<?php
  
  namespace Sabre\VObject\Component;
  
  use Sabre\VObject;
  
  /**
   * The VFreeBusy component
   *
   * This component adds functionality to a component, specific for VFREEBUSY
   * components.
   *
   * @copyright Copyright (C) 2007-2012 Rooftop Solutions. All rights reserved.
   * @author Evert Pot (http://www.rooftopsolutions.nl/)
   * @license http://code.google.com/p/sabredav/wiki/License Modified BSD License
   */
  class VFreeBusy extends VObject\Component {
  
      /**
       * Checks based on the contained FREEBUSY information, if a timeslot is
       * available.
       *
       * @param DateTime $start
       * @param Datetime $end
       * @return bool
       */
      public function isFree(\DateTime $start, \Datetime $end) {
  
          foreach($this->select('FREEBUSY') as $freebusy) {
  
              // We are only interested in FBTYPE=BUSY (the default),
              // FBTYPE=BUSY-TENTATIVE or FBTYPE=BUSY-UNAVAILABLE.
              if (isset($freebusy['FBTYPE']) && strtoupper(substr((string)$freebusy['FBTYPE'],0,4))!=='BUSY') {
                  continue;
              }
  
              // The freebusy component can hold more than 1 value, separated by
              // commas.
              $periods = explode(',', (string)$freebusy);
  
              foreach($periods as $period) {
                  // Every period is formatted as [start]/[end]. The start is an
                  // absolute UTC time, the end may be an absolute UTC time, or
                  // duration (relative) value.
                  list($busyStart, $busyEnd) = explode('/', $period);
  
                  $busyStart = VObject\DateTimeParser::parse($busyStart);
                  $busyEnd = VObject\DateTimeParser::parse($busyEnd);
                  if ($busyEnd instanceof \DateInterval) {
                      $tmp = clone $busyStart;
                      $tmp->add($busyEnd);
                      $busyEnd = $tmp;
                  }
  
                  if($start < $busyEnd && $end > $busyStart) {
                      return false;
                  }
  
              }
  
          }
  
          return true;
  
      }
  
  }