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

5 files changed, 1644 insertions, 0 deletions

diff --git a/vendor/sabre/vobject/lib/Recur/EventIterator.php b/vendor/sabre/vobject/lib/Recur/EventIterator.php
new file mode 100644
index 000000000..86c996aec
--- /dev/null
+++ b/vendor/sabre/vobject/lib/Recur/EventIterator.php
@@ -0,0 +1,507 @@
+<?php
+
+namespace Sabre\VObject\Recur;
+
+use DateTimeZone;
+use DateTimeImmutable;
+use DateTimeInterface;
+use InvalidArgumentException;
+use Sabre\VObject\Component;
+use Sabre\VObject\Component\VEvent;
+use Sabre\VObject\Settings;
+
+/**
+ * This class is used to determine new for a recurring event, when the next
+ * events occur.
+ *
+ * This iterator may loop infinitely in the future, therefore it is important
+ * that if you use this class, you set hard limits for the amount of iterations
+ * you want to handle.
+ *
+ * Note that currently there is not full support for the entire iCalendar
+ * specification, as it's very complex and contains a lot of permutations
+ * that's not yet used very often in software.
+ *
+ * For the focus has been on features as they actually appear in Calendaring
+ * software, but this may well get expanded as needed / on demand
+ *
+ * The following RRULE properties are supported
+ *   * UNTIL
+ *   * INTERVAL
+ *   * COUNT
+ *   * FREQ=DAILY
+ *     * BYDAY
+ *     * BYHOUR
+ *     * BYMONTH
+ *   * FREQ=WEEKLY
+ *     * BYDAY
+ *     * BYHOUR
+ *     * WKST
+ *   * FREQ=MONTHLY
+ *     * BYMONTHDAY
+ *     * BYDAY
+ *     * BYSETPOS
+ *   * FREQ=YEARLY
+ *     * BYMONTH
+ *     * BYMONTHDAY (only if BYMONTH is also set)
+ *     * BYDAY (only if BYMONTH is also set)
+ *
+ * Anything beyond this is 'undefined', which means that it may get ignored, or
+ * you may get unexpected results. The effect is that in some applications the
+ * specified recurrence may look incorrect, or is missing.
+ *
+ * The recurrence iterator also does not yet support THISANDFUTURE.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class EventIterator implements \Iterator {
+
+    /**
+     * Reference timeZone for floating dates and times.
+     *
+     * @var DateTimeZone
+     */
+    protected $timeZone;
+
+    /**
+     * True if we're iterating an all-day event.
+     *
+     * @var bool
+     */
+    protected $allDay = false;
+
+    /**
+     * Creates the iterator.
+     *
+     * There's three ways to set up the iterator.
+     *
+     * 1. You can pass a VCALENDAR component and a UID.
+     * 2. You can pass an array of VEVENTs (all UIDS should match).
+     * 3. You can pass a single VEVENT component.
+     *
+     * Only the second method is recomended. The other 1 and 3 will be removed
+     * at some point in the future.
+     *
+     * The $uid parameter is only required for the first method.
+     *
+     * @param Component|array $input
+     * @param string|null $uid
+     * @param DateTimeZone $timeZone Reference timezone for floating dates and
+     *                               times.
+     */
+    function __construct($input, $uid = null, DateTimeZone $timeZone = null) {
+
+        if (is_null($timeZone)) {
+            $timeZone = new DateTimeZone('UTC');
+        }
+        $this->timeZone = $timeZone;
+
+        if (is_array($input)) {
+            $events = $input;
+        } elseif ($input instanceof VEvent) {
+            // Single instance mode.
+            $events = [$input];
+        } else {
+            // Calendar + UID mode.
+            $uid = (string)$uid;
+            if (!$uid) {
+                throw new InvalidArgumentException('The UID argument is required when a VCALENDAR is passed to this constructor');
+            }
+            if (!isset($input->VEVENT)) {
+                throw new InvalidArgumentException('No events found in this calendar');
+            }
+            $events = $input->getByUID($uid);
+
+        }
+
+        foreach ($events as $vevent) {
+
+            if (!isset($vevent->{'RECURRENCE-ID'})) {
+
+                $this->masterEvent = $vevent;
+
+            } else {
+
+                $this->exceptions[
+                    $vevent->{'RECURRENCE-ID'}->getDateTime($this->timeZone)->getTimeStamp()
+                ] = true;
+                $this->overriddenEvents[] = $vevent;
+
+            }
+
+        }
+
+        if (!$this->masterEvent) {
+            // No base event was found. CalDAV does allow cases where only
+            // overridden instances are stored.
+            //
+            // In this particular case, we're just going to grab the first
+            // event and use that instead. This may not always give the
+            // desired result.
+            if (!count($this->overriddenEvents)) {
+                throw new InvalidArgumentException('This VCALENDAR did not have an event with UID: ' . $uid);
+            }
+            $this->masterEvent = array_shift($this->overriddenEvents);
+        }
+
+        $this->startDate = $this->masterEvent->DTSTART->getDateTime($this->timeZone);
+        $this->allDay = !$this->masterEvent->DTSTART->hasTime();
+
+        if (isset($this->masterEvent->EXDATE)) {
+
+            foreach ($this->masterEvent->EXDATE as $exDate) {
+
+                foreach ($exDate->getDateTimes($this->timeZone) as $dt) {
+                    $this->exceptions[$dt->getTimeStamp()] = true;
+                }
+
+            }
+
+        }
+
+        if (isset($this->masterEvent->DTEND)) {
+            $this->eventDuration =
+                $this->masterEvent->DTEND->getDateTime($this->timeZone)->getTimeStamp() -
+                $this->startDate->getTimeStamp();
+        } elseif (isset($this->masterEvent->DURATION)) {
+            $duration = $this->masterEvent->DURATION->getDateInterval();
+            $end = clone $this->startDate;
+            $end = $end->add($duration);
+            $this->eventDuration = $end->getTimeStamp() - $this->startDate->getTimeStamp();
+        } elseif ($this->allDay) {
+            $this->eventDuration = 3600 * 24;
+        } else {
+            $this->eventDuration = 0;
+        }
+
+        if (isset($this->masterEvent->RDATE)) {
+            $this->recurIterator = new RDateIterator(
+                $this->masterEvent->RDATE->getParts(),
+                $this->startDate
+            );
+        } elseif (isset($this->masterEvent->RRULE)) {
+            $this->recurIterator = new RRuleIterator(
+                $this->masterEvent->RRULE->getParts(),
+                $this->startDate
+            );
+        } else {
+            $this->recurIterator = new RRuleIterator(
+                [
+                    'FREQ'  => 'DAILY',
+                    'COUNT' => 1,
+                ],
+                $this->startDate
+            );
+        }
+
+        $this->rewind();
+        if (!$this->valid()) {
+            throw new NoInstancesException('This recurrence rule does not generate any valid instances');
+        }
+
+    }
+
+    /**
+     * Returns the date for the current position of the iterator.
+     *
+     * @return DateTimeImmutable
+     */
+    function current() {
+
+        if ($this->currentDate) {
+            return clone $this->currentDate;
+        }
+
+    }
+
+    /**
+     * This method returns the start date for the current iteration of the
+     * event.
+     *
+     * @return DateTimeImmutable
+     */
+    function getDtStart() {
+
+        if ($this->currentDate) {
+            return clone $this->currentDate;
+        }
+
+    }
+
+    /**
+     * This method returns the end date for the current iteration of the
+     * event.
+     *
+     * @return DateTimeImmutable
+     */
+    function getDtEnd() {
+
+        if (!$this->valid()) {
+            return;
+        }
+        $end = clone $this->currentDate;
+        return $end->modify('+' . $this->eventDuration . ' seconds');
+
+    }
+
+    /**
+     * Returns a VEVENT for the current iterations of the event.
+     *
+     * This VEVENT will have a recurrence id, and it's DTSTART and DTEND
+     * altered.
+     *
+     * @return VEvent
+     */
+    function getEventObject() {
+
+        if ($this->currentOverriddenEvent) {
+            return $this->currentOverriddenEvent;
+        }
+
+        $event = clone $this->masterEvent;
+
+        // Ignoring the following block, because PHPUnit's code coverage
+        // ignores most of these lines, and this messes with our stats.
+        //
+        // @codeCoverageIgnoreStart
+        unset(
+            $event->RRULE,
+            $event->EXDATE,
+            $event->RDATE,
+            $event->EXRULE,
+            $event->{'RECURRENCE-ID'}
+        );
+        // @codeCoverageIgnoreEnd
+
+        $event->DTSTART->setDateTime($this->getDtStart(), $event->DTSTART->isFloating());
+        if (isset($event->DTEND)) {
+            $event->DTEND->setDateTime($this->getDtEnd(), $event->DTEND->isFloating());
+        }
+        $recurid = clone $event->DTSTART;
+        $recurid->name = 'RECURRENCE-ID';
+        $event->add($recurid);
+        return $event;
+
+    }
+
+    /**
+     * Returns the current position of the iterator.
+     *
+     * This is for us simply a 0-based index.
+     *
+     * @return int
+     */
+    function key() {
+
+        // The counter is always 1 ahead.
+        return $this->counter - 1;
+
+    }
+
+    /**
+     * This is called after next, to see if the iterator is still at a valid
+     * position, or if it's at the end.
+     *
+     * @return bool
+     */
+    function valid() {
+
+        if ($this->counter > Settings::$maxRecurrences && Settings::$maxRecurrences !== -1) {
+            throw new MaxInstancesExceededException('Recurring events are only allowed to generate ' . Settings::$maxRecurrences);
+        }
+        return !!$this->currentDate;
+
+    }
+
+    /**
+     * Sets the iterator back to the starting point.
+     */
+    function rewind() {
+
+        $this->recurIterator->rewind();
+        // re-creating overridden event index.
+        $index = [];
+        foreach ($this->overriddenEvents as $key => $event) {
+            $stamp = $event->DTSTART->getDateTime($this->timeZone)->getTimeStamp();
+            $index[$stamp] = $key;
+        }
+        krsort($index);
+        $this->counter = 0;
+        $this->overriddenEventsIndex = $index;
+        $this->currentOverriddenEvent = null;
+
+        $this->nextDate = null;
+        $this->currentDate = clone $this->startDate;
+
+        $this->next();
+
+    }
+
+    /**
+     * Advances the iterator with one step.
+     *
+     * @return void
+     */
+    function next() {
+
+        $this->currentOverriddenEvent = null;
+        $this->counter++;
+        if ($this->nextDate) {
+            // We had a stored value.
+            $nextDate = $this->nextDate;
+            $this->nextDate = null;
+        } else {
+            // We need to ask rruleparser for the next date.
+            // We need to do this until we find a date that's not in the
+            // exception list.
+            do {
+                if (!$this->recurIterator->valid()) {
+                    $nextDate = null;
+                    break;
+                }
+                $nextDate = $this->recurIterator->current();
+                $this->recurIterator->next();
+            } while (isset($this->exceptions[$nextDate->getTimeStamp()]));
+
+        }
+
+
+        // $nextDate now contains what rrule thinks is the next one, but an
+        // overridden event may cut ahead.
+        if ($this->overriddenEventsIndex) {
+
+            $offset = end($this->overriddenEventsIndex);
+            $timestamp = key($this->overriddenEventsIndex);
+            if (!$nextDate || $timestamp < $nextDate->getTimeStamp()) {
+                // Overridden event comes first.
+                $this->currentOverriddenEvent = $this->overriddenEvents[$offset];
+
+                // Putting the rrule next date aside.
+                $this->nextDate = $nextDate;
+                $this->currentDate = $this->currentOverriddenEvent->DTSTART->getDateTime($this->timeZone);
+
+                // Ensuring that this item will only be used once.
+                array_pop($this->overriddenEventsIndex);
+
+                // Exit point!
+                return;
+
+            }
+
+        }
+
+        $this->currentDate = $nextDate;
+
+    }
+
+    /**
+     * Quickly jump to a date in the future.
+     *
+     * @param DateTimeInterface $dateTime
+     */
+    function fastForward(DateTimeInterface $dateTime) {
+
+        while ($this->valid() && $this->getDtEnd() < $dateTime) {
+            $this->next();
+        }
+
+    }
+
+    /**
+     * Returns true if this recurring event never ends.
+     *
+     * @return bool
+     */
+    function isInfinite() {
+
+        return $this->recurIterator->isInfinite();
+
+    }
+
+    /**
+     * RRULE parser.
+     *
+     * @var RRuleIterator
+     */
+    protected $recurIterator;
+
+    /**
+     * The duration, in seconds, of the master event.
+     *
+     * We use this to calculate the DTEND for subsequent events.
+     */
+    protected $eventDuration;
+
+    /**
+     * A reference to the main (master) event.
+     *
+     * @var VEVENT
+     */
+    protected $masterEvent;
+
+    /**
+     * List of overridden events.
+     *
+     * @var array
+     */
+    protected $overriddenEvents = [];
+
+    /**
+     * Overridden event index.
+     *
+     * Key is timestamp, value is the index of the item in the $overriddenEvent
+     * property.
+     *
+     * @var array
+     */
+    protected $overriddenEventsIndex;
+
+    /**
+     * A list of recurrence-id's that are either part of EXDATE, or are
+     * overridden.
+     *
+     * @var array
+     */
+    protected $exceptions = [];
+
+    /**
+     * Internal event counter.
+     *
+     * @var int
+     */
+    protected $counter;
+
+    /**
+     * The very start of the iteration process.
+     *
+     * @var DateTimeImmutable
+     */
+    protected $startDate;
+
+    /**
+     * Where we are currently in the iteration process.
+     *
+     * @var DateTimeImmutable
+     */
+    protected $currentDate;
+
+    /**
+     * The next date from the rrule parser.
+     *
+     * Sometimes we need to temporary store the next date, because an
+     * overridden event came before.
+     *
+     * @var DateTimeImmutable
+     */
+    protected $nextDate;
+
+    /**
+     * The event that overwrites the current iteration
+     *
+     * @var VEVENT
+     */
+    protected $currentOverriddenEvent;
+
+}
diff --git a/vendor/sabre/vobject/lib/Recur/MaxInstancesExceededException.php b/vendor/sabre/vobject/lib/Recur/MaxInstancesExceededException.php
new file mode 100644
index 000000000..264df7d2b
--- /dev/null
+++ b/vendor/sabre/vobject/lib/Recur/MaxInstancesExceededException.php
@@ -0,0 +1,16 @@
+<?php
+
+namespace Sabre\VObject\Recur;
+
+use Exception;
+
+/**
+ * This exception will get thrown when a recurrence rule generated more than
+ * the maximum number of instances.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://code.google.com/p/sabredav/wiki/License Modified BSD License
+ */
+class MaxInstancesExceededException extends Exception {
+}
diff --git a/vendor/sabre/vobject/lib/Recur/NoInstancesException.php b/vendor/sabre/vobject/lib/Recur/NoInstancesException.php
new file mode 100644
index 000000000..8f8bb472b
--- /dev/null
+++ b/vendor/sabre/vobject/lib/Recur/NoInstancesException.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace Sabre\VObject\Recur;
+
+use Exception;
+
+/**
+ * This exception gets thrown when a recurrence iterator produces 0 instances.
+ *
+ * This may happen when every occurence in a rrule is also in EXDATE.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://code.google.com/p/sabredav/wiki/License Modified BSD License
+ */
+class NoInstancesException extends Exception {
+
+}
diff --git a/vendor/sabre/vobject/lib/Recur/RDateIterator.php b/vendor/sabre/vobject/lib/Recur/RDateIterator.php
new file mode 100644
index 000000000..f44960e12
--- /dev/null
+++ b/vendor/sabre/vobject/lib/Recur/RDateIterator.php
@@ -0,0 +1,182 @@
+<?php
+
+namespace Sabre\VObject\Recur;
+
+use DateTimeInterface;
+use Iterator;
+use Sabre\VObject\DateTimeParser;
+
+/**
+ * RRuleParser.
+ *
+ * This class receives an RRULE string, and allows you to iterate to get a list
+ * of dates in that recurrence.
+ *
+ * For instance, passing: FREQ=DAILY;LIMIT=5 will cause the iterator to contain
+ * 5 items, one for each day.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class RDateIterator implements Iterator {
+
+    /**
+     * Creates the Iterator.
+     *
+     * @param string|array $rrule
+     * @param DateTimeInterface $start
+     */
+    function __construct($rrule, DateTimeInterface $start) {
+
+        $this->startDate = $start;
+        $this->parseRDate($rrule);
+        $this->currentDate = clone $this->startDate;
+
+    }
+
+    /* Implementation of the Iterator interface {{{ */
+
+    function current() {
+
+        if (!$this->valid()) return;
+        return clone $this->currentDate;
+
+    }
+
+    /**
+     * Returns the current item number.
+     *
+     * @return int
+     */
+    function key() {
+
+        return $this->counter;
+
+    }
+
+    /**
+     * Returns whether the current item is a valid item for the recurrence
+     * iterator.
+     *
+     * @return bool
+     */
+    function valid() {
+
+        return ($this->counter <= count($this->dates));
+
+    }
+
+    /**
+     * Resets the iterator.
+     *
+     * @return void
+     */
+    function rewind() {
+
+        $this->currentDate = clone $this->startDate;
+        $this->counter = 0;
+
+    }
+
+    /**
+     * Goes on to the next iteration.
+     *
+     * @return void
+     */
+    function next() {
+
+        $this->counter++;
+        if (!$this->valid()) return;
+
+        $this->currentDate =
+            DateTimeParser::parse(
+                $this->dates[$this->counter - 1],
+                $this->startDate->getTimezone()
+            );
+
+    }
+
+    /* End of Iterator implementation }}} */
+
+    /**
+     * Returns true if this recurring event never ends.
+     *
+     * @return bool
+     */
+    function isInfinite() {
+
+        return false;
+
+    }
+
+    /**
+     * This method allows you to quickly go to the next occurrence after the
+     * specified date.
+     *
+     * @param DateTimeInterface $dt
+     *
+     * @return void
+     */
+    function fastForward(DateTimeInterface $dt) {
+
+        while ($this->valid() && $this->currentDate < $dt) {
+            $this->next();
+        }
+
+    }
+
+    /**
+     * The reference start date/time for the rrule.
+     *
+     * All calculations are based on this initial date.
+     *
+     * @var DateTimeInterface
+     */
+    protected $startDate;
+
+    /**
+     * The date of the current iteration. You can get this by calling
+     * ->current().
+     *
+     * @var DateTimeInterface
+     */
+    protected $currentDate;
+
+    /**
+     * The current item in the list.
+     *
+     * You can get this number with the key() method.
+     *
+     * @var int
+     */
+    protected $counter = 0;
+
+    /* }}} */
+
+    /**
+     * This method receives a string from an RRULE property, and populates this
+     * class with all the values.
+     *
+     * @param string|array $rrule
+     *
+     * @return void
+     */
+    protected function parseRDate($rdate) {
+
+        if (is_string($rdate)) {
+            $rdate = explode(',', $rdate);
+        }
+
+        $this->dates = $rdate;
+
+    }
+
+    /**
+     * Array with the RRULE dates
+     *
+     * @var array
+     */
+    protected $dates = [];
+
+}
diff --git a/vendor/sabre/vobject/lib/Recur/RRuleIterator.php b/vendor/sabre/vobject/lib/Recur/RRuleIterator.php
new file mode 100644
index 000000000..402e2de83
--- /dev/null
+++ b/vendor/sabre/vobject/lib/Recur/RRuleIterator.php
@@ -0,0 +1,921 @@
+<?php
+
+namespace Sabre\VObject\Recur;
+
+use DateTimeInterface;
+use DateTimeImmutable;
+use Iterator;
+use Sabre\VObject\DateTimeParser;
+use Sabre\VObject\InvalidDataException;
+use Sabre\VObject\Property;
+
+/**
+ * RRuleParser.
+ *
+ * This class receives an RRULE string, and allows you to iterate to get a list
+ * of dates in that recurrence.
+ *
+ * For instance, passing: FREQ=DAILY;LIMIT=5 will cause the iterator to contain
+ * 5 items, one for each day.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class RRuleIterator implements Iterator {
+
+    /**
+     * Creates the Iterator.
+     *
+     * @param string|array $rrule
+     * @param DateTimeInterface $start
+     */
+    function __construct($rrule, DateTimeInterface $start) {
+
+        $this->startDate = $start;
+        $this->parseRRule($rrule);
+        $this->currentDate = clone $this->startDate;
+
+    }
+
+    /* Implementation of the Iterator interface {{{ */
+
+    function current() {
+
+        if (!$this->valid()) return;
+        return clone $this->currentDate;
+
+    }
+
+    /**
+     * Returns the current item number.
+     *
+     * @return int
+     */
+    function key() {
+
+        return $this->counter;
+
+    }
+
+    /**
+     * Returns whether the current item is a valid item for the recurrence
+     * iterator. This will return false if we've gone beyond the UNTIL or COUNT
+     * statements.
+     *
+     * @return bool
+     */
+    function valid() {
+
+        if (!is_null($this->count)) {
+            return $this->counter < $this->count;
+        }
+        return is_null($this->until) || $this->currentDate <= $this->until;
+
+    }
+
+    /**
+     * Resets the iterator.
+     *
+     * @return void
+     */
+    function rewind() {
+
+        $this->currentDate = clone $this->startDate;
+        $this->counter = 0;
+
+    }
+
+    /**
+     * Goes on to the next iteration.
+     *
+     * @return void
+     */
+    function next() {
+
+        // Otherwise, we find the next event in the normal RRULE
+        // sequence.
+        switch ($this->frequency) {
+
+            case 'hourly' :
+                $this->nextHourly();
+                break;
+
+            case 'daily' :
+                $this->nextDaily();
+                break;
+
+            case 'weekly' :
+                $this->nextWeekly();
+                break;
+
+            case 'monthly' :
+                $this->nextMonthly();
+                break;
+
+            case 'yearly' :
+                $this->nextYearly();
+                break;
+
+        }
+        $this->counter++;
+
+    }
+
+    /* End of Iterator implementation }}} */
+
+    /**
+     * Returns true if this recurring event never ends.
+     *
+     * @return bool
+     */
+    function isInfinite() {
+
+        return !$this->count && !$this->until;
+
+    }
+
+    /**
+     * This method allows you to quickly go to the next occurrence after the
+     * specified date.
+     *
+     * @param DateTimeInterface $dt
+     *
+     * @return void
+     */
+    function fastForward(DateTimeInterface $dt) {
+
+        while ($this->valid() && $this->currentDate < $dt) {
+            $this->next();
+        }
+
+    }
+
+    /**
+     * The reference start date/time for the rrule.
+     *
+     * All calculations are based on this initial date.
+     *
+     * @var DateTimeInterface
+     */
+    protected $startDate;
+
+    /**
+     * The date of the current iteration. You can get this by calling
+     * ->current().
+     *
+     * @var DateTimeInterface
+     */
+    protected $currentDate;
+
+    /**
+     * Frequency is one of: secondly, minutely, hourly, daily, weekly, monthly,
+     * yearly.
+     *
+     * @var string
+     */
+    protected $frequency;
+
+    /**
+     * The number of recurrences, or 'null' if infinitely recurring.
+     *
+     * @var int
+     */
+    protected $count;
+
+    /**
+     * The interval.
+     *
+     * If for example frequency is set to daily, interval = 2 would mean every
+     * 2 days.
+     *
+     * @var int
+     */
+    protected $interval = 1;
+
+    /**
+     * The last instance of this recurrence, inclusively.
+     *
+     * @var DateTimeInterface|null
+     */
+    protected $until;
+
+    /**
+     * Which seconds to recur.
+     *
+     * This is an array of integers (between 0 and 60)
+     *
+     * @var array
+     */
+    protected $bySecond;
+
+    /**
+     * Which minutes to recur.
+     *
+     * This is an array of integers (between 0 and 59)
+     *
+     * @var array
+     */
+    protected $byMinute;
+
+    /**
+     * Which hours to recur.
+     *
+     * This is an array of integers (between 0 and 23)
+     *
+     * @var array
+     */
+    protected $byHour;
+
+    /**
+     * The current item in the list.
+     *
+     * You can get this number with the key() method.
+     *
+     * @var int
+     */
+    protected $counter = 0;
+
+    /**
+     * Which weekdays to recur.
+     *
+     * This is an array of weekdays
+     *
+     * This may also be preceeded by a positive or negative integer. If present,
+     * this indicates the nth occurrence of a specific day within the monthly or
+     * yearly rrule. For instance, -2TU indicates the second-last tuesday of
+     * the month, or year.
+     *
+     * @var array
+     */
+    protected $byDay;
+
+    /**
+     * Which days of the month to recur.
+     *
+     * This is an array of days of the months (1-31). The value can also be
+     * negative. -5 for instance means the 5th last day of the month.
+     *
+     * @var array
+     */
+    protected $byMonthDay;
+
+    /**
+     * Which days of the year to recur.
+     *
+     * This is an array with days of the year (1 to 366). The values can also
+     * be negative. For instance, -1 will always represent the last day of the
+     * year. (December 31st).
+     *
+     * @var array
+     */
+    protected $byYearDay;
+
+    /**
+     * Which week numbers to recur.
+     *
+     * This is an array of integers from 1 to 53. The values can also be
+     * negative. -1 will always refer to the last week of the year.
+     *
+     * @var array
+     */
+    protected $byWeekNo;
+
+    /**
+     * Which months to recur.
+     *
+     * This is an array of integers from 1 to 12.
+     *
+     * @var array
+     */
+    protected $byMonth;
+
+    /**
+     * Which items in an existing st to recur.
+     *
+     * These numbers work together with an existing by* rule. It specifies
+     * exactly which items of the existing by-rule to filter.
+     *
+     * Valid values are 1 to 366 and -1 to -366. As an example, this can be
+     * used to recur the last workday of the month.
+     *
+     * This would be done by setting frequency to 'monthly', byDay to
+     * 'MO,TU,WE,TH,FR' and bySetPos to -1.
+     *
+     * @var array
+     */
+    protected $bySetPos;
+
+    /**
+     * When the week starts.
+     *
+     * @var string
+     */
+    protected $weekStart = 'MO';
+
+    /* Functions that advance the iterator {{{ */
+
+    /**
+     * Does the processing for advancing the iterator for hourly frequency.
+     *
+     * @return void
+     */
+    protected function nextHourly() {
+
+        $this->currentDate = $this->currentDate->modify('+' . $this->interval . ' hours');
+
+    }
+
+    /**
+     * Does the processing for advancing the iterator for daily frequency.
+     *
+     * @return void
+     */
+    protected function nextDaily() {
+
+        if (!$this->byHour && !$this->byDay) {
+            $this->currentDate = $this->currentDate->modify('+' . $this->interval . ' days');
+            return;
+        }
+
+        if (!empty($this->byHour)) {
+            $recurrenceHours = $this->getHours();
+        }
+
+        if (!empty($this->byDay)) {
+            $recurrenceDays = $this->getDays();
+        }
+
+        if (!empty($this->byMonth)) {
+            $recurrenceMonths = $this->getMonths();
+        }
+
+        do {
+            if ($this->byHour) {
+                if ($this->currentDate->format('G') == '23') {
+                    // to obey the interval rule
+                    $this->currentDate = $this->currentDate->modify('+' . $this->interval - 1 . ' days');
+                }
+
+                $this->currentDate = $this->currentDate->modify('+1 hours');
+
+            } else {
+                $this->currentDate = $this->currentDate->modify('+' . $this->interval . ' days');
+
+            }
+
+            // Current month of the year
+            $currentMonth = $this->currentDate->format('n');
+
+            // Current day of the week
+            $currentDay = $this->currentDate->format('w');
+
+            // Current hour of the day
+            $currentHour = $this->currentDate->format('G');
+
+        } while (
+            ($this->byDay   && !in_array($currentDay, $recurrenceDays)) ||
+            ($this->byHour  && !in_array($currentHour, $recurrenceHours)) ||
+            ($this->byMonth && !in_array($currentMonth, $recurrenceMonths))
+        );
+
+    }
+
+    /**
+     * Does the processing for advancing the iterator for weekly frequency.
+     *
+     * @return void
+     */
+    protected function nextWeekly() {
+
+        if (!$this->byHour && !$this->byDay) {
+            $this->currentDate = $this->currentDate->modify('+' . $this->interval . ' weeks');
+            return;
+        }
+
+        if ($this->byHour) {
+            $recurrenceHours = $this->getHours();
+        }
+
+        if ($this->byDay) {
+            $recurrenceDays = $this->getDays();
+        }
+
+        // First day of the week:
+        $firstDay = $this->dayMap[$this->weekStart];
+
+        do {
+
+            if ($this->byHour) {
+                $this->currentDate = $this->currentDate->modify('+1 hours');
+            } else {
+                $this->currentDate = $this->currentDate->modify('+1 days');
+            }
+
+            // Current day of the week
+            $currentDay = (int)$this->currentDate->format('w');
+
+            // Current hour of the day
+            $currentHour = (int)$this->currentDate->format('G');
+
+            // We need to roll over to the next week
+            if ($currentDay === $firstDay && (!$this->byHour || $currentHour == '0')) {
+                $this->currentDate = $this->currentDate->modify('+' . $this->interval - 1 . ' weeks');
+
+                // We need to go to the first day of this week, but only if we
+                // are not already on this first day of this week.
+                if ($this->currentDate->format('w') != $firstDay) {
+                    $this->currentDate = $this->currentDate->modify('last ' . $this->dayNames[$this->dayMap[$this->weekStart]]);
+                }
+            }
+
+            // We have a match
+        } while (($this->byDay && !in_array($currentDay, $recurrenceDays)) || ($this->byHour && !in_array($currentHour, $recurrenceHours)));
+    }
+
+    /**
+     * Does the processing for advancing the iterator for monthly frequency.
+     *
+     * @return void
+     */
+    protected function nextMonthly() {
+
+        $currentDayOfMonth = $this->currentDate->format('j');
+        if (!$this->byMonthDay && !$this->byDay) {
+
+            // If the current day is higher than the 28th, rollover can
+            // occur to the next month. We Must skip these invalid
+            // entries.
+            if ($currentDayOfMonth < 29) {
+                $this->currentDate = $this->currentDate->modify('+' . $this->interval . ' months');
+            } else {
+                $increase = 0;
+                do {
+                    $increase++;
+                    $tempDate = clone $this->currentDate;
+                    $tempDate = $tempDate->modify('+ ' . ($this->interval * $increase) . ' months');
+                } while ($tempDate->format('j') != $currentDayOfMonth);
+                $this->currentDate = $tempDate;
+            }
+            return;
+        }
+
+        while (true) {
+
+            $occurrences = $this->getMonthlyOccurrences();
+
+            foreach ($occurrences as $occurrence) {
+
+                // The first occurrence thats higher than the current
+                // day of the month wins.
+                if ($occurrence > $currentDayOfMonth) {
+                    break 2;
+                }
+
+            }
+
+            // If we made it all the way here, it means there were no
+            // valid occurrences, and we need to advance to the next
+            // month.
+            //
+            // This line does not currently work in hhvm. Temporary workaround
+            // follows:
+            // $this->currentDate->modify('first day of this month');
+            $this->currentDate = new DateTimeImmutable($this->currentDate->format('Y-m-1 H:i:s'), $this->currentDate->getTimezone());
+            // end of workaround
+            $this->currentDate = $this->currentDate->modify('+ ' . $this->interval . ' months');
+
+            // This goes to 0 because we need to start counting at the
+            // beginning.
+            $currentDayOfMonth = 0;
+
+        }
+
+        $this->currentDate = $this->currentDate->setDate(
+            (int)$this->currentDate->format('Y'),
+            (int)$this->currentDate->format('n'),
+            (int)$occurrence
+        );
+
+    }
+
+    /**
+     * Does the processing for advancing the iterator for yearly frequency.
+     *
+     * @return void
+     */
+    protected function nextYearly() {
+
+        $currentMonth = $this->currentDate->format('n');
+        $currentYear = $this->currentDate->format('Y');
+        $currentDayOfMonth = $this->currentDate->format('j');
+
+        // No sub-rules, so we just advance by year
+        if (empty($this->byMonth)) {
+
+            // Unless it was a leap day!
+            if ($currentMonth == 2 && $currentDayOfMonth == 29) {
+
+                $counter = 0;
+                do {
+                    $counter++;
+                    // Here we increase the year count by the interval, until
+                    // we hit a date that's also in a leap year.
+                    //
+                    // We could just find the next interval that's dividable by
+                    // 4, but that would ignore the rule that there's no leap
+                    // year every year that's dividable by a 100, but not by
+                    // 400. (1800, 1900, 2100). So we just rely on the datetime
+                    // functions instead.
+                    $nextDate = clone $this->currentDate;
+                    $nextDate = $nextDate->modify('+ ' . ($this->interval * $counter) . ' years');
+                } while ($nextDate->format('n') != 2);
+
+                $this->currentDate = $nextDate;
+
+                return;
+
+            }
+
+            // The easiest form
+            $this->currentDate = $this->currentDate->modify('+' . $this->interval . ' years');
+            return;
+
+        }
+
+        $currentMonth = $this->currentDate->format('n');
+        $currentYear = $this->currentDate->format('Y');
+        $currentDayOfMonth = $this->currentDate->format('j');
+
+        $advancedToNewMonth = false;
+
+        // If we got a byDay or getMonthDay filter, we must first expand
+        // further.
+        if ($this->byDay || $this->byMonthDay) {
+
+            while (true) {
+
+                $occurrences = $this->getMonthlyOccurrences();
+
+                foreach ($occurrences as $occurrence) {
+
+                    // The first occurrence that's higher than the current
+                    // day of the month wins.
+                    // If we advanced to the next month or year, the first
+                    // occurrence is always correct.
+                    if ($occurrence > $currentDayOfMonth || $advancedToNewMonth) {
+                        break 2;
+                    }
+
+                }
+
+                // If we made it here, it means we need to advance to
+                // the next month or year.
+                $currentDayOfMonth = 1;
+                $advancedToNewMonth = true;
+                do {
+
+                    $currentMonth++;
+                    if ($currentMonth > 12) {
+                        $currentYear += $this->interval;
+                        $currentMonth = 1;
+                    }
+                } while (!in_array($currentMonth, $this->byMonth));
+
+                $this->currentDate = $this->currentDate->setDate(
+                    (int)$currentYear,
+                    (int)$currentMonth,
+                    (int)$currentDayOfMonth
+                );
+
+            }
+
+            // If we made it here, it means we got a valid occurrence
+            $this->currentDate = $this->currentDate->setDate(
+                (int)$currentYear,
+                (int)$currentMonth,
+                (int)$occurrence
+            );
+            return;
+
+        } else {
+
+            // These are the 'byMonth' rules, if there are no byDay or
+            // byMonthDay sub-rules.
+            do {
+
+                $currentMonth++;
+                if ($currentMonth > 12) {
+                    $currentYear += $this->interval;
+                    $currentMonth = 1;
+                }
+            } while (!in_array($currentMonth, $this->byMonth));
+            $this->currentDate = $this->currentDate->setDate(
+                (int)$currentYear,
+                (int)$currentMonth,
+                (int)$currentDayOfMonth
+            );
+
+            return;
+
+        }
+
+    }
+
+    /* }}} */
+
+    /**
+     * This method receives a string from an RRULE property, and populates this
+     * class with all the values.
+     *
+     * @param string|array $rrule
+     *
+     * @return void
+     */
+    protected function parseRRule($rrule) {
+
+        if (is_string($rrule)) {
+            $rrule = Property\ICalendar\Recur::stringToArray($rrule);
+        }
+
+        foreach ($rrule as $key => $value) {
+
+            $key = strtoupper($key);
+            switch ($key) {
+
+                case 'FREQ' :
+                    $value = strtolower($value);
+                    if (!in_array(
+                        $value,
+                        ['secondly', 'minutely', 'hourly', 'daily', 'weekly', 'monthly', 'yearly']
+                    )) {
+                        throw new InvalidDataException('Unknown value for FREQ=' . strtoupper($value));
+                    }
+                    $this->frequency = $value;
+                    break;
+
+                case 'UNTIL' :
+                    $this->until = DateTimeParser::parse($value, $this->startDate->getTimezone());
+
+                    // In some cases events are generated with an UNTIL=
+                    // parameter before the actual start of the event.
+                    //
+                    // Not sure why this is happening. We assume that the
+                    // intention was that the event only recurs once.
+                    //
+                    // So we are modifying the parameter so our code doesn't
+                    // break.
+                    if ($this->until < $this->startDate) {
+                        $this->until = $this->startDate;
+                    }
+                    break;
+
+                case 'INTERVAL' :
+                    // No break
+
+                case 'COUNT' :
+                    $val = (int)$value;
+                    if ($val < 1) {
+                        throw new InvalidDataException(strtoupper($key) . ' in RRULE must be a positive integer!');
+                    }
+                    $key = strtolower($key);
+                    $this->$key = $val;
+                    break;
+
+                case 'BYSECOND' :
+                    $this->bySecond = (array)$value;
+                    break;
+
+                case 'BYMINUTE' :
+                    $this->byMinute = (array)$value;
+                    break;
+
+                case 'BYHOUR' :
+                    $this->byHour = (array)$value;
+                    break;
+
+                case 'BYDAY' :
+                    $value = (array)$value;
+                    foreach ($value as $part) {
+                        if (!preg_match('#^  (-|\+)? ([1-5])? (MO|TU|WE|TH|FR|SA|SU) $# xi', $part)) {
+                            throw new InvalidDataException('Invalid part in BYDAY clause: ' . $part);
+                        }
+                    }
+                    $this->byDay = $value;
+                    break;
+
+                case 'BYMONTHDAY' :
+                    $this->byMonthDay = (array)$value;
+                    break;
+
+                case 'BYYEARDAY' :
+                    $this->byYearDay = (array)$value;
+                    break;
+
+                case 'BYWEEKNO' :
+                    $this->byWeekNo = (array)$value;
+                    break;
+
+                case 'BYMONTH' :
+                    $this->byMonth = (array)$value;
+                    break;
+
+                case 'BYSETPOS' :
+                    $this->bySetPos = (array)$value;
+                    break;
+
+                case 'WKST' :
+                    $this->weekStart = strtoupper($value);
+                    break;
+
+                default:
+                    throw new InvalidDataException('Not supported: ' . strtoupper($key));
+
+            }
+
+        }
+
+    }
+
+    /**
+     * Mappings between the day number and english day name.
+     *
+     * @var array
+     */
+    protected $dayNames = [
+        0 => 'Sunday',
+        1 => 'Monday',
+        2 => 'Tuesday',
+        3 => 'Wednesday',
+        4 => 'Thursday',
+        5 => 'Friday',
+        6 => 'Saturday',
+    ];
+
+    /**
+     * Returns all the occurrences for a monthly frequency with a 'byDay' or
+     * 'byMonthDay' expansion for the current month.
+     *
+     * The returned list is an array of integers with the day of month (1-31).
+     *
+     * @return array
+     */
+    protected function getMonthlyOccurrences() {
+
+        $startDate = clone $this->currentDate;
+
+        $byDayResults = [];
+
+        // Our strategy is to simply go through the byDays, advance the date to
+        // that point and add it to the results.
+        if ($this->byDay) foreach ($this->byDay as $day) {
+
+            $dayName = $this->dayNames[$this->dayMap[substr($day, -2)]];
+
+
+            // Dayname will be something like 'wednesday'. Now we need to find
+            // all wednesdays in this month.
+            $dayHits = [];
+
+            // workaround for missing 'first day of the month' support in hhvm
+            $checkDate = new \DateTime($startDate->format('Y-m-1'));
+            // workaround modify always advancing the date even if the current day is a $dayName in hhvm
+            if ($checkDate->format('l') !== $dayName) {
+                $checkDate = $checkDate->modify($dayName);
+            }
+
+            do {
+                $dayHits[] = $checkDate->format('j');
+                $checkDate = $checkDate->modify('next ' . $dayName);
+            } while ($checkDate->format('n') === $startDate->format('n'));
+
+            // So now we have 'all wednesdays' for month. It is however
+            // possible that the user only really wanted the 1st, 2nd or last
+            // wednesday.
+            if (strlen($day) > 2) {
+                $offset = (int)substr($day, 0, -2);
+
+                if ($offset > 0) {
+                    // It is possible that the day does not exist, such as a
+                    // 5th or 6th wednesday of the month.
+                    if (isset($dayHits[$offset - 1])) {
+                        $byDayResults[] = $dayHits[$offset - 1];
+                    }
+                } else {
+
+                    // if it was negative we count from the end of the array
+                    // might not exist, fx. -5th tuesday
+                    if (isset($dayHits[count($dayHits) + $offset])) {
+                        $byDayResults[] = $dayHits[count($dayHits) + $offset];
+                    }
+                }
+            } else {
+                // There was no counter (first, second, last wednesdays), so we
+                // just need to add the all to the list).
+                $byDayResults = array_merge($byDayResults, $dayHits);
+
+            }
+
+        }
+
+        $byMonthDayResults = [];
+        if ($this->byMonthDay) foreach ($this->byMonthDay as $monthDay) {
+
+            // Removing values that are out of range for this month
+            if ($monthDay > $startDate->format('t') ||
+                $monthDay < 0 - $startDate->format('t')) {
+                    continue;
+            }
+            if ($monthDay > 0) {
+                $byMonthDayResults[] = $monthDay;
+            } else {
+                // Negative values
+                $byMonthDayResults[] = $startDate->format('t') + 1 + $monthDay;
+            }
+        }
+
+        // If there was just byDay or just byMonthDay, they just specify our
+        // (almost) final list. If both were provided, then byDay limits the
+        // list.
+        if ($this->byMonthDay && $this->byDay) {
+            $result = array_intersect($byMonthDayResults, $byDayResults);
+        } elseif ($this->byMonthDay) {
+            $result = $byMonthDayResults;
+        } else {
+            $result = $byDayResults;
+        }
+        $result = array_unique($result);
+        sort($result, SORT_NUMERIC);
+
+        // The last thing that needs checking is the BYSETPOS. If it's set, it
+        // means only certain items in the set survive the filter.
+        if (!$this->bySetPos) {
+            return $result;
+        }
+
+        $filteredResult = [];
+        foreach ($this->bySetPos as $setPos) {
+
+            if ($setPos < 0) {
+                $setPos = count($result) + ($setPos + 1);
+            }
+            if (isset($result[$setPos - 1])) {
+                $filteredResult[] = $result[$setPos - 1];
+            }
+        }
+
+        sort($filteredResult, SORT_NUMERIC);
+        return $filteredResult;
+
+    }
+
+    /**
+     * Simple mapping from iCalendar day names to day numbers.
+     *
+     * @var array
+     */
+    protected $dayMap = [
+        'SU' => 0,
+        'MO' => 1,
+        'TU' => 2,
+        'WE' => 3,
+        'TH' => 4,
+        'FR' => 5,
+        'SA' => 6,
+    ];
+
+    protected function getHours() {
+
+        $recurrenceHours = [];
+        foreach ($this->byHour as $byHour) {
+            $recurrenceHours[] = $byHour;
+        }
+
+        return $recurrenceHours;
+    }
+
+    protected function getDays() {
+
+        $recurrenceDays = [];
+        foreach ($this->byDay as $byDay) {
+
+            // The day may be preceeded with a positive (+n) or
+            // negative (-n) integer. However, this does not make
+            // sense in 'weekly' so we ignore it here.
+            $recurrenceDays[] = $this->dayMap[substr($byDay, -2)];
+
+        }
+
+        return $recurrenceDays;
+    }
+
+    protected function getMonths() {
+
+        $recurrenceMonths = [];
+        foreach ($this->byMonth as $byMonth) {
+            $recurrenceMonths[] = $byMonth;
+        }
+
+        return $recurrenceMonths;
+    }
+}