initial sabre upgrade (needs lots of work - to wit: authentication, redo the browser interface, and rework event export/import)

67 files changed, 12220 insertions, 0 deletions

diff --git a/vendor/sabre/dav/lib/CalDAV/Backend/AbstractBackend.php b/vendor/sabre/dav/lib/CalDAV/Backend/AbstractBackend.php
new file mode 100644
index 000000000..d58b4a46e
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Backend/AbstractBackend.php
@@ -0,0 +1,226 @@
+<?php
+
+namespace Sabre\CalDAV\Backend;
+
+use Sabre\VObject;
+use Sabre\CalDAV;
+
+/**
+ * Abstract Calendaring backend. Extend this class to create your own backends.
+ *
+ * Checkout the BackendInterface for all the methods that must be implemented.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+abstract class AbstractBackend implements BackendInterface {
+
+    /**
+     * Updates properties for a calendar.
+     *
+     * The list of mutations is stored in a Sabre\DAV\PropPatch object.
+     * To do the actual updates, you must tell this object which properties
+     * you're going to process with the handle() method.
+     *
+     * Calling the handle method is like telling the PropPatch object "I
+     * promise I can handle updating this property".
+     *
+     * Read the PropPatch documenation for more info and examples.
+     *
+     * @param string $path
+     * @param \Sabre\DAV\PropPatch $propPatch
+     * @return void
+     */
+    function updateCalendar($calendarId, \Sabre\DAV\PropPatch $propPatch) {
+
+    }
+
+    /**
+     * Returns a list of calendar objects.
+     *
+     * This method should work identical to getCalendarObject, but instead
+     * return all the calendar objects in the list as an array.
+     *
+     * If the backend supports this, it may allow for some speed-ups.
+     *
+     * @param mixed $calendarId
+     * @param array $uris
+     * @return array
+     */
+    function getMultipleCalendarObjects($calendarId, array $uris) {
+
+        return array_map(function($uri) use ($calendarId) {
+            return $this->getCalendarObject($calendarId, $uri);
+        }, $uris);
+
+    }
+
+    /**
+     * Performs a calendar-query on the contents of this calendar.
+     *
+     * The calendar-query is defined in RFC4791 : CalDAV. Using the
+     * calendar-query it is possible for a client to request a specific set of
+     * object, based on contents of iCalendar properties, date-ranges and
+     * iCalendar component types (VTODO, VEVENT).
+     *
+     * This method should just return a list of (relative) urls that match this
+     * query.
+     *
+     * The list of filters are specified as an array. The exact array is
+     * documented by \Sabre\CalDAV\CalendarQueryParser.
+     *
+     * Note that it is extremely likely that getCalendarObject for every path
+     * returned from this method will be called almost immediately after. You
+     * may want to anticipate this to speed up these requests.
+     *
+     * This method provides a default implementation, which parses *all* the
+     * iCalendar objects in the specified calendar.
+     *
+     * This default may well be good enough for personal use, and calendars
+     * that aren't very large. But if you anticipate high usage, big calendars
+     * or high loads, you are strongly adviced to optimize certain paths.
+     *
+     * The best way to do so is override this method and to optimize
+     * specifically for 'common filters'.
+     *
+     * Requests that are extremely common are:
+     *   * requests for just VEVENTS
+     *   * requests for just VTODO
+     *   * requests with a time-range-filter on either VEVENT or VTODO.
+     *
+     * ..and combinations of these requests. It may not be worth it to try to
+     * handle every possible situation and just rely on the (relatively
+     * easy to use) CalendarQueryValidator to handle the rest.
+     *
+     * Note that especially time-range-filters may be difficult to parse. A
+     * time-range filter specified on a VEVENT must for instance also handle
+     * recurrence rules correctly.
+     * A good example of how to interprete all these filters can also simply
+     * be found in \Sabre\CalDAV\CalendarQueryFilter. This class is as correct
+     * as possible, so it gives you a good idea on what type of stuff you need
+     * to think of.
+     *
+     * @param mixed $calendarId
+     * @param array $filters
+     * @return array
+     */
+    function calendarQuery($calendarId, array $filters) {
+
+        $result = [];
+        $objects = $this->getCalendarObjects($calendarId);
+
+        foreach ($objects as $object) {
+
+            if ($this->validateFilterForObject($object, $filters)) {
+                $result[] = $object['uri'];
+            }
+
+        }
+
+        return $result;
+
+    }
+
+    /**
+     * This method validates if a filter (as passed to calendarQuery) matches
+     * the given object.
+     *
+     * @param array $object
+     * @param array $filters
+     * @return bool
+     */
+    protected function validateFilterForObject(array $object, array $filters) {
+
+        // Unfortunately, setting the 'calendardata' here is optional. If
+        // it was excluded, we actually need another call to get this as
+        // well.
+        if (!isset($object['calendardata'])) {
+            $object = $this->getCalendarObject($object['calendarid'], $object['uri']);
+        }
+
+        $vObject = VObject\Reader::read($object['calendardata']);
+
+        $validator = new CalDAV\CalendarQueryValidator();
+        $result = $validator->validate($vObject, $filters);
+
+        // Destroy circular references so PHP will GC the object.
+        $vObject->destroy();
+
+        return $result;
+
+    }
+
+    /**
+     * Searches through all of a users calendars and calendar objects to find
+     * an object with a specific UID.
+     *
+     * This method should return the path to this object, relative to the
+     * calendar home, so this path usually only contains two parts:
+     *
+     * calendarpath/objectpath.ics
+     *
+     * If the uid is not found, return null.
+     *
+     * This method should only consider * objects that the principal owns, so
+     * any calendars owned by other principals that also appear in this
+     * collection should be ignored.
+     *
+     * @param string $principalUri
+     * @param string $uid
+     * @return string|null
+     */
+    function getCalendarObjectByUID($principalUri, $uid) {
+
+        // Note: this is a super slow naive implementation of this method. You
+        // are highly recommended to optimize it, if your backend allows it.
+        foreach ($this->getCalendarsForUser($principalUri) as $calendar) {
+
+            // We must ignore calendars owned by other principals.
+            if ($calendar['principaluri'] !== $principalUri) {
+                continue;
+            }
+
+            // Ignore calendars that are shared.
+            if (isset($calendar['{http://sabredav.org/ns}owner-principal']) && $calendar['{http://sabredav.org/ns}owner-principal'] !== $principalUri) {
+                continue;
+            }
+
+            $results = $this->calendarQuery(
+                $calendar['id'],
+                [
+                    'name'         => 'VCALENDAR',
+                    'prop-filters' => [],
+                    'comp-filters' => [
+                        [
+                            'name'           => 'VEVENT',
+                            'is-not-defined' => false,
+                            'time-range'     => null,
+                            'comp-filters'   => [],
+                            'prop-filters'   => [
+                                [
+                                    'name'           => 'UID',
+                                    'is-not-defined' => false,
+                                    'time-range'     => null,
+                                    'text-match'     => [
+                                        'value'            => $uid,
+                                        'negate-condition' => false,
+                                        'collation'        => 'i;octet',
+                                    ],
+                                    'param-filters' => [],
+                                ],
+                            ]
+                        ]
+                    ],
+                ]
+            );
+            if ($results) {
+                // We have a match
+                return $calendar['uri'] . '/' . $results[0];
+            }
+
+        }
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Backend/BackendInterface.php b/vendor/sabre/dav/lib/CalDAV/Backend/BackendInterface.php
new file mode 100644
index 000000000..7513fb60d
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Backend/BackendInterface.php
@@ -0,0 +1,268 @@
+<?php
+
+namespace Sabre\CalDAV\Backend;
+
+/**
+ * Every CalDAV backend must at least implement this interface.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface BackendInterface {
+
+    /**
+     * Returns a list of calendars for a principal.
+     *
+     * Every project is an array with the following keys:
+     *  * id, a unique id that will be used by other functions to modify the
+     *    calendar. This can be the same as the uri or a database key.
+     *  * uri, which is the basename of the uri with which the calendar is
+     *    accessed.
+     *  * principaluri. The owner of the calendar. Almost always the same as
+     *    principalUri passed to this method.
+     *
+     * Furthermore it can contain webdav properties in clark notation. A very
+     * common one is '{DAV:}displayname'.
+     *
+     * Many clients also require:
+     * {urn:ietf:params:xml:ns:caldav}supported-calendar-component-set
+     * For this property, you can just return an instance of
+     * Sabre\CalDAV\Property\SupportedCalendarComponentSet.
+     *
+     * If you return {http://sabredav.org/ns}read-only and set the value to 1,
+     * ACL will automatically be put in read-only mode.
+     *
+     * @param string $principalUri
+     * @return array
+     */
+    function getCalendarsForUser($principalUri);
+
+    /**
+     * Creates a new calendar for a principal.
+     *
+     * If the creation was a success, an id must be returned that can be used to
+     * reference this calendar in other methods, such as updateCalendar.
+     *
+     * @param string $principalUri
+     * @param string $calendarUri
+     * @param array $properties
+     * @return void
+     */
+    function createCalendar($principalUri, $calendarUri, array $properties);
+
+    /**
+     * Updates properties for a calendar.
+     *
+     * The list of mutations is stored in a Sabre\DAV\PropPatch object.
+     * To do the actual updates, you must tell this object which properties
+     * you're going to process with the handle() method.
+     *
+     * Calling the handle method is like telling the PropPatch object "I
+     * promise I can handle updating this property".
+     *
+     * Read the PropPatch documentation for more info and examples.
+     *
+     * @param string $path
+     * @param \Sabre\DAV\PropPatch $propPatch
+     * @return void
+     */
+    function updateCalendar($calendarId, \Sabre\DAV\PropPatch $propPatch);
+
+    /**
+     * Delete a calendar and all its objects
+     *
+     * @param mixed $calendarId
+     * @return void
+     */
+    function deleteCalendar($calendarId);
+
+    /**
+     * Returns all calendar objects within a calendar.
+     *
+     * Every item contains an array with the following keys:
+     *   * calendardata - The iCalendar-compatible calendar data
+     *   * uri - a unique key which will be used to construct the uri. This can
+     *     be any arbitrary string, but making sure it ends with '.ics' is a
+     *     good idea. This is only the basename, or filename, not the full
+     *     path.
+     *   * lastmodified - a timestamp of the last modification time
+     *   * etag - An arbitrary string, surrounded by double-quotes. (e.g.:
+     *   '"abcdef"')
+     *   * size - The size of the calendar objects, in bytes.
+     *   * component - optional, a string containing the type of object, such
+     *     as 'vevent' or 'vtodo'. If specified, this will be used to populate
+     *     the Content-Type header.
+     *
+     * Note that the etag is optional, but it's highly encouraged to return for
+     * speed reasons.
+     *
+     * The calendardata is also optional. If it's not returned
+     * 'getCalendarObject' will be called later, which *is* expected to return
+     * calendardata.
+     *
+     * If neither etag or size are specified, the calendardata will be
+     * used/fetched to determine these numbers. If both are specified the
+     * amount of times this is needed is reduced by a great degree.
+     *
+     * @param mixed $calendarId
+     * @return array
+     */
+    function getCalendarObjects($calendarId);
+
+    /**
+     * Returns information from a single calendar object, based on it's object
+     * uri.
+     *
+     * The object uri is only the basename, or filename and not a full path.
+     *
+     * The returned array must have the same keys as getCalendarObjects. The
+     * 'calendardata' object is required here though, while it's not required
+     * for getCalendarObjects.
+     *
+     * This method must return null if the object did not exist.
+     *
+     * @param mixed $calendarId
+     * @param string $objectUri
+     * @return array|null
+     */
+    function getCalendarObject($calendarId, $objectUri);
+
+    /**
+     * Returns a list of calendar objects.
+     *
+     * This method should work identical to getCalendarObject, but instead
+     * return all the calendar objects in the list as an array.
+     *
+     * If the backend supports this, it may allow for some speed-ups.
+     *
+     * @param mixed $calendarId
+     * @param array $uris
+     * @return array
+     */
+    function getMultipleCalendarObjects($calendarId, array $uris);
+
+    /**
+     * Creates a new calendar object.
+     *
+     * The object uri is only the basename, or filename and not a full path.
+     *
+     * It is possible to return an etag from this function, which will be used
+     * in the response to this PUT request. Note that the ETag must be
+     * surrounded by double-quotes.
+     *
+     * However, you should only really return this ETag if you don't mangle the
+     * calendar-data. If the result of a subsequent GET to this object is not
+     * the exact same as this request body, you should omit the ETag.
+     *
+     * @param mixed $calendarId
+     * @param string $objectUri
+     * @param string $calendarData
+     * @return string|null
+     */
+    function createCalendarObject($calendarId, $objectUri, $calendarData);
+
+    /**
+     * Updates an existing calendarobject, based on it's uri.
+     *
+     * The object uri is only the basename, or filename and not a full path.
+     *
+     * It is possible return an etag from this function, which will be used in
+     * the response to this PUT request. Note that the ETag must be surrounded
+     * by double-quotes.
+     *
+     * However, you should only really return this ETag if you don't mangle the
+     * calendar-data. If the result of a subsequent GET to this object is not
+     * the exact same as this request body, you should omit the ETag.
+     *
+     * @param mixed $calendarId
+     * @param string $objectUri
+     * @param string $calendarData
+     * @return string|null
+     */
+    function updateCalendarObject($calendarId, $objectUri, $calendarData);
+
+    /**
+     * Deletes an existing calendar object.
+     *
+     * The object uri is only the basename, or filename and not a full path.
+     *
+     * @param mixed $calendarId
+     * @param string $objectUri
+     * @return void
+     */
+    function deleteCalendarObject($calendarId, $objectUri);
+
+    /**
+     * Performs a calendar-query on the contents of this calendar.
+     *
+     * The calendar-query is defined in RFC4791 : CalDAV. Using the
+     * calendar-query it is possible for a client to request a specific set of
+     * object, based on contents of iCalendar properties, date-ranges and
+     * iCalendar component types (VTODO, VEVENT).
+     *
+     * This method should just return a list of (relative) urls that match this
+     * query.
+     *
+     * The list of filters are specified as an array. The exact array is
+     * documented by Sabre\CalDAV\CalendarQueryParser.
+     *
+     * Note that it is extremely likely that getCalendarObject for every path
+     * returned from this method will be called almost immediately after. You
+     * may want to anticipate this to speed up these requests.
+     *
+     * This method provides a default implementation, which parses *all* the
+     * iCalendar objects in the specified calendar.
+     *
+     * This default may well be good enough for personal use, and calendars
+     * that aren't very large. But if you anticipate high usage, big calendars
+     * or high loads, you are strongly adviced to optimize certain paths.
+     *
+     * The best way to do so is override this method and to optimize
+     * specifically for 'common filters'.
+     *
+     * Requests that are extremely common are:
+     *   * requests for just VEVENTS
+     *   * requests for just VTODO
+     *   * requests with a time-range-filter on either VEVENT or VTODO.
+     *
+     * ..and combinations of these requests. It may not be worth it to try to
+     * handle every possible situation and just rely on the (relatively
+     * easy to use) CalendarQueryValidator to handle the rest.
+     *
+     * Note that especially time-range-filters may be difficult to parse. A
+     * time-range filter specified on a VEVENT must for instance also handle
+     * recurrence rules correctly.
+     * A good example of how to interprete all these filters can also simply
+     * be found in Sabre\CalDAV\CalendarQueryFilter. This class is as correct
+     * as possible, so it gives you a good idea on what type of stuff you need
+     * to think of.
+     *
+     * @param mixed $calendarId
+     * @param array $filters
+     * @return array
+     */
+    function calendarQuery($calendarId, array $filters);
+
+    /**
+     * Searches through all of a users calendars and calendar objects to find
+     * an object with a specific UID.
+     *
+     * This method should return the path to this object, relative to the
+     * calendar home, so this path usually only contains two parts:
+     *
+     * calendarpath/objectpath.ics
+     *
+     * If the uid is not found, return null.
+     *
+     * This method should only consider * objects that the principal owns, so
+     * any calendars owned by other principals that also appear in this
+     * collection should be ignored.
+     *
+     * @param string $principalUri
+     * @param string $uid
+     * @return string|null
+     */
+    function getCalendarObjectByUID($principalUri, $uid);
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Backend/NotificationSupport.php b/vendor/sabre/dav/lib/CalDAV/Backend/NotificationSupport.php
new file mode 100644
index 000000000..19b9b22a7
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Backend/NotificationSupport.php
@@ -0,0 +1,46 @@
+<?php
+
+namespace Sabre\CalDAV\Backend;
+
+use Sabre\CalDAV\Xml\Notification\NotificationInterface;
+
+/**
+ * Adds caldav notification support to a backend.
+ *
+ * Note: This feature is experimental, and may change in between different
+ * SabreDAV versions.
+ *
+ * Notifications are defined at:
+ * http://svn.calendarserver.org/repository/calendarserver/CalendarServer/trunk/doc/Extensions/caldav-notifications.txt
+ *
+ * These notifications are basically a list of server-generated notifications
+ * displayed to the user. Users can dismiss notifications by deleting them.
+ *
+ * The primary usecase is to allow for calendar-sharing.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface NotificationSupport extends BackendInterface {
+
+    /**
+     * Returns a list of notifications for a given principal url.
+     *
+     * @param string $principalUri
+     * @return NotificationInterface[]
+     */
+    function getNotificationsForPrincipal($principalUri);
+
+    /**
+     * This deletes a specific notifcation.
+     *
+     * This may be called by a client once it deems a notification handled.
+     *
+     * @param string $principalUri
+     * @param NotificationInterface $notification
+     * @return void
+     */
+    function deleteNotification($principalUri, NotificationInterface $notification);
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Backend/PDO.php b/vendor/sabre/dav/lib/CalDAV/Backend/PDO.php
new file mode 100644
index 000000000..76b69dc6e
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Backend/PDO.php
@@ -0,0 +1,1210 @@
+<?php
+
+namespace Sabre\CalDAV\Backend;
+
+use Sabre\VObject;
+use Sabre\CalDAV;
+use Sabre\DAV;
+use Sabre\DAV\Exception\Forbidden;
+
+/**
+ * PDO CalDAV backend
+ *
+ * This backend is used to store calendar-data in a PDO database, such as
+ * sqlite or MySQL
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class PDO extends AbstractBackend implements SyncSupport, SubscriptionSupport, SchedulingSupport {
+
+    /**
+     * We need to specify a max date, because we need to stop *somewhere*
+     *
+     * On 32 bit system the maximum for a signed integer is 2147483647, so
+     * MAX_DATE cannot be higher than date('Y-m-d', 2147483647) which results
+     * in 2038-01-19 to avoid problems when the date is converted
+     * to a unix timestamp.
+     */
+    const MAX_DATE = '2038-01-01';
+
+    /**
+     * pdo
+     *
+     * @var \PDO
+     */
+    protected $pdo;
+
+    /**
+     * The table name that will be used for calendars
+     *
+     * @var string
+     */
+    public $calendarTableName = 'calendars';
+
+    /**
+     * The table name that will be used for calendar objects
+     *
+     * @var string
+     */
+    public $calendarObjectTableName = 'calendarobjects';
+
+    /**
+     * The table name that will be used for tracking changes in calendars.
+     *
+     * @var string
+     */
+    public $calendarChangesTableName = 'calendarchanges';
+
+    /**
+     * The table name that will be used inbox items.
+     *
+     * @var string
+     */
+    public $schedulingObjectTableName = 'schedulingobjects';
+
+    /**
+     * The table name that will be used for calendar subscriptions.
+     *
+     * @var string
+     */
+    public $calendarSubscriptionsTableName = 'calendarsubscriptions';
+
+    /**
+     * List of CalDAV properties, and how they map to database fieldnames
+     * Add your own properties by simply adding on to this array.
+     *
+     * Note that only string-based properties are supported here.
+     *
+     * @var array
+     */
+    public $propertyMap = [
+        '{DAV:}displayname'                                   => 'displayname',
+        '{urn:ietf:params:xml:ns:caldav}calendar-description' => 'description',
+        '{urn:ietf:params:xml:ns:caldav}calendar-timezone'    => 'timezone',
+        '{http://apple.com/ns/ical/}calendar-order'           => 'calendarorder',
+        '{http://apple.com/ns/ical/}calendar-color'           => 'calendarcolor',
+    ];
+
+    /**
+     * List of subscription properties, and how they map to database fieldnames.
+     *
+     * @var array
+     */
+    public $subscriptionPropertyMap = [
+        '{DAV:}displayname'                                           => 'displayname',
+        '{http://apple.com/ns/ical/}refreshrate'                      => 'refreshrate',
+        '{http://apple.com/ns/ical/}calendar-order'                   => 'calendarorder',
+        '{http://apple.com/ns/ical/}calendar-color'                   => 'calendarcolor',
+        '{http://calendarserver.org/ns/}subscribed-strip-todos'       => 'striptodos',
+        '{http://calendarserver.org/ns/}subscribed-strip-alarms'      => 'stripalarms',
+        '{http://calendarserver.org/ns/}subscribed-strip-attachments' => 'stripattachments',
+    ];
+
+    /**
+     * Creates the backend
+     *
+     * @param \PDO $pdo
+     */
+    function __construct(\PDO $pdo) {
+
+        $this->pdo = $pdo;
+
+    }
+
+    /**
+     * Returns a list of calendars for a principal.
+     *
+     * Every project is an array with the following keys:
+     *  * id, a unique id that will be used by other functions to modify the
+     *    calendar. This can be the same as the uri or a database key.
+     *  * uri. This is just the 'base uri' or 'filename' of the calendar.
+     *  * principaluri. The owner of the calendar. Almost always the same as
+     *    principalUri passed to this method.
+     *
+     * Furthermore it can contain webdav properties in clark notation. A very
+     * common one is '{DAV:}displayname'.
+     *
+     * Many clients also require:
+     * {urn:ietf:params:xml:ns:caldav}supported-calendar-component-set
+     * For this property, you can just return an instance of
+     * Sabre\CalDAV\Xml\Property\SupportedCalendarComponentSet.
+     *
+     * If you return {http://sabredav.org/ns}read-only and set the value to 1,
+     * ACL will automatically be put in read-only mode.
+     *
+     * @param string $principalUri
+     * @return array
+     */
+    function getCalendarsForUser($principalUri) {
+
+        $fields = array_values($this->propertyMap);
+        $fields[] = 'id';
+        $fields[] = 'uri';
+        $fields[] = 'synctoken';
+        $fields[] = 'components';
+        $fields[] = 'principaluri';
+        $fields[] = 'transparent';
+
+        // Making fields a comma-delimited list
+        $fields = implode(', ', $fields);
+        $stmt = $this->pdo->prepare("SELECT " . $fields . " FROM " . $this->calendarTableName . " WHERE principaluri = ? ORDER BY calendarorder ASC");
+        $stmt->execute([$principalUri]);
+
+        $calendars = [];
+        while ($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
+
+            $components = [];
+            if ($row['components']) {
+                $components = explode(',', $row['components']);
+            }
+
+            $calendar = [
+                'id'                                                                 => $row['id'],
+                'uri'                                                                => $row['uri'],
+                'principaluri'                                                       => $row['principaluri'],
+                '{' . CalDAV\Plugin::NS_CALENDARSERVER . '}getctag'                  => 'http://sabre.io/ns/sync/' . ($row['synctoken'] ? $row['synctoken'] : '0'),
+                '{http://sabredav.org/ns}sync-token'                                 => $row['synctoken'] ? $row['synctoken'] : '0',
+                '{' . CalDAV\Plugin::NS_CALDAV . '}supported-calendar-component-set' => new CalDAV\Xml\Property\SupportedCalendarComponentSet($components),
+                '{' . CalDAV\Plugin::NS_CALDAV . '}schedule-calendar-transp'         => new CalDAV\Xml\Property\ScheduleCalendarTransp($row['transparent'] ? 'transparent' : 'opaque'),
+            ];
+
+
+            foreach ($this->propertyMap as $xmlName => $dbName) {
+                $calendar[$xmlName] = $row[$dbName];
+            }
+
+            $calendars[] = $calendar;
+
+        }
+
+        return $calendars;
+
+    }
+
+    /**
+     * Creates a new calendar for a principal.
+     *
+     * If the creation was a success, an id must be returned that can be used
+     * to reference this calendar in other methods, such as updateCalendar.
+     *
+     * @param string $principalUri
+     * @param string $calendarUri
+     * @param array $properties
+     * @return string
+     */
+    function createCalendar($principalUri, $calendarUri, array $properties) {
+
+        $fieldNames = [
+            'principaluri',
+            'uri',
+            'synctoken',
+            'transparent',
+        ];
+        $values = [
+            ':principaluri' => $principalUri,
+            ':uri'          => $calendarUri,
+            ':synctoken'    => 1,
+            ':transparent'  => 0,
+        ];
+
+        // Default value
+        $sccs = '{urn:ietf:params:xml:ns:caldav}supported-calendar-component-set';
+        $fieldNames[] = 'components';
+        if (!isset($properties[$sccs])) {
+            $values[':components'] = 'VEVENT,VTODO';
+        } else {
+            if (!($properties[$sccs] instanceof CalDAV\Xml\Property\SupportedCalendarComponentSet)) {
+                throw new DAV\Exception('The ' . $sccs . ' property must be of type: \Sabre\CalDAV\Xml\Property\SupportedCalendarComponentSet');
+            }
+            $values[':components'] = implode(',', $properties[$sccs]->getValue());
+        }
+        $transp = '{' . CalDAV\Plugin::NS_CALDAV . '}schedule-calendar-transp';
+        if (isset($properties[$transp])) {
+            $values[':transparent'] = $properties[$transp]->getValue() === 'transparent';
+        }
+
+        foreach ($this->propertyMap as $xmlName => $dbName) {
+            if (isset($properties[$xmlName])) {
+
+                $values[':' . $dbName] = $properties[$xmlName];
+                $fieldNames[] = $dbName;
+            }
+        }
+
+        $stmt = $this->pdo->prepare("INSERT INTO " . $this->calendarTableName . " (" . implode(', ', $fieldNames) . ") VALUES (" . implode(', ', array_keys($values)) . ")");
+        $stmt->execute($values);
+
+        return $this->pdo->lastInsertId();
+
+    }
+
+    /**
+     * Updates properties for a calendar.
+     *
+     * The list of mutations is stored in a Sabre\DAV\PropPatch object.
+     * To do the actual updates, you must tell this object which properties
+     * you're going to process with the handle() method.
+     *
+     * Calling the handle method is like telling the PropPatch object "I
+     * promise I can handle updating this property".
+     *
+     * Read the PropPatch documenation for more info and examples.
+     *
+     * @param string $calendarId
+     * @param \Sabre\DAV\PropPatch $propPatch
+     * @return void
+     */
+    function updateCalendar($calendarId, \Sabre\DAV\PropPatch $propPatch) {
+
+        $supportedProperties = array_keys($this->propertyMap);
+        $supportedProperties[] = '{' . CalDAV\Plugin::NS_CALDAV . '}schedule-calendar-transp';
+
+        $propPatch->handle($supportedProperties, function($mutations) use ($calendarId) {
+            $newValues = [];
+            foreach ($mutations as $propertyName => $propertyValue) {
+
+                switch ($propertyName) {
+                    case '{' . CalDAV\Plugin::NS_CALDAV . '}schedule-calendar-transp' :
+                        $fieldName = 'transparent';
+                        $newValues[$fieldName] = $propertyValue->getValue() === 'transparent';
+                        break;
+                    default :
+                        $fieldName = $this->propertyMap[$propertyName];
+                        $newValues[$fieldName] = $propertyValue;
+                        break;
+                }
+
+            }
+            $valuesSql = [];
+            foreach ($newValues as $fieldName => $value) {
+                $valuesSql[] = $fieldName . ' = ?';
+            }
+
+            $stmt = $this->pdo->prepare("UPDATE " . $this->calendarTableName . " SET " . implode(', ', $valuesSql) . " WHERE id = ?");
+            $newValues['id'] = $calendarId;
+            $stmt->execute(array_values($newValues));
+
+            $this->addChange($calendarId, "", 2);
+
+            return true;
+
+        });
+
+    }
+
+    /**
+     * Delete a calendar and all it's objects
+     *
+     * @param string $calendarId
+     * @return void
+     */
+    function deleteCalendar($calendarId) {
+
+        $stmt = $this->pdo->prepare('DELETE FROM ' . $this->calendarObjectTableName . ' WHERE calendarid = ?');
+        $stmt->execute([$calendarId]);
+
+        $stmt = $this->pdo->prepare('DELETE FROM ' . $this->calendarTableName . ' WHERE id = ?');
+        $stmt->execute([$calendarId]);
+
+        $stmt = $this->pdo->prepare('DELETE FROM ' . $this->calendarChangesTableName . ' WHERE calendarid = ?');
+        $stmt->execute([$calendarId]);
+
+    }
+
+    /**
+     * Returns all calendar objects within a calendar.
+     *
+     * Every item contains an array with the following keys:
+     *   * calendardata - The iCalendar-compatible calendar data
+     *   * uri - a unique key which will be used to construct the uri. This can
+     *     be any arbitrary string, but making sure it ends with '.ics' is a
+     *     good idea. This is only the basename, or filename, not the full
+     *     path.
+     *   * lastmodified - a timestamp of the last modification time
+     *   * etag - An arbitrary string, surrounded by double-quotes. (e.g.:
+     *   '  "abcdef"')
+     *   * size - The size of the calendar objects, in bytes.
+     *   * component - optional, a string containing the type of object, such
+     *     as 'vevent' or 'vtodo'. If specified, this will be used to populate
+     *     the Content-Type header.
+     *
+     * Note that the etag is optional, but it's highly encouraged to return for
+     * speed reasons.
+     *
+     * The calendardata is also optional. If it's not returned
+     * 'getCalendarObject' will be called later, which *is* expected to return
+     * calendardata.
+     *
+     * If neither etag or size are specified, the calendardata will be
+     * used/fetched to determine these numbers. If both are specified the
+     * amount of times this is needed is reduced by a great degree.
+     *
+     * @param string $calendarId
+     * @return array
+     */
+    function getCalendarObjects($calendarId) {
+
+        $stmt = $this->pdo->prepare('SELECT id, uri, lastmodified, etag, calendarid, size, componenttype FROM ' . $this->calendarObjectTableName . ' WHERE calendarid = ?');
+        $stmt->execute([$calendarId]);
+
+        $result = [];
+        foreach ($stmt->fetchAll(\PDO::FETCH_ASSOC) as $row) {
+            $result[] = [
+                'id'           => $row['id'],
+                'uri'          => $row['uri'],
+                'lastmodified' => $row['lastmodified'],
+                'etag'         => '"' . $row['etag'] . '"',
+                'calendarid'   => $row['calendarid'],
+                'size'         => (int)$row['size'],
+                'component'    => strtolower($row['componenttype']),
+            ];
+        }
+
+        return $result;
+
+    }
+
+    /**
+     * Returns information from a single calendar object, based on it's object
+     * uri.
+     *
+     * The object uri is only the basename, or filename and not a full path.
+     *
+     * The returned array must have the same keys as getCalendarObjects. The
+     * 'calendardata' object is required here though, while it's not required
+     * for getCalendarObjects.
+     *
+     * This method must return null if the object did not exist.
+     *
+     * @param string $calendarId
+     * @param string $objectUri
+     * @return array|null
+     */
+    function getCalendarObject($calendarId, $objectUri) {
+
+        $stmt = $this->pdo->prepare('SELECT id, uri, lastmodified, etag, calendarid, size, calendardata, componenttype FROM ' . $this->calendarObjectTableName . ' WHERE calendarid = ? AND uri = ?');
+        $stmt->execute([$calendarId, $objectUri]);
+        $row = $stmt->fetch(\PDO::FETCH_ASSOC);
+
+        if (!$row) return null;
+
+        return [
+            'id'            => $row['id'],
+            'uri'           => $row['uri'],
+            'lastmodified'  => $row['lastmodified'],
+            'etag'          => '"' . $row['etag'] . '"',
+            'calendarid'    => $row['calendarid'],
+            'size'          => (int)$row['size'],
+            'calendardata'  => $row['calendardata'],
+            'component'     => strtolower($row['componenttype']),
+         ];
+
+    }
+
+    /**
+     * Returns a list of calendar objects.
+     *
+     * This method should work identical to getCalendarObject, but instead
+     * return all the calendar objects in the list as an array.
+     *
+     * If the backend supports this, it may allow for some speed-ups.
+     *
+     * @param mixed $calendarId
+     * @param array $uris
+     * @return array
+     */
+    function getMultipleCalendarObjects($calendarId, array $uris) {
+
+        $query = 'SELECT id, uri, lastmodified, etag, calendarid, size, calendardata, componenttype FROM ' . $this->calendarObjectTableName . ' WHERE calendarid = ? AND uri IN (';
+        // Inserting a whole bunch of question marks
+        $query .= implode(',', array_fill(0, count($uris), '?'));
+        $query .= ')';
+
+        $stmt = $this->pdo->prepare($query);
+        $stmt->execute(array_merge([$calendarId], $uris));
+
+        $result = [];
+        while ($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
+
+            $result[] = [
+                'id'           => $row['id'],
+                'uri'          => $row['uri'],
+                'lastmodified' => $row['lastmodified'],
+                'etag'         => '"' . $row['etag'] . '"',
+                'calendarid'   => $row['calendarid'],
+                'size'         => (int)$row['size'],
+                'calendardata' => $row['calendardata'],
+                'component'    => strtolower($row['componenttype']),
+            ];
+
+        }
+        return $result;
+
+    }
+
+
+    /**
+     * Creates a new calendar object.
+     *
+     * The object uri is only the basename, or filename and not a full path.
+     *
+     * It is possible return an etag from this function, which will be used in
+     * the response to this PUT request. Note that the ETag must be surrounded
+     * by double-quotes.
+     *
+     * However, you should only really return this ETag if you don't mangle the
+     * calendar-data. If the result of a subsequent GET to this object is not
+     * the exact same as this request body, you should omit the ETag.
+     *
+     * @param mixed $calendarId
+     * @param string $objectUri
+     * @param string $calendarData
+     * @return string|null
+     */
+    function createCalendarObject($calendarId, $objectUri, $calendarData) {
+
+        $extraData = $this->getDenormalizedData($calendarData);
+
+        $stmt = $this->pdo->prepare('INSERT INTO ' . $this->calendarObjectTableName . ' (calendarid, uri, calendardata, lastmodified, etag, size, componenttype, firstoccurence, lastoccurence, uid) VALUES (?,?,?,?,?,?,?,?,?,?)');
+        $stmt->execute([
+            $calendarId,
+            $objectUri,
+            $calendarData,
+            time(),
+            $extraData['etag'],
+            $extraData['size'],
+            $extraData['componentType'],
+            $extraData['firstOccurence'],
+            $extraData['lastOccurence'],
+            $extraData['uid'],
+        ]);
+        $this->addChange($calendarId, $objectUri, 1);
+
+        return '"' . $extraData['etag'] . '"';
+
+    }
+
+    /**
+     * Updates an existing calendarobject, based on it's uri.
+     *
+     * The object uri is only the basename, or filename and not a full path.
+     *
+     * It is possible return an etag from this function, which will be used in
+     * the response to this PUT request. Note that the ETag must be surrounded
+     * by double-quotes.
+     *
+     * However, you should only really return this ETag if you don't mangle the
+     * calendar-data. If the result of a subsequent GET to this object is not
+     * the exact same as this request body, you should omit the ETag.
+     *
+     * @param mixed $calendarId
+     * @param string $objectUri
+     * @param string $calendarData
+     * @return string|null
+     */
+    function updateCalendarObject($calendarId, $objectUri, $calendarData) {
+
+        $extraData = $this->getDenormalizedData($calendarData);
+
+        $stmt = $this->pdo->prepare('UPDATE ' . $this->calendarObjectTableName . ' SET calendardata = ?, lastmodified = ?, etag = ?, size = ?, componenttype = ?, firstoccurence = ?, lastoccurence = ?, uid = ? WHERE calendarid = ? AND uri = ?');
+        $stmt->execute([$calendarData, time(), $extraData['etag'], $extraData['size'], $extraData['componentType'], $extraData['firstOccurence'], $extraData['lastOccurence'], $extraData['uid'], $calendarId, $objectUri]);
+
+        $this->addChange($calendarId, $objectUri, 2);
+
+        return '"' . $extraData['etag'] . '"';
+
+    }
+
+    /**
+     * Parses some information from calendar objects, used for optimized
+     * calendar-queries.
+     *
+     * Returns an array with the following keys:
+     *   * etag - An md5 checksum of the object without the quotes.
+     *   * size - Size of the object in bytes
+     *   * componentType - VEVENT, VTODO or VJOURNAL
+     *   * firstOccurence
+     *   * lastOccurence
+     *   * uid - value of the UID property
+     *
+     * @param string $calendarData
+     * @return array
+     */
+    protected function getDenormalizedData($calendarData) {
+
+        $vObject = VObject\Reader::read($calendarData);
+        $componentType = null;
+        $component = null;
+        $firstOccurence = null;
+        $lastOccurence = null;
+        $uid = null;
+        foreach ($vObject->getComponents() as $component) {
+            if ($component->name !== 'VTIMEZONE') {
+                $componentType = $component->name;
+                $uid = (string)$component->UID;
+                break;
+            }
+        }
+        if (!$componentType) {
+            throw new \Sabre\DAV\Exception\BadRequest('Calendar objects must have a VJOURNAL, VEVENT or VTODO component');
+        }
+        if ($componentType === 'VEVENT') {
+            $firstOccurence = $component->DTSTART->getDateTime()->getTimeStamp();
+            // Finding the last occurence is a bit harder
+            if (!isset($component->RRULE)) {
+                if (isset($component->DTEND)) {
+                    $lastOccurence = $component->DTEND->getDateTime()->getTimeStamp();
+                } elseif (isset($component->DURATION)) {
+                    $endDate = clone $component->DTSTART->getDateTime();
+                    $endDate = $endDate->add(VObject\DateTimeParser::parse($component->DURATION->getValue()));
+                    $lastOccurence = $endDate->getTimeStamp();
+                } elseif (!$component->DTSTART->hasTime()) {
+                    $endDate = clone $component->DTSTART->getDateTime();
+                    $endDate = $endDate->modify('+1 day');
+                    $lastOccurence = $endDate->getTimeStamp();
+                } else {
+                    $lastOccurence = $firstOccurence;
+                }
+            } else {
+                $it = new VObject\Recur\EventIterator($vObject, (string)$component->UID);
+                $maxDate = new \DateTime(self::MAX_DATE);
+                if ($it->isInfinite()) {
+                    $lastOccurence = $maxDate->getTimeStamp();
+                } else {
+                    $end = $it->getDtEnd();
+                    while ($it->valid() && $end < $maxDate) {
+                        $end = $it->getDtEnd();
+                        $it->next();
+
+                    }
+                    $lastOccurence = $end->getTimeStamp();
+                }
+
+            }
+        }
+
+        // Destroy circular references to PHP will GC the object.
+        $vObject->destroy();
+
+        return [
+            'etag'           => md5($calendarData),
+            'size'           => strlen($calendarData),
+            'componentType'  => $componentType,
+            'firstOccurence' => $firstOccurence,
+            'lastOccurence'  => $lastOccurence,
+            'uid'            => $uid,
+        ];
+
+    }
+
+    /**
+     * Deletes an existing calendar object.
+     *
+     * The object uri is only the basename, or filename and not a full path.
+     *
+     * @param string $calendarId
+     * @param string $objectUri
+     * @return void
+     */
+    function deleteCalendarObject($calendarId, $objectUri) {
+
+        $stmt = $this->pdo->prepare('DELETE FROM ' . $this->calendarObjectTableName . ' WHERE calendarid = ? AND uri = ?');
+        $stmt->execute([$calendarId, $objectUri]);
+
+        $this->addChange($calendarId, $objectUri, 3);
+
+    }
+
+    /**
+     * Performs a calendar-query on the contents of this calendar.
+     *
+     * The calendar-query is defined in RFC4791 : CalDAV. Using the
+     * calendar-query it is possible for a client to request a specific set of
+     * object, based on contents of iCalendar properties, date-ranges and
+     * iCalendar component types (VTODO, VEVENT).
+     *
+     * This method should just return a list of (relative) urls that match this
+     * query.
+     *
+     * The list of filters are specified as an array. The exact array is
+     * documented by \Sabre\CalDAV\CalendarQueryParser.
+     *
+     * Note that it is extremely likely that getCalendarObject for every path
+     * returned from this method will be called almost immediately after. You
+     * may want to anticipate this to speed up these requests.
+     *
+     * This method provides a default implementation, which parses *all* the
+     * iCalendar objects in the specified calendar.
+     *
+     * This default may well be good enough for personal use, and calendars
+     * that aren't very large. But if you anticipate high usage, big calendars
+     * or high loads, you are strongly adviced to optimize certain paths.
+     *
+     * The best way to do so is override this method and to optimize
+     * specifically for 'common filters'.
+     *
+     * Requests that are extremely common are:
+     *   * requests for just VEVENTS
+     *   * requests for just VTODO
+     *   * requests with a time-range-filter on a VEVENT.
+     *
+     * ..and combinations of these requests. It may not be worth it to try to
+     * handle every possible situation and just rely on the (relatively
+     * easy to use) CalendarQueryValidator to handle the rest.
+     *
+     * Note that especially time-range-filters may be difficult to parse. A
+     * time-range filter specified on a VEVENT must for instance also handle
+     * recurrence rules correctly.
+     * A good example of how to interprete all these filters can also simply
+     * be found in \Sabre\CalDAV\CalendarQueryFilter. This class is as correct
+     * as possible, so it gives you a good idea on what type of stuff you need
+     * to think of.
+     *
+     * This specific implementation (for the PDO) backend optimizes filters on
+     * specific components, and VEVENT time-ranges.
+     *
+     * @param string $calendarId
+     * @param array $filters
+     * @return array
+     */
+    function calendarQuery($calendarId, array $filters) {
+
+        $componentType = null;
+        $requirePostFilter = true;
+        $timeRange = null;
+
+        // if no filters were specified, we don't need to filter after a query
+        if (!$filters['prop-filters'] && !$filters['comp-filters']) {
+            $requirePostFilter = false;
+        }
+
+        // Figuring out if there's a component filter
+        if (count($filters['comp-filters']) > 0 && !$filters['comp-filters'][0]['is-not-defined']) {
+            $componentType = $filters['comp-filters'][0]['name'];
+
+            // Checking if we need post-filters
+            if (!$filters['prop-filters'] && !$filters['comp-filters'][0]['comp-filters'] && !$filters['comp-filters'][0]['time-range'] && !$filters['comp-filters'][0]['prop-filters']) {
+                $requirePostFilter = false;
+            }
+            // There was a time-range filter
+            if ($componentType == 'VEVENT' && isset($filters['comp-filters'][0]['time-range'])) {
+                $timeRange = $filters['comp-filters'][0]['time-range'];
+
+                // If start time OR the end time is not specified, we can do a
+                // 100% accurate mysql query.
+                if (!$filters['prop-filters'] && !$filters['comp-filters'][0]['comp-filters'] && !$filters['comp-filters'][0]['prop-filters'] && (!$timeRange['start'] || !$timeRange['end'])) {
+                    $requirePostFilter = false;
+                }
+            }
+
+        }
+
+        if ($requirePostFilter) {
+            $query = "SELECT uri, calendardata FROM " . $this->calendarObjectTableName . " WHERE calendarid = :calendarid";
+        } else {
+            $query = "SELECT uri FROM " . $this->calendarObjectTableName . " WHERE calendarid = :calendarid";
+        }
+
+        $values = [
+            'calendarid' => $calendarId,
+        ];
+
+        if ($componentType) {
+            $query .= " AND componenttype = :componenttype";
+            $values['componenttype'] = $componentType;
+        }
+
+        if ($timeRange && $timeRange['start']) {
+            $query .= " AND lastoccurence > :startdate";
+            $values['startdate'] = $timeRange['start']->getTimeStamp();
+        }
+        if ($timeRange && $timeRange['end']) {
+            $query .= " AND firstoccurence < :enddate";
+            $values['enddate'] = $timeRange['end']->getTimeStamp();
+        }
+
+        $stmt = $this->pdo->prepare($query);
+        $stmt->execute($values);
+
+        $result = [];
+        while ($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
+            if ($requirePostFilter) {
+                if (!$this->validateFilterForObject($row, $filters)) {
+                    continue;
+                }
+            }
+            $result[] = $row['uri'];
+
+        }
+
+        return $result;
+
+    }
+
+    /**
+     * Searches through all of a users calendars and calendar objects to find
+     * an object with a specific UID.
+     *
+     * This method should return the path to this object, relative to the
+     * calendar home, so this path usually only contains two parts:
+     *
+     * calendarpath/objectpath.ics
+     *
+     * If the uid is not found, return null.
+     *
+     * This method should only consider * objects that the principal owns, so
+     * any calendars owned by other principals that also appear in this
+     * collection should be ignored.
+     *
+     * @param string $principalUri
+     * @param string $uid
+     * @return string|null
+     */
+    function getCalendarObjectByUID($principalUri, $uid) {
+
+        $query = <<<SQL
+SELECT
+    calendars.uri AS calendaruri, calendarobjects.uri as objecturi
+FROM
+    $this->calendarObjectTableName AS calendarobjects
+LEFT JOIN
+    $this->calendarTableName AS calendars
+    ON calendarobjects.calendarid = calendars.id
+WHERE
+    calendars.principaluri = ?
+    AND
+    calendarobjects.uid = ?
+SQL;
+
+        $stmt = $this->pdo->prepare($query);
+        $stmt->execute([$principalUri, $uid]);
+
+        if ($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
+            return $row['calendaruri'] . '/' . $row['objecturi'];
+        }
+
+    }
+
+    /**
+     * The getChanges method returns all the changes that have happened, since
+     * the specified syncToken in the specified calendar.
+     *
+     * This function should return an array, such as the following:
+     *
+     * [
+     *   'syncToken' => 'The current synctoken',
+     *   'added'   => [
+     *      'new.txt',
+     *   ],
+     *   'modified'   => [
+     *      'modified.txt',
+     *   ],
+     *   'deleted' => [
+     *      'foo.php.bak',
+     *      'old.txt'
+     *   ]
+     * ];
+     *
+     * The returned syncToken property should reflect the *current* syncToken
+     * of the calendar, as reported in the {http://sabredav.org/ns}sync-token
+     * property this is needed here too, to ensure the operation is atomic.
+     *
+     * If the $syncToken argument is specified as null, this is an initial
+     * sync, and all members should be reported.
+     *
+     * The modified property is an array of nodenames that have changed since
+     * the last token.
+     *
+     * The deleted property is an array with nodenames, that have been deleted
+     * from collection.
+     *
+     * The $syncLevel argument is basically the 'depth' of the report. If it's
+     * 1, you only have to report changes that happened only directly in
+     * immediate descendants. If it's 2, it should also include changes from
+     * the nodes below the child collections. (grandchildren)
+     *
+     * The $limit argument allows a client to specify how many results should
+     * be returned at most. If the limit is not specified, it should be treated
+     * as infinite.
+     *
+     * If the limit (infinite or not) is higher than you're willing to return,
+     * you should throw a Sabre\DAV\Exception\TooMuchMatches() exception.
+     *
+     * If the syncToken is expired (due to data cleanup) or unknown, you must
+     * return null.
+     *
+     * The limit is 'suggestive'. You are free to ignore it.
+     *
+     * @param string $calendarId
+     * @param string $syncToken
+     * @param int $syncLevel
+     * @param int $limit
+     * @return array
+     */
+    function getChangesForCalendar($calendarId, $syncToken, $syncLevel, $limit = null) {
+
+        // Current synctoken
+        $stmt = $this->pdo->prepare('SELECT synctoken FROM ' . $this->calendarTableName . ' WHERE id = ?');
+        $stmt->execute([ $calendarId ]);
+        $currentToken = $stmt->fetchColumn(0);
+
+        if (is_null($currentToken)) return null;
+
+        $result = [
+            'syncToken' => $currentToken,
+            'added'     => [],
+            'modified'  => [],
+            'deleted'   => [],
+        ];
+
+        if ($syncToken) {
+
+            $query = "SELECT uri, operation FROM " . $this->calendarChangesTableName . " WHERE synctoken >= ? AND synctoken < ? AND calendarid = ? ORDER BY synctoken";
+            if ($limit > 0) $query .= " LIMIT " . (int)$limit;
+
+            // Fetching all changes
+            $stmt = $this->pdo->prepare($query);
+            $stmt->execute([$syncToken, $currentToken, $calendarId]);
+
+            $changes = [];
+
+            // This loop ensures that any duplicates are overwritten, only the
+            // last change on a node is relevant.
+            while ($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
+
+                $changes[$row['uri']] = $row['operation'];
+
+            }
+
+            foreach ($changes as $uri => $operation) {
+
+                switch ($operation) {
+                    case 1 :
+                        $result['added'][] = $uri;
+                        break;
+                    case 2 :
+                        $result['modified'][] = $uri;
+                        break;
+                    case 3 :
+                        $result['deleted'][] = $uri;
+                        break;
+                }
+
+            }
+        } else {
+            // No synctoken supplied, this is the initial sync.
+            $query = "SELECT uri FROM " . $this->calendarObjectTableName . " WHERE calendarid = ?";
+            $stmt = $this->pdo->prepare($query);
+            $stmt->execute([$calendarId]);
+
+            $result['added'] = $stmt->fetchAll(\PDO::FETCH_COLUMN);
+        }
+        return $result;
+
+    }
+
+    /**
+     * Adds a change record to the calendarchanges table.
+     *
+     * @param mixed $calendarId
+     * @param string $objectUri
+     * @param int $operation 1 = add, 2 = modify, 3 = delete.
+     * @return void
+     */
+    protected function addChange($calendarId, $objectUri, $operation) {
+
+        $stmt = $this->pdo->prepare('INSERT INTO ' . $this->calendarChangesTableName . ' (uri, synctoken, calendarid, operation) SELECT ?, synctoken, ?, ? FROM ' . $this->calendarTableName . ' WHERE id = ?');
+        $stmt->execute([
+            $objectUri,
+            $calendarId,
+            $operation,
+            $calendarId
+        ]);
+        $stmt = $this->pdo->prepare('UPDATE ' . $this->calendarTableName . ' SET synctoken = synctoken + 1 WHERE id = ?');
+        $stmt->execute([
+            $calendarId
+        ]);
+
+    }
+
+    /**
+     * Returns a list of subscriptions for a principal.
+     *
+     * Every subscription is an array with the following keys:
+     *  * id, a unique id that will be used by other functions to modify the
+     *    subscription. This can be the same as the uri or a database key.
+     *  * uri. This is just the 'base uri' or 'filename' of the subscription.
+     *  * principaluri. The owner of the subscription. Almost always the same as
+     *    principalUri passed to this method.
+     *  * source. Url to the actual feed
+     *
+     * Furthermore, all the subscription info must be returned too:
+     *
+     * 1. {DAV:}displayname
+     * 2. {http://apple.com/ns/ical/}refreshrate
+     * 3. {http://calendarserver.org/ns/}subscribed-strip-todos (omit if todos
+     *    should not be stripped).
+     * 4. {http://calendarserver.org/ns/}subscribed-strip-alarms (omit if alarms
+     *    should not be stripped).
+     * 5. {http://calendarserver.org/ns/}subscribed-strip-attachments (omit if
+     *    attachments should not be stripped).
+     * 7. {http://apple.com/ns/ical/}calendar-color
+     * 8. {http://apple.com/ns/ical/}calendar-order
+     * 9. {urn:ietf:params:xml:ns:caldav}supported-calendar-component-set
+     *    (should just be an instance of
+     *    Sabre\CalDAV\Property\SupportedCalendarComponentSet, with a bunch of
+     *    default components).
+     *
+     * @param string $principalUri
+     * @return array
+     */
+    function getSubscriptionsForUser($principalUri) {
+
+        $fields = array_values($this->subscriptionPropertyMap);
+        $fields[] = 'id';
+        $fields[] = 'uri';
+        $fields[] = 'source';
+        $fields[] = 'principaluri';
+        $fields[] = 'lastmodified';
+
+        // Making fields a comma-delimited list
+        $fields = implode(', ', $fields);
+        $stmt = $this->pdo->prepare("SELECT " . $fields . " FROM " . $this->calendarSubscriptionsTableName . " WHERE principaluri = ? ORDER BY calendarorder ASC");
+        $stmt->execute([$principalUri]);
+
+        $subscriptions = [];
+        while ($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
+
+            $subscription = [
+                'id'           => $row['id'],
+                'uri'          => $row['uri'],
+                'principaluri' => $row['principaluri'],
+                'source'       => $row['source'],
+                'lastmodified' => $row['lastmodified'],
+
+                '{' . CalDAV\Plugin::NS_CALDAV . '}supported-calendar-component-set' => new CalDAV\Xml\Property\SupportedCalendarComponentSet(['VTODO', 'VEVENT']),
+            ];
+
+            foreach ($this->subscriptionPropertyMap as $xmlName => $dbName) {
+                if (!is_null($row[$dbName])) {
+                    $subscription[$xmlName] = $row[$dbName];
+                }
+            }
+
+            $subscriptions[] = $subscription;
+
+        }
+
+        return $subscriptions;
+
+    }
+
+    /**
+     * Creates a new subscription for a principal.
+     *
+     * If the creation was a success, an id must be returned that can be used to reference
+     * this subscription in other methods, such as updateSubscription.
+     *
+     * @param string $principalUri
+     * @param string $uri
+     * @param array $properties
+     * @return mixed
+     */
+    function createSubscription($principalUri, $uri, array $properties) {
+
+        $fieldNames = [
+            'principaluri',
+            'uri',
+            'source',
+            'lastmodified',
+        ];
+
+        if (!isset($properties['{http://calendarserver.org/ns/}source'])) {
+            throw new Forbidden('The {http://calendarserver.org/ns/}source property is required when creating subscriptions');
+        }
+
+        $values = [
+            ':principaluri' => $principalUri,
+            ':uri'          => $uri,
+            ':source'       => $properties['{http://calendarserver.org/ns/}source']->getHref(),
+            ':lastmodified' => time(),
+        ];
+
+        foreach ($this->subscriptionPropertyMap as $xmlName => $dbName) {
+            if (isset($properties[$xmlName])) {
+
+                $values[':' . $dbName] = $properties[$xmlName];
+                $fieldNames[] = $dbName;
+            }
+        }
+
+        $stmt = $this->pdo->prepare("INSERT INTO " . $this->calendarSubscriptionsTableName . " (" . implode(', ', $fieldNames) . ") VALUES (" . implode(', ', array_keys($values)) . ")");
+        $stmt->execute($values);
+
+        return $this->pdo->lastInsertId();
+
+    }
+
+    /**
+     * Updates a subscription
+     *
+     * The list of mutations is stored in a Sabre\DAV\PropPatch object.
+     * To do the actual updates, you must tell this object which properties
+     * you're going to process with the handle() method.
+     *
+     * Calling the handle method is like telling the PropPatch object "I
+     * promise I can handle updating this property".
+     *
+     * Read the PropPatch documenation for more info and examples.
+     *
+     * @param mixed $subscriptionId
+     * @param \Sabre\DAV\PropPatch $propPatch
+     * @return void
+     */
+    function updateSubscription($subscriptionId, DAV\PropPatch $propPatch) {
+
+        $supportedProperties = array_keys($this->subscriptionPropertyMap);
+        $supportedProperties[] = '{http://calendarserver.org/ns/}source';
+
+        $propPatch->handle($supportedProperties, function($mutations) use ($subscriptionId) {
+
+            $newValues = [];
+
+            foreach ($mutations as $propertyName => $propertyValue) {
+
+                if ($propertyName === '{http://calendarserver.org/ns/}source') {
+                    $newValues['source'] = $propertyValue->getHref();
+                } else {
+                    $fieldName = $this->subscriptionPropertyMap[$propertyName];
+                    $newValues[$fieldName] = $propertyValue;
+                }
+
+            }
+
+            // Now we're generating the sql query.
+            $valuesSql = [];
+            foreach ($newValues as $fieldName => $value) {
+                $valuesSql[] = $fieldName . ' = ?';
+            }
+
+            $stmt = $this->pdo->prepare("UPDATE " . $this->calendarSubscriptionsTableName . " SET " . implode(', ', $valuesSql) . ", lastmodified = ? WHERE id = ?");
+            $newValues['lastmodified'] = time();
+            $newValues['id'] = $subscriptionId;
+            $stmt->execute(array_values($newValues));
+
+            return true;
+
+        });
+
+    }
+
+    /**
+     * Deletes a subscription
+     *
+     * @param mixed $subscriptionId
+     * @return void
+     */
+    function deleteSubscription($subscriptionId) {
+
+        $stmt = $this->pdo->prepare('DELETE FROM ' . $this->calendarSubscriptionsTableName . ' WHERE id = ?');
+        $stmt->execute([$subscriptionId]);
+
+    }
+
+    /**
+     * Returns a single scheduling object.
+     *
+     * The returned array should contain the following elements:
+     *   * uri - A unique basename for the object. This will be used to
+     *           construct a full uri.
+     *   * calendardata - The iCalendar object
+     *   * lastmodified - The last modification date. Can be an int for a unix
+     *                    timestamp, or a PHP DateTime object.
+     *   * etag - A unique token that must change if the object changed.
+     *   * size - The size of the object, in bytes.
+     *
+     * @param string $principalUri
+     * @param string $objectUri
+     * @return array
+     */
+    function getSchedulingObject($principalUri, $objectUri) {
+
+        $stmt = $this->pdo->prepare('SELECT uri, calendardata, lastmodified, etag, size FROM ' . $this->schedulingObjectTableName . ' WHERE principaluri = ? AND uri = ?');
+        $stmt->execute([$principalUri, $objectUri]);
+        $row = $stmt->fetch(\PDO::FETCH_ASSOC);
+
+        if (!$row) return null;
+
+        return [
+            'uri'          => $row['uri'],
+            'calendardata' => $row['calendardata'],
+            'lastmodified' => $row['lastmodified'],
+            'etag'         => '"' . $row['etag'] . '"',
+            'size'         => (int)$row['size'],
+         ];
+
+    }
+
+    /**
+     * Returns all scheduling objects for the inbox collection.
+     *
+     * These objects should be returned as an array. Every item in the array
+     * should follow the same structure as returned from getSchedulingObject.
+     *
+     * The main difference is that 'calendardata' is optional.
+     *
+     * @param string $principalUri
+     * @return array
+     */
+    function getSchedulingObjects($principalUri) {
+
+        $stmt = $this->pdo->prepare('SELECT id, calendardata, uri, lastmodified, etag, size FROM ' . $this->schedulingObjectTableName . ' WHERE principaluri = ?');
+        $stmt->execute([$principalUri]);
+
+        $result = [];
+        foreach ($stmt->fetchAll(\PDO::FETCH_ASSOC) as $row) {
+            $result[] = [
+                'calendardata' => $row['calendardata'],
+                'uri'          => $row['uri'],
+                'lastmodified' => $row['lastmodified'],
+                'etag'         => '"' . $row['etag'] . '"',
+                'size'         => (int)$row['size'],
+            ];
+        }
+
+        return $result;
+
+    }
+
+    /**
+     * Deletes a scheduling object
+     *
+     * @param string $principalUri
+     * @param string $objectUri
+     * @return void
+     */
+    function deleteSchedulingObject($principalUri, $objectUri) {
+
+        $stmt = $this->pdo->prepare('DELETE FROM ' . $this->schedulingObjectTableName . ' WHERE principaluri = ? AND uri = ?');
+        $stmt->execute([$principalUri, $objectUri]);
+
+    }
+
+    /**
+     * Creates a new scheduling object. This should land in a users' inbox.
+     *
+     * @param string $principalUri
+     * @param string $objectUri
+     * @param string $objectData
+     * @return void
+     */
+    function createSchedulingObject($principalUri, $objectUri, $objectData) {
+
+        $stmt = $this->pdo->prepare('INSERT INTO ' . $this->schedulingObjectTableName . ' (principaluri, calendardata, uri, lastmodified, etag, size) VALUES (?, ?, ?, ?, ?, ?)');
+        $stmt->execute([$principalUri, $objectData, $objectUri, time(), md5($objectData), strlen($objectData) ]);
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Backend/SchedulingSupport.php b/vendor/sabre/dav/lib/CalDAV/Backend/SchedulingSupport.php
new file mode 100644
index 000000000..6ec0bf06b
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Backend/SchedulingSupport.php
@@ -0,0 +1,65 @@
+<?php
+
+namespace Sabre\CalDAV\Backend;
+
+/**
+ * Implementing this interface adds CalDAV Scheduling support to your caldav
+ * server, as defined in rfc6638.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface SchedulingSupport extends BackendInterface {
+
+    /**
+     * Returns a single scheduling object for the inbox collection.
+     *
+     * The returned array should contain the following elements:
+     *   * uri - A unique basename for the object. This will be used to
+     *           construct a full uri.
+     *   * calendardata - The iCalendar object
+     *   * lastmodified - The last modification date. Can be an int for a unix
+     *                    timestamp, or a PHP DateTime object.
+     *   * etag - A unique token that must change if the object changed.
+     *   * size - The size of the object, in bytes.
+     *
+     * @param string $principalUri
+     * @param string $objectUri
+     * @return array
+     */
+    function getSchedulingObject($principalUri, $objectUri);
+
+    /**
+     * Returns all scheduling objects for the inbox collection.
+     *
+     * These objects should be returned as an array. Every item in the array
+     * should follow the same structure as returned from getSchedulingObject.
+     *
+     * The main difference is that 'calendardata' is optional.
+     *
+     * @param string $principalUri
+     * @return array
+     */
+    function getSchedulingObjects($principalUri);
+
+    /**
+     * Deletes a scheduling object from the inbox collection.
+     *
+     * @param string $principalUri
+     * @param string $objectUri
+     * @return void
+     */
+    function deleteSchedulingObject($principalUri, $objectUri);
+
+    /**
+     * Creates a new scheduling object. This should land in a users' inbox.
+     *
+     * @param string $principalUri
+     * @param string $objectUri
+     * @param string $objectData
+     * @return void
+     */
+    function createSchedulingObject($principalUri, $objectUri, $objectData);
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Backend/SharingSupport.php b/vendor/sabre/dav/lib/CalDAV/Backend/SharingSupport.php
new file mode 100644
index 000000000..6a11b0ab1
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Backend/SharingSupport.php
@@ -0,0 +1,243 @@
+<?php
+
+namespace Sabre\CalDAV\Backend;
+
+/**
+ * Adds support for sharing features to a CalDAV server.
+ *
+ * Note: This feature is experimental, and may change in between different
+ * SabreDAV versions.
+ *
+ * Early warning: Currently SabreDAV provides no implementation for this. This
+ * is, because in it's current state there is no elegant way to do this.
+ * The problem lies in the fact that a real CalDAV server with sharing support
+ * would first need email support (with invite notifications), and really also
+ * a browser-frontend that allows people to accept or reject these shares.
+ *
+ * In addition, the CalDAV backends are currently kept as independent as
+ * possible, and should not be aware of principals, email addresses or
+ * accounts.
+ *
+ * Adding an implementation for Sharing to standard-sabredav would contradict
+ * these goals, so for this reason this is currently not implemented, although
+ * it may very well in the future; but probably not before SabreDAV 2.0.
+ *
+ * The interface works however, so if you implement all this, and do it
+ * correctly sharing _will_ work. It's not particularly easy, and I _urge you_
+ * to make yourself acquainted with the following document first:
+ *
+ * https://trac.calendarserver.org/browser/CalendarServer/trunk/doc/Extensions/caldav-sharing.txt
+ *
+ * An overview
+ * ===========
+ *
+ * Implementing this interface will allow a user to share his or her calendars
+ * to other users. Effectively, when a calendar is shared the calendar will
+ * show up in both the Sharer's and Sharee's calendar-home root.
+ * This interface adds a few methods that ensure that this happens, and there
+ * are also a number of new requirements in the base-class you must now follow.
+ *
+ *
+ * How it works
+ * ============
+ *
+ * When a user shares a calendar, the updateShares() method will be called with
+ * a list of sharees that are now added, and a list of sharees that have been
+ * removed.
+ * Removal is instant, but when a sharee is added the sharee first gets a
+ * chance to accept or reject the invitation for a share.
+ *
+ * After a share is accepted, the calendar will be returned from
+ * getUserCalendars for both the sharer, and the sharee.
+ *
+ * If the sharee deletes the calendar, only their share gets deleted. When the
+ * owner deletes a calendar, it will be removed for everybody.
+ *
+ *
+ * Notifications
+ * =============
+ *
+ * During all these sharing operations, a lot of notifications are sent back
+ * and forward.
+ *
+ * Whenever the list of sharees for a calendar has been changed (they have been
+ * added, removed or modified) all sharees should get a notification for this
+ * change.
+ * This notification is always represented by:
+ *
+ * Sabre\CalDAV\Notifications\Notification\Invite
+ *
+ * In the case of an invite, the sharee may reply with an 'accept' or
+ * 'decline'. These are always represented by:
+ *
+ * Sabre\CalDAV\Notifications\Notification\InviteReply
+ *
+ *
+ * Calendar access by sharees
+ * ==========================
+ *
+ * As mentioned earlier, shared calendars must now also be returned for
+ * getCalendarsForUser for sharees. A few things change though.
+ *
+ * The following properties must be specified:
+ *
+ * 1. {http://calendarserver.org/ns/}shared-url
+ *
+ * This property MUST contain the url to the original calendar, that is.. the
+ * path to the calendar from the owner.
+ *
+ * 2. {http://sabredav.org/ns}owner-principal
+ *
+ * This is a url to to the principal who is sharing the calendar.
+ *
+ * 3. {http://sabredav.org/ns}read-only
+ *
+ * This should be either 0 or 1, depending on if the user has read-only or
+ * read-write access to the calendar.
+ *
+ * Only when this is done, the calendar will correctly be marked as a calendar
+ * that's shared to him, thus allowing clients to display the correct interface
+ * and ACL enforcement.
+ *
+ * If a sharee deletes their calendar, only their instance of the calendar
+ * should be deleted, the original should still exists.
+ * Pretty much any 'dead' WebDAV properties on these shared calendars should be
+ * specific to a user. This means that if the displayname is changed by a
+ * sharee, the original is not affected. This is also true for:
+ *   * The description
+ *   * The color
+ *   * The order
+ *   * And any other dead properties.
+ *
+ * Properties like a ctag should not be different for multiple instances of the
+ * calendar.
+ *
+ * Lastly, objects *within* calendars should also have user-specific data. The
+ * two things that are user-specific are:
+ *   * VALARM objects
+ *   * The TRANSP property
+ *
+ * This _also_ implies that if a VALARM is deleted by a sharee for some event,
+ * this has no effect on the original VALARM.
+ *
+ * Understandably, the this last requirement is one of the hardest.
+ * Realisticly, I can see people ignoring this part of the spec, but that could
+ * cause a different set of issues.
+ *
+ *
+ * Publishing
+ * ==========
+ *
+ * When a user publishes a url, the server should generate a 'publish url'.
+ * This is a read-only url, anybody can use to consume the calendar feed.
+ *
+ * Calendars are in one of two states:
+ *   * published
+ *   * unpublished
+ *
+ * If a calendar is published, the following property should be returned
+ * for each calendar in getCalendarsForUser.
+ *
+ * {http://calendarserver.org/ns/}publish-url
+ *
+ * This element should contain a {DAV:}href element, which points to the
+ * public url that does not require authentication. Unlike every other href,
+ * this url must be absolute.
+ *
+ * Ideally, the following property is always returned
+ *
+ * {http://calendarserver.org/ns/}pre-publish-url
+ *
+ * This property should contain the url that the calendar _would_ have, if it
+ * were to be published. iCal uses this to display the url, before the user
+ * will actually publish it.
+ *
+ *
+ * Selectively disabling publish or share feature
+ * ==============================================
+ *
+ * If Sabre\CalDAV\Property\AllowedSharingModes is returned from
+ * getCalendarsForUser, this allows the server to specify whether either sharing,
+ * or publishing is supported.
+ *
+ * This allows a client to determine in advance which features are available,
+ * and update the interface appropriately. If this property is not returned by
+ * the backend, the SharingPlugin automatically injects it and assumes both
+ * features are available.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface SharingSupport extends NotificationSupport {
+
+    /**
+     * Updates the list of shares.
+     *
+     * The first array is a list of people that are to be added to the
+     * calendar.
+     *
+     * Every element in the add array has the following properties:
+     *   * href - A url. Usually a mailto: address
+     *   * commonName - Usually a first and last name, or false
+     *   * summary - A description of the share, can also be false
+     *   * readOnly - A boolean value
+     *
+     * Every element in the remove array is just the address string.
+     *
+     * Note that if the calendar is currently marked as 'not shared' by and
+     * this method is called, the calendar should be 'upgraded' to a shared
+     * calendar.
+     *
+     * @param mixed $calendarId
+     * @param array $add
+     * @param array $remove
+     * @return void
+     */
+    function updateShares($calendarId, array $add, array $remove);
+
+    /**
+     * Returns the list of people whom this calendar is shared with.
+     *
+     * Every element in this array should have the following properties:
+     *   * href - Often a mailto: address
+     *   * commonName - Optional, for example a first + last name
+     *   * status - See the Sabre\CalDAV\SharingPlugin::STATUS_ constants.
+     *   * readOnly - boolean
+     *   * summary - Optional, a description for the share
+     *
+     * This method may be called by either the original instance of the
+     * calendar, as well as the shared instances. In the case of the shared
+     * instances, it is perfectly acceptable to return an empty array in case
+     * there are privacy concerns.
+     *
+     * @param mixed $calendarId
+     * @return array
+     */
+    function getShares($calendarId);
+
+    /**
+     * This method is called when a user replied to a request to share.
+     *
+     * If the user chose to accept the share, this method should return the
+     * newly created calendar url.
+     *
+     * @param string href The sharee who is replying (often a mailto: address)
+     * @param int status One of the SharingPlugin::STATUS_* constants
+     * @param string $calendarUri The url to the calendar thats being shared
+     * @param string $inReplyTo The unique id this message is a response to
+     * @param string $summary A description of the reply
+     * @return null|string
+     */
+    function shareReply($href, $status, $calendarUri, $inReplyTo, $summary = null);
+
+    /**
+     * Publishes a calendar
+     *
+     * @param mixed $calendarId
+     * @param bool $value
+     * @return void
+     */
+    function setPublishStatus($calendarId, $value);
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Backend/SubscriptionSupport.php b/vendor/sabre/dav/lib/CalDAV/Backend/SubscriptionSupport.php
new file mode 100644
index 000000000..a39289f5e
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Backend/SubscriptionSupport.php
@@ -0,0 +1,89 @@
+<?php
+
+namespace Sabre\CalDAV\Backend;
+
+use Sabre\DAV;
+
+/**
+ * Every CalDAV backend must at least implement this interface.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface SubscriptionSupport extends BackendInterface {
+
+    /**
+     * Returns a list of subscriptions for a principal.
+     *
+     * Every subscription is an array with the following keys:
+     *  * id, a unique id that will be used by other functions to modify the
+     *    subscription. This can be the same as the uri or a database key.
+     *  * uri. This is just the 'base uri' or 'filename' of the subscription.
+     *  * principaluri. The owner of the subscription. Almost always the same as
+     *    principalUri passed to this method.
+     *
+     * Furthermore, all the subscription info must be returned too:
+     *
+     * 1. {DAV:}displayname
+     * 2. {http://apple.com/ns/ical/}refreshrate
+     * 3. {http://calendarserver.org/ns/}subscribed-strip-todos (omit if todos
+     *    should not be stripped).
+     * 4. {http://calendarserver.org/ns/}subscribed-strip-alarms (omit if alarms
+     *    should not be stripped).
+     * 5. {http://calendarserver.org/ns/}subscribed-strip-attachments (omit if
+     *    attachments should not be stripped).
+     * 6. {http://calendarserver.org/ns/}source (Must be a
+     *     Sabre\DAV\Property\Href).
+     * 7. {http://apple.com/ns/ical/}calendar-color
+     * 8. {http://apple.com/ns/ical/}calendar-order
+     * 9. {urn:ietf:params:xml:ns:caldav}supported-calendar-component-set
+     *    (should just be an instance of
+     *    Sabre\CalDAV\Property\SupportedCalendarComponentSet, with a bunch of
+     *    default components).
+     *
+     * @param string $principalUri
+     * @return array
+     */
+    function getSubscriptionsForUser($principalUri);
+
+    /**
+     * Creates a new subscription for a principal.
+     *
+     * If the creation was a success, an id must be returned that can be used to reference
+     * this subscription in other methods, such as updateSubscription.
+     *
+     * @param string $principalUri
+     * @param string $uri
+     * @param array $properties
+     * @return mixed
+     */
+    function createSubscription($principalUri, $uri, array $properties);
+
+    /**
+     * Updates a subscription
+     *
+     * The list of mutations is stored in a Sabre\DAV\PropPatch object.
+     * To do the actual updates, you must tell this object which properties
+     * you're going to process with the handle() method.
+     *
+     * Calling the handle method is like telling the PropPatch object "I
+     * promise I can handle updating this property".
+     *
+     * Read the PropPatch documenation for more info and examples.
+     *
+     * @param mixed $subscriptionId
+     * @param \Sabre\DAV\PropPatch $propPatch
+     * @return void
+     */
+    function updateSubscription($subscriptionId, DAV\PropPatch $propPatch);
+
+    /**
+     * Deletes a subscription.
+     *
+     * @param mixed $subscriptionId
+     * @return void
+     */
+    function deleteSubscription($subscriptionId);
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Backend/SyncSupport.php b/vendor/sabre/dav/lib/CalDAV/Backend/SyncSupport.php
new file mode 100644
index 000000000..a934505f9
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Backend/SyncSupport.php
@@ -0,0 +1,81 @@
+<?php
+
+namespace Sabre\CalDAV\Backend;
+
+/**
+ * WebDAV-sync support for CalDAV backends.
+ *
+ * In order for backends to advertise support for WebDAV-sync, this interface
+ * must be implemented.
+ *
+ * Implementing this can result in a significant reduction of bandwidth and CPU
+ * time.
+ *
+ * For this to work, you _must_ return a {http://sabredav.org/ns}sync-token
+ * property from getCalendarsFromUser.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface SyncSupport extends BackendInterface {
+
+    /**
+     * The getChanges method returns all the changes that have happened, since
+     * the specified syncToken in the specified calendar.
+     *
+     * This function should return an array, such as the following:
+     *
+     * [
+     *   'syncToken' => 'The current synctoken',
+     *   'added'   => [
+     *      'new.txt',
+     *   ],
+     *   'modified'   => [
+     *      'modified.txt',
+     *   ],
+     *   'deleted' => [
+     *      'foo.php.bak',
+     *      'old.txt'
+     *   ]
+     * );
+     *
+     * The returned syncToken property should reflect the *current* syncToken
+     * of the calendar, as reported in the {http://sabredav.org/ns}sync-token
+     * property This is * needed here too, to ensure the operation is atomic.
+     *
+     * If the $syncToken argument is specified as null, this is an initial
+     * sync, and all members should be reported.
+     *
+     * The modified property is an array of nodenames that have changed since
+     * the last token.
+     *
+     * The deleted property is an array with nodenames, that have been deleted
+     * from collection.
+     *
+     * The $syncLevel argument is basically the 'depth' of the report. If it's
+     * 1, you only have to report changes that happened only directly in
+     * immediate descendants. If it's 2, it should also include changes from
+     * the nodes below the child collections. (grandchildren)
+     *
+     * The $limit argument allows a client to specify how many results should
+     * be returned at most. If the limit is not specified, it should be treated
+     * as infinite.
+     *
+     * If the limit (infinite or not) is higher than you're willing to return,
+     * you should throw a Sabre\DAV\Exception\TooMuchMatches() exception.
+     *
+     * If the syncToken is expired (due to data cleanup) or unknown, you must
+     * return null.
+     *
+     * The limit is 'suggestive'. You are free to ignore it.
+     *
+     * @param string $calendarId
+     * @param string $syncToken
+     * @param int $syncLevel
+     * @param int $limit
+     * @return array
+     */
+    function getChangesForCalendar($calendarId, $syncToken, $syncLevel, $limit = null);
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Calendar.php b/vendor/sabre/dav/lib/CalDAV/Calendar.php
new file mode 100644
index 000000000..ff8e19b15
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Calendar.php
@@ -0,0 +1,527 @@
+<?php
+
+namespace Sabre\CalDAV;
+
+use Sabre\DAV;
+use Sabre\DAVACL;
+use Sabre\DAV\PropPatch;
+
+/**
+ * This object represents a CalDAV calendar.
+ *
+ * A calendar can contain multiple TODO and or Events. These are represented
+ * as \Sabre\CalDAV\CalendarObject objects.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Calendar implements ICalendar, DAV\IProperties, DAV\Sync\ISyncCollection, DAV\IMultiGet {
+
+    /**
+     * This is an array with calendar information
+     *
+     * @var array
+     */
+    protected $calendarInfo;
+
+    /**
+     * CalDAV backend
+     *
+     * @var Backend\BackendInterface
+     */
+    protected $caldavBackend;
+
+    /**
+     * Constructor
+     *
+     * @param Backend\BackendInterface $caldavBackend
+     * @param array $calendarInfo
+     */
+    function __construct(Backend\BackendInterface $caldavBackend, $calendarInfo) {
+
+        $this->caldavBackend = $caldavBackend;
+        $this->calendarInfo = $calendarInfo;
+
+    }
+
+    /**
+     * Returns the name of the calendar
+     *
+     * @return string
+     */
+    function getName() {
+
+        return $this->calendarInfo['uri'];
+
+    }
+
+    /**
+     * Updates properties on this node.
+     *
+     * This method received a PropPatch object, which contains all the
+     * information about the update.
+     *
+     * To update specific properties, call the 'handle' method on this object.
+     * Read the PropPatch documentation for more information.
+     *
+     * @param PropPatch $propPatch
+     * @return void
+     */
+    function propPatch(PropPatch $propPatch) {
+
+        return $this->caldavBackend->updateCalendar($this->calendarInfo['id'], $propPatch);
+
+    }
+
+    /**
+     * Returns the list of properties
+     *
+     * @param array $requestedProperties
+     * @return array
+     */
+    function getProperties($requestedProperties) {
+
+        $response = [];
+
+        foreach ($this->calendarInfo as $propName => $propValue) {
+
+            if ($propName[0] === '{')
+                $response[$propName] = $this->calendarInfo[$propName];
+
+        }
+        return $response;
+
+    }
+
+    /**
+     * Returns a calendar object
+     *
+     * The contained calendar objects are for example Events or Todo's.
+     *
+     * @param string $name
+     * @return \Sabre\CalDAV\ICalendarObject
+     */
+    function getChild($name) {
+
+        $obj = $this->caldavBackend->getCalendarObject($this->calendarInfo['id'], $name);
+
+        if (!$obj) throw new DAV\Exception\NotFound('Calendar object not found');
+
+        $obj['acl'] = $this->getChildACL();
+
+        return new CalendarObject($this->caldavBackend, $this->calendarInfo, $obj);
+
+    }
+
+    /**
+     * Returns the full list of calendar objects
+     *
+     * @return array
+     */
+    function getChildren() {
+
+        $objs = $this->caldavBackend->getCalendarObjects($this->calendarInfo['id']);
+        $children = [];
+        foreach ($objs as $obj) {
+            $obj['acl'] = $this->getChildACL();
+            $children[] = new CalendarObject($this->caldavBackend, $this->calendarInfo, $obj);
+        }
+        return $children;
+
+    }
+
+    /**
+     * This method receives a list of paths in it's first argument.
+     * It must return an array with Node objects.
+     *
+     * If any children are not found, you do not have to return them.
+     *
+     * @param string[] $paths
+     * @return array
+     */
+    function getMultipleChildren(array $paths) {
+
+        $objs = $this->caldavBackend->getMultipleCalendarObjects($this->calendarInfo['id'], $paths);
+        $children = [];
+        foreach ($objs as $obj) {
+            $obj['acl'] = $this->getChildACL();
+            $children[] = new CalendarObject($this->caldavBackend, $this->calendarInfo, $obj);
+        }
+        return $children;
+
+    }
+
+    /**
+     * Checks if a child-node exists.
+     *
+     * @param string $name
+     * @return bool
+     */
+    function childExists($name) {
+
+        $obj = $this->caldavBackend->getCalendarObject($this->calendarInfo['id'], $name);
+        if (!$obj)
+            return false;
+        else
+            return true;
+
+    }
+
+    /**
+     * Creates a new directory
+     *
+     * We actually block this, as subdirectories are not allowed in calendars.
+     *
+     * @param string $name
+     * @return void
+     */
+    function createDirectory($name) {
+
+        throw new DAV\Exception\MethodNotAllowed('Creating collections in calendar objects is not allowed');
+
+    }
+
+    /**
+     * Creates a new file
+     *
+     * The contents of the new file must be a valid ICalendar string.
+     *
+     * @param string $name
+     * @param resource $calendarData
+     * @return string|null
+     */
+    function createFile($name, $calendarData = null) {
+
+        if (is_resource($calendarData)) {
+            $calendarData = stream_get_contents($calendarData);
+        }
+        return $this->caldavBackend->createCalendarObject($this->calendarInfo['id'], $name, $calendarData);
+
+    }
+
+    /**
+     * Deletes the calendar.
+     *
+     * @return void
+     */
+    function delete() {
+
+        $this->caldavBackend->deleteCalendar($this->calendarInfo['id']);
+
+    }
+
+    /**
+     * Renames the calendar. Note that most calendars use the
+     * {DAV:}displayname to display a name to display a name.
+     *
+     * @param string $newName
+     * @return void
+     */
+    function setName($newName) {
+
+        throw new DAV\Exception\MethodNotAllowed('Renaming calendars is not yet supported');
+
+    }
+
+    /**
+     * Returns the last modification date as a unix timestamp.
+     *
+     * @return void
+     */
+    function getLastModified() {
+
+        return null;
+
+    }
+
+    /**
+     * Returns the owner principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getOwner() {
+
+        return $this->calendarInfo['principaluri'];
+
+    }
+
+    /**
+     * Returns a group principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getGroup() {
+
+        return null;
+
+    }
+
+    /**
+     * Returns a list of ACE's for this node.
+     *
+     * Each ACE has the following properties:
+     *   * 'privilege', a string such as {DAV:}read or {DAV:}write. These are
+     *     currently the only supported privileges
+     *   * 'principal', a url to the principal who owns the node
+     *   * 'protected' (optional), indicating that this ACE is not allowed to
+     *      be updated.
+     *
+     * @return array
+     */
+    function getACL() {
+
+        $acl = [
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->getOwner(),
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->getOwner() . '/calendar-proxy-write',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->getOwner() . '/calendar-proxy-read',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{' . Plugin::NS_CALDAV . '}read-free-busy',
+                'principal' => '{DAV:}authenticated',
+                'protected' => true,
+            ],
+
+        ];
+        if (empty($this->calendarInfo['{http://sabredav.org/ns}read-only'])) {
+            $acl[] = [
+                'privilege' => '{DAV:}write',
+                'principal' => $this->getOwner(),
+                'protected' => true,
+            ];
+            $acl[] = [
+                'privilege' => '{DAV:}write',
+                'principal' => $this->getOwner() . '/calendar-proxy-write',
+                'protected' => true,
+            ];
+        }
+
+        return $acl;
+
+    }
+
+    /**
+     * This method returns the ACL's for calendar objects in this calendar.
+     * The result of this method automatically gets passed to the
+     * calendar-object nodes in the calendar.
+     *
+     * @return array
+     */
+    function getChildACL() {
+
+        $acl = [
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->getOwner(),
+                'protected' => true,
+            ],
+
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->getOwner() . '/calendar-proxy-write',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->getOwner() . '/calendar-proxy-read',
+                'protected' => true,
+            ],
+
+        ];
+        if (empty($this->calendarInfo['{http://sabredav.org/ns}read-only'])) {
+            $acl[] = [
+                'privilege' => '{DAV:}write',
+                'principal' => $this->getOwner(),
+                'protected' => true,
+            ];
+            $acl[] = [
+                'privilege' => '{DAV:}write',
+                'principal' => $this->getOwner() . '/calendar-proxy-write',
+                'protected' => true,
+            ];
+
+        }
+        return $acl;
+
+    }
+
+    /**
+     * Updates the ACL
+     *
+     * This method will receive a list of new ACE's.
+     *
+     * @param array $acl
+     * @return void
+     */
+    function setACL(array $acl) {
+
+        throw new DAV\Exception\MethodNotAllowed('Changing ACL is not yet supported');
+
+    }
+
+    /**
+     * Returns the list of supported privileges for this node.
+     *
+     * The returned data structure is a list of nested privileges.
+     * See \Sabre\DAVACL\Plugin::getDefaultSupportedPrivilegeSet for a simple
+     * standard structure.
+     *
+     * If null is returned from this method, the default privilege set is used,
+     * which is fine for most common usecases.
+     *
+     * @return array|null
+     */
+    function getSupportedPrivilegeSet() {
+
+        $default = DAVACL\Plugin::getDefaultSupportedPrivilegeSet();
+
+        // We need to inject 'read-free-busy' in the tree, aggregated under
+        // {DAV:}read.
+        foreach ($default['aggregates'] as &$agg) {
+
+            if ($agg['privilege'] !== '{DAV:}read') continue;
+
+            $agg['aggregates'][] = [
+                'privilege' => '{' . Plugin::NS_CALDAV . '}read-free-busy',
+            ];
+
+        }
+        return $default;
+
+    }
+
+    /**
+     * Performs a calendar-query on the contents of this calendar.
+     *
+     * The calendar-query is defined in RFC4791 : CalDAV. Using the
+     * calendar-query it is possible for a client to request a specific set of
+     * object, based on contents of iCalendar properties, date-ranges and
+     * iCalendar component types (VTODO, VEVENT).
+     *
+     * This method should just return a list of (relative) urls that match this
+     * query.
+     *
+     * The list of filters are specified as an array. The exact array is
+     * documented by Sabre\CalDAV\CalendarQueryParser.
+     *
+     * @param array $filters
+     * @return array
+     */
+    function calendarQuery(array $filters) {
+
+        return $this->caldavBackend->calendarQuery($this->calendarInfo['id'], $filters);
+
+    }
+
+    /**
+     * This method returns the current sync-token for this collection.
+     * This can be any string.
+     *
+     * If null is returned from this function, the plugin assumes there's no
+     * sync information available.
+     *
+     * @return string|null
+     */
+    function getSyncToken() {
+
+        if (
+            $this->caldavBackend instanceof Backend\SyncSupport &&
+            isset($this->calendarInfo['{DAV:}sync-token'])
+        ) {
+            return $this->calendarInfo['{DAV:}sync-token'];
+        }
+        if (
+            $this->caldavBackend instanceof Backend\SyncSupport &&
+            isset($this->calendarInfo['{http://sabredav.org/ns}sync-token'])
+        ) {
+            return $this->calendarInfo['{http://sabredav.org/ns}sync-token'];
+        }
+
+    }
+
+    /**
+     * The getChanges method returns all the changes that have happened, since
+     * the specified syncToken and the current collection.
+     *
+     * This function should return an array, such as the following:
+     *
+     * [
+     *   'syncToken' => 'The current synctoken',
+     *   'added'   => [
+     *      'new.txt',
+     *   ],
+     *   'modified'   => [
+     *      'modified.txt',
+     *   ],
+     *   'deleted' => [
+     *      'foo.php.bak',
+     *      'old.txt'
+     *   ]
+     * ];
+     *
+     * The syncToken property should reflect the *current* syncToken of the
+     * collection, as reported getSyncToken(). This is needed here too, to
+     * ensure the operation is atomic.
+     *
+     * If the syncToken is specified as null, this is an initial sync, and all
+     * members should be reported.
+     *
+     * The modified property is an array of nodenames that have changed since
+     * the last token.
+     *
+     * The deleted property is an array with nodenames, that have been deleted
+     * from collection.
+     *
+     * The second argument is basically the 'depth' of the report. If it's 1,
+     * you only have to report changes that happened only directly in immediate
+     * descendants. If it's 2, it should also include changes from the nodes
+     * below the child collections. (grandchildren)
+     *
+     * The third (optional) argument allows a client to specify how many
+     * results should be returned at most. If the limit is not specified, it
+     * should be treated as infinite.
+     *
+     * If the limit (infinite or not) is higher than you're willing to return,
+     * you should throw a Sabre\DAV\Exception\TooMuchMatches() exception.
+     *
+     * If the syncToken is expired (due to data cleanup) or unknown, you must
+     * return null.
+     *
+     * The limit is 'suggestive'. You are free to ignore it.
+     *
+     * @param string $syncToken
+     * @param int $syncLevel
+     * @param int $limit
+     * @return array
+     */
+    function getChanges($syncToken, $syncLevel, $limit = null) {
+
+        if (!$this->caldavBackend instanceof Backend\SyncSupport) {
+            return null;
+        }
+
+        return $this->caldavBackend->getChangesForCalendar(
+            $this->calendarInfo['id'],
+            $syncToken,
+            $syncLevel,
+            $limit
+        );
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/CalendarHome.php b/vendor/sabre/dav/lib/CalDAV/CalendarHome.php
new file mode 100644
index 000000000..a53f829e2
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/CalendarHome.php
@@ -0,0 +1,430 @@
+<?php
+
+namespace Sabre\CalDAV;
+
+use Sabre\DAV;
+use Sabre\DAV\Exception\NotFound;
+use Sabre\DAV\MkCol;
+use Sabre\DAVACL;
+use Sabre\HTTP\URLUtil;
+
+/**
+ * The CalendarHome represents a node that is usually in a users'
+ * calendar-homeset.
+ *
+ * It contains all the users' calendars, and can optionally contain a
+ * notifications collection, calendar subscriptions, a users' inbox, and a
+ * users' outbox.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class CalendarHome implements DAV\IExtendedCollection, DAVACL\IACL {
+
+    /**
+     * CalDAV backend
+     *
+     * @var Sabre\CalDAV\Backend\BackendInterface
+     */
+    protected $caldavBackend;
+
+    /**
+     * Principal information
+     *
+     * @var array
+     */
+    protected $principalInfo;
+
+    /**
+     * Constructor
+     *
+     * @param Backend\BackendInterface $caldavBackend
+     * @param mixed $userUri
+     */
+    function __construct(Backend\BackendInterface $caldavBackend, $principalInfo) {
+
+        $this->caldavBackend = $caldavBackend;
+        $this->principalInfo = $principalInfo;
+
+    }
+
+    /**
+     * Returns the name of this object
+     *
+     * @return string
+     */
+    function getName() {
+
+        list(, $name) = URLUtil::splitPath($this->principalInfo['uri']);
+        return $name;
+
+    }
+
+    /**
+     * Updates the name of this object
+     *
+     * @param string $name
+     * @return void
+     */
+    function setName($name) {
+
+        throw new DAV\Exception\Forbidden();
+
+    }
+
+    /**
+     * Deletes this object
+     *
+     * @return void
+     */
+    function delete() {
+
+        throw new DAV\Exception\Forbidden();
+
+    }
+
+    /**
+     * Returns the last modification date
+     *
+     * @return int
+     */
+    function getLastModified() {
+
+        return null;
+
+    }
+
+    /**
+     * Creates a new file under this object.
+     *
+     * This is currently not allowed
+     *
+     * @param string $filename
+     * @param resource $data
+     * @return void
+     */
+    function createFile($filename, $data = null) {
+
+        throw new DAV\Exception\MethodNotAllowed('Creating new files in this collection is not supported');
+
+    }
+
+    /**
+     * Creates a new directory under this object.
+     *
+     * This is currently not allowed.
+     *
+     * @param string $filename
+     * @return void
+     */
+    function createDirectory($filename) {
+
+        throw new DAV\Exception\MethodNotAllowed('Creating new collections in this collection is not supported');
+
+    }
+
+    /**
+     * Returns a single calendar, by name
+     *
+     * @param string $name
+     * @return Calendar
+     */
+    function getChild($name) {
+
+        // Special nodes
+        if ($name === 'inbox' && $this->caldavBackend instanceof Backend\SchedulingSupport) {
+            return new Schedule\Inbox($this->caldavBackend, $this->principalInfo['uri']);
+        }
+        if ($name === 'outbox' && $this->caldavBackend instanceof Backend\SchedulingSupport) {
+            return new Schedule\Outbox($this->principalInfo['uri']);
+        }
+        if ($name === 'notifications' && $this->caldavBackend instanceof Backend\NotificationSupport) {
+            return new Notifications\Collection($this->caldavBackend, $this->principalInfo['uri']);
+        }
+
+        // Calendars
+        foreach ($this->caldavBackend->getCalendarsForUser($this->principalInfo['uri']) as $calendar) {
+            if ($calendar['uri'] === $name) {
+                if ($this->caldavBackend instanceof Backend\SharingSupport) {
+                    if (isset($calendar['{http://calendarserver.org/ns/}shared-url'])) {
+                        return new SharedCalendar($this->caldavBackend, $calendar);
+                    } else {
+                        return new ShareableCalendar($this->caldavBackend, $calendar);
+                    }
+                } else {
+                    return new Calendar($this->caldavBackend, $calendar);
+                }
+            }
+        }
+
+        if ($this->caldavBackend instanceof Backend\SubscriptionSupport) {
+            foreach ($this->caldavBackend->getSubscriptionsForUser($this->principalInfo['uri']) as $subscription) {
+                if ($subscription['uri'] === $name) {
+                    return new Subscriptions\Subscription($this->caldavBackend, $subscription);
+                }
+            }
+
+        }
+
+        throw new NotFound('Node with name \'' . $name . '\' could not be found');
+
+    }
+
+    /**
+     * Checks if a calendar exists.
+     *
+     * @param string $name
+     * @return bool
+     */
+    function childExists($name) {
+
+        try {
+            return !!$this->getChild($name);
+        } catch (NotFound $e) {
+            return false;
+        }
+
+    }
+
+    /**
+     * Returns a list of calendars
+     *
+     * @return array
+     */
+    function getChildren() {
+
+        $calendars = $this->caldavBackend->getCalendarsForUser($this->principalInfo['uri']);
+        $objs = [];
+        foreach ($calendars as $calendar) {
+            if ($this->caldavBackend instanceof Backend\SharingSupport) {
+                if (isset($calendar['{http://calendarserver.org/ns/}shared-url'])) {
+                    $objs[] = new SharedCalendar($this->caldavBackend, $calendar);
+                } else {
+                    $objs[] = new ShareableCalendar($this->caldavBackend, $calendar);
+                }
+            } else {
+                $objs[] = new Calendar($this->caldavBackend, $calendar);
+            }
+        }
+
+        if ($this->caldavBackend instanceof Backend\SchedulingSupport) {
+            $objs[] = new Schedule\Inbox($this->caldavBackend, $this->principalInfo['uri']);
+            $objs[] = new Schedule\Outbox($this->principalInfo['uri']);
+        }
+
+        // We're adding a notifications node, if it's supported by the backend.
+        if ($this->caldavBackend instanceof Backend\NotificationSupport) {
+            $objs[] = new Notifications\Collection($this->caldavBackend, $this->principalInfo['uri']);
+        }
+
+        // If the backend supports subscriptions, we'll add those as well,
+        if ($this->caldavBackend instanceof Backend\SubscriptionSupport) {
+            foreach ($this->caldavBackend->getSubscriptionsForUser($this->principalInfo['uri']) as $subscription) {
+                $objs[] = new Subscriptions\Subscription($this->caldavBackend, $subscription);
+            }
+        }
+
+        return $objs;
+
+    }
+
+    /**
+     * Creates a new calendar or subscription.
+     *
+     * @param string $name
+     * @param MkCol $mkCol
+     * @throws DAV\Exception\InvalidResourceType
+     * @return void
+     */
+    function createExtendedCollection($name, MkCol $mkCol) {
+
+        $isCalendar = false;
+        $isSubscription = false;
+        foreach ($mkCol->getResourceType() as $rt) {
+            switch ($rt) {
+                case '{DAV:}collection' :
+                case '{http://calendarserver.org/ns/}shared-owner' :
+                    // ignore
+                    break;
+                case '{urn:ietf:params:xml:ns:caldav}calendar' :
+                    $isCalendar = true;
+                    break;
+                case '{http://calendarserver.org/ns/}subscribed' :
+                    $isSubscription = true;
+                    break;
+                default :
+                    throw new DAV\Exception\InvalidResourceType('Unknown resourceType: ' . $rt);
+            }
+        }
+
+        $properties = $mkCol->getRemainingValues();
+        $mkCol->setRemainingResultCode(201);
+
+        if ($isSubscription) {
+            if (!$this->caldavBackend instanceof Backend\SubscriptionSupport) {
+                throw new DAV\Exception\InvalidResourceType('This backend does not support subscriptions');
+            }
+            $this->caldavBackend->createSubscription($this->principalInfo['uri'], $name, $properties);
+
+        } elseif ($isCalendar) {
+            $this->caldavBackend->createCalendar($this->principalInfo['uri'], $name, $properties);
+
+        } else {
+            throw new DAV\Exception\InvalidResourceType('You can only create calendars and subscriptions in this collection');
+
+        }
+
+    }
+
+    /**
+     * Returns the owner principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getOwner() {
+
+        return $this->principalInfo['uri'];
+
+    }
+
+    /**
+     * Returns a group principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getGroup() {
+
+        return null;
+
+    }
+
+    /**
+     * Returns a list of ACE's for this node.
+     *
+     * Each ACE has the following properties:
+     *   * 'privilege', a string such as {DAV:}read or {DAV:}write. These are
+     *     currently the only supported privileges
+     *   * 'principal', a url to the principal who owns the node
+     *   * 'protected' (optional), indicating that this ACE is not allowed to
+     *      be updated.
+     *
+     * @return array
+     */
+    function getACL() {
+
+        return [
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->principalInfo['uri'],
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}write',
+                'principal' => $this->principalInfo['uri'],
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->principalInfo['uri'] . '/calendar-proxy-write',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}write',
+                'principal' => $this->principalInfo['uri'] . '/calendar-proxy-write',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->principalInfo['uri'] . '/calendar-proxy-read',
+                'protected' => true,
+            ],
+
+        ];
+
+    }
+
+    /**
+     * Updates the ACL
+     *
+     * This method will receive a list of new ACE's.
+     *
+     * @param array $acl
+     * @return void
+     */
+    function setACL(array $acl) {
+
+        throw new DAV\Exception\MethodNotAllowed('Changing ACL is not yet supported');
+
+    }
+
+    /**
+     * Returns the list of supported privileges for this node.
+     *
+     * The returned data structure is a list of nested privileges.
+     * See Sabre\DAVACL\Plugin::getDefaultSupportedPrivilegeSet for a simple
+     * standard structure.
+     *
+     * If null is returned from this method, the default privilege set is used,
+     * which is fine for most common usecases.
+     *
+     * @return array|null
+     */
+    function getSupportedPrivilegeSet() {
+
+        return null;
+
+    }
+
+    /**
+     * This method is called when a user replied to a request to share.
+     *
+     * This method should return the url of the newly created calendar if the
+     * share was accepted.
+     *
+     * @param string href The sharee who is replying (often a mailto: address)
+     * @param int status One of the SharingPlugin::STATUS_* constants
+     * @param string $calendarUri The url to the calendar thats being shared
+     * @param string $inReplyTo The unique id this message is a response to
+     * @param string $summary A description of the reply
+     * @return null|string
+     */
+    function shareReply($href, $status, $calendarUri, $inReplyTo, $summary = null) {
+
+        if (!$this->caldavBackend instanceof Backend\SharingSupport) {
+            throw new DAV\Exception\NotImplemented('Sharing support is not implemented by this backend.');
+        }
+
+        return $this->caldavBackend->shareReply($href, $status, $calendarUri, $inReplyTo, $summary);
+
+    }
+
+    /**
+     * Searches through all of a users calendars and calendar objects to find
+     * an object with a specific UID.
+     *
+     * This method should return the path to this object, relative to the
+     * calendar home, so this path usually only contains two parts:
+     *
+     * calendarpath/objectpath.ics
+     *
+     * If the uid is not found, return null.
+     *
+     * This method should only consider * objects that the principal owns, so
+     * any calendars owned by other principals that also appear in this
+     * collection should be ignored.
+     *
+     * @param string $uid
+     * @return string|null
+     */
+    function getCalendarObjectByUID($uid) {
+
+        return $this->caldavBackend->getCalendarObjectByUID($this->principalInfo['uri'], $uid);
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/CalendarObject.php b/vendor/sabre/dav/lib/CalDAV/CalendarObject.php
new file mode 100644
index 000000000..393ca4cbd
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/CalendarObject.php
@@ -0,0 +1,290 @@
+<?php
+
+namespace Sabre\CalDAV;
+
+/**
+ * The CalendarObject represents a single VEVENT or VTODO within a Calendar.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class CalendarObject extends \Sabre\DAV\File implements ICalendarObject, \Sabre\DAVACL\IACL {
+
+    /**
+     * Sabre\CalDAV\Backend\BackendInterface
+     *
+     * @var Sabre\CalDAV\Backend\AbstractBackend
+     */
+    protected $caldavBackend;
+
+    /**
+     * Array with information about this CalendarObject
+     *
+     * @var array
+     */
+    protected $objectData;
+
+    /**
+     * Array with information about the containing calendar
+     *
+     * @var array
+     */
+    protected $calendarInfo;
+
+    /**
+     * Constructor
+     *
+     * The following properties may be passed within $objectData:
+     *
+     *   * calendarid - This must refer to a calendarid from a caldavBackend
+     *   * uri - A unique uri. Only the 'basename' must be passed.
+     *   * calendardata (optional) - The iCalendar data
+     *   * etag - (optional) The etag for this object, MUST be encloded with
+     *            double-quotes.
+     *   * size - (optional) The size of the data in bytes.
+     *   * lastmodified - (optional) format as a unix timestamp.
+     *   * acl - (optional) Use this to override the default ACL for the node.
+     *
+     * @param Backend\BackendInterface $caldavBackend
+     * @param array $calendarInfo
+     * @param array $objectData
+     */
+    function __construct(Backend\BackendInterface $caldavBackend, array $calendarInfo, array $objectData) {
+
+        $this->caldavBackend = $caldavBackend;
+
+        if (!isset($objectData['uri'])) {
+            throw new \InvalidArgumentException('The objectData argument must contain an \'uri\' property');
+        }
+
+        $this->calendarInfo = $calendarInfo;
+        $this->objectData = $objectData;
+
+    }
+
+    /**
+     * Returns the uri for this object
+     *
+     * @return string
+     */
+    function getName() {
+
+        return $this->objectData['uri'];
+
+    }
+
+    /**
+     * Returns the ICalendar-formatted object
+     *
+     * @return string
+     */
+    function get() {
+
+        // Pre-populating the 'calendardata' is optional, if we don't have it
+        // already we fetch it from the backend.
+        if (!isset($this->objectData['calendardata'])) {
+            $this->objectData = $this->caldavBackend->getCalendarObject($this->calendarInfo['id'], $this->objectData['uri']);
+        }
+        return $this->objectData['calendardata'];
+
+    }
+
+    /**
+     * Updates the ICalendar-formatted object
+     *
+     * @param string|resource $calendarData
+     * @return string
+     */
+    function put($calendarData) {
+
+        if (is_resource($calendarData)) {
+            $calendarData = stream_get_contents($calendarData);
+        }
+        $etag = $this->caldavBackend->updateCalendarObject($this->calendarInfo['id'], $this->objectData['uri'], $calendarData);
+        $this->objectData['calendardata'] = $calendarData;
+        $this->objectData['etag'] = $etag;
+
+        return $etag;
+
+    }
+
+    /**
+     * Deletes the calendar object
+     *
+     * @return void
+     */
+    function delete() {
+
+        $this->caldavBackend->deleteCalendarObject($this->calendarInfo['id'], $this->objectData['uri']);
+
+    }
+
+    /**
+     * Returns the mime content-type
+     *
+     * @return string
+     */
+    function getContentType() {
+
+        $mime = 'text/calendar; charset=utf-8';
+        if (isset($this->objectData['component']) && $this->objectData['component']) {
+            $mime .= '; component=' . $this->objectData['component'];
+        }
+        return $mime;
+
+    }
+
+    /**
+     * Returns an ETag for this object.
+     *
+     * The ETag is an arbitrary string, but MUST be surrounded by double-quotes.
+     *
+     * @return string
+     */
+    function getETag() {
+
+        if (isset($this->objectData['etag'])) {
+            return $this->objectData['etag'];
+        } else {
+            return '"' . md5($this->get()) . '"';
+        }
+
+    }
+
+    /**
+     * Returns the last modification date as a unix timestamp
+     *
+     * @return int
+     */
+    function getLastModified() {
+
+        return $this->objectData['lastmodified'];
+
+    }
+
+    /**
+     * Returns the size of this object in bytes
+     *
+     * @return int
+     */
+    function getSize() {
+
+        if (array_key_exists('size', $this->objectData)) {
+            return $this->objectData['size'];
+        } else {
+            return strlen($this->get());
+        }
+
+    }
+
+    /**
+     * Returns the owner principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getOwner() {
+
+        return $this->calendarInfo['principaluri'];
+
+    }
+
+    /**
+     * Returns a group principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getGroup() {
+
+        return null;
+
+    }
+
+    /**
+     * Returns a list of ACE's for this node.
+     *
+     * Each ACE has the following properties:
+     *   * 'privilege', a string such as {DAV:}read or {DAV:}write. These are
+     *     currently the only supported privileges
+     *   * 'principal', a url to the principal who owns the node
+     *   * 'protected' (optional), indicating that this ACE is not allowed to
+     *      be updated.
+     *
+     * @return array
+     */
+    function getACL() {
+
+        // An alternative acl may be specified in the object data.
+        if (isset($this->objectData['acl'])) {
+            return $this->objectData['acl'];
+        }
+
+        // The default ACL
+        return [
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->calendarInfo['principaluri'],
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}write',
+                'principal' => $this->calendarInfo['principaluri'],
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->calendarInfo['principaluri'] . '/calendar-proxy-write',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}write',
+                'principal' => $this->calendarInfo['principaluri'] . '/calendar-proxy-write',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->calendarInfo['principaluri'] . '/calendar-proxy-read',
+                'protected' => true,
+            ],
+
+        ];
+
+    }
+
+    /**
+     * Updates the ACL
+     *
+     * This method will receive a list of new ACE's.
+     *
+     * @param array $acl
+     * @return void
+     */
+    function setACL(array $acl) {
+
+        throw new \Sabre\DAV\Exception\MethodNotAllowed('Changing ACL is not yet supported');
+
+    }
+
+    /**
+     * Returns the list of supported privileges for this node.
+     *
+     * The returned data structure is a list of nested privileges.
+     * See \Sabre\DAVACL\Plugin::getDefaultSupportedPrivilegeSet for a simple
+     * standard structure.
+     *
+     * If null is returned from this method, the default privilege set is used,
+     * which is fine for most common usecases.
+     *
+     * @return array|null
+     */
+    function getSupportedPrivilegeSet() {
+
+        return null;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/CalendarQueryValidator.php b/vendor/sabre/dav/lib/CalDAV/CalendarQueryValidator.php
new file mode 100644
index 000000000..f3c7524d2
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/CalendarQueryValidator.php
@@ -0,0 +1,375 @@
+<?php
+
+namespace Sabre\CalDAV;
+
+use Sabre\VObject;
+use DateTime;
+
+/**
+ * CalendarQuery Validator
+ *
+ * This class is responsible for checking if an iCalendar object matches a set
+ * of filters. The main function to do this is 'validate'.
+ *
+ * This is used to determine which icalendar objects should be returned for a
+ * calendar-query REPORT request.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class CalendarQueryValidator {
+
+    /**
+     * Verify if a list of filters applies to the calendar data object
+     *
+     * The list of filters must be formatted as parsed by \Sabre\CalDAV\CalendarQueryParser
+     *
+     * @param VObject\Component $vObject
+     * @param array $filters
+     * @return bool
+     */
+    function validate(VObject\Component\VCalendar $vObject, array $filters) {
+
+        // The top level object is always a component filter.
+        // We'll parse it manually, as it's pretty simple.
+        if ($vObject->name !== $filters['name']) {
+            return false;
+        }
+
+        return
+            $this->validateCompFilters($vObject, $filters['comp-filters']) &&
+            $this->validatePropFilters($vObject, $filters['prop-filters']);
+
+
+    }
+
+    /**
+     * This method checks the validity of comp-filters.
+     *
+     * A list of comp-filters needs to be specified. Also the parent of the
+     * component we're checking should be specified, not the component to check
+     * itself.
+     *
+     * @param VObject\Component $parent
+     * @param array $filters
+     * @return bool
+     */
+    protected function validateCompFilters(VObject\Component $parent, array $filters) {
+
+        foreach ($filters as $filter) {
+
+            $isDefined = isset($parent->{$filter['name']});
+
+            if ($filter['is-not-defined']) {
+
+                if ($isDefined) {
+                    return false;
+                } else {
+                    continue;
+                }
+
+            }
+            if (!$isDefined) {
+                return false;
+            }
+
+            if ($filter['time-range']) {
+                foreach ($parent->{$filter['name']} as $subComponent) {
+                    if ($this->validateTimeRange($subComponent, $filter['time-range']['start'], $filter['time-range']['end'])) {
+                        continue 2;
+                    }
+                }
+                return false;
+            }
+
+            if (!$filter['comp-filters'] && !$filter['prop-filters']) {
+                continue;
+            }
+
+            // If there are sub-filters, we need to find at least one component
+            // for which the subfilters hold true.
+            foreach ($parent->{$filter['name']} as $subComponent) {
+
+                if (
+                    $this->validateCompFilters($subComponent, $filter['comp-filters']) &&
+                    $this->validatePropFilters($subComponent, $filter['prop-filters'])) {
+                        // We had a match, so this comp-filter succeeds
+                        continue 2;
+                }
+
+            }
+
+            // If we got here it means there were sub-comp-filters or
+            // sub-prop-filters and there was no match. This means this filter
+            // needs to return false.
+            return false;
+
+        }
+
+        // If we got here it means we got through all comp-filters alive so the
+        // filters were all true.
+        return true;
+
+    }
+
+    /**
+     * This method checks the validity of prop-filters.
+     *
+     * A list of prop-filters needs to be specified. Also the parent of the
+     * property we're checking should be specified, not the property to check
+     * itself.
+     *
+     * @param VObject\Component $parent
+     * @param array $filters
+     * @return bool
+     */
+    protected function validatePropFilters(VObject\Component $parent, array $filters) {
+
+        foreach ($filters as $filter) {
+
+            $isDefined = isset($parent->{$filter['name']});
+
+            if ($filter['is-not-defined']) {
+
+                if ($isDefined) {
+                    return false;
+                } else {
+                    continue;
+                }
+
+            }
+            if (!$isDefined) {
+                return false;
+            }
+
+            if ($filter['time-range']) {
+                foreach ($parent->{$filter['name']} as $subComponent) {
+                    if ($this->validateTimeRange($subComponent, $filter['time-range']['start'], $filter['time-range']['end'])) {
+                        continue 2;
+                    }
+                }
+                return false;
+            }
+
+            if (!$filter['param-filters'] && !$filter['text-match']) {
+                continue;
+            }
+
+            // If there are sub-filters, we need to find at least one property
+            // for which the subfilters hold true.
+            foreach ($parent->{$filter['name']} as $subComponent) {
+
+                if (
+                    $this->validateParamFilters($subComponent, $filter['param-filters']) &&
+                    (!$filter['text-match'] || $this->validateTextMatch($subComponent, $filter['text-match']))
+                ) {
+                    // We had a match, so this prop-filter succeeds
+                    continue 2;
+                }
+
+            }
+
+            // If we got here it means there were sub-param-filters or
+            // text-match filters and there was no match. This means the
+            // filter needs to return false.
+            return false;
+
+        }
+
+        // If we got here it means we got through all prop-filters alive so the
+        // filters were all true.
+        return true;
+
+    }
+
+    /**
+     * This method checks the validity of param-filters.
+     *
+     * A list of param-filters needs to be specified. Also the parent of the
+     * parameter we're checking should be specified, not the parameter to check
+     * itself.
+     *
+     * @param VObject\Property $parent
+     * @param array $filters
+     * @return bool
+     */
+    protected function validateParamFilters(VObject\Property $parent, array $filters) {
+
+        foreach ($filters as $filter) {
+
+            $isDefined = isset($parent[$filter['name']]);
+
+            if ($filter['is-not-defined']) {
+
+                if ($isDefined) {
+                    return false;
+                } else {
+                    continue;
+                }
+
+            }
+            if (!$isDefined) {
+                return false;
+            }
+
+            if (!$filter['text-match']) {
+                continue;
+            }
+
+            // If there are sub-filters, we need to find at least one parameter
+            // for which the subfilters hold true.
+            foreach ($parent[$filter['name']]->getParts() as $paramPart) {
+
+                if ($this->validateTextMatch($paramPart, $filter['text-match'])) {
+                    // We had a match, so this param-filter succeeds
+                    continue 2;
+                }
+
+            }
+
+            // If we got here it means there was a text-match filter and there
+            // were no matches. This means the filter needs to return false.
+            return false;
+
+        }
+
+        // If we got here it means we got through all param-filters alive so the
+        // filters were all true.
+        return true;
+
+    }
+
+    /**
+     * This method checks the validity of a text-match.
+     *
+     * A single text-match should be specified as well as the specific property
+     * or parameter we need to validate.
+     *
+     * @param VObject\Node|string $check Value to check against.
+     * @param array $textMatch
+     * @return bool
+     */
+    protected function validateTextMatch($check, array $textMatch) {
+
+        if ($check instanceof VObject\Node) {
+            $check = $check->getValue();
+        }
+
+        $isMatching = \Sabre\DAV\StringUtil::textMatch($check, $textMatch['value'], $textMatch['collation']);
+
+        return ($textMatch['negate-condition'] xor $isMatching);
+
+    }
+
+    /**
+     * Validates if a component matches the given time range.
+     *
+     * This is all based on the rules specified in rfc4791, which are quite
+     * complex.
+     *
+     * @param VObject\Node $component
+     * @param DateTime $start
+     * @param DateTime $end
+     * @return bool
+     */
+    protected function validateTimeRange(VObject\Node $component, $start, $end) {
+
+        if (is_null($start)) {
+            $start = new DateTime('1900-01-01');
+        }
+        if (is_null($end)) {
+            $end = new DateTime('3000-01-01');
+        }
+
+        switch ($component->name) {
+
+            case 'VEVENT' :
+            case 'VTODO' :
+            case 'VJOURNAL' :
+
+                return $component->isInTimeRange($start, $end);
+
+            case 'VALARM' :
+
+                // If the valarm is wrapped in a recurring event, we need to
+                // expand the recursions, and validate each.
+                //
+                // Our datamodel doesn't easily allow us to do this straight
+                // in the VALARM component code, so this is a hack, and an
+                // expensive one too.
+                if ($component->parent->name === 'VEVENT' && $component->parent->RRULE) {
+
+                    // Fire up the iterator!
+                    $it = new VObject\Recur\EventIterator($component->parent->parent, (string)$component->parent->UID);
+                    while ($it->valid()) {
+                        $expandedEvent = $it->getEventObject();
+
+                        // We need to check from these expanded alarms, which
+                        // one is the first to trigger. Based on this, we can
+                        // determine if we can 'give up' expanding events.
+                        $firstAlarm = null;
+                        if ($expandedEvent->VALARM !== null) {
+                            foreach ($expandedEvent->VALARM as $expandedAlarm) {
+
+                                $effectiveTrigger = $expandedAlarm->getEffectiveTriggerTime();
+                                if ($expandedAlarm->isInTimeRange($start, $end)) {
+                                    return true;
+                                }
+
+                                if ((string)$expandedAlarm->TRIGGER['VALUE'] === 'DATE-TIME') {
+                                    // This is an alarm with a non-relative trigger
+                                    // time, likely created by a buggy client. The
+                                    // implication is that every alarm in this
+                                    // recurring event trigger at the exact same
+                                    // time. It doesn't make sense to traverse
+                                    // further.
+                                } else {
+                                    // We store the first alarm as a means to
+                                    // figure out when we can stop traversing.
+                                    if (!$firstAlarm || $effectiveTrigger < $firstAlarm) {
+                                        $firstAlarm = $effectiveTrigger;
+                                    }
+                                }
+                            }
+                        }
+                        if (is_null($firstAlarm)) {
+                            // No alarm was found.
+                            //
+                            // Or technically: No alarm that will change for
+                            // every instance of the recurrence was found,
+                            // which means we can assume there was no match.
+                            return false;
+                        }
+                        if ($firstAlarm > $end) {
+                            return false;
+                        }
+                        $it->next();
+                    }
+                    return false;
+                } else {
+                    return $component->isInTimeRange($start, $end);
+                }
+
+            case 'VFREEBUSY' :
+                throw new \Sabre\DAV\Exception\NotImplemented('time-range filters are currently not supported on ' . $component->name . ' components');
+
+            case 'COMPLETED' :
+            case 'CREATED' :
+            case 'DTEND' :
+            case 'DTSTAMP' :
+            case 'DTSTART' :
+            case 'DUE' :
+            case 'LAST-MODIFIED' :
+                return ($start <= $component->getDateTime() && $end >= $component->getDateTime());
+
+
+
+            default :
+                throw new \Sabre\DAV\Exception\BadRequest('You cannot create a time-range filter on a ' . $component->name . ' component');
+
+        }
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/CalendarRoot.php b/vendor/sabre/dav/lib/CalDAV/CalendarRoot.php
new file mode 100644
index 000000000..0ac50e41d
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/CalendarRoot.php
@@ -0,0 +1,80 @@
+<?php
+
+namespace Sabre\CalDAV;
+
+use Sabre\DAVACL\PrincipalBackend;
+
+/**
+ * Calendars collection
+ *
+ * This object is responsible for generating a list of calendar-homes for each
+ * user.
+ *
+ * This is the top-most node for the calendars tree. In most servers this class
+ * represents the "/calendars" path.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class CalendarRoot extends \Sabre\DAVACL\AbstractPrincipalCollection {
+
+    /**
+     * CalDAV backend
+     *
+     * @var Sabre\CalDAV\Backend\BackendInterface
+     */
+    protected $caldavBackend;
+
+    /**
+     * Constructor
+     *
+     * This constructor needs both an authentication and a caldav backend.
+     *
+     * By default this class will show a list of calendar collections for
+     * principals in the 'principals' collection. If your main principals are
+     * actually located in a different path, use the $principalPrefix argument
+     * to override this.
+     *
+     * @param PrincipalBackend\BackendInterface $principalBackend
+     * @param Backend\BackendInterface $caldavBackend
+     * @param string $principalPrefix
+     */
+    function __construct(PrincipalBackend\BackendInterface $principalBackend, Backend\BackendInterface $caldavBackend, $principalPrefix = 'principals') {
+
+        parent::__construct($principalBackend, $principalPrefix);
+        $this->caldavBackend = $caldavBackend;
+
+    }
+
+    /**
+     * Returns the nodename
+     *
+     * We're overriding this, because the default will be the 'principalPrefix',
+     * and we want it to be Sabre\CalDAV\Plugin::CALENDAR_ROOT
+     *
+     * @return string
+     */
+    function getName() {
+
+        return Plugin::CALENDAR_ROOT;
+
+    }
+
+    /**
+     * This method returns a node for a principal.
+     *
+     * The passed array contains principal information, and is guaranteed to
+     * at least contain a uri item. Other properties may or may not be
+     * supplied by the authentication backend.
+     *
+     * @param array $principal
+     * @return \Sabre\DAV\INode
+     */
+    function getChildForPrincipal(array $principal) {
+
+        return new CalendarHome($this->caldavBackend, $principal);
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Exception/InvalidComponentType.php b/vendor/sabre/dav/lib/CalDAV/Exception/InvalidComponentType.php
new file mode 100644
index 000000000..5ce8a93f5
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Exception/InvalidComponentType.php
@@ -0,0 +1,35 @@
+<?php
+
+namespace Sabre\CalDAV\Exception;
+
+use Sabre\DAV;
+use Sabre\CalDAV;
+
+/**
+ * InvalidComponentType
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class InvalidComponentType extends DAV\Exception\Forbidden {
+
+    /**
+     * Adds in extra information in the xml response.
+     *
+     * This method adds the {CALDAV:}supported-calendar-component as defined in rfc4791
+     *
+     * @param DAV\Server $server
+     * @param \DOMElement $errorNode
+     * @return void
+     */
+    function serialize(DAV\Server $server, \DOMElement $errorNode) {
+
+        $doc = $errorNode->ownerDocument;
+
+        $np = $doc->createElementNS(CalDAV\Plugin::NS_CALDAV, 'cal:supported-calendar-component');
+        $errorNode->appendChild($np);
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/ICSExportPlugin.php b/vendor/sabre/dav/lib/CalDAV/ICSExportPlugin.php
new file mode 100644
index 000000000..8c296d50f
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/ICSExportPlugin.php
@@ -0,0 +1,366 @@
+<?php
+
+namespace Sabre\CalDAV;
+
+use DateTimeZone;
+use Sabre\DAV;
+use Sabre\VObject;
+use Sabre\HTTP\RequestInterface;
+use Sabre\HTTP\ResponseInterface;
+use Sabre\DAV\Exception\BadRequest;
+use DateTime;
+
+/**
+ * ICS Exporter
+ *
+ * This plugin adds the ability to export entire calendars as .ics files.
+ * This is useful for clients that don't support CalDAV yet. They often do
+ * support ics files.
+ *
+ * To use this, point a http client to a caldav calendar, and add ?expand to
+ * the url.
+ *
+ * Further options that can be added to the url:
+ *   start=123456789 - Only return events after the given unix timestamp
+ *   end=123245679   - Only return events from before the given unix timestamp
+ *   expand=1        - Strip timezone information and expand recurring events.
+ *                     If you'd like to expand, you _must_ also specify start
+ *                     and end.
+ *
+ * By default this plugin returns data in the text/calendar format (iCalendar
+ * 2.0). If you'd like to receive jCal data instead, you can use an Accept
+ * header:
+ *
+ * Accept: application/calendar+json
+ *
+ * Alternatively, you can also specify this in the url using
+ * accept=application/calendar+json, or accept=jcal for short. If the url
+ * parameter and Accept header is specified, the url parameter wins.
+ *
+ * Note that specifying a start or end data implies that only events will be
+ * returned. VTODO and VJOURNAL will be stripped.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class ICSExportPlugin extends DAV\ServerPlugin {
+
+    /**
+     * Reference to Server class
+     *
+     * @var \Sabre\DAV\Server
+     */
+    protected $server;
+
+    /**
+     * Initializes the plugin and registers event handlers
+     *
+     * @param \Sabre\DAV\Server $server
+     * @return void
+     */
+    function initialize(DAV\Server $server) {
+
+        $this->server = $server;
+        $server->on('method:GET', [$this, 'httpGet'], 90);
+        $server->on('browserButtonActions', function($path, $node, &$actions) {
+            if ($node instanceof ICalendar) {
+                $actions .= '<a href="' . htmlspecialchars($path, ENT_QUOTES, 'UTF-8') . '?export"><span class="oi" data-glyph="calendar"></span></a>';
+            }
+        });
+
+    }
+
+    /**
+     * Intercepts GET requests on calendar urls ending with ?export.
+     *
+     * @param RequestInterface $request
+     * @param ResponseInterface $response
+     * @return bool
+     */
+    function httpGet(RequestInterface $request, ResponseInterface $response) {
+
+        $queryParams = $request->getQueryParameters();
+        if (!array_key_exists('export', $queryParams)) return;
+
+        $path = $request->getPath();
+
+        $node = $this->server->getProperties($path, [
+            '{DAV:}resourcetype',
+            '{DAV:}displayname',
+            '{http://sabredav.org/ns}sync-token',
+            '{DAV:}sync-token',
+            '{http://apple.com/ns/ical/}calendar-color',
+        ]);
+
+        if (!isset($node['{DAV:}resourcetype']) || !$node['{DAV:}resourcetype']->is('{' . Plugin::NS_CALDAV . '}calendar')) {
+            return;
+        }
+        // Marking the transactionType, for logging purposes.
+        $this->server->transactionType = 'get-calendar-export';
+
+        $properties = $node;
+
+        $start = null;
+        $end = null;
+        $expand = false;
+        $componentType = false;
+        if (isset($queryParams['start'])) {
+            if (!ctype_digit($queryParams['start'])) {
+                throw new BadRequest('The start= parameter must contain a unix timestamp');
+            }
+            $start = DateTime::createFromFormat('U', $queryParams['start']);
+        }
+        if (isset($queryParams['end'])) {
+            if (!ctype_digit($queryParams['end'])) {
+                throw new BadRequest('The end= parameter must contain a unix timestamp');
+            }
+            $end = DateTime::createFromFormat('U', $queryParams['end']);
+        }
+        if (isset($queryParams['expand']) && !!$queryParams['expand']) {
+            if (!$start || !$end) {
+                throw new BadRequest('If you\'d like to expand recurrences, you must specify both a start= and end= parameter.');
+            }
+            $expand = true;
+            $componentType = 'VEVENT';
+        }
+        if (isset($queryParams['componentType'])) {
+            if (!in_array($queryParams['componentType'], ['VEVENT', 'VTODO', 'VJOURNAL'])) {
+                throw new BadRequest('You are not allowed to search for components of type: ' . $queryParams['componentType'] . ' here');
+            }
+            $componentType = $queryParams['componentType'];
+        }
+
+        $format = \Sabre\HTTP\Util::Negotiate(
+            $request->getHeader('Accept'),
+            [
+                'text/calendar',
+                'application/calendar+json',
+            ]
+        );
+
+        if (isset($queryParams['accept'])) {
+            if ($queryParams['accept'] === 'application/calendar+json' || $queryParams['accept'] === 'jcal') {
+                $format = 'application/calendar+json';
+            }
+        }
+        if (!$format) {
+            $format = 'text/calendar';
+        }
+
+        $this->generateResponse($path, $start, $end, $expand, $componentType, $format, $properties, $response);
+
+        // Returning false to break the event chain
+        return false;
+
+    }
+
+    /**
+     * This method is responsible for generating the actual, full response.
+     *
+     * @param string $path
+     * @param DateTime|null $start
+     * @param DateTime|null $end
+     * @param bool $expand
+     * @param string $componentType
+     * @param string $format
+     * @param array $properties
+     * @param ResponseInterface $response
+     */
+    protected function generateResponse($path, $start, $end, $expand, $componentType, $format, $properties, ResponseInterface $response) {
+
+        $calDataProp = '{' . Plugin::NS_CALDAV . '}calendar-data';
+
+        $blobs = [];
+        if ($start || $end || $componentType) {
+
+            // If there was a start or end filter, we need to enlist
+            // calendarQuery for speed.
+            $calendarNode = $this->server->tree->getNodeForPath($path);
+            $queryResult = $calendarNode->calendarQuery([
+                'name'         => 'VCALENDAR',
+                'comp-filters' => [
+                    [
+                        'name'           => $componentType,
+                        'comp-filters'   => [],
+                        'prop-filters'   => [],
+                        'is-not-defined' => false,
+                        'time-range'     => [
+                            'start' => $start,
+                            'end'   => $end,
+                        ],
+                    ],
+                ],
+                'prop-filters'   => [],
+                'is-not-defined' => false,
+                'time-range'     => null,
+            ]);
+
+            // queryResult is just a list of base urls. We need to prefix the
+            // calendar path.
+            $queryResult = array_map(
+                function($item) use ($path) {
+                    return $path . '/' . $item;
+                },
+                $queryResult
+            );
+            $nodes = $this->server->getPropertiesForMultiplePaths($queryResult, [$calDataProp]);
+            unset($queryResult);
+
+        } else {
+            $nodes = $this->server->getPropertiesForPath($path, [$calDataProp], 1);
+        }
+
+        // Flattening the arrays
+        foreach ($nodes as $node) {
+            if (isset($node[200][$calDataProp])) {
+                $blobs[$node['href']] = $node[200][$calDataProp];
+            }
+        }
+        unset($nodes);
+
+        $mergedCalendar = $this->mergeObjects(
+            $properties,
+            $blobs
+        );
+
+        if ($expand) {
+            $calendarTimeZone = null;
+            // We're expanding, and for that we need to figure out the
+            // calendar's timezone.
+            $tzProp = '{' . Plugin::NS_CALDAV . '}calendar-timezone';
+            $tzResult = $this->server->getProperties($path, [$tzProp]);
+            if (isset($tzResult[$tzProp])) {
+                // This property contains a VCALENDAR with a single
+                // VTIMEZONE.
+                $vtimezoneObj = VObject\Reader::read($tzResult[$tzProp]);
+                $calendarTimeZone = $vtimezoneObj->VTIMEZONE->getTimeZone();
+                // Destroy circular references to PHP will GC the object.
+                $vtimezoneObj->destroy();
+                unset($vtimezoneObj);
+            } else {
+                // Defaulting to UTC.
+                $calendarTimeZone = new DateTimeZone('UTC');
+            }
+
+            $mergedCalendar = $mergedCalendar->expand($start, $end, $calendarTimeZone);
+        }
+
+        $response->setHeader('Content-Type', $format);
+
+        switch ($format) {
+            case 'text/calendar' :
+                $mergedCalendar = $mergedCalendar->serialize();
+                break;
+            case 'application/calendar+json' :
+                $mergedCalendar = json_encode($mergedCalendar->jsonSerialize());
+                break;
+        }
+
+        $response->setStatus(200);
+        $response->setBody($mergedCalendar);
+
+    }
+
+    /**
+     * Merges all calendar objects, and builds one big iCalendar blob.
+     *
+     * @param array $properties Some CalDAV properties
+     * @param array $inputObjects
+     * @return VObject\Component\VCalendar
+     */
+    function mergeObjects(array $properties, array $inputObjects) {
+
+        $calendar = new VObject\Component\VCalendar();
+        $calendar->version = '2.0';
+        if (DAV\Server::$exposeVersion) {
+            $calendar->prodid = '-//SabreDAV//SabreDAV ' . DAV\Version::VERSION . '//EN';
+        } else {
+            $calendar->prodid = '-//SabreDAV//SabreDAV//EN';
+        }
+        if (isset($properties['{DAV:}displayname'])) {
+            $calendar->{'X-WR-CALNAME'} = $properties['{DAV:}displayname'];
+        }
+        if (isset($properties['{http://apple.com/ns/ical/}calendar-color'])) {
+            $calendar->{'X-APPLE-CALENDAR-COLOR'} = $properties['{http://apple.com/ns/ical/}calendar-color'];
+        }
+
+        $collectedTimezones = [];
+
+        $timezones = [];
+        $objects = [];
+
+        foreach ($inputObjects as $href => $inputObject) {
+
+            $nodeComp = VObject\Reader::read($inputObject);
+
+            foreach ($nodeComp->children() as $child) {
+
+                switch ($child->name) {
+                    case 'VEVENT' :
+                    case 'VTODO' :
+                    case 'VJOURNAL' :
+                        $objects[] = clone $child;
+                        break;
+
+                    // VTIMEZONE is special, because we need to filter out the duplicates
+                    case 'VTIMEZONE' :
+                        // Naively just checking tzid.
+                        if (in_array((string)$child->TZID, $collectedTimezones)) continue;
+
+                        $timezones[] = clone $child;
+                        $collectedTimezones[] = $child->TZID;
+                        break;
+
+                }
+
+            }
+            // Destroy circular references to PHP will GC the object.
+            $nodeComp->destroy();
+            unset($nodeComp);
+
+        }
+
+        foreach ($timezones as $tz) $calendar->add($tz);
+        foreach ($objects as $obj) $calendar->add($obj);
+
+        return $calendar;
+
+    }
+
+    /**
+     * Returns a plugin name.
+     *
+     * Using this name other plugins will be able to access other plugins
+     * using \Sabre\DAV\Server::getPlugin
+     *
+     * @return string
+     */
+    function getPluginName() {
+
+        return 'ics-export';
+
+    }
+
+    /**
+     * Returns a bunch of meta-data about the plugin.
+     *
+     * Providing this information is optional, and is mainly displayed by the
+     * Browser plugin.
+     *
+     * The description key in the returned array may contain html and will not
+     * be sanitized.
+     *
+     * @return array
+     */
+    function getPluginInfo() {
+
+        return [
+            'name'        => $this->getPluginName(),
+            'description' => 'Adds the ability to export CalDAV calendars as a single iCalendar file.',
+            'link'        => 'http://sabre.io/dav/ics-export-plugin/',
+        ];
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/ICalendar.php b/vendor/sabre/dav/lib/CalDAV/ICalendar.php
new file mode 100644
index 000000000..7cf4b1256
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/ICalendar.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace Sabre\CalDAV;
+
+use Sabre\DAVACL;
+
+/**
+ * Calendar interface
+ *
+ * Implement this interface to allow a node to be recognized as an calendar.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface ICalendar extends ICalendarObjectContainer, DAVACL\IACL {
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/ICalendarObject.php b/vendor/sabre/dav/lib/CalDAV/ICalendarObject.php
new file mode 100644
index 000000000..b3a767b74
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/ICalendarObject.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace Sabre\CalDAV;
+
+use Sabre\DAV;
+
+/**
+ * CalendarObject interface
+ *
+ * Extend the ICalendarObject interface to allow your custom nodes to be picked up as
+ * CalendarObjects.
+ *
+ * Calendar objects are resources such as Events, Todo's or Journals.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface ICalendarObject extends DAV\IFile {
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/ICalendarObjectContainer.php b/vendor/sabre/dav/lib/CalDAV/ICalendarObjectContainer.php
new file mode 100644
index 000000000..0308b8a55
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/ICalendarObjectContainer.php
@@ -0,0 +1,39 @@
+<?php
+
+namespace Sabre\CalDAV;
+
+/**
+ * This interface represents a node that may contain calendar objects.
+ *
+ * This is the shared parent for both the Inbox collection and calendars
+ * resources.
+ *
+ * In most cases you will likely want to look at ICalendar instead of this
+ * interface.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface ICalendarObjectContainer extends \Sabre\DAV\ICollection {
+
+    /**
+     * Performs a calendar-query on the contents of this calendar.
+     *
+     * The calendar-query is defined in RFC4791 : CalDAV. Using the
+     * calendar-query it is possible for a client to request a specific set of
+     * object, based on contents of iCalendar properties, date-ranges and
+     * iCalendar component types (VTODO, VEVENT).
+     *
+     * This method should just return a list of (relative) urls that match this
+     * query.
+     *
+     * The list of filters are specified as an array. The exact array is
+     * documented by \Sabre\CalDAV\CalendarQueryParser.
+     *
+     * @param array $filters
+     * @return array
+     */
+    function calendarQuery(array $filters);
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/IShareableCalendar.php b/vendor/sabre/dav/lib/CalDAV/IShareableCalendar.php
new file mode 100644
index 000000000..cfda91a55
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/IShareableCalendar.php
@@ -0,0 +1,48 @@
+<?php
+
+namespace Sabre\CalDAV;
+
+/**
+ * This interface represents a Calendar that can be shared with other users.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface IShareableCalendar extends ICalendar {
+
+    /**
+     * Updates the list of shares.
+     *
+     * The first array is a list of people that are to be added to the
+     * calendar.
+     *
+     * Every element in the add array has the following properties:
+     *   * href - A url. Usually a mailto: address
+     *   * commonName - Usually a first and last name, or false
+     *   * summary - A description of the share, can also be false
+     *   * readOnly - A boolean value
+     *
+     * Every element in the remove array is just the address string.
+     *
+     * @param array $add
+     * @param array $remove
+     * @return void
+     */
+    function updateShares(array $add, array $remove);
+
+    /**
+     * Returns the list of people whom this calendar is shared with.
+     *
+     * Every element in this array should have the following properties:
+     *   * href - Often a mailto: address
+     *   * commonName - Optional, for example a first + last name
+     *   * status - See the Sabre\CalDAV\SharingPlugin::STATUS_ constants.
+     *   * readOnly - boolean
+     *   * summary - Optional, a description for the share
+     *
+     * @return array
+     */
+    function getShares();
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/ISharedCalendar.php b/vendor/sabre/dav/lib/CalDAV/ISharedCalendar.php
new file mode 100644
index 000000000..84442ac21
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/ISharedCalendar.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace Sabre\CalDAV;
+
+/**
+ * This interface represents a Calendar that is shared by a different user.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface ISharedCalendar extends ICalendar {
+
+    /**
+     * This method should return the url of the owners' copy of the shared
+     * calendar.
+     *
+     * @return string
+     */
+    function getSharedUrl();
+
+    /**
+     * Returns the list of people whom this calendar is shared with.
+     *
+     * Every element in this array should have the following properties:
+     *   * href - Often a mailto: address
+     *   * commonName - Optional, for example a first + last name
+     *   * status - See the Sabre\CalDAV\SharingPlugin::STATUS_ constants.
+     *   * readOnly - boolean
+     *   * summary - Optional, a description for the share
+     *
+     * @return array
+     */
+    function getShares();
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Notifications/Collection.php b/vendor/sabre/dav/lib/CalDAV/Notifications/Collection.php
new file mode 100644
index 000000000..1fcc1171c
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Notifications/Collection.php
@@ -0,0 +1,173 @@
+<?php
+
+namespace Sabre\CalDAV\Notifications;
+
+use Sabre\DAV;
+use Sabre\CalDAV;
+use Sabre\DAVACL;
+
+/**
+ * This node represents a list of notifications.
+ *
+ * It provides no additional functionality, but you must implement this
+ * interface to allow the Notifications plugin to mark the collection
+ * as a notifications collection.
+ *
+ * This collection should only return Sabre\CalDAV\Notifications\INode nodes as
+ * its children.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Collection extends DAV\Collection implements ICollection, DAVACL\IACL {
+
+    /**
+     * The notification backend
+     *
+     * @var Sabre\CalDAV\Backend\NotificationSupport
+     */
+    protected $caldavBackend;
+
+    /**
+     * Principal uri
+     *
+     * @var string
+     */
+    protected $principalUri;
+
+    /**
+     * Constructor
+     *
+     * @param CalDAV\Backend\NotificationSupport $caldavBackend
+     * @param string $principalUri
+     */
+    function __construct(CalDAV\Backend\NotificationSupport $caldavBackend, $principalUri) {
+
+        $this->caldavBackend = $caldavBackend;
+        $this->principalUri = $principalUri;
+
+    }
+
+    /**
+     * Returns all notifications for a principal
+     *
+     * @return array
+     */
+    function getChildren() {
+
+        $children = [];
+        $notifications = $this->caldavBackend->getNotificationsForPrincipal($this->principalUri);
+
+        foreach ($notifications as $notification) {
+
+            $children[] = new Node(
+                $this->caldavBackend,
+                $this->principalUri,
+                $notification
+            );
+        }
+
+        return $children;
+
+    }
+
+    /**
+     * Returns the name of this object
+     *
+     * @return string
+     */
+    function getName() {
+
+        return 'notifications';
+
+    }
+
+    /**
+     * Returns the owner principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getOwner() {
+
+        return $this->principalUri;
+
+    }
+
+    /**
+     * Returns a group principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getGroup() {
+
+        return null;
+
+    }
+
+    /**
+     * Returns a list of ACE's for this node.
+     *
+     * Each ACE has the following properties:
+     *   * 'privilege', a string such as {DAV:}read or {DAV:}write. These are
+     *     currently the only supported privileges
+     *   * 'principal', a url to the principal who owns the node
+     *   * 'protected' (optional), indicating that this ACE is not allowed to
+     *      be updated.
+     *
+     * @return array
+     */
+    function getACL() {
+
+        return [
+            [
+                'principal' => $this->getOwner(),
+                'privilege' => '{DAV:}read',
+                'protected' => true,
+            ],
+            [
+                'principal' => $this->getOwner(),
+                'privilege' => '{DAV:}write',
+                'protected' => true,
+            ]
+        ];
+
+    }
+
+    /**
+     * Updates the ACL
+     *
+     * This method will receive a list of new ACE's as an array argument.
+     *
+     * @param array $acl
+     * @return void
+     */
+    function setACL(array $acl) {
+
+        throw new DAV\Exception\NotImplemented('Updating ACLs is not implemented here');
+
+    }
+
+    /**
+     * Returns the list of supported privileges for this node.
+     *
+     * The returned data structure is a list of nested privileges.
+     * See Sabre\DAVACL\Plugin::getDefaultSupportedPrivilegeSet for a simple
+     * standard structure.
+     *
+     * If null is returned from this method, the default privilege set is used,
+     * which is fine for most common usecases.
+     *
+     * @return array|null
+     */
+    function getSupportedPrivilegeSet() {
+
+        return null;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Notifications/ICollection.php b/vendor/sabre/dav/lib/CalDAV/Notifications/ICollection.php
new file mode 100644
index 000000000..008e87435
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Notifications/ICollection.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace Sabre\CalDAV\Notifications;
+
+use Sabre\DAV;
+
+/**
+ * This node represents a list of notifications.
+ *
+ * It provides no additional functionality, but you must implement this
+ * interface to allow the Notifications plugin to mark the collection
+ * as a notifications collection.
+ *
+ * This collection should only return Sabre\CalDAV\Notifications\INode nodes as
+ * its children.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface ICollection extends DAV\ICollection {
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Notifications/INode.php b/vendor/sabre/dav/lib/CalDAV/Notifications/INode.php
new file mode 100644
index 000000000..f9986b714
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Notifications/INode.php
@@ -0,0 +1,38 @@
+<?php
+
+namespace Sabre\CalDAV\Notifications;
+
+/**
+ * This node represents a single notification.
+ *
+ * The signature is mostly identical to that of Sabre\DAV\IFile, but the get() method
+ * MUST return an xml document that matches the requirements of the
+ * 'caldav-notifications.txt' spec.
+ *
+ * For a complete example, check out the Notification class, which contains
+ * some helper functions.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface INode {
+
+    /**
+     * This method must return an xml element, using the
+     * Sabre\CalDAV\Notifications\INotificationType classes.
+     *
+     * @return INotificationType
+     */
+    function getNotificationType();
+
+    /**
+     * Returns the etag for the notification.
+     *
+     * The etag must be surrounded by litteral double-quotes.
+     *
+     * @return string
+     */
+    function getETag();
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Notifications/Node.php b/vendor/sabre/dav/lib/CalDAV/Notifications/Node.php
new file mode 100644
index 000000000..47e78d5de
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Notifications/Node.php
@@ -0,0 +1,193 @@
+<?php
+
+namespace Sabre\CalDAV\Notifications;
+
+use Sabre\DAV;
+use Sabre\CalDAV;
+use Sabre\CalDAV\Xml\Notification\NotificationInterface;
+use Sabre\DAVACL;
+
+/**
+ * This node represents a single notification.
+ *
+ * The signature is mostly identical to that of Sabre\DAV\IFile, but the get() method
+ * MUST return an xml document that matches the requirements of the
+ * 'caldav-notifications.txt' spec.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Node extends DAV\File implements INode, DAVACL\IACL {
+
+    /**
+     * The notification backend
+     *
+     * @var Sabre\CalDAV\Backend\NotificationSupport
+     */
+    protected $caldavBackend;
+
+    /**
+     * The actual notification
+     *
+     * @var Sabre\CalDAV\Notifications\INotificationType
+     */
+    protected $notification;
+
+    /**
+     * Owner principal of the notification
+     *
+     * @var string
+     */
+    protected $principalUri;
+
+    /**
+     * Constructor
+     *
+     * @param CalDAV\Backend\NotificationSupport $caldavBackend
+     * @param string $principalUri
+     * @param NotificationInterface $notification
+     */
+    function __construct(CalDAV\Backend\NotificationSupport $caldavBackend, $principalUri, NotificationInterface $notification) {
+
+        $this->caldavBackend = $caldavBackend;
+        $this->principalUri = $principalUri;
+        $this->notification = $notification;
+
+    }
+
+    /**
+     * Returns the path name for this notification
+     *
+     * @return id
+     */
+    function getName() {
+
+        return $this->notification->getId() . '.xml';
+
+    }
+
+    /**
+     * Returns the etag for the notification.
+     *
+     * The etag must be surrounded by litteral double-quotes.
+     *
+     * @return string
+     */
+    function getETag() {
+
+        return $this->notification->getETag();
+
+    }
+
+    /**
+     * This method must return an xml element, using the
+     * Sabre\CalDAV\Notifications\INotificationType classes.
+     *
+     * @return INotificationType
+     */
+    function getNotificationType() {
+
+        return $this->notification;
+
+    }
+
+    /**
+     * Deletes this notification
+     *
+     * @return void
+     */
+    function delete() {
+
+        $this->caldavBackend->deleteNotification($this->getOwner(), $this->notification);
+
+    }
+
+    /**
+     * Returns the owner principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getOwner() {
+
+        return $this->principalUri;
+
+    }
+
+    /**
+     * Returns a group principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getGroup() {
+
+        return null;
+
+    }
+
+    /**
+     * Returns a list of ACE's for this node.
+     *
+     * Each ACE has the following properties:
+     *   * 'privilege', a string such as {DAV:}read or {DAV:}write. These are
+     *     currently the only supported privileges
+     *   * 'principal', a url to the principal who owns the node
+     *   * 'protected' (optional), indicating that this ACE is not allowed to
+     *      be updated.
+     *
+     * @return array
+     */
+    function getACL() {
+
+        return [
+            [
+                'principal' => $this->getOwner(),
+                'privilege' => '{DAV:}read',
+                'protected' => true,
+            ],
+            [
+                'principal' => $this->getOwner(),
+                'privilege' => '{DAV:}write',
+                'protected' => true,
+            ]
+        ];
+
+    }
+
+    /**
+     * Updates the ACL
+     *
+     * This method will receive a list of new ACE's as an array argument.
+     *
+     * @param array $acl
+     * @return void
+     */
+    function setACL(array $acl) {
+
+        throw new DAV\Exception\NotImplemented('Updating ACLs is not implemented here');
+
+    }
+
+    /**
+     * Returns the list of supported privileges for this node.
+     *
+     * The returned data structure is a list of nested privileges.
+     * See Sabre\DAVACL\Plugin::getDefaultSupportedPrivilegeSet for a simple
+     * standard structure.
+     *
+     * If null is returned from this method, the default privilege set is used,
+     * which is fine for most common usecases.
+     *
+     * @return array|null
+     */
+    function getSupportedPrivilegeSet() {
+
+        return null;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Notifications/Plugin.php b/vendor/sabre/dav/lib/CalDAV/Notifications/Plugin.php
new file mode 100644
index 000000000..546bf927f
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Notifications/Plugin.php
@@ -0,0 +1,180 @@
+<?php
+
+namespace Sabre\CalDAV\Notifications;
+
+use Sabre\DAV;
+use Sabre\DAV\PropFind;
+use Sabre\DAV\INode as BaseINode;
+use Sabre\DAV\ServerPlugin;
+use Sabre\DAV\Server;
+use Sabre\DAVACL;
+use Sabre\HTTP\RequestInterface;
+use Sabre\HTTP\ResponseInterface;
+
+/**
+ * Notifications plugin
+ *
+ * This plugin implements several features required by the caldav-notification
+ * draft specification.
+ *
+ * Before version 2.1.0 this functionality was part of Sabre\CalDAV\Plugin but
+ * this has since been split up.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Plugin extends ServerPlugin {
+
+    /**
+     * This is the namespace for the proprietary calendarserver extensions
+     */
+    const NS_CALENDARSERVER = 'http://calendarserver.org/ns/';
+
+    /**
+     * Reference to the main server object.
+     *
+     * @var Server
+     */
+    protected $server;
+
+    /**
+     * Returns a plugin name.
+     *
+     * Using this name other plugins will be able to access other plugins
+     * using \Sabre\DAV\Server::getPlugin
+     *
+     * @return string
+     */
+    function getPluginName() {
+
+        return 'notifications';
+
+    }
+
+    /**
+     * This initializes the plugin.
+     *
+     * This function is called by Sabre\DAV\Server, after
+     * addPlugin is called.
+     *
+     * This method should set up the required event subscriptions.
+     *
+     * @param Server $server
+     * @return void
+     */
+    function initialize(Server $server) {
+
+        $this->server = $server;
+        $server->on('method:GET', [$this, 'httpGet'], 90);
+        $server->on('propFind',   [$this, 'propFind']);
+
+        $server->xml->namespaceMap[self::NS_CALENDARSERVER] = 'cs';
+        $server->resourceTypeMapping['\\Sabre\\CalDAV\\Notifications\\ICollection'] = '{' . self::NS_CALENDARSERVER . '}notification';
+
+        array_push($server->protectedProperties,
+            '{' . self::NS_CALENDARSERVER . '}notification-URL',
+            '{' . self::NS_CALENDARSERVER . '}notificationtype'
+        );
+
+    }
+
+    /**
+     * PropFind
+     *
+     * @param PropFind $propFind
+     * @param BaseINode $node
+     * @return void
+     */
+    function propFind(PropFind $propFind, BaseINode $node) {
+
+        $caldavPlugin = $this->server->getPlugin('caldav');
+
+        if ($node instanceof DAVACL\IPrincipal) {
+
+            $principalUrl = $node->getPrincipalUrl();
+
+            // notification-URL property
+            $propFind->handle('{' . self::NS_CALENDARSERVER . '}notification-URL', function() use ($principalUrl, $caldavPlugin) {
+
+                $notificationPath = $caldavPlugin->getCalendarHomeForPrincipal($principalUrl) . '/notifications/';
+                return new DAV\Xml\Property\Href($notificationPath);
+
+            });
+
+        }
+
+        if ($node instanceof INode) {
+
+            $propFind->handle(
+                '{' . self::NS_CALENDARSERVER . '}notificationtype',
+                [$node, 'getNotificationType']
+            );
+
+        }
+
+    }
+
+    /**
+     * This event is triggered before the usual GET request handler.
+     *
+     * We use this to intercept GET calls to notification nodes, and return the
+     * proper response.
+     *
+     * @param RequestInterface $request
+     * @param ResponseInterface $response
+     * @return void
+     */
+    function httpGet(RequestInterface $request, ResponseInterface $response) {
+
+        $path = $request->getPath();
+
+        try {
+            $node = $this->server->tree->getNodeForPath($path);
+        } catch (DAV\Exception\NotFound $e) {
+            return;
+        }
+
+        if (!$node instanceof INode)
+            return;
+
+        $writer = $this->server->xml->getWriter();
+        $writer->contextUri = $this->server->getBaseUri();
+        $writer->openMemory();
+        $writer->startDocument('1.0', 'UTF-8');
+        $writer->startElement('{http://calendarserver.org/ns/}notification');
+        $node->getNotificationType()->xmlSerializeFull($writer);
+        $writer->endElement();
+
+        $response->setHeader('Content-Type', 'application/xml');
+        $response->setHeader('ETag', $node->getETag());
+        $response->setStatus(200);
+        $response->setBody($writer->outputMemory());
+
+        // Return false to break the event chain.
+        return false;
+
+    }
+
+    /**
+     * Returns a bunch of meta-data about the plugin.
+     *
+     * Providing this information is optional, and is mainly displayed by the
+     * Browser plugin.
+     *
+     * The description key in the returned array may contain html and will not
+     * be sanitized.
+     *
+     * @return array
+     */
+    function getPluginInfo() {
+
+        return [
+            'name'        => $this->getPluginName(),
+            'description' => 'Adds support for caldav-notifications, which is required to enable caldav-sharing.',
+            'link'        => 'http://sabre.io/dav/caldav-sharing/',
+        ];
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Plugin.php b/vendor/sabre/dav/lib/CalDAV/Plugin.php
new file mode 100644
index 000000000..663490023
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Plugin.php
@@ -0,0 +1,1025 @@
+<?php
+
+namespace Sabre\CalDAV;
+
+use DateTimeZone;
+use Sabre\DAV;
+use Sabre\DAV\Exception\BadRequest;
+use Sabre\DAV\MkCol;
+use Sabre\DAV\Xml\Property\Href;
+use Sabre\DAVACL;
+use Sabre\VObject;
+use Sabre\HTTP;
+use Sabre\Uri;
+use Sabre\HTTP\RequestInterface;
+use Sabre\HTTP\ResponseInterface;
+
+/**
+ * CalDAV plugin
+ *
+ * This plugin provides functionality added by CalDAV (RFC 4791)
+ * It implements new reports, and the MKCALENDAR method.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Plugin extends DAV\ServerPlugin {
+
+    /**
+     * This is the official CalDAV namespace
+     */
+    const NS_CALDAV = 'urn:ietf:params:xml:ns:caldav';
+
+    /**
+     * This is the namespace for the proprietary calendarserver extensions
+     */
+    const NS_CALENDARSERVER = 'http://calendarserver.org/ns/';
+
+    /**
+     * The hardcoded root for calendar objects. It is unfortunate
+     * that we're stuck with it, but it will have to do for now
+     */
+    const CALENDAR_ROOT = 'calendars';
+
+    /**
+     * Reference to server object
+     *
+     * @var DAV\Server
+     */
+    protected $server;
+
+    /**
+     * The default PDO storage uses a MySQL MEDIUMBLOB for iCalendar data,
+     * which can hold up to 2^24 = 16777216 bytes. This is plenty. We're
+     * capping it to 10M here.
+     */
+    protected $maxResourceSize = 10000000;
+
+    /**
+     * Use this method to tell the server this plugin defines additional
+     * HTTP methods.
+     *
+     * This method is passed a uri. It should only return HTTP methods that are
+     * available for the specified uri.
+     *
+     * @param string $uri
+     * @return array
+     */
+    function getHTTPMethods($uri) {
+
+        // The MKCALENDAR is only available on unmapped uri's, whose
+        // parents extend IExtendedCollection
+        list($parent, $name) = Uri\split($uri);
+
+        $node = $this->server->tree->getNodeForPath($parent);
+
+        if ($node instanceof DAV\IExtendedCollection) {
+            try {
+                $node->getChild($name);
+            } catch (DAV\Exception\NotFound $e) {
+                return ['MKCALENDAR'];
+            }
+        }
+        return [];
+
+    }
+
+    /**
+     * Returns the path to a principal's calendar home.
+     *
+     * The return url must not end with a slash.
+     * This function should return null in case a principal did not have
+     * a calendar home.
+     *
+     * @param string $principalUrl
+     * @return string
+     */
+    function getCalendarHomeForPrincipal($principalUrl) {
+
+        // The default behavior for most sabre/dav servers is that there is a
+        // principals root node, which contains users directly under it.
+        //
+        // This function assumes that there are two components in a principal
+        // path. If there's more, we don't return a calendar home. This
+        // excludes things like the calendar-proxy-read principal (which it
+        // should).
+        $parts = explode('/', trim($principalUrl, '/'));
+        if (count($parts) !== 2) return;
+        if ($parts[0] !== 'principals') return;
+
+        return self::CALENDAR_ROOT . '/' . $parts[1];
+
+    }
+
+    /**
+     * Returns a list of features for the DAV: HTTP header.
+     *
+     * @return array
+     */
+    function getFeatures() {
+
+        return ['calendar-access', 'calendar-proxy'];
+
+    }
+
+    /**
+     * Returns a plugin name.
+     *
+     * Using this name other plugins will be able to access other plugins
+     * using DAV\Server::getPlugin
+     *
+     * @return string
+     */
+    function getPluginName() {
+
+        return 'caldav';
+
+    }
+
+    /**
+     * Returns a list of reports this plugin supports.
+     *
+     * This will be used in the {DAV:}supported-report-set property.
+     * Note that you still need to subscribe to the 'report' event to actually
+     * implement them
+     *
+     * @param string $uri
+     * @return array
+     */
+    function getSupportedReportSet($uri) {
+
+        $node = $this->server->tree->getNodeForPath($uri);
+
+        $reports = [];
+        if ($node instanceof ICalendarObjectContainer || $node instanceof ICalendarObject) {
+            $reports[] = '{' . self::NS_CALDAV . '}calendar-multiget';
+            $reports[] = '{' . self::NS_CALDAV . '}calendar-query';
+        }
+        if ($node instanceof ICalendar) {
+            $reports[] = '{' . self::NS_CALDAV . '}free-busy-query';
+        }
+        // iCal has a bug where it assumes that sync support is enabled, only
+        // if we say we support it on the calendar-home, even though this is
+        // not actually the case.
+        if ($node instanceof CalendarHome && $this->server->getPlugin('sync')) {
+            $reports[] = '{DAV:}sync-collection';
+        }
+        return $reports;
+
+    }
+
+    /**
+     * Initializes the plugin
+     *
+     * @param DAV\Server $server
+     * @return void
+     */
+    function initialize(DAV\Server $server) {
+
+        $this->server = $server;
+
+        $server->on('method:MKCALENDAR',   [$this, 'httpMkCalendar']);
+        $server->on('report',              [$this, 'report']);
+        $server->on('propFind',            [$this, 'propFind']);
+        $server->on('onHTMLActionsPanel',  [$this, 'htmlActionsPanel']);
+        $server->on('beforeCreateFile',    [$this, 'beforeCreateFile']);
+        $server->on('beforeWriteContent',  [$this, 'beforeWriteContent']);
+        $server->on('afterMethod:GET',     [$this, 'httpAfterGET']);
+
+        $server->xml->namespaceMap[self::NS_CALDAV] = 'cal';
+        $server->xml->namespaceMap[self::NS_CALENDARSERVER] = 'cs';
+
+        $server->xml->elementMap['{' . self::NS_CALDAV . '}supported-calendar-component-set'] = 'Sabre\\CalDAV\\Xml\\Property\\SupportedCalendarComponentSet';
+        $server->xml->elementMap['{' . self::NS_CALDAV . '}calendar-query'] = 'Sabre\\CalDAV\\Xml\\Request\\CalendarQueryReport';
+        $server->xml->elementMap['{' . self::NS_CALDAV . '}calendar-multiget'] = 'Sabre\\CalDAV\\Xml\\Request\\CalendarMultiGetReport';
+        $server->xml->elementMap['{' . self::NS_CALDAV . '}free-busy-query'] = 'Sabre\\CalDAV\\Xml\\Request\\FreeBusyQueryReport';
+        $server->xml->elementMap['{' . self::NS_CALDAV . '}mkcalendar'] = 'Sabre\\CalDAV\\Xml\\Request\\MkCalendar';
+        $server->xml->elementMap['{' . self::NS_CALDAV . '}schedule-calendar-transp'] = 'Sabre\\CalDAV\\Xml\\Property\\ScheduleCalendarTransp';
+        $server->xml->elementMap['{' . self::NS_CALDAV . '}supported-calendar-component-set'] = 'Sabre\\CalDAV\\Xml\\Property\\SupportedCalendarComponentSet';
+
+        $server->resourceTypeMapping['\\Sabre\\CalDAV\\ICalendar'] = '{urn:ietf:params:xml:ns:caldav}calendar';
+
+        $server->resourceTypeMapping['\\Sabre\\CalDAV\\Principal\\IProxyRead'] = '{http://calendarserver.org/ns/}calendar-proxy-read';
+        $server->resourceTypeMapping['\\Sabre\\CalDAV\\Principal\\IProxyWrite'] = '{http://calendarserver.org/ns/}calendar-proxy-write';
+
+        array_push($server->protectedProperties,
+
+            '{' . self::NS_CALDAV . '}supported-calendar-component-set',
+            '{' . self::NS_CALDAV . '}supported-calendar-data',
+            '{' . self::NS_CALDAV . '}max-resource-size',
+            '{' . self::NS_CALDAV . '}min-date-time',
+            '{' . self::NS_CALDAV . '}max-date-time',
+            '{' . self::NS_CALDAV . '}max-instances',
+            '{' . self::NS_CALDAV . '}max-attendees-per-instance',
+            '{' . self::NS_CALDAV . '}calendar-home-set',
+            '{' . self::NS_CALDAV . '}supported-collation-set',
+            '{' . self::NS_CALDAV . '}calendar-data',
+
+            // CalendarServer extensions
+            '{' . self::NS_CALENDARSERVER . '}getctag',
+            '{' . self::NS_CALENDARSERVER . '}calendar-proxy-read-for',
+            '{' . self::NS_CALENDARSERVER . '}calendar-proxy-write-for'
+
+        );
+
+        if ($aclPlugin = $server->getPlugin('acl')) {
+            $aclPlugin->principalSearchPropertySet['{' . self::NS_CALDAV . '}calendar-user-address-set'] = 'Calendar address';
+        }
+    }
+
+    /**
+     * This functions handles REPORT requests specific to CalDAV
+     *
+     * @param string $reportName
+     * @param mixed $report
+     * @return bool
+     */
+    function report($reportName, $report) {
+
+        switch ($reportName) {
+            case '{' . self::NS_CALDAV . '}calendar-multiget' :
+                $this->server->transactionType = 'report-calendar-multiget';
+                $this->calendarMultiGetReport($report);
+                return false;
+            case '{' . self::NS_CALDAV . '}calendar-query' :
+                $this->server->transactionType = 'report-calendar-query';
+                $this->calendarQueryReport($report);
+                return false;
+            case '{' . self::NS_CALDAV . '}free-busy-query' :
+                $this->server->transactionType = 'report-free-busy-query';
+                $this->freeBusyQueryReport($report);
+                return false;
+
+        }
+
+
+    }
+
+    /**
+     * This function handles the MKCALENDAR HTTP method, which creates
+     * a new calendar.
+     *
+     * @param RequestInterface $request
+     * @param ResponseInterface $response
+     * @return bool
+     */
+    function httpMkCalendar(RequestInterface $request, ResponseInterface $response) {
+
+        $body = $request->getBodyAsString();
+        $path = $request->getPath();
+
+        $properties = [];
+
+        if ($body) {
+
+            try {
+                $mkcalendar = $this->server->xml->expect(
+                    '{urn:ietf:params:xml:ns:caldav}mkcalendar',
+                    $body
+                );
+            } catch (\Sabre\Xml\ParseException $e) {
+                throw new BadRequest($e->getMessage(), null, $e);
+            }
+            $properties = $mkcalendar->getProperties();
+
+        }
+
+        // iCal abuses MKCALENDAR since iCal 10.9.2 to create server-stored
+        // subscriptions. Before that it used MKCOL which was the correct way
+        // to do this.
+        //
+        // If the body had a {DAV:}resourcetype, it means we stumbled upon this
+        // request, and we simply use it instead of the pre-defined list.
+        if (isset($properties['{DAV:}resourcetype'])) {
+            $resourceType = $properties['{DAV:}resourcetype']->getValue();
+        } else {
+            $resourceType = ['{DAV:}collection','{urn:ietf:params:xml:ns:caldav}calendar'];
+        }
+
+        $this->server->createCollection($path, new MkCol($resourceType, $properties));
+
+        $this->server->httpResponse->setStatus(201);
+        $this->server->httpResponse->setHeader('Content-Length', 0);
+
+        // This breaks the method chain.
+        return false;
+    }
+
+    /**
+     * PropFind
+     *
+     * This method handler is invoked before any after properties for a
+     * resource are fetched. This allows us to add in any CalDAV specific
+     * properties.
+     *
+     * @param DAV\PropFind $propFind
+     * @param DAV\INode $node
+     * @return void
+     */
+    function propFind(DAV\PropFind $propFind, DAV\INode $node) {
+
+        $ns = '{' . self::NS_CALDAV . '}';
+
+        if ($node instanceof ICalendarObjectContainer) {
+
+            $propFind->handle($ns . 'max-resource-size', $this->maxResourceSize);
+            $propFind->handle($ns . 'supported-calendar-data', function() {
+                return new Xml\Property\SupportedCalendarData();
+            });
+            $propFind->handle($ns . 'supported-collation-set', function() {
+                return new Xml\Property\SupportedCollationSet();
+            });
+
+        }
+
+        if ($node instanceof DAVACL\IPrincipal) {
+
+            $principalUrl = $node->getPrincipalUrl();
+
+            $propFind->handle('{' . self::NS_CALDAV . '}calendar-home-set', function() use ($principalUrl) {
+
+                $calendarHomePath = $this->getCalendarHomeForPrincipal($principalUrl);
+                if (is_null($calendarHomePath)) return null;
+                return new Href($calendarHomePath . '/');
+
+            });
+            // The calendar-user-address-set property is basically mapped to
+            // the {DAV:}alternate-URI-set property.
+            $propFind->handle('{' . self::NS_CALDAV . '}calendar-user-address-set', function() use ($node) {
+                $addresses = $node->getAlternateUriSet();
+                $addresses[] = $this->server->getBaseUri() . $node->getPrincipalUrl() . '/';
+                return new Href($addresses, false);
+            });
+            // For some reason somebody thought it was a good idea to add
+            // another one of these properties. We're supporting it too.
+            $propFind->handle('{' . self::NS_CALENDARSERVER . '}email-address-set', function() use ($node) {
+                $addresses = $node->getAlternateUriSet();
+                $emails = [];
+                foreach ($addresses as $address) {
+                    if (substr($address, 0, 7) === 'mailto:') {
+                        $emails[] = substr($address, 7);
+                    }
+                }
+                return new Xml\Property\EmailAddressSet($emails);
+            });
+
+            // These two properties are shortcuts for ical to easily find
+            // other principals this principal has access to.
+            $propRead = '{' . self::NS_CALENDARSERVER . '}calendar-proxy-read-for';
+            $propWrite = '{' . self::NS_CALENDARSERVER . '}calendar-proxy-write-for';
+
+            if ($propFind->getStatus($propRead) === 404 || $propFind->getStatus($propWrite) === 404) {
+
+                $aclPlugin = $this->server->getPlugin('acl');
+                $membership = $aclPlugin->getPrincipalMembership($propFind->getPath());
+                $readList = [];
+                $writeList = [];
+
+                foreach ($membership as $group) {
+
+                    $groupNode = $this->server->tree->getNodeForPath($group);
+
+                    $listItem = Uri\split($group)[0] . '/';
+
+                    // If the node is either ap proxy-read or proxy-write
+                    // group, we grab the parent principal and add it to the
+                    // list.
+                    if ($groupNode instanceof Principal\IProxyRead) {
+                        $readList[] = $listItem;
+                    }
+                    if ($groupNode instanceof Principal\IProxyWrite) {
+                        $writeList[] = $listItem;
+                    }
+
+                }
+
+                $propFind->set($propRead, new Href($readList));
+                $propFind->set($propWrite, new Href($writeList));
+
+            }
+
+        } // instanceof IPrincipal
+
+        if ($node instanceof ICalendarObject) {
+
+            // The calendar-data property is not supposed to be a 'real'
+            // property, but in large chunks of the spec it does act as such.
+            // Therefore we simply expose it as a property.
+            $propFind->handle('{' . self::NS_CALDAV . '}calendar-data', function() use ($node) {
+                $val = $node->get();
+                if (is_resource($val))
+                    $val = stream_get_contents($val);
+
+                // Taking out \r to not screw up the xml output
+                return str_replace("\r", "", $val);
+
+            });
+
+        }
+
+    }
+
+    /**
+     * This function handles the calendar-multiget REPORT.
+     *
+     * This report is used by the client to fetch the content of a series
+     * of urls. Effectively avoiding a lot of redundant requests.
+     *
+     * @param CalendarMultiGetReport $report
+     * @return void
+     */
+    function calendarMultiGetReport($report) {
+
+        $needsJson = $report->contentType === 'application/calendar+json';
+
+        $timeZones = [];
+        $propertyList = [];
+
+        $paths = array_map(
+            [$this->server, 'calculateUri'],
+            $report->hrefs
+        );
+
+        foreach ($this->server->getPropertiesForMultiplePaths($paths, $report->properties) as $uri => $objProps) {
+
+            if (($needsJson || $report->expand) && isset($objProps[200]['{' . self::NS_CALDAV . '}calendar-data'])) {
+                $vObject = VObject\Reader::read($objProps[200]['{' . self::NS_CALDAV . '}calendar-data']);
+
+                if ($report->expand) {
+                    // We're expanding, and for that we need to figure out the
+                    // calendar's timezone.
+                    list($calendarPath) = Uri\split($uri);
+                    if (!isset($timeZones[$calendarPath])) {
+                        // Checking the calendar-timezone property.
+                        $tzProp = '{' . self::NS_CALDAV . '}calendar-timezone';
+                        $tzResult = $this->server->getProperties($calendarPath, [$tzProp]);
+                        if (isset($tzResult[$tzProp])) {
+                            // This property contains a VCALENDAR with a single
+                            // VTIMEZONE.
+                            $vtimezoneObj = VObject\Reader::read($tzResult[$tzProp]);
+                            $timeZone = $vtimezoneObj->VTIMEZONE->getTimeZone();
+                        } else {
+                            // Defaulting to UTC.
+                            $timeZone = new DateTimeZone('UTC');
+                        }
+                        $timeZones[$calendarPath] = $timeZone;
+                    }
+
+                    $vObject = $vObject->expand($report->expand['start'], $report->expand['end'], $timeZones[$calendarPath]);
+                }
+                if ($needsJson) {
+                    $objProps[200]['{' . self::NS_CALDAV . '}calendar-data'] = json_encode($vObject->jsonSerialize());
+                } else {
+                    $objProps[200]['{' . self::NS_CALDAV . '}calendar-data'] = $vObject->serialize();
+                }
+                // Destroy circular references so PHP will garbage collect the
+                // object.
+                $vObject->destroy();
+            }
+
+            $propertyList[] = $objProps;
+
+        }
+
+        $prefer = $this->server->getHTTPPrefer();
+
+        $this->server->httpResponse->setStatus(207);
+        $this->server->httpResponse->setHeader('Content-Type', 'application/xml; charset=utf-8');
+        $this->server->httpResponse->setHeader('Vary', 'Brief,Prefer');
+        $this->server->httpResponse->setBody($this->server->generateMultiStatus($propertyList, $prefer['return'] === 'minimal'));
+
+    }
+
+    /**
+     * This function handles the calendar-query REPORT
+     *
+     * This report is used by clients to request calendar objects based on
+     * complex conditions.
+     *
+     * @param Xml\Request\CalendarQueryReport $report
+     * @return void
+     */
+    function calendarQueryReport($report) {
+
+        $path = $this->server->getRequestUri();
+
+        $needsJson = $report->contentType === 'application/calendar+json';
+
+        $node = $this->server->tree->getNodeForPath($this->server->getRequestUri());
+        $depth = $this->server->getHTTPDepth(0);
+
+        // The default result is an empty array
+        $result = [];
+
+        $calendarTimeZone = null;
+        if ($report->expand) {
+            // We're expanding, and for that we need to figure out the
+            // calendar's timezone.
+            $tzProp = '{' . self::NS_CALDAV . '}calendar-timezone';
+            $tzResult = $this->server->getProperties($path, [$tzProp]);
+            if (isset($tzResult[$tzProp])) {
+                // This property contains a VCALENDAR with a single
+                // VTIMEZONE.
+                $vtimezoneObj = VObject\Reader::read($tzResult[$tzProp]);
+                $calendarTimeZone = $vtimezoneObj->VTIMEZONE->getTimeZone();
+
+                // Destroy circular references so PHP will garbage collect the
+                // object.
+                $vtimezoneObj->destroy();
+            } else {
+                // Defaulting to UTC.
+                $calendarTimeZone = new DateTimeZone('UTC');
+            }
+        }
+
+        // The calendarobject was requested directly. In this case we handle
+        // this locally.
+        if ($depth == 0 && $node instanceof ICalendarObject) {
+
+            $requestedCalendarData = true;
+            $requestedProperties = $report->properties;
+
+            if (!in_array('{urn:ietf:params:xml:ns:caldav}calendar-data', $requestedProperties)) {
+
+                // We always retrieve calendar-data, as we need it for filtering.
+                $requestedProperties[] = '{urn:ietf:params:xml:ns:caldav}calendar-data';
+
+                // If calendar-data wasn't explicitly requested, we need to remove
+                // it after processing.
+                $requestedCalendarData = false;
+            }
+
+            $properties = $this->server->getPropertiesForPath(
+                $path,
+                $requestedProperties,
+                0
+            );
+
+            // This array should have only 1 element, the first calendar
+            // object.
+            $properties = current($properties);
+
+            // If there wasn't any calendar-data returned somehow, we ignore
+            // this.
+            if (isset($properties[200]['{urn:ietf:params:xml:ns:caldav}calendar-data'])) {
+
+                $validator = new CalendarQueryValidator();
+
+                $vObject = VObject\Reader::read($properties[200]['{urn:ietf:params:xml:ns:caldav}calendar-data']);
+                if ($validator->validate($vObject, $report->filters)) {
+
+                    // If the client didn't require the calendar-data property,
+                    // we won't give it back.
+                    if (!$requestedCalendarData) {
+                        unset($properties[200]['{urn:ietf:params:xml:ns:caldav}calendar-data']);
+                    } else {
+
+
+                        if ($report->expand) {
+                            $vObject = $vObject->expand($report->expand['start'], $report->expand['end'], $calendarTimeZone);
+                        }
+                        if ($needsJson) {
+                            $properties[200]['{' . self::NS_CALDAV . '}calendar-data'] = json_encode($vObject->jsonSerialize());
+                        } elseif ($report->expand) {
+                            $properties[200]['{' . self::NS_CALDAV . '}calendar-data'] = $vObject->serialize();
+                        }
+                    }
+
+                    $result = [$properties];
+
+                }
+                // Destroy circular references so PHP will garbage collect the
+                // object.
+                $vObject->destroy();
+
+            }
+
+        }
+
+        if ($node instanceof ICalendarObjectContainer && $depth === 0) {
+
+            if (strpos($this->server->httpRequest->getHeader('User-Agent'), 'MSFT-') === 0) {
+                // Microsoft clients incorrectly supplied depth as 0, when it actually
+                // should have set depth to 1. We're implementing a workaround here
+                // to deal with this.
+                //
+                // This targets at least the following clients:
+                //   Windows 10
+                //   Windows Phone 8, 10
+                $depth = 1;
+            } else {
+                throw new BadRequest('A calendar-query REPORT on a calendar with a Depth: 0 is undefined. Set Depth to 1');
+            }
+
+        }
+
+        // If we're dealing with a calendar, the calendar itself is responsible
+        // for the calendar-query.
+        if ($node instanceof ICalendarObjectContainer && $depth == 1) {
+
+            $nodePaths = $node->calendarQuery($report->filters);
+
+            foreach ($nodePaths as $path) {
+
+                list($properties) =
+                    $this->server->getPropertiesForPath($this->server->getRequestUri() . '/' . $path, $report->properties);
+
+                if (($needsJson || $report->expand)) {
+                    $vObject = VObject\Reader::read($properties[200]['{' . self::NS_CALDAV . '}calendar-data']);
+
+                    if ($report->expand) {
+                        $vObject = $vObject->expand($report->expand['start'], $report->expand['end'], $calendarTimeZone);
+                    }
+
+                    if ($needsJson) {
+                        $properties[200]['{' . self::NS_CALDAV . '}calendar-data'] = json_encode($vObject->jsonSerialize());
+                    } else {
+                        $properties[200]['{' . self::NS_CALDAV . '}calendar-data'] = $vObject->serialize();
+                    }
+
+                    // Destroy circular references so PHP will garbage collect the
+                    // object.
+                    $vObject->destroy();
+                }
+                $result[] = $properties;
+
+            }
+
+        }
+
+        $prefer = $this->server->getHTTPPrefer();
+
+        $this->server->httpResponse->setStatus(207);
+        $this->server->httpResponse->setHeader('Content-Type', 'application/xml; charset=utf-8');
+        $this->server->httpResponse->setHeader('Vary', 'Brief,Prefer');
+        $this->server->httpResponse->setBody($this->server->generateMultiStatus($result, $prefer['return'] === 'minimal'));
+
+    }
+
+    /**
+     * This method is responsible for parsing the request and generating the
+     * response for the CALDAV:free-busy-query REPORT.
+     *
+     * @param Xml\Request\FreeBusyQueryReport $report
+     * @return void
+     */
+    protected function freeBusyQueryReport(Xml\Request\FreeBusyQueryReport $report) {
+
+        $uri = $this->server->getRequestUri();
+
+        $acl = $this->server->getPlugin('acl');
+        if ($acl) {
+            $acl->checkPrivileges($uri, '{' . self::NS_CALDAV . '}read-free-busy');
+        }
+
+        $calendar = $this->server->tree->getNodeForPath($uri);
+        if (!$calendar instanceof ICalendar) {
+            throw new DAV\Exception\NotImplemented('The free-busy-query REPORT is only implemented on calendars');
+        }
+
+        $tzProp = '{' . self::NS_CALDAV . '}calendar-timezone';
+
+        // Figuring out the default timezone for the calendar, for floating
+        // times.
+        $calendarProps = $this->server->getProperties($uri, [$tzProp]);
+
+        if (isset($calendarProps[$tzProp])) {
+            $vtimezoneObj = VObject\Reader::read($calendarProps[$tzProp]);
+            $calendarTimeZone = $vtimezoneObj->VTIMEZONE->getTimeZone();
+            // Destroy circular references so PHP will garbage collect the object.
+            $vtimezoneObj->destroy();
+        } else {
+            $calendarTimeZone = new DateTimeZone('UTC');
+        }
+
+        // Doing a calendar-query first, to make sure we get the most
+        // performance.
+        $urls = $calendar->calendarQuery([
+            'name'         => 'VCALENDAR',
+            'comp-filters' => [
+                [
+                    'name'           => 'VEVENT',
+                    'comp-filters'   => [],
+                    'prop-filters'   => [],
+                    'is-not-defined' => false,
+                    'time-range'     => [
+                        'start' => $report->start,
+                        'end'   => $report->end,
+                    ],
+                ],
+            ],
+            'prop-filters'   => [],
+            'is-not-defined' => false,
+            'time-range'     => null,
+        ]);
+
+        $objects = array_map(function($url) use ($calendar) {
+            $obj = $calendar->getChild($url)->get();
+            return $obj;
+        }, $urls);
+
+        $generator = new VObject\FreeBusyGenerator();
+        $generator->setObjects($objects);
+        $generator->setTimeRange($report->start, $report->end);
+        $generator->setTimeZone($calendarTimeZone);
+        $result = $generator->getResult();
+        $result = $result->serialize();
+
+        $this->server->httpResponse->setStatus(200);
+        $this->server->httpResponse->setHeader('Content-Type', 'text/calendar');
+        $this->server->httpResponse->setHeader('Content-Length', strlen($result));
+        $this->server->httpResponse->setBody($result);
+
+    }
+
+    /**
+     * This method is triggered before a file gets updated with new content.
+     *
+     * This plugin uses this method to ensure that CalDAV objects receive
+     * valid calendar data.
+     *
+     * @param string $path
+     * @param DAV\IFile $node
+     * @param resource $data
+     * @param bool $modified Should be set to true, if this event handler
+     *                       changed &$data.
+     * @return void
+     */
+    function beforeWriteContent($path, DAV\IFile $node, &$data, &$modified) {
+
+        if (!$node instanceof ICalendarObject)
+            return;
+
+        // We're onyl interested in ICalendarObject nodes that are inside of a
+        // real calendar. This is to avoid triggering validation and scheduling
+        // for non-calendars (such as an inbox).
+        list($parent) = Uri\split($path);
+        $parentNode = $this->server->tree->getNodeForPath($parent);
+
+        if (!$parentNode instanceof ICalendar)
+            return;
+
+        $this->validateICalendar(
+            $data,
+            $path,
+            $modified,
+            $this->server->httpRequest,
+            $this->server->httpResponse,
+            false
+        );
+
+    }
+
+    /**
+     * This method is triggered before a new file is created.
+     *
+     * This plugin uses this method to ensure that newly created calendar
+     * objects contain valid calendar data.
+     *
+     * @param string $path
+     * @param resource $data
+     * @param DAV\ICollection $parentNode
+     * @param bool $modified Should be set to true, if this event handler
+     *                       changed &$data.
+     * @return void
+     */
+    function beforeCreateFile($path, &$data, DAV\ICollection $parentNode, &$modified) {
+
+        if (!$parentNode instanceof ICalendar)
+            return;
+
+        $this->validateICalendar(
+            $data,
+            $path,
+            $modified,
+            $this->server->httpRequest,
+            $this->server->httpResponse,
+            true
+        );
+
+    }
+
+    /**
+     * Checks if the submitted iCalendar data is in fact, valid.
+     *
+     * An exception is thrown if it's not.
+     *
+     * @param resource|string $data
+     * @param string $path
+     * @param bool $modified Should be set to true, if this event handler
+     *                       changed &$data.
+     * @param RequestInterface $request The http request.
+     * @param ResponseInterface $response The http response.
+     * @param bool $isNew Is the item a new one, or an update.
+     * @return void
+     */
+    protected function validateICalendar(&$data, $path, &$modified, RequestInterface $request, ResponseInterface $response, $isNew) {
+
+        // If it's a stream, we convert it to a string first.
+        if (is_resource($data)) {
+            $data = stream_get_contents($data);
+        }
+
+        $before = md5($data);
+        // Converting the data to unicode, if needed.
+        $data = DAV\StringUtil::ensureUTF8($data);
+
+        if ($before !== md5($data)) $modified = true;
+
+        try {
+
+            // If the data starts with a [, we can reasonably assume we're dealing
+            // with a jCal object.
+            if (substr($data, 0, 1) === '[') {
+                $vobj = VObject\Reader::readJson($data);
+
+                // Converting $data back to iCalendar, as that's what we
+                // technically support everywhere.
+                $data = $vobj->serialize();
+                $modified = true;
+            } else {
+                $vobj = VObject\Reader::read($data);
+            }
+
+        } catch (VObject\ParseException $e) {
+
+            throw new DAV\Exception\UnsupportedMediaType('This resource only supports valid iCalendar 2.0 data. Parse error: ' . $e->getMessage());
+
+        }
+
+        if ($vobj->name !== 'VCALENDAR') {
+            throw new DAV\Exception\UnsupportedMediaType('This collection can only support iCalendar objects.');
+        }
+
+        $sCCS = '{urn:ietf:params:xml:ns:caldav}supported-calendar-component-set';
+
+        // Get the Supported Components for the target calendar
+        list($parentPath) = Uri\split($path);
+        $calendarProperties = $this->server->getProperties($parentPath, [$sCCS]);
+
+        if (isset($calendarProperties[$sCCS])) {
+            $supportedComponents = $calendarProperties[$sCCS]->getValue();
+        } else {
+            $supportedComponents = ['VJOURNAL', 'VTODO', 'VEVENT'];
+        }
+
+        $foundType = null;
+        $foundUID = null;
+        foreach ($vobj->getComponents() as $component) {
+            switch ($component->name) {
+                case 'VTIMEZONE' :
+                    continue 2;
+                case 'VEVENT' :
+                case 'VTODO' :
+                case 'VJOURNAL' :
+                    if (is_null($foundType)) {
+                        $foundType = $component->name;
+                        if (!in_array($foundType, $supportedComponents)) {
+                            throw new Exception\InvalidComponentType('This calendar only supports ' . implode(', ', $supportedComponents) . '. We found a ' . $foundType);
+                        }
+                        if (!isset($component->UID)) {
+                            throw new DAV\Exception\BadRequest('Every ' . $component->name . ' component must have an UID');
+                        }
+                        $foundUID = (string)$component->UID;
+                    } else {
+                        if ($foundType !== $component->name) {
+                            throw new DAV\Exception\BadRequest('A calendar object must only contain 1 component. We found a ' . $component->name . ' as well as a ' . $foundType);
+                        }
+                        if ($foundUID !== (string)$component->UID) {
+                            throw new DAV\Exception\BadRequest('Every ' . $component->name . ' in this object must have identical UIDs');
+                        }
+                    }
+                    break;
+                default :
+                    throw new DAV\Exception\BadRequest('You are not allowed to create components of type: ' . $component->name . ' here');
+
+            }
+        }
+        if (!$foundType)
+            throw new DAV\Exception\BadRequest('iCalendar object must contain at least 1 of VEVENT, VTODO or VJOURNAL');
+
+        // We use an extra variable to allow event handles to tell us wether
+        // the object was modified or not.
+        //
+        // This helps us determine if we need to re-serialize the object.
+        $subModified = false;
+
+        $this->server->emit(
+            'calendarObjectChange',
+            [
+                $request,
+                $response,
+                $vobj,
+                $parentPath,
+                &$subModified,
+                $isNew
+            ]
+        );
+
+        if ($subModified) {
+            // An event handler told us that it modified the object.
+            $data = $vobj->serialize();
+
+            // Using md5 to figure out if there was an *actual* change.
+            if (!$modified && $before !== md5($data)) {
+                $modified = true;
+            }
+
+        }
+
+        // Destroy circular references so PHP will garbage collect the object.
+        $vobj->destroy();
+
+    }
+
+
+    /**
+     * This method is used to generate HTML output for the
+     * DAV\Browser\Plugin. This allows us to generate an interface users
+     * can use to create new calendars.
+     *
+     * @param DAV\INode $node
+     * @param string $output
+     * @return bool
+     */
+    function htmlActionsPanel(DAV\INode $node, &$output) {
+
+        if (!$node instanceof CalendarHome)
+            return;
+
+        $output .= '<tr><td colspan="2"><form method="post" action="">
+            <h3>Create new calendar</h3>
+            <input type="hidden" name="sabreAction" value="mkcol" />
+            <input type="hidden" name="resourceType" value="{DAV:}collection,{' . self::NS_CALDAV . '}calendar" />
+            <label>Name (uri):</label> <input type="text" name="name" /><br />
+            <label>Display name:</label> <input type="text" name="{DAV:}displayname" /><br />
+            <input type="submit" value="create" />
+            </form>
+            </td></tr>';
+
+        return false;
+
+    }
+
+    /**
+     * This event is triggered after GET requests.
+     *
+     * This is used to transform data into jCal, if this was requested.
+     *
+     * @param RequestInterface $request
+     * @param ResponseInterface $response
+     * @return void
+     */
+    function httpAfterGet(RequestInterface $request, ResponseInterface $response) {
+
+        if (strpos($response->getHeader('Content-Type'), 'text/calendar') === false) {
+            return;
+        }
+
+        $result = HTTP\Util::negotiate(
+            $request->getHeader('Accept'),
+            ['text/calendar', 'application/calendar+json']
+        );
+
+        if ($result !== 'application/calendar+json') {
+            // Do nothing
+            return;
+        }
+
+        // Transforming.
+        $vobj = VObject\Reader::read($response->getBody());
+
+        $jsonBody = json_encode($vobj->jsonSerialize());
+        $response->setBody($jsonBody);
+
+        // Destroy circular references so PHP will garbage collect the object.
+        $vobj->destroy();
+
+        $response->setHeader('Content-Type', 'application/calendar+json');
+        $response->setHeader('Content-Length', strlen($jsonBody));
+
+    }
+
+    /**
+     * Returns a bunch of meta-data about the plugin.
+     *
+     * Providing this information is optional, and is mainly displayed by the
+     * Browser plugin.
+     *
+     * The description key in the returned array may contain html and will not
+     * be sanitized.
+     *
+     * @return array
+     */
+    function getPluginInfo() {
+
+        return [
+            'name'        => $this->getPluginName(),
+            'description' => 'Adds support for CalDAV (rfc4791)',
+            'link'        => 'http://sabre.io/dav/caldav/',
+        ];
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Principal/Collection.php b/vendor/sabre/dav/lib/CalDAV/Principal/Collection.php
new file mode 100644
index 000000000..e19719a76
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Principal/Collection.php
@@ -0,0 +1,33 @@
+<?php
+
+namespace Sabre\CalDAV\Principal;
+
+use Sabre\DAVACL;
+
+/**
+ * Principal collection
+ *
+ * This is an alternative collection to the standard ACL principal collection.
+ * This collection adds support for the calendar-proxy-read and
+ * calendar-proxy-write sub-principals, as defined by the caldav-proxy
+ * specification.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Collection extends DAVACL\PrincipalCollection {
+
+    /**
+     * Returns a child object based on principal information
+     *
+     * @param array $principalInfo
+     * @return User
+     */
+    function getChildForPrincipal(array $principalInfo) {
+
+        return new User($this->principalBackend, $principalInfo);
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Principal/IProxyRead.php b/vendor/sabre/dav/lib/CalDAV/Principal/IProxyRead.php
new file mode 100644
index 000000000..7dd375932
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Principal/IProxyRead.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace Sabre\CalDAV\Principal;
+
+use Sabre\DAVACL;
+
+/**
+ * ProxyRead principal interface
+ *
+ * Any principal node implementing this interface will be picked up as a 'proxy
+ * principal group'.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface IProxyRead extends DAVACL\IPrincipal {
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Principal/IProxyWrite.php b/vendor/sabre/dav/lib/CalDAV/Principal/IProxyWrite.php
new file mode 100644
index 000000000..eda87a4ff
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Principal/IProxyWrite.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace Sabre\CalDAV\Principal;
+
+use Sabre\DAVACL;
+
+/**
+ * ProxyWrite principal interface
+ *
+ * Any principal node implementing this interface will be picked up as a 'proxy
+ * principal group'.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface IProxyWrite extends DAVACL\IPrincipal {
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Principal/ProxyRead.php b/vendor/sabre/dav/lib/CalDAV/Principal/ProxyRead.php
new file mode 100644
index 000000000..93f0fe095
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Principal/ProxyRead.php
@@ -0,0 +1,181 @@
+<?php
+
+namespace Sabre\CalDAV\Principal;
+
+use Sabre\DAVACL;
+use Sabre\DAV;
+
+/**
+ * ProxyRead principal
+ *
+ * This class represents a principal group, hosted under the main principal.
+ * This is needed to implement 'Calendar delegation' support. This class is
+ * instantiated by User.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class ProxyRead implements IProxyRead {
+
+    /**
+     * Principal information from the parent principal.
+     *
+     * @var array
+     */
+    protected $principalInfo;
+
+    /**
+     * Principal backend
+     *
+     * @var DAVACL\PrincipalBackend\BackendInterface
+     */
+    protected $principalBackend;
+
+    /**
+     * Creates the object.
+     *
+     * Note that you MUST supply the parent principal information.
+     *
+     * @param DAVACL\PrincipalBackend\BackendInterface $principalBackend
+     * @param array $principalInfo
+     */
+    function __construct(DAVACL\PrincipalBackend\BackendInterface $principalBackend, array $principalInfo) {
+
+        $this->principalInfo = $principalInfo;
+        $this->principalBackend = $principalBackend;
+
+    }
+
+    /**
+     * Returns this principals name.
+     *
+     * @return string
+     */
+    function getName() {
+
+        return 'calendar-proxy-read';
+
+    }
+
+    /**
+     * Returns the last modification time
+     *
+     * @return null
+     */
+    function getLastModified() {
+
+        return null;
+
+    }
+
+    /**
+     * Deletes the current node
+     *
+     * @throws DAV\Exception\Forbidden
+     * @return void
+     */
+    function delete() {
+
+        throw new DAV\Exception\Forbidden('Permission denied to delete node');
+
+    }
+
+    /**
+     * Renames the node
+     *
+     * @throws DAV\Exception\Forbidden
+     * @param string $name The new name
+     * @return void
+     */
+    function setName($name) {
+
+        throw new DAV\Exception\Forbidden('Permission denied to rename file');
+
+    }
+
+
+    /**
+     * Returns a list of alternative urls for a principal
+     *
+     * This can for example be an email address, or ldap url.
+     *
+     * @return array
+     */
+    function getAlternateUriSet() {
+
+        return [];
+
+    }
+
+    /**
+     * Returns the full principal url
+     *
+     * @return string
+     */
+    function getPrincipalUrl() {
+
+        return $this->principalInfo['uri'] . '/' . $this->getName();
+
+    }
+
+    /**
+     * Returns the list of group members
+     *
+     * If this principal is a group, this function should return
+     * all member principal uri's for the group.
+     *
+     * @return array
+     */
+    function getGroupMemberSet() {
+
+        return $this->principalBackend->getGroupMemberSet($this->getPrincipalUrl());
+
+    }
+
+    /**
+     * Returns the list of groups this principal is member of
+     *
+     * If this principal is a member of a (list of) groups, this function
+     * should return a list of principal uri's for it's members.
+     *
+     * @return array
+     */
+    function getGroupMembership() {
+
+        return $this->principalBackend->getGroupMembership($this->getPrincipalUrl());
+
+    }
+
+    /**
+     * Sets a list of group members
+     *
+     * If this principal is a group, this method sets all the group members.
+     * The list of members is always overwritten, never appended to.
+     *
+     * This method should throw an exception if the members could not be set.
+     *
+     * @param array $principals
+     * @return void
+     */
+    function setGroupMemberSet(array $principals) {
+
+        $this->principalBackend->setGroupMemberSet($this->getPrincipalUrl(), $principals);
+
+    }
+
+    /**
+     * Returns the displayname
+     *
+     * This should be a human readable name for the principal.
+     * If none is available, return the nodename.
+     *
+     * @return string
+     */
+    function getDisplayName() {
+
+        return $this->getName();
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Principal/ProxyWrite.php b/vendor/sabre/dav/lib/CalDAV/Principal/ProxyWrite.php
new file mode 100644
index 000000000..8124c05e0
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Principal/ProxyWrite.php
@@ -0,0 +1,181 @@
+<?php
+
+namespace Sabre\CalDAV\Principal;
+
+use Sabre\DAVACL;
+use Sabre\DAV;
+
+/**
+ * ProxyWrite principal
+ *
+ * This class represents a principal group, hosted under the main principal.
+ * This is needed to implement 'Calendar delegation' support. This class is
+ * instantiated by User.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class ProxyWrite implements IProxyWrite {
+
+    /**
+     * Parent principal information
+     *
+     * @var array
+     */
+    protected $principalInfo;
+
+    /**
+     * Principal Backend
+     *
+     * @var DAVACL\PrincipalBackend\BackendInterface
+     */
+    protected $principalBackend;
+
+    /**
+     * Creates the object
+     *
+     * Note that you MUST supply the parent principal information.
+     *
+     * @param DAVACL\PrincipalBackend\BackendInterface $principalBackend
+     * @param array $principalInfo
+     */
+    function __construct(DAVACL\PrincipalBackend\BackendInterface $principalBackend, array $principalInfo) {
+
+        $this->principalInfo = $principalInfo;
+        $this->principalBackend = $principalBackend;
+
+    }
+
+    /**
+     * Returns this principals name.
+     *
+     * @return string
+     */
+    function getName() {
+
+        return 'calendar-proxy-write';
+
+    }
+
+    /**
+     * Returns the last modification time
+     *
+     * @return null
+     */
+    function getLastModified() {
+
+        return null;
+
+    }
+
+    /**
+     * Deletes the current node
+     *
+     * @throws DAV\Exception\Forbidden
+     * @return void
+     */
+    function delete() {
+
+        throw new DAV\Exception\Forbidden('Permission denied to delete node');
+
+    }
+
+    /**
+     * Renames the node
+     *
+     * @throws DAV\Exception\Forbidden
+     * @param string $name The new name
+     * @return void
+     */
+    function setName($name) {
+
+        throw new DAV\Exception\Forbidden('Permission denied to rename file');
+
+    }
+
+
+    /**
+     * Returns a list of alternative urls for a principal
+     *
+     * This can for example be an email address, or ldap url.
+     *
+     * @return array
+     */
+    function getAlternateUriSet() {
+
+        return [];
+
+    }
+
+    /**
+     * Returns the full principal url
+     *
+     * @return string
+     */
+    function getPrincipalUrl() {
+
+        return $this->principalInfo['uri'] . '/' . $this->getName();
+
+    }
+
+    /**
+     * Returns the list of group members
+     *
+     * If this principal is a group, this function should return
+     * all member principal uri's for the group.
+     *
+     * @return array
+     */
+    function getGroupMemberSet() {
+
+        return $this->principalBackend->getGroupMemberSet($this->getPrincipalUrl());
+
+    }
+
+    /**
+     * Returns the list of groups this principal is member of
+     *
+     * If this principal is a member of a (list of) groups, this function
+     * should return a list of principal uri's for it's members.
+     *
+     * @return array
+     */
+    function getGroupMembership() {
+
+        return $this->principalBackend->getGroupMembership($this->getPrincipalUrl());
+
+    }
+
+    /**
+     * Sets a list of group members
+     *
+     * If this principal is a group, this method sets all the group members.
+     * The list of members is always overwritten, never appended to.
+     *
+     * This method should throw an exception if the members could not be set.
+     *
+     * @param array $principals
+     * @return void
+     */
+    function setGroupMemberSet(array $principals) {
+
+        $this->principalBackend->setGroupMemberSet($this->getPrincipalUrl(), $principals);
+
+    }
+
+    /**
+     * Returns the displayname
+     *
+     * This should be a human readable name for the principal.
+     * If none is available, return the nodename.
+     *
+     * @return string
+     */
+    function getDisplayName() {
+
+        return $this->getName();
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Principal/User.php b/vendor/sabre/dav/lib/CalDAV/Principal/User.php
new file mode 100644
index 000000000..6e97e7cca
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Principal/User.php
@@ -0,0 +1,135 @@
+<?php
+
+namespace Sabre\CalDAV\Principal;
+
+use Sabre\DAV;
+use Sabre\DAVACL;
+
+/**
+ * CalDAV principal
+ *
+ * This is a standard user-principal for CalDAV. This principal is also a
+ * collection and returns the caldav-proxy-read and caldav-proxy-write child
+ * principals.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class User extends DAVACL\Principal implements DAV\ICollection {
+
+    /**
+     * Creates a new file in the directory
+     *
+     * @param string $name Name of the file
+     * @param resource $data Initial payload, passed as a readable stream resource.
+     * @throws DAV\Exception\Forbidden
+     * @return void
+     */
+    function createFile($name, $data = null) {
+
+        throw new DAV\Exception\Forbidden('Permission denied to create file (filename ' . $name . ')');
+
+    }
+
+    /**
+     * Creates a new subdirectory
+     *
+     * @param string $name
+     * @throws DAV\Exception\Forbidden
+     * @return void
+     */
+    function createDirectory($name) {
+
+        throw new DAV\Exception\Forbidden('Permission denied to create directory');
+
+    }
+
+    /**
+     * Returns a specific child node, referenced by its name
+     *
+     * @param string $name
+     * @return DAV\INode
+     */
+    function getChild($name) {
+
+        $principal = $this->principalBackend->getPrincipalByPath($this->getPrincipalURL() . '/' . $name);
+        if (!$principal) {
+            throw new DAV\Exception\NotFound('Node with name ' . $name . ' was not found');
+        }
+        if ($name === 'calendar-proxy-read')
+            return new ProxyRead($this->principalBackend, $this->principalProperties);
+
+        if ($name === 'calendar-proxy-write')
+            return new ProxyWrite($this->principalBackend, $this->principalProperties);
+
+        throw new DAV\Exception\NotFound('Node with name ' . $name . ' was not found');
+
+    }
+
+    /**
+     * Returns an array with all the child nodes
+     *
+     * @return DAV\INode[]
+     */
+    function getChildren() {
+
+        $r = [];
+        if ($this->principalBackend->getPrincipalByPath($this->getPrincipalURL() . '/calendar-proxy-read')) {
+            $r[] = new ProxyRead($this->principalBackend, $this->principalProperties);
+        }
+        if ($this->principalBackend->getPrincipalByPath($this->getPrincipalURL() . '/calendar-proxy-write')) {
+            $r[] = new ProxyWrite($this->principalBackend, $this->principalProperties);
+        }
+
+        return $r;
+
+    }
+
+    /**
+     * Returns whether or not the child node exists
+     *
+     * @param string $name
+     * @return bool
+     */
+    function childExists($name) {
+
+        try {
+            $this->getChild($name);
+            return true;
+        } catch (DAV\Exception\NotFound $e) {
+            return false;
+        }
+
+    }
+
+    /**
+     * Returns a list of ACE's for this node.
+     *
+     * Each ACE has the following properties:
+     *   * 'privilege', a string such as {DAV:}read or {DAV:}write. These are
+     *     currently the only supported privileges
+     *   * 'principal', a url to the principal who owns the node
+     *   * 'protected' (optional), indicating that this ACE is not allowed to
+     *      be updated.
+     *
+     * @return array
+     */
+    function getACL() {
+
+        $acl = parent::getACL();
+        $acl[] = [
+            'privilege' => '{DAV:}read',
+            'principal' => $this->principalProperties['uri'] . '/calendar-proxy-read',
+            'protected' => true,
+        ];
+        $acl[] = [
+            'privilege' => '{DAV:}read',
+            'principal' => $this->principalProperties['uri'] . '/calendar-proxy-write',
+            'protected' => true,
+        ];
+        return $acl;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Schedule/IInbox.php b/vendor/sabre/dav/lib/CalDAV/Schedule/IInbox.php
new file mode 100644
index 000000000..c9fd77d93
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Schedule/IInbox.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Sabre\CalDAV\Schedule;
+
+/**
+ * Implement this interface to have a node be recognized as a CalDAV scheduling
+ * inbox.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface IInbox extends \Sabre\CalDAV\ICalendarObjectContainer, \Sabre\DAVACL\IACL {
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Schedule/IMipPlugin.php b/vendor/sabre/dav/lib/CalDAV/Schedule/IMipPlugin.php
new file mode 100644
index 000000000..ffb1fe45b
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Schedule/IMipPlugin.php
@@ -0,0 +1,190 @@
+<?php
+
+namespace Sabre\CalDAV\Schedule;
+
+use Sabre\DAV;
+use Sabre\VObject\ITip;
+
+/**
+ * iMIP handler.
+ *
+ * This class is responsible for sending out iMIP messages. iMIP is the
+ * email-based transport for iTIP. iTIP deals with scheduling operations for
+ * iCalendar objects.
+ *
+ * If you want to customize the email that gets sent out, you can do so by
+ * extending this class and overriding the sendMessage method.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class IMipPlugin extends DAV\ServerPlugin {
+
+    /**
+     * Email address used in From: header.
+     *
+     * @var string
+     */
+    protected $senderEmail;
+
+    /**
+     * ITipMessage
+     *
+     * @var ITip\Message
+     */
+    protected $itipMessage;
+
+    /**
+     * Creates the email handler.
+     *
+     * @param string $senderEmail. The 'senderEmail' is the email that shows up
+     *                             in the 'From:' address. This should
+     *                             generally be some kind of no-reply email
+     *                             address you own.
+     */
+    function __construct($senderEmail) {
+
+        $this->senderEmail = $senderEmail;
+
+    }
+
+    /*
+     * This initializes the plugin.
+     *
+     * This function is called by Sabre\DAV\Server, after
+     * addPlugin is called.
+     *
+     * This method should set up the required event subscriptions.
+     *
+     * @param DAV\Server $server
+     * @return void
+     */
+    function initialize(DAV\Server $server) {
+
+        $server->on('schedule', [$this, 'schedule'], 120);
+
+    }
+
+    /**
+     * Returns a plugin name.
+     *
+     * Using this name other plugins will be able to access other plugins
+     * using \Sabre\DAV\Server::getPlugin
+     *
+     * @return string
+     */
+    function getPluginName() {
+
+        return 'imip';
+
+    }
+
+    /**
+     * Event handler for the 'schedule' event.
+     *
+     * @param ITip\Message $iTipMessage
+     * @return void
+     */
+    function schedule(ITip\Message $iTipMessage) {
+
+        // Not sending any emails if the system considers the update
+        // insignificant.
+        if (!$iTipMessage->significantChange) {
+            if (!$iTipMessage->scheduleStatus) {
+                $iTipMessage->scheduleStatus = '1.0;We got the message, but it\'s not significant enough to warrant an email';
+            }
+            return;
+        }
+
+        $summary = $iTipMessage->message->VEVENT->SUMMARY;
+
+        if (parse_url($iTipMessage->sender, PHP_URL_SCHEME) !== 'mailto')
+            return;
+
+        if (parse_url($iTipMessage->recipient, PHP_URL_SCHEME) !== 'mailto')
+            return;
+
+        $sender = substr($iTipMessage->sender, 7);
+        $recipient = substr($iTipMessage->recipient, 7);
+
+        if ($iTipMessage->senderName) {
+            $sender = $iTipMessage->senderName . ' <' . $sender . '>';
+        }
+        if ($iTipMessage->recipientName) {
+            $recipient = $iTipMessage->recipientName . ' <' . $recipient . '>';
+        }
+
+        $subject = 'SabreDAV iTIP message';
+        switch (strtoupper($iTipMessage->method)) {
+            case 'REPLY' :
+                $subject = 'Re: ' . $summary;
+                break;
+            case 'REQUEST' :
+                $subject = $summary;
+                break;
+            case 'CANCEL' :
+                $subject = 'Cancelled: ' . $summary;
+                break;
+        }
+
+        $headers = [
+            'Reply-To: ' . $sender,
+            'From: ' . $this->senderEmail,
+            'Content-Type: text/calendar; charset=UTF-8; method=' . $iTipMessage->method,
+        ];
+        if (DAV\Server::$exposeVersion) {
+            $headers[] = 'X-Sabre-Version: ' . DAV\Version::VERSION;
+        }
+        $this->mail(
+            $recipient,
+            $subject,
+            $iTipMessage->message->serialize(),
+            $headers
+        );
+        $iTipMessage->scheduleStatus = '1.1; Scheduling message is sent via iMip';
+
+    }
+
+    // @codeCoverageIgnoreStart
+    // This is deemed untestable in a reasonable manner
+
+    /**
+     * This function is responsible for sending the actual email.
+     *
+     * @param string $to Recipient email address
+     * @param string $subject Subject of the email
+     * @param string $body iCalendar body
+     * @param array $headers List of headers
+     * @return void
+     */
+    protected function mail($to, $subject, $body, array $headers) {
+
+        mail($to, $subject, $body, implode("\r\n", $headers));
+
+    }
+
+    // @codeCoverageIgnoreEnd
+
+    /**
+     * Returns a bunch of meta-data about the plugin.
+     *
+     * Providing this information is optional, and is mainly displayed by the
+     * Browser plugin.
+     *
+     * The description key in the returned array may contain html and will not
+     * be sanitized.
+     *
+     * @return array
+     */
+    function getPluginInfo() {
+
+        return [
+            'name'        => $this->getPluginName(),
+            'description' => 'Email delivery (rfc6037) for CalDAV scheduling',
+            'link'        => 'http://sabre.io/dav/scheduling/',
+        ];
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Schedule/IOutbox.php b/vendor/sabre/dav/lib/CalDAV/Schedule/IOutbox.php
new file mode 100644
index 000000000..88fbdc411
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Schedule/IOutbox.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Sabre\CalDAV\Schedule;
+
+/**
+ * Implement this interface to have a node be recognized as a CalDAV scheduling
+ * outbox.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface IOutbox extends \Sabre\DAV\ICollection, \Sabre\DAVACL\IACL {
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Schedule/ISchedulingObject.php b/vendor/sabre/dav/lib/CalDAV/Schedule/ISchedulingObject.php
new file mode 100644
index 000000000..b37cb40a1
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Schedule/ISchedulingObject.php
@@ -0,0 +1,13 @@
+<?php
+
+namespace Sabre\CalDAV\Schedule;
+
+/**
+ * The SchedulingObject represents a scheduling object in the Inbox collection
+ *
+ * @license http://sabre.io/license/ Modified BSD License
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ */
+interface ISchedulingObject extends \Sabre\CalDAV\ICalendarObject {
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Schedule/Inbox.php b/vendor/sabre/dav/lib/CalDAV/Schedule/Inbox.php
new file mode 100644
index 000000000..13212565e
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Schedule/Inbox.php
@@ -0,0 +1,261 @@
+<?php
+
+namespace Sabre\CalDAV\Schedule;
+
+use Sabre\DAV;
+use Sabre\CalDAV;
+use Sabre\DAVACL;
+use Sabre\CalDAV\Backend;
+use Sabre\VObject;
+
+/**
+ * The CalDAV scheduling inbox
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Inbox extends DAV\Collection implements IInbox {
+
+    /**
+     * CalDAV backend
+     *
+     * @var Backend\BackendInterface
+     */
+    protected $caldavBackend;
+
+    /**
+     * The principal Uri
+     *
+     * @var string
+     */
+    protected $principalUri;
+
+    /**
+     * Constructor
+     *
+     * @param Backend\SchedulingSupport $caldavBackend
+     * @param string $principalUri
+     */
+    function __construct(Backend\SchedulingSupport $caldavBackend, $principalUri) {
+
+        $this->caldavBackend = $caldavBackend;
+        $this->principalUri = $principalUri;
+
+    }
+
+    /**
+     * Returns the name of the node.
+     *
+     * This is used to generate the url.
+     *
+     * @return string
+     */
+    function getName() {
+
+        return 'inbox';
+
+    }
+
+    /**
+     * Returns an array with all the child nodes
+     *
+     * @return \Sabre\DAV\INode[]
+     */
+    function getChildren() {
+
+        $objs = $this->caldavBackend->getSchedulingObjects($this->principalUri);
+        $children = [];
+        foreach ($objs as $obj) {
+            //$obj['acl'] = $this->getACL();
+            $obj['principaluri'] = $this->principalUri;
+            $children[] = new SchedulingObject($this->caldavBackend, $obj);
+        }
+        return $children;
+
+    }
+
+    /**
+     * Creates a new file in the directory
+     *
+     * Data will either be supplied as a stream resource, or in certain cases
+     * as a string. Keep in mind that you may have to support either.
+     *
+     * After succesful creation of the file, you may choose to return the ETag
+     * of the new file here.
+     *
+     * The returned ETag must be surrounded by double-quotes (The quotes should
+     * be part of the actual string).
+     *
+     * If you cannot accurately determine the ETag, you should not return it.
+     * If you don't store the file exactly as-is (you're transforming it
+     * somehow) you should also not return an ETag.
+     *
+     * This means that if a subsequent GET to this new file does not exactly
+     * return the same contents of what was submitted here, you are strongly
+     * recommended to omit the ETag.
+     *
+     * @param string $name Name of the file
+     * @param resource|string $data Initial payload
+     * @return null|string
+     */
+    function createFile($name, $data = null) {
+
+        $this->caldavBackend->createSchedulingObject($this->principalUri, $name, $data);
+
+    }
+
+    /**
+     * Returns the owner principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getOwner() {
+
+        return $this->principalUri;
+
+    }
+
+    /**
+     * Returns a group principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getGroup() {
+
+        return null;
+
+    }
+
+    /**
+     * Returns a list of ACE's for this node.
+     *
+     * Each ACE has the following properties:
+     *   * 'privilege', a string such as {DAV:}read or {DAV:}write. These are
+     *     currently the only supported privileges
+     *   * 'principal', a url to the principal who owns the node
+     *   * 'protected' (optional), indicating that this ACE is not allowed to
+     *      be updated.
+     *
+     * @return array
+     */
+    function getACL() {
+
+        return [
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => '{DAV:}authenticated',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}write-properties',
+                'principal' => $this->getOwner(),
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}unbind',
+                'principal' => $this->getOwner(),
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}unbind',
+                'principal' => $this->getOwner() . '/calendar-proxy-write',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{' . CalDAV\Plugin::NS_CALDAV . '}schedule-deliver-invite',
+                'principal' => '{DAV:}authenticated',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{' . CalDAV\Plugin::NS_CALDAV . '}schedule-deliver-reply',
+                'principal' => '{DAV:}authenticated',
+                'protected' => true,
+            ],
+        ];
+
+    }
+
+    /**
+     * Updates the ACL
+     *
+     * This method will receive a list of new ACE's.
+     *
+     * @param array $acl
+     * @return void
+     */
+    function setACL(array $acl) {
+
+        throw new DAV\Exception\MethodNotAllowed('You\'re not allowed to update the ACL');
+
+    }
+
+    /**
+     * Returns the list of supported privileges for this node.
+     *
+     * The returned data structure is a list of nested privileges.
+     * See Sabre\DAVACL\Plugin::getDefaultSupportedPrivilegeSet for a simple
+     * standard structure.
+     *
+     * If null is returned from this method, the default privilege set is used,
+     * which is fine for most common usecases.
+     *
+     * @return array|null
+     */
+    function getSupportedPrivilegeSet() {
+
+        $ns = '{' . CalDAV\Plugin::NS_CALDAV . '}';
+
+        $default = DAVACL\Plugin::getDefaultSupportedPrivilegeSet();
+        $default['aggregates'][] = [
+            'privilege'  => $ns . 'schedule-deliver',
+            'aggregates' => [
+               ['privilege' => $ns . 'schedule-deliver-invite'],
+               ['privilege' => $ns . 'schedule-deliver-reply'],
+            ],
+        ];
+        return $default;
+
+    }
+
+    /**
+     * Performs a calendar-query on the contents of this calendar.
+     *
+     * The calendar-query is defined in RFC4791 : CalDAV. Using the
+     * calendar-query it is possible for a client to request a specific set of
+     * object, based on contents of iCalendar properties, date-ranges and
+     * iCalendar component types (VTODO, VEVENT).
+     *
+     * This method should just return a list of (relative) urls that match this
+     * query.
+     *
+     * The list of filters are specified as an array. The exact array is
+     * documented by \Sabre\CalDAV\CalendarQueryParser.
+     *
+     * @param array $filters
+     * @return array
+     */
+    function calendarQuery(array $filters) {
+
+        $result = [];
+        $validator = new CalDAV\CalendarQueryValidator();
+
+        $objects = $this->caldavBackend->getSchedulingObjects($this->principalUri);
+        foreach ($objects as $object) {
+            $vObject = VObject\Reader::read($object['calendardata']);
+            if ($validator->validate($vObject, $filters)) {
+                $result[] = $object['uri'];
+            }
+
+            // Destroy circular references to PHP will GC the object.
+            $vObject->destroy();
+        }
+        return $result;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Schedule/Outbox.php b/vendor/sabre/dav/lib/CalDAV/Schedule/Outbox.php
new file mode 100644
index 000000000..dabaee2ca
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Schedule/Outbox.php
@@ -0,0 +1,184 @@
+<?php
+
+namespace Sabre\CalDAV\Schedule;
+
+use Sabre\DAV;
+use Sabre\CalDAV;
+use Sabre\DAVACL;
+
+/**
+ * The CalDAV scheduling outbox
+ *
+ * The outbox is mainly used as an endpoint in the tree for a client to do
+ * free-busy requests. This functionality is completely handled by the
+ * Scheduling plugin, so this object is actually mostly static.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Outbox extends DAV\Collection implements IOutbox {
+
+    /**
+     * The principal Uri
+     *
+     * @var string
+     */
+    protected $principalUri;
+
+    /**
+     * Constructor
+     *
+     * @param string $principalUri
+     */
+    function __construct($principalUri) {
+
+        $this->principalUri = $principalUri;
+
+    }
+
+    /**
+     * Returns the name of the node.
+     *
+     * This is used to generate the url.
+     *
+     * @return string
+     */
+    function getName() {
+
+        return 'outbox';
+
+    }
+
+    /**
+     * Returns an array with all the child nodes
+     *
+     * @return \Sabre\DAV\INode[]
+     */
+    function getChildren() {
+
+        return [];
+
+    }
+
+    /**
+     * Returns the owner principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getOwner() {
+
+        return $this->principalUri;
+
+    }
+
+    /**
+     * Returns a group principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getGroup() {
+
+        return null;
+
+    }
+
+    /**
+     * Returns a list of ACE's for this node.
+     *
+     * Each ACE has the following properties:
+     *   * 'privilege', a string such as {DAV:}read or {DAV:}write. These are
+     *     currently the only supported privileges
+     *   * 'principal', a url to the principal who owns the node
+     *   * 'protected' (optional), indicating that this ACE is not allowed to
+     *      be updated.
+     *
+     * @return array
+     */
+    function getACL() {
+
+        return [
+            [
+                'privilege' => '{' . CalDAV\Plugin::NS_CALDAV . '}schedule-query-freebusy',
+                'principal' => $this->getOwner(),
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{' . CalDAV\Plugin::NS_CALDAV . '}schedule-post-vevent',
+                'principal' => $this->getOwner(),
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->getOwner(),
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{' . CalDAV\Plugin::NS_CALDAV . '}schedule-query-freebusy',
+                'principal' => $this->getOwner() . '/calendar-proxy-write',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{' . CalDAV\Plugin::NS_CALDAV . '}schedule-post-vevent',
+                'principal' => $this->getOwner() . '/calendar-proxy-write',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->getOwner() . '/calendar-proxy-read',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->getOwner() . '/calendar-proxy-write',
+                'protected' => true,
+            ],
+        ];
+
+    }
+
+    /**
+     * Updates the ACL
+     *
+     * This method will receive a list of new ACE's.
+     *
+     * @param array $acl
+     * @return void
+     */
+    function setACL(array $acl) {
+
+        throw new DAV\Exception\MethodNotAllowed('You\'re not allowed to update the ACL');
+
+    }
+
+    /**
+     * Returns the list of supported privileges for this node.
+     *
+     * The returned data structure is a list of nested privileges.
+     * See Sabre\DAVACL\Plugin::getDefaultSupportedPrivilegeSet for a simple
+     * standard structure.
+     *
+     * If null is returned from this method, the default privilege set is used,
+     * which is fine for most common usecases.
+     *
+     * @return array|null
+     */
+    function getSupportedPrivilegeSet() {
+
+        $default = DAVACL\Plugin::getDefaultSupportedPrivilegeSet();
+        $default['aggregates'][] = [
+            'privilege' => '{' . CalDAV\Plugin::NS_CALDAV . '}schedule-query-freebusy',
+        ];
+        $default['aggregates'][] = [
+            'privilege' => '{' . CalDAV\Plugin::NS_CALDAV . '}schedule-post-vevent',
+        ];
+
+        return $default;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Schedule/Plugin.php b/vendor/sabre/dav/lib/CalDAV/Schedule/Plugin.php
new file mode 100644
index 000000000..827d6209b
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Schedule/Plugin.php
@@ -0,0 +1,994 @@
+<?php
+
+namespace Sabre\CalDAV\Schedule;
+
+use DateTimeZone;
+use Sabre\DAV\Server;
+use Sabre\DAV\ServerPlugin;
+use Sabre\DAV\PropFind;
+use Sabre\DAV\PropPatch;
+use Sabre\DAV\INode;
+use Sabre\DAV\Xml\Property\Href;
+use Sabre\HTTP\RequestInterface;
+use Sabre\HTTP\ResponseInterface;
+use Sabre\VObject;
+use Sabre\VObject\Reader;
+use Sabre\VObject\Component\VCalendar;
+use Sabre\VObject\ITip;
+use Sabre\VObject\ITip\Message;
+use Sabre\DAVACL;
+use Sabre\CalDAV\ICalendar;
+use Sabre\CalDAV\ICalendarObject;
+use Sabre\CalDAV\Xml\Property\ScheduleCalendarTransp;
+use Sabre\DAV\Exception\NotFound;
+use Sabre\DAV\Exception\Forbidden;
+use Sabre\DAV\Exception\BadRequest;
+use Sabre\DAV\Exception\NotImplemented;
+
+/**
+ * CalDAV scheduling plugin.
+ * =========================
+ *
+ * This plugin provides the functionality added by the "Scheduling Extensions
+ * to CalDAV" standard, as defined in RFC6638.
+ *
+ * calendar-auto-schedule largely works by intercepting a users request to
+ * update their local calendar. If a user creates a new event with attendees,
+ * this plugin is supposed to grab the information from that event, and notify
+ * the attendees of this.
+ *
+ * There's 3 possible transports for this:
+ * * local delivery
+ * * delivery through email (iMip)
+ * * server-to-server delivery (iSchedule)
+ *
+ * iMip is simply, because we just need to add the iTip message as an email
+ * attachment. Local delivery is harder, because we both need to add this same
+ * message to a local DAV inbox, as well as live-update the relevant events.
+ *
+ * iSchedule is something for later.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Plugin extends ServerPlugin {
+
+    /**
+     * This is the official CalDAV namespace
+     */
+    const NS_CALDAV = 'urn:ietf:params:xml:ns:caldav';
+
+    /**
+     * Reference to main Server object.
+     *
+     * @var Server
+     */
+    protected $server;
+
+    /**
+     * Returns a list of features for the DAV: HTTP header.
+     *
+     * @return array
+     */
+    function getFeatures() {
+
+        return ['calendar-auto-schedule', 'calendar-availability'];
+
+    }
+
+    /**
+     * Returns the name of the plugin.
+     *
+     * Using this name other plugins will be able to access other plugins
+     * using Server::getPlugin
+     *
+     * @return string
+     */
+    function getPluginName() {
+
+        return 'caldav-schedule';
+
+    }
+
+    /**
+     * Initializes the plugin
+     *
+     * @param Server $server
+     * @return void
+     */
+    function initialize(Server $server) {
+
+        $this->server = $server;
+        $server->on('method:POST',          [$this, 'httpPost']);
+        $server->on('propFind',             [$this, 'propFind']);
+        $server->on('propPatch',            [$this, 'propPatch']);
+        $server->on('calendarObjectChange', [$this, 'calendarObjectChange']);
+        $server->on('beforeUnbind',         [$this, 'beforeUnbind']);
+        $server->on('schedule',             [$this, 'scheduleLocalDelivery']);
+
+        $ns = '{' . self::NS_CALDAV . '}';
+
+        /**
+         * This information ensures that the {DAV:}resourcetype property has
+         * the correct values.
+         */
+        $server->resourceTypeMapping['\\Sabre\\CalDAV\\Schedule\\IOutbox'] = $ns . 'schedule-outbox';
+        $server->resourceTypeMapping['\\Sabre\\CalDAV\\Schedule\\IInbox'] = $ns . 'schedule-inbox';
+
+        /**
+         * Properties we protect are made read-only by the server.
+         */
+        array_push($server->protectedProperties,
+            $ns . 'schedule-inbox-URL',
+            $ns . 'schedule-outbox-URL',
+            $ns . 'calendar-user-address-set',
+            $ns . 'calendar-user-type',
+            $ns . 'schedule-default-calendar-URL'
+        );
+
+    }
+
+    /**
+     * Use this method to tell the server this plugin defines additional
+     * HTTP methods.
+     *
+     * This method is passed a uri. It should only return HTTP methods that are
+     * available for the specified uri.
+     *
+     * @param string $uri
+     * @return array
+     */
+    function getHTTPMethods($uri) {
+
+        try {
+            $node = $this->server->tree->getNodeForPath($uri);
+        } catch (NotFound $e) {
+            return [];
+        }
+
+        if ($node instanceof IOutbox) {
+            return ['POST'];
+        }
+
+        return [];
+
+    }
+
+    /**
+     * This method handles POST request for the outbox.
+     *
+     * @param RequestInterface $request
+     * @param ResponseInterface $response
+     * @return bool
+     */
+    function httpPost(RequestInterface $request, ResponseInterface $response) {
+
+        // Checking if this is a text/calendar content type
+        $contentType = $request->getHeader('Content-Type');
+        if (strpos($contentType, 'text/calendar') !== 0) {
+            return;
+        }
+
+        $path = $request->getPath();
+
+        // Checking if we're talking to an outbox
+        try {
+            $node = $this->server->tree->getNodeForPath($path);
+        } catch (NotFound $e) {
+            return;
+        }
+        if (!$node instanceof IOutbox)
+            return;
+
+        $this->server->transactionType = 'post-caldav-outbox';
+        $this->outboxRequest($node, $request, $response);
+
+        // Returning false breaks the event chain and tells the server we've
+        // handled the request.
+        return false;
+
+    }
+
+    /**
+     * This method handler is invoked during fetching of properties.
+     *
+     * We use this event to add calendar-auto-schedule-specific properties.
+     *
+     * @param PropFind $propFind
+     * @param INode $node
+     * @return void
+     */
+    function propFind(PropFind $propFind, INode $node) {
+
+        if ($node instanceof DAVACL\IPrincipal) {
+
+            $caldavPlugin = $this->server->getPlugin('caldav');
+            $principalUrl = $node->getPrincipalUrl();
+
+            // schedule-outbox-URL property
+            $propFind->handle('{' . self::NS_CALDAV . '}schedule-outbox-URL', function() use ($principalUrl, $caldavPlugin) {
+
+                $calendarHomePath = $caldavPlugin->getCalendarHomeForPrincipal($principalUrl);
+                if (!$calendarHomePath) {
+                    return null;
+                }
+                $outboxPath = $calendarHomePath . '/outbox/';
+
+                return new Href($outboxPath);
+
+            });
+            // schedule-inbox-URL property
+            $propFind->handle('{' . self::NS_CALDAV . '}schedule-inbox-URL', function() use ($principalUrl, $caldavPlugin) {
+
+                $calendarHomePath = $caldavPlugin->getCalendarHomeForPrincipal($principalUrl);
+                if (!$calendarHomePath) {
+                    return null;
+                }
+                $inboxPath = $calendarHomePath . '/inbox/';
+
+                return new Href($inboxPath);
+
+            });
+
+            $propFind->handle('{' . self::NS_CALDAV . '}schedule-default-calendar-URL', function() use ($principalUrl, $caldavPlugin) {
+
+                // We don't support customizing this property yet, so in the
+                // meantime we just grab the first calendar in the home-set.
+                $calendarHomePath = $caldavPlugin->getCalendarHomeForPrincipal($principalUrl);
+
+                if (!$calendarHomePath) {
+                    return null;
+                }
+
+                $sccs = '{' . self::NS_CALDAV . '}supported-calendar-component-set';
+
+                $result = $this->server->getPropertiesForPath($calendarHomePath, [
+                    '{DAV:}resourcetype',
+                    $sccs,
+                ], 1);
+
+                foreach ($result as $child) {
+                    if (!isset($child[200]['{DAV:}resourcetype']) || !$child[200]['{DAV:}resourcetype']->is('{' . self::NS_CALDAV . '}calendar') || $child[200]['{DAV:}resourcetype']->is('{http://calendarserver.org/ns/}shared')) {
+                        // Node is either not a calendar or a shared instance.
+                        continue;
+                    }
+                    if (!isset($child[200][$sccs]) || in_array('VEVENT', $child[200][$sccs]->getValue())) {
+                        // Either there is no supported-calendar-component-set
+                        // (which is fine) or we found one that supports VEVENT.
+                        return new Href($child['href']);
+                    }
+                }
+
+            });
+
+            // The server currently reports every principal to be of type
+            // 'INDIVIDUAL'
+            $propFind->handle('{' . self::NS_CALDAV . '}calendar-user-type', function() {
+
+                return 'INDIVIDUAL';
+
+            });
+
+        }
+
+        // Mapping the old property to the new property.
+        $propFind->handle('{http://calendarserver.org/ns/}calendar-availability', function() use ($propFind, $node) {
+
+             // In case it wasn't clear, the only difference is that we map the
+            // old property to a different namespace.
+             $availProp = '{' . self::NS_CALDAV . '}calendar-availability';
+             $subPropFind = new PropFind(
+                 $propFind->getPath(),
+                 [$availProp]
+             );
+
+             $this->server->getPropertiesByNode(
+                 $subPropFind,
+                 $node
+             );
+
+             $propFind->set(
+                 '{http://calendarserver.org/ns/}calendar-availability',
+                 $subPropFind->get($availProp),
+                 $subPropFind->getStatus($availProp)
+             );
+
+        });
+
+    }
+
+    /**
+     * This method is called during property updates.
+     *
+     * @param string $path
+     * @param PropPatch $propPatch
+     * @return void
+     */
+    function propPatch($path, PropPatch $propPatch) {
+
+        // Mapping the old property to the new property.
+        $propPatch->handle('{http://calendarserver.org/ns/}calendar-availability', function($value) use ($path) {
+
+            $availProp = '{' . self::NS_CALDAV . '}calendar-availability';
+            $subPropPatch = new PropPatch([$availProp => $value]);
+            $this->server->emit('propPatch', [$path, $subPropPatch]);
+            $subPropPatch->commit();
+
+            return $subPropPatch->getResult()[$availProp];
+
+        });
+
+    }
+
+    /**
+     * This method is triggered whenever there was a calendar object gets
+     * created or updated.
+     *
+     * @param RequestInterface $request HTTP request
+     * @param ResponseInterface $response HTTP Response
+     * @param VCalendar $vCal Parsed iCalendar object
+     * @param mixed $calendarPath Path to calendar collection
+     * @param mixed $modified The iCalendar object has been touched.
+     * @param mixed $isNew Whether this was a new item or we're updating one
+     * @return void
+     */
+    function calendarObjectChange(RequestInterface $request, ResponseInterface $response, VCalendar $vCal, $calendarPath, &$modified, $isNew) {
+
+        if (!$this->scheduleReply($this->server->httpRequest)) {
+            return;
+        }
+
+        $calendarNode = $this->server->tree->getNodeForPath($calendarPath);
+
+        $addresses = $this->getAddressesForPrincipal(
+            $calendarNode->getOwner()
+        );
+
+        if (!$isNew) {
+            $node = $this->server->tree->getNodeForPath($request->getPath());
+            $oldObj = Reader::read($node->get());
+        } else {
+            $oldObj = null;
+        }
+
+        $this->processICalendarChange($oldObj, $vCal, $addresses, [], $modified);
+
+        if ($oldObj) {
+            // Destroy circular references so PHP will GC the object.
+            $oldObj->destroy();
+        }
+
+    }
+
+    /**
+     * This method is responsible for delivering the ITip message.
+     *
+     * @param ITip\Message $itipMessage
+     * @return void
+     */
+    function deliver(ITip\Message $iTipMessage) {
+
+        $this->server->emit('schedule', [$iTipMessage]);
+        if (!$iTipMessage->scheduleStatus) {
+            $iTipMessage->scheduleStatus = '5.2;There was no system capable of delivering the scheduling message';
+        }
+        // In case the change was considered 'insignificant', we are going to
+        // remove any error statuses, if any. See ticket #525.
+        list($baseCode) = explode('.', $iTipMessage->scheduleStatus);
+        if (!$iTipMessage->significantChange && in_array($baseCode, ['3', '5'])) {
+            $iTipMessage->scheduleStatus = null;
+        }
+
+    }
+
+    /**
+     * This method is triggered before a file gets deleted.
+     *
+     * We use this event to make sure that when this happens, attendees get
+     * cancellations, and organizers get 'DECLINED' statuses.
+     *
+     * @param string $path
+     * @return void
+     */
+    function beforeUnbind($path) {
+
+        // FIXME: We shouldn't trigger this functionality when we're issuing a
+        // MOVE. This is a hack.
+        if ($this->server->httpRequest->getMethod() === 'MOVE') return;
+
+        $node = $this->server->tree->getNodeForPath($path);
+
+        if (!$node instanceof ICalendarObject || $node instanceof ISchedulingObject) {
+            return;
+        }
+
+        if (!$this->scheduleReply($this->server->httpRequest)) {
+            return;
+        }
+
+        $addresses = $this->getAddressesForPrincipal(
+            $node->getOwner()
+        );
+
+        $broker = new ITip\Broker();
+        $messages = $broker->parseEvent(null, $addresses, $node->get());
+
+        foreach ($messages as $message) {
+            $this->deliver($message);
+        }
+
+    }
+
+    /**
+     * Event handler for the 'schedule' event.
+     *
+     * This handler attempts to look at local accounts to deliver the
+     * scheduling object.
+     *
+     * @param ITip\Message $iTipMessage
+     * @return void
+     */
+    function scheduleLocalDelivery(ITip\Message $iTipMessage) {
+
+        $aclPlugin = $this->server->getPlugin('acl');
+
+        // Local delivery is not available if the ACL plugin is not loaded.
+        if (!$aclPlugin) {
+            return;
+        }
+
+        $caldavNS = '{' . self::NS_CALDAV . '}';
+
+        $principalUri = $aclPlugin->getPrincipalByUri($iTipMessage->recipient);
+        if (!$principalUri) {
+            $iTipMessage->scheduleStatus = '3.7;Could not find principal.';
+            return;
+        }
+
+        // We found a principal URL, now we need to find its inbox.
+        // Unfortunately we may not have sufficient privileges to find this, so
+        // we are temporarily turning off ACL to let this come through.
+        //
+        // Once we support PHP 5.5, this should be wrapped in a try..finally
+        // block so we can ensure that this privilege gets added again after.
+        $this->server->removeListener('propFind', [$aclPlugin, 'propFind']);
+
+        $result = $this->server->getProperties(
+            $principalUri,
+            [
+                '{DAV:}principal-URL',
+                 $caldavNS . 'calendar-home-set',
+                 $caldavNS . 'schedule-inbox-URL',
+                 $caldavNS . 'schedule-default-calendar-URL',
+                '{http://sabredav.org/ns}email-address',
+            ]
+        );
+
+        // Re-registering the ACL event
+        $this->server->on('propFind', [$aclPlugin, 'propFind'], 20);
+
+        if (!isset($result[$caldavNS . 'schedule-inbox-URL'])) {
+            $iTipMessage->scheduleStatus = '5.2;Could not find local inbox';
+            return;
+        }
+        if (!isset($result[$caldavNS . 'calendar-home-set'])) {
+            $iTipMessage->scheduleStatus = '5.2;Could not locate a calendar-home-set';
+            return;
+        }
+        if (!isset($result[$caldavNS . 'schedule-default-calendar-URL'])) {
+            $iTipMessage->scheduleStatus = '5.2;Could not find a schedule-default-calendar-URL property';
+            return;
+        }
+
+        $calendarPath = $result[$caldavNS . 'schedule-default-calendar-URL']->getHref();
+        $homePath = $result[$caldavNS . 'calendar-home-set']->getHref();
+        $inboxPath = $result[$caldavNS . 'schedule-inbox-URL']->getHref();
+
+        if ($iTipMessage->method === 'REPLY') {
+            $privilege = 'schedule-deliver-reply';
+        } else {
+            $privilege = 'schedule-deliver-invite';
+        }
+
+        if (!$aclPlugin->checkPrivileges($inboxPath, $caldavNS . $privilege, DAVACL\Plugin::R_PARENT, false)) {
+            $iTipMessage->scheduleStatus = '3.8;organizer did not have the ' . $privilege . ' privilege on the attendees inbox';
+            return;
+        }
+
+        // Next, we're going to find out if the item already exits in one of
+        // the users' calendars.
+        $uid = $iTipMessage->uid;
+
+        $newFileName = 'sabredav-' . \Sabre\DAV\UUIDUtil::getUUID() . '.ics';
+
+        $home = $this->server->tree->getNodeForPath($homePath);
+        $inbox = $this->server->tree->getNodeForPath($inboxPath);
+
+        $currentObject = null;
+        $objectNode = null;
+        $isNewNode = false;
+
+        $result = $home->getCalendarObjectByUID($uid);
+        if ($result) {
+            // There was an existing object, we need to update probably.
+            $objectPath = $homePath . '/' . $result;
+            $objectNode = $this->server->tree->getNodeForPath($objectPath);
+            $oldICalendarData = $objectNode->get();
+            $currentObject = Reader::read($oldICalendarData);
+        } else {
+            $isNewNode = true;
+        }
+
+        $broker = new ITip\Broker();
+        $newObject = $broker->processMessage($iTipMessage, $currentObject);
+
+        $inbox->createFile($newFileName, $iTipMessage->message->serialize());
+
+        if (!$newObject) {
+            // We received an iTip message referring to a UID that we don't
+            // have in any calendars yet, and processMessage did not give us a
+            // calendarobject back.
+            //
+            // The implication is that processMessage did not understand the
+            // iTip message.
+            $iTipMessage->scheduleStatus = '5.0;iTip message was not processed by the server, likely because we didn\'t understand it.';
+            return;
+        }
+
+        // Note that we are bypassing ACL on purpose by calling this directly.
+        // We may need to look a bit deeper into this later. Supporting ACL
+        // here would be nice.
+        if ($isNewNode) {
+            $calendar = $this->server->tree->getNodeForPath($calendarPath);
+            $calendar->createFile($newFileName, $newObject->serialize());
+        } else {
+            // If the message was a reply, we may have to inform other
+            // attendees of this attendees status. Therefore we're shooting off
+            // another itipMessage.
+            if ($iTipMessage->method === 'REPLY') {
+                $this->processICalendarChange(
+                    $oldICalendarData,
+                    $newObject,
+                    [$iTipMessage->recipient],
+                    [$iTipMessage->sender]
+                );
+            }
+            $objectNode->put($newObject->serialize());
+        }
+        $iTipMessage->scheduleStatus = '1.2;Message delivered locally';
+
+    }
+
+    /**
+     * This method looks at an old iCalendar object, a new iCalendar object and
+     * starts sending scheduling messages based on the changes.
+     *
+     * A list of addresses needs to be specified, so the system knows who made
+     * the update, because the behavior may be different based on if it's an
+     * attendee or an organizer.
+     *
+     * This method may update $newObject to add any status changes.
+     *
+     * @param VCalendar|string $oldObject
+     * @param VCalendar $newObject
+     * @param array $addresses
+     * @param array $ignore Any addresses to not send messages to.
+     * @param bool $modified A marker to indicate that the original object
+     *   modified by this process.
+     * @return void
+     */
+    protected function processICalendarChange($oldObject = null, VCalendar $newObject, array $addresses, array $ignore = [], &$modified = false) {
+
+        $broker = new ITip\Broker();
+        $messages = $broker->parseEvent($newObject, $addresses, $oldObject);
+
+        if ($messages) $modified = true;
+
+        foreach ($messages as $message) {
+
+            if (in_array($message->recipient, $ignore)) {
+                continue;
+            }
+
+            $this->deliver($message);
+
+            if (isset($newObject->VEVENT->ORGANIZER) && ($newObject->VEVENT->ORGANIZER->getNormalizedValue() === $message->recipient)) {
+                if ($message->scheduleStatus) {
+                    $newObject->VEVENT->ORGANIZER['SCHEDULE-STATUS'] = $message->getScheduleStatus();
+                }
+                unset($newObject->VEVENT->ORGANIZER['SCHEDULE-FORCE-SEND']);
+
+            } else {
+
+                if (isset($newObject->VEVENT->ATTENDEE)) foreach ($newObject->VEVENT->ATTENDEE as $attendee) {
+
+                    if ($attendee->getNormalizedValue() === $message->recipient) {
+                        if ($message->scheduleStatus) {
+                            $attendee['SCHEDULE-STATUS'] = $message->getScheduleStatus();
+                        }
+                        unset($attendee['SCHEDULE-FORCE-SEND']);
+                        break;
+                    }
+
+                }
+
+            }
+
+        }
+
+    }
+
+    /**
+     * Returns a list of addresses that are associated with a principal.
+     *
+     * @param string $principal
+     * @return array
+     */
+    protected function getAddressesForPrincipal($principal) {
+
+        $CUAS = '{' . self::NS_CALDAV . '}calendar-user-address-set';
+
+        $properties = $this->server->getProperties(
+            $principal,
+            [$CUAS]
+        );
+
+        // If we can't find this information, we'll stop processing
+        if (!isset($properties[$CUAS])) {
+            return;
+        }
+
+        $addresses = $properties[$CUAS]->getHrefs();
+        return $addresses;
+
+    }
+
+    /**
+     * This method handles POST requests to the schedule-outbox.
+     *
+     * Currently, two types of requests are support:
+     *   * FREEBUSY requests from RFC 6638
+     *   * Simple iTIP messages from draft-desruisseaux-caldav-sched-04
+     *
+     * The latter is from an expired early draft of the CalDAV scheduling
+     * extensions, but iCal depends on a feature from that spec, so we
+     * implement it.
+     *
+     * @param IOutbox $outboxNode
+     * @param RequestInterface $request
+     * @param ResponseInterface $response
+     * @return void
+     */
+    function outboxRequest(IOutbox $outboxNode, RequestInterface $request, ResponseInterface $response) {
+
+        $outboxPath = $request->getPath();
+
+        // Parsing the request body
+        try {
+            $vObject = VObject\Reader::read($request->getBody());
+        } catch (VObject\ParseException $e) {
+            throw new BadRequest('The request body must be a valid iCalendar object. Parse error: ' . $e->getMessage());
+        }
+
+        // The incoming iCalendar object must have a METHOD property, and a
+        // component. The combination of both determines what type of request
+        // this is.
+        $componentType = null;
+        foreach ($vObject->getComponents() as $component) {
+            if ($component->name !== 'VTIMEZONE') {
+                $componentType = $component->name;
+                break;
+            }
+        }
+        if (is_null($componentType)) {
+            throw new BadRequest('We expected at least one VTODO, VJOURNAL, VFREEBUSY or VEVENT component');
+        }
+
+        // Validating the METHOD
+        $method = strtoupper((string)$vObject->METHOD);
+        if (!$method) {
+            throw new BadRequest('A METHOD property must be specified in iTIP messages');
+        }
+
+        // So we support one type of request:
+        //
+        // REQUEST with a VFREEBUSY component
+
+        $acl = $this->server->getPlugin('acl');
+
+        if ($componentType === 'VFREEBUSY' && $method === 'REQUEST') {
+
+            $acl && $acl->checkPrivileges($outboxPath, '{' . self::NS_CALDAV . '}schedule-query-freebusy');
+            $this->handleFreeBusyRequest($outboxNode, $vObject, $request, $response);
+
+            // Destroy circular references so PHP can GC the object.
+            $vObject->destroy();
+            unset($vObject);
+
+        } else {
+
+            throw new NotImplemented('We only support VFREEBUSY (REQUEST) on this endpoint');
+
+        }
+
+    }
+
+    /**
+     * This method is responsible for parsing a free-busy query request and
+     * returning it's result.
+     *
+     * @param IOutbox $outbox
+     * @param VObject\Component $vObject
+     * @param RequestInterface $request
+     * @param ResponseInterface $response
+     * @return string
+     */
+    protected function handleFreeBusyRequest(IOutbox $outbox, VObject\Component $vObject, RequestInterface $request, ResponseInterface $response) {
+
+        $vFreeBusy = $vObject->VFREEBUSY;
+        $organizer = $vFreeBusy->organizer;
+
+        $organizer = (string)$organizer;
+
+        // Validating if the organizer matches the owner of the inbox.
+        $owner = $outbox->getOwner();
+
+        $caldavNS = '{' . self::NS_CALDAV . '}';
+
+        $uas = $caldavNS . 'calendar-user-address-set';
+        $props = $this->server->getProperties($owner, [$uas]);
+
+        if (empty($props[$uas]) || !in_array($organizer, $props[$uas]->getHrefs())) {
+            throw new Forbidden('The organizer in the request did not match any of the addresses for the owner of this inbox');
+        }
+
+        if (!isset($vFreeBusy->ATTENDEE)) {
+            throw new BadRequest('You must at least specify 1 attendee');
+        }
+
+        $attendees = [];
+        foreach ($vFreeBusy->ATTENDEE as $attendee) {
+            $attendees[] = (string)$attendee;
+        }
+
+
+        if (!isset($vFreeBusy->DTSTART) || !isset($vFreeBusy->DTEND)) {
+            throw new BadRequest('DTSTART and DTEND must both be specified');
+        }
+
+        $startRange = $vFreeBusy->DTSTART->getDateTime();
+        $endRange = $vFreeBusy->DTEND->getDateTime();
+
+        $results = [];
+        foreach ($attendees as $attendee) {
+            $results[] = $this->getFreeBusyForEmail($attendee, $startRange, $endRange, $vObject);
+        }
+
+        $dom = new \DOMDocument('1.0', 'utf-8');
+        $dom->formatOutput = true;
+        $scheduleResponse = $dom->createElement('cal:schedule-response');
+        foreach ($this->server->xml->namespaceMap as $namespace => $prefix) {
+
+            $scheduleResponse->setAttribute('xmlns:' . $prefix, $namespace);
+
+        }
+        $dom->appendChild($scheduleResponse);
+
+        foreach ($results as $result) {
+            $xresponse = $dom->createElement('cal:response');
+
+            $recipient = $dom->createElement('cal:recipient');
+            $recipientHref = $dom->createElement('d:href');
+
+            $recipientHref->appendChild($dom->createTextNode($result['href']));
+            $recipient->appendChild($recipientHref);
+            $xresponse->appendChild($recipient);
+
+            $reqStatus = $dom->createElement('cal:request-status');
+            $reqStatus->appendChild($dom->createTextNode($result['request-status']));
+            $xresponse->appendChild($reqStatus);
+
+            if (isset($result['calendar-data'])) {
+
+                $calendardata = $dom->createElement('cal:calendar-data');
+                $calendardata->appendChild($dom->createTextNode(str_replace("\r\n", "\n", $result['calendar-data']->serialize())));
+                $xresponse->appendChild($calendardata);
+
+            }
+            $scheduleResponse->appendChild($xresponse);
+        }
+
+        $response->setStatus(200);
+        $response->setHeader('Content-Type', 'application/xml');
+        $response->setBody($dom->saveXML());
+
+    }
+
+    /**
+     * Returns free-busy information for a specific address. The returned
+     * data is an array containing the following properties:
+     *
+     * calendar-data : A VFREEBUSY VObject
+     * request-status : an iTip status code.
+     * href: The principal's email address, as requested
+     *
+     * The following request status codes may be returned:
+     *   * 2.0;description
+     *   * 3.7;description
+     *
+     * @param string $email address
+     * @param DateTimeInterface $start
+     * @param DateTimeInterface $end
+     * @param VObject\Component $request
+     * @return array
+     */
+    protected function getFreeBusyForEmail($email, \DateTimeInterface $start, \DateTimeInterface $end, VObject\Component $request) {
+
+        $caldavNS = '{' . self::NS_CALDAV . '}';
+
+        $aclPlugin = $this->server->getPlugin('acl');
+        if (substr($email, 0, 7) === 'mailto:') $email = substr($email, 7);
+
+        $result = $aclPlugin->principalSearch(
+            ['{http://sabredav.org/ns}email-address' => $email],
+            [
+                '{DAV:}principal-URL',
+                $caldavNS . 'calendar-home-set',
+                $caldavNS . 'schedule-inbox-URL',
+                '{http://sabredav.org/ns}email-address',
+
+            ]
+        );
+
+        if (!count($result)) {
+            return [
+                'request-status' => '3.7;Could not find principal',
+                'href'           => 'mailto:' . $email,
+            ];
+        }
+
+        if (!isset($result[0][200][$caldavNS . 'calendar-home-set'])) {
+            return [
+                'request-status' => '3.7;No calendar-home-set property found',
+                'href'           => 'mailto:' . $email,
+            ];
+        }
+        if (!isset($result[0][200][$caldavNS . 'schedule-inbox-URL'])) {
+            return [
+                'request-status' => '3.7;No schedule-inbox-URL property found',
+                'href'           => 'mailto:' . $email,
+            ];
+        }
+        $homeSet = $result[0][200][$caldavNS . 'calendar-home-set']->getHref();
+        $inboxUrl = $result[0][200][$caldavNS . 'schedule-inbox-URL']->getHref();
+
+        // Grabbing the calendar list
+        $objects = [];
+        $calendarTimeZone = new DateTimeZone('UTC');
+
+        foreach ($this->server->tree->getNodeForPath($homeSet)->getChildren() as $node) {
+            if (!$node instanceof ICalendar) {
+                continue;
+            }
+
+            $sct = $caldavNS . 'schedule-calendar-transp';
+            $ctz = $caldavNS . 'calendar-timezone';
+            $props = $node->getProperties([$sct, $ctz]);
+
+            if (isset($props[$sct]) && $props[$sct]->getValue() == ScheduleCalendarTransp::TRANSPARENT) {
+                // If a calendar is marked as 'transparent', it means we must
+                // ignore it for free-busy purposes.
+                continue;
+            }
+
+            $aclPlugin->checkPrivileges($homeSet . $node->getName(), $caldavNS . 'read-free-busy');
+
+            if (isset($props[$ctz])) {
+                $vtimezoneObj = VObject\Reader::read($props[$ctz]);
+                $calendarTimeZone = $vtimezoneObj->VTIMEZONE->getTimeZone();
+
+                // Destroy circular references so PHP can garbage collect the object.
+                $vtimezoneObj->destroy();
+
+            }
+
+            // Getting the list of object uris within the time-range
+            $urls = $node->calendarQuery([
+                'name'         => 'VCALENDAR',
+                'comp-filters' => [
+                    [
+                        'name'           => 'VEVENT',
+                        'comp-filters'   => [],
+                        'prop-filters'   => [],
+                        'is-not-defined' => false,
+                        'time-range'     => [
+                            'start' => $start,
+                            'end'   => $end,
+                        ],
+                    ],
+                ],
+                'prop-filters'   => [],
+                'is-not-defined' => false,
+                'time-range'     => null,
+            ]);
+
+            $calObjects = array_map(function($url) use ($node) {
+                $obj = $node->getChild($url)->get();
+                return $obj;
+            }, $urls);
+
+            $objects = array_merge($objects, $calObjects);
+
+        }
+
+        $inboxProps = $this->server->getProperties(
+            $inboxUrl,
+            $caldavNS . 'calendar-availability'
+        );
+
+        $vcalendar = new VObject\Component\VCalendar();
+        $vcalendar->METHOD = 'REPLY';
+
+        $generator = new VObject\FreeBusyGenerator();
+        $generator->setObjects($objects);
+        $generator->setTimeRange($start, $end);
+        $generator->setBaseObject($vcalendar);
+        $generator->setTimeZone($calendarTimeZone);
+
+        if ($inboxProps) {
+            $generator->setVAvailability(
+                VObject\Reader::read(
+                    $inboxProps[$caldavNS . 'calendar-availability']
+                )
+            );
+        }
+
+        $result = $generator->getResult();
+
+        $vcalendar->VFREEBUSY->ATTENDEE = 'mailto:' . $email;
+        $vcalendar->VFREEBUSY->UID = (string)$request->VFREEBUSY->UID;
+        $vcalendar->VFREEBUSY->ORGANIZER = clone $request->VFREEBUSY->ORGANIZER;
+
+        return [
+            'calendar-data'  => $result,
+            'request-status' => '2.0;Success',
+            'href'           => 'mailto:' . $email,
+        ];
+    }
+
+    /**
+     * This method checks the 'Schedule-Reply' header
+     * and returns false if it's 'F', otherwise true.
+     *
+     * @param RequestInterface $request
+     * @return bool
+     */
+    private function scheduleReply(RequestInterface $request) {
+
+        $scheduleReply = $request->getHeader('Schedule-Reply');
+        return $scheduleReply !== 'F';
+
+    }
+
+    /**
+     * Returns a bunch of meta-data about the plugin.
+     *
+     * Providing this information is optional, and is mainly displayed by the
+     * Browser plugin.
+     *
+     * The description key in the returned array may contain html and will not
+     * be sanitized.
+     *
+     * @return array
+     */
+    function getPluginInfo() {
+
+        return [
+            'name'        => $this->getPluginName(),
+            'description' => 'Adds calendar-auto-schedule, as defined in rf6868',
+            'link'        => 'http://sabre.io/dav/scheduling/',
+        ];
+
+    }
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Schedule/SchedulingObject.php b/vendor/sabre/dav/lib/CalDAV/Schedule/SchedulingObject.php
new file mode 100644
index 000000000..a36646e6c
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Schedule/SchedulingObject.php
@@ -0,0 +1,165 @@
+<?php
+
+namespace Sabre\CalDAV\Schedule;
+
+use Sabre\CalDAV\Backend;
+use Sabre\DAV\Exception\MethodNotAllowed;
+
+/**
+ * The SchedulingObject represents a scheduling object in the Inbox collection
+ *
+ * @author Brett (https://github.com/bretten)
+ * @license http://sabre.io/license/ Modified BSD License
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ */
+class SchedulingObject extends \Sabre\CalDAV\CalendarObject implements ISchedulingObject {
+
+    /**
+     /* The CalDAV backend
+     *
+     * @var Backend\SchedulingSupport
+     */
+    protected $caldavBackend;
+
+    /**
+     * Array with information about this SchedulingObject
+     *
+     * @var array
+     */
+    protected $objectData;
+
+    /**
+     * Constructor
+     *
+     * The following properties may be passed within $objectData:
+     *
+     *   * uri - A unique uri. Only the 'basename' must be passed.
+     *   * principaluri - the principal that owns the object.
+     *   * calendardata (optional) - The iCalendar data
+     *   * etag - (optional) The etag for this object, MUST be encloded with
+     *            double-quotes.
+     *   * size - (optional) The size of the data in bytes.
+     *   * lastmodified - (optional) format as a unix timestamp.
+     *   * acl - (optional) Use this to override the default ACL for the node.
+     *
+     * @param Backend\BackendInterface $caldavBackend
+     * @param array $objectData
+     */
+    function __construct(Backend\SchedulingSupport $caldavBackend, array $objectData) {
+
+        $this->caldavBackend = $caldavBackend;
+
+        if (!isset($objectData['uri'])) {
+            throw new \InvalidArgumentException('The objectData argument must contain an \'uri\' property');
+        }
+
+        $this->objectData = $objectData;
+
+    }
+
+    /**
+     * Returns the ICalendar-formatted object
+     *
+     * @return string
+     */
+    function get() {
+
+        // Pre-populating the 'calendardata' is optional, if we don't have it
+        // already we fetch it from the backend.
+        if (!isset($this->objectData['calendardata'])) {
+            $this->objectData = $this->caldavBackend->getSchedulingObject($this->objectData['principaluri'], $this->objectData['uri']);
+        }
+        return $this->objectData['calendardata'];
+
+    }
+
+    /**
+     * Updates the ICalendar-formatted object
+     *
+     * @param string|resource $calendarData
+     * @return string
+     */
+    function put($calendarData) {
+
+        throw new MethodNotAllowed('Updating scheduling objects is not supported');
+
+    }
+
+    /**
+     * Deletes the scheduling message
+     *
+     * @return void
+     */
+    function delete() {
+
+        $this->caldavBackend->deleteSchedulingObject($this->objectData['principaluri'], $this->objectData['uri']);
+
+    }
+
+    /**
+     * Returns the owner principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getOwner() {
+
+        return $this->objectData['principaluri'];
+
+    }
+
+
+    /**
+     * Returns a list of ACE's for this node.
+     *
+     * Each ACE has the following properties:
+     *   * 'privilege', a string such as {DAV:}read or {DAV:}write. These are
+     *     currently the only supported privileges
+     *   * 'principal', a url to the principal who owns the node
+     *   * 'protected' (optional), indicating that this ACE is not allowed to
+     *      be updated.
+     *
+     * @return array
+     */
+    function getACL() {
+
+        // An alternative acl may be specified in the object data.
+        //
+
+        if (isset($this->objectData['acl'])) {
+            return $this->objectData['acl'];
+        }
+
+        // The default ACL
+        return [
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->objectData['principaluri'],
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}write',
+                'principal' => $this->objectData['principaluri'],
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->objectData['principaluri'] . '/calendar-proxy-write',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}write',
+                'principal' => $this->objectData['principaluri'] . '/calendar-proxy-write',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->objectData['principaluri'] . '/calendar-proxy-read',
+                'protected' => true,
+            ],
+        ];
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/ShareableCalendar.php b/vendor/sabre/dav/lib/CalDAV/ShareableCalendar.php
new file mode 100644
index 000000000..c11695d5f
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/ShareableCalendar.php
@@ -0,0 +1,72 @@
+<?php
+
+namespace Sabre\CalDAV;
+
+/**
+ * This object represents a CalDAV calendar that can be shared with other
+ * users.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class ShareableCalendar extends Calendar implements IShareableCalendar {
+
+    /**
+     * Updates the list of shares.
+     *
+     * The first array is a list of people that are to be added to the
+     * calendar.
+     *
+     * Every element in the add array has the following properties:
+     *   * href - A url. Usually a mailto: address
+     *   * commonName - Usually a first and last name, or false
+     *   * summary - A description of the share, can also be false
+     *   * readOnly - A boolean value
+     *
+     * Every element in the remove array is just the address string.
+     *
+     * @param array $add
+     * @param array $remove
+     * @return void
+     */
+    function updateShares(array $add, array $remove) {
+
+        $this->caldavBackend->updateShares($this->calendarInfo['id'], $add, $remove);
+
+    }
+
+    /**
+     * Returns the list of people whom this calendar is shared with.
+     *
+     * Every element in this array should have the following properties:
+     *   * href - Often a mailto: address
+     *   * commonName - Optional, for example a first + last name
+     *   * status - See the Sabre\CalDAV\SharingPlugin::STATUS_ constants.
+     *   * readOnly - boolean
+     *   * summary - Optional, a description for the share
+     *
+     * @return array
+     */
+    function getShares() {
+
+        return $this->caldavBackend->getShares($this->calendarInfo['id']);
+
+    }
+
+    /**
+     * Marks this calendar as published.
+     *
+     * Publishing a calendar should automatically create a read-only, public,
+     * subscribable calendar.
+     *
+     * @param bool $value
+     * @return void
+     */
+    function setPublishStatus($value) {
+
+        $this->caldavBackend->setPublishStatus($this->calendarInfo['id'], $value);
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/SharedCalendar.php b/vendor/sabre/dav/lib/CalDAV/SharedCalendar.php
new file mode 100644
index 000000000..7973eff9c
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/SharedCalendar.php
@@ -0,0 +1,148 @@
+<?php
+
+namespace Sabre\CalDAV;
+
+/**
+ * This object represents a CalDAV calendar that is shared by a different user.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class SharedCalendar extends Calendar implements ISharedCalendar {
+
+    /**
+     * Constructor
+     *
+     * @param Backend\BackendInterface $caldavBackend
+     * @param array $calendarInfo
+     */
+    function __construct(Backend\BackendInterface $caldavBackend, $calendarInfo) {
+
+        $required = [
+            '{http://calendarserver.org/ns/}shared-url',
+            '{http://sabredav.org/ns}owner-principal',
+            '{http://sabredav.org/ns}read-only',
+        ];
+        foreach ($required as $r) {
+            if (!isset($calendarInfo[$r])) {
+                throw new \InvalidArgumentException('The ' . $r . ' property must be specified for SharedCalendar(s)');
+            }
+        }
+
+        parent::__construct($caldavBackend, $calendarInfo);
+
+    }
+
+    /**
+     * This method should return the url of the owners' copy of the shared
+     * calendar.
+     *
+     * @return string
+     */
+    function getSharedUrl() {
+
+        return $this->calendarInfo['{http://calendarserver.org/ns/}shared-url'];
+
+    }
+
+    /**
+     * Returns the owner principal
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getOwner() {
+
+        return $this->calendarInfo['{http://sabredav.org/ns}owner-principal'];
+
+    }
+
+    /**
+     * Returns a list of ACE's for this node.
+     *
+     * Each ACE has the following properties:
+     *   * 'privilege', a string such as {DAV:}read or {DAV:}write. These are
+     *     currently the only supported privileges
+     *   * 'principal', a url to the principal who owns the node
+     *   * 'protected' (optional), indicating that this ACE is not allowed to
+     *      be updated.
+     *
+     * @return array
+     */
+    function getACL() {
+
+        // The top-level ACL only contains access information for the true
+        // owner of the calendar, so we need to add the information for the
+        // sharee.
+        $acl = parent::getACL();
+        $acl[] = [
+            'privilege' => '{DAV:}read',
+            'principal' => $this->calendarInfo['principaluri'],
+            'protected' => true,
+        ];
+        if ($this->calendarInfo['{http://sabredav.org/ns}read-only']) {
+            $acl[] = [
+                'privilege' => '{DAV:}write-properties',
+                'principal' => $this->calendarInfo['principaluri'],
+                'protected' => true,
+            ];
+        } else {
+            $acl[] = [
+                'privilege' => '{DAV:}write',
+                'principal' => $this->calendarInfo['principaluri'],
+                'protected' => true,
+            ];
+        }
+        return $acl;
+
+    }
+
+    /**
+     * This method returns the ACL's for calendar objects in this calendar.
+     * The result of this method automatically gets passed to the
+     * calendar-object nodes in the calendar.
+     *
+     * @return array
+     */
+    function getChildACL() {
+
+        $acl = parent::getChildACL();
+        $acl[] = [
+            'privilege' => '{DAV:}read',
+            'principal' => $this->calendarInfo['principaluri'],
+            'protected' => true,
+        ];
+
+        if (!$this->calendarInfo['{http://sabredav.org/ns}read-only']) {
+            $acl[] = [
+                'privilege' => '{DAV:}write',
+                'principal' => $this->calendarInfo['principaluri'],
+                'protected' => true,
+            ];
+        }
+        return $acl;
+
+    }
+
+
+    /**
+     * Returns the list of people whom this calendar is shared with.
+     *
+     * Every element in this array should have the following properties:
+     *   * href - Often a mailto: address
+     *   * commonName - Optional, for example a first + last name
+     *   * status - See the Sabre\CalDAV\SharingPlugin::STATUS_ constants.
+     *   * readOnly - boolean
+     *   * summary - Optional, a description for the share
+     *
+     * @return array
+     */
+    function getShares() {
+
+        return $this->caldavBackend->getShares($this->calendarInfo['id']);
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/SharingPlugin.php b/vendor/sabre/dav/lib/CalDAV/SharingPlugin.php
new file mode 100644
index 000000000..5154fb1de
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/SharingPlugin.php
@@ -0,0 +1,426 @@
+<?php
+
+namespace Sabre\CalDAV;
+
+use Sabre\DAV;
+use Sabre\DAV\Xml\Property\Href;
+use Sabre\HTTP\RequestInterface;
+use Sabre\HTTP\ResponseInterface;
+
+/**
+ * This plugin implements support for caldav sharing.
+ *
+ * This spec is defined at:
+ * http://svn.calendarserver.org/repository/calendarserver/CalendarServer/trunk/doc/Extensions/caldav-sharing.txt
+ *
+ * See:
+ * Sabre\CalDAV\Backend\SharingSupport for all the documentation.
+ *
+ * Note: This feature is experimental, and may change in between different
+ * SabreDAV versions.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class SharingPlugin extends DAV\ServerPlugin {
+
+    /**
+     * These are the various status constants used by sharing-messages.
+     */
+    const STATUS_ACCEPTED = 1;
+    const STATUS_DECLINED = 2;
+    const STATUS_DELETED = 3;
+    const STATUS_NORESPONSE = 4;
+    const STATUS_INVALID = 5;
+
+    /**
+     * Reference to SabreDAV server object.
+     *
+     * @var Sabre\DAV\Server
+     */
+    protected $server;
+
+    /**
+     * This method should return a list of server-features.
+     *
+     * This is for example 'versioning' and is added to the DAV: header
+     * in an OPTIONS response.
+     *
+     * @return array
+     */
+    function getFeatures() {
+
+        return ['calendarserver-sharing'];
+
+    }
+
+    /**
+     * Returns a plugin name.
+     *
+     * Using this name other plugins will be able to access other plugins
+     * using Sabre\DAV\Server::getPlugin
+     *
+     * @return string
+     */
+    function getPluginName() {
+
+        return 'caldav-sharing';
+
+    }
+
+    /**
+     * This initializes the plugin.
+     *
+     * This function is called by Sabre\DAV\Server, after
+     * addPlugin is called.
+     *
+     * This method should set up the required event subscriptions.
+     *
+     * @param DAV\Server $server
+     * @return void
+     */
+    function initialize(DAV\Server $server) {
+
+        $this->server = $server;
+        $server->resourceTypeMapping['Sabre\\CalDAV\\ISharedCalendar'] = '{' . Plugin::NS_CALENDARSERVER . '}shared';
+
+        array_push(
+            $this->server->protectedProperties,
+            '{' . Plugin::NS_CALENDARSERVER . '}invite',
+            '{' . Plugin::NS_CALENDARSERVER . '}allowed-sharing-modes',
+            '{' . Plugin::NS_CALENDARSERVER . '}shared-url'
+        );
+
+        $this->server->xml->elementMap['{' . Plugin::NS_CALENDARSERVER . '}share'] = 'Sabre\\CalDAV\\Xml\\Request\\Share';
+        $this->server->xml->elementMap['{' . Plugin::NS_CALENDARSERVER . '}invite-reply'] = 'Sabre\\CalDAV\\Xml\\Request\\InviteReply';
+
+        $this->server->on('propFind',     [$this, 'propFindEarly']);
+        $this->server->on('propFind',     [$this, 'propFindLate'], 150);
+        $this->server->on('propPatch',    [$this, 'propPatch'], 40);
+        $this->server->on('method:POST',  [$this, 'httpPost']);
+
+    }
+
+    /**
+     * This event is triggered when properties are requested for a certain
+     * node.
+     *
+     * This allows us to inject any properties early.
+     *
+     * @param DAV\PropFind $propFind
+     * @param DAV\INode $node
+     * @return void
+     */
+    function propFindEarly(DAV\PropFind $propFind, DAV\INode $node) {
+
+        if ($node instanceof IShareableCalendar) {
+
+            $propFind->handle('{' . Plugin::NS_CALENDARSERVER . '}invite', function() use ($node) {
+                return new Xml\Property\Invite(
+                    $node->getShares()
+                );
+            });
+
+        }
+
+        if ($node instanceof ISharedCalendar) {
+
+            $propFind->handle('{' . Plugin::NS_CALENDARSERVER . '}shared-url', function() use ($node) {
+                return new Href(
+                    $node->getSharedUrl()
+                );
+            });
+
+            $propFind->handle('{' . Plugin::NS_CALENDARSERVER . '}invite', function() use ($node) {
+
+                // Fetching owner information
+                $props = $this->server->getPropertiesForPath($node->getOwner(), [
+                    '{http://sabredav.org/ns}email-address',
+                    '{DAV:}displayname',
+                ], 0);
+
+                $ownerInfo = [
+                    'href' => $node->getOwner(),
+                ];
+
+                if (isset($props[0][200])) {
+
+                    // We're mapping the internal webdav properties to the
+                    // elements caldav-sharing expects.
+                    if (isset($props[0][200]['{http://sabredav.org/ns}email-address'])) {
+                        $ownerInfo['href'] = 'mailto:' . $props[0][200]['{http://sabredav.org/ns}email-address'];
+                    }
+                    if (isset($props[0][200]['{DAV:}displayname'])) {
+                        $ownerInfo['commonName'] = $props[0][200]['{DAV:}displayname'];
+                    }
+
+                }
+
+                return new Xml\Property\Invite(
+                    $node->getShares(),
+                    $ownerInfo
+                );
+
+            });
+
+        }
+
+    }
+
+    /**
+     * This method is triggered *after* all properties have been retrieved.
+     * This allows us to inject the correct resourcetype for calendars that
+     * have been shared.
+     *
+     * @param DAV\PropFind $propFind
+     * @param DAV\INode $node
+     * @return void
+     */
+    function propFindLate(DAV\PropFind $propFind, DAV\INode $node) {
+
+        if ($node instanceof IShareableCalendar) {
+            if ($rt = $propFind->get('{DAV:}resourcetype')) {
+                if (count($node->getShares()) > 0) {
+                    $rt->add('{' . Plugin::NS_CALENDARSERVER . '}shared-owner');
+                }
+            }
+            $propFind->handle('{' . Plugin::NS_CALENDARSERVER . '}allowed-sharing-modes', function() {
+                return new Xml\Property\AllowedSharingModes(true, false);
+            });
+
+        }
+
+    }
+
+    /**
+     * This method is trigged when a user attempts to update a node's
+     * properties.
+     *
+     * A previous draft of the sharing spec stated that it was possible to use
+     * PROPPATCH to remove 'shared-owner' from the resourcetype, thus unsharing
+     * the calendar.
+     *
+     * Even though this is no longer in the current spec, we keep this around
+     * because OS X 10.7 may still make use of this feature.
+     *
+     * @param string $path
+     * @param DAV\PropPatch $propPatch
+     * @return void
+     */
+    function propPatch($path, DAV\PropPatch $propPatch) {
+
+        $node = $this->server->tree->getNodeForPath($path);
+        if (!$node instanceof IShareableCalendar)
+            return;
+
+        $propPatch->handle('{DAV:}resourcetype', function($value) use ($node) {
+            if ($value->is('{' . Plugin::NS_CALENDARSERVER . '}shared-owner')) return false;
+            $shares = $node->getShares();
+            $remove = [];
+            foreach ($shares as $share) {
+                $remove[] = $share['href'];
+            }
+            $node->updateShares([], $remove);
+
+            return true;
+
+        });
+
+    }
+
+    /**
+     * We intercept this to handle POST requests on calendars.
+     *
+     * @param RequestInterface $request
+     * @param ResponseInterface $response
+     * @return null|bool
+     */
+    function httpPost(RequestInterface $request, ResponseInterface $response) {
+
+        $path = $request->getPath();
+
+        // Only handling xml
+        $contentType = $request->getHeader('Content-Type');
+        if (strpos($contentType, 'application/xml') === false && strpos($contentType, 'text/xml') === false)
+            return;
+
+        // Making sure the node exists
+        try {
+            $node = $this->server->tree->getNodeForPath($path);
+        } catch (DAV\Exception\NotFound $e) {
+            return;
+        }
+
+        $requestBody = $request->getBodyAsString();
+
+        // If this request handler could not deal with this POST request, it
+        // will return 'null' and other plugins get a chance to handle the
+        // request.
+        //
+        // However, we already requested the full body. This is a problem,
+        // because a body can only be read once. This is why we preemptively
+        // re-populated the request body with the existing data.
+        $request->setBody($requestBody);
+
+        $message = $this->server->xml->parse($requestBody, $request->getUrl(), $documentType);
+
+        switch ($documentType) {
+
+            // Dealing with the 'share' document, which modified invitees on a
+            // calendar.
+            case '{' . Plugin::NS_CALENDARSERVER . '}share' :
+
+                // We can only deal with IShareableCalendar objects
+                if (!$node instanceof IShareableCalendar) {
+                    return;
+                }
+
+                $this->server->transactionType = 'post-calendar-share';
+
+                // Getting ACL info
+                $acl = $this->server->getPlugin('acl');
+
+                // If there's no ACL support, we allow everything
+                if ($acl) {
+                    $acl->checkPrivileges($path, '{DAV:}write');
+                }
+
+                $node->updateShares($message->set, $message->remove);
+
+                $response->setStatus(200);
+                // Adding this because sending a response body may cause issues,
+                // and I wanted some type of indicator the response was handled.
+                $response->setHeader('X-Sabre-Status', 'everything-went-well');
+
+                // Breaking the event chain
+                return false;
+
+            // The invite-reply document is sent when the user replies to an
+            // invitation of a calendar share.
+            case '{' . Plugin::NS_CALENDARSERVER . '}invite-reply' :
+
+                // This only works on the calendar-home-root node.
+                if (!$node instanceof CalendarHome) {
+                    return;
+                }
+                $this->server->transactionType = 'post-invite-reply';
+
+                // Getting ACL info
+                $acl = $this->server->getPlugin('acl');
+
+                // If there's no ACL support, we allow everything
+                if ($acl) {
+                    $acl->checkPrivileges($path, '{DAV:}write');
+                }
+
+                $url = $node->shareReply(
+                    $message->href,
+                    $message->status,
+                    $message->calendarUri,
+                    $message->inReplyTo,
+                    $message->summary
+                );
+
+                $response->setStatus(200);
+                // Adding this because sending a response body may cause issues,
+                // and I wanted some type of indicator the response was handled.
+                $response->setHeader('X-Sabre-Status', 'everything-went-well');
+
+                if ($url) {
+                    $writer = $this->server->xml->getWriter($this->server->getBaseUri());
+                    $writer->openMemory();
+                    $writer->startDocument();
+                    $writer->startElement('{' . Plugin::NS_CALENDARSERVER . '}shared-as');
+                    $writer->write(new Href($url));
+                    $writer->endElement();
+                    $response->setHeader('Content-Type', 'application/xml');
+                    $response->setBody($writer->outputMemory());
+
+                }
+
+                // Breaking the event chain
+                return false;
+
+            case '{' . Plugin::NS_CALENDARSERVER . '}publish-calendar' :
+
+                // We can only deal with IShareableCalendar objects
+                if (!$node instanceof IShareableCalendar) {
+                    return;
+                }
+                $this->server->transactionType = 'post-publish-calendar';
+
+                // Getting ACL info
+                $acl = $this->server->getPlugin('acl');
+
+                // If there's no ACL support, we allow everything
+                if ($acl) {
+                    $acl->checkPrivileges($path, '{DAV:}write');
+                }
+
+                $node->setPublishStatus(true);
+
+                // iCloud sends back the 202, so we will too.
+                $response->setStatus(202);
+
+                // Adding this because sending a response body may cause issues,
+                // and I wanted some type of indicator the response was handled.
+                $response->setHeader('X-Sabre-Status', 'everything-went-well');
+
+                // Breaking the event chain
+                return false;
+
+            case '{' . Plugin::NS_CALENDARSERVER . '}unpublish-calendar' :
+
+                // We can only deal with IShareableCalendar objects
+                if (!$node instanceof IShareableCalendar) {
+                    return;
+                }
+                $this->server->transactionType = 'post-unpublish-calendar';
+
+                // Getting ACL info
+                $acl = $this->server->getPlugin('acl');
+
+                // If there's no ACL support, we allow everything
+                if ($acl) {
+                    $acl->checkPrivileges($path, '{DAV:}write');
+                }
+
+                $node->setPublishStatus(false);
+
+                $response->setStatus(200);
+
+                // Adding this because sending a response body may cause issues,
+                // and I wanted some type of indicator the response was handled.
+                $response->setHeader('X-Sabre-Status', 'everything-went-well');
+
+                // Breaking the event chain
+                return false;
+
+        }
+
+
+
+    }
+
+    /**
+     * Returns a bunch of meta-data about the plugin.
+     *
+     * Providing this information is optional, and is mainly displayed by the
+     * Browser plugin.
+     *
+     * The description key in the returned array may contain html and will not
+     * be sanitized.
+     *
+     * @return array
+     */
+    function getPluginInfo() {
+
+        return [
+            'name'        => $this->getPluginName(),
+            'description' => 'Adds support for caldav-sharing.',
+            'link'        => 'http://sabre.io/dav/caldav-sharing/',
+        ];
+
+    }
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Subscriptions/ISubscription.php b/vendor/sabre/dav/lib/CalDAV/Subscriptions/ISubscription.php
new file mode 100644
index 000000000..7ba259c7b
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Subscriptions/ISubscription.php
@@ -0,0 +1,40 @@
+<?php
+
+namespace Sabre\CalDAV\Subscriptions;
+
+use Sabre\DAV\ICollection;
+use Sabre\DAV\IProperties;
+
+/**
+ * ISubscription
+ *
+ * Nodes implementing this interface represent calendar subscriptions.
+ *
+ * The subscription node doesn't do much, other than returning and updating
+ * subscription-related properties.
+ *
+ * The following properties should be supported:
+ *
+ * 1. {DAV:}displayname
+ * 2. {http://apple.com/ns/ical/}refreshrate
+ * 3. {http://calendarserver.org/ns/}subscribed-strip-todos (omit if todos
+ *    should not be stripped).
+ * 4. {http://calendarserver.org/ns/}subscribed-strip-alarms (omit if alarms
+ *    should not be stripped).
+ * 5. {http://calendarserver.org/ns/}subscribed-strip-attachments (omit if
+ *    attachments should not be stripped).
+ * 6. {http://calendarserver.org/ns/}source (Must be a
+ *     Sabre\DAV\Property\Href).
+ * 7. {http://apple.com/ns/ical/}calendar-color
+ * 8. {http://apple.com/ns/ical/}calendar-order
+ *
+ * It is recommended to support every property.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface ISubscription extends ICollection, IProperties {
+
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Subscriptions/Plugin.php b/vendor/sabre/dav/lib/CalDAV/Subscriptions/Plugin.php
new file mode 100644
index 000000000..7abbfb1f9
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Subscriptions/Plugin.php
@@ -0,0 +1,120 @@
+<?php
+
+namespace Sabre\CalDAV\Subscriptions;
+
+use Sabre\DAV\INode;
+use Sabre\DAV\PropFind;
+use Sabre\DAV\ServerPlugin;
+use Sabre\DAV\Server;
+
+/**
+ * This plugin adds calendar-subscription support to your CalDAV server.
+ *
+ * Some clients support 'managed subscriptions' server-side. This is basically
+ * a list of subscription urls a user is using.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Plugin extends ServerPlugin {
+
+    /**
+     * This initializes the plugin.
+     *
+     * This function is called by Sabre\DAV\Server, after
+     * addPlugin is called.
+     *
+     * This method should set up the required event subscriptions.
+     *
+     * @param Server $server
+     * @return void
+     */
+    function initialize(Server $server) {
+
+        $server->resourceTypeMapping['Sabre\\CalDAV\\Subscriptions\\ISubscription'] =
+            '{http://calendarserver.org/ns/}subscribed';
+
+        $server->xml->elementMap['{http://calendarserver.org/ns/}source'] =
+            'Sabre\\DAV\\Xml\\Property\\Href';
+
+        $server->on('propFind', [$this, 'propFind'], 150);
+
+    }
+
+    /**
+     * This method should return a list of server-features.
+     *
+     * This is for example 'versioning' and is added to the DAV: header
+     * in an OPTIONS response.
+     *
+     * @return array
+     */
+    function getFeatures() {
+
+        return ['calendarserver-subscribed'];
+
+    }
+
+    /**
+     * Triggered after properties have been fetched.
+     *
+     * @param PropFind $propFind
+     * @param INode $node
+     * @return void
+     */
+    function propFind(PropFind $propFind, INode $node) {
+
+        // There's a bunch of properties that must appear as a self-closing
+        // xml-element. This event handler ensures that this will be the case.
+        $props = [
+            '{http://calendarserver.org/ns/}subscribed-strip-alarms',
+            '{http://calendarserver.org/ns/}subscribed-strip-attachments',
+            '{http://calendarserver.org/ns/}subscribed-strip-todos',
+        ];
+
+        foreach ($props as $prop) {
+
+            if ($propFind->getStatus($prop) === 200) {
+                $propFind->set($prop, '', 200);
+            }
+
+        }
+
+    }
+
+    /**
+     * Returns a plugin name.
+     *
+     * Using this name other plugins will be able to access other plugins
+     * using \Sabre\DAV\Server::getPlugin
+     *
+     * @return string
+     */
+    function getPluginName() {
+
+        return 'subscriptions';
+
+    }
+
+    /**
+     * Returns a bunch of meta-data about the plugin.
+     *
+     * Providing this information is optional, and is mainly displayed by the
+     * Browser plugin.
+     *
+     * The description key in the returned array may contain html and will not
+     * be sanitized.
+     *
+     * @return array
+     */
+    function getPluginInfo() {
+
+        return [
+            'name'        => $this->getPluginName(),
+            'description' => 'This plugin allows users to store iCalendar subscriptions in their calendar-home.',
+            'link'        => null,
+        ];
+
+    }
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Subscriptions/Subscription.php b/vendor/sabre/dav/lib/CalDAV/Subscriptions/Subscription.php
new file mode 100644
index 000000000..ee53da2c6
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Subscriptions/Subscription.php
@@ -0,0 +1,274 @@
+<?php
+
+namespace Sabre\CalDAV\Subscriptions;
+
+use Sabre\DAV\Collection;
+use Sabre\DAV\Xml\Property\Href;
+use Sabre\DAV\PropPatch;
+use Sabre\DAV\Exception\MethodNotAllowed;
+use Sabre\DAVACL\IACL;
+use Sabre\CalDAV\Backend\SubscriptionSupport;
+
+/**
+ * Subscription Node
+ *
+ * This node represents a subscription.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Subscription extends Collection implements ISubscription, IACL {
+
+    /**
+     * caldavBackend
+     *
+     * @var SupportsSubscriptions
+     */
+    protected $caldavBackend;
+
+    /**
+     * subscriptionInfo
+     *
+     * @var array
+     */
+    protected $subscriptionInfo;
+
+    /**
+     * Constructor
+     *
+     * @param SubscriptionSupport $caldavBackend
+     * @param array $calendarInfo
+     */
+    function __construct(SubscriptionSupport $caldavBackend, array $subscriptionInfo) {
+
+        $this->caldavBackend = $caldavBackend;
+        $this->subscriptionInfo = $subscriptionInfo;
+
+        $required = [
+            'id',
+            'uri',
+            'principaluri',
+            'source',
+            ];
+
+        foreach ($required as $r) {
+            if (!isset($subscriptionInfo[$r])) {
+                throw new \InvalidArgumentException('The ' . $r . ' field is required when creating a subscription node');
+            }
+        }
+
+    }
+
+    /**
+     * Returns the name of the node.
+     *
+     * This is used to generate the url.
+     *
+     * @return string
+     */
+    function getName() {
+
+        return $this->subscriptionInfo['uri'];
+
+    }
+
+    /**
+     * Returns the last modification time
+     *
+     * @return int
+     */
+    function getLastModified() {
+
+        if (isset($this->subscriptionInfo['lastmodified'])) {
+            return $this->subscriptionInfo['lastmodified'];
+        }
+
+    }
+
+    /**
+     * Deletes the current node
+     *
+     * @return void
+     */
+    function delete() {
+
+        $this->caldavBackend->deleteSubscription(
+            $this->subscriptionInfo['id']
+        );
+
+    }
+
+    /**
+     * Returns an array with all the child nodes
+     *
+     * @return DAV\INode[]
+     */
+    function getChildren() {
+
+        return [];
+
+    }
+
+    /**
+     * Updates properties on this node.
+     *
+     * This method received a PropPatch object, which contains all the
+     * information about the update.
+     *
+     * To update specific properties, call the 'handle' method on this object.
+     * Read the PropPatch documentation for more information.
+     *
+     * @param PropPatch $propPatch
+     * @return void
+     */
+    function propPatch(PropPatch $propPatch) {
+
+        return $this->caldavBackend->updateSubscription(
+            $this->subscriptionInfo['id'],
+            $propPatch
+        );
+
+    }
+
+    /**
+     * Returns a list of properties for this nodes.
+     *
+     * The properties list is a list of propertynames the client requested,
+     * encoded in clark-notation {xmlnamespace}tagname.
+     *
+     * If the array is empty, it means 'all properties' were requested.
+     *
+     * Note that it's fine to liberally give properties back, instead of
+     * conforming to the list of requested properties.
+     * The Server class will filter out the extra.
+     *
+     * @param array $properties
+     * @return void
+     */
+    function getProperties($properties) {
+
+        $r = [];
+
+        foreach ($properties as $prop) {
+
+            switch ($prop) {
+                case '{http://calendarserver.org/ns/}source' :
+                    $r[$prop] = new Href($this->subscriptionInfo['source'], false);
+                    break;
+                default :
+                    if (array_key_exists($prop, $this->subscriptionInfo)) {
+                        $r[$prop] = $this->subscriptionInfo[$prop];
+                    }
+                    break;
+            }
+
+        }
+
+        return $r;
+
+    }
+
+    /**
+     * Returns the owner principal.
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getOwner() {
+
+        return $this->subscriptionInfo['principaluri'];
+
+    }
+
+    /**
+     * Returns a group principal.
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    function getGroup() {
+
+        return null;
+
+    }
+
+    /**
+     * Returns a list of ACE's for this node.
+     *
+     * Each ACE has the following properties:
+     *   * 'privilege', a string such as {DAV:}read or {DAV:}write. These are
+     *     currently the only supported privileges
+     *   * 'principal', a url to the principal who owns the node
+     *   * 'protected' (optional), indicating that this ACE is not allowed to
+     *      be updated.
+     *
+     * @return array
+     */
+    function getACL() {
+
+        return [
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->getOwner(),
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}write',
+                'principal' => $this->getOwner(),
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->getOwner() . '/calendar-proxy-write',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}write',
+                'principal' => $this->getOwner() . '/calendar-proxy-write',
+                'protected' => true,
+            ],
+            [
+                'privilege' => '{DAV:}read',
+                'principal' => $this->getOwner() . '/calendar-proxy-read',
+                'protected' => true,
+            ]
+        ];
+
+    }
+
+    /**
+     * Updates the ACL.
+     *
+     * This method will receive a list of new ACE's.
+     *
+     * @param array $acl
+     * @return void
+     */
+    function setACL(array $acl) {
+
+        throw new MethodNotAllowed('Changing ACL is not yet supported');
+
+    }
+
+    /**
+     * Returns the list of supported privileges for this node.
+     *
+     * The returned data structure is a list of nested privileges.
+     * See \Sabre\DAVACL\Plugin::getDefaultSupportedPrivilegeSet for a simple
+     * standard structure.
+     *
+     * If null is returned from this method, the default privilege set is used,
+     * which is fine for most common usecases.
+     *
+     * @return array|null
+     */
+    function getSupportedPrivilegeSet() {
+
+        return null;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Filter/CalendarData.php b/vendor/sabre/dav/lib/CalDAV/Xml/Filter/CalendarData.php
new file mode 100644
index 000000000..9babcf15c
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Filter/CalendarData.php
@@ -0,0 +1,84 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Filter;
+
+use Sabre\Xml\Reader;
+use Sabre\Xml\XmlDeserializable;
+use Sabre\DAV\Exception\BadRequest;
+use Sabre\CalDAV\Plugin;
+use Sabre\VObject\DateTimeParser;
+
+/**
+ * CalendarData parser.
+ *
+ * This class parses the {urn:ietf:params:xml:ns:caldav}calendar-data XML
+ * element, as defined in:
+ *
+ * https://tools.ietf.org/html/rfc4791#section-9.6
+ *
+ * This element is used in three distinct places in the caldav spec, but in
+ * this case, this element class only implements the calendar-data element as
+ * it appears in a DAV:prop element, in a calendar-query or calendar-multiget
+ * REPORT request.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://www.rooftopsolutions.nl/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class CalendarData implements XmlDeserializable {
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * You are responsible for advancing the reader to the next element. Not
+     * doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Reader $reader) {
+
+        $result = [
+            'contentType' => $reader->getAttribute('content-type') ?: 'text/calendar',
+            'version'     => $reader->getAttribute('version') ?: '2.0',
+        ];
+
+        $elems = (array)$reader->parseInnerTree();
+        foreach ($elems as $elem) {
+
+            switch ($elem['name']) {
+                case '{' . Plugin::NS_CALDAV . '}expand' :
+
+                    $result['expand'] = [
+                        'start' => isset($elem['attributes']['start']) ? DateTimeParser::parseDateTime($elem['attributes']['start']) : null,
+                        'end'   => isset($elem['attributes']['end']) ? DateTimeParser::parseDateTime($elem['attributes']['end']) : null,
+                    ];
+
+                    if (!$result['expand']['start'] || !$result['expand']['end']) {
+                        throw new BadRequest('The "start" and "end" attributes are required when expanding calendar-data');
+                    }
+                    if ($result['expand']['end'] <= $result['expand']['start']) {
+                        throw new BadRequest('The end-date must be larger than the start-date when expanding calendar-data');
+                    }
+                    break;
+            }
+
+        }
+
+        return $result;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Filter/CompFilter.php b/vendor/sabre/dav/lib/CalDAV/Xml/Filter/CompFilter.php
new file mode 100644
index 000000000..c9b27dbfd
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Filter/CompFilter.php
@@ -0,0 +1,97 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Filter;
+
+use Sabre\Xml\Reader;
+use Sabre\Xml\XmlDeserializable;
+use Sabre\DAV\Exception\BadRequest;
+use Sabre\CalDAV\Plugin;
+use Sabre\VObject\DateTimeParser;
+
+/**
+ * CompFilter parser.
+ *
+ * This class parses the {urn:ietf:params:xml:ns:caldav}comp-filter XML
+ * element, as defined in:
+ *
+ * https://tools.ietf.org/html/rfc4791#section-9.6
+ *
+ * The result will be spit out as an array.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://www.rooftopsolutions.nl/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class CompFilter implements XmlDeserializable {
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * You are responsible for advancing the reader to the next element. Not
+     * doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Reader $reader) {
+
+        $result = [
+            'name'           => null,
+            'is-not-defined' => false,
+            'comp-filters'   => [],
+            'prop-filters'   => [],
+            'time-range'     => false,
+        ];
+
+        $att = $reader->parseAttributes();
+        $result['name'] = $att['name'];
+
+        $elems = $reader->parseInnerTree();
+
+        if (is_array($elems)) foreach ($elems as $elem) {
+
+            switch ($elem['name']) {
+
+                case '{' . Plugin::NS_CALDAV . '}comp-filter' :
+                    $result['comp-filters'][] = $elem['value'];
+                    break;
+                case '{' . Plugin::NS_CALDAV . '}prop-filter' :
+                    $result['prop-filters'][] = $elem['value'];
+                    break;
+                case '{' . Plugin::NS_CALDAV . '}is-not-defined' :
+                    $result['is-not-defined'] = true;
+                    break;
+                case '{' . Plugin::NS_CALDAV . '}time-range' :
+                    if ($result['name'] === 'VCALENDAR') {
+                        throw new BadRequest('You cannot add time-range filters on the VCALENDAR component');
+                    }
+                    $result['time-range'] = [
+                        'start' => isset($elem['attributes']['start']) ? DateTimeParser::parseDateTime($elem['attributes']['start']) : null,
+                        'end'   => isset($elem['attributes']['end']) ? DateTimeParser::parseDateTime($elem['attributes']['end']) : null,
+                    ];
+                    if ($result['time-range']['start'] && $result['time-range']['end'] && $result['time-range']['end'] <= $result['time-range']['start']) {
+                        throw new BadRequest('The end-date must be larger than the start-date');
+                    }
+                    break;
+
+            }
+
+        }
+
+        return $result;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Filter/ParamFilter.php b/vendor/sabre/dav/lib/CalDAV/Xml/Filter/ParamFilter.php
new file mode 100644
index 000000000..eb7f564df
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Filter/ParamFilter.php
@@ -0,0 +1,82 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Filter;
+
+use Sabre\Xml\Reader;
+use Sabre\Xml\XmlDeserializable;
+use Sabre\CalDAV\Plugin;
+
+/**
+ * PropFilter parser.
+ *
+ * This class parses the {urn:ietf:params:xml:ns:caldav}param-filter XML
+ * element, as defined in:
+ *
+ * https://tools.ietf.org/html/rfc4791#section-9.7.3
+ *
+ * The result will be spit out as an array.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://www.rooftopsolutions.nl/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class ParamFilter implements XmlDeserializable {
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * Important note 2: You are responsible for advancing the reader to the
+     * next element. Not doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Reader $reader) {
+
+        $result = [
+            'name'           => null,
+            'is-not-defined' => false,
+            'text-match'     => null,
+        ];
+
+        $att = $reader->parseAttributes();
+        $result['name'] = $att['name'];
+
+        $elems = $reader->parseInnerTree();
+
+        if (is_array($elems)) foreach ($elems as $elem) {
+
+            switch ($elem['name']) {
+
+                case '{' . Plugin::NS_CALDAV . '}is-not-defined' :
+                    $result['is-not-defined'] = true;
+                    break;
+                case '{' . Plugin::NS_CALDAV . '}text-match' :
+                    $result['text-match'] = [
+                        'negate-condition' => isset($elem['attributes']['negate-condition']) && $elem['attributes']['negate-condition'] === 'yes',
+                        'collation'        => isset($elem['attributes']['collation']) ? $elem['attributes']['collation'] : 'i;ascii-casemap',
+                        'value'            => $elem['value'],
+                    ];
+                    break;
+
+            }
+
+        }
+
+        return $result;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Filter/PropFilter.php b/vendor/sabre/dav/lib/CalDAV/Xml/Filter/PropFilter.php
new file mode 100644
index 000000000..4c2e1b172
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Filter/PropFilter.php
@@ -0,0 +1,98 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Filter;
+
+use Sabre\Xml\Reader;
+use Sabre\Xml\XmlDeserializable;
+use Sabre\DAV\Exception\BadRequest;
+use Sabre\CalDAV\Plugin;
+use Sabre\VObject\DateTimeParser;
+
+/**
+ * PropFilter parser.
+ *
+ * This class parses the {urn:ietf:params:xml:ns:caldav}prop-filter XML
+ * element, as defined in:
+ *
+ * https://tools.ietf.org/html/rfc4791#section-9.7.2
+ *
+ * The result will be spit out as an array.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://www.rooftopsolutions.nl/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class PropFilter implements XmlDeserializable {
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * You are responsible for advancing the reader to the next element. Not
+     * doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Reader $reader) {
+
+        $result = [
+            'name'           => null,
+            'is-not-defined' => false,
+            'param-filters'  => [],
+            'text-match'     => null,
+            'time-range'     => false,
+        ];
+
+        $att = $reader->parseAttributes();
+        $result['name'] = $att['name'];
+
+        $elems = $reader->parseInnerTree();
+
+        if (is_array($elems)) foreach ($elems as $elem) {
+
+            switch ($elem['name']) {
+
+                case '{' . Plugin::NS_CALDAV . '}param-filter' :
+                    $result['param-filters'][] = $elem['value'];
+                    break;
+                case '{' . Plugin::NS_CALDAV . '}is-not-defined' :
+                    $result['is-not-defined'] = true;
+                    break;
+                case '{' . Plugin::NS_CALDAV . '}time-range' :
+                    $result['time-range'] = [
+                        'start' => isset($elem['attributes']['start']) ? DateTimeParser::parseDateTime($elem['attributes']['start']) : null,
+                        'end'   => isset($elem['attributes']['end']) ? DateTimeParser::parseDateTime($elem['attributes']['end']) : null,
+                    ];
+                    if ($result['time-range']['start'] && $result['time-range']['end'] && $result['time-range']['end'] <= $result['time-range']['start']) {
+                        throw new BadRequest('The end-date must be larger than the start-date');
+                    }
+                    break;
+                case '{' . Plugin::NS_CALDAV . '}text-match' :
+                    $result['text-match'] = [
+                        'negate-condition' => isset($elem['attributes']['negate-condition']) && $elem['attributes']['negate-condition'] === 'yes',
+                        'collation'        => isset($elem['attributes']['collation']) ? $elem['attributes']['collation'] : 'i;ascii-casemap',
+                        'value'            => $elem['value'],
+                    ];
+                    break;
+
+            }
+
+        }
+
+        return $result;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Notification/Invite.php b/vendor/sabre/dav/lib/CalDAV/Xml/Notification/Invite.php
new file mode 100644
index 000000000..7fb022e33
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Notification/Invite.php
@@ -0,0 +1,307 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Notification;
+
+use Sabre\Xml\Writer;
+use Sabre\CalDAV\SharingPlugin as SharingPlugin;
+use Sabre\CalDAV;
+
+/**
+ * This class represents the cs:invite-notification notification element.
+ *
+ * This element is defined here:
+ * http://svn.calendarserver.org/repository/calendarserver/CalendarServer/trunk/doc/Extensions/caldav-sharing.txt
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Invite implements NotificationInterface {
+
+    /**
+     * A unique id for the message
+     *
+     * @var string
+     */
+    protected $id;
+
+    /**
+     * Timestamp of the notification
+     *
+     * @var DateTime
+     */
+    protected $dtStamp;
+
+    /**
+     * A url to the recipient of the notification. This can be an email
+     * address (mailto:), or a principal url.
+     *
+     * @var string
+     */
+    protected $href;
+
+    /**
+     * The type of message, see the SharingPlugin::STATUS_* constants.
+     *
+     * @var int
+     */
+    protected $type;
+
+    /**
+     * True if access to a calendar is read-only.
+     *
+     * @var bool
+     */
+    protected $readOnly;
+
+    /**
+     * A url to the shared calendar.
+     *
+     * @var string
+     */
+    protected $hostUrl;
+
+    /**
+     * Url to the sharer of the calendar
+     *
+     * @var string
+     */
+    protected $organizer;
+
+    /**
+     * The name of the sharer.
+     *
+     * @var string
+     */
+    protected $commonName;
+
+    /**
+     * The name of the sharer.
+     *
+     * @var string
+     */
+    protected $firstName;
+
+    /**
+     * The name of the sharer.
+     *
+     * @var string
+     */
+    protected $lastName;
+
+    /**
+     * A description of the share request
+     *
+     * @var string
+     */
+    protected $summary;
+
+    /**
+     * The Etag for the notification
+     *
+     * @var string
+     */
+    protected $etag;
+
+    /**
+     * The list of supported components
+     *
+     * @var Sabre\CalDAV\Property\SupportedCalendarComponentSet
+     */
+    protected $supportedComponents;
+
+    /**
+     * Creates the Invite notification.
+     *
+     * This constructor receives an array with the following elements:
+     *
+     *   * id           - A unique id
+     *   * etag         - The etag
+     *   * dtStamp      - A DateTime object with a timestamp for the notification.
+     *   * type         - The type of notification, see SharingPlugin::STATUS_*
+     *                    constants for details.
+     *   * readOnly     - This must be set to true, if this is an invite for
+     *                    read-only access to a calendar.
+     *   * hostUrl      - A url to the shared calendar.
+     *   * organizer    - Url to the sharer principal.
+     *   * commonName   - The real name of the sharer (optional).
+     *   * firstName    - The first name of the sharer (optional).
+     *   * lastName     - The last name of the sharer (optional).
+     *   * summary      - Description of the share, can be the same as the
+     *                    calendar, but may also be modified (optional).
+     *   * supportedComponents - An instance of
+     *                    Sabre\CalDAV\Property\SupportedCalendarComponentSet.
+     *                    This allows the client to determine which components
+     *                    will be supported in the shared calendar. This is
+     *                    also optional.
+     *
+     * @param array $values All the options
+     */
+    function __construct(array $values) {
+
+        $required = [
+            'id',
+            'etag',
+            'href',
+            'dtStamp',
+            'type',
+            'readOnly',
+            'hostUrl',
+            'organizer',
+        ];
+        foreach ($required as $item) {
+            if (!isset($values[$item])) {
+                throw new \InvalidArgumentException($item . ' is a required constructor option');
+            }
+        }
+
+        foreach ($values as $key => $value) {
+            if (!property_exists($this, $key)) {
+                throw new \InvalidArgumentException('Unknown option: ' . $key);
+            }
+            $this->$key = $value;
+        }
+
+    }
+
+    /**
+     * The xmlSerialize metod is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializble should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Writer $writer) {
+
+        $writer->writeElement('{' . CalDAV\Plugin::NS_CALENDARSERVER . '}invite-notification');
+
+    }
+
+    /**
+     * This method serializes the entire notification, as it is used in the
+     * response body.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerializeFull(Writer $writer) {
+
+        $cs = '{' . CalDAV\Plugin::NS_CALENDARSERVER . '}';
+
+        $this->dtStamp->setTimezone(new \DateTimezone('GMT'));
+        $writer->writeElement($cs . 'dtstamp', $this->dtStamp->format('Ymd\\THis\\Z'));
+
+        $writer->startElement($cs . 'invite-notification');
+
+        $writer->writeElement($cs . 'uid', $this->id);
+        $writer->writeElement('{DAV:}href', $this->href);
+
+        switch ($this->type) {
+
+            case SharingPlugin::STATUS_ACCEPTED :
+                $writer->writeElement($cs . 'invite-accepted');
+                break;
+            case SharingPlugin::STATUS_DECLINED :
+                $writer->writeElement($cs . 'invite-declined');
+                break;
+            case SharingPlugin::STATUS_DELETED :
+                $writer->writeElement($cs . 'invite-deleted');
+                break;
+            case SharingPlugin::STATUS_NORESPONSE :
+                $writer->writeElement($cs . 'invite-noresponse');
+                break;
+
+        }
+
+        $writer->writeElement($cs . 'hosturl', [
+            '{DAV:}href' => $writer->contextUri . $this->hostUrl
+            ]);
+
+        if ($this->summary) {
+            $writer->writeElement($cs . 'summary', $this->summary);
+        }
+
+        $writer->startElement($cs . 'access');
+        if ($this->readOnly) {
+            $writer->writeElement($cs . 'read');
+        } else {
+            $writer->writeElement($cs . 'read-write');
+        }
+        $writer->endElement(); // access
+
+        $writer->startElement($cs . 'organizer');
+        // If the organizer contains a 'mailto:' part, it means it should be
+        // treated as absolute.
+        if (strtolower(substr($this->organizer, 0, 7)) === 'mailto:') {
+            $writer->writeElement('{DAV:}href', $this->organizer);
+        } else {
+            $writer->writeElement('{DAV:}href', $writer->contextUri . $this->organizer);
+        }
+        if ($this->commonName) {
+            $writer->writeElement($cs . 'common-name', $this->commonName);
+        }
+        if ($this->firstName) {
+            $writer->writeElement($cs . 'first-name', $this->firstName);
+        }
+        if ($this->lastName) {
+            $writer->writeElement($cs . 'last-name', $this->lastName);
+        }
+        $writer->endElement(); // organizer
+
+        if ($this->commonName) {
+            $writer->writeElement($cs . 'organizer-cn', $this->commonName);
+        }
+        if ($this->firstName) {
+            $writer->writeElement($cs . 'organizer-first', $this->firstName);
+        }
+        if ($this->lastName) {
+            $writer->writeElement($cs . 'organizer-last', $this->lastName);
+        }
+        if ($this->supportedComponents) {
+            $writer->writeElement('{' . CalDAV\Plugin::NS_CALDAV . '}supported-calendar-component-set', $this->supportedComponents);
+        }
+
+        $writer->endElement(); // invite-notification
+
+    }
+
+    /**
+     * Returns a unique id for this notification
+     *
+     * This is just the base url. This should generally be some kind of unique
+     * id.
+     *
+     * @return string
+     */
+    function getId() {
+
+        return $this->id;
+
+    }
+
+    /**
+     * Returns the ETag for this notification.
+     *
+     * The ETag must be surrounded by literal double-quotes.
+     *
+     * @return string
+     */
+    function getETag() {
+
+        return $this->etag;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Notification/InviteReply.php b/vendor/sabre/dav/lib/CalDAV/Xml/Notification/InviteReply.php
new file mode 100644
index 000000000..945323fed
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Notification/InviteReply.php
@@ -0,0 +1,212 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Notification;
+
+use Sabre\Xml\Writer;
+use Sabre\CalDAV;
+use Sabre\CalDAV\SharingPlugin;
+
+/**
+ * This class represents the cs:invite-reply notification element.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class InviteReply implements NotificationInterface {
+
+    /**
+     * A unique id for the message
+     *
+     * @var string
+     */
+    protected $id;
+
+    /**
+     * Timestamp of the notification
+     *
+     * @var DateTime
+     */
+    protected $dtStamp;
+
+    /**
+     * The unique id of the notification this was a reply to.
+     *
+     * @var string
+     */
+    protected $inReplyTo;
+
+    /**
+     * A url to the recipient of the original (!) notification.
+     *
+     * @var string
+     */
+    protected $href;
+
+    /**
+     * The type of message, see the SharingPlugin::STATUS_ constants.
+     *
+     * @var int
+     */
+    protected $type;
+
+    /**
+     * A url to the shared calendar.
+     *
+     * @var string
+     */
+    protected $hostUrl;
+
+    /**
+     * A description of the share request
+     *
+     * @var string
+     */
+    protected $summary;
+
+    /**
+     * Notification Etag
+     *
+     * @var string
+     */
+    protected $etag;
+
+    /**
+     * Creates the Invite Reply Notification.
+     *
+     * This constructor receives an array with the following elements:
+     *
+     *   * id           - A unique id
+     *   * etag         - The etag
+     *   * dtStamp      - A DateTime object with a timestamp for the notification.
+     *   * inReplyTo    - This should refer to the 'id' of the notification
+     *                    this is a reply to.
+     *   * type         - The type of notification, see SharingPlugin::STATUS_*
+     *                    constants for details.
+     *   * hostUrl      - A url to the shared calendar.
+     *   * summary      - Description of the share, can be the same as the
+     *                    calendar, but may also be modified (optional).
+     *
+     * @param array $values
+     */
+    function __construct(array $values) {
+
+        $required = [
+            'id',
+            'etag',
+            'href',
+            'dtStamp',
+            'inReplyTo',
+            'type',
+            'hostUrl',
+        ];
+        foreach ($required as $item) {
+            if (!isset($values[$item])) {
+                throw new \InvalidArgumentException($item . ' is a required constructor option');
+            }
+        }
+
+        foreach ($values as $key => $value) {
+            if (!property_exists($this, $key)) {
+                throw new \InvalidArgumentException('Unknown option: ' . $key);
+            }
+            $this->$key = $value;
+        }
+
+    }
+
+    /**
+     * The xmlSerialize metod is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializble should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Writer $writer) {
+
+        $writer->writeElement('{' . CalDAV\Plugin::NS_CALENDARSERVER . '}invite-reply');
+
+    }
+
+    /**
+     * This method serializes the entire notification, as it is used in the
+     * response body.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerializeFull(Writer $writer) {
+
+        $cs = '{' . CalDAV\Plugin::NS_CALENDARSERVER . '}';
+
+        $this->dtStamp->setTimezone(new \DateTimezone('GMT'));
+        $writer->writeElement($cs . 'dtstamp', $this->dtStamp->format('Ymd\\THis\\Z'));
+
+        $writer->startElement($cs . 'invite-reply');
+
+        $writer->writeElement($cs . 'uid', $this->id);
+        $writer->writeElement($cs . 'in-reply-to', $this->inReplyTo);
+        $writer->writeElement('{DAV:}href', $this->href);
+
+        switch ($this->type) {
+
+            case SharingPlugin::STATUS_ACCEPTED :
+                $writer->writeElement($cs . 'invite-accepted');
+                break;
+            case SharingPlugin::STATUS_DECLINED :
+                $writer->writeElement($cs . 'invite-declined');
+                break;
+
+        }
+
+        $writer->writeElement($cs . 'hosturl', [
+            '{DAV:}href' => $writer->contextUri . $this->hostUrl
+            ]);
+
+        if ($this->summary) {
+            $writer->writeElement($cs . 'summary', $this->summary);
+        }
+        $writer->endElement(); // invite-reply
+
+    }
+
+    /**
+     * Returns a unique id for this notification
+     *
+     * This is just the base url. This should generally be some kind of unique
+     * id.
+     *
+     * @return string
+     */
+    function getId() {
+
+        return $this->id;
+
+    }
+
+    /**
+     * Returns the ETag for this notification.
+     *
+     * The ETag must be surrounded by literal double-quotes.
+     *
+     * @return string
+     */
+    function getETag() {
+
+        return $this->etag;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Notification/NotificationInterface.php b/vendor/sabre/dav/lib/CalDAV/Xml/Notification/NotificationInterface.php
new file mode 100644
index 000000000..1c08f12fd
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Notification/NotificationInterface.php
@@ -0,0 +1,45 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Notification;
+
+use Sabre\Xml\XmlSerializable;
+use Sabre\Xml\Writer;
+
+/**
+ * This interface reflects a single notification type.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+interface NotificationInterface extends XmlSerializable {
+
+    /**
+     * This method serializes the entire notification, as it is used in the
+     * response body.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerializeFull(Writer $writer);
+
+    /**
+     * Returns a unique id for this notification
+     *
+     * This is just the base url. This should generally be some kind of unique
+     * id.
+     *
+     * @return string
+     */
+    function getId();
+
+    /**
+     * Returns the ETag for this notification.
+     *
+     * The ETag must be surrounded by literal double-quotes.
+     *
+     * @return string
+     */
+    function getETag();
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Notification/SystemStatus.php b/vendor/sabre/dav/lib/CalDAV/Xml/Notification/SystemStatus.php
new file mode 100644
index 000000000..d41702e07
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Notification/SystemStatus.php
@@ -0,0 +1,182 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Notification;
+
+use Sabre\Xml\Writer;
+use Sabre\CalDAV\Plugin;
+
+/**
+ * SystemStatus notification
+ *
+ * This notification can be used to indicate to the user that the system is
+ * down.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class SystemStatus implements NotificationInterface {
+
+    const TYPE_LOW = 1;
+    const TYPE_MEDIUM = 2;
+    const TYPE_HIGH = 3;
+
+    /**
+     * A unique id
+     *
+     * @var string
+     */
+    protected $id;
+
+    /**
+     * The type of alert. This should be one of the TYPE_ constants.
+     *
+     * @var int
+     */
+    protected $type;
+
+    /**
+     * A human-readable description of the problem.
+     *
+     * @var string
+     */
+    protected $description;
+
+    /**
+     * A url to a website with more information for the user.
+     *
+     * @var string
+     */
+    protected $href;
+
+    /**
+     * Notification Etag
+     *
+     * @var string
+     */
+    protected $etag;
+
+    /**
+     * Creates the notification.
+     *
+     * Some kind of unique id should be provided. This is used to generate a
+     * url.
+     *
+     * @param string $id
+     * @param string $etag
+     * @param int $type
+     * @param string $description
+     * @param string $href
+     */
+    function __construct($id, $etag, $type = self::TYPE_HIGH, $description = null, $href = null) {
+
+        $this->id = $id;
+        $this->type = $type;
+        $this->description = $description;
+        $this->href = $href;
+        $this->etag = $etag;
+
+    }
+
+    /**
+     * The serialize method is called during xml writing.
+     *
+     * It should use the $writer argument to encode this object into XML.
+     *
+     * Important note: it is not needed to create the parent element. The
+     * parent element is already created, and we only have to worry about
+     * attributes, child elements and text (if any).
+     *
+     * Important note 2: If you are writing any new elements, you are also
+     * responsible for closing them.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Writer $writer) {
+
+        switch ($this->type) {
+            case self::TYPE_LOW :
+                $type = 'low';
+                break;
+            case self::TYPE_MEDIUM :
+                $type = 'medium';
+                break;
+            default :
+            case self::TYPE_HIGH :
+                $type = 'high';
+                break;
+        }
+
+        $writer->startElement('{' . Plugin::NS_CALENDARSERVER . '}systemstatus');
+        $writer->writeAttribute('type', $type);
+        $writer->endElement();
+
+    }
+
+    /**
+     * This method serializes the entire notification, as it is used in the
+     * response body.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerializeFull(Writer $writer) {
+
+        $cs = '{' . Plugin::NS_CALENDARSERVER . '}';
+        switch ($this->type) {
+            case self::TYPE_LOW :
+                $type = 'low';
+                break;
+            case self::TYPE_MEDIUM :
+                $type = 'medium';
+                break;
+            default :
+            case self::TYPE_HIGH :
+                $type = 'high';
+                break;
+        }
+
+        $writer->startElement($cs . 'systemstatus');
+        $writer->writeAttribute('type', $type);
+
+
+        if ($this->description) {
+            $writer->writeElement($cs . 'description', $this->description);
+        }
+        if ($this->href) {
+            $writer->writeElement('{DAV:}href', $this->href);
+        }
+
+        $writer->endElement(); // systemstatus
+
+    }
+
+    /**
+     * Returns a unique id for this notification
+     *
+     * This is just the base url. This should generally be some kind of unique
+     * id.
+     *
+     * @return string
+     */
+    function getId() {
+
+        return $this->id;
+
+    }
+
+    /*
+     * Returns the ETag for this notification.
+     *
+     * The ETag must be surrounded by literal double-quotes.
+     *
+     * @return string
+     */
+    function getETag() {
+
+        return $this->etag;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Property/AllowedSharingModes.php b/vendor/sabre/dav/lib/CalDAV/Xml/Property/AllowedSharingModes.php
new file mode 100644
index 000000000..c2a2d565e
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Property/AllowedSharingModes.php
@@ -0,0 +1,87 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Property;
+
+use Sabre\Xml\XmlSerializable;
+use Sabre\Xml\Writer;
+use Sabre\CalDAV\Plugin;
+
+/**
+ * AllowedSharingModes
+ *
+ * This property encodes the 'allowed-sharing-modes' property, as defined by
+ * the 'caldav-sharing-02' spec, in the http://calendarserver.org/ns/
+ * namespace.
+ *
+ * This property is a representation of the supported-calendar_component-set
+ * property in the CalDAV namespace. It simply requires an array of components,
+ * such as VEVENT, VTODO
+ *
+ * @see https://trac.calendarserver.org/browser/CalendarServer/trunk/doc/Extensions/caldav-sharing-02.txt
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://www.rooftopsolutions.nl/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class AllowedSharingModes implements XmlSerializable {
+
+    /**
+     * Whether or not a calendar can be shared with another user
+     *
+     * @var bool
+     */
+    protected $canBeShared;
+
+    /**
+     * Whether or not the calendar can be placed on a public url.
+     *
+     * @var bool
+     */
+    protected $canBePublished;
+
+    /**
+     * Constructor
+     *
+     * @param bool $canBeShared
+     * @param bool $canBePublished
+     * @return void
+     */
+    function __construct($canBeShared, $canBePublished) {
+
+        $this->canBeShared = $canBeShared;
+        $this->canBePublished = $canBePublished;
+
+    }
+
+    /**
+     * The xmlSerialize metod is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializble should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Writer $writer) {
+
+        if ($this->canBeShared) {
+            $writer->writeElement('{' . Plugin::NS_CALENDARSERVER . '}can-be-shared');
+        }
+        if ($this->canBePublished) {
+            $writer->writeElement('{' . Plugin::NS_CALENDARSERVER . '}can-be-published');
+        }
+
+    }
+
+
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Property/EmailAddressSet.php b/vendor/sabre/dav/lib/CalDAV/Xml/Property/EmailAddressSet.php
new file mode 100644
index 000000000..f577a9919
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Property/EmailAddressSet.php
@@ -0,0 +1,80 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Property;
+
+use Sabre\Xml\Writer;
+use Sabre\Xml\XmlSerializable;
+
+/**
+ * email-address-set property
+ *
+ * This property represents the email-address-set property in the
+ * http://calendarserver.org/ns/ namespace.
+ *
+ * It's a list of email addresses associated with a user.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class EmailAddressSet implements XmlSerializable {
+
+    /**
+     * emails
+     *
+     * @var array
+     */
+    private $emails;
+
+    /**
+     * __construct
+     *
+     * @param array $emails
+     */
+    function __construct(array $emails) {
+
+        $this->emails = $emails;
+
+    }
+
+    /**
+     * Returns the email addresses
+     *
+     * @return array
+     */
+    function getValue() {
+
+        return $this->emails;
+
+    }
+
+    /**
+     * The xmlSerialize metod is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializble should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Writer $writer) {
+
+        foreach ($this->emails as $email) {
+
+            $writer->writeElement('{http://calendarserver.org/ns/}email-address', $email);
+
+        }
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Property/Invite.php b/vendor/sabre/dav/lib/CalDAV/Xml/Property/Invite.php
new file mode 100644
index 000000000..3ee053214
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Property/Invite.php
@@ -0,0 +1,252 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Property;
+
+use Sabre\Xml\Element;
+use Sabre\Xml\Reader;
+use Sabre\Xml\Writer;
+use Sabre\CalDAV\Plugin;
+use Sabre\CalDAV\SharingPlugin;
+
+/**
+ * Invite property
+ *
+ * This property encodes the 'invite' property, as defined by
+ * the 'caldav-sharing-02' spec, in the http://calendarserver.org/ns/
+ * namespace.
+ *
+ * @see https://trac.calendarserver.org/browser/CalendarServer/trunk/doc/Extensions/caldav-sharing-02.txt
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Invite implements Element {
+
+    /**
+     * The list of users a calendar has been shared to.
+     *
+     * @var array
+     */
+    protected $users;
+
+    /**
+     * The organizer contains information about the person who shared the
+     * object.
+     *
+     * @var array
+     */
+    protected $organizer;
+
+    /**
+     * Creates the property.
+     *
+     * Users is an array. Each element of the array has the following
+     * properties:
+     *
+     *   * href - Often a mailto: address
+     *   * commonName - Optional, for example a first and lastname for a user.
+     *   * status - One of the SharingPlugin::STATUS_* constants.
+     *   * readOnly - true or false
+     *   * summary - Optional, description of the share
+     *
+     * The organizer key is optional to specify. It's only useful when a
+     * 'sharee' requests the sharing information.
+     *
+     * The organizer may have the following properties:
+     *   * href - Often a mailto: address.
+     *   * commonName - Optional human-readable name.
+     *   * firstName - Optional first name.
+     *   * lastName - Optional last name.
+     *
+     * If you wonder why these two structures are so different, I guess a
+     * valid answer is that the current spec is still a draft.
+     *
+     * @param array $users
+     */
+    function __construct(array $users, array $organizer = null) {
+
+        $this->users = $users;
+        $this->organizer = $organizer;
+
+    }
+
+    /**
+     * Returns the list of users, as it was passed to the constructor.
+     *
+     * @return array
+     */
+    function getValue() {
+
+        return $this->users;
+
+    }
+
+    /**
+     * The xmlSerialize metod is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializble should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Writer $writer) {
+
+        $cs = '{' . Plugin::NS_CALENDARSERVER . '}';
+
+        if (!is_null($this->organizer)) {
+
+            $writer->startElement($cs . 'organizer');
+            $writer->writeElement('{DAV:}href', $this->organizer['href']);
+
+            if (isset($this->organizer['commonName']) && $this->organizer['commonName']) {
+                $writer->writeElement($cs . 'common-name', $this->organizer['commonName']);
+            }
+            if (isset($this->organizer['firstName']) && $this->organizer['firstName']) {
+                $writer->writeElement($cs . 'first-name', $this->organizer['firstName']);
+            }
+            if (isset($this->organizer['lastName']) && $this->organizer['lastName']) {
+                $writer->writeElement($cs . 'last-name', $this->organizer['lastName']);
+            }
+            $writer->endElement(); // organizer
+
+        }
+
+        foreach ($this->users as $user) {
+
+            $writer->startElement($cs . 'user');
+            $writer->writeElement('{DAV:}href', $user['href']);
+            if (isset($user['commonName']) && $user['commonName']) {
+                $writer->writeElement($cs . 'common-name', $user['commonName']);
+            }
+            switch ($user['status']) {
+
+                case SharingPlugin::STATUS_ACCEPTED :
+                    $writer->writeElement($cs . 'invite-accepted');
+                    break;
+                case SharingPlugin::STATUS_DECLINED :
+                    $writer->writeElement($cs . 'invite-declined');
+                    break;
+                case SharingPlugin::STATUS_NORESPONSE :
+                    $writer->writeElement($cs . 'invite-noresponse');
+                    break;
+                case SharingPlugin::STATUS_INVALID :
+                    $writer->writeElement($cs . 'invite-invalid');
+                    break;
+            }
+
+            $writer->startElement($cs . 'access');
+            if ($user['readOnly']) {
+                $writer->writeElement($cs . 'read');
+            } else {
+                $writer->writeElement($cs . 'read-write');
+            }
+            $writer->endElement(); // access
+
+            if (isset($user['summary']) && $user['summary']) {
+                $writer->writeElement($cs . 'summary', $user['summary']);
+            }
+
+            $writer->endElement(); //user
+
+        }
+
+    }
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * You are responsible for advancing the reader to the next element. Not
+     * doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Reader $reader) {
+
+        $cs = '{' . Plugin::NS_CALENDARSERVER . '}';
+
+        $users = [];
+
+        foreach ($reader->parseInnerTree() as $elem) {
+
+            if ($elem['name'] !== $cs . 'user')
+                continue;
+
+            $user = [
+                'href'       => null,
+                'commonName' => null,
+                'readOnly'   => null,
+                'summary'    => null,
+                'status'     => null,
+            ];
+
+            foreach ($elem['value'] as $userElem) {
+
+                switch ($userElem['name']) {
+                    case $cs . 'invite-accepted' :
+                        $user['status'] = SharingPlugin::STATUS_ACCEPTED;
+                        break;
+                    case $cs . 'invite-declined' :
+                        $user['status'] = SharingPlugin::STATUS_DECLINED;
+                        break;
+                    case $cs . 'invite-noresponse' :
+                        $user['status'] = SharingPlugin::STATUS_NORESPONSE;
+                        break;
+                    case $cs . 'invite-invalid' :
+                        $user['status'] = SharingPlugin::STATUS_INVALID;
+                        break;
+                    case '{DAV:}href' :
+                        $user['href'] = $userElem['value'];
+                        break;
+                    case $cs . 'common-name' :
+                        $user['commonName'] = $userElem['value'];
+                        break;
+                    case $cs . 'access' :
+                        foreach ($userElem['value'] as $accessHref) {
+                            if ($accessHref['name'] === $cs . 'read') {
+                                $user['readOnly'] = true;
+                            }
+                        }
+                        break;
+                    case $cs . 'summary' :
+                        $user['summary'] = $userElem['value'];
+                        break;
+
+                }
+
+            }
+            if (!$user['status']) {
+                throw new \InvalidArgumentException('Every user must have one of cs:invite-accepted, cs:invite-declined, cs:invite-noresponse or cs:invite-invalid');
+            }
+
+            $users[] = $user;
+
+        }
+
+        return new self($users);
+
+    }
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Property/ScheduleCalendarTransp.php b/vendor/sabre/dav/lib/CalDAV/Xml/Property/ScheduleCalendarTransp.php
new file mode 100644
index 000000000..4a253e008
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Property/ScheduleCalendarTransp.php
@@ -0,0 +1,140 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Property;
+
+use Sabre\Xml\Element;
+use Sabre\Xml\Reader;
+use Sabre\Xml\Writer;
+use Sabre\Xml\Element\Elements;
+use Sabre\CalDAV\Plugin;
+
+/**
+ * schedule-calendar-transp property.
+ *
+ * This property is a representation of the schedule-calendar-transp property.
+ * This property is defined in:
+ *
+ * http://tools.ietf.org/html/rfc6638#section-9.1
+ *
+ * Its values are either 'transparent' or 'opaque'. If it's transparent, it
+ * means that this calendar will not be taken into consideration when a
+ * different user queries for free-busy information. If it's 'opaque', it will.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://www.rooftopsolutions.nl/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class ScheduleCalendarTransp implements Element {
+
+    const TRANSPARENT = 'transparent';
+    const OPAQUE = 'opaque';
+
+    /**
+     * value
+     *
+     * @var string
+     */
+    protected $value;
+
+    /**
+     * Creates the property
+     *
+     * @param string $value
+     */
+    function __construct($value) {
+
+        if ($value !== self::TRANSPARENT && $value !== self::OPAQUE) {
+            throw new \InvalidArgumentException('The value must either be specified as "transparent" or "opaque"');
+        }
+        $this->value = $value;
+
+    }
+
+    /**
+     * Returns the current value
+     *
+     * @return string
+     */
+    function getValue() {
+
+        return $this->value;
+
+    }
+
+    /**
+     * The xmlSerialize metod is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializble should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Writer $writer) {
+
+        switch ($this->value) {
+            case self::TRANSPARENT :
+                $writer->writeElement('{' . Plugin::NS_CALDAV . '}transparent');
+                break;
+            case self::OPAQUE :
+                $writer->writeElement('{' . Plugin::NS_CALDAV . '}opaque');
+                break;
+        }
+
+    }
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * You are responsible for advancing the reader to the next element. Not
+     * doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Reader $reader) {
+
+        $elems = Elements::xmlDeserialize($reader);
+
+        $value = null;
+
+        foreach ($elems as $elem) {
+            switch ($elem) {
+                case '{' . Plugin::NS_CALDAV . '}opaque' :
+                    $value = self::OPAQUE;
+                    break;
+                case '{' . Plugin::NS_CALDAV . '}transparent' :
+                    $value = self::TRANSPARENT;
+                    break;
+            }
+        }
+        if (is_null($value))
+           return null;
+
+        return new self($value);
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Property/SupportedCalendarComponentSet.php b/vendor/sabre/dav/lib/CalDAV/Xml/Property/SupportedCalendarComponentSet.php
new file mode 100644
index 000000000..7a26e767e
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Property/SupportedCalendarComponentSet.php
@@ -0,0 +1,129 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Property;
+
+use Sabre\Xml\Element;
+use Sabre\Xml\ParseException;
+use Sabre\Xml\Reader;
+use Sabre\Xml\Writer;
+use Sabre\CalDAV\Plugin;
+
+/**
+ * SupportedCalendarComponentSet property.
+ *
+ * This class represents the
+ * {urn:ietf:params:xml:ns:caldav}supported-calendar-component-set property, as
+ * defined in:
+ *
+ * https://tools.ietf.org/html/rfc4791#section-5.2.3
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class SupportedCalendarComponentSet implements Element {
+
+    /**
+     * List of supported components.
+     *
+     * This array will contain values such as VEVENT, VTODO and VJOURNAL.
+     *
+     * @var array
+     */
+    protected $components = [];
+
+    /**
+     * Creates the property.
+     *
+     * @param array $components
+     */
+    function __construct(array $components) {
+
+        $this->components = $components;
+
+    }
+
+    /**
+     * Returns the list of supported components
+     *
+     * @return array
+     */
+    function getValue() {
+
+        return $this->components;
+
+    }
+
+    /**
+     * The xmlSerialize metod is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializble should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Writer $writer) {
+
+        foreach ($this->components as $component) {
+
+            $writer->startElement('{' . Plugin::NS_CALDAV . '}comp');
+            $writer->writeAttributes(['name' => $component]);
+            $writer->endElement();
+
+        }
+
+    }
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * You are responsible for advancing the reader to the next element. Not
+     * doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Reader $reader) {
+
+        $elems = $reader->parseInnerTree();
+
+        $components = [];
+
+        foreach ((array)$elems as $elem) {
+            if ($elem['name'] === '{' . Plugin::NS_CALDAV . '}comp') {
+                $components[] = $elem['attributes']['name'];
+            }
+        }
+
+        if (!$components) {
+            throw new ParseException('supported-calendar-component-set must have at least one CALDAV:comp element');
+        }
+
+        return new self($components);
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Property/SupportedCalendarData.php b/vendor/sabre/dav/lib/CalDAV/Xml/Property/SupportedCalendarData.php
new file mode 100644
index 000000000..b0c407fd6
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Property/SupportedCalendarData.php
@@ -0,0 +1,60 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Property;
+
+use Sabre\Xml\XmlSerializable;
+use Sabre\Xml\Writer;
+use Sabre\CalDAV\Plugin;
+
+/**
+ * Supported-calendar-data property
+ *
+ * This property is a representation of the supported-calendar-data property
+ * in the CalDAV namespace. SabreDAV only has support for text/calendar;2.0
+ * so the value is currently hardcoded.
+ *
+ * This property is defined in:
+ * http://tools.ietf.org/html/rfc4791#section-5.2.4
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://www.rooftopsolutions.nl/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class SupportedCalendarData implements XmlSerializable {
+
+    /**
+     * The xmlSerialize metod is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializble should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Writer $writer) {
+
+        $writer->startElement('{' . Plugin::NS_CALDAV . '}calendar-data');
+        $writer->writeAttributes([
+            'content-type' => 'text/calendar',
+            'version'      => '2.0',
+        ]);
+        $writer->endElement(); // calendar-data
+        $writer->startElement('{' . Plugin::NS_CALDAV . '}calendar-data');
+        $writer->writeAttributes([
+            'content-type' => 'application/calendar+json',
+        ]);
+        $writer->endElement(); // calendar-data
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Property/SupportedCollationSet.php b/vendor/sabre/dav/lib/CalDAV/Xml/Property/SupportedCollationSet.php
new file mode 100644
index 000000000..71de25a62
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Property/SupportedCollationSet.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Property;
+
+use Sabre\Xml\Writer;
+use Sabre\Xml\XmlSerializable;
+use Sabre\CalDAV\Plugin;
+
+/**
+ * supported-collation-set property
+ *
+ * This property is a representation of the supported-collation-set property
+ * in the CalDAV namespace.
+ *
+ * This property is defined in:
+ * http://tools.ietf.org/html/rfc4791#section-7.5.1
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class SupportedCollationSet implements XmlSerializable {
+
+    /**
+     * The xmlSerialize metod is called during xml writing.
+     *
+     * Use the $writer argument to write its own xml serialization.
+     *
+     * An important note: do _not_ create a parent element. Any element
+     * implementing XmlSerializble should only ever write what's considered
+     * its 'inner xml'.
+     *
+     * The parent of the current element is responsible for writing a
+     * containing element.
+     *
+     * This allows serializers to be re-used for different element names.
+     *
+     * If you are opening new elements, you must also close them again.
+     *
+     * @param Writer $writer
+     * @return void
+     */
+    function xmlSerialize(Writer $writer) {
+
+        $collations = [
+            'i;ascii-casemap',
+            'i;octet',
+            'i;unicode-casemap'
+        ];
+
+        foreach ($collations as $collation) {
+            $writer->writeElement('{' . Plugin::NS_CALDAV . '}supported-collation', $collation);
+        }
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Request/CalendarMultiGetReport.php b/vendor/sabre/dav/lib/CalDAV/Xml/Request/CalendarMultiGetReport.php
new file mode 100644
index 000000000..79b3bb3ac
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Request/CalendarMultiGetReport.php
@@ -0,0 +1,124 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Request;
+
+use Sabre\Xml\XmlDeserializable;
+use Sabre\Xml\Reader;
+use Sabre\CalDAV\Plugin;
+use Sabre\Uri;
+
+/**
+ * CalendarMultiGetReport request parser.
+ *
+ * This class parses the {urn:ietf:params:xml:ns:caldav}calendar-multiget
+ * REPORT, as defined in:
+ *
+ * https://tools.ietf.org/html/rfc4791#section-7.9
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://www.rooftopsolutions.nl/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class CalendarMultiGetReport implements XmlDeserializable {
+
+    /**
+     * An array with requested properties.
+     *
+     * @var array
+     */
+    public $properties;
+
+    /**
+     * This is an array with the urls that are being requested.
+     *
+     * @var array
+     */
+    public $hrefs;
+
+    /**
+     * If the calendar data must be expanded, this will contain an array with 2
+     * elements: start and end.
+     *
+     * Each may be a DateTime or null.
+     *
+     * @var array|null
+     */
+    public $expand = null;
+
+    /**
+     * The mimetype of the content that should be returend. Usually
+     * text/calendar.
+     *
+     * @var string
+     */
+    public $contentType = null;
+
+    /**
+     * The version of calendar-data that should be returned. Usually '2.0',
+     * referring to iCalendar 2.0.
+     *
+     * @var string
+     */
+    public $version = null;
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * You are responsible for advancing the reader to the next element. Not
+     * doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Reader $reader) {
+
+        $elems = $reader->parseInnerTree([
+            '{urn:ietf:params:xml:ns:caldav}calendar-data' => 'Sabre\\CalDAV\\Xml\\Filter\\CalendarData',
+            '{DAV:}prop'                                   => 'Sabre\\Xml\\Element\\KeyValue',
+        ]);
+
+        $newProps = [
+            'hrefs'      => [],
+            'properties' => [],
+        ];
+
+        foreach ($elems as $elem) {
+
+            switch ($elem['name']) {
+
+                case '{DAV:}prop' :
+                    $newProps['properties'] = array_keys($elem['value']);
+                    if (isset($elem['value']['{' . Plugin::NS_CALDAV . '}calendar-data'])) {
+                        $newProps += $elem['value']['{' . Plugin::NS_CALDAV . '}calendar-data'];
+                    }
+                    break;
+                case '{DAV:}href' :
+                    $newProps['hrefs'][] = Uri\resolve($reader->contextUri, $elem['value']);
+                    break;
+
+            }
+
+        }
+
+        $obj = new self();
+        foreach ($newProps as $key => $value) {
+            $obj->$key = $value;
+        }
+
+        return $obj;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Request/CalendarQueryReport.php b/vendor/sabre/dav/lib/CalDAV/Xml/Request/CalendarQueryReport.php
new file mode 100644
index 000000000..848a4dc46
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Request/CalendarQueryReport.php
@@ -0,0 +1,139 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Request;
+
+use Sabre\Xml\XmlDeserializable;
+use Sabre\Xml\Reader;
+use Sabre\DAV\Exception\BadRequest;
+use Sabre\CalDAV\Plugin;
+
+/**
+ * CalendarQueryReport request parser.
+ *
+ * This class parses the {urn:ietf:params:xml:ns:caldav}calendar-query
+ * REPORT, as defined in:
+ *
+ * https://tools.ietf.org/html/rfc4791#section-7.9
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://www.rooftopsolutions.nl/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class CalendarQueryReport implements XmlDeserializable {
+
+    /**
+     * An array with requested properties.
+     *
+     * @var array
+     */
+    public $properties;
+
+    /**
+     * List of property/component filters.
+     *
+     * @var array
+     */
+    public $filters;
+
+    /**
+     * If the calendar data must be expanded, this will contain an array with 2
+     * elements: start and end.
+     *
+     * Each may be a DateTime or null.
+     *
+     * @var array|null
+     */
+    public $expand = null;
+
+    /**
+     * The mimetype of the content that should be returend. Usually
+     * text/calendar.
+     *
+     * @var string
+     */
+    public $contentType = null;
+
+    /**
+     * The version of calendar-data that should be returned. Usually '2.0',
+     * referring to iCalendar 2.0.
+     *
+     * @var string
+     */
+    public $version = null;
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * You are responsible for advancing the reader to the next element. Not
+     * doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Reader $reader) {
+
+        $elems = $reader->parseInnerTree([
+            '{urn:ietf:params:xml:ns:caldav}comp-filter'   => 'Sabre\\CalDAV\\Xml\\Filter\\CompFilter',
+            '{urn:ietf:params:xml:ns:caldav}prop-filter'   => 'Sabre\\CalDAV\\Xml\\Filter\\PropFilter',
+            '{urn:ietf:params:xml:ns:caldav}param-filter'  => 'Sabre\\CalDAV\\Xml\\Filter\\ParamFilter',
+            '{urn:ietf:params:xml:ns:caldav}calendar-data' => 'Sabre\\CalDAV\\Xml\\Filter\\CalendarData',
+            '{DAV:}prop'                                   => 'Sabre\\Xml\\Element\\KeyValue',
+        ]);
+
+        $newProps = [
+            'filters'    => null,
+            'properties' => [],
+        ];
+
+        if (!is_array($elems)) $elems = [];
+
+        foreach ($elems as $elem) {
+
+            switch ($elem['name']) {
+
+                case '{DAV:}prop' :
+                    $newProps['properties'] = array_keys($elem['value']);
+                    if (isset($elem['value']['{' . Plugin::NS_CALDAV . '}calendar-data'])) {
+                        $newProps += $elem['value']['{' . Plugin::NS_CALDAV . '}calendar-data'];
+                    }
+                    break;
+                case '{' . Plugin::NS_CALDAV . '}filter' :
+                    foreach ($elem['value'] as $subElem) {
+                        if ($subElem['name'] === '{' . Plugin::NS_CALDAV . '}comp-filter') {
+                            if (!is_null($newProps['filters'])) {
+                                throw new BadRequest('Only one top-level comp-filter may be defined');
+                            }
+                            $newProps['filters'] = $subElem['value'];
+                        }
+                    }
+                    break;
+
+            }
+
+        }
+
+        if (is_null($newProps['filters'])) {
+            throw new BadRequest('The {' . Plugin::NS_CALDAV . '}filter element is required for this request');
+        }
+
+        $obj = new self();
+        foreach ($newProps as $key => $value) {
+            $obj->$key = $value;
+        }
+        return $obj;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Request/FreeBusyQueryReport.php b/vendor/sabre/dav/lib/CalDAV/Xml/Request/FreeBusyQueryReport.php
new file mode 100644
index 000000000..e3b27d08e
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Request/FreeBusyQueryReport.php
@@ -0,0 +1,91 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Request;
+
+use Sabre\CalDAV\Plugin;
+use Sabre\DAV\Exception\BadRequest;
+use Sabre\VObject\DateTimeParser;
+use Sabre\Xml\Reader;
+use Sabre\Xml\XmlDeserializable;
+
+/**
+ * FreeBusyQueryReport
+ *
+ * This class parses the {DAV:}free-busy-query REPORT, as defined in:
+ *
+ * http://tools.ietf.org/html/rfc3253#section-3.8
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class FreeBusyQueryReport implements XmlDeserializable {
+
+    /**
+     * Starttime of report
+     *
+     * @var DateTime|null
+     */
+    public $start;
+
+    /**
+     * End time of report
+     *
+     * @var DateTime|null
+     */
+    public $end;
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * You are responsible for advancing the reader to the next element. Not
+     * doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Reader $reader) {
+
+        $timeRange = '{' . Plugin::NS_CALDAV . '}time-range';
+
+        $start = null;
+        $end = null;
+
+        foreach ((array)$reader->parseInnerTree([]) as $elem) {
+
+            if ($elem['name'] !== $timeRange) continue;
+
+            $start = empty($elem['attributes']['start']) ?: $elem['attributes']['start'];
+            $end = empty($elem['attributes']['end']) ?: $elem['attributes']['end'];
+
+        }
+        if (!$start && !$end) {
+            throw new BadRequest('The freebusy report must have a time-range element');
+        }
+        if ($start) {
+            $start = DateTimeParser::parseDateTime($start);
+        }
+        if ($end) {
+            $end = DateTimeParser::parseDateTime($end);
+        }
+        $result = new self();
+        $result->start = $start;
+        $result->end = $end;
+
+        return $result;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Request/InviteReply.php b/vendor/sabre/dav/lib/CalDAV/Xml/Request/InviteReply.php
new file mode 100644
index 000000000..ec627156f
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Request/InviteReply.php
@@ -0,0 +1,149 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Request;
+
+use Sabre\Xml\Reader;
+use Sabre\Xml\XmlDeserializable;
+use Sabre\Xml\Element\KeyValue;
+use Sabre\DAV\Exception\BadRequest;
+use Sabre\CalDAV\Plugin;
+use Sabre\CalDAV\SharingPlugin;
+
+/**
+ * Invite-reply POST request parser
+ *
+ * This class parses the invite-reply POST request, as defined in:
+ *
+ * http://svn.calendarserver.org/repository/calendarserver/CalendarServer/trunk/doc/Extensions/caldav-sharing.txt
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class InviteReply implements XmlDeserializable {
+
+    /**
+     * The sharee calendar user address.
+     *
+     * This is the address that the original invite was set to
+     *
+     * @var string
+     */
+    public $href;
+
+    /**
+     * The uri to the calendar that was being shared.
+     *
+     * @var string
+     */
+    public $calendarUri;
+
+    /**
+     * The id of the invite message that's being responded to
+     *
+     * @var string
+     */
+    public $inReplyTo;
+
+    /**
+     * An optional message
+     *
+     * @var string
+     */
+    public $summary;
+
+    /**
+     * Either SharingPlugin::STATUS_ACCEPTED or SharingPlugin::STATUS_DECLINED.
+     *
+     * @var int
+     */
+    public $status;
+
+    /**
+     * Constructor
+     *
+     * @param string $href
+     * @param string $calendarUri
+     * @param string $inReplyTo
+     * @param string $summary
+     * @param int $status
+     */
+    function __construct($href, $calendarUri, $inReplyTo, $summary, $status) {
+
+        $this->href = $href;
+        $this->calendarUri = $calendarUri;
+        $this->inReplyTo = $inReplyTo;
+        $this->summary = $summary;
+        $this->status = $status;
+
+    }
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * You are responsible for advancing the reader to the next element. Not
+     * doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Reader $reader) {
+
+        $elems = KeyValue::xmlDeserialize($reader);
+
+        $href = null;
+        $calendarUri = null;
+        $inReplyTo = null;
+        $summary = null;
+        $status = null;
+
+        foreach ($elems as $name => $value) {
+
+            switch ($name) {
+
+                case '{' . Plugin::NS_CALENDARSERVER . '}hosturl' :
+                    foreach ($value as $bla) {
+                        if ($bla['name'] === '{DAV:}href') {
+                            $calendarUri = $bla['value'];
+                        }
+                    }
+                    break;
+                case '{' . Plugin::NS_CALENDARSERVER . '}invite-accepted' :
+                    $status = SharingPlugin::STATUS_ACCEPTED;
+                    break;
+                case '{' . Plugin::NS_CALENDARSERVER . '}invite-declined' :
+                    $status = SharingPlugin::STATUS_DECLINED;
+                    break;
+                case '{' . Plugin::NS_CALENDARSERVER . '}in-reply-to' :
+                    $inReplyTo = $value;
+                    break;
+                case '{' . Plugin::NS_CALENDARSERVER . '}summary' :
+                    $summary = $value;
+                    break;
+                case '{DAV:}href' :
+                    $href = $value;
+                    break;
+            }
+
+        }
+        if (is_null($calendarUri)) {
+            throw new BadRequest('The {http://calendarserver.org/ns/}hosturl/{DAV:}href element must exist');
+        }
+
+        return new self($href, $calendarUri, $inReplyTo, $summary, $status);
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Request/MkCalendar.php b/vendor/sabre/dav/lib/CalDAV/Xml/Request/MkCalendar.php
new file mode 100644
index 000000000..7b745db55
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Request/MkCalendar.php
@@ -0,0 +1,79 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Request;
+
+use Sabre\Xml\Reader;
+use Sabre\Xml\XmlDeserializable;
+
+/**
+ * MKCALENDAR parser.
+ *
+ * This class parses the MKCALENDAR request, as defined in:
+ *
+ * https://tools.ietf.org/html/rfc4791#section-5.3.1
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class MkCalendar implements XmlDeserializable {
+
+    /**
+     * The list of properties that will be set.
+     *
+     * @var array
+     */
+    public $properties = [];
+
+    /**
+     * Returns the list of properties the calendar will be initialized with.
+     *
+     * @return array
+     */
+    function getProperties() {
+
+        return $this->properties;
+
+    }
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * You are responsible for advancing the reader to the next element. Not
+     * doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Reader $reader) {
+
+        $self = new self();
+
+        $elementMap = $reader->elementMap;
+        $elementMap['{DAV:}prop']   = 'Sabre\DAV\Xml\Element\Prop';
+        $elementMap['{DAV:}set']    = 'Sabre\Xml\Element\KeyValue';
+        $elems = $reader->parseInnerTree($elementMap);
+
+        foreach ($elems as $elem) {
+            if ($elem['name'] === '{DAV:}set') {
+                $self->properties = array_merge($self->properties, $elem['value']['{DAV:}prop']);
+            }
+        }
+
+        return $self;
+
+    }
+
+}
diff --git a/vendor/sabre/dav/lib/CalDAV/Xml/Request/Share.php b/vendor/sabre/dav/lib/CalDAV/Xml/Request/Share.php
new file mode 100644
index 000000000..dacc5dc94
--- /dev/null
+++ b/vendor/sabre/dav/lib/CalDAV/Xml/Request/Share.php
@@ -0,0 +1,116 @@
+<?php
+
+namespace Sabre\CalDAV\Xml\Request;
+
+use Sabre\Xml\Reader;
+use Sabre\Xml\XmlDeserializable;
+use Sabre\CalDAV\Plugin;
+
+/**
+ * Share POST request parser
+ *
+ * This class parses the share POST request, as defined in:
+ *
+ * http://svn.calendarserver.org/repository/calendarserver/CalendarServer/trunk/doc/Extensions/caldav-sharing.txt
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Share implements XmlDeserializable {
+
+    /**
+     * The list of new people added or updated.
+     *
+     * Every element has the following keys:
+     * 1. href - An email address
+     * 2. commonName - Some name
+     * 3. summary - An optional description of the share
+     * 4. readOnly - true or false
+     *
+     * @var array
+     */
+    public $set = [];
+
+    /**
+     * List of people removed from the share list.
+     *
+     * The list is a flat list of email addresses (including mailto:).
+     *
+     * @var array
+     */
+    public $remove = [];
+
+    /**
+     * Constructor
+     *
+     * @param array $set
+     * @param array $remove
+     */
+    function __construct(array $set, array $remove) {
+
+        $this->set = $set;
+        $this->remove = $remove;
+
+    }
+
+    /**
+     * The deserialize method is called during xml parsing.
+     *
+     * This method is called statictly, this is because in theory this method
+     * may be used as a type of constructor, or factory method.
+     *
+     * Often you want to return an instance of the current class, but you are
+     * free to return other data as well.
+     *
+     * You are responsible for advancing the reader to the next element. Not
+     * doing anything will result in a never-ending loop.
+     *
+     * If you just want to skip parsing for this element altogether, you can
+     * just call $reader->next();
+     *
+     * $reader->parseInnerTree() will parse the entire sub-tree, and advance to
+     * the next element.
+     *
+     * @param Reader $reader
+     * @return mixed
+     */
+    static function xmlDeserialize(Reader $reader) {
+
+        $elems = $reader->parseInnerTree([
+            '{' . Plugin::NS_CALENDARSERVER . '}set'    => 'Sabre\\Xml\\Element\\KeyValue',
+            '{' . Plugin::NS_CALENDARSERVER . '}remove' => 'Sabre\\Xml\\Element\\KeyValue',
+        ]);
+
+        $set = [];
+        $remove = [];
+
+        foreach ($elems as $elem) {
+            switch ($elem['name']) {
+
+                case '{' . Plugin::NS_CALENDARSERVER . '}set' :
+                    $sharee = $elem['value'];
+
+                    $sumElem = '{' . Plugin::NS_CALENDARSERVER . '}summary';
+                    $commonName = '{' . Plugin::NS_CALENDARSERVER . '}common-name';
+
+                    $set[] = [
+                        'href'       => $sharee['{DAV:}href'],
+                        'commonName' => isset($sharee[$commonName]) ? $sharee[$commonName] : null,
+                        'summary'    => isset($sharee[$sumElem]) ? $sharee[$sumElem] : null,
+                        'readOnly'   => !array_key_exists('{' . Plugin::NS_CALENDARSERVER . '}read-write', $sharee),
+                    ];
+                    break;
+
+                case '{' . Plugin::NS_CALENDARSERVER . '}remove' :
+                    $remove[] = $elem['value']['{DAV:}href'];
+                    break;
+
+            }
+        }
+
+        return new self($set, $remove);
+
+    }
+
+}