<?php

/**
 * Recurrence computation class for xcal-based Kolab format objects
 *
 * Uitility class to compute instances of recurring events.
 *
 * @version @package_version@
 * @author Thomas Bruederli <bruederli@kolabsys.com>
 *
 * Copyright (C) 2012, Kolab Systems AG <contact@kolabsys.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
class kolab_date_recurrence
{
  private $engine;
  private $tz_offset = 0;
  private $allday = false;
  private $hour = 0;

  /**
   * Default constructor
   *
   * @param array The Kolab object to operate on
   */
  function __construct($object)
  {
      // use (copied) Horde classes to compute recurring instances
      // TODO: replace with something that has less than 6'000 lines of code
      $this->engine = new Horde_Date_Recurrence($object['start']);
      $this->engine->fromRRule20($this->to_rrule($object['recurrence']));  // TODO: get that string directly from libkolabxml

      foreach ((array)$object['recurrence']['EXDATE'] as $exdate)
          $this->engine->addException(date('Y', $exdate), date('n', $exdate), date('j', $exdate));

      $now = new DateTime('now', kolab_format::$timezone);
      $this->tz_offset = $object['allday'] ? $now->getOffset() - date('Z') : 0;
      $this->next = new Horde_Date($object['start'] + $this->tz_offset);  # shift all-day times to server timezone because computation operates in local TZ
      $this->dst_start = $this->next->format('I');
      $this->allday = $object['allday'];
      $this->hour = $this->next->hour;
  }

  /**
   * Get timestamp of the next occurence of this event
   *
   * @return mixed Unix timestamp or False if recurrence ended
   */
  public function next_start()
  {
    $time = false;
    if ($this->next && ($next = $this->engine->nextActiveRecurrence(array('year' => $this->next->year, 'month' => $this->next->month, 'mday' => $this->next->mday + 1, 'hour' => $this->next->hour, 'min' => $this->next->min, 'sec' => $this->next->sec)))) {
      if ($this->allday) {
        $next->hour = $this->hour;  # fix time for all-day events
        $next->min = 0;
      }
      # consider difference in daylight saving between base event and recurring instance
      $dst_diff = ($this->dst_start - $next->format('I')) * 3600;
      $time = $next->timestamp() - $this->tz_offset - $dst_diff;
      $this->next = $next;
    }

    return $time;
  }

  /**
   * Convert the internal structured data into a vcalendar RRULE 2.0 string
   */
  private function to_rrule($recurrence)
  {
    if (is_string($recurrence))
        return $recurrence;

      $rrule = '';
      foreach ((array)$recurrence as $k => $val) {
          $k = strtoupper($k);
          switch ($k) {
          case 'UNTIL':
              $val = gmdate('Ymd\THis', $val);
              break;
          case 'EXDATE':
              foreach ((array)$val as $i => $ex)
                  $val[$i] = gmdate('Ymd\THis', $ex);
              $val = join(',', (array)$val);
              break;
          }
          $rrule .= $k . '=' . $val . ';';
      }

    return $rrule;
  }

}