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

6 files changed, 1016 insertions, 0 deletions

diff --git a/vendor/sabre/vobject/lib/Property/ICalendar/CalAddress.php b/vendor/sabre/vobject/lib/Property/ICalendar/CalAddress.php
new file mode 100644
index 000000000..a0c4a9b9a
--- /dev/null
+++ b/vendor/sabre/vobject/lib/Property/ICalendar/CalAddress.php
@@ -0,0 +1,61 @@
+<?php
+
+namespace Sabre\VObject\Property\ICalendar;
+
+use
+    Sabre\VObject\Property\Text;
+
+/**
+ * CalAddress property.
+ *
+ * This object encodes CAL-ADDRESS values, as defined in rfc5545
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class CalAddress extends Text {
+
+    /**
+     * In case this is a multi-value property. This string will be used as a
+     * delimiter.
+     *
+     * @var string|null
+     */
+    public $delimiter = null;
+
+    /**
+     * Returns the type of value.
+     *
+     * This corresponds to the VALUE= parameter. Every property also has a
+     * 'default' valueType.
+     *
+     * @return string
+     */
+    function getValueType() {
+
+        return 'CAL-ADDRESS';
+
+    }
+
+    /**
+     * This returns a normalized form of the value.
+     *
+     * This is primarily used right now to turn mixed-cased schemes in user
+     * uris to lower-case.
+     *
+     * Evolution in particular tends to encode mailto: as MAILTO:.
+     *
+     * @return string
+     */
+    function getNormalizedValue() {
+
+        $input = $this->getValue();
+        if (!strpos($input, ':')) {
+            return $input;
+        }
+        list($schema, $everythingElse) = explode(':', $input, 2);
+        return strtolower($schema) . ':' . $everythingElse;
+
+    }
+}
diff --git a/vendor/sabre/vobject/lib/Property/ICalendar/Date.php b/vendor/sabre/vobject/lib/Property/ICalendar/Date.php
new file mode 100644
index 000000000..378a0d60a
--- /dev/null
+++ b/vendor/sabre/vobject/lib/Property/ICalendar/Date.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace Sabre\VObject\Property\ICalendar;
+
+/**
+ * DateTime property.
+ *
+ * This object represents DATE values, as defined here:
+ *
+ * http://tools.ietf.org/html/rfc5545#section-3.3.5
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Date extends DateTime {
+
+}
diff --git a/vendor/sabre/vobject/lib/Property/ICalendar/DateTime.php b/vendor/sabre/vobject/lib/Property/ICalendar/DateTime.php
new file mode 100644
index 000000000..d580d4f68
--- /dev/null
+++ b/vendor/sabre/vobject/lib/Property/ICalendar/DateTime.php
@@ -0,0 +1,404 @@
+<?php
+
+namespace Sabre\VObject\Property\ICalendar;
+
+use DateTimeInterface;
+use DateTimeZone;
+use Sabre\VObject\DateTimeParser;
+use Sabre\VObject\InvalidDataException;
+use Sabre\VObject\Property;
+use Sabre\VObject\TimeZoneUtil;
+
+/**
+ * DateTime property.
+ *
+ * This object represents DATE-TIME values, as defined here:
+ *
+ * http://tools.ietf.org/html/rfc5545#section-3.3.4
+ *
+ * This particular object has a bit of hackish magic that it may also in some
+ * cases represent a DATE value. This is because it's a common usecase to be
+ * able to change a DATE-TIME into a DATE.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class DateTime extends Property {
+
+    /**
+     * In case this is a multi-value property. This string will be used as a
+     * delimiter.
+     *
+     * @var string|null
+     */
+    public $delimiter = ',';
+
+    /**
+     * Sets a multi-valued property.
+     *
+     * You may also specify DateTime objects here.
+     *
+     * @param array $parts
+     *
+     * @return void
+     */
+    function setParts(array $parts) {
+
+        if (isset($parts[0]) && $parts[0] instanceof DateTimeInterface) {
+            $this->setDateTimes($parts);
+        } else {
+            parent::setParts($parts);
+        }
+
+    }
+
+    /**
+     * Updates the current value.
+     *
+     * This may be either a single, or multiple strings in an array.
+     *
+     * Instead of strings, you may also use DateTime here.
+     *
+     * @param string|array|DateTimeInterface $value
+     *
+     * @return void
+     */
+    function setValue($value) {
+
+        if (is_array($value) && isset($value[0]) && $value[0] instanceof DateTimeInterface) {
+            $this->setDateTimes($value);
+        } elseif ($value instanceof DateTimeInterface) {
+            $this->setDateTimes([$value]);
+        } else {
+            parent::setValue($value);
+        }
+
+    }
+
+    /**
+     * Sets a raw value coming from a mimedir (iCalendar/vCard) file.
+     *
+     * This has been 'unfolded', so only 1 line will be passed. Unescaping is
+     * not yet done, but parameters are not included.
+     *
+     * @param string $val
+     *
+     * @return void
+     */
+    function setRawMimeDirValue($val) {
+
+        $this->setValue(explode($this->delimiter, $val));
+
+    }
+
+    /**
+     * Returns a raw mime-dir representation of the value.
+     *
+     * @return string
+     */
+    function getRawMimeDirValue() {
+
+        return implode($this->delimiter, $this->getParts());
+
+    }
+
+    /**
+     * Returns true if this is a DATE-TIME value, false if it's a DATE.
+     *
+     * @return bool
+     */
+    function hasTime() {
+
+        return strtoupper((string)$this['VALUE']) !== 'DATE';
+
+    }
+
+    /**
+     * Returns true if this is a floating DATE or DATE-TIME.
+     *
+     * Note that DATE is always floating.
+     */
+    function isFloating() {
+
+        return
+            !$this->hasTime() ||
+            (
+                !isset($this['TZID']) &&
+                strpos($this->getValue(), 'Z') === false
+            );
+
+    }
+
+    /**
+     * Returns a date-time value.
+     *
+     * Note that if this property contained more than 1 date-time, only the
+     * first will be returned. To get an array with multiple values, call
+     * getDateTimes.
+     *
+     * If no timezone information is known, because it's either an all-day
+     * property or floating time, we will use the DateTimeZone argument to
+     * figure out the exact date.
+     *
+     * @param DateTimeZone $timeZone
+     *
+     * @return DateTimeImmutable
+     */
+    function getDateTime(DateTimeZone $timeZone = null) {
+
+        $dt = $this->getDateTimes($timeZone);
+        if (!$dt) return;
+
+        return $dt[0];
+
+    }
+
+    /**
+     * Returns multiple date-time values.
+     *
+     * If no timezone information is known, because it's either an all-day
+     * property or floating time, we will use the DateTimeZone argument to
+     * figure out the exact date.
+     *
+     * @param DateTimeZone $timeZone
+     *
+     * @return DateTimeImmutable[]
+     * @return \DateTime[]
+     */
+    function getDateTimes(DateTimeZone $timeZone = null) {
+
+        // Does the property have a TZID?
+        $tzid = $this['TZID'];
+
+        if ($tzid) {
+            $timeZone = TimeZoneUtil::getTimeZone((string)$tzid, $this->root);
+        }
+
+        $dts = [];
+        foreach ($this->getParts() as $part) {
+            $dts[] = DateTimeParser::parse($part, $timeZone);
+        }
+        return $dts;
+
+    }
+
+    /**
+     * Sets the property as a DateTime object.
+     *
+     * @param DateTimeInterface $dt
+     * @param bool isFloating If set to true, timezones will be ignored.
+     *
+     * @return void
+     */
+    function setDateTime(DateTimeInterface $dt, $isFloating = false) {
+
+        $this->setDateTimes([$dt], $isFloating);
+
+    }
+
+    /**
+     * Sets the property as multiple date-time objects.
+     *
+     * The first value will be used as a reference for the timezones, and all
+     * the otehr values will be adjusted for that timezone
+     *
+     * @param DateTimeInterface[] $dt
+     * @param bool isFloating If set to true, timezones will be ignored.
+     *
+     * @return void
+     */
+    function setDateTimes(array $dt, $isFloating = false) {
+
+        $values = [];
+
+        if ($this->hasTime()) {
+
+            $tz = null;
+            $isUtc = false;
+
+            foreach ($dt as $d) {
+
+                if ($isFloating) {
+                    $values[] = $d->format('Ymd\\THis');
+                    continue;
+                }
+                if (is_null($tz)) {
+                    $tz = $d->getTimeZone();
+                    $isUtc = in_array($tz->getName(), ['UTC', 'GMT', 'Z', '+00:00']);
+                    if (!$isUtc) {
+                        $this->offsetSet('TZID', $tz->getName());
+                    }
+                } else {
+                    $d = $d->setTimeZone($tz);
+                }
+
+                if ($isUtc) {
+                    $values[] = $d->format('Ymd\\THis\\Z');
+                } else {
+                    $values[] = $d->format('Ymd\\THis');
+                }
+
+            }
+            if ($isUtc || $isFloating) {
+                $this->offsetUnset('TZID');
+            }
+
+        } else {
+
+            foreach ($dt as $d) {
+
+                $values[] = $d->format('Ymd');
+
+            }
+            $this->offsetUnset('TZID');
+
+        }
+
+        $this->value = $values;
+
+    }
+
+    /**
+     * Returns the type of value.
+     *
+     * This corresponds to the VALUE= parameter. Every property also has a
+     * 'default' valueType.
+     *
+     * @return string
+     */
+    function getValueType() {
+
+        return $this->hasTime() ? 'DATE-TIME' : 'DATE';
+
+    }
+
+    /**
+     * Returns the value, in the format it should be encoded for JSON.
+     *
+     * This method must always return an array.
+     *
+     * @return array
+     */
+    function getJsonValue() {
+
+        $dts = $this->getDateTimes();
+        $hasTime = $this->hasTime();
+        $isFloating = $this->isFloating();
+
+        $tz = $dts[0]->getTimeZone();
+        $isUtc = $isFloating ? false : in_array($tz->getName(), ['UTC', 'GMT', 'Z']);
+
+        return array_map(
+            function(DateTimeInterface $dt) use ($hasTime, $isUtc) {
+
+                if ($hasTime) {
+                    return $dt->format('Y-m-d\\TH:i:s') . ($isUtc ? 'Z' : '');
+                } else {
+                    return $dt->format('Y-m-d');
+                }
+
+            },
+            $dts
+        );
+
+    }
+
+    /**
+     * Sets the json value, as it would appear in a jCard or jCal object.
+     *
+     * The value must always be an array.
+     *
+     * @param array $value
+     *
+     * @return void
+     */
+    function setJsonValue(array $value) {
+
+        // dates and times in jCal have one difference to dates and times in
+        // iCalendar. In jCal date-parts are separated by dashes, and
+        // time-parts are separated by colons. It makes sense to just remove
+        // those.
+        $this->setValue(
+            array_map(
+                function($item) {
+
+                    return strtr($item, [':' => '', '-' => '']);
+
+                },
+                $value
+            )
+        );
+
+    }
+
+    /**
+     * We need to intercept offsetSet, because it may be used to alter the
+     * VALUE from DATE-TIME to DATE or vice-versa.
+     *
+     * @param string $name
+     * @param mixed $value
+     *
+     * @return void
+     */
+    function offsetSet($name, $value) {
+
+        parent::offsetSet($name, $value);
+        if (strtoupper($name) !== 'VALUE') {
+            return;
+        }
+
+        // This will ensure that dates are correctly encoded.
+        $this->setDateTimes($this->getDateTimes());
+
+    }
+
+    /**
+     * Validates the node for correctness.
+     *
+     * The following options are supported:
+     *   Node::REPAIR - May attempt to automatically repair the problem.
+     *
+     * This method returns an array with detected problems.
+     * Every element has the following properties:
+     *
+     *  * level - problem level.
+     *  * message - A human-readable string describing the issue.
+     *  * node - A reference to the problematic node.
+     *
+     * The level means:
+     *   1 - The issue was repaired (only happens if REPAIR was turned on)
+     *   2 - An inconsequential issue
+     *   3 - A severe issue.
+     *
+     * @param int $options
+     *
+     * @return array
+     */
+    function validate($options = 0) {
+
+        $messages = parent::validate($options);
+        $valueType = $this->getValueType();
+        $values = $this->getParts();
+        try {
+            foreach ($values as $value) {
+                switch ($valueType) {
+                    case 'DATE' :
+                        DateTimeParser::parseDate($value);
+                        break;
+                    case 'DATE-TIME' :
+                        DateTimeParser::parseDateTime($value);
+                        break;
+                }
+            }
+        } catch (InvalidDataException $e) {
+            $messages[] = [
+                'level'   => 3,
+                'message' => 'The supplied value (' . $value . ') is not a correct ' . $valueType,
+                'node'    => $this,
+            ];
+        }
+        return $messages;
+
+    }
+}
diff --git a/vendor/sabre/vobject/lib/Property/ICalendar/Duration.php b/vendor/sabre/vobject/lib/Property/ICalendar/Duration.php
new file mode 100644
index 000000000..66d366960
--- /dev/null
+++ b/vendor/sabre/vobject/lib/Property/ICalendar/Duration.php
@@ -0,0 +1,85 @@
+<?php
+
+namespace Sabre\VObject\Property\ICalendar;
+
+use Sabre\VObject\Property;
+use Sabre\VObject\DateTimeParser;
+
+/**
+ * Duration property.
+ *
+ * This object represents DURATION values, as defined here:
+ *
+ * http://tools.ietf.org/html/rfc5545#section-3.3.6
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Duration extends Property {
+
+    /**
+     * In case this is a multi-value property. This string will be used as a
+     * delimiter.
+     *
+     * @var string|null
+     */
+    public $delimiter = ',';
+
+    /**
+     * Sets a raw value coming from a mimedir (iCalendar/vCard) file.
+     *
+     * This has been 'unfolded', so only 1 line will be passed. Unescaping is
+     * not yet done, but parameters are not included.
+     *
+     * @param string $val
+     *
+     * @return void
+     */
+    function setRawMimeDirValue($val) {
+
+        $this->setValue(explode($this->delimiter, $val));
+
+    }
+
+    /**
+     * Returns a raw mime-dir representation of the value.
+     *
+     * @return string
+     */
+    function getRawMimeDirValue() {
+
+        return implode($this->delimiter, $this->getParts());
+
+    }
+
+    /**
+     * Returns the type of value.
+     *
+     * This corresponds to the VALUE= parameter. Every property also has a
+     * 'default' valueType.
+     *
+     * @return string
+     */
+    function getValueType() {
+
+        return 'DURATION';
+
+    }
+
+    /**
+     * Returns a DateInterval representation of the Duration property.
+     *
+     * If the property has more than one value, only the first is returned.
+     *
+     * @return \DateInterval
+     */
+    function getDateInterval() {
+
+        $parts = $this->getParts();
+        $value = $parts[0];
+        return DateTimeParser::parseDuration($value);
+
+    }
+
+}
diff --git a/vendor/sabre/vobject/lib/Property/ICalendar/Period.php b/vendor/sabre/vobject/lib/Property/ICalendar/Period.php
new file mode 100644
index 000000000..a4561d929
--- /dev/null
+++ b/vendor/sabre/vobject/lib/Property/ICalendar/Period.php
@@ -0,0 +1,155 @@
+<?php
+
+namespace Sabre\VObject\Property\ICalendar;
+
+use Sabre\VObject\Property;
+use Sabre\VObject\DateTimeParser;
+use Sabre\Xml;
+
+/**
+ * Period property.
+ *
+ * This object represents PERIOD values, as defined here:
+ *
+ * http://tools.ietf.org/html/rfc5545#section-3.8.2.6
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Period extends Property {
+
+    /**
+     * In case this is a multi-value property. This string will be used as a
+     * delimiter.
+     *
+     * @var string|null
+     */
+    public $delimiter = ',';
+
+    /**
+     * Sets a raw value coming from a mimedir (iCalendar/vCard) file.
+     *
+     * This has been 'unfolded', so only 1 line will be passed. Unescaping is
+     * not yet done, but parameters are not included.
+     *
+     * @param string $val
+     *
+     * @return void
+     */
+    function setRawMimeDirValue($val) {
+
+        $this->setValue(explode($this->delimiter, $val));
+
+    }
+
+    /**
+     * Returns a raw mime-dir representation of the value.
+     *
+     * @return string
+     */
+    function getRawMimeDirValue() {
+
+        return implode($this->delimiter, $this->getParts());
+
+    }
+
+    /**
+     * Returns the type of value.
+     *
+     * This corresponds to the VALUE= parameter. Every property also has a
+     * 'default' valueType.
+     *
+     * @return string
+     */
+    function getValueType() {
+
+        return 'PERIOD';
+
+    }
+
+    /**
+     * Sets the json value, as it would appear in a jCard or jCal object.
+     *
+     * The value must always be an array.
+     *
+     * @param array $value
+     *
+     * @return void
+     */
+    function setJsonValue(array $value) {
+
+        $value = array_map(
+            function($item) {
+
+                return strtr(implode('/', $item), [':' => '', '-' => '']);
+
+            },
+            $value
+        );
+        parent::setJsonValue($value);
+
+    }
+
+    /**
+     * Returns the value, in the format it should be encoded for json.
+     *
+     * This method must always return an array.
+     *
+     * @return array
+     */
+    function getJsonValue() {
+
+        $return = [];
+        foreach ($this->getParts() as $item) {
+
+            list($start, $end) = explode('/', $item, 2);
+
+            $start = DateTimeParser::parseDateTime($start);
+
+            // This is a duration value.
+            if ($end[0] === 'P') {
+                $return[] = [
+                    $start->format('Y-m-d\\TH:i:s'),
+                    $end
+                ];
+            } else {
+                $end = DateTimeParser::parseDateTime($end);
+                $return[] = [
+                    $start->format('Y-m-d\\TH:i:s'),
+                    $end->format('Y-m-d\\TH:i:s'),
+                ];
+            }
+
+        }
+
+        return $return;
+
+    }
+
+    /**
+     * This method serializes only the value of a property. This is used to
+     * create xCard or xCal documents.
+     *
+     * @param Xml\Writer $writer  XML writer.
+     *
+     * @return void
+     */
+    protected function xmlSerializeValue(Xml\Writer $writer) {
+
+        $writer->startElement(strtolower($this->getValueType()));
+        $value = $this->getJsonValue();
+        $writer->writeElement('start', $value[0][0]);
+
+        if ($value[0][1][0] === 'P') {
+            $writer->writeElement('duration', $value[0][1]);
+        }
+        else {
+            $writer->writeElement('end', $value[0][1]);
+        }
+
+        $writer->endElement();
+
+    }
+
+}
diff --git a/vendor/sabre/vobject/lib/Property/ICalendar/Recur.php b/vendor/sabre/vobject/lib/Property/ICalendar/Recur.php
new file mode 100644
index 000000000..a3c36dc64
--- /dev/null
+++ b/vendor/sabre/vobject/lib/Property/ICalendar/Recur.php
@@ -0,0 +1,293 @@
+<?php
+
+namespace Sabre\VObject\Property\ICalendar;
+
+use Sabre\VObject\Property;
+use Sabre\Xml;
+
+/**
+ * Recur property.
+ *
+ * This object represents RECUR properties.
+ * These values are just used for RRULE and the now deprecated EXRULE.
+ *
+ * The RRULE property may look something like this:
+ *
+ * RRULE:FREQ=MONTHLY;BYDAY=1,2,3;BYHOUR=5.
+ *
+ * This property exposes this as a key=>value array that is accessible using
+ * getParts, and may be set using setParts.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Recur extends Property {
+
+    /**
+     * Updates the current value.
+     *
+     * This may be either a single, or multiple strings in an array.
+     *
+     * @param string|array $value
+     *
+     * @return void
+     */
+    function setValue($value) {
+
+        // If we're getting the data from json, we'll be receiving an object
+        if ($value instanceof \StdClass) {
+            $value = (array)$value;
+        }
+
+        if (is_array($value)) {
+            $newVal = [];
+            foreach ($value as $k => $v) {
+
+                if (is_string($v)) {
+                    $v = strtoupper($v);
+
+                    // The value had multiple sub-values
+                    if (strpos($v, ',') !== false) {
+                        $v = explode(',', $v);
+                    }
+                    if (strcmp($k, 'until') === 0) {
+                        $v = strtr($v, [':' => '', '-' => '']);
+                    }
+                } elseif (is_array($v)) {
+                    $v = array_map('strtoupper', $v);
+                }
+
+                $newVal[strtoupper($k)] = $v;
+            }
+            $this->value = $newVal;
+        } elseif (is_string($value)) {
+            $this->value = self::stringToArray($value);
+        } else {
+            throw new \InvalidArgumentException('You must either pass a string, or a key=>value array');
+        }
+
+    }
+
+    /**
+     * Returns the current value.
+     *
+     * This method will always return a singular value. If this was a
+     * multi-value object, some decision will be made first on how to represent
+     * it as a string.
+     *
+     * To get the correct multi-value version, use getParts.
+     *
+     * @return string
+     */
+    function getValue() {
+
+        $out = [];
+        foreach ($this->value as $key => $value) {
+            $out[] = $key . '=' . (is_array($value) ? implode(',', $value) : $value);
+        }
+        return strtoupper(implode(';', $out));
+
+    }
+
+    /**
+     * Sets a multi-valued property.
+     *
+     * @param array $parts
+     * @return void
+     */
+    function setParts(array $parts) {
+
+        $this->setValue($parts);
+
+    }
+
+    /**
+     * Returns a multi-valued property.
+     *
+     * This method always returns an array, if there was only a single value,
+     * it will still be wrapped in an array.
+     *
+     * @return array
+     */
+    function getParts() {
+
+        return $this->value;
+
+    }
+
+    /**
+     * Sets a raw value coming from a mimedir (iCalendar/vCard) file.
+     *
+     * This has been 'unfolded', so only 1 line will be passed. Unescaping is
+     * not yet done, but parameters are not included.
+     *
+     * @param string $val
+     *
+     * @return void
+     */
+    function setRawMimeDirValue($val) {
+
+        $this->setValue($val);
+
+    }
+
+    /**
+     * Returns a raw mime-dir representation of the value.
+     *
+     * @return string
+     */
+    function getRawMimeDirValue() {
+
+        return $this->getValue();
+
+    }
+
+    /**
+     * Returns the type of value.
+     *
+     * This corresponds to the VALUE= parameter. Every property also has a
+     * 'default' valueType.
+     *
+     * @return string
+     */
+    function getValueType() {
+
+        return 'RECUR';
+
+    }
+
+    /**
+     * Returns the value, in the format it should be encoded for json.
+     *
+     * This method must always return an array.
+     *
+     * @return array
+     */
+    function getJsonValue() {
+
+        $values = [];
+        foreach ($this->getParts() as $k => $v) {
+            if (strcmp($k, 'UNTIL') === 0) {
+                $date = new DateTime($this->root, null, $v);
+                $values[strtolower($k)] = $date->getJsonValue()[0];
+            } elseif (strcmp($k, 'COUNT') === 0) {
+                $values[strtolower($k)] = intval($v);
+            } else {
+                $values[strtolower($k)] = $v;
+            }
+        }
+        return [$values];
+
+    }
+
+    /**
+     * This method serializes only the value of a property. This is used to
+     * create xCard or xCal documents.
+     *
+     * @param Xml\Writer $writer  XML writer.
+     *
+     * @return void
+     */
+    protected function xmlSerializeValue(Xml\Writer $writer) {
+
+        $valueType = strtolower($this->getValueType());
+
+        foreach ($this->getJsonValue() as $value) {
+            $writer->writeElement($valueType, $value);
+        }
+
+    }
+
+    /**
+     * Parses an RRULE value string, and turns it into a struct-ish array.
+     *
+     * @param string $value
+     *
+     * @return array
+     */
+    static function stringToArray($value) {
+
+        $value = strtoupper($value);
+        $newValue = [];
+        foreach (explode(';', $value) as $part) {
+
+            // Skipping empty parts.
+            if (empty($part)) {
+                continue;
+            }
+            list($partName, $partValue) = explode('=', $part);
+
+            // The value itself had multiple values..
+            if (strpos($partValue, ',') !== false) {
+                $partValue = explode(',', $partValue);
+            }
+            $newValue[$partName] = $partValue;
+
+        }
+
+        return $newValue;
+    }
+
+    /**
+     * Validates the node for correctness.
+     *
+     * The following options are supported:
+     *   Node::REPAIR - May attempt to automatically repair the problem.
+     *
+     * This method returns an array with detected problems.
+     * Every element has the following properties:
+     *
+     *  * level - problem level.
+     *  * message - A human-readable string describing the issue.
+     *  * node - A reference to the problematic node.
+     *
+     * The level means:
+     *   1 - The issue was repaired (only happens if REPAIR was turned on)
+     *   2 - An inconsequential issue
+     *   3 - A severe issue.
+     *
+     * @param int $options
+     *
+     * @return array
+     */
+    function validate($options = 0) {
+
+        $repair = ($options & self::REPAIR);
+
+        $warnings = parent::validate($options);
+        $values = $this->getParts();
+
+        foreach ($values as $key => $value) {
+
+            if (empty($value)) {
+                $warnings[] = [
+                    'level'   => $repair ? 3 : 1,
+                    'message' => 'Invalid value for ' . $key . ' in ' . $this->name,
+                    'node'    => $this
+                ];
+                if ($repair) {
+                    unset($values[$key]);
+                }
+            }
+
+        }
+        if (!isset($values['FREQ'])) {
+            $warnings[] = [
+                'level'   => $repair ? 3 : 1,
+                'message' => 'FREQ is required in ' . $this->name,
+                'node'    => $this
+            ];
+            if ($repair) {
+                $this->parent->remove($this);
+            }
+        }
+        if ($repair) {
+            $this->setValue($values);
+        }
+
+        return $warnings;
+
+    }
+
+}