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<?php

/* --------------------------------------------------------------
   CacheTokenHelper.inc.php 2016-06-23
   Gambio GmbH
   http://www.gambio.de
   Copyright (c) 2016 Gambio GmbH
   Released under the GNU General Public License (Version 2)
   [http://www.gnu.org/licenses/gpl-2.0.html]
   --------------------------------------------------------------
*/

/**
 * Class CacheTokenHelper
 *
 * This class returns the cache token string that is saved in the cache directory. This token can be
 * used for cache busting of various resources. It is cleared whenever the module data are removed 
 * from the "cache" directory (also known as persistent data). 
 * 
 * @category   System
 * @package    Extensions
 * @subpackage Helpers
 */
class CacheTokenHelper implements CacheTokenHelperInterface
{
    /**
     * Returns the cache token string.
     *
     * @return string
     */
    public function getCacheToken()
    {
        $dataCache = DataCache::get_instance(); 
        $cacheToken = $dataCache->get_persistent_data('cache_token'); 
        
        if(empty($cacheToken))
        {
            $cacheToken = md5(time());
            $dataCache->write_persistent_data('cache_token', $cacheToken); 
        }
        
        return $cacheToken; 
    }
}