[locationinfo] His: Switch from SOAP to iCal

iCal downloads are much faster in more revent HisInOne versions, while
the SOAP API will make cobbling together a time table for a specific
room even more complicated in the next release (2020.12).
Switch to iCal for now and see how it goes.

TODO: Create a generic iCal backend module based on this.

7 files changed, 2373 insertions, 304 deletions

diff --git a/modules-available/locationinfo/inc/coursebackend.inc.php b/modules-available/locationinfo/inc/coursebackend.inc.php
index a66d35a3..fc03671c 100644
--- a/modules-available/locationinfo/inc/coursebackend.inc.php
+++ b/modules-available/locationinfo/inc/coursebackend.inc.php
@@ -149,13 +149,25 @@ abstract class CourseBackend
 	 */
 	protected abstract function fetchSchedulesInternal($roomId);
 
+	/**
+	 * In case you want to sanitize or otherwise mangle a property for your backend,
+	 * override this.
+	 * @param string $prop
+	 * @param $value
+	 * @return mixed
+	 */
+	public function mangleProperty($prop, $value)
+	{
+		return $value;
+	}
+
 	private static function fixTime(&$start, &$end)
 	{
-		if (!preg_match('/^\d+-\d+-\d+T\d+:\d+:\d+$/', $start) || !preg_match('/^\d+-\d+-\d+T\d+:\d+:\d+$/', $end))
+		if (!preg_match('/^(\d{2}|\d{4})-?\d{2}-?\d{2}-?T\d{1,2}:?\d{2}:?(\d{2})?$/', $start))
 			return false;
 		$start = strtotime($start);
 		$end = strtotime($end);
-		if ($start >= $end)
+		if ($start === false || $end === false || $start >= $end)
 			return false;
 		$start = date('Y-m-d\TH:i:s', $start);
 		$end = date('Y-m-d\TH:i:s', $end);
diff --git a/modules-available/locationinfo/inc/coursebackend/coursebackend_hisinone.inc.php b/modules-available/locationinfo/inc/coursebackend/coursebackend_hisinone.inc.php
index 4664a011..ee152684 100644
--- a/modules-available/locationinfo/inc/coursebackend/coursebackend_hisinone.inc.php
+++ b/modules-available/locationinfo/inc/coursebackend/coursebackend_hisinone.inc.php
@@ -2,9 +2,6 @@
 
 class CourseBackend_HisInOne extends CourseBackend
 {
-	private $username = '';
-	private $password = '';
-	private $open = true;
 	private $location;
 	private $verifyHostname = true;
 	private $verifyCert = true;
@@ -16,32 +13,12 @@ class CourseBackend_HisInOne extends CourseBackend
 
 	public function setCredentialsInternal($data)
 	{
-		if (!$data['open']) {
-			// If not using OpenCourseService, require credentials
-			foreach (['username', 'password'] as $field) {
-				if (empty($data[$field])) {
-					$this->addError('setCredentials: Missing field ' . $field, true);
-					return false;
-				}
-			}
-		}
 		if (empty($data['baseUrl'])) {
 			$this->addError("No url is given", true);
 			return false;
 		}
 
-		$this->username = $data['username'];
-		if (!empty($data['role'])) {
-			$this->username .= "\t" . $data['role'];
-		}
-		$this->password = $data['password'];
-		$this->open = $data['open'] !== 'CourseService';
-		$url = preg_replace('#(/+qisserver(/+services\d+(/+OpenCourseService)?)?)?\W*$#i', '', $data['baseUrl']);
-		if ($this->open) {
-			$this->location = $url . "/qisserver/services2/OpenCourseService";
-		} else {
-			$this->location = $url . "/qisserver/services2/CourseService";
-		}
+		$this->location = $this->mangleProperty('baseUrl', $data['baseUrl']);
 		$this->verifyHostname = $data['verifyHostname'];
 		$this->verifyCert = $data['verifyCert'];
 
@@ -52,156 +29,80 @@ class CourseBackend_HisInOne extends CourseBackend
 	{
 		return [
 			new BackendProperty('baseUrl', 'string'),
-			new BackendProperty('username', 'string'),
-			new BackendProperty('role', 'string'),
-			new BackendProperty('password', 'password'),
-			new BackendProperty('open', ['OpenCourseService', 'CourseService'], 'OpenCourseService'),
 			new BackendProperty('verifyCert', 'bool', true),
 			new BackendProperty('verifyHostname', 'bool', true)
 		];
 	}
 
-	public function checkConnection()
+	public function mangleProperty($prop, $value)
 	{
-		if (empty($this->location)) {
-			$this->addError("Credentials are not set", true);
-			return false;
+		if ($prop === 'baseUrl') {
+			// Update form SOAP to iCal url
+			if (preg_match(',^(http.*?)/qisserver,', $value, $out)) {
+				$value = $out[1] . '/qisserver/pages/cm/exa/timetable/roomScheduleCalendarExport.faces?roomId=';
+			} elseif (preg_match(',(.*[/=])\d*$', $value, $out)) {
+				$value = $out[1];
+			} elseif (substr_count($value, '/') <= 3) {
+				if (substr($value, -1) !== '/') {
+					$value .= '/';
+				}
+				$value .= 'qisserver/pages/cm/exa/timetable/roomScheduleCalendarExport.faces?roomId=';
+			}
 		}
-		return $this->findUnit(123456789, date('Y-m-d'), true) !== false;
+		return $value;
 	}
 
-	/**
-	 * @param int $roomId his in one room id to get
-	 * @param bool $connectionCheckOnly true will only check if no soapError is returned, return value will be empty
-	 * @return array|bool if successful an array with the event ids that take place in the room
-	 */
-	public function findUnit($roomId, $day, $connectionCheckOnly = false)
+	public function checkConnection()
 	{
-		$doc = new DOMDocument('1.0', 'utf-8');
-		$doc->formatOutput = true;
-		$envelope = $doc->createElementNS('http://schemas.xmlsoap.org/soap/envelope/', 'SOAP-ENV:Envelope');
-		$doc->appendChild($envelope);
-		if ($this->open) {
-			$envelope->setAttributeNS('http://www.w3.org/2000/xmlns/', 'xmlns:ns1', 'http://www.his.de/ws/OpenCourseService');
-		} else {
-			$envelope->setAttributeNS('http://www.w3.org/2000/xmlns/', 'xmlns:ns1', 'http://www.his.de/ws/CourseService');
-		}
-		$header = $this->getHeader($doc);
-		$envelope->appendChild($header);
-		//Body of the request
-		$body = $doc->createElement('SOAP-ENV:Body');
-		$envelope->appendChild($body);
-		$findUnit = $doc->createElement('ns1:findUnit');
-		$body->appendChild($findUnit);
-		$findUnit->appendChild($doc->createElement('ns1:individualDatesExecutionDate', $day));
-		$findUnit->appendChild($doc->createElement('ns1:roomId', $roomId));
-
-		$soap_request = $doc->saveXML();
-		$response1 = $this->postToServer($soap_request, "findUnit");
-		if ($response1 === false) {
-			$this->addError('Could not fetch room ' . $roomId, true);
-			return false;
-		}
-		$response2 = $this->xmlStringToArray($response1, $err);
-		if (!is_array($response2)) {
-			$this->addError("Parsing room $roomId: $err", false);
-			return false;
-		}
-		if (!isset($response2['soapenvBody'])) {
-			$this->addError('Backend reply is missing element soapenvBody', true);
-			return false;
-		}
-		if (isset($response2['soapenvBody']['soapenvFault'])) {
-			$this->addError('SOAP-Fault (' . $response2['soapenvBody']['soapenvFault']['faultcode'] . ") " . $response2['soapenvBody']['soapenvFault']['faultstring'], true);
-			return false;
-		}
-		// We only need to check if the connection is working (URL ok, credentials ok, ..) so bail out early
-		if ($connectionCheckOnly) {
-			return array();
-		}
-		if ($this->open) {
-			$path = '/soapenvBody/hisfindUnitResponse/hisunits';
-			$subpath = '/hisunit/hisid';
-		} else {
-			$path = '/soapenvBody/hisfindUnitResponse/hisunitIds';
-			$subpath = '/hisid';
-		}
-		$idSubDoc = $this->getArrayPath($response2, $path);
-		if ($idSubDoc === false) {
-			$this->addError('Cannot find ' . $path, false);
-			//@file_put_contents('/tmp/findUnit-1.' . $roomId . '.' . microtime(true), print_r($response2, true));
+		if (empty($this->location)) {
+			$this->addError("Credentials are not set", true);
 			return false;
 		}
-		if (empty($idSubDoc))
-			return $idSubDoc;
-		$idList = $this->getArrayPath($idSubDoc, $subpath);
-		if ($idList === false) {
-			$this->addError('Cannot find ' . $subpath . ' after ' . $path, false);
-			@file_put_contents('/tmp/bwlp-findUnit-2.' . $roomId . '.' . microtime(true), print_r($idSubDoc, true));
+		// Unfortunately HisInOne returns an internal server error if you pass an invalid roomId.
+		// So we just try a bunch and see if anything works. Even if this fails, using
+		// the backend should work, given the URL is actually correct.
+		foreach ([60, 100, 5, 10, 50, 110, 200, 210, 250, 300, 333, 500, 1000, 2000] as $roomId) {
+			if ($this->downloadIcal($roomId) !== null)
+				return true;
 		}
-		return $idList;
+		return false;
 	}
 
 	/**
-	 * @param $doc DOMDocument
-	 * @return DOMElement
+	 * @param int $roomId room id
+	 * @return ICalEvent[]|null all events for this room in the range -7 days to +7 days, or NULL on error
 	 */
-	private function getHeader($doc)
+	private function downloadIcal($roomId)
 	{
-		$header = $doc->createElement('SOAP-ENV:Header');
-		$security = $doc->createElementNS('http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd', 'ns2:Security');
-		$mustunderstand = $doc->createAttribute('SOAP-ENV:mustUnderstand');
-		$mustunderstand->value = 1;
-		$security->appendChild($mustunderstand);
-		$header->appendChild($security);
-		$token = $doc->createElement('ns2:UsernameToken');
-		$security->appendChild($token);
-		$user = $doc->createElement('ns2:Username', $this->username);
-		$token->appendChild($user);
-		$pass = $doc->createElement('ns2:Password', $this->password);
-		$type = $doc->createAttribute('Type');
-		$type->value = 'http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-username-token-profile-1.0#PasswordText';
-		$pass->appendChild($type);
-		$token->appendChild($pass);
-		return $header;
-	}
-
-	/**
-	 * @param $request string with xml SOAP request
-	 * @param $action string with the name of the SOAP action
-	 * @return bool|string if successful the answer xml from the SOAP server
-	 */
-	private function postToServer($request, $action)
-	{
-		$header = array(
-			'Content-type: text/xml;charset="utf-8"',
-			'SOAPAction: "' . $action . '"',
-		);
-
 		if ($this->curlHandle === false) {
 			$this->curlHandle = curl_init();
 		}
 
+		$ical = new ICalParser(['filterDaysBefore' => 7, 'filterDaysAfter' => 7]);
 		$options = array(
-			CURLOPT_RETURNTRANSFER => true,
+			CURLOPT_WRITEFUNCTION => function ($ch, $data) use ($ical) {
+				$ical->feedData($data);
+				return strlen($data);
+			},
 			CURLOPT_FOLLOWLOCATION => true,
 			CURLOPT_SSL_VERIFYHOST => $this->verifyHostname ? 2 : 0,
 			CURLOPT_SSL_VERIFYPEER => $this->verifyCert ? 1 : 0,
-			CURLOPT_URL => $this->location,
-			CURLOPT_POSTFIELDS => $request,
-			CURLOPT_HTTPHEADER => $header,
-			CURLOPT_TIMEOUT => 15,
-			CURLOPT_CONNECTTIMEOUT => 3,
+			CURLOPT_URL => $this->location . $roomId,
+			CURLOPT_TIMEOUT => 60,
+			CURLOPT_CONNECTTIMEOUT => 4,
 		);
 
 		curl_setopt_array($this->curlHandle, $options);
 
-		$output = curl_exec($this->curlHandle);
-
-		if ($output === false) {
+		if (!curl_exec($this->curlHandle)) {
 			$this->addError('Curl error: ' . curl_error($this->curlHandle), false);
 		}
-		return $output;
+		$ical->finish();
+		if (!$ical->isValid()) {
+			error_log('Did not find a VCALENDAR in returned data');
+			return null;
+		}
+		return $ical->events();
 	}
 
 	public function getCacheTime()
@@ -209,7 +110,6 @@ class CourseBackend_HisInOne extends CourseBackend
 		return 30 * 60;
 	}
 
-
 	public function getRefreshTime()
 	{
 		return 60 * 60;
@@ -226,159 +126,39 @@ class CourseBackend_HisInOne extends CourseBackend
 		if (empty($requestedRoomIds)) {
 			return array();
 		}
-		$currentWeek = $this->getCurrentWeekDates();
 		$tTables = [];
-		//get all eventIDs in a given room
-		$eventIds = [];
 		foreach ($requestedRoomIds as $roomId) {
-			$ok = false;
-			foreach ($currentWeek as $day) {
-				$roomEventIds = $this->findUnit($roomId, $day, false);
-				if ($roomEventIds === false)
-					continue;
-				$ok = true;
-				$eventIds = array_merge($eventIds, $roomEventIds);
-			}
-			if ($ok) {
-				$tTables[$roomId] = [];
-			}
-		}
-		$eventIds = array_unique($eventIds);
-		if (empty($eventIds)) {
-			return $tTables;
-		}
-		$eventDetails = [];
-		//get all information on each event
-		foreach ($eventIds as $eventId) {
-			$event = $this->readUnit(intval($eventId));
-			if ($event === false)
-				continue;
-			$eventDetails = array_merge($eventDetails, $event);
-		}
-		$name = false;
-		$now = time();
-		foreach ($eventDetails as $event) {
-			foreach (array('/hisdefaulttext',
-							'/hisshorttext',
-							'/hisshortcomment') as $path) {
-				$name = $this->getArrayPath($event, $path);
-				if (!empty($name) && !empty($name[0]))
-					break;
-				$name = false;
-			}
-			if ($name === false) {
-				$name = ['???'];
-			}
-			$planElements = $this->getArrayPath($event, '/hisplanelements/hisplanelement');
-			if ($planElements === false) {
-				$this->addError('Cannot find ./hisplanelements/hisplanelement', false);
-				//error_log('Cannot find ./hisplanelements/hisplanelement');
-				//error_log(print_r($event, true));
+			$data = $this->downloadIcal($roomId);
+			if ($data === null) {
+				$this->addError("Downloading ical for $roomId failed", false);
 				continue;
 			}
-			foreach ($planElements as $planElement) {
-				if (empty($planElement['hisplannedDates']))
-					continue;
-				// Do not use -- is set improperly for some courses :-(
-				/*
-				$checkDate = $this->getArrayPath($planElement, '/hisplannedDates/hisplannedDate/hisenddate');
-				if (!empty($checkDate) && strtotime($checkDate[0]) + 86400 < $now)
-					continue; // Course ended
-				$checkDate = $this->getArrayPath($planElement, '/hisplannedDates/hisplannedDate/hisstartdate');
-				if (!empty($checkDate) && strtotime($checkDate[0]) - 86400 > $now)
-					continue; // Course didn't start yet
-				*/
-				$cancelled = $this->getArrayPath($planElement, '/hiscancelled');
-				$cancelled = $cancelled !== false && is_array($cancelled) && ($cancelled[0] > 0 || strtolower($cancelled[0]) === 'true');
-				$unitPlannedDates = $this->getArrayPath($planElement,
-					'/hisplannedDates/hisplannedDate/hisindividualDates/hisindividualDate');
-				if ($unitPlannedDates === false) {
-					$this->addError('Cannot find ./hisplannedDates/hisplannedDate/hisindividualDates/hisindividualDate', false);
-					//error_log('Cannot find ./hisplannedDates/hisplannedDate/hisindividualDates/hisindividualDate');
-					//error_log(print_r($planElement, true));
-					continue;
-				}
-				$localName = $this->getArrayPath($planElement, '/hisdefaulttext');
-				if ($localName === false || empty($localName[0])) {
-					$localName = $name;
-				}
-				foreach ($unitPlannedDates as $plannedDate) {
-					$eventRoomId = $this->getArrayPath($plannedDate, '/hisroomId')[0];
-					$eventDate = $this->getArrayPath($plannedDate, '/hisexecutiondate')[0];
-					if (in_array($eventRoomId, $requestedRoomIds) && in_array($eventDate, $currentWeek)) {
-						$startTime = $this->getArrayPath($plannedDate, '/hisstarttime')[0];
-						$endTime = $this->getArrayPath($plannedDate, '/hisendtime')[0];
-						$tTables[$eventRoomId][] = array(
-							'title' => $localName[0],
-							'start' => $eventDate . "T" . $startTime,
-							'end' => $eventDate . "T" . $endTime,
-							'cancelled' => $cancelled,
-						);
-					}
-				}
+			foreach ($data as $event) {
+				$tTables[$roomId][] = array(
+					'title' => $this->toTitle($event),
+					'start' => $event->dtstart,
+					'end' => $event->dtend,
+					'cancelled' => false, // ??? How
+				);
 			}
 		}
 		return $tTables;
 	}
 
-
 	/**
-	 * @param $unit int ID of the subject in HisInOne database
-	 * @return bool|array false if there was an error otherwise an array with the information about the subject
+	 * Get a usable title from either SUMMARY or DESCRIPTION
+	 * @param ICalEvent $event
 	 */
-	public function readUnit($unit)
+	private function toTitle($event)
 	{
-		$doc = new DOMDocument('1.0', 'utf-8');
-		$doc->formatOutput = true;
-		$envelope = $doc->createElementNS('http://schemas.xmlsoap.org/soap/envelope/', 'SOAP-ENV:Envelope');
-		$doc->appendChild($envelope);
-		if ($this->open) {
-			$envelope->setAttributeNS('http://www.w3.org/2000/xmlns/', 'xmlns:ns1', 'http://www.his.de/ws/OpenCourseService');
-		} else {
-			$envelope->setAttributeNS('http://www.w3.org/2000/xmlns/', 'xmlns:ns1', 'http://www.his.de/ws/CourseService');
-		}
-		$header = $this->getHeader($doc);
-		$envelope->appendChild($header);
-		//body of the request
-		$body = $doc->createElement('SOAP-ENV:Body');
-		$envelope->appendChild($body);
-		$readUnit = $doc->createElement('ns1:readUnit');
-		$body->appendChild($readUnit);
-		$readUnit->appendChild($doc->createElement('ns1:unitId', $unit));
-
-		$soap_request = $doc->saveXML();
-		$response1 = $this->postToServer($soap_request, "readUnit");
-		if ($response1 === false) {
-			return false;
-		}
-		$response2 = $this->xmlStringToArray($response1, $err);
-		if ($response2 === false) {
-			$this->addError("Cannot parse unit $unit as XML: $err", false);
-			return false;
-		}
-		if (!isset($response2['soapenvBody'])) {
-			$this->addError('Backend reply is missing element soapenvBody', true);
-			return false;
-		}
-		if (isset($response2['soapenvBody']['soapenvFault'])) {
-			$this->addError('SOAP-Fault (' . $response2['soapenvBody']['soapenvFault']['faultcode'] . ") " . $response2['soapenvBody']['soapenvFault']['faultstring'], true);
-			return false;
+		$title = $event->summary;
+		if (empty($title)) {
+			$title = $event->description;
 		}
-		return $this->getArrayPath($response2, '/soapenvBody/hisreadUnitResponse/hisunit');
-	}
-
-	/**
-	 * @return array with days of the current week in datetime format
-	 */
-	private function getCurrentWeekDates()
-	{
-		$returnValue = array();
-		$date = date('Y-m-d', strtotime('last Monday'));
-		for ($i = 0; $i < 14; $i++) {
-			$returnValue[] = $date;
-			$date = date('Y-m-d', strtotime($date.' +1 day'));
+		if (empty($title)) {
+			$title = 'Unknown';
 		}
-		return $returnValue;
+		return preg_replace([',(\s*<br\s*/?>\s*|\r|\n|\\\r|\\\n)+,', '/\\\\([,;:])/'], ["\n", '$1'], $title);
 	}
 
 	public function __destruct()
diff --git a/modules-available/locationinfo/inc/icalevent.inc.php b/modules-available/locationinfo/inc/icalevent.inc.php
new file mode 100644
index 00000000..1fb586ee
--- /dev/null
+++ b/modules-available/locationinfo/inc/icalevent.inc.php
@@ -0,0 +1,200 @@
+<?php
+
+class ICalEvent
+{
+    // phpcs:disable Generic.Arrays.DisallowLongArraySyntax
+
+    const HTML_TEMPLATE = '<p>%s: %s</p>';
+
+    /**
+     * https://www.kanzaki.com/docs/ical/summary.html
+     *
+     * @var $summary
+     */
+    public $summary;
+
+    /**
+     * https://www.kanzaki.com/docs/ical/dtstart.html
+     *
+     * @var $dtstart
+     */
+    public $dtstart;
+
+    /**
+     * https://www.kanzaki.com/docs/ical/dtend.html
+     *
+     * @var $dtend
+     */
+    public $dtend;
+
+    /**
+     * https://www.kanzaki.com/docs/ical/duration.html
+     *
+     * @var $duration
+     */
+    public $duration;
+
+    /**
+     * https://www.kanzaki.com/docs/ical/dtstamp.html
+     *
+     * @var $dtstamp
+     */
+    public $dtstamp;
+
+    /**
+     * https://www.kanzaki.com/docs/ical/uid.html
+     *
+     * @var $uid
+     */
+    public $uid;
+
+    /**
+     * https://www.kanzaki.com/docs/ical/created.html
+     *
+     * @var $created
+     */
+    public $created;
+
+    /**
+     * https://www.kanzaki.com/docs/ical/lastModified.html
+     *
+     * @var $lastmodified
+     */
+    public $lastmodified;
+
+    /**
+     * https://www.kanzaki.com/docs/ical/description.html
+     *
+     * @var $description
+     */
+    public $description;
+
+    /**
+     * https://www.kanzaki.com/docs/ical/location.html
+     *
+     * @var $location
+     */
+    public $location;
+
+    /**
+     * https://www.kanzaki.com/docs/ical/sequence.html
+     *
+     * @var $sequence
+     */
+    public $sequence;
+
+    /**
+     * https://www.kanzaki.com/docs/ical/status.html
+     *
+     * @var $status
+     */
+    public $status;
+
+    /**
+     * https://www.kanzaki.com/docs/ical/transp.html
+     *
+     * @var $transp
+     */
+    public $transp;
+
+    /**
+     * https://www.kanzaki.com/docs/ical/organizer.html
+     *
+     * @var $organizer
+     */
+    public $organizer;
+
+    /**
+     * https://www.kanzaki.com/docs/ical/attendee.html
+     *
+     * @var $attendee
+     */
+    public $attendee;
+
+    /**
+     * Creates the Event object
+     *
+     * @param  array $data
+     * @return void
+     */
+    public function __construct(array $data = array())
+    {
+        foreach ($data as $key => $value) {
+            $variable = self::snakeCase($key);
+            $this->{$variable} = self::prepareData($value);
+        }
+    }
+
+    /**
+     * Prepares the data for output
+     *
+     * @param  mixed $value
+     * @return mixed
+     */
+    protected function prepareData($value)
+    {
+        if (is_string($value)) {
+            return stripslashes(trim(str_replace('\n', "\n", $value)));
+        } elseif (is_array($value)) {
+            return array_map('self::prepareData', $value);
+        }
+
+        return $value;
+    }
+
+    /**
+     * Returns Event data excluding anything blank
+     * within an HTML template
+     *
+     * @param  string $html HTML template to use
+     * @return string
+     */
+    public function printData($html = self::HTML_TEMPLATE)
+    {
+        $data = array(
+            'SUMMARY'       => $this->summary,
+            'DTSTART'       => $this->dtstart,
+            'DTEND'         => $this->dtend,
+            'DURATION'      => $this->duration,
+            'DTSTAMP'       => $this->dtstamp,
+            'UID'           => $this->uid,
+            'CREATED'       => $this->created,
+            'LAST-MODIFIED' => $this->lastmodified,
+            'DESCRIPTION'   => $this->description,
+            'LOCATION'      => $this->location,
+            'SEQUENCE'      => $this->sequence,
+            'STATUS'        => $this->status,
+            'TRANSP'        => $this->transp,
+            'ORGANISER'     => $this->organizer,
+            'ATTENDEE(S)'   => $this->attendee,
+        );
+
+        // Remove any blank values
+        $data = array_filter($data);
+
+        $output = '';
+
+        foreach ($data as $key => $value) {
+            $output .= sprintf($html, $key, $value);
+        }
+
+        return $output;
+    }
+
+    /**
+     * Converts the given input to snake_case
+     *
+     * @param  string $input
+     * @param  string $glue
+     * @param  string $separator
+     * @return string
+     */
+    protected static function snakeCase($input, $glue = '_', $separator = '-')
+    {
+        $input = preg_split('/(?<=[a-z])(?=[A-Z])/x', $input);
+        $input = implode($glue, $input);
+        $input = str_replace($separator, $glue, $input);
+
+        return strtolower($input);
+    }
+}
diff --git a/modules-available/locationinfo/inc/icalparser.inc.php b/modules-available/locationinfo/inc/icalparser.inc.php
new file mode 100644
index 00000000..6d41404c
--- /dev/null
+++ b/modules-available/locationinfo/inc/icalparser.inc.php
@@ -0,0 +1,2092 @@
+<?php
+
+/*
+ * Modified for slx-admin to support streaming, some functions removed that are not needed,
+ * Carbon removed, Honor window size when calculating recurring events, ...
+ */
+
+/**
+ * This PHP class will read an ICS (`.ics`, `.ical`, `.ifb`) file, parse it and return an
+ * array of its contents.
+ *
+ * PHP 5 (≥ 5.3.9)
+ *
+ * @author  Jonathan Goode <https://github.com/u01jmg3>
+ * @license https://opensource.org/licenses/mit-license.php MIT License
+ * @version 2.1.20
+ */
+class ICalParser
+{
+	// phpcs:disable Generic.Arrays.DisallowLongArraySyntax
+
+	const DATE_TIME_FORMAT = 'Ymd\THis';
+	const ICAL_DATE_TIME_TEMPLATE = 'TZID=%s:';
+	const ISO_8601_WEEK_START = 'MO';
+	const RECURRENCE_EVENT = 'Generated recurrence event';
+	const TIME_FORMAT = 'His';
+	const TIME_ZONE_UTC = 'UTC';
+	const UNIX_FORMAT = 'U';
+
+	/**
+	 * Tracks the number of alarms in the current iCal feed
+	 *
+	 * @var integer
+	 */
+	public $alarmCount = 0;
+
+	/**
+	 * Tracks the number of events in the current iCal feed
+	 *
+	 * @var integer
+	 */
+	public $eventCount = 0;
+
+	/**
+	 * Tracks the free/busy count in the current iCal feed
+	 *
+	 * @var integer
+	 */
+	public $freeBusyCount = 0;
+
+	/**
+	 * Tracks the number of todos in the current iCal feed
+	 *
+	 * @var integer
+	 */
+	public $todoCount = 0;
+
+	/**
+	 * The value in years to use for indefinite, recurring events
+	 *
+	 * @var integer
+	 */
+	public $defaultSpan = 2;
+
+	/**
+	 * Enables customisation of the default time zone
+	 *
+	 * @var string
+	 */
+	public $defaultTimeZone;
+
+	/**
+	 * The two letter representation of the first day of the week
+	 *
+	 * @var string
+	 */
+	public $defaultWeekStart = self::ISO_8601_WEEK_START;
+
+	/**
+	 * Toggles whether to skip the parsing of recurrence rules
+	 *
+	 * @var boolean
+	 */
+	public $skipRecurrence = false;
+
+	/**
+	 * With this being non-null the parser will ignore all events more than roughly this many days after now.
+	 *
+	 * @var integer
+	 */
+	public $filterDaysBefore;
+
+	/**
+	 * With this being non-null the parser will ignore all events more than roughly this many days before now.
+	 *
+	 * @var integer
+	 */
+	public $filterDaysAfter;
+
+	/**
+	 * @var string Which object type we're currently handling while parsing.
+	 */
+	private $parseStateComponent = '';
+
+	/**
+	 * @var string Current line being read (in case of continuation).
+	 */
+	private $currentLineBuffer = '';
+
+	/**
+	 * @var string Chunk of data currently being handled - might stop mid-line.
+	 */
+	private $feedBuffer = '';
+
+	/**
+	 * @var bool whether we ever saw a BEGIN:VCALENDAR in the data
+	 */
+	private $hasSeenStart = false;
+
+	/**
+	 * The parsed calendar
+	 *
+	 * @var array
+	 */
+	public $cal = array();
+
+	/**
+	 * Tracks the VFREEBUSY component
+	 *
+	 * @var integer
+	 */
+	protected $freeBusyIndex = 0;
+
+	/**
+	 * Variable to track the previous keyword
+	 *
+	 * @var string
+	 */
+	protected $lastKeyword;
+
+	/**
+	 * Cache valid IANA time zone IDs to avoid unnecessary lookups
+	 *
+	 * @var array
+	 */
+	protected $validIanaTimeZones = array();
+
+	/**
+	 * Event recurrence instances that have been altered
+	 *
+	 * @var array
+	 */
+	protected $alteredRecurrenceInstances = array();
+
+	/**
+	 * An associative array containing weekday conversion data
+	 *
+	 * The order of the days in the array follow the ISO-8601 specification of a week.
+	 *
+	 * @var array
+	 */
+	protected $weekdays = array(
+		'MO' => 'monday',
+		'TU' => 'tuesday',
+		'WE' => 'wednesday',
+		'TH' => 'thursday',
+		'FR' => 'friday',
+		'SA' => 'saturday',
+		'SU' => 'sunday',
+	);
+
+	/**
+	 * An associative array containing frequency conversion terms
+	 *
+	 * @var array
+	 */
+	protected $frequencyConversion = array(
+		'DAILY' => 'day',
+		'WEEKLY' => 'week',
+		'MONTHLY' => 'month',
+		'YEARLY' => 'year',
+	);
+
+	/**
+	 * Define which variables can be configured
+	 *
+	 * @var array
+	 */
+	private static $configurableOptions = array(
+		'defaultSpan',
+		'defaultTimeZone',
+		'defaultWeekStart',
+		'filterDaysAfter',
+		'filterDaysBefore',
+		'skipRecurrence',
+	);
+
+	/**
+	 * CLDR time zones mapped to IANA time zones.
+	 *
+	 * @var array
+	 */
+	private static $cldrTimeZonesMap = array(
+		'(UTC-12:00) International Date Line West' => 'Etc/GMT+12',
+		'(UTC-11:00) Coordinated Universal Time-11' => 'Etc/GMT+11',
+		'(UTC-10:00) Hawaii' => 'Pacific/Honolulu',
+		'(UTC-09:00) Alaska' => 'America/Anchorage',
+		'(UTC-08:00) Pacific Time (US & Canada)' => 'America/Los_Angeles',
+		'(UTC-07:00) Arizona' => 'America/Phoenix',
+		'(UTC-07:00) Chihuahua, La Paz, Mazatlan' => 'America/Chihuahua',
+		'(UTC-07:00) Mountain Time (US & Canada)' => 'America/Denver',
+		'(UTC-06:00) Central America' => 'America/Guatemala',
+		'(UTC-06:00) Central Time (US & Canada)' => 'America/Chicago',
+		'(UTC-06:00) Guadalajara, Mexico City, Monterrey' => 'America/Mexico_City',
+		'(UTC-06:00) Saskatchewan' => 'America/Regina',
+		'(UTC-05:00) Bogota, Lima, Quito, Rio Branco' => 'America/Bogota',
+		'(UTC-05:00) Chetumal' => 'America/Cancun',
+		'(UTC-05:00) Eastern Time (US & Canada)' => 'America/New_York',
+		'(UTC-05:00) Indiana (East)' => 'America/Indianapolis',
+		'(UTC-04:00) Asuncion' => 'America/Asuncion',
+		'(UTC-04:00) Atlantic Time (Canada)' => 'America/Halifax',
+		'(UTC-04:00) Caracas' => 'America/Caracas',
+		'(UTC-04:00) Cuiaba' => 'America/Cuiaba',
+		'(UTC-04:00) Georgetown, La Paz, Manaus, San Juan' => 'America/La_Paz',
+		'(UTC-04:00) Santiago' => 'America/Santiago',
+		'(UTC-03:30) Newfoundland' => 'America/St_Johns',
+		'(UTC-03:00) Brasilia' => 'America/Sao_Paulo',
+		'(UTC-03:00) Cayenne, Fortaleza' => 'America/Cayenne',
+		'(UTC-03:00) City of Buenos Aires' => 'America/Buenos_Aires',
+		'(UTC-03:00) Greenland' => 'America/Godthab',
+		'(UTC-03:00) Montevideo' => 'America/Montevideo',
+		'(UTC-03:00) Salvador' => 'America/Bahia',
+		'(UTC-02:00) Coordinated Universal Time-02' => 'Etc/GMT+2',
+		'(UTC-01:00) Azores' => 'Atlantic/Azores',
+		'(UTC-01:00) Cabo Verde Is.' => 'Atlantic/Cape_Verde',
+		'(UTC) Coordinated Universal Time' => 'Etc/GMT',
+		'(UTC+00:00) Casablanca' => 'Africa/Casablanca',
+		'(UTC+00:00) Dublin, Edinburgh, Lisbon, London' => 'Europe/London',
+		'(UTC+00:00) Monrovia, Reykjavik' => 'Atlantic/Reykjavik',
+		'(UTC+01:00) Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna' => 'Europe/Berlin',
+		'(UTC+01:00) Belgrade, Bratislava, Budapest, Ljubljana, Prague' => 'Europe/Budapest',
+		'(UTC+01:00) Brussels, Copenhagen, Madrid, Paris' => 'Europe/Paris',
+		'(UTC+01:00) Sarajevo, Skopje, Warsaw, Zagreb' => 'Europe/Warsaw',
+		'(UTC+01:00) West Central Africa' => 'Africa/Lagos',
+		'(UTC+02:00) Amman' => 'Asia/Amman',
+		'(UTC+02:00) Athens, Bucharest' => 'Europe/Bucharest',
+		'(UTC+02:00) Beirut' => 'Asia/Beirut',
+		'(UTC+02:00) Cairo' => 'Africa/Cairo',
+		'(UTC+02:00) Chisinau' => 'Europe/Chisinau',
+		'(UTC+02:00) Damascus' => 'Asia/Damascus',
+		'(UTC+02:00) Harare, Pretoria' => 'Africa/Johannesburg',
+		'(UTC+02:00) Helsinki, Kyiv, Riga, Sofia, Tallinn, Vilnius' => 'Europe/Kiev',
+		'(UTC+02:00) Jerusalem' => 'Asia/Jerusalem',
+		'(UTC+02:00) Kaliningrad' => 'Europe/Kaliningrad',
+		'(UTC+02:00) Tripoli' => 'Africa/Tripoli',
+		'(UTC+02:00) Windhoek' => 'Africa/Windhoek',
+		'(UTC+03:00) Baghdad' => 'Asia/Baghdad',
+		'(UTC+03:00) Istanbul' => 'Europe/Istanbul',
+		'(UTC+03:00) Kuwait, Riyadh' => 'Asia/Riyadh',
+		'(UTC+03:00) Minsk' => 'Europe/Minsk',
+		'(UTC+03:00) Moscow, St. Petersburg, Volgograd' => 'Europe/Moscow',
+		'(UTC+03:00) Nairobi' => 'Africa/Nairobi',
+		'(UTC+03:30) Tehran' => 'Asia/Tehran',
+		'(UTC+04:00) Abu Dhabi, Muscat' => 'Asia/Dubai',
+		'(UTC+04:00) Baku' => 'Asia/Baku',
+		'(UTC+04:00) Izhevsk, Samara' => 'Europe/Samara',
+		'(UTC+04:00) Port Louis' => 'Indian/Mauritius',
+		'(UTC+04:00) Tbilisi' => 'Asia/Tbilisi',
+		'(UTC+04:00) Yerevan' => 'Asia/Yerevan',
+		'(UTC+04:30) Kabul' => 'Asia/Kabul',
+		'(UTC+05:00) Ashgabat, Tashkent' => 'Asia/Tashkent',
+		'(UTC+05:00) Ekaterinburg' => 'Asia/Yekaterinburg',
+		'(UTC+05:00) Islamabad, Karachi' => 'Asia/Karachi',
+		'(UTC+05:30) Chennai, Kolkata, Mumbai, New Delhi' => 'Asia/Calcutta',
+		'(UTC+05:30) Sri Jayawardenepura' => 'Asia/Colombo',
+		'(UTC+05:45) Kathmandu' => 'Asia/Katmandu',
+		'(UTC+06:00) Astana' => 'Asia/Almaty',
+		'(UTC+06:00) Dhaka' => 'Asia/Dhaka',
+		'(UTC+06:30) Yangon (Rangoon)' => 'Asia/Rangoon',
+		'(UTC+07:00) Bangkok, Hanoi, Jakarta' => 'Asia/Bangkok',
+		'(UTC+07:00) Krasnoyarsk' => 'Asia/Krasnoyarsk',
+		'(UTC+07:00) Novosibirsk' => 'Asia/Novosibirsk',
+		'(UTC+08:00) Beijing, Chongqing, Hong Kong, Urumqi' => 'Asia/Shanghai',
+		'(UTC+08:00) Irkutsk' => 'Asia/Irkutsk',
+		'(UTC+08:00) Kuala Lumpur, Singapore' => 'Asia/Singapore',
+		'(UTC+08:00) Perth' => 'Australia/Perth',
+		'(UTC+08:00) Taipei' => 'Asia/Taipei',
+		'(UTC+08:00) Ulaanbaatar' => 'Asia/Ulaanbaatar',
+		'(UTC+09:00) Osaka, Sapporo, Tokyo' => 'Asia/Tokyo',
+		'(UTC+09:00) Pyongyang' => 'Asia/Pyongyang',
+		'(UTC+09:00) Seoul' => 'Asia/Seoul',
+		'(UTC+09:00) Yakutsk' => 'Asia/Yakutsk',
+		'(UTC+09:30) Adelaide' => 'Australia/Adelaide',
+		'(UTC+09:30) Darwin' => 'Australia/Darwin',
+		'(UTC+10:00) Brisbane' => 'Australia/Brisbane',
+		'(UTC+10:00) Canberra, Melbourne, Sydney' => 'Australia/Sydney',
+		'(UTC+10:00) Guam, Port Moresby' => 'Pacific/Port_Moresby',
+		'(UTC+10:00) Hobart' => 'Australia/Hobart',
+		'(UTC+10:00) Vladivostok' => 'Asia/Vladivostok',
+		'(UTC+11:00) Chokurdakh' => 'Asia/Srednekolymsk',
+		'(UTC+11:00) Magadan' => 'Asia/Magadan',
+		'(UTC+11:00) Solomon Is., New Caledonia' => 'Pacific/Guadalcanal',
+		'(UTC+12:00) Anadyr, Petropavlovsk-Kamchatsky' => 'Asia/Kamchatka',
+		'(UTC+12:00) Auckland, Wellington' => 'Pacific/Auckland',
+		'(UTC+12:00) Coordinated Universal Time+12' => 'Etc/GMT-12',
+		'(UTC+12:00) Fiji' => 'Pacific/Fiji',
+		"(UTC+13:00) Nuku'alofa" => 'Pacific/Tongatapu',
+		'(UTC+13:00) Samoa' => 'Pacific/Apia',
+		'(UTC+14:00) Kiritimati Island' => 'Pacific/Kiritimati',
+	);
+
+	/**
+	 * Maps Windows (non-CLDR) time zone ID to IANA ID. This is pragmatic but not 100% precise as one Windows zone ID
+	 * maps to multiple IANA IDs (one for each territory). For all practical purposes this should be good enough, though.
+	 *
+	 * Source: http://unicode.org/repos/cldr/trunk/common/supplemental/windowsZones.xml
+	 *
+	 * @var array
+	 */
+	private static $windowsTimeZonesMap = array(
+		'AUS Central Standard Time' => 'Australia/Darwin',
+		'AUS Eastern Standard Time' => 'Australia/Sydney',
+		'Afghanistan Standard Time' => 'Asia/Kabul',
+		'Alaskan Standard Time' => 'America/Anchorage',
+		'Aleutian Standard Time' => 'America/Adak',
+		'Altai Standard Time' => 'Asia/Barnaul',
+		'Arab Standard Time' => 'Asia/Riyadh',
+		'Arabian Standard Time' => 'Asia/Dubai',
+		'Arabic Standard Time' => 'Asia/Baghdad',
+		'Argentina Standard Time' => 'America/Buenos_Aires',
+		'Astrakhan Standard Time' => 'Europe/Astrakhan',
+		'Atlantic Standard Time' => 'America/Halifax',
+		'Aus Central W. Standard Time' => 'Australia/Eucla',
+		'Azerbaijan Standard Time' => 'Asia/Baku',
+		'Azores Standard Time' => 'Atlantic/Azores',
+		'Bahia Standard Time' => 'America/Bahia',
+		'Bangladesh Standard Time' => 'Asia/Dhaka',
+		'Belarus Standard Time' => 'Europe/Minsk',
+		'Bougainville Standard Time' => 'Pacific/Bougainville',
+		'Canada Central Standard Time' => 'America/Regina',
+		'Cape Verde Standard Time' => 'Atlantic/Cape_Verde',
+		'Caucasus Standard Time' => 'Asia/Yerevan',
+		'Cen. Australia Standard Time' => 'Australia/Adelaide',
+		'Central America Standard Time' => 'America/Guatemala',
+		'Central Asia Standard Time' => 'Asia/Almaty',
+		'Central Brazilian Standard Time' => 'America/Cuiaba',
+		'Central Europe Standard Time' => 'Europe/Budapest',
+		'Central European Standard Time' => 'Europe/Warsaw',
+		'Central Pacific Standard Time' => 'Pacific/Guadalcanal',
+		'Central Standard Time (Mexico)' => 'America/Mexico_City',
+		'Central Standard Time' => 'America/Chicago',
+		'Chatham Islands Standard Time' => 'Pacific/Chatham',
+		'China Standard Time' => 'Asia/Shanghai',
+		'Cuba Standard Time' => 'America/Havana',
+		'Dateline Standard Time' => 'Etc/GMT+12',
+		'E. Africa Standard Time' => 'Africa/Nairobi',
+		'E. Australia Standard Time' => 'Australia/Brisbane',
+		'E. Europe Standard Time' => 'Europe/Chisinau',
+		'E. South America Standard Time' => 'America/Sao_Paulo',
+		'Easter Island Standard Time' => 'Pacific/Easter',
+		'Eastern Standard Time (Mexico)' => 'America/Cancun',
+		'Eastern Standard Time' => 'America/New_York',
+		'Egypt Standard Time' => 'Africa/Cairo',
+		'Ekaterinburg Standard Time' => 'Asia/Yekaterinburg',
+		'FLE Standard Time' => 'Europe/Kiev',
+		'Fiji Standard Time' => 'Pacific/Fiji',
+		'GMT Standard Time' => 'Europe/London',
+		'GTB Standard Time' => 'Europe/Bucharest',
+		'Georgian Standard Time' => 'Asia/Tbilisi',
+		'Greenland Standard Time' => 'America/Godthab',
+		'Greenwich Standard Time' => 'Atlantic/Reykjavik',
+		'Haiti Standard Time' => 'America/Port-au-Prince',
+		'Hawaiian Standard Time' => 'Pacific/Honolulu',
+		'India Standard Time' => 'Asia/Calcutta',
+		'Iran Standard Time' => 'Asia/Tehran',
+		'Israel Standard Time' => 'Asia/Jerusalem',
+		'Jordan Standard Time' => 'Asia/Amman',
+		'Kaliningrad Standard Time' => 'Europe/Kaliningrad',
+		'Korea Standard Time' => 'Asia/Seoul',
+		'Libya Standard Time' => 'Africa/Tripoli',
+		'Line Islands Standard Time' => 'Pacific/Kiritimati',
+		'Lord Howe Standard Time' => 'Australia/Lord_Howe',
+		'Magadan Standard Time' => 'Asia/Magadan',
+		'Magallanes Standard Time' => 'America/Punta_Arenas',
+		'Marquesas Standard Time' => 'Pacific/Marquesas',
+		'Mauritius Standard Time' => 'Indian/Mauritius',
+		'Middle East Standard Time' => 'Asia/Beirut',
+		'Montevideo Standard Time' => 'America/Montevideo',
+		'Morocco Standard Time' => 'Africa/Casablanca',
+		'Mountain Standard Time (Mexico)' => 'America/Chihuahua',
+		'Mountain Standard Time' => 'America/Denver',
+		'Myanmar Standard Time' => 'Asia/Rangoon',
+		'N. Central Asia Standard Time' => 'Asia/Novosibirsk',
+		'Namibia Standard Time' => 'Africa/Windhoek',
+		'Nepal Standard Time' => 'Asia/Katmandu',
+		'New Zealand Standard Time' => 'Pacific/Auckland',
+		'Newfoundland Standard Time' => 'America/St_Johns',
+		'Norfolk Standard Time' => 'Pacific/Norfolk',
+		'North Asia East Standard Time' => 'Asia/Irkutsk',
+		'North Asia Standard Time' => 'Asia/Krasnoyarsk',
+		'North Korea Standard Time' => 'Asia/Pyongyang',
+		'Omsk Standard Time' => 'Asia/Omsk',
+		'Pacific SA Standard Time' => 'America/Santiago',
+		'Pacific Standard Time (Mexico)' => 'America/Tijuana',
+		'Pacific Standard Time' => 'America/Los_Angeles',
+		'Pakistan Standard Time' => 'Asia/Karachi',
+		'Paraguay Standard Time' => 'America/Asuncion',
+		'Romance Standard Time' => 'Europe/Paris',
+		'Russia Time Zone 10' => 'Asia/Srednekolymsk',
+		'Russia Time Zone 11' => 'Asia/Kamchatka',
+		'Russia Time Zone 3' => 'Europe/Samara',
+		'Russian Standard Time' => 'Europe/Moscow',
+		'SA Eastern Standard Time' => 'America/Cayenne',
+		'SA Pacific Standard Time' => 'America/Bogota',
+		'SA Western Standard Time' => 'America/La_Paz',
+		'SE Asia Standard Time' => 'Asia/Bangkok',
+		'Saint Pierre Standard Time' => 'America/Miquelon',
+		'Sakhalin Standard Time' => 'Asia/Sakhalin',
+		'Samoa Standard Time' => 'Pacific/Apia',
+		'Sao Tome Standard Time' => 'Africa/Sao_Tome',
+		'Saratov Standard Time' => 'Europe/Saratov',
+		'Singapore Standard Time' => 'Asia/Singapore',
+		'South Africa Standard Time' => 'Africa/Johannesburg',
+		'Sri Lanka Standard Time' => 'Asia/Colombo',
+		'Sudan Standard Time' => 'Africa/Tripoli',
+		'Syria Standard Time' => 'Asia/Damascus',
+		'Taipei Standard Time' => 'Asia/Taipei',
+		'Tasmania Standard Time' => 'Australia/Hobart',
+		'Tocantins Standard Time' => 'America/Araguaina',
+		'Tokyo Standard Time' => 'Asia/Tokyo',
+		'Tomsk Standard Time' => 'Asia/Tomsk',
+		'Tonga Standard Time' => 'Pacific/Tongatapu',
+		'Transbaikal Standard Time' => 'Asia/Chita',
+		'Turkey Standard Time' => 'Europe/Istanbul',
+		'Turks And Caicos Standard Time' => 'America/Grand_Turk',
+		'US Eastern Standard Time' => 'America/Indianapolis',
+		'US Mountain Standard Time' => 'America/Phoenix',
+		'UTC' => 'Etc/GMT',
+		'UTC+12' => 'Etc/GMT-12',
+		'UTC+13' => 'Etc/GMT-13',
+		'UTC-02' => 'Etc/GMT+2',
+		'UTC-08' => 'Etc/GMT+8',
+		'UTC-09' => 'Etc/GMT+9',
+		'UTC-11' => 'Etc/GMT+11',
+		'Ulaanbaatar Standard Time' => 'Asia/Ulaanbaatar',
+		'Venezuela Standard Time' => 'America/Caracas',
+		'Vladivostok Standard Time' => 'Asia/Vladivostok',
+		'W. Australia Standard Time' => 'Australia/Perth',
+		'W. Central Africa Standard Time' => 'Africa/Lagos',
+		'W. Europe Standard Time' => 'Europe/Berlin',
+		'W. Mongolia Standard Time' => 'Asia/Hovd',
+		'West Asia Standard Time' => 'Asia/Tashkent',
+		'West Bank Standard Time' => 'Asia/Hebron',
+		'West Pacific Standard Time' => 'Pacific/Port_Moresby',
+		'Yakutsk Standard Time' => 'Asia/Yakutsk',
+	);
+
+	/**
+	 * If `$filterDaysBefore` or `$filterDaysAfter` are set then the events are filtered according to the window defined
+	 * by this field and `$windowMaxTimestamp`.
+	 *
+	 * @var integer
+	 */
+	private $windowMinTimestamp;
+
+	/**
+	 * If `$filterDaysBefore` or `$filterDaysAfter` are set then the events are filtered according to the window defined
+	 * by this field and `$windowMinTimestamp`.
+	 *
+	 * @var integer
+	 */
+	private $windowMaxTimestamp;
+
+	/**
+	 * `true` if either `$filterDaysBefore` or `$filterDaysAfter` are set.
+	 *
+	 * @var boolean
+	 */
+	private $shouldFilterByWindow;
+
+	/**
+	 * Creates the ICal object
+	 *
+	 * @param mixed $files
+	 * @param array $options
+	 * @return void
+	 * @throws Exception
+	 */
+	public function __construct(array $options = array())
+	{
+		ini_set('auto_detect_line_endings', '1');
+
+		foreach ($options as $option => $value) {
+			if (in_array($option, self::$configurableOptions)) {
+				$this->{$option} = $value;
+			}
+		}
+
+		// Fallback to use the system default time zone
+		if (!isset($this->defaultTimeZone) || !$this->isValidTimeZoneId($this->defaultTimeZone)) {
+			$this->defaultTimeZone = date_default_timezone_get();
+		}
+
+		// Ideally you would use `PHP_INT_MIN` from PHP 7
+		$php_int_min = -2147483648;
+
+		$this->windowMinTimestamp = is_null($this->filterDaysBefore) ? $php_int_min : (new DateTime('now'))->sub(new DateInterval('P' . $this->filterDaysBefore . 'D'))->getTimestamp();
+		$this->windowMaxTimestamp = is_null($this->filterDaysAfter) ? PHP_INT_MAX : (new DateTime('now'))->add(new DateInterval('P' . $this->filterDaysAfter . 'D'))->getTimestamp();
+
+		$this->shouldFilterByWindow = !is_null($this->filterDaysBefore) || !is_null($this->filterDaysAfter);
+	}
+
+	/**
+	 * Feed more data to the parser. This can be a chunk of arbitrary length, it
+	 * is not required to end on a line break.
+	 *
+	 * @param string $data
+	 */
+	public function feedData($data)
+	{
+		$this->feedBuffer .= $data;
+		$start = 0;
+		$bufferLen = strlen($this->feedBuffer);
+		while (($newLine = strcspn($this->feedBuffer, "\r\n", $start) + $start) !== $bufferLen) {
+			$length = $newLine - $start;
+			if ($length > 1) {
+				if ($this->feedBuffer[$start] === ' ' || $this->feedBuffer[$start] === '\t') {
+					// Continuation of previous line
+					$this->currentLineBuffer .= substr($this->feedBuffer, $start + 1, $length - 1);
+				} else {
+					// New line, flush previous one
+					$this->handleLine($this->currentLineBuffer);
+					$this->currentLineBuffer = substr($this->feedBuffer, $start, $length);
+				}
+			}
+			$start = $newLine + 1;
+		}
+		$this->feedBuffer = substr($this->feedBuffer, $start);
+	}
+
+	/**
+	 * Finish feeding more data to the parser, process the data.
+	 */
+	public function finish()
+	{
+		// Flush
+		$this->feedData("\n*\n");
+		$this->currentLineBuffer = '';
+		$this->feedBuffer = '';
+		$this->processEvents();
+
+		if (!$this->skipRecurrence) {
+			$this->processRecurrences();
+
+			// Apply changes to altered recurrence instances
+			if (!empty($this->alteredRecurrenceInstances)) {
+				$events = $this->cal['VEVENT'];
+
+				foreach ($this->alteredRecurrenceInstances as $alteredRecurrenceInstance) {
+					if (isset($alteredRecurrenceInstance['altered-event'])) {
+						$alteredEvent = $alteredRecurrenceInstance['altered-event'];
+						$key = key($alteredEvent);
+						$events[$key] = $alteredEvent[$key];
+					}
+				}
+
+				$this->cal['VEVENT'] = $events;
+			}
+		}
+
+		if ($this->shouldFilterByWindow) {
+			$this->reduceEventsToMinMaxRange();
+		}
+
+		$this->processDateConversions();
+	}
+
+	/**
+	 * True if this resembles a calendar, i.e. we've seen the
+	 * BEGIN:VCALENDAR line at some point.
+	 *
+	 * @return bool
+	 */
+	public function isValid()
+	{
+		return $this->hasSeenStart;
+	}
+
+	/**
+	 * Process next completed line from file
+	 *
+	 * @param string $line
+	 */
+	protected function handleLine($line)
+	{
+		$line = rtrim($line); // Trim trailing whitespace
+		$line = $this->removeUnprintableChars($line);
+
+		if (empty($line)) {
+			return;
+		}
+
+		$add = $this->keyValueFromString($line);
+
+		if ($add === false) {
+			return;
+		}
+
+		$keyword = $add[0];
+		$values = $add[1]; // May be an array containing multiple values
+
+		if (!is_array($values)) {
+			if (!empty($values)) {
+				$values = array($values); // Make an array as not already
+				$blankArray = array(); // Empty placeholder array
+				array_push($values, $blankArray);
+			} else {
+				$values = array(); // Use blank array to ignore this line
+			}
+		} elseif (empty($values[0])) {
+			$values = array(); // Use blank array to ignore this line
+		}
+
+		// Reverse so that our array of properties is processed first
+		$values = array_reverse($values);
+
+		foreach ($values as $value) {
+			switch ($line) {
+				// https://www.kanzaki.com/docs/ical/vtodo.html
+			case 'BEGIN:VTODO':
+				if (!is_array($value)) {
+					$this->todoCount++;
+				}
+
+				$this->parseStateComponent = 'VTODO';
+
+				break;
+
+				// https://www.kanzaki.com/docs/ical/vevent.html
+			case 'BEGIN:VEVENT':
+				if (!is_array($value)) {
+					$this->eventCount++;
+				}
+
+				$this->parseStateComponent = 'VEVENT';
+
+				break;
+
+				// https://www.kanzaki.com/docs/ical/vfreebusy.html
+			case 'BEGIN:VFREEBUSY':
+				if (!is_array($value)) {
+					$this->freeBusyIndex++;
+				}
+
+				$this->parseStateComponent = 'VFREEBUSY';
+
+				break;
+
+			case 'BEGIN:VALARM':
+				if (!is_array($value)) {
+					$this->alarmCount++;
+				}
+
+				$this->parseStateComponent = 'VALARM';
+
+				break;
+
+			case 'END:VALARM':
+				$this->parseStateComponent = 'VEVENT';
+
+				break;
+
+			case 'BEGIN:DAYLIGHT':
+			case 'BEGIN:STANDARD':
+			case 'BEGIN:VTIMEZONE':
+				$this->parseStateComponent = $value;
+
+				break;
+
+			case 'END:DAYLIGHT':
+			case 'END:STANDARD':
+			case 'END:VFREEBUSY':
+			case 'END:VTIMEZONE':
+			case 'END:VTODO':
+				$this->parseStateComponent = 'VCALENDAR';
+
+				break;
+
+			case 'BEGIN:VCALENDAR':
+				$this->hasSeenStart = true;
+				$this->parseStateComponent = $value;
+
+				break;
+
+			case 'END:VCALENDAR':
+				$this->parseStateComponent = '';
+
+				break;
+
+			case 'END:VEVENT':
+				if ($this->shouldFilterByWindow) {
+					$this->removeLastEventIfOutsideWindowAndNonRecurring();
+				}
+
+				$this->parseStateComponent = 'VCALENDAR';
+
+				break;
+
+			default:
+				if (!empty($this->parseStateComponent)) {
+					$this->addCalendarComponentWithKeyAndValue($this->parseStateComponent, $keyword, $value);
+				}
+				break;
+			}
+		}
+	}
+
+	/**
+	 * Removes the last event (i.e. most recently parsed) if its start date is outside the window spanned by
+	 * `$windowMinTimestamp` / `$windowMaxTimestamp`.
+	 *
+	 * @return void
+	 */
+	protected function removeLastEventIfOutsideWindowAndNonRecurring()
+	{
+		$events = $this->cal['VEVENT'];
+
+		if (!empty($events)) {
+			$lastIndex = count($events) - 1;
+			$lastEvent = $events[$lastIndex];
+
+			if (empty($lastEvent['RRULE']) && $this->doesEventStartOutsideWindow($lastEvent)) {
+				$this->eventCount--;
+
+				unset($events[$lastIndex]);
+			}
+
+			$this->cal['VEVENT'] = $events;
+		}
+	}
+
+	/**
+	 * Reduces the number of events to the defined minimum and maximum range
+	 *
+	 * @return void
+	 */
+	protected function reduceEventsToMinMaxRange()
+	{
+		$events = (isset($this->cal['VEVENT'])) ? $this->cal['VEVENT'] : array();
+
+		if (!empty($events)) {
+			foreach ($events as $key => $anEvent) {
+				if ($anEvent === null) {
+					unset($events[$key]);
+
+					continue;
+				}
+
+				if ($this->doesEventStartOutsideWindow($anEvent)) {
+					$this->eventCount--;
+
+					unset($events[$key]);
+
+					continue;
+				}
+			}
+
+			$this->cal['VEVENT'] = $events;
+		}
+	}
+
+	/**
+	 * Determines whether the event start date is outside `$windowMinTimestamp` / `$windowMaxTimestamp`.
+	 * Returns `true` for invalid dates.
+	 *
+	 * @param array $event
+	 * @return boolean
+	 */
+	protected function doesEventStartOutsideWindow(array $event)
+	{
+		return !$this->isValidDate($event['DTSTART']) || $this->isOutOfRange($event['DTSTART'], $this->windowMinTimestamp, $this->windowMaxTimestamp);
+	}
+
+	/**
+	 * Determines whether a valid iCalendar date is within a given range
+	 *
+	 * @param string $calendarDate
+	 * @param integer $minTimestamp
+	 * @param integer $maxTimestamp
+	 * @return boolean
+	 */
+	protected function isOutOfRange($calendarDate, $minTimestamp, $maxTimestamp)
+	{
+		$timestamp = strtotime(explode('T', $calendarDate)[0]);
+
+		return $timestamp < $minTimestamp || $timestamp > $maxTimestamp;
+	}
+
+	/**
+	 * Unfolds an iCal file in preparation for parsing
+	 * (https://icalendar.org/iCalendar-RFC-5545/3-1-content-lines.html)
+	 *
+	 * @param array $lines
+	 * @return array
+	 */
+	protected function unfold(array $lines)
+	{
+		$string = implode(PHP_EOL, $lines);
+		$string = preg_replace('/' . PHP_EOL . '[ \t]/', '', $string);
+
+		$lines = explode(PHP_EOL, $string);
+
+		return $lines;
+	}
+
+	/**
+	 * Add one key and value pair to the `$this->cal` array
+	 *
+	 * @param string $component
+	 * @param string|boolean $keyword
+	 * @param string $value
+	 * @return void
+	 */
+	protected function addCalendarComponentWithKeyAndValue($component, $keyword, $value)
+	{
+		if ($keyword == false) {
+			$keyword = $this->lastKeyword;
+		}
+
+		switch ($component) {
+		case 'VALARM':
+			$key1 = 'VEVENT';
+			$key2 = ($this->eventCount - 1);
+			$key3 = $component;
+
+			if (!isset($this->cal[$key1][$key2][$key3]["{$keyword}_array"])) {
+				$this->cal[$key1][$key2][$key3]["{$keyword}_array"] = array();
+			}
+
+			if (is_array($value)) {
+				// Add array of properties to the end
+				array_push($this->cal[$key1][$key2][$key3]["{$keyword}_array"], $value);
+			} else {
+				if (!isset($this->cal[$key1][$key2][$key3][$keyword])) {
+					$this->cal[$key1][$key2][$key3][$keyword] = $value;
+				}
+
+				if ($this->cal[$key1][$key2][$key3][$keyword] !== $value) {
+					$this->cal[$key1][$key2][$key3][$keyword] .= ',' . $value;
+				}
+			}
+			break;
+
+		case 'VEVENT':
+			$key1 = $component;
+			$key2 = ($this->eventCount - 1);
+
+			if (!isset($this->cal[$key1][$key2]["{$keyword}_array"])) {
+				$this->cal[$key1][$key2]["{$keyword}_array"] = array();
+			}
+
+			if (is_array($value)) {
+				// Add array of properties to the end
+				array_push($this->cal[$key1][$key2]["{$keyword}_array"], $value);
+			} else {
+				if (!isset($this->cal[$key1][$key2][$keyword])) {
+					$this->cal[$key1][$key2][$keyword] = $value;
+				}
+
+				if ($keyword === 'EXDATE') {
+					if (trim($value) === $value) {
+						$array = array_filter(explode(',', $value));
+						$this->cal[$key1][$key2]["{$keyword}_array"][] = $array;
+					} else {
+						$value = explode(',', implode(',', $this->cal[$key1][$key2]["{$keyword}_array"][1]) . trim($value));
+						$this->cal[$key1][$key2]["{$keyword}_array"][1] = $value;
+					}
+				} else {
+					$this->cal[$key1][$key2]["{$keyword}_array"][] = $value;
+
+					if ($keyword === 'DURATION') {
+						try {
+							$duration = new DateInterval($value);
+							array_push($this->cal[$key1][$key2]["{$keyword}_array"], $duration);
+						} catch (Exception $e) {
+							error_log('Ignoring invalid duration ' . $value);
+						}
+					}
+				}
+
+				if ($this->cal[$key1][$key2][$keyword] !== $value) {
+					$this->cal[$key1][$key2][$keyword] .= ',' . $value;
+				}
+			}
+			break;
+
+		case 'VFREEBUSY':
+			$key1 = $component;
+			$key2 = ($this->freeBusyIndex - 1);
+			$key3 = $keyword;
+
+			if ($keyword === 'FREEBUSY') {
+				if (is_array($value)) {
+					$this->cal[$key1][$key2][$key3][][] = $value;
+				} else {
+					$this->freeBusyCount++;
+
+					end($this->cal[$key1][$key2][$key3]);
+					$key = key($this->cal[$key1][$key2][$key3]);
+
+					$value = explode('/', $value);
+					$this->cal[$key1][$key2][$key3][$key][] = $value;
+				}
+			} else {
+				$this->cal[$key1][$key2][$key3][] = $value;
+			}
+			break;
+
+		case 'VTODO':
+			$this->cal[$component][$this->todoCount - 1][$keyword] = $value;
+
+			break;
+
+		default:
+			$this->cal[$component][$keyword] = $value;
+
+			break;
+		}
+
+		$this->lastKeyword = $keyword;
+	}
+
+	/**
+	 * Gets the key value pair from an iCal string
+	 *
+	 * @param string $text
+	 * @return array|boolean
+	 */
+	protected function keyValueFromString($text)
+	{
+		$text = htmlspecialchars($text, ENT_NOQUOTES, 'UTF-8');
+
+		$colon = strpos($text, ':');
+		$quote = strpos($text, '"');
+		if ($colon === false) {
+			$matches = array();
+		} elseif ($quote === false || $colon < $quote) {
+			list($before, $after) = explode(':', $text, 2);
+			$matches = array($text, $before, $after);
+		} else {
+			list($before, $text) = explode('"', $text, 2);
+			$text = '"' . $text;
+			$matches = str_getcsv($text, ':');
+			$combinedValue = '';
+
+			foreach (array_keys($matches) as $key) {
+				if ($key === 0) {
+					if (!empty($before)) {
+						$matches[$key] = $before . '"' . $matches[$key] . '"';
+					}
+				} else {
+					if ($key > 1) {
+						$combinedValue .= ':';
+					}
+
+					$combinedValue .= $matches[$key];
+				}
+			}
+
+			$matches = array_slice($matches, 0, 2);
+			$matches[1] = $combinedValue;
+			array_unshift($matches, $before . $text);
+		}
+
+		if (count($matches) === 0) {
+			return false;
+		}
+
+		if (preg_match('/^([A-Z-]+)([;][\w\W]*)?$/', $matches[1])) {
+			$matches = array_splice($matches, 1, 2); // Remove first match and re-align ordering
+
+			// Process properties
+			if (preg_match('/([A-Z-]+)[;]([\w\W]*)/', $matches[0], $properties)) {
+				// Remove first match
+				array_shift($properties);
+				// Fix to ignore everything in keyword after a ; (e.g. Language, TZID, etc.)
+				$matches[0] = $properties[0];
+				array_shift($properties); // Repeat removing first match
+
+				$formatted = array();
+				foreach ($properties as $property) {
+					// Match semicolon separator outside of quoted substrings
+					preg_match_all('~[^' . PHP_EOL . '";]+(?:"[^"\\\]*(?:\\\.[^"\\\]*)*"[^' . PHP_EOL . '";]*)*~', $property, $attributes);
+					// Remove multi-dimensional array and use the first key
+					$attributes = (count($attributes) === 0) ? array($property) : reset($attributes);
+
+					if (is_array($attributes)) {
+						foreach ($attributes as $attribute) {
+							// Match equals sign separator outside of quoted substrings
+							preg_match_all(
+								'~[^' . PHP_EOL . '"=]+(?:"[^"\\\]*(?:\\\.[^"\\\]*)*"[^' . PHP_EOL . '"=]*)*~',
+								$attribute,
+								$values
+							);
+							// Remove multi-dimensional array and use the first key
+							$value = (count($values) === 0) ? null : reset($values);
+
+							if (is_array($value) && isset($value[1])) {
+								// Remove double quotes from beginning and end only
+								$formatted[$value[0]] = trim($value[1], '"');
+							}
+						}
+					}
+				}
+
+				// Assign the keyword property information
+				$properties[0] = $formatted;
+
+				// Add match to beginning of array
+				array_unshift($properties, $matches[1]);
+				$matches[1] = $properties;
+			}
+
+			return $matches;
+		} else {
+			return false; // Ignore this match
+		}
+	}
+
+	/**
+	 * Returns a `DateTime` object from an iCal date time format
+	 *
+	 * @param string $icalDate
+	 * @return DateTime
+	 */
+	public function iCalDateToDateTime($icalDate)
+	{
+		/**
+		 * iCal times may be in 3 formats, (https://www.kanzaki.com/docs/ical/dateTime.html)
+		 *
+		 * UTC:      Has a trailing 'Z'
+		 * Floating: No time zone reference specified, no trailing 'Z', use local time
+		 * TZID:     Set time zone as specified
+		 *
+		 * Use DateTime class objects to get around limitations with `mktime` and `gmmktime`.
+		 * Must have a local time zone set to process floating times.
+		 */
+		$pattern = '/^(?:TZID=)?([^:]*|".*")'; // [1]: Time zone
+		$pattern .= ':?';                       //      Time zone delimiter
+		$pattern .= '([0-9]{8})';               // [2]: YYYYMMDD
+		$pattern .= 'T?';                       //      Time delimiter
+		$pattern .= '(?(?<=T)([0-9]{6}))';      // [3]: HHMMSS (filled if delimiter present)
+		$pattern .= '(Z?)/';                    // [4]: UTC flag
+
+		preg_match($pattern, $icalDate, $date);
+
+		if (empty($date)) {
+			error_log('Invalid iCal date format: ' . $icalDate);
+			return new Datetime('1970-08-08'); // Return something far in the past
+		}
+
+		// A Unix timestamp usually cannot represent a date prior to 1 Jan 1970.
+		// PHP, on the other hand, uses negative numbers for that. Thus we don't
+		// need to special case them.
+
+		if ($date[4] === 'Z') {
+			$dateTimeZone = new DateTimeZone(self::TIME_ZONE_UTC);
+		} elseif (!empty($date[1])) {
+			$dateTimeZone = $this->timeZoneStringToDateTimeZone($date[1]);
+		} else {
+			$dateTimeZone = new DateTimeZone($this->defaultTimeZone);
+		}
+
+		// The exclamation mark at the start of the format string indicates that if a
+		// time portion is not included, the time in the returned DateTime should be
+		// set to 00:00:00. Without it, the time would be set to the current system time.
+		$dateFormat = '!Ymd';
+		$dateBasic = $date[2];
+		if (!empty($date[3])) {
+			$dateBasic .= "T{$date[3]}";
+			$dateFormat .= '\THis';
+		}
+
+		return DateTime::createFromFormat($dateFormat, $dateBasic, $dateTimeZone);
+	}
+
+	/**
+	 * Returns a Unix timestamp from an iCal date time format
+	 *
+	 * @param string $icalDate
+	 * @return integer
+	 */
+	public function iCalDateToUnixTimestamp($icalDate)
+	{
+		return $this->iCalDateToDateTime($icalDate)->getTimestamp();
+	}
+
+	/**
+	 * Returns a date adapted to the calendar time zone depending on the event `TZID`
+	 *
+	 * @param array $event
+	 * @param string $key
+	 * @param string $format
+	 * @return string|boolean
+	 */
+	public function iCalDateWithTimeZone(array $event, $key, $format = self::DATE_TIME_FORMAT)
+	{
+		if (!isset($event["{$key}_array"]) || !isset($event[$key])) {
+			return false;
+		}
+
+		$dateArray = $event["{$key}_array"];
+
+		if ($key === 'DURATION') {
+			$dateTime = $this->parseDuration($event['DTSTART'], $dateArray[2], null);
+		} else {
+			// When constructing from a Unix Timestamp, no time zone needs passing.
+			$dateTime = new DateTime("@{$dateArray[2]}");
+		}
+
+		// Set the time zone we wish to use when running `$dateTime->format`.
+		$dateTime->setTimezone(new DateTimeZone($this->calendarTimeZone()));
+
+		if (is_null($format)) {
+			return $dateTime;
+		}
+
+		return $dateTime->format($format);
+	}
+
+	/**
+	 * Performs admin tasks on all events as read from the iCal file.
+	 * Adds a Unix timestamp to all `{DTSTART|DTEND|RECURRENCE-ID}_array` arrays
+	 * Tracks modified recurrence instances
+	 *
+	 * @return void
+	 */
+	protected function processEvents()
+	{
+		if (empty($this->cal['VEVENT']))
+			return;
+		$events =& $this->cal['VEVENT'];
+		$checks = null;
+
+		foreach ($events as $key => $anEvent) {
+			foreach (array('DTSTART', 'DTEND', 'RECURRENCE-ID') as $type) {
+				if (isset($anEvent[$type])) {
+					$date = $anEvent["{$type}_array"][1];
+
+					if (isset($anEvent["{$type}_array"][0]['TZID'])) {
+						$timeZone = $this->escapeParamText($anEvent["{$type}_array"][0]['TZID']);
+						$date = sprintf(self::ICAL_DATE_TIME_TEMPLATE, $timeZone) . $date;
+					}
+
+					$anEvent["{$type}_array"][2] = $this->iCalDateToUnixTimestamp($date);
+					$anEvent["{$type}_array"][3] = $date;
+				}
+			}
+
+			if (isset($anEvent['RECURRENCE-ID'])) {
+				$uid = $anEvent['UID'];
+
+				if (!isset($this->alteredRecurrenceInstances[$uid])) {
+					$this->alteredRecurrenceInstances[$uid] = array();
+				}
+
+				$recurrenceDateUtc = $this->iCalDateToUnixTimestamp($anEvent['RECURRENCE-ID_array'][3]);
+				$this->alteredRecurrenceInstances[$uid][$key] = $recurrenceDateUtc;
+			}
+
+			$events[$key] = $anEvent;
+		}
+
+		$eventKeysToRemove = array();
+
+		foreach ($events as $key => $event) {
+			$checks[] = !isset($event['RECURRENCE-ID']);
+			$checks[] = isset($event['UID']);
+			$checks[] = isset($event['UID']) && isset($this->alteredRecurrenceInstances[$event['UID']]);
+
+			if ((bool)array_product($checks)) {
+				$eventDtstartUnix = $this->iCalDateToUnixTimestamp($event['DTSTART_array'][3]);
+
+				// phpcs:ignore CustomPHPCS.ControlStructures.AssignmentInCondition
+				if (($alteredEventKey = array_search($eventDtstartUnix, $this->alteredRecurrenceInstances[$event['UID']])) !== false) {
+					$eventKeysToRemove[] = $alteredEventKey;
+
+					$alteredEvent = array_replace_recursive($events[$key], $events[$alteredEventKey]);
+					$this->alteredRecurrenceInstances[$event['UID']]['altered-event'] = array($key => $alteredEvent);
+				}
+			}
+
+			unset($checks);
+		}
+
+		foreach ($eventKeysToRemove as $eventKeyToRemove) {
+			$events[$eventKeyToRemove] = null;
+		}
+	}
+
+	/**
+	 * Processes recurrence rules
+	 *
+	 * @return void
+	 */
+	protected function processRecurrences()
+	{
+		// If there are no events, then we have nothing to process.
+		if (empty($this->cal['VEVENT']))
+			return;
+		$events =& $this->cal['VEVENT'];
+
+		$allEventRecurrences = array();
+		$eventKeysToRemove = array();
+
+		foreach ($events as $key => $anEvent) {
+			if (!isset($anEvent['RRULE']) || $anEvent['RRULE'] === '') {
+				continue;
+			}
+
+			// Tag as generated by a recurrence rule
+			$anEvent['RRULE_array'][2] = self::RECURRENCE_EVENT;
+
+			// Create new initial starting point.
+			$initialEventDate = $this->icalDateToDateTime($anEvent['DTSTART_array'][3]);
+
+			// Separate the RRULE stanzas, and explode the values that are lists.
+			$rrules = array();
+			foreach (explode(';', $anEvent['RRULE']) as $s) {
+				list($k, $v) = explode('=', $s);
+				if (in_array($k, array('BYSETPOS', 'BYDAY', 'BYMONTHDAY', 'BYMONTH'))) {
+					$rrules[$k] = explode(',', $v);
+				} else {
+					$rrules[$k] = $v;
+				}
+			}
+
+			// Get frequency
+			$frequency = $rrules['FREQ'];
+
+			// Reject RRULE if BYDAY stanza is invalid:
+			// > The BYDAY rule part MUST NOT be specified with a numeric value
+			// > when the FREQ rule part is not set to MONTHLY or YEARLY.
+			if (isset($rrules['BYDAY']) && !in_array($frequency, array('MONTHLY', 'YEARLY'))) {
+				$allByDayStanzasValid = array_reduce($rrules['BYDAY'], function ($carry, $weekday) {
+					return $carry && substr($weekday, -2) === $weekday;
+				}, true);
+
+				if (!$allByDayStanzasValid) {
+					error_log("ICal::ProcessRecurrences: A \"{$frequency}\" RRULE should not contain BYDAY values with numeric prefixes");
+
+					continue;
+				}
+			}
+
+			// Get Interval
+			$interval = (empty($rrules['INTERVAL'])) ? 1 : $rrules['INTERVAL'];
+
+			// Throw an error if this isn't an integer.
+			if (!is_int($this->defaultSpan)) {
+				trigger_error('ICal::defaultSpan: User defined value is not an integer', E_USER_NOTICE);
+			}
+
+			// Compute EXDATEs
+			$exdates = $this->parseExdates($anEvent);
+
+			// Determine if the initial date is also an EXDATE
+			$initialDateIsExdate = array_reduce($exdates, function ($carry, $exdate) use ($initialEventDate) {
+				return $carry || $exdate->getTimestamp() === $initialEventDate->getTimestamp();
+			}, false);
+
+			if ($initialDateIsExdate) {
+				$eventKeysToRemove[] = $key;
+			}
+
+			/**
+			 * Determine at what point we should stop calculating recurrences
+			 * by looking at the UNTIL or COUNT rrule stanza, or, if neither
+			 * if set, using a fallback.
+			 *
+			 * If the initial date is also an EXDATE, it shouldn't be included
+			 * in the count.
+			 *
+			 * Syntax:
+			 *   UNTIL={enddate}
+			 *   COUNT=<positive integer>
+			 *
+			 * Where:
+			 *   enddate = <icalDate> || <icalDateTime>
+			 */
+			$count = 1;
+			$countLimit = (isset($rrules['COUNT'])) ? intval($rrules['COUNT']) : 0;
+			$until = date_create()->modify("{$this->defaultSpan} years")->setTime(23, 59, 59)->getTimestamp();
+
+			if (isset($rrules['UNTIL'])) {
+				$until = min($until, $this->iCalDateToUnixTimestamp($rrules['UNTIL']));
+			}
+			$until = min($until, $this->windowMaxTimestamp);
+
+			$eventRecurrences = array();
+
+			$frequencyRecurringDateTime = clone $initialEventDate;
+			while ($frequencyRecurringDateTime->getTimestamp() <= $until) {
+				$candidateDateTimes = array();
+
+				// phpcs:ignore Squiz.ControlStructures.SwitchDeclaration.MissingDefault
+				switch ($frequency) {
+				case 'DAILY':
+					$candidateDateTimes[] = clone $frequencyRecurringDateTime;
+
+					break;
+
+				case 'WEEKLY':
+					$initialDayOfWeek = $frequencyRecurringDateTime->format('N');
+					$matchingDays = array($initialDayOfWeek);
+
+					if (!empty($rrules['BYDAY'])) {
+						// setISODate() below uses the ISO-8601 specification of weeks: start on
+						// a Monday, end on a Sunday. However, RRULEs (or the caller of the
+						// parser) may state an alternate WeeKSTart.
+						$wkstTransition = 7;
+
+						if (empty($rrules['WKST'])) {
+							if ($this->defaultWeekStart !== self::ISO_8601_WEEK_START) {
+								$wkstTransition = array_search($this->defaultWeekStart, array_keys($this->weekdays));
+							}
+						} elseif ($rrules['WKST'] !== self::ISO_8601_WEEK_START) {
+							$wkstTransition = array_search($rrules['WKST'], array_keys($this->weekdays));
+						}
+
+						$matchingDays = array_map(
+							function ($weekday) use ($initialDayOfWeek, $wkstTransition, $interval) {
+								$day = array_search($weekday, array_keys($this->weekdays));
+
+								if ($day < $initialDayOfWeek) {
+									$day += 7;
+								}
+
+								if ($day >= $wkstTransition) {
+									$day += 7 * ($interval - 1);
+								}
+
+								// Ignoring alternate week starts, $day at this point will have a
+								// value between 0 and 6. But setISODate() expects a value of 1 to 7.
+								// Even with alternate week starts, we still need to +1 to set the
+								// correct weekday.
+								$day++;
+
+								return $day;
+							},
+							$rrules['BYDAY']
+						);
+					}
+
+					sort($matchingDays);
+
+					foreach ($matchingDays as $day) {
+						$clonedDateTime = clone $frequencyRecurringDateTime;
+						$candidateDateTimes[] = $clonedDateTime->setISODate(
+							$frequencyRecurringDateTime->format('o'),
+							$frequencyRecurringDateTime->format('W'),
+							$day
+						);
+					}
+					break;
+
+				case 'MONTHLY':
+					$matchingDays = array();
+
+					if (!empty($rrules['BYMONTHDAY'])) {
+						$matchingDays = $rrules['BYMONTHDAY'];
+					} elseif (!empty($rrules['BYDAY'])) {
+						$matchingDays = $this->getDaysOfMonthMatchingByDayRRule($rrules['BYDAY'], $frequencyRecurringDateTime);
+					}
+
+					if (!empty($rrules['BYSETPOS'])) {
+						$matchingDays = $this->filterValuesUsingBySetPosRRule($rrules['BYSETPOS'], $matchingDays);
+					}
+
+					foreach ($matchingDays as $day) {
+						// Skip invalid dates (e.g. 30th February)
+						if ($day > $frequencyRecurringDateTime->format('t')) {
+							continue;
+						}
+
+						$clonedDateTime = clone $frequencyRecurringDateTime;
+						$candidateDateTimes[] = $clonedDateTime->setDate(
+							$frequencyRecurringDateTime->format('Y'),
+							$frequencyRecurringDateTime->format('m'),
+							$day
+						);
+					}
+					break;
+
+				case 'YEARLY':
+					if (!empty($rrules['BYMONTH'])) {
+						foreach ($rrules['BYMONTH'] as $byMonth) {
+							$clonedDateTime = clone $frequencyRecurringDateTime;
+							$bymonthRecurringDatetime = $clonedDateTime->setDate(
+								$frequencyRecurringDateTime->format('Y'),
+								$byMonth,
+								$frequencyRecurringDateTime->format('d')
+							);
+
+							if (!empty($rrules['BYDAY'])) {
+								// Get all days of the month that match the BYDAY rule.
+								$matchingDays = $this->getDaysOfMonthMatchingByDayRRule($rrules['BYDAY'], $bymonthRecurringDatetime);
+
+								// And add each of them to the list of recurrences
+								foreach ($matchingDays as $day) {
+									$clonedDateTime = clone $bymonthRecurringDatetime;
+									$candidateDateTimes[] = $clonedDateTime->setDate(
+										$frequencyRecurringDateTime->format('Y'),
+										$bymonthRecurringDatetime->format('m'),
+										$day
+									);
+								}
+							} else {
+								$candidateDateTimes[] = clone $bymonthRecurringDatetime;
+							}
+						}
+					} else {
+						$candidateDateTimes[] = clone $frequencyRecurringDateTime;
+					}
+					break;
+				}
+
+				foreach ($candidateDateTimes as $candidate) {
+					$timestamp = $candidate->getTimestamp();
+					if ($timestamp <= $initialEventDate->getTimestamp()) {
+						continue;
+					}
+
+					if ($timestamp > $until) {
+						break;
+					}
+
+					// Exclusions
+					$isExcluded = ($this->shouldFilterByWindow && $timestamp + 160000 < $this->windowMinTimestamp);
+
+					if (!$isExcluded) {
+						$isExcluded = array_filter($exdates, function ($exdate) use ($timestamp) {
+							return $exdate->getTimestamp() == $timestamp;
+						});
+					}
+
+					if (!$isExcluded && isset($this->alteredRecurrenceInstances[$anEvent['UID']])) {
+						if (in_array($timestamp, $this->alteredRecurrenceInstances[$anEvent['UID']])) {
+							$isExcluded = true;
+						}
+					}
+
+					if (!$isExcluded) {
+						$eventRecurrences[] = $candidate;
+						$this->eventCount++;
+					}
+
+					// Count all evaluated candidates including excluded ones
+					if (isset($rrules['COUNT'])) {
+						$count++;
+
+						// If RRULE[COUNT] is reached then break
+						if ($count >= $countLimit) {
+							break 2;
+						}
+					}
+				}
+
+				// Move forwards $interval $frequency.
+				$monthPreMove = $frequencyRecurringDateTime->format('m');
+				$frequencyRecurringDateTime->modify("{$interval} {$this->frequencyConversion[$frequency]}");
+
+				// As noted in Example #2 on https://www.php.net/manual/en/datetime.modify.php,
+				// there are some occasions where adding months doesn't give the month you might
+				// expect. For instance: January 31st + 1 month == March 3rd (March 2nd on a leap
+				// year.) The following code crudely rectifies this.
+				if ($frequency === 'MONTHLY') {
+					$monthDiff = $frequencyRecurringDateTime->format('m') - $monthPreMove;
+
+					if (($monthDiff > 0 && $monthDiff > $interval) || ($monthDiff < 0 && $monthDiff > $interval - 12)) {
+						$frequencyRecurringDateTime->modify('-1 month');
+					}
+				}
+			}
+
+			// Determine event length
+			$eventLength = 0;
+			if (isset($anEvent['DURATION'])) {
+				$clonedDateTime = clone $initialEventDate;
+				$endDate = $clonedDateTime->add($anEvent['DURATION_array'][2]);
+				$eventLength = $endDate->getTimestamp() - $anEvent['DTSTART_array'][2];
+			} elseif (isset($anEvent['DTEND_array'])) {
+				$eventLength = $anEvent['DTEND_array'][2] - $anEvent['DTSTART_array'][2];
+			}
+
+			// Whether or not the initial date was UTC
+			$initialDateWasUTC = substr($anEvent['DTSTART'], -1) === 'Z';
+
+			// Build the param array
+			$dateParamArray = array();
+			if (
+				!$initialDateWasUTC
+				&& isset($anEvent['DTSTART_array'][0]['TZID'])
+				&& $this->isValidTimeZoneId($anEvent['DTSTART_array'][0]['TZID'])
+			) {
+				$dateParamArray['TZID'] = $anEvent['DTSTART_array'][0]['TZID'];
+			}
+
+			// Populate the `DT{START|END}[_array]`s
+			$eventRecurrences = array_map(
+				function ($recurringDatetime) use ($anEvent, $eventLength, $initialDateWasUTC, $dateParamArray) {
+					$tzidPrefix = (isset($dateParamArray['TZID'])) ? 'TZID=' . $this->escapeParamText($dateParamArray['TZID']) . ':' : '';
+
+					foreach (array('DTSTART', 'DTEND') as $dtkey) {
+						$anEvent[$dtkey] = $recurringDatetime->format(self::DATE_TIME_FORMAT) . (($initialDateWasUTC) ? 'Z' : '');
+
+						$anEvent["{$dtkey}_array"] = array(
+							$dateParamArray,                    // [0] Array of params (incl. TZID)
+							$anEvent[$dtkey],                   // [1] ICalDateTime string w/o TZID
+							$recurringDatetime->getTimestamp(), // [2] Unix Timestamp
+							"{$tzidPrefix}{$anEvent[$dtkey]}",  // [3] Full ICalDateTime string
+						);
+
+						if ($dtkey !== 'DTEND') {
+							$recurringDatetime->modify("{$eventLength} seconds");
+						}
+					}
+
+					return $anEvent;
+				},
+				$eventRecurrences
+			);
+
+			$allEventRecurrences = array_merge($allEventRecurrences, $eventRecurrences);
+		}
+
+		// Nullify the initial events that are also EXDATEs
+		foreach ($eventKeysToRemove as $eventKeyToRemove) {
+			$events[$eventKeyToRemove] = null;
+		}
+
+		$events = array_merge($events, $allEventRecurrences);
+	}
+
+	/**
+	 * Find all days of a month that match the BYDAY stanza of an RRULE.
+	 *
+	 * With no {ordwk}, then return the day number of every {weekday}
+	 * within the month.
+	 *
+	 * With a +ve {ordwk}, then return the {ordwk} {weekday} within the
+	 * month.
+	 *
+	 * With a -ve {ordwk}, then return the {ordwk}-to-last {weekday}
+	 * within the month.
+	 *
+	 * RRule Syntax:
+	 *   BYDAY={bywdaylist}
+	 *
+	 * Where:
+	 *   bywdaylist = {weekdaynum}[,{weekdaynum}...]
+	 *   weekdaynum = [[+]{ordwk} || -{ordwk}]{weekday}
+	 *   ordwk      = 1 to 53
+	 *   weekday    = SU || MO || TU || WE || TH || FR || SA
+	 *
+	 * @param array $byDays
+	 * @param DateTime $initialDateTime
+	 * @return array
+	 */
+	protected function getDaysOfMonthMatchingByDayRRule(array $byDays, $initialDateTime)
+	{
+		$matchingDays = array();
+
+		foreach ($byDays as $weekday) {
+			$bydayDateTime = clone $initialDateTime;
+
+			$ordwk = intval(substr($weekday, 0, -2));
+
+			// Quantise the date to the first instance of the requested day in a month
+			// (Or last if we have a -ve {ordwk})
+			$bydayDateTime->modify(
+				(($ordwk < 0) ? 'Last' : 'First')
+				. ' '
+				. $this->weekdays[substr($weekday, -2)]  // e.g. "Monday"
+				. ' of ' . $initialDateTime->format('F') // e.g. "June"
+			);
+
+			if ($ordwk < 0) { // -ve {ordwk}
+				$bydayDateTime->modify((++$ordwk) . ' week');
+				$matchingDays[] = $bydayDateTime->format('j');
+			} elseif ($ordwk > 0) { // +ve {ordwk}
+				$bydayDateTime->modify((--$ordwk) . ' week');
+				$matchingDays[] = $bydayDateTime->format('j');
+			} else { // No {ordwk}
+				while ($bydayDateTime->format('n') === $initialDateTime->format('n')) {
+					$matchingDays[] = $bydayDateTime->format('j');
+					$bydayDateTime->modify('+1 week');
+				}
+			}
+		}
+
+		// Sort into ascending order.
+		sort($matchingDays);
+
+		return $matchingDays;
+	}
+
+	/**
+	 * Filters a provided values-list by applying a BYSETPOS RRule.
+	 *
+	 * Where a +ve {daynum} is provided, the {ordday} position'd value as
+	 * measured from the start of the list of values should be retained.
+	 *
+	 * Where a -ve {daynum} is provided, the {ordday} position'd value as
+	 * measured from the end of the list of values should be retained.
+	 *
+	 * RRule Syntax:
+	 *   BYSETPOS={bysplist}
+	 *
+	 * Where:
+	 *   bysplist  = {setposday}[,{setposday}...]
+	 *   setposday = {daynum}
+	 *   daynum    = [+ || -] {ordday}
+	 *   ordday    = 1 to 366
+	 *
+	 * @param array $bySetPos
+	 * @param array $valuesList
+	 * @return array
+	 */
+	protected function filterValuesUsingBySetPosRRule(array $bySetPos, array $valuesList)
+	{
+		$filteredMatches = array();
+
+		foreach ($bySetPos as $setPosition) {
+			if ($setPosition < 0) {
+				$setPosition = count($valuesList) + ++$setPosition;
+			}
+
+			// Positioning starts at 1, array indexes start at 0
+			if (isset($valuesList[$setPosition - 1])) {
+				$filteredMatches[] = $valuesList[$setPosition - 1];
+			}
+		}
+
+		return $filteredMatches;
+	}
+
+	/**
+	 * Processes date conversions using the time zone
+	 *
+	 * Add keys `DTSTART_tz` and `DTEND_tz` to each Event
+	 * These keys contain dates adapted to the calendar
+	 * time zone depending on the event `TZID`.
+	 *
+	 * @return void
+	 */
+	protected function processDateConversions()
+	{
+		if (empty($this->cal['VEVENT']))
+			return;
+
+		$events =& $this->cal['VEVENT'];
+		foreach ($events as $key => $anEvent) {
+			if (is_null($anEvent) || !$this->isValidDate($anEvent['DTSTART'])) {
+				unset($events[$key]);
+				$this->eventCount--;
+
+				continue;
+			}
+
+			$events[$key]['DTSTART_tz'] = $this->iCalDateWithTimeZone($anEvent, 'DTSTART');
+
+			if ($this->iCalDateWithTimeZone($anEvent, 'DTEND')) {
+				$events[$key]['DTEND_tz'] = $this->iCalDateWithTimeZone($anEvent, 'DTEND');
+			} elseif ($this->iCalDateWithTimeZone($anEvent, 'DURATION')) {
+				$events[$key]['DTEND_tz'] = $this->iCalDateWithTimeZone($anEvent, 'DURATION');
+			} else {
+				$events[$key]['DTEND_tz'] = $events[$key]['DTSTART_tz'];
+			}
+		}
+	}
+
+	/**
+	 * Returns an array of Events.
+	 * Every event is a class with the event
+	 * details being properties within it.
+	 *
+	 * @return ICalEvent[]
+	 */
+	public function events()
+	{
+		if (empty($this->cal) || empty($this->cal['VEVENT']))
+			return [];
+
+		$events = array();
+		foreach ($this->cal['VEVENT'] as $event) {
+			$events[] = new ICalEvent($event);
+		}
+
+		return $events;
+	}
+
+	/**
+	 * Returns the calendar name
+	 *
+	 * @return string
+	 */
+	public function calendarName()
+	{
+		return isset($this->cal['VCALENDAR']['X-WR-CALNAME']) ? $this->cal['VCALENDAR']['X-WR-CALNAME'] : '';
+	}
+
+	/**
+	 * Returns the calendar description
+	 *
+	 * @return string
+	 */
+	public function calendarDescription()
+	{
+		return isset($this->cal['VCALENDAR']['X-WR-CALDESC']) ? $this->cal['VCALENDAR']['X-WR-CALDESC'] : '';
+	}
+
+	/**
+	 * Returns the calendar time zone
+	 *
+	 * @param boolean $ignoreUtc
+	 * @return string
+	 */
+	public function calendarTimeZone($ignoreUtc = false)
+	{
+		if (isset($this->cal['VCALENDAR']['X-WR-TIMEZONE'])) {
+			$timeZone = $this->cal['VCALENDAR']['X-WR-TIMEZONE'];
+		} elseif (isset($this->cal['VTIMEZONE']['TZID'])) {
+			$timeZone = $this->cal['VTIMEZONE']['TZID'];
+		} else {
+			$timeZone = $this->defaultTimeZone;
+		}
+
+		// Validate the time zone, falling back to the time zone set in the PHP environment.
+		$timeZone = $this->timeZoneStringToDateTimeZone($timeZone)->getName();
+
+		if ($ignoreUtc && strtoupper($timeZone) === self::TIME_ZONE_UTC) {
+			return null;
+		}
+
+		return $timeZone;
+	}
+
+	/**
+	 * Returns an array of arrays with all free/busy events.
+	 * Every event is an associative array and each property
+	 * is an element it.
+	 *
+	 * @return array
+	 */
+	public function freeBusyEvents()
+	{
+		$array = $this->cal;
+
+		return isset($array['VFREEBUSY']) ? $array['VFREEBUSY'] : array();
+	}
+
+	/**
+	 * Returns a sorted array of the events in a given range,
+	 * or an empty array if no events exist in the range.
+	 *
+	 * Events will be returned if the start or end date is contained within the
+	 * range (inclusive), or if the event starts before and end after the range.
+	 *
+	 * If a start date is not specified or of a valid format, then the start
+	 * of the range will default to the current time and date of the server.
+	 *
+	 * If an end date is not specified or of a valid format, then the end of
+	 * the range will default to the current time and date of the server,
+	 * plus 20 years.
+	 *
+	 * Note that this function makes use of Unix timestamps. This might be a
+	 * problem for events on, during, or after 29 Jan 2038.
+	 * See https://en.wikipedia.org/wiki/Unix_time#Representing_the_number
+	 *
+	 * @param string|null $rangeStart
+	 * @param string|null $rangeEnd
+	 * @return array
+	 * @throws Exception
+	 */
+	public function eventsFromRange($rangeStart = null, $rangeEnd = null)
+	{
+		// Sort events before processing range
+		$events = $this->sortEventsWithOrder($this->events());
+
+		if (empty($events)) {
+			return array();
+		}
+
+		$extendedEvents = array();
+
+		if (!is_null($rangeStart)) {
+			try {
+				$rangeStart = new DateTime($rangeStart, new DateTimeZone($this->defaultTimeZone));
+			} catch (Exception $exception) {
+				error_log("ICal::eventsFromRange: Invalid date passed ({$rangeStart})");
+				$rangeStart = false;
+			}
+		} else {
+			$rangeStart = new DateTime('now', new DateTimeZone($this->defaultTimeZone));
+		}
+
+		if (!is_null($rangeEnd)) {
+			try {
+				$rangeEnd = new DateTime($rangeEnd, new DateTimeZone($this->defaultTimeZone));
+			} catch (Exception $exception) {
+				error_log("ICal::eventsFromRange: Invalid date passed ({$rangeEnd})");
+				$rangeEnd = false;
+			}
+		} else {
+			$rangeEnd = new DateTime('now', new DateTimeZone($this->defaultTimeZone));
+			$rangeEnd->modify('+20 years');
+		}
+
+		// If start and end are identical and are dates with no times...
+		if ($rangeEnd->format('His') == 0 && $rangeStart->getTimestamp() === $rangeEnd->getTimestamp()) {
+			$rangeEnd->modify('+1 day');
+		}
+
+		$rangeStart = $rangeStart->getTimestamp();
+		$rangeEnd = $rangeEnd->getTimestamp();
+
+		foreach ($events as $anEvent) {
+			$eventStart = $anEvent->dtstart_array[2];
+			$eventEnd = (isset($anEvent->dtend_array[2])) ? $anEvent->dtend_array[2] : null;
+
+			if (
+				($eventStart >= $rangeStart && $eventStart < $rangeEnd)         // Event start date contained in the range
+				|| ($eventEnd !== null
+					&& (
+						($eventEnd > $rangeStart && $eventEnd <= $rangeEnd)     // Event end date contained in the range
+						|| ($eventStart < $rangeStart && $eventEnd > $rangeEnd) // Event starts before and finishes after range
+					)
+				)
+			) {
+				$extendedEvents[] = $anEvent;
+			}
+		}
+
+		if (empty($extendedEvents)) {
+			return array();
+		}
+
+		return $extendedEvents;
+	}
+
+	/**
+	 * Sorts events based on a given sort order
+	 *
+	 * @param array $events
+	 * @param integer $sortOrder Either SORT_ASC, SORT_DESC, SORT_REGULAR, SORT_NUMERIC, SORT_STRING
+	 * @return array
+	 */
+	public function sortEventsWithOrder(array $events, $sortOrder = SORT_ASC)
+	{
+		$extendedEvents = array();
+		$timestamp = array();
+
+		foreach ($events as $key => $anEvent) {
+			$extendedEvents[] = $anEvent;
+			$timestamp[$key] = $anEvent->dtstart_array[2];
+		}
+
+		array_multisort($timestamp, $sortOrder, $extendedEvents);
+
+		return $extendedEvents;
+	}
+
+	/**
+	 * Checks if a time zone is valid (IANA, CLDR, or Windows)
+	 *
+	 * @param string $timeZone
+	 * @return boolean
+	 */
+	protected function isValidTimeZoneId($timeZone)
+	{
+		return $this->isValidIanaTimeZoneId($timeZone) !== false
+			|| $this->isValidCldrTimeZoneId($timeZone) !== false
+			|| $this->isValidWindowsTimeZoneId($timeZone) !== false;
+	}
+
+	/**
+	 * Checks if a time zone is a valid IANA time zone
+	 *
+	 * @param string $timeZone
+	 * @return boolean
+	 */
+	protected function isValidIanaTimeZoneId($timeZone)
+	{
+		if (in_array($timeZone, $this->validIanaTimeZones)) {
+			return true;
+		}
+
+		$valid = array();
+		$tza = timezone_abbreviations_list();
+
+		foreach ($tza as $zone) {
+			foreach ($zone as $item) {
+				$valid[$item['timezone_id']] = true;
+			}
+		}
+
+		unset($valid['']);
+
+		if (isset($valid[$timeZone]) || in_array($timeZone, timezone_identifiers_list(DateTimeZone::ALL_WITH_BC))) {
+			$this->validIanaTimeZones[] = $timeZone;
+
+			return true;
+		}
+
+		return false;
+	}
+
+	/**
+	 * Checks if a time zone is a valid CLDR time zone
+	 *
+	 * @param string $timeZone
+	 * @return boolean
+	 */
+	public function isValidCldrTimeZoneId($timeZone)
+	{
+		return array_key_exists(html_entity_decode($timeZone), self::$cldrTimeZonesMap);
+	}
+
+	/**
+	 * Checks if a time zone is a recognised Windows (non-CLDR) time zone
+	 *
+	 * @param string $timeZone
+	 * @return boolean
+	 */
+	public function isValidWindowsTimeZoneId($timeZone)
+	{
+		return array_key_exists(html_entity_decode($timeZone), self::$windowsTimeZonesMap);
+	}
+
+	/**
+	 * Parses a duration and applies it to a date
+	 *
+	 * @param string $date
+	 * @param DateInterval $duration
+	 * @param string $format
+	 * @return integer|DateTime
+	 */
+	protected function parseDuration($date, $duration, $format = self::UNIX_FORMAT)
+	{
+		$dateTime = date_create($date);
+		$dateTime->modify("{$duration->y} year");
+		$dateTime->modify("{$duration->m} month");
+		$dateTime->modify("{$duration->d} day");
+		$dateTime->modify("{$duration->h} hour");
+		$dateTime->modify("{$duration->i} minute");
+		$dateTime->modify("{$duration->s} second");
+
+		if (is_null($format)) {
+			$output = $dateTime;
+		} elseif ($format === self::UNIX_FORMAT) {
+			$output = $dateTime->getTimestamp();
+		} else {
+			$output = $dateTime->format($format);
+		}
+
+		return $output;
+	}
+
+	/**
+	 * Removes unprintable ASCII and UTF-8 characters
+	 *
+	 * @param string $data
+	 * @return string
+	 */
+	protected function removeUnprintableChars($data)
+	{
+		return preg_replace('/[\x00-\x1F\x7F\xA0]/u', '', $data);
+	}
+
+	/**
+	 * Places double-quotes around texts that have characters not permitted
+	 * in parameter-texts, but are permitted in quoted-texts.
+	 *
+	 * @param string $candidateText
+	 * @return string
+	 */
+	protected function escapeParamText($candidateText)
+	{
+		if (strpbrk($candidateText, ':;,') !== false) {
+			return '"' . $candidateText . '"';
+		}
+
+		return $candidateText;
+	}
+
+	/**
+	 * Parses a list of excluded dates
+	 * to be applied to an Event
+	 *
+	 * @param array $event
+	 * @return array
+	 */
+	public function parseExdates(array $event)
+	{
+		if (empty($event['EXDATE_array'])) {
+			return array();
+		} else {
+			$exdates = $event['EXDATE_array'];
+		}
+
+		$output = array();
+		$currentTimeZone = $this->defaultTimeZone;
+
+		foreach ($exdates as $subArray) {
+			end($subArray);
+			$finalKey = key($subArray);
+
+			foreach (array_keys($subArray) as $key) {
+				if ($key === 'TZID') {
+					$currentTimeZone = $this->timeZoneStringToDateTimeZone($subArray[$key]);
+				} elseif (is_numeric($key)) {
+					$icalDate = $subArray[$key];
+
+					if (substr($icalDate, -1) === 'Z') {
+						$currentTimeZone = self::TIME_ZONE_UTC;
+					}
+
+					$output[] = new DateTimeImmutable($icalDate, $currentTimeZone);
+
+					if ($key === $finalKey) {
+						// Reset to default
+						$currentTimeZone = $this->defaultTimeZone;
+					}
+				}
+			}
+		}
+
+		return $output;
+	}
+
+	/**
+	 * Checks if a date string is a valid date
+	 *
+	 * @param string $value
+	 * @return boolean
+	 */
+	public function isValidDate($value)
+	{
+		if (!$value) {
+			return false;
+		}
+
+		try {
+			new DateTime($value);
+
+			return true;
+		} catch (Exception $exception) {
+			return false;
+		}
+	}
+
+	/**
+	 * Returns a `DateTimeZone` object based on a string containing a time zone name.
+	 * Falls back to the default time zone if string passed not a recognised time zone.
+	 *
+	 * @param string $timeZoneString
+	 * @return DateTimeZone
+	 */
+	public function timeZoneStringToDateTimeZone($timeZoneString)
+	{
+		// Some time zones contain characters that are not permitted in param-texts,
+		// but are within quoted texts. We need to remove the quotes as they're not
+		// actually part of the time zone.
+		$timeZoneString = trim($timeZoneString, '"');
+		$timeZoneString = html_entity_decode($timeZoneString);
+
+		if ($this->isValidIanaTimeZoneId($timeZoneString)) {
+			return new DateTimeZone($timeZoneString);
+		}
+
+		if ($this->isValidCldrTimeZoneId($timeZoneString)) {
+			return new DateTimeZone(self::$cldrTimeZonesMap[$timeZoneString]);
+		}
+
+		if ($this->isValidWindowsTimeZoneId($timeZoneString)) {
+			return new DateTimeZone(self::$windowsTimeZonesMap[$timeZoneString]);
+		}
+
+		return new DateTimeZone($this->defaultTimeZone);
+	}
+}
diff --git a/modules-available/locationinfo/lang/de/backend-hisinone.json b/modules-available/locationinfo/lang/de/backend-hisinone.json
index 6ea1a933..5a2ad69f 100644
--- a/modules-available/locationinfo/lang/de/backend-hisinone.json
+++ b/modules-available/locationinfo/lang/de/backend-hisinone.json
@@ -1,14 +1,6 @@
 {
     "baseUrl": "Basis-URL",
-    "baseUrl_helptext": "URL zur HisInOne-Installation",
-    "open": "Service",
-    "open_helptext": "Legt den zu verwendenden Web Service fest. OpenCourseService bietet anonymisierte Belegungspl\u00e4ne und erfordert keine Authentifizierung und ist i.d.R. bevorzugt.",
-    "password": "Passwort",
-    "password_helptext": "Das Passwort, das in HisInOne verwendet wird.",
-    "role": "Rolle",
-    "role_helptext": "Die Rolle die der Nutzername in HisInOne verwendet.",
-    "username": "Nutzername",
-    "username_helptext": "Der Nutzername, der in HisInOne verwendet wird.",
+    "baseUrl_helptext": "URL zur HisInOne-Installation, bzw. die URL, um einen Raumbelegungsplan als iCal-Datei herunterzuladen, z.B. \"https:\/\/<hisinoneserver>\/qisserver\/pages\/cm\/exa\/timetable\/roomScheduleCalendarExport.faces?roomId=\"",
     "verifyCert": "Zertifikat pr\u00fcfen",
     "verifyCert_helptext": "Wenn das Zertifikat abgelaufen ist, oder von keiner bekannten CA ausgestellt wurde, wird die Verbindung abgelehnt.",
     "verifyHostname": "Hostnamen pr\u00fcfen",
diff --git a/modules-available/locationinfo/lang/en/backend-hisinone.json b/modules-available/locationinfo/lang/en/backend-hisinone.json
index 616b4c83..ee44a62e 100644
--- a/modules-available/locationinfo/lang/en/backend-hisinone.json
+++ b/modules-available/locationinfo/lang/en/backend-hisinone.json
@@ -1,16 +1,8 @@
 {
     "baseUrl": "Base URL",
-    "baseUrl_helptext": "URL to HisInOne installation",
-    "open": "Service",
-    "open_helptext": "Sets the Web Service to use. OpenCourseService is anonymized and doesn't require authentication, so it's usually the preferred way.",
-    "password": "Password",
-    "password_helptext": "Account password. Only required if using CourseService",
-    "role": "Role",
-    "role_helptext": "Role of the user accessing the CourseService.",
-    "username": "Username",
-    "username_helptext": "Authenticating user (only required for CourseService).",
+    "baseUrl_helptext": "URL to HisInOne installation, or more precisely the URL to download a room's events as an iCal file, usually something like \"https:\/\/<hisinoneserver>\/qisserver\/pages\/cm\/exa\/timetable\/roomScheduleCalendarExport.faces?roomId=\"",
     "verifyCert": "Verify certificate",
     "verifyCert_helptext": "If the certificate expired or was not signed by a known CA, the connection will be aborted.",
     "verifyHostname": "Verify host name",
     "verifyHostname_helptext": "The certificate's host name must match the host name given in the URL, otherwise the connection will be aborted."
-}
+}
\ No newline at end of file
diff --git a/modules-available/locationinfo/page.inc.php b/modules-available/locationinfo/page.inc.php
index 0885f446..e6269857 100644
--- a/modules-available/locationinfo/page.inc.php
+++ b/modules-available/locationinfo/page.inc.php
@@ -752,8 +752,9 @@ class Page_LocationInfo extends Page
 			);
 			$backend['credentials'] = $backendInstance->getCredentialDefinitions();
 			foreach ($backend['credentials'] as $cred) {
+				/* @var BackendProperty $cred */
 				if ($backend['active'] && isset($oldCredentials[$cred->property])) {
-					$cred->initForRender($oldCredentials[$cred->property]);
+					$cred->initForRender($backendInstance->mangleProperty($cred->property, $oldCredentials[$cred->property]));
 				} else {
 					$cred->initForRender();
 				}