Merge remote-tracking branch 'upstream/dev' into plugin-repo

1 files changed, 989 insertions, 0 deletions

diff --git a/vendor/sabre/vobject/lib/ITip/Broker.php b/vendor/sabre/vobject/lib/ITip/Broker.php
new file mode 100644
index 000000000..effa74317
--- /dev/null
+++ b/vendor/sabre/vobject/lib/ITip/Broker.php
@@ -0,0 +1,989 @@
+<?php
+
+namespace Sabre\VObject\ITip;
+
+use Sabre\VObject\Component\VCalendar;
+use Sabre\VObject\DateTimeParser;
+use Sabre\VObject\Reader;
+use Sabre\VObject\Recur\EventIterator;
+
+/**
+ * The ITip\Broker class is a utility class that helps with processing
+ * so-called iTip messages.
+ *
+ * iTip is defined in rfc5546, stands for iCalendar Transport-Independent
+ * Interoperability Protocol, and describes the underlying mechanism for
+ * using iCalendar for scheduling for for example through email (also known as
+ * IMip) and CalDAV Scheduling.
+ *
+ * This class helps by:
+ *
+ * 1. Creating individual invites based on an iCalendar event for each
+ *    attendee.
+ * 2. Generating invite updates based on an iCalendar update. This may result
+ *    in new invites, updates and cancellations for attendees, if that list
+ *    changed.
+ * 3. On the receiving end, it can create a local iCalendar event based on
+ *    a received invite.
+ * 4. It can also process an invite update on a local event, ensuring that any
+ *    overridden properties from attendees are retained.
+ * 5. It can create a accepted or declined iTip reply based on an invite.
+ * 6. It can process a reply from an invite and update an events attendee
+ *     status based on a reply.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Broker {
+
+    /**
+     * This setting determines whether the rules for the SCHEDULE-AGENT
+     * parameter should be followed.
+     *
+     * This is a parameter defined on ATTENDEE properties, introduced by RFC
+     * 6638. This parameter allows a caldav client to tell the server 'Don't do
+     * any scheduling operations'.
+     *
+     * If this setting is turned on, any attendees with SCHEDULE-AGENT set to
+     * CLIENT will be ignored. This is the desired behavior for a CalDAV
+     * server, but if you're writing an iTip application that doesn't deal with
+     * CalDAV, you may want to ignore this parameter.
+     *
+     * @var bool
+     */
+    public $scheduleAgentServerRules = true;
+
+    /**
+     * The broker will try during 'parseEvent' figure out whether the change
+     * was significant.
+     *
+     * It uses a few different ways to do this. One of these ways is seeing if
+     * certain properties changed values. This list of specified here.
+     *
+     * This list is taken from:
+     * * http://tools.ietf.org/html/rfc5546#section-2.1.4
+     *
+     * @var string[]
+     */
+    public $significantChangeProperties = [
+        'DTSTART',
+        'DTEND',
+        'DURATION',
+        'DUE',
+        'RRULE',
+        'RDATE',
+        'EXDATE',
+        'STATUS',
+    ];
+
+    /**
+     * This method is used to process an incoming itip message.
+     *
+     * Examples:
+     *
+     * 1. A user is an attendee to an event. The organizer sends an updated
+     * meeting using a new iTip message with METHOD:REQUEST. This function
+     * will process the message and update the attendee's event accordingly.
+     *
+     * 2. The organizer cancelled the event using METHOD:CANCEL. We will update
+     * the users event to state STATUS:CANCELLED.
+     *
+     * 3. An attendee sent a reply to an invite using METHOD:REPLY. We can
+     * update the organizers event to update the ATTENDEE with its correct
+     * PARTSTAT.
+     *
+     * The $existingObject is updated in-place. If there is no existing object
+     * (because it's a new invite for example) a new object will be created.
+     *
+     * If an existing object does not exist, and the method was CANCEL or
+     * REPLY, the message effectively gets ignored, and no 'existingObject'
+     * will be created.
+     *
+     * The updated $existingObject is also returned from this function.
+     *
+     * If the iTip message was not supported, we will always return false.
+     *
+     * @param Message $itipMessage
+     * @param VCalendar $existingObject
+     *
+     * @return VCalendar|null
+     */
+    function processMessage(Message $itipMessage, VCalendar $existingObject = null) {
+
+        // We only support events at the moment.
+        if ($itipMessage->component !== 'VEVENT') {
+            return false;
+        }
+
+        switch ($itipMessage->method) {
+
+            case 'REQUEST' :
+                return $this->processMessageRequest($itipMessage, $existingObject);
+
+            case 'CANCEL' :
+                return $this->processMessageCancel($itipMessage, $existingObject);
+
+            case 'REPLY' :
+                return $this->processMessageReply($itipMessage, $existingObject);
+
+            default :
+                // Unsupported iTip message
+                return;
+
+        }
+
+        return $existingObject;
+
+    }
+
+    /**
+     * This function parses a VCALENDAR object and figure out if any messages
+     * need to be sent.
+     *
+     * A VCALENDAR object will be created from the perspective of either an
+     * attendee, or an organizer. You must pass a string identifying the
+     * current user, so we can figure out who in the list of attendees or the
+     * organizer we are sending this message on behalf of.
+     *
+     * It's possible to specify the current user as an array, in case the user
+     * has more than one identifying href (such as multiple emails).
+     *
+     * It $oldCalendar is specified, it is assumed that the operation is
+     * updating an existing event, which means that we need to look at the
+     * differences between events, and potentially send old attendees
+     * cancellations, and current attendees updates.
+     *
+     * If $calendar is null, but $oldCalendar is specified, we treat the
+     * operation as if the user has deleted an event. If the user was an
+     * organizer, this means that we need to send cancellation notices to
+     * people. If the user was an attendee, we need to make sure that the
+     * organizer gets the 'declined' message.
+     *
+     * @param VCalendar|string $calendar
+     * @param string|array $userHref
+     * @param VCalendar|string $oldCalendar
+     *
+     * @return array
+     */
+    function parseEvent($calendar = null, $userHref, $oldCalendar = null) {
+
+        if ($oldCalendar) {
+            if (is_string($oldCalendar)) {
+                $oldCalendar = Reader::read($oldCalendar);
+            }
+            if (!isset($oldCalendar->VEVENT)) {
+                // We only support events at the moment
+                return [];
+            }
+
+            $oldEventInfo = $this->parseEventInfo($oldCalendar);
+        } else {
+            $oldEventInfo = [
+                'organizer'             => null,
+                'significantChangeHash' => '',
+                'attendees'             => [],
+            ];
+        }
+
+        $userHref = (array)$userHref;
+
+        if (!is_null($calendar)) {
+
+            if (is_string($calendar)) {
+                $calendar = Reader::read($calendar);
+            }
+            if (!isset($calendar->VEVENT)) {
+                // We only support events at the moment
+                return [];
+            }
+            $eventInfo = $this->parseEventInfo($calendar);
+            if (!$eventInfo['attendees'] && !$oldEventInfo['attendees']) {
+                // If there were no attendees on either side of the equation,
+                // we don't need to do anything.
+                return [];
+            }
+            if (!$eventInfo['organizer'] && !$oldEventInfo['organizer']) {
+                // There was no organizer before or after the change.
+                return [];
+            }
+
+            $baseCalendar = $calendar;
+
+            // If the new object didn't have an organizer, the organizer
+            // changed the object from a scheduling object to a non-scheduling
+            // object. We just copy the info from the old object.
+            if (!$eventInfo['organizer'] && $oldEventInfo['organizer']) {
+                $eventInfo['organizer'] = $oldEventInfo['organizer'];
+                $eventInfo['organizerName'] = $oldEventInfo['organizerName'];
+            }
+
+        } else {
+            // The calendar object got deleted, we need to process this as a
+            // cancellation / decline.
+            if (!$oldCalendar) {
+                // No old and no new calendar, there's no thing to do.
+                return [];
+            }
+
+            $eventInfo = $oldEventInfo;
+
+            if (in_array($eventInfo['organizer'], $userHref)) {
+                // This is an organizer deleting the event.
+                $eventInfo['attendees'] = [];
+                // Increasing the sequence, but only if the organizer deleted
+                // the event.
+                $eventInfo['sequence']++;
+            } else {
+                // This is an attendee deleting the event.
+                foreach ($eventInfo['attendees'] as $key => $attendee) {
+                    if (in_array($attendee['href'], $userHref)) {
+                        $eventInfo['attendees'][$key]['instances'] = ['master' =>
+                            ['id' => 'master', 'partstat' => 'DECLINED']
+                        ];
+                    }
+                }
+            }
+            $baseCalendar = $oldCalendar;
+
+        }
+
+        if (in_array($eventInfo['organizer'], $userHref)) {
+            return $this->parseEventForOrganizer($baseCalendar, $eventInfo, $oldEventInfo);
+        } elseif ($oldCalendar) {
+            // We need to figure out if the user is an attendee, but we're only
+            // doing so if there's an oldCalendar, because we only want to
+            // process updates, not creation of new events.
+            foreach ($eventInfo['attendees'] as $attendee) {
+                if (in_array($attendee['href'], $userHref)) {
+                    return $this->parseEventForAttendee($baseCalendar, $eventInfo, $oldEventInfo, $attendee['href']);
+                }
+            }
+        }
+        return [];
+
+    }
+
+    /**
+     * Processes incoming REQUEST messages.
+     *
+     * This is message from an organizer, and is either a new event
+     * invite, or an update to an existing one.
+     *
+     *
+     * @param Message $itipMessage
+     * @param VCalendar $existingObject
+     *
+     * @return VCalendar|null
+     */
+    protected function processMessageRequest(Message $itipMessage, VCalendar $existingObject = null) {
+
+        if (!$existingObject) {
+            // This is a new invite, and we're just going to copy over
+            // all the components from the invite.
+            $existingObject = new VCalendar();
+            foreach ($itipMessage->message->getComponents() as $component) {
+                $existingObject->add(clone $component);
+            }
+        } else {
+            // We need to update an existing object with all the new
+            // information. We can just remove all existing components
+            // and create new ones.
+            foreach ($existingObject->getComponents() as $component) {
+                $existingObject->remove($component);
+            }
+            foreach ($itipMessage->message->getComponents() as $component) {
+                $existingObject->add(clone $component);
+            }
+        }
+        return $existingObject;
+
+    }
+
+    /**
+     * Processes incoming CANCEL messages.
+     *
+     * This is a message from an organizer, and means that either an
+     * attendee got removed from an event, or an event got cancelled
+     * altogether.
+     *
+     * @param Message $itipMessage
+     * @param VCalendar $existingObject
+     *
+     * @return VCalendar|null
+     */
+    protected function processMessageCancel(Message $itipMessage, VCalendar $existingObject = null) {
+
+        if (!$existingObject) {
+            // The event didn't exist in the first place, so we're just
+            // ignoring this message.
+        } else {
+            foreach ($existingObject->VEVENT as $vevent) {
+                $vevent->STATUS = 'CANCELLED';
+                $vevent->SEQUENCE = $itipMessage->sequence;
+            }
+        }
+        return $existingObject;
+
+    }
+
+    /**
+     * Processes incoming REPLY messages.
+     *
+     * The message is a reply. This is for example an attendee telling
+     * an organizer he accepted the invite, or declined it.
+     *
+     * @param Message $itipMessage
+     * @param VCalendar $existingObject
+     *
+     * @return VCalendar|null
+     */
+    protected function processMessageReply(Message $itipMessage, VCalendar $existingObject = null) {
+
+        // A reply can only be processed based on an existing object.
+        // If the object is not available, the reply is ignored.
+        if (!$existingObject) {
+            return;
+        }
+        $instances = [];
+        $requestStatus = '2.0';
+
+        // Finding all the instances the attendee replied to.
+        foreach ($itipMessage->message->VEVENT as $vevent) {
+            $recurId = isset($vevent->{'RECURRENCE-ID'}) ? $vevent->{'RECURRENCE-ID'}->getValue() : 'master';
+            $attendee = $vevent->ATTENDEE;
+            $instances[$recurId] = $attendee['PARTSTAT']->getValue();
+            if (isset($vevent->{'REQUEST-STATUS'})) {
+                $requestStatus = $vevent->{'REQUEST-STATUS'}->getValue();
+                list($requestStatus) = explode(';', $requestStatus);
+            }
+        }
+
+        // Now we need to loop through the original organizer event, to find
+        // all the instances where we have a reply for.
+        $masterObject = null;
+        foreach ($existingObject->VEVENT as $vevent) {
+            $recurId = isset($vevent->{'RECURRENCE-ID'}) ? $vevent->{'RECURRENCE-ID'}->getValue() : 'master';
+            if ($recurId === 'master') {
+                $masterObject = $vevent;
+            }
+            if (isset($instances[$recurId])) {
+                $attendeeFound = false;
+                if (isset($vevent->ATTENDEE)) {
+                    foreach ($vevent->ATTENDEE as $attendee) {
+                        if ($attendee->getValue() === $itipMessage->sender) {
+                            $attendeeFound = true;
+                            $attendee['PARTSTAT'] = $instances[$recurId];
+                            $attendee['SCHEDULE-STATUS'] = $requestStatus;
+                            // Un-setting the RSVP status, because we now know
+                            // that the attendee already replied.
+                            unset($attendee['RSVP']);
+                            break;
+                        }
+                    }
+                }
+                if (!$attendeeFound) {
+                    // Adding a new attendee. The iTip documentation calls this
+                    // a party crasher.
+                    $attendee = $vevent->add('ATTENDEE', $itipMessage->sender, [
+                        'PARTSTAT' => $instances[$recurId]
+                    ]);
+                    if ($itipMessage->senderName) $attendee['CN'] = $itipMessage->senderName;
+                }
+                unset($instances[$recurId]);
+            }
+        }
+
+        if (!$masterObject) {
+            // No master object, we can't add new instances.
+            return;
+        }
+        // If we got replies to instances that did not exist in the
+        // original list, it means that new exceptions must be created.
+        foreach ($instances as $recurId => $partstat) {
+
+            $recurrenceIterator = new EventIterator($existingObject, $itipMessage->uid);
+            $found = false;
+            $iterations = 1000;
+            do {
+
+                $newObject = $recurrenceIterator->getEventObject();
+                $recurrenceIterator->next();
+
+                if (isset($newObject->{'RECURRENCE-ID'}) && $newObject->{'RECURRENCE-ID'}->getValue() === $recurId) {
+                    $found = true;
+                }
+                $iterations--;
+
+            } while ($recurrenceIterator->valid() && !$found && $iterations);
+
+            // Invalid recurrence id. Skipping this object.
+            if (!$found) continue;
+
+            unset(
+                $newObject->RRULE,
+                $newObject->EXDATE,
+                $newObject->RDATE
+            );
+            $attendeeFound = false;
+            if (isset($newObject->ATTENDEE)) {
+                foreach ($newObject->ATTENDEE as $attendee) {
+                    if ($attendee->getValue() === $itipMessage->sender) {
+                        $attendeeFound = true;
+                        $attendee['PARTSTAT'] = $partstat;
+                        break;
+                    }
+                }
+            }
+            if (!$attendeeFound) {
+                // Adding a new attendee
+                $attendee = $newObject->add('ATTENDEE', $itipMessage->sender, [
+                    'PARTSTAT' => $partstat
+                ]);
+                if ($itipMessage->senderName) {
+                    $attendee['CN'] = $itipMessage->senderName;
+                }
+            }
+            $existingObject->add($newObject);
+
+        }
+        return $existingObject;
+
+    }
+
+    /**
+     * This method is used in cases where an event got updated, and we
+     * potentially need to send emails to attendees to let them know of updates
+     * in the events.
+     *
+     * We will detect which attendees got added, which got removed and create
+     * specific messages for these situations.
+     *
+     * @param VCalendar $calendar
+     * @param array $eventInfo
+     * @param array $oldEventInfo
+     *
+     * @return array
+     */
+    protected function parseEventForOrganizer(VCalendar $calendar, array $eventInfo, array $oldEventInfo) {
+
+        // Merging attendee lists.
+        $attendees = [];
+        foreach ($oldEventInfo['attendees'] as $attendee) {
+            $attendees[$attendee['href']] = [
+                'href'         => $attendee['href'],
+                'oldInstances' => $attendee['instances'],
+                'newInstances' => [],
+                'name'         => $attendee['name'],
+                'forceSend'    => null,
+            ];
+        }
+        foreach ($eventInfo['attendees'] as $attendee) {
+            if (isset($attendees[$attendee['href']])) {
+                $attendees[$attendee['href']]['name'] = $attendee['name'];
+                $attendees[$attendee['href']]['newInstances'] = $attendee['instances'];
+                $attendees[$attendee['href']]['forceSend'] = $attendee['forceSend'];
+            } else {
+                $attendees[$attendee['href']] = [
+                    'href'         => $attendee['href'],
+                    'oldInstances' => [],
+                    'newInstances' => $attendee['instances'],
+                    'name'         => $attendee['name'],
+                    'forceSend'    => $attendee['forceSend'],
+                ];
+            }
+        }
+
+        $messages = [];
+
+        foreach ($attendees as $attendee) {
+
+            // An organizer can also be an attendee. We should not generate any
+            // messages for those.
+            if ($attendee['href'] === $eventInfo['organizer']) {
+                continue;
+            }
+
+            $message = new Message();
+            $message->uid = $eventInfo['uid'];
+            $message->component = 'VEVENT';
+            $message->sequence = $eventInfo['sequence'];
+            $message->sender = $eventInfo['organizer'];
+            $message->senderName = $eventInfo['organizerName'];
+            $message->recipient = $attendee['href'];
+            $message->recipientName = $attendee['name'];
+
+            if (!$attendee['newInstances']) {
+
+                // If there are no instances the attendee is a part of, it
+                // means the attendee was removed and we need to send him a
+                // CANCEL.
+                $message->method = 'CANCEL';
+
+                // Creating the new iCalendar body.
+                $icalMsg = new VCalendar();
+                $icalMsg->METHOD = $message->method;
+                $event = $icalMsg->add('VEVENT', [
+                    'UID'      => $message->uid,
+                    'SEQUENCE' => $message->sequence,
+                ]);
+                if (isset($calendar->VEVENT->SUMMARY)) {
+                    $event->add('SUMMARY', $calendar->VEVENT->SUMMARY->getValue());
+                }
+                $event->add(clone $calendar->VEVENT->DTSTART);
+                if (isset($calendar->VEVENT->DTEND)) {
+                    $event->add(clone $calendar->VEVENT->DTEND);
+                } elseif (isset($calendar->VEVENT->DURATION)) {
+                    $event->add(clone $calendar->VEVENT->DURATION);
+                }
+                $org = $event->add('ORGANIZER', $eventInfo['organizer']);
+                if ($eventInfo['organizerName']) $org['CN'] = $eventInfo['organizerName'];
+                $event->add('ATTENDEE', $attendee['href'], [
+                    'CN' => $attendee['name'],
+                ]);
+                $message->significantChange = true;
+
+            } else {
+
+                // The attendee gets the updated event body
+                $message->method = 'REQUEST';
+
+                // Creating the new iCalendar body.
+                $icalMsg = new VCalendar();
+                $icalMsg->METHOD = $message->method;
+
+                foreach ($calendar->select('VTIMEZONE') as $timezone) {
+                    $icalMsg->add(clone $timezone);
+                }
+
+                // We need to find out that this change is significant. If it's
+                // not, systems may opt to not send messages.
+                //
+                // We do this based on the 'significantChangeHash' which is
+                // some value that changes if there's a certain set of
+                // properties changed in the event, or simply if there's a
+                // difference in instances that the attendee is invited to.
+
+                $message->significantChange =
+                    $attendee['forceSend'] === 'REQUEST' ||
+                    array_keys($attendee['oldInstances']) != array_keys($attendee['newInstances']) ||
+                    $oldEventInfo['significantChangeHash'] !== $eventInfo['significantChangeHash'];
+
+                foreach ($attendee['newInstances'] as $instanceId => $instanceInfo) {
+
+                    $currentEvent = clone $eventInfo['instances'][$instanceId];
+                    if ($instanceId === 'master') {
+
+                        // We need to find a list of events that the attendee
+                        // is not a part of to add to the list of exceptions.
+                        $exceptions = [];
+                        foreach ($eventInfo['instances'] as $instanceId => $vevent) {
+                            if (!isset($attendee['newInstances'][$instanceId])) {
+                                $exceptions[] = $instanceId;
+                            }
+                        }
+
+                        // If there were exceptions, we need to add it to an
+                        // existing EXDATE property, if it exists.
+                        if ($exceptions) {
+                            if (isset($currentEvent->EXDATE)) {
+                                $currentEvent->EXDATE->setParts(array_merge(
+                                    $currentEvent->EXDATE->getParts(),
+                                    $exceptions
+                                ));
+                            } else {
+                                $currentEvent->EXDATE = $exceptions;
+                            }
+                        }
+
+                        // Cleaning up any scheduling information that
+                        // shouldn't be sent along.
+                        unset($currentEvent->ORGANIZER['SCHEDULE-FORCE-SEND']);
+                        unset($currentEvent->ORGANIZER['SCHEDULE-STATUS']);
+
+                        foreach ($currentEvent->ATTENDEE as $attendee) {
+                            unset($attendee['SCHEDULE-FORCE-SEND']);
+                            unset($attendee['SCHEDULE-STATUS']);
+
+                            // We're adding PARTSTAT=NEEDS-ACTION to ensure that
+                            // iOS shows an "Inbox Item"
+                            if (!isset($attendee['PARTSTAT'])) {
+                                $attendee['PARTSTAT'] = 'NEEDS-ACTION';
+                            }
+
+                        }
+
+                    }
+
+                    $icalMsg->add($currentEvent);
+
+                }
+
+            }
+
+            $message->message = $icalMsg;
+            $messages[] = $message;
+
+        }
+
+        return $messages;
+
+    }
+
+    /**
+     * Parse an event update for an attendee.
+     *
+     * This function figures out if we need to send a reply to an organizer.
+     *
+     * @param VCalendar $calendar
+     * @param array $eventInfo
+     * @param array $oldEventInfo
+     * @param string $attendee
+     *
+     * @return Message[]
+     */
+    protected function parseEventForAttendee(VCalendar $calendar, array $eventInfo, array $oldEventInfo, $attendee) {
+
+        if ($this->scheduleAgentServerRules && $eventInfo['organizerScheduleAgent'] === 'CLIENT') {
+            return [];
+        }
+
+        // Don't bother generating messages for events that have already been
+        // cancelled.
+        if ($eventInfo['status'] === 'CANCELLED') {
+            return [];
+        }
+
+        $oldInstances = !empty($oldEventInfo['attendees'][$attendee]['instances']) ?
+            $oldEventInfo['attendees'][$attendee]['instances'] :
+            [];
+
+        $instances = [];
+        foreach ($oldInstances as $instance) {
+
+            $instances[$instance['id']] = [
+                'id'        => $instance['id'],
+                'oldstatus' => $instance['partstat'],
+                'newstatus' => null,
+            ];
+
+        }
+        foreach ($eventInfo['attendees'][$attendee]['instances'] as $instance) {
+
+            if (isset($instances[$instance['id']])) {
+                $instances[$instance['id']]['newstatus'] = $instance['partstat'];
+            } else {
+                $instances[$instance['id']] = [
+                    'id'        => $instance['id'],
+                    'oldstatus' => null,
+                    'newstatus' => $instance['partstat'],
+                ];
+            }
+
+        }
+
+        // We need to also look for differences in EXDATE. If there are new
+        // items in EXDATE, it means that an attendee deleted instances of an
+        // event, which means we need to send DECLINED specifically for those
+        // instances.
+        // We only need to do that though, if the master event is not declined.
+        if (isset($instances['master']) && $instances['master']['newstatus'] !== 'DECLINED') {
+            foreach ($eventInfo['exdate'] as $exDate) {
+
+                if (!in_array($exDate, $oldEventInfo['exdate'])) {
+                    if (isset($instances[$exDate])) {
+                        $instances[$exDate]['newstatus'] = 'DECLINED';
+                    } else {
+                        $instances[$exDate] = [
+                            'id'        => $exDate,
+                            'oldstatus' => null,
+                            'newstatus' => 'DECLINED',
+                        ];
+                    }
+                }
+
+            }
+        }
+
+        // Gathering a few extra properties for each instance.
+        foreach ($instances as $recurId => $instanceInfo) {
+
+            if (isset($eventInfo['instances'][$recurId])) {
+                $instances[$recurId]['dtstart'] = clone $eventInfo['instances'][$recurId]->DTSTART;
+            } else {
+                $instances[$recurId]['dtstart'] = $recurId;
+            }
+
+        }
+
+        $message = new Message();
+        $message->uid = $eventInfo['uid'];
+        $message->method = 'REPLY';
+        $message->component = 'VEVENT';
+        $message->sequence = $eventInfo['sequence'];
+        $message->sender = $attendee;
+        $message->senderName = $eventInfo['attendees'][$attendee]['name'];
+        $message->recipient = $eventInfo['organizer'];
+        $message->recipientName = $eventInfo['organizerName'];
+
+        $icalMsg = new VCalendar();
+        $icalMsg->METHOD = 'REPLY';
+
+        $hasReply = false;
+
+        foreach ($instances as $instance) {
+
+            if ($instance['oldstatus'] == $instance['newstatus'] && $eventInfo['organizerForceSend'] !== 'REPLY') {
+                // Skip
+                continue;
+            }
+
+            $event = $icalMsg->add('VEVENT', [
+                'UID'      => $message->uid,
+                'SEQUENCE' => $message->sequence,
+            ]);
+            $summary = isset($calendar->VEVENT->SUMMARY) ? $calendar->VEVENT->SUMMARY->getValue() : '';
+            // Adding properties from the correct source instance
+            if (isset($eventInfo['instances'][$instance['id']])) {
+                $instanceObj = $eventInfo['instances'][$instance['id']];
+                $event->add(clone $instanceObj->DTSTART);
+                if (isset($instanceObj->DTEND)) {
+                    $event->add(clone $instanceObj->DTEND);
+                } elseif (isset($instanceObj->DURATION)) {
+                    $event->add(clone $instanceObj->DURATION);
+                }
+                if (isset($instanceObj->SUMMARY)) {
+                    $event->add('SUMMARY', $instanceObj->SUMMARY->getValue());
+                } elseif ($summary) {
+                    $event->add('SUMMARY', $summary);
+                }
+            } else {
+                // This branch of the code is reached, when a reply is
+                // generated for an instance of a recurring event, through the
+                // fact that the instance has disappeared by showing up in
+                // EXDATE
+                $dt = DateTimeParser::parse($instance['id'], $eventInfo['timezone']);
+                // Treat is as a DATE field
+                if (strlen($instance['id']) <= 8) {
+                    $event->add('DTSTART', $dt, ['VALUE' => 'DATE']);
+                } else {
+                    $event->add('DTSTART', $dt);
+                }
+                if ($summary) {
+                    $event->add('SUMMARY', $summary);
+                }
+            }
+            if ($instance['id'] !== 'master') {
+                $dt = DateTimeParser::parse($instance['id'], $eventInfo['timezone']);
+                // Treat is as a DATE field
+                if (strlen($instance['id']) <= 8) {
+                    $event->add('RECURRENCE-ID', $dt, ['VALUE' => 'DATE']);
+                } else {
+                    $event->add('RECURRENCE-ID', $dt);
+                }
+            }
+            $organizer = $event->add('ORGANIZER', $message->recipient);
+            if ($message->recipientName) {
+                $organizer['CN'] = $message->recipientName;
+            }
+            $attendee = $event->add('ATTENDEE', $message->sender, [
+                'PARTSTAT' => $instance['newstatus']
+            ]);
+            if ($message->senderName) {
+                $attendee['CN'] = $message->senderName;
+            }
+            $hasReply = true;
+
+        }
+
+        if ($hasReply) {
+            $message->message = $icalMsg;
+            return [$message];
+        } else {
+            return [];
+        }
+
+    }
+
+    /**
+     * Returns attendee information and information about instances of an
+     * event.
+     *
+     * Returns an array with the following keys:
+     *
+     * 1. uid
+     * 2. organizer
+     * 3. organizerName
+     * 4. organizerScheduleAgent
+     * 5. organizerForceSend
+     * 6. instances
+     * 7. attendees
+     * 8. sequence
+     * 9. exdate
+     * 10. timezone - strictly the timezone on which the recurrence rule is
+     *                based on.
+     * 11. significantChangeHash
+     * 12. status
+     * @param VCalendar $calendar
+     *
+     * @return array
+     */
+    protected function parseEventInfo(VCalendar $calendar = null) {
+
+        $uid = null;
+        $organizer = null;
+        $organizerName = null;
+        $organizerForceSend = null;
+        $sequence = null;
+        $timezone = null;
+        $status = null;
+        $organizerScheduleAgent = 'SERVER';
+
+        $significantChangeHash = '';
+
+        // Now we need to collect a list of attendees, and which instances they
+        // are a part of.
+        $attendees = [];
+
+        $instances = [];
+        $exdate = [];
+
+        foreach ($calendar->VEVENT as $vevent) {
+
+            if (is_null($uid)) {
+                $uid = $vevent->UID->getValue();
+            } else {
+                if ($uid !== $vevent->UID->getValue()) {
+                    throw new ITipException('If a calendar contained more than one event, they must have the same UID.');
+                }
+            }
+
+            if (!isset($vevent->DTSTART)) {
+                throw new ITipException('An event MUST have a DTSTART property.');
+            }
+
+            if (isset($vevent->ORGANIZER)) {
+                if (is_null($organizer)) {
+                    $organizer = $vevent->ORGANIZER->getNormalizedValue();
+                    $organizerName = isset($vevent->ORGANIZER['CN']) ? $vevent->ORGANIZER['CN'] : null;
+                } else {
+                    if ($organizer !== $vevent->ORGANIZER->getNormalizedValue()) {
+                        throw new SameOrganizerForAllComponentsException('Every instance of the event must have the same organizer.');
+                    }
+                }
+                $organizerForceSend =
+                    isset($vevent->ORGANIZER['SCHEDULE-FORCE-SEND']) ?
+                    strtoupper($vevent->ORGANIZER['SCHEDULE-FORCE-SEND']) :
+                    null;
+                $organizerScheduleAgent =
+                    isset($vevent->ORGANIZER['SCHEDULE-AGENT']) ?
+                    strtoupper((string)$vevent->ORGANIZER['SCHEDULE-AGENT']) :
+                    'SERVER';
+            }
+            if (is_null($sequence) && isset($vevent->SEQUENCE)) {
+                $sequence = $vevent->SEQUENCE->getValue();
+            }
+            if (isset($vevent->EXDATE)) {
+                foreach ($vevent->select('EXDATE') as $val) {
+                    $exdate = array_merge($exdate, $val->getParts());
+                }
+                sort($exdate);
+            }
+            if (isset($vevent->STATUS)) {
+                $status = strtoupper($vevent->STATUS->getValue());
+            }
+
+            $recurId = isset($vevent->{'RECURRENCE-ID'}) ? $vevent->{'RECURRENCE-ID'}->getValue() : 'master';
+            if (is_null($timezone)) {
+                if ($recurId === 'master') {
+                    $timezone = $vevent->DTSTART->getDateTime()->getTimeZone();
+                } else {
+                    $timezone = $vevent->{'RECURRENCE-ID'}->getDateTime()->getTimeZone();
+                }
+            }
+            if (isset($vevent->ATTENDEE)) {
+                foreach ($vevent->ATTENDEE as $attendee) {
+
+                    if ($this->scheduleAgentServerRules &&
+                        isset($attendee['SCHEDULE-AGENT']) &&
+                        strtoupper($attendee['SCHEDULE-AGENT']->getValue()) === 'CLIENT'
+                    ) {
+                        continue;
+                    }
+                    $partStat =
+                        isset($attendee['PARTSTAT']) ?
+                        strtoupper($attendee['PARTSTAT']) :
+                        'NEEDS-ACTION';
+
+                    $forceSend =
+                        isset($attendee['SCHEDULE-FORCE-SEND']) ?
+                        strtoupper($attendee['SCHEDULE-FORCE-SEND']) :
+                        null;
+
+
+                    if (isset($attendees[$attendee->getNormalizedValue()])) {
+                        $attendees[$attendee->getNormalizedValue()]['instances'][$recurId] = [
+                            'id'         => $recurId,
+                            'partstat'   => $partStat,
+                            'force-send' => $forceSend,
+                        ];
+                    } else {
+                        $attendees[$attendee->getNormalizedValue()] = [
+                            'href'      => $attendee->getNormalizedValue(),
+                            'instances' => [
+                                $recurId => [
+                                    'id'       => $recurId,
+                                    'partstat' => $partStat,
+                                ],
+                            ],
+                            'name'      => isset($attendee['CN']) ? (string)$attendee['CN'] : null,
+                            'forceSend' => $forceSend,
+                        ];
+                    }
+
+                }
+                $instances[$recurId] = $vevent;
+
+            }
+
+            foreach ($this->significantChangeProperties as $prop) {
+                if (isset($vevent->$prop)) {
+                    $propertyValues = $vevent->select($prop);
+
+                    $significantChangeHash .= $prop . ':';
+
+                    if ($prop === 'EXDATE') {
+
+                        $significantChangeHash .= implode(',', $exdate) . ';';
+
+                    } else {
+
+                        foreach ($propertyValues as $val) {
+                            $significantChangeHash .= $val->getValue() . ';';
+                        }
+
+                    }
+                }
+            }
+
+        }
+        $significantChangeHash = md5($significantChangeHash);
+
+        return compact(
+            'uid',
+            'organizer',
+            'organizerName',
+            'organizerScheduleAgent',
+            'organizerForceSend',
+            'instances',
+            'attendees',
+            'sequence',
+            'exdate',
+            'timezone',
+            'significantChangeHash',
+            'status'
+        );
+
+    }
+
+}