<field name="downloadid" type="text" default=""
               label="COMMON_DOWNLOADID_LABEL" description ="COMMON_DOWNLOADID_DESCRIPTION" class="text-long" />

/*
 * This code is called in frontend with every page load
 * which is consuming resources unnecessarily
 * Todo: find a way to make this code run on template backend on save only
 * possible solution: extention plug-in which hooks into gantry template save event
 */
class GantryFeatureDownloadId extends GantryFeature 
{
  var $_feature_name = 'downloadId';
  var $_extra_query = "";

  function isEnabled() {

    global $gantry;


    $dID = $gantry->get('downloadid');
    if (!empty($dID)){
      $this->_extra_query= "downloadid=$dID";
      return true;
    }

    return false;
  }


  function init() {

    global $gantry;

    parent::init();

    if (!empty($this->_extra_query)) {
      $this->SetUpdateSite($this->_extra_query,  $this->GetExtensionId());
    }
  }


  private function GetExtensionId()
  {
    global $gantry;

    $templateName= $gantry->_template->getName();

    $db    = JFactory::getDbo();
    $query = $db->getQuery(true)
        ->select('extension_id')
        ->from($db->qn('#__extensions'))
        ->where($db->qn('client_id') . ' = ' . $db->q(0))
        ->where($db->qn('type') . ' = ' . $db->q('template'))
        ->where($db->qn('name') . ' = ' . $db->q($templateName))
    ;
    $db->setQuery($query);

    return $db->loadResult();
  }


  private function SetUpdateSite($extra_query, $extensionId)
  {

    if(empty($extra_query) || empty($extensionId)) return; // do nothing

    $db    = JFactory::getDbo();
    $query = $db->getQuery(true)
        ->select('update_site_id')
        ->from($db->qn('#__update_sites_extensions'))
        ->where($db->qn('extension_id') . ' = ' . $db->q($extensionId));
    $db->setQuery($query);
    $updateSiteId = $db->loadResult();

    if ($updateSiteId) {
      // Update the update site record
      $query = $db->getQuery(true)
          ->update($db->qn('#__update_sites'))
          ->set(array(
                    $db->quoteName('extra_query') . ' = ' . $db->q($extra_query),
                    $db->quoteName('enabled') . ' = ' . 1,
                    $db->quoteName('last_check_timestamp') . ' = ' . 0,
                ))
          ->where($db->qn('update_site_id') . ' = ' . $db->q($updateSiteId));
      $db->setQuery($query);
      $db->execute();

      // Delete any existing updates (essentially flushes the updates cache for this update site)
      $query = $db->getQuery(true)
          ->delete($db->qn('#__updates'))
          ->where($db->qn('update_site_id') . ' = ' . $db->q($updateSiteId));
      $db->setQuery($query);
      $db->execute();
    }
  }
}