<?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() {
    $this->sqlite =& plugin_load('helper', 'sqlite');
    global $conf;
    dbglog('---- DAVCAL helper.php init');
    if(!$this->sqlite)
    {
        dbglog('This plugin requires the sqlite plugin. Please install it.');
        msg('This plugin requires the sqlite plugin. Please install it.');
        return;
    }
    
    if(!$this->sqlite->init('davcal', DOKU_PLUGIN.'davcal/db/'))
    {
        dbglog('Error initialising the SQLite DB for DAVCal');
        return;
    }
  }
  
  /**
   * 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($page, 'webdav://') === 0)
      {
          $wdc =& plugin_load('helper', 'webdavclient');
          if(is_null($wdc))
            return AUTH_NONE;
          $connectionId = str_replace('webdav://', '', $page);
          $settings = $wdc->getConnection($connectionId);
          if($settings === false)
            return AUTH_NONE;
          if($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)
          {
              $retList[$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;
      
      $query = "UPDATE calendars SET calendarcolor = ? ".
               " WHERE id = ?";
      $res = $this->sqlite->query($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);
      
      $query = "UPDATE calendars SET displayname = ?, description = ? WHERE id = ?";
      $res = $this->sqlite->query($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)
  {
      $query = "UPDATE calendars SET displayname = ? WHERE id = ?";
      $res = $this->sqlite->query($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)
  {
      $query = "UPDATE calendars SET description = ? WHERE id = ?";
      $res = $this->sqlite->query($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)
  {
      $query = "UPDATE calendars SET timezone = ? WHERE id = ?";
      $res = $this->sqlite->query($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;
          }
      }
      $this->sqlite->query("BEGIN TRANSACTION");
      
      $query = "DELETE FROM calendarsettings WHERE userid = ?";
      $this->sqlite->query($query, $userid);
      
      foreach($settings as $key => $value)
      {
          $query = "INSERT INTO calendarsettings (userid, key, value) VALUES (?, ?, ?)";
          $res = $this->sqlite->query($query, $userid, $key, $value);
          if($res === false)
              return false;
      }
      $this->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;
          }
      }

      if(isset($this->cachedValues['settings'][$userid]))
        return $this->cachedValues['settings'][$userid];
      $query = "SELECT key, value FROM calendarsettings WHERE userid = ?";
      $res = $this->sqlite->query($query, $userid);
      $arr = $this->sqlite->res2arr($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];
      
      $query = "SELECT calid FROM pagetocalendarmapping WHERE page = ?";
      $res = $this->sqlite->query($query, $id);
      $row = $this->sqlite->res2row($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()
  {
      $query = "SELECT calid, page FROM pagetocalendarmapping";
      $res = $this->sqlite->query($query);
      $arr = $this->sqlite->res2arr($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'];
          $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);
      $query = "INSERT INTO calendars (principaluri, displayname, uri, description, components, transparent, synctoken) ".
               "VALUES (?, ?, ?, ?, ?, ?, ?)";
      $res = $this->sqlite->query($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 = $this->sqlite->query($query, $values[0], $values[1], $values[2], $values[3]);
      $row = $this->sqlite->res2row($res);
      
      // Update the pagetocalendarmapping table with the new calendar ID
      if(isset($row['id']))
      {
          $query = "INSERT INTO pagetocalendarmapping (page, calid) VALUES (?, ?)";
          $res = $this->sqlite->query($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);

    $query = "INSERT INTO calendarobjects (calendarid, uri, calendardata, lastmodified, etag, size, componenttype, firstoccurence, lastoccurence, uid) VALUES (?,?,?,?,?,?,?,?,?,?)";
    $res = $this->sqlite->query($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);

      $query = "UPDATE calendarobjects SET calendardata = ?, lastmodified = ?, etag = ?, size = ?, componenttype = ?, firstoccurence = ?, lastoccurence = ?, uid = ? WHERE calendarid = ? AND uri = ?";
      $res = $this->sqlite->query($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 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 = uniqid('dokuwiki-').'.ics';
          $now = new \DateTime();
          
          $query = "INSERT INTO calendarobjects (calendarid, uri, calendardata, lastmodified, componenttype, firstoccurence, lastoccurence, size, etag, uid) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";
          $res = $this->sqlite->query($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)
  {
      $query = "SELECT id, principaluri, calendarcolor, displayname, uri, description, components, transparent, synctoken FROM calendars WHERE id= ? ";
      $res = $this->sqlite->query($query, $calid);
      $row = $this->sqlite->res2row($res);
      return $row;
  }

  /**
   * 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();
      
      $query = "SELECT calendardata, componenttype, uid FROM calendarobjects WHERE calendarid = ?";
      $startTs = null;
      $endTs = null;
      if($startDate !== null)
      {
        $startTs = new \DateTime($startDate);
        $query .= " AND lastoccurence > ".$this->sqlite->quote_string($startTs->getTimestamp());
      }
      if($endDate !== null)
      {
        $endTs = new \DateTime($endDate);
        $query .= " AND firstoccurence < ".$this->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);
    
          // Retrieve matching calendar objects
          $res = $this->sqlite->query($query, $calid);
          $arr = $this->sqlite->res2arr($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['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)
  {
      $query = "SELECT calendardata, calendarid, componenttype, uri FROM calendarobjects WHERE uid = ?";
      $res = $this->sqlite->query($query, $uid);
      $row = $this->sqlite->res2row($res);
      return $row;
  }
  
  /**
   * Retrieve information of a calendar's object, not including the actual
   * calendar data! This is mainly neede for the sync support.
   * 
   * @param int $calid The calendar ID
   * 
   * @return mixed The result
   */
  public function getCalendarObjects($calid)
  {
      $query = "SELECT id, uri, lastmodified, etag, calendarid, size, componenttype FROM calendarobjects WHERE calendarid = ?";
      $res = $this->sqlite->query($query, $calid);
      $arr = $this->sqlite->res2arr($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)
  {
      $query = "SELECT id, uri, lastmodified, etag, calendarid, size, calendardata, componenttype FROM calendarobjects WHERE calendarid = ? AND uri = ?";
      $res = $this->sqlite->query($query, $calid, $uri);
      $row = $this->sqlite->res2row($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)
  {
        $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 = $this->sqlite->query($query, $vals);
        $arr = $this->sqlite->res2arr($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)
  {
      $query = "SELECT calendardata, uid, componenttype, uri FROM calendarobjects WHERE calendarid = ?";
      $res = $this->sqlite->query($query, $calid);
      $arr = $this->sqlite->res2arr($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'];
      
      // Remove existing timestamps to overwrite them
      $vevent->remove('DESCRIPTION');      
      $vevent->remove('DTSTAMP');
      $vevent->remove('LAST-MODIFIED');
      $vevent->remove('ATTACH');
      
      // Add new time stamps and description
      $vevent->add('DTSTAMP', $dtStamp);
      $vevent->add('LAST-MODIFIED', $dtStamp);
      if($description !== '')
        $vevent->add('DESCRIPTION', $description);

      // 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
      {
          $now = new DateTime();
          // Actually write to the database
          $query = "UPDATE calendarobjects SET calendardata = ?, lastmodified = ?, ".
                   "firstoccurence = ?, lastoccurence = ?, size = ?, etag = ? WHERE uid = ?";
          $res = $this->sqlite->query($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)
  {
      $query = "DELETE FROM calendarobjects WHERE calendarid = ? AND uri = ?";
      $res = $this->sqlite->query($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;
      }
      $event = $this->getEventWithUid($uid);
      $calid = $event['calendarid'];
      $uri = $event['uri'];
      $query = "DELETE FROM calendarobjects WHERE uid = ?";
      $res = $this->sqlite->query($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
      );
      $query = "INSERT INTO calendarchanges (uri, synctoken, calendarid, operation) VALUES(?, ?, ?, ?)";
      $res = $this->sqlite->query($query, $uri, $currentToken, $calid, $operationCode);
      if($res === false)
        return false;
      $currentToken++;
      $query = "UPDATE calendars SET synctoken = ? WHERE id = ?";
      $res = $this->sqlite->query($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];
      $query = "SELECT url FROM calendartoprivateurlmapping WHERE calid = ?";
      $res = $this->sqlite->query($query, $calid);
      $row = $this->sqlite->res2row($res);
      if(!isset($row['url']))
      {
          $url = uniqid("dokuwiki-").".ics";
          $query = "INSERT INTO calendartoprivateurlmapping (url, calid) VALUES(?, ?)";
          $res = $this->sqlite->query($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)
  {
      $query = "SELECT calid FROM calendartoprivateurlmapping WHERE url = ?";
      $res = $this->sqlite->query($query, $url);
      $row = $this->sqlite->res2row($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;

    // 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();
    }

    dbglog($query);
    $res = $this->sqlite->query($query, $values);
    $arr = $this->sqlite->res2arr($res);
    dbglog($arr);

    $result = array();
    foreach($arr as $row)
    {
        if ($requirePostFilter) 
        {
            dbglog('requirePostFilter for');
            dbglog($row);
            dbglog($filters);
            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'])) 
      {
          dbglog('fetching object...');
          $object = $this->getCalendarObjectByUri($object['calendarid'], $object['uri']);
      }
      
      dbglog('object to validate: ');
      dbglog($object);
      $vObject = \Sabre\VObject\Reader::read($object['calendardata']);
      $validator = new \Sabre\CalDAV\CalendarQueryValidator();
      
      $res = $validator->validate($vObject, $filters);
      dbglog($res);
      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(),
      );

      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 = $this->sqlite->query($query, $syncToken, $currentToken, $calid);
          if($res === false)
              return null;

          $arr = $this->sqlite->res2arr($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 = $this->sqlite->query($query);
          $arr = $this->sqlite->res2arr($res);

          $result['added'] = $arr;
      }
      return $result;
  }

}