diff --git a/helper.php b/helper.php
--- a/helper.php
+++ b/helper.php
@@ -1,1944 +1,1949 @@
 <?php
 /** 
   * Helper Class for the DAVCal plugin
   * This helper does the actual work.
   * 
   */
   
 // must be run within Dokuwiki
 if(!defined('DOKU_INC')) die();
 
 class helper_plugin_davcal extends DokuWiki_Plugin {
   
   protected $sqlite = null;
   protected $cachedValues = array();
   
   /**
     * Constructor to load the configuration and the SQLite plugin
     */
   public function helper_plugin_davcal() {
     dbglog('---- DAVCAL helper.php init');
   }
   
   /** Establish and initialize the database if not already done
    * @return sqlite interface or false
    */
   private function getDB()
   {
       if($this->sqlite === null)
       {
         $this->sqlite = plugin_load('helper', 'sqlite');
         if(!$this->sqlite)
         {
             dbglog('This plugin requires the sqlite plugin. Please install it.');
             msg('This plugin requires the sqlite plugin. Please install it.', -1);
             return false;
         }
         if(!$this->sqlite->init('davcal', DOKU_PLUGIN.'davcal/db/'))
         {
             $this->sqlite = null;
             dbglog('Error initialising the SQLite DB for DAVCal');
             return false;
         }
       }
       return $this->sqlite;
   }
   
   /**
    * Retrieve meta data for a given page
    * 
    * @param string $id optional The page ID
    * @return array The metadata
    */
   private function getMeta($id = null) {
     global $ID;
     global $INFO;
 
     if ($id === null) $id = $ID;
 
     if($ID === $id && $INFO['meta']) {
         $meta = $INFO['meta'];
     } else {
         $meta = p_get_metadata($id);
     }
     
     return $meta;
   }
   
   /**
    * Retrieve the meta data for a given page
    * 
    * @param string $id optional The page ID
    * @return array with meta data
    */
   public function getCalendarMetaForPage($id = null)
   {
       if(is_null($id))
       {
           global $ID;
           $id = $ID;
       }
       
       $meta = $this->getMeta($id);
       if(isset($meta['plugin_davcal']))
         return $meta['plugin_davcal'];
       else
         return array();
   }
   
   /**
    * Check the permission of a user for a given calendar ID
    * 
    * @param string $id The calendar ID to check
    * @return int AUTH_* constants
    */
   public function checkCalendarPermission($id)
   {
       if(strpos($id, 'webdav://') === 0)
       {
           $wdc =& plugin_load('helper', 'webdavclient');
           if(is_null($wdc))
             return AUTH_NONE;
           $connectionId = str_replace('webdav://', '', $id);
           $settings = $wdc->getConnection($connectionId);
           if($settings === false)
             return AUTH_NONE;
+          // Check if webdavclient has permissions attached to a page
+          if(!empty($settings['permission']))
+          {
+            $perm = auth_quickaclcheck($settings['permission']);
+            // In case the page has more than read permission, but the
+            // calendar is read-only, we need to modify the permission here.
+            if($perm > AUTH_READ && $settings['write'] == 0)
+              $perm = AUTH_READ;
+            return $perm;
+          }
           if($settings['write'] === '1')
             return AUTH_CREATE;
           return AUTH_READ;
       }
       else
       {
           $calid = $this->getCalendarIdForPage($id);
           // We return AUTH_READ if the calendar does not exist. This makes
           // davcal happy when there are just included calendars
           if($calid === false)
             return AUTH_READ;
           return auth_quickaclcheck($id);
       }
   }
   
   /**
    * Filter calendar pages and return only those where the current
    * user has at least read permission.
    * 
    * @param array $calendarPages Array with calendar pages to check
    * @return array with filtered calendar pages
    */
   public function filterCalendarPagesByUserPermission($calendarPages)
   {
       $retList = array();
       foreach($calendarPages as $page => $data)
       {
-          // WebDAV Connections are always readable
-          if(strpos($page, 'webdav://') === 0)
-          {
-              $retList[$page] = $data;
-          }
-          elseif(auth_quickaclcheck($page) >= AUTH_READ)
+          if($this->checkCalendarPermission($page) >= AUTH_READ)
           {
               $retList[$page] = $data;
           }
       }
       return $retList;
   }
   
   /**
    * Get all calendar pages used by a given page
    * based on the stored metadata
    * 
    * @param string $id optional The page id
    * @return mixed The pages as array or false
    */
   public function getCalendarPagesByMeta($id = null)
   {
       if(is_null($id))
       {
           global $ID;
           $id = $ID;
       }
       
       $meta = $this->getCalendarMetaForPage($id);
 
       if(isset($meta['id']))
       {
           // Filter the list of pages by permission
           $pages = $this->filterCalendarPagesByUserPermission($meta['id']);
           if(empty($pages))
             return false;
           return $pages;
       }
       return false;
   }
   
   /**
    * Get a list of calendar names/pages/ids/colors
    * for an array of page ids
    * 
    * @param array $calendarPages The calendar pages to retrieve
    * @return array The list
    */
   public function getCalendarMapForIDs($calendarPages)
   {
       $data = array();
       foreach($calendarPages as $page => $color)
       {
             if(strpos($page, 'webdav://') === 0)
             {
                 $wdc =& plugin_load('helper', 'webdavclient');
                 if(is_null($wdc))
                     continue;
                 $connectionId = str_replace('webdav://', '', $page);
                 $settings = $wdc->getConnection($connectionId);
                 if($settings === false)
                     continue;
                 $name = $settings['displayname'];
                 $write = ($settings['write'] === '1');
                 $calid = $connectionId;
                 $color = '#3a87ad';
             }
             else
             {
                 $calid = $this->getCalendarIdForPage($page);
                 if($calid !== false)
                 {
                     $settings = $this->getCalendarSettings($calid);
                     $name = $settings['displayname'];
                     $color = $settings['calendarcolor'];
                     $write = (auth_quickaclcheck($page) > AUTH_READ);
                 }
                 else
                 {
                     continue;
                 }
             }
             $data[] = array('name' => $name, 'page' => $page, 'calid' => $calid,
                             'color' => $color, 'write' => $write);
       }
       return $data;
   }
   
   /**
    * Get the saved calendar color for a given page.
    * 
    * @param string $id optional The page ID
    * @return mixed The color on success, otherwise false
    */
   public function getCalendarColorForPage($id = null)
   {
       if(is_null($id))
       {
           global $ID;
           $id = $ID;
       }
       
       $calid = $this->getCalendarIdForPage($id);
       if($calid === false)
         return false;
       
       return $this->getCalendarColorForCalendar($calid);
   }
   
   /**
    * Get the saved calendar color for a given calendar ID.
    * 
    * @param string $id optional The calendar ID
    * @return mixed The color on success, otherwise false
    */
   public function getCalendarColorForCalendar($calid)
   {
       if(isset($this->cachedValues['calendarcolor'][$calid]))
         return $this->cachedValues['calendarcolor'][$calid];
 
       $row = $this->getCalendarSettings($calid);
 
       if(!isset($row['calendarcolor']))
         return false;
       
       $color = $row['calendarcolor'];
       $this->cachedValues['calendarcolor'][$calid] = $color;
       return $color;
   }
   
   /**
    * Get the user's principal URL for iOS sync
    * @param string $user the user name
    * @return the URL to the principal sync
    */
   public function getPrincipalUrlForUser($user)
   {
       if(is_null($user))
         return false;
       $url = DOKU_URL.'lib/plugins/davcal/calendarserver.php/principals/'.$user;
       return $url;
   }
   
   /**
    * Set the calendar color for a given page.
    * 
    * @param string $color The color definition
    * @param string $id optional The page ID
    * @return boolean True on success, otherwise false
    */
   public function setCalendarColorForPage($color, $id = null)
   {
       if(is_null($id))
       {
           global $ID;
           $id = $ID;
       }
       $calid = $this->getCalendarIdForPage($id);
       if($calid === false)
         return false;
       
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "UPDATE calendars SET calendarcolor = ? ".
                " WHERE id = ?";
       $res = $sqlite->query($query, $color, $calid);
       if($res !== false)
       {
         $this->cachedValues['calendarcolor'][$calid] = $color;
         return true;
       }
       return false;
   }
   
   /**
    * Set the calendar name and description for a given page with a given
    * page id.
    * If the calendar doesn't exist, the calendar is created!
    * 
    * @param string  $name The name of the new calendar
    * @param string  $description The description of the new calendar
    * @param string  $id (optional) The ID of the page
    * @param string  $userid The userid of the creating user
    * 
    * @return boolean True on success, otherwise false.
    */
   public function setCalendarNameForPage($name, $description, $id = null, $userid = null)
   {
       if(is_null($id))
       {
           global $ID;
           $id = $ID;
       }
       if(is_null($userid))
       {
         if(isset($_SERVER['REMOTE_USER']) && !is_null($_SERVER['REMOTE_USER']))
         {
           $userid = $_SERVER['REMOTE_USER'];
         }
         else
         {
           $userid = uniqid('davcal-');
         }
       }
       $calid = $this->getCalendarIdForPage($id);
       if($calid === false)
         return $this->createCalendarForPage($name, $description, $id, $userid);
       
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "UPDATE calendars SET displayname = ?, description = ? WHERE id = ?";
       $res = $sqlite->query($query, $name, $description, $calid);
       if($res !== false)
         return true;
       return false;
   }
   
   /**
    * Update a calendar's displayname
    * 
    * @param int $calid The calendar's ID
    * @param string $name The new calendar name
    * 
    * @return boolean True on success, otherwise false
    */
   public function updateCalendarName($calid, $name)
   {
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "UPDATE calendars SET displayname = ? WHERE id = ?";
       $res = $sqlite->query($query, $calid, $name);
       if($res !== false)
       {
         $this->updateSyncTokenLog($calid, '', 'modified');
         return true;
       }
       return false;
   }
   
   /**
    * Update the calendar description
    * 
    * @param int $calid The calendar's ID
    * @param string $description The new calendar's description
    * 
    * @return boolean True on success, otherwise false
    */
   public function updateCalendarDescription($calid, $description)
   {
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "UPDATE calendars SET description = ? WHERE id = ?";
       $res = $sqlite->query($query, $calid, $description);
       if($res !== false)
       {
         $this->updateSyncTokenLog($calid, '', 'modified');
         return true;
       }
       return false;
   }
   
   /**
    * Update a calendar's timezone information
    * 
    * @param int $calid The calendar's ID
    * @param string $timezone The new timezone to set
    * 
    * @return boolean True on success, otherwise false
    */
   public function updateCalendarTimezone($calid, $timezone)
   {
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "UPDATE calendars SET timezone = ? WHERE id = ?";
       $res = $sqlite->query($query, $calid, $timezone);
       if($res !== false)
       {
         $this->updateSyncTokenLog($calid, '', 'modified');
         return true;
       }
       return false;
   }
   
   /**
    * Save the personal settings to the SQLite database 'calendarsettings'.
    * 
    * @param array  $settings The settings array to store
    * @param string $userid (optional) The userid to store
    * 
    * @param boolean True on success, otherwise false
    */
   public function savePersonalSettings($settings, $userid = null)
   {
       if(is_null($userid))
       {
           if(isset($_SERVER['REMOTE_USER']) && !is_null($_SERVER['REMOTE_USER']))
           {
             $userid = $_SERVER['REMOTE_USER'];
           }
           else 
           {
               return false;
           }
       }
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $sqlite->query("BEGIN TRANSACTION");
       
       $query = "DELETE FROM calendarsettings WHERE userid = ?";
       $sqlite->query($query, $userid);
       
       foreach($settings as $key => $value)
       {
           $query = "INSERT INTO calendarsettings (userid, key, value) VALUES (?, ?, ?)";
           $res = $sqlite->query($query, $userid, $key, $value);
           if($res === false)
               return false;
       }
       $sqlite->query("COMMIT TRANSACTION");
       $this->cachedValues['settings'][$userid] = $settings;
       return true;
   }
   
   /**
    * Retrieve the settings array for a given user id. 
    * Some sane defaults are returned, currently:
    * 
    *    timezone    => local
    *    weeknumbers => 0
    *    workweek    => 0
    * 
    * @param string $userid (optional) The user id to retrieve
    * 
    * @return array The settings array
    */
   public function getPersonalSettings($userid = null)
   {
       // Some sane default settings
       $settings = array(
         'timezone' => $this->getConf('timezone'),
         'weeknumbers' => $this->getConf('weeknumbers'),
         'workweek' => $this->getConf('workweek'),
         'monday' => $this->getConf('monday'),
         'timeformat' => $this->getConf('timeformat')
       );
       if(is_null($userid))
       {
           if(isset($_SERVER['REMOTE_USER']) && !is_null($_SERVER['REMOTE_USER']))
           {
             $userid = $_SERVER['REMOTE_USER'];
           }
           else 
           {
             return $settings;
           }
       }
 
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       if(isset($this->cachedValues['settings'][$userid]))
         return $this->cachedValues['settings'][$userid];
       $query = "SELECT key, value FROM calendarsettings WHERE userid = ?";
       $res = $sqlite->query($query, $userid);
       $arr = $sqlite->res2arr($res);
       foreach($arr as $row)
       {
           $settings[$row['key']] = $row['value'];
       }
       $this->cachedValues['settings'][$userid] = $settings;
       return $settings;
   }
   
   /**
    * Retrieve the calendar ID based on a page ID from the SQLite table
    * 'pagetocalendarmapping'. 
    * 
    * @param string $id (optional) The page ID to retrieve the corresponding calendar
    * 
    * @return mixed the ID on success, otherwise false
    */
   public function getCalendarIdForPage($id = null)
   {
       if(is_null($id))
       {
           global $ID;
           $id = $ID;
       }
       
       if(isset($this->cachedValues['calid'][$id]))
         return $this->cachedValues['calid'][$id];
       
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "SELECT calid FROM pagetocalendarmapping WHERE page = ?";
       $res = $sqlite->query($query, $id);
       $row = $sqlite->res2row($res);
       if(isset($row['calid']))
       {
         $calid = $row['calid'];
         $this->cachedValues['calid'] = $calid;
         return $calid;
       }
       return false;
   }
   
   /**
    * Retrieve the complete calendar id to page mapping.
    * This is necessary to be able to retrieve a list of
    * calendars for a given user and check the access rights.
    * 
    * @return array The mapping array
    */
   public function getCalendarIdToPageMapping()
   {
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "SELECT calid, page FROM pagetocalendarmapping";
       $res = $sqlite->query($query);
       $arr = $sqlite->res2arr($res);
       return $arr;
   }
   
   /**
    * Retrieve all calendar IDs a given user has access to.
    * The user is specified by the principalUri, so the
    * user name is actually split from the URI component.
    * 
    * Access rights are checked against DokuWiki's ACL
    * and applied accordingly.
    * 
    * @param string $principalUri The principal URI to work on
    * 
    * @return array An associative array of calendar IDs
    */
   public function getCalendarIdsForUser($principalUri)
   {
       global $auth;
       $user = explode('/', $principalUri);
       $user = end($user);
       $mapping = $this->getCalendarIdToPageMapping();
       $calids = array();
       $ud = $auth->getUserData($user);
       $groups = $ud['grps'];      
       foreach($mapping as $row)
       {
           $id = $row['calid'];
           $enabled = $this->getCalendarStatus($id);
           if($enabled == false)
             continue;
           $page = $row['page'];
           $acl = auth_aclcheck($page, $user, $groups);
           if($acl >= AUTH_READ)
           {
               $write = $acl > AUTH_READ;
               $calids[$id] = array('readonly' => !$write);
           }
       }
       return $calids;
   }
   
   /**
    * Create a new calendar for a given page ID and set name and description
    * accordingly. Also update the pagetocalendarmapping table on success.
    * 
    * @param string $name The calendar's name
    * @param string $description The calendar's description
    * @param string $id (optional) The page ID to work on
    * @param string $userid (optional) The user ID that created the calendar
    * 
    * @return boolean True on success, otherwise false
    */
   public function createCalendarForPage($name, $description, $id = null, $userid = null)
   {
       if(is_null($id))
       {
           global $ID;
           $id = $ID;
       }
       if(is_null($userid))
       {
         if(isset($_SERVER['REMOTE_USER']) && !is_null($_SERVER['REMOTE_USER']))
         {
           $userid = $_SERVER['REMOTE_USER'];
         }
         else
         {
           $userid = uniqid('davcal-');
         }
       }
       $values = array('principals/'.$userid, 
                       $name,
                       str_replace(array('/', ' ', ':'), '_', $id), 
                       $description,
                       'VEVENT,VTODO',
                       0,
                       1);
 
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "INSERT INTO calendars (principaluri, displayname, uri, description, components, transparent, synctoken) ".
                "VALUES (?, ?, ?, ?, ?, ?, ?)";
       $res = $sqlite->query($query, $values[0], $values[1], $values[2], $values[3], $values[4], $values[5], $values[6]);
       if($res === false)
         return false;
       
       // Get the new calendar ID
       $query = "SELECT id FROM calendars WHERE principaluri = ? AND displayname = ? AND ".
                "uri = ? AND description = ?";
       $res = $sqlite->query($query, $values[0], $values[1], $values[2], $values[3]);
       $row = $sqlite->res2row($res);
       
       // Update the pagetocalendarmapping table with the new calendar ID
       if(isset($row['id']))
       {
           $query = "INSERT INTO pagetocalendarmapping (page, calid) VALUES (?, ?)";
           $res = $sqlite->query($query, $id, $row['id']);
           return ($res !== false);
       }
       
       return false;
   }
 
   /**
    * Add a new calendar entry to the given calendar. Calendar data is
    * specified as ICS file, thus it needs to be parsed first.
    * 
    * This is mainly needed for the sync support.
    * 
    * @param int $calid The calendar's ID
    * @param string $uri The new object URI
    * @param string $ics The ICS file
    * 
    * @return mixed The etag.
    */
   public function addCalendarEntryToCalendarByICS($calid, $uri, $ics)
   {
     $extraData = $this->getDenormalizedData($ics);
 
     $sqlite = $this->getDB();
     if(!$sqlite)
       return false;
     $query = "INSERT INTO calendarobjects (calendarid, uri, calendardata, lastmodified, etag, size, componenttype, firstoccurence, lastoccurence, uid) VALUES (?,?,?,?,?,?,?,?,?,?)";
     $res = $sqlite->query($query, 
             $calid,
             $uri,
             $ics,
             time(),
             $extraData['etag'],
             $extraData['size'],
             $extraData['componentType'],
             $extraData['firstOccurence'],
             $extraData['lastOccurence'],
             $extraData['uid']);
             // If successfully, update the sync token database
     if($res !== false)
     {
         $this->updateSyncTokenLog($calid, $uri, 'added');
     }
     return $extraData['etag'];
   }
   
   /**
    * Edit a calendar entry by providing a new ICS file. This is mainly
    * needed for the sync support.
    * 
    * @param int $calid The calendar's IS
    * @param string $uri The object's URI to modify
    * @param string $ics The new object's ICS file
    */
   public function editCalendarEntryToCalendarByICS($calid, $uri, $ics)
   {
       $extraData = $this->getDenormalizedData($ics);
 
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "UPDATE calendarobjects SET calendardata = ?, lastmodified = ?, etag = ?, size = ?, componenttype = ?, firstoccurence = ?, lastoccurence = ?, uid = ? WHERE calendarid = ? AND uri = ?";
       $res = $sqlite->query($query, 
         $ics,
         time(),
         $extraData['etag'],
         $extraData['size'],
         $extraData['componentType'],
         $extraData['firstOccurence'], 
         $extraData['lastOccurence'], 
         $extraData['uid'], 
         $calid,
         $uri
       );
       if($res !== false)
       {
           $this->updateSyncTokenLog($calid, $uri, 'modified');
       }
       return $extraData['etag'];
   }
 
   /**
    * Add a new iCal entry for a given page, i.e. a given calendar.
    * 
    * The parameter array needs to contain
    *   detectedtz       => The timezone as detected by the browser
    *   currenttz        => The timezone in use by the calendar
    *   eventfrom        => The event's start date
    *   eventfromtime    => The event's start time
    *   eventto          => The event's end date
    *   eventtotime      => The event's end time
    *   eventname        => The event's name
    *   eventdescription => The event's description
    * 
    * @param string $id The page ID to work on
    * @param string $user The user who created the calendar
    * @param string $params A parameter array with values to create
    * 
    * @return boolean True on success, otherwise false
    */
   public function addCalendarEntryToCalendarForPage($id, $user, $params)
   {
       if($params['currenttz'] !== '' && $params['currenttz'] !== 'local')
           $timezone = new \DateTimeZone($params['currenttz']);
       elseif($params['currenttz'] === 'local')
           $timezone = new \DateTimeZone($params['detectedtz']);
       else
           $timezone = new \DateTimeZone('UTC');
       
       // Retrieve dates from settings
       $startDate = explode('-', $params['eventfrom']);
       $startTime = explode(':', $params['eventfromtime']);
       $endDate = explode('-', $params['eventto']);
       $endTime = explode(':', $params['eventtotime']);
       
       // Load SabreDAV
       require_once(DOKU_PLUGIN.'davcal/vendor/autoload.php');
       $vcalendar = new \Sabre\VObject\Component\VCalendar();
       
       // Add VCalendar, UID and Event Name
       $event = $vcalendar->add('VEVENT');
       $uuid = \Sabre\VObject\UUIDUtil::getUUID();
       $event->add('UID', $uuid);
       $event->summary = $params['eventname'];
       
       // Add a description if requested
       $description = $params['eventdescription'];
       if($description !== '')
         $event->add('DESCRIPTION', $description);
       
       // Add a location if requested
       $location = $params['eventlocation'];
       if($location !== '')
         $event->add('LOCATION', $location);
       
       // Add attachments
       $attachments = $params['attachments'];
       if(!is_null($attachments))
         foreach($attachments as $attachment)
           $event->add('ATTACH', $attachment);
       
       // Create a timestamp for last modified, created and dtstamp values in UTC
       $dtStamp = new \DateTime(null, new \DateTimeZone('UTC'));
       $event->add('DTSTAMP', $dtStamp);
       $event->add('CREATED', $dtStamp);
       $event->add('LAST-MODIFIED', $dtStamp);
       
       // Adjust the start date, based on the given timezone information
       $dtStart = new \DateTime();
       $dtStart->setTimezone($timezone);            
       $dtStart->setDate(intval($startDate[0]), intval($startDate[1]), intval($startDate[2]));
       
       // Only add the time values if it's not an allday event
       if($params['allday'] != '1')
         $dtStart->setTime(intval($startTime[0]), intval($startTime[1]), 0);
       
       // Adjust the end date, based on the given timezone information
       $dtEnd = new \DateTime();
       $dtEnd->setTimezone($timezone);      
       $dtEnd->setDate(intval($endDate[0]), intval($endDate[1]), intval($endDate[2]));
       
       // Only add the time values if it's not an allday event
       if($params['allday'] != '1')
         $dtEnd->setTime(intval($endTime[0]), intval($endTime[1]), 0);
       
       // According to the VCal spec, we need to add a whole day here
       if($params['allday'] == '1')
           $dtEnd->add(new \DateInterval('P1D'));
       
       // Really add Start and End events
       $dtStartEv = $event->add('DTSTART', $dtStart);
       $dtEndEv = $event->add('DTEND', $dtEnd);
       
       // Adjust the DATE format for allday events
       if($params['allday'] == '1')
       {
           $dtStartEv['VALUE'] = 'DATE';
           $dtEndEv['VALUE'] = 'DATE';
       }
       
       $eventStr = $vcalendar->serialize();
       
       if(strpos($id, 'webdav://') === 0)
       {
           $wdc =& plugin_load('helper', 'webdavclient');
           if(is_null($wdc))
             return false;
           $connectionId = str_replace('webdav://', '', $id);
           return $wdc->addCalendarEntry($connectionId, $eventStr);
       }
       else 
       {
           // Actually add the values to the database
           $calid = $this->getCalendarIdForPage($id);
           $uri = $uri = 'dokuwiki-' . bin2hex(random_bytes(16)) . '.ics';
           $now = new \DateTime();
           
           $sqlite = $this->getDB();
           if(!$sqlite)
             return false;
           $query = "INSERT INTO calendarobjects (calendarid, uri, calendardata, lastmodified, componenttype, firstoccurence, lastoccurence, size, etag, uid) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";
           $res = $sqlite->query($query, $calid, $uri, $eventStr, $now->getTimestamp(), 'VEVENT',
                                       $event->DTSTART->getDateTime()->getTimeStamp(), $event->DTEND->getDateTime()->getTimeStamp(),
                                       strlen($eventStr), md5($eventStr), $uuid);
           
           // If successfully, update the sync token database
           if($res !== false)
           {
               $this->updateSyncTokenLog($calid, $uri, 'added');
               return true;
           }
       }
       return false;
   }
 
   /**
    * Retrieve the calendar settings of a given calendar id
    * 
    * @param string $calid The calendar ID
    * 
    * @return array The calendar settings array
    */
   public function getCalendarSettings($calid)
   {
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "SELECT id, principaluri, calendarcolor, displayname, uri, description, components, transparent, synctoken, disabled FROM calendars WHERE id= ? ";
       $res = $sqlite->query($query, $calid);
       $row = $sqlite->res2row($res);
       return $row;
   }
   
   /**
    * Retrieve the calendar status of a given calendar id
    * 
    * @param string $calid The calendar ID
    * @return boolean True if calendar is enabled, otherwise false
    */
   public function getCalendarStatus($calid)
   {
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "SELECT disabled FROM calendars WHERE id = ?";
       $res = $sqlite->query($query, $calid);
       $row = $sqlite->res2row($res);
       if($row['disabled'] == 1)
         return false;
       else
         return true;
   }
   
   /**
    * Disable a calendar for a given page
    * 
    * @param string $id The page ID
    * 
    * @return boolean true on success, otherwise false
    */
   public function disableCalendarForPage($id)
   {
       $calid = $this->getCalendarIdForPage($id);
       if($calid === false)
         return false;
 
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "UPDATE calendars SET disabled = 1 WHERE id = ?";
       $res = $sqlite->query($query, $calid);
       if($res !== false)
         return true;
       return false;
   }
   
   /**
    * Enable a calendar for a given page
    * 
    * @param string $id The page ID
    * 
    * @return boolean true on success, otherwise false
    */
   public function enableCalendarForPage($id)
   {
       $calid = $this->getCalendarIdForPage($id);
       if($calid === false)
         return false;
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "UPDATE calendars SET disabled = 0 WHERE id = ?";
       $res = $sqlite->query($query, $calid);
       if($res !== false)
         return true;
       return false;
   }
 
   /**
    * Retrieve all events that are within a given date range,
    * based on the timezone setting.
    * 
    * There is also support for retrieving recurring events,
    * using Sabre's VObject Iterator. Recurring events are represented
    * as individual calendar entries with the same UID.
    * 
    * @param string $id The page ID to work with
    * @param string $user The user ID to work with
    * @param string $startDate The start date as a string
    * @param string $endDate The end date as a string
    * @param string $color (optional) The calendar's color
    * 
    * @return array An array containing the calendar entries.
    */
   public function getEventsWithinDateRange($id, $user, $startDate, $endDate, $timezone, $color = null)
   {
       if($timezone !== '' && $timezone !== 'local')
           $timezone = new \DateTimeZone($timezone);
       else
           $timezone = new \DateTimeZone('UTC');
       $data = array();
 
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
 
       $query = "SELECT calendardata, componenttype, uid FROM calendarobjects WHERE calendarid = ?";
       $startTs = null;
       $endTs = null;
       if($startDate !== null)
       {
         $startTs = new \DateTime($startDate);
         $query .= " AND lastoccurence > ".$sqlite->quote_string($startTs->getTimestamp());
       }
       if($endDate !== null)
       {
         $endTs = new \DateTime($endDate);
         $query .= " AND firstoccurence < ".$sqlite->quote_string($endTs->getTimestamp());
       }
       
       // Load SabreDAV
       require_once(DOKU_PLUGIN.'davcal/vendor/autoload.php');
       
       if(strpos($id, 'webdav://') === 0)
       {
           $wdc =& plugin_load('helper', 'webdavclient');
           if(is_null($wdc))
             return $data;
           $connectionId = str_replace('webdav://', '', $id);
           $arr = $wdc->getCalendarEntries($connectionId, $startDate, $endDate);
       }
       else
       {
           $calid = $this->getCalendarIdForPage($id);
           if(is_null($color))
             $color = $this->getCalendarColorForCalendar($calid);
             
           $enabled = $this->getCalendarStatus($calid);
           if($enabled === false)
             return $data;
     
           // Retrieve matching calendar objects
           $res = $sqlite->query($query, $calid);
           $arr = $sqlite->res2arr($res);
       }
       
       // Parse individual calendar entries
       foreach($arr as $row)
       {
           if(isset($row['calendardata']))
           {
               $entry = array();
               $vcal = \Sabre\VObject\Reader::read($row['calendardata']);
               $recurrence = $vcal->VEVENT->RRULE;
               // If it is a recurring event, pass it through Sabre's EventIterator
               if($recurrence != null)
               {
                   $rEvents = new \Sabre\VObject\Recur\EventIterator(array($vcal->VEVENT));
                   $rEvents->rewind();
                   while($rEvents->valid())
                   {
                       $event = $rEvents->getEventObject();
                       // If we are after the given time range, exit
                       if(($endTs !== null) && ($rEvents->getDtStart()->getTimestamp() > $endTs->getTimestamp()))
                           break;
                         
                       // If we are before the given time range, continue
                       if(($startTs != null) && ($rEvents->getDtEnd()->getTimestamp() < $startTs->getTimestamp()))
                       {
                           $rEvents->next();
                           continue;
                       }
                       
                       // If we are within the given time range, parse the event
                       $data[] = $this->convertIcalDataToEntry($event, $id, $timezone, $row['uid'], $color, true);
                       $rEvents->next();
                   }
               }
               else
                 $data[] = $this->convertIcalDataToEntry($vcal->VEVENT, $id, $timezone, $row['uid'], $color);
           }
       }
       return $data;
   }
 
   /**
    * Helper function that parses the iCal data of a VEVENT to a calendar entry.
    * 
    * @param \Sabre\VObject\VEvent $event The event to parse
    * @param \DateTimeZone $timezone The timezone object
    * @param string $uid The entry's UID
    * @param boolean $recurring (optional) Set to true to define a recurring event
    * 
    * @return array The parse calendar entry
    */
   private function convertIcalDataToEntry($event, $page, $timezone, $uid, $color, $recurring = false)
   {
       $entry = array();
       $start = $event->DTSTART;
       // Parse only if the start date/time is present
       if($start !== null)
       {
         $dtStart = $start->getDateTime();
         $dtStart->setTimezone($timezone);
         
         // moment.js doesn't like times be given even if 
         // allDay is set to true
         // This should fix T23
         if($start['VALUE'] == 'DATE')
         {
           $entry['allDay'] = true;
           $entry['start'] = $dtStart->format("Y-m-d");
         }
         else
         {
           $entry['allDay'] = false;
           $entry['start'] = $dtStart->format(\DateTime::ATOM);
         }
       }
       $end = $event->DTEND;
       // Parse only if the end date/time is present
       if($end !== null)
       {
         $dtEnd = $end->getDateTime();
         $dtEnd->setTimezone($timezone);
         if($end['VALUE'] == 'DATE')
           $entry['end'] = $dtEnd->format("Y-m-d");
         else 
           $entry['end'] = $dtEnd->format(\DateTime::ATOM);
       }
       $description = $event->DESCRIPTION;
       if($description !== null)
         $entry['description'] = (string)$description;
       else
         $entry['description'] = '';
       $attachments = $event->ATTACH;
       if($attachments !== null)
       {
         $entry['attachments'] = array();
         foreach($attachments as $attachment)
           $entry['attachments'][] = (string)$attachment;
       }
       $entry['title'] = (string)$event->summary;
       $entry['location'] = (string)$event->location;
       $entry['id'] = $uid;
       $entry['page'] = $page;
       $entry['color'] = $color;
       $entry['recurring'] = $recurring;
       
       return $entry;
   }
   
   /**
    * Retrieve an event by its UID
    * 
    * @param string $uid The event's UID
    * 
    * @return mixed The table row with the given event
    */
   public function getEventWithUid($uid)
   {
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "SELECT calendardata, calendarid, componenttype, uri FROM calendarobjects WHERE uid = ?";
       $res = $sqlite->query($query, $uid);
       $row = $sqlite->res2row($res);
       return $row;
   }
   
   /**
    * Retrieve information of a calendar's object, not including the actual
    * calendar data! This is mainly needed for the sync support.
    * 
    * @param int $calid The calendar ID
    * 
    * @return mixed The result
    */
   public function getCalendarObjects($calid)
   {
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "SELECT id, uri, lastmodified, etag, calendarid, size, componenttype FROM calendarobjects WHERE calendarid = ?";
       $res = $sqlite->query($query, $calid);
       $arr = $sqlite->res2arr($res);
       return $arr; 
   }
   
   /**
    * Retrieve a single calendar object by calendar ID and URI
    * 
    * @param int $calid The calendar's ID
    * @param string $uri The object's URI
    * 
    * @return mixed The result
    */
   public function getCalendarObjectByUri($calid, $uri)
   {
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "SELECT id, uri, lastmodified, etag, calendarid, size, calendardata, componenttype FROM calendarobjects WHERE calendarid = ? AND uri = ?";
       $res = $sqlite->query($query, $calid, $uri);
       $row = $sqlite->res2row($res);
       return $row;
   }
   
   /**
    * Retrieve several calendar objects by specifying an array of URIs.
    * This is mainly neede for sync.
    * 
    * @param int $calid The calendar's ID
    * @param array $uris An array of URIs
    * 
    * @return mixed The result
    */
   public function getMultipleCalendarObjectsByUri($calid, $uris)
   {
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "SELECT id, uri, lastmodified, etag, calendarid, size, calendardata, componenttype FROM calendarobjects WHERE calendarid = ? AND uri IN (";
       // Inserting a whole bunch of question marks
       $query .= implode(',', array_fill(0, count($uris), '?'));
       $query .= ')';
       $vals = array_merge(array($calid), $uris);
         
       $res = $sqlite->query($query, $vals);
       $arr = $sqlite->res2arr($res);
       return $arr;
   }
   
   /**
    * Retrieve all calendar events for a given calendar ID
    * 
    * @param string $calid The calendar's ID
    * 
    * @return array An array containing all calendar data
    */
   public function getAllCalendarEvents($calid)
   {
       $enabled = $this->getCalendarStatus($calid);
       if($enabled === false)
         return false;
       
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "SELECT calendardata, uid, componenttype, uri FROM calendarobjects WHERE calendarid = ?";
       $res = $sqlite->query($query, $calid);
       $arr = $sqlite->res2arr($res);
       return $arr;
   }
   
   /**
    * Edit a calendar entry for a page, given by its parameters.
    * The params array has the same format as @see addCalendarEntryForPage
    * 
    * @param string $id The page's ID to work on
    * @param string $user The user's ID to work on
    * @param array $params The parameter array for the edited calendar event
    * 
    * @return boolean True on success, otherwise false
    */
   public function editCalendarEntryForPage($id, $user, $params)
   {
       if($params['currenttz'] !== '' && $params['currenttz'] !== 'local')
           $timezone = new \DateTimeZone($params['currenttz']);
       elseif($params['currenttz'] === 'local')
           $timezone = new \DateTimeZone($params['detectedtz']);
       else
           $timezone = new \DateTimeZone('UTC');
           
       // Parse dates
       $startDate = explode('-', $params['eventfrom']);
       $startTime = explode(':', $params['eventfromtime']);
       $endDate = explode('-', $params['eventto']);
       $endTime = explode(':', $params['eventtotime']);
       
       // Retrieve the existing event based on the UID
       $uid = $params['uid'];
       
       if(strpos($id, 'webdav://') === 0)
       {
         $wdc =& plugin_load('helper', 'webdavclient');
         if(is_null($wdc))
           return false;
         $event = $wdc->getCalendarEntryByUid($uid);
       }
       else
       {
         $event = $this->getEventWithUid($uid);
       }
       
       // Load SabreDAV
       require_once(DOKU_PLUGIN.'davcal/vendor/autoload.php');
       if(!isset($event['calendardata']))
         return false;
       $uri = $event['uri'];
       $calid = $event['calendarid'];
       
       // Parse the existing event
       $vcal = \Sabre\VObject\Reader::read($event['calendardata']);
       $vevent = $vcal->VEVENT;
       
       // Set the new event values
       $vevent->summary = $params['eventname'];
       $dtStamp = new \DateTime(null, new \DateTimeZone('UTC'));
       $description = $params['eventdescription'];
       $location = $params['eventlocation'];
       
       // Remove existing timestamps to overwrite them
       $vevent->remove('DESCRIPTION');      
       $vevent->remove('DTSTAMP');
       $vevent->remove('LAST-MODIFIED');
       $vevent->remove('ATTACH');
       $vevent->remove('LOCATION');
       
       // Add new time stamps, description and location
       $vevent->add('DTSTAMP', $dtStamp);
       $vevent->add('LAST-MODIFIED', $dtStamp);
       if($description !== '')
         $vevent->add('DESCRIPTION', $description);
       if($location !== '')
         $vevent->add('LOCATION', $location);
 
       // Add attachments
       $attachments = $params['attachments'];
       if(!is_null($attachments))
         foreach($attachments as $attachment)
           $vevent->add('ATTACH', $attachment);
       
       // Setup DTSTART      
       $dtStart = new \DateTime();
       $dtStart->setTimezone($timezone);      
       $dtStart->setDate(intval($startDate[0]), intval($startDate[1]), intval($startDate[2]));
       if($params['allday'] != '1')
         $dtStart->setTime(intval($startTime[0]), intval($startTime[1]), 0);
       
       // Setup DTEND
       $dtEnd = new \DateTime();
       $dtEnd->setTimezone($timezone);      
       $dtEnd->setDate(intval($endDate[0]), intval($endDate[1]), intval($endDate[2]));
       if($params['allday'] != '1')
         $dtEnd->setTime(intval($endTime[0]), intval($endTime[1]), 0);
       
       // According to the VCal spec, we need to add a whole day here
       if($params['allday'] == '1')
           $dtEnd->add(new \DateInterval('P1D'));
       $vevent->remove('DTSTART');
       $vevent->remove('DTEND');
       $dtStartEv = $vevent->add('DTSTART', $dtStart);
       $dtEndEv = $vevent->add('DTEND', $dtEnd);
       
       // Remove the time for allday events
       if($params['allday'] == '1')
       {
           $dtStartEv['VALUE'] = 'DATE';
           $dtEndEv['VALUE'] = 'DATE';
       }
       $eventStr = $vcal->serialize();
       if(strpos($id, 'webdav://') === 0)
       {
           $connectionId = str_replace('webdav://', '', $id);
           return $wdc->editCalendarEntry($connectionId, $uid, $eventStr);
       }
       else
       {
           $sqlite = $this->getDB();
           if(!$sqlite)
             return false;
           $now = new DateTime();
           // Actually write to the database
           $query = "UPDATE calendarobjects SET calendardata = ?, lastmodified = ?, ".
                    "firstoccurence = ?, lastoccurence = ?, size = ?, etag = ? WHERE uid = ?";
           $res = $sqlite->query($query, $eventStr, $now->getTimestamp(), $dtStart->getTimestamp(),
                                       $dtEnd->getTimestamp(), strlen($eventStr), md5($eventStr), $uid);
           if($res !== false)
           {
               $this->updateSyncTokenLog($calid, $uri, 'modified');
               return true;
           }
       }
       return false;
   }
 
   /**
    * Delete an event from a calendar by calendar ID and URI
    * 
    * @param int $calid The calendar's ID
    * @param string $uri The object's URI
    * 
    * @return true
    */
   public function deleteCalendarEntryForCalendarByUri($calid, $uri)
   {
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "DELETE FROM calendarobjects WHERE calendarid = ? AND uri = ?";
       $res = $sqlite->query($query, $calid, $uri);
       if($res !== false)
       {
           $this->updateSyncTokenLog($calid, $uri, 'deleted');
       }
       return true;      
   }
 
   /**
    * Delete a calendar entry for a given page. Actually, the event is removed
    * based on the entry's UID, so that page ID is no used.
    * 
    * @param string $id The page's ID (unused)
    * @param array $params The parameter array to work with
    * 
    * @return boolean True
    */
   public function deleteCalendarEntryForPage($id, $params)
   {
       $uid = $params['uid'];
       if(strpos($id, 'webdav://') === 0)
       {
         $wdc =& plugin_load('helper', 'webdavclient');
         if(is_null($wdc))
           return false;
         $connectionId = str_replace('webdav://', '', $id);
         $result = $wdc->deleteCalendarEntry($connectionId, $uid);
         return $result;
       }
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $event = $this->getEventWithUid($uid);
       $calid = $event['calendarid'];
       $uri = $event['uri'];
       $query = "DELETE FROM calendarobjects WHERE uid = ?";
       $res = $sqlite->query($query, $uid);
       if($res !== false)
       {
           $this->updateSyncTokenLog($calid, $uri, 'deleted');
       }
       return true;
   }
   
   /**
    * Retrieve the current sync token for a calendar
    * 
    * @param string $calid The calendar id
    * 
    * @return mixed The synctoken or false
    */
   public function getSyncTokenForCalendar($calid)
   {
       $row = $this->getCalendarSettings($calid);
       if(isset($row['synctoken']))
           return $row['synctoken'];
       return false;
   }
   
   /**
    * Helper function to convert the operation name to 
    * an operation code as stored in the database
    * 
    * @param string $operationName The operation name
    * 
    * @return mixed The operation code or false
    */
   public function operationNameToOperation($operationName)
   {
       switch($operationName)
       {
           case 'added':
               return 1;
           break;
           case 'modified':
               return 2;
           break;
           case 'deleted':
               return 3;
           break;
       }
       return false;
   }
   
   /**
    * Update the sync token log based on the calendar id and the 
    * operation that was performed.
    * 
    * @param string $calid The calendar ID that was modified
    * @param string $uri The calendar URI that was modified
    * @param string $operation The operation that was performed
    * 
    * @return boolean True on success, otherwise false
    */
   private function updateSyncTokenLog($calid, $uri, $operation)
   {
       $currentToken = $this->getSyncTokenForCalendar($calid);
       $operationCode = $this->operationNameToOperation($operation);
       if(($operationCode === false) || ($currentToken === false))
           return false;
       $values = array($uri,
                       $currentToken,
                       $calid,
                       $operationCode
       );
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "INSERT INTO calendarchanges (uri, synctoken, calendarid, operation) VALUES(?, ?, ?, ?)";
       $res = $sqlite->query($query, $uri, $currentToken, $calid, $operationCode);
       if($res === false)
         return false;
       $currentToken++;
       $query = "UPDATE calendars SET synctoken = ? WHERE id = ?";
       $res = $sqlite->query($query, $currentToken, $calid);
       return ($res !== false);
   }
   
   /**
    * Return the sync URL for a given Page, i.e. a calendar
    * 
    * @param string $id The page's ID
    * @param string $user (optional) The user's ID
    * 
    * @return mixed The sync url or false
    */
   public function getSyncUrlForPage($id, $user = null)
   {
       if(is_null($userid))
       {
         if(isset($_SERVER['REMOTE_USER']) && !is_null($_SERVER['REMOTE_USER']))
         {
           $userid = $_SERVER['REMOTE_USER'];
         }
         else
         {
           return false;
         }
       }
       
       $calid = $this->getCalendarIdForPage($id);
       if($calid === false)
         return false;
       
       $calsettings = $this->getCalendarSettings($calid);
       if(!isset($calsettings['uri']))
         return false;
       
       $syncurl = DOKU_URL.'lib/plugins/davcal/calendarserver.php/calendars/'.$user.'/'.$calsettings['uri'];
       return $syncurl; 
   }
   
   /**
    * Return the private calendar's URL for a given page
    * 
    * @param string $id the page ID
    * 
    * @return mixed The private URL or false
    */
   public function getPrivateURLForPage($id)
   {
       $calid = $this->getCalendarIdForPage($id);
       if($calid === false)
         return false;
       
       return $this->getPrivateURLForCalendar($calid);
   }
   
   /**
    * Return the private calendar's URL for a given calendar ID
    * 
    * @param string $calid The calendar's ID
    * 
    * @return mixed The private URL or false
    */
   public function getPrivateURLForCalendar($calid)
   {
       if(isset($this->cachedValues['privateurl'][$calid]))
         return $this->cachedValues['privateurl'][$calid];
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "SELECT url FROM calendartoprivateurlmapping WHERE calid = ?";
       $res = $sqlite->query($query, $calid);
       $row = $sqlite->res2row($res);
       if(!isset($row['url']))
       {
           $url = 'dokuwiki-' . bin2hex(random_bytes(16)) . '.ics';
           $query = "INSERT INTO calendartoprivateurlmapping (url, calid) VALUES(?, ?)";
           $res = $sqlite->query($query, $url, $calid);
           if($res === false)
             return false;
       }
       else
       {
           $url = $row['url'];
       }
       
       $url = DOKU_URL.'lib/plugins/davcal/ics.php/'.$url;
       $this->cachedValues['privateurl'][$calid] = $url;
       return $url;
   }
   
   /**
    * Retrieve the calendar ID for a given private calendar URL
    * 
    * @param string $url The private URL
    * 
    * @return mixed The calendar ID or false
    */
   public function getCalendarForPrivateURL($url)
   {
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
       $query = "SELECT calid FROM calendartoprivateurlmapping WHERE url = ?";
       $res = $sqlite->query($query, $url);
       $row = $sqlite->res2row($res);
       if(!isset($row['calid']))
         return false;
       return $row['calid'];
   }
   
   /**
    * Return a given calendar as ICS feed, i.e. all events in one ICS file.
    * 
    * @param string $calid The calendar ID to retrieve
    * 
    * @return mixed The calendar events as string or false
    */
   public function getCalendarAsICSFeed($calid)
   {
       $calSettings = $this->getCalendarSettings($calid);
       if($calSettings === false)
         return false;
       $events = $this->getAllCalendarEvents($calid);
       if($events === false)
         return false;
       
       // Load SabreDAV
       require_once(DOKU_PLUGIN.'davcal/vendor/autoload.php');      
       $out = "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//DAVCal//DAVCal for DokuWiki//EN\r\nCALSCALE:GREGORIAN\r\nX-WR-CALNAME:";
       $out .= $calSettings['displayname']."\r\n";
       foreach($events as $event)
       {
           $vcal = \Sabre\VObject\Reader::read($event['calendardata']);
           $evt = $vcal->VEVENT;
           $out .= $evt->serialize();
       }
       $out .= "END:VCALENDAR\r\n";
       return $out;
   }
   
   /**
    * Retrieve a configuration option for the plugin
    * 
    * @param string $key The key to query
    * @return mixed The option set, null if not found
    */
   public function getConfig($key)
   {
       return $this->getConf($key);
   }
   
   /**
    * Parses some information from calendar objects, used for optimized
    * calendar-queries. Taken nearly unmodified from Sabre's PDO backend
    *
    * Returns an array with the following keys:
    *   * etag - An md5 checksum of the object without the quotes.
    *   * size - Size of the object in bytes
    *   * componentType - VEVENT, VTODO or VJOURNAL
    *   * firstOccurence
    *   * lastOccurence
    *   * uid - value of the UID property
    *
    * @param string $calendarData
    * @return array
    */
   protected function getDenormalizedData($calendarData) 
   {
     require_once(DOKU_PLUGIN.'davcal/vendor/autoload.php');
     
     $vObject = \Sabre\VObject\Reader::read($calendarData);
     $componentType = null;
     $component = null;
     $firstOccurence = null;
     $lastOccurence = null;
     $uid = null;
     foreach ($vObject->getComponents() as $component) 
     {
         if ($component->name !== 'VTIMEZONE') 
         {
             $componentType = $component->name;
             $uid = (string)$component->UID;
             break;
         }
     }
     if (!$componentType) 
     {
         return false;
     }
     if ($componentType === 'VEVENT') 
     {
         $firstOccurence = $component->DTSTART->getDateTime()->getTimeStamp();
         // Finding the last occurence is a bit harder
         if (!isset($component->RRULE)) 
         {
             if (isset($component->DTEND)) 
             {
                 $lastOccurence = $component->DTEND->getDateTime()->getTimeStamp();
             }
             elseif (isset($component->DURATION)) 
             {
                 $endDate = clone $component->DTSTART->getDateTime();
                 $endDate->add(\Sabre\VObject\DateTimeParser::parse($component->DURATION->getValue()));
                 $lastOccurence = $endDate->getTimeStamp();
             } 
             elseif (!$component->DTSTART->hasTime()) 
             {
                 $endDate = clone $component->DTSTART->getDateTime();
                 $endDate->modify('+1 day');
                 $lastOccurence = $endDate->getTimeStamp();
             } 
             else 
             {
                 $lastOccurence = $firstOccurence;
             }
         } 
         else 
         {
             $it = new \Sabre\VObject\Recur\EventIterator($vObject, (string)$component->UID);
             $maxDate = new \DateTime('2038-01-01');
             if ($it->isInfinite()) 
             {
                 $lastOccurence = $maxDate->getTimeStamp();
             } 
             else 
             {
                 $end = $it->getDtEnd();
                 while ($it->valid() && $end < $maxDate) 
                 {
                     $end = $it->getDtEnd();
                     $it->next();
                 }
                 $lastOccurence = $end->getTimeStamp();
             }
         }
     }
 
     return array(
         'etag'           => md5($calendarData),
         'size'           => strlen($calendarData),
         'componentType'  => $componentType,
         'firstOccurence' => $firstOccurence,
         'lastOccurence'  => $lastOccurence,
         'uid'            => $uid,
     );
 
   }
 
   /**
    * Query a calendar by ID and taking several filters into account.
    * This is heavily based on Sabre's PDO backend.
    * 
    * @param int $calendarId The calendar's ID
    * @param array $filters The filter array to apply
    * 
    * @return mixed The result
    */
   public function calendarQuery($calendarId, $filters)
   {
     dbglog('davcal::helper::calendarQuery');
     $componentType = null;
     $requirePostFilter = true;
     $timeRange = null;
     $sqlite = $this->getDB();
     if(!$sqlite)
       return false;
 
     // if no filters were specified, we don't need to filter after a query
     if (!$filters['prop-filters'] && !$filters['comp-filters']) 
     {
         $requirePostFilter = false;
     }
 
     // Figuring out if there's a component filter
     if (count($filters['comp-filters']) > 0 && !$filters['comp-filters'][0]['is-not-defined']) 
     {
         $componentType = $filters['comp-filters'][0]['name'];
 
         // Checking if we need post-filters
         if (!$filters['prop-filters'] && !$filters['comp-filters'][0]['comp-filters'] && !$filters['comp-filters'][0]['time-range'] && !$filters['comp-filters'][0]['prop-filters']) 
         {
             $requirePostFilter = false;
         }
         // There was a time-range filter
         if ($componentType == 'VEVENT' && isset($filters['comp-filters'][0]['time-range'])) 
         {
             $timeRange = $filters['comp-filters'][0]['time-range'];
 
             // If start time OR the end time is not specified, we can do a
             // 100% accurate mysql query.
             if (!$filters['prop-filters'] && !$filters['comp-filters'][0]['comp-filters'] && !$filters['comp-filters'][0]['prop-filters'] && (!$timeRange['start'] || !$timeRange['end'])) 
             {
                 $requirePostFilter = false;
             }
         }
 
     }
 
     if ($requirePostFilter) 
     {
         $query = "SELECT uri, calendardata FROM calendarobjects WHERE calendarid = ?";
     } 
     else 
     {
         $query = "SELECT uri FROM calendarobjects WHERE calendarid = ?";
     }
 
     $values = array(
         $calendarId
     );
 
     if ($componentType) 
     {
         $query .= " AND componenttype = ?";
         $values[] = $componentType;
     }
 
     if ($timeRange && $timeRange['start']) 
     {
         $query .= " AND lastoccurence > ?";
         $values[] = $timeRange['start']->getTimeStamp();
     }
     if ($timeRange && $timeRange['end']) 
     {
         $query .= " AND firstoccurence < ?";
         $values[] = $timeRange['end']->getTimeStamp();
     }
 
     $res = $sqlite->query($query, $values);
     $arr = $sqlite->res2arr($res);
 
     $result = array();
     foreach($arr as $row)
     {
         if ($requirePostFilter) 
         {
             if (!$this->validateFilterForObject($row, $filters))
             {
                 continue;
             }
         }
         $result[] = $row['uri'];
 
     }
 
     return $result;
   }
   
   /**
    * This method validates if a filter (as passed to calendarQuery) matches
    * the given object. Taken from Sabre's PDO backend
    *
    * @param array $object
    * @param array $filters
    * @return bool
    */
   protected function validateFilterForObject($object, $filters) 
   {
       require_once(DOKU_PLUGIN.'davcal/vendor/autoload.php');
       // Unfortunately, setting the 'calendardata' here is optional. If
       // it was excluded, we actually need another call to get this as
       // well.
       if (!isset($object['calendardata'])) 
       {
           $object = $this->getCalendarObjectByUri($object['calendarid'], $object['uri']);
       }
       
       $vObject = \Sabre\VObject\Reader::read($object['calendardata']);
       $validator = new \Sabre\CalDAV\CalendarQueryValidator();
       
       $res = $validator->validate($vObject, $filters);
       return $res;
 
   }
   
   /**
    * Retrieve changes for a given calendar based on the given syncToken.
    * 
    * @param int $calid The calendar's ID
    * @param int $syncToken The supplied sync token
    * @param int $syncLevel The sync level
    * @param int $limit The limit of changes
    * 
    * @return array The result
    */
   public function getChangesForCalendar($calid, $syncToken, $syncLevel, $limit = null)
   {
       // Current synctoken
       $currentToken = $this->getSyncTokenForCalendar($calid);
 
       if ($currentToken === false) return null;
 
       $result = array(
           'syncToken' => $currentToken,
           'added'     => array(),
           'modified'  => array(),
           'deleted'   => array(),
       );
       $sqlite = $this->getDB();
       if(!$sqlite)
         return false;
 
       if ($syncToken) 
       {
 
           $query = "SELECT uri, operation FROM calendarchanges WHERE synctoken >= ? AND synctoken < ? AND calendarid = ? ORDER BY synctoken";
           if ($limit > 0) $query .= " LIMIT " . (int)$limit;
 
           // Fetching all changes
           $res = $sqlite->query($query, $syncToken, $currentToken, $calid);
           if($res === false)
               return null;
 
           $arr = $sqlite->res2arr($res);
           $changes = array();
 
           // This loop ensures that any duplicates are overwritten, only the
           // last change on a node is relevant.
           foreach($arr as $row) 
           {
               $changes[$row['uri']] = $row['operation'];
           }
 
           foreach ($changes as $uri => $operation) 
           {
               switch ($operation) 
               {
                   case 1 :
                       $result['added'][] = $uri;
                       break;
                   case 2 :
                       $result['modified'][] = $uri;
                       break;
                   case 3 :
                       $result['deleted'][] = $uri;
                       break;
               }
 
           }
       }
       else 
       {
           // No synctoken supplied, this is the initial sync.
           $query = "SELECT uri FROM calendarobjects WHERE calendarid = ?";
           $res = $sqlite->query($query);
           $arr = $sqlite->res2arr($res);
 
           $result['added'] = $arr;
       }
       return $result;
   }
 
 }
diff --git a/plugin.info.txt b/plugin.info.txt
--- a/plugin.info.txt
+++ b/plugin.info.txt
@@ -1,7 +1,7 @@
 base	davcal
 author  Andreas Boehler
 email   dev@aboehler.at
-date    2017-11-24
+date    2019-01-21
 name    Calendar PlugIn with CalDAV sharing support
 desc    Create one calendar per page and share/subscribe via CalDAV
 url     http://www.dokuwiki.org/plugin:davcal