<?php
/**
 * TCacheHttpSession class
 *
 * @author Carl G. Mathisen <carlgmathisen@gmail.com>
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @link http://www.pradosoft.com/
 * @copyright Copyright &copy; 2005-2014 PradoSoft
 * @license http://www.pradosoft.com/license/
 * @package System.Web
 * @since 3.1.1
 */

/**
 * TCacheHttpSession class
 *
 * TCacheHttpSession provides access for storing session data using a cache module (e.g. TMemCache, TDbCache).
 * To specify the cache module for data storage, set the {@link setCacheModuleID CacheModuleID} property
 * which should refer to a valid cache module configured in the application configuration.
 *
 * The following example shows how we configure TCacheHttpSession:
 * <code>
 *  <modules>
 *    <module id="cache" class="System.Caching.TMemCache" Host="localhost" Port="11211" />
 *    <module id="session" class="System.Web.TCacheHttpSession"
 *         CacheModuleID="cache" SessionName="SSID"
 *         CookieMode="Allow" AutoStart="true" GCProbability="1"
 *         UseTransparentSessionID="true" TimeOut="3600" />
 *  </modules>
 * </code>
 *
 * Beware, by definition cache storage are volatile, which means the data stored on them
 * may be swapped out and get lost. This may not be the case for certain cache storage,
 * such as database. So make sure you manage your cache properly to avoid loss of session data.
 *
 * @author Carl G. Mathisen <carlgmathisen@gmail.com>
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @package System.Web
 * @since 3.1.1
 */
class TCacheHttpSession extends THttpSession
{
	private $_prefix='session';
	private $_cacheModuleID='';
	private $_cache;

	/**
	 * Initializes the module.
	 * This method is required by IModule.
	 * It reads the CacheModule property.
	 * @param TXmlElement module configuration
	 */
    public function init($config)
    {
		if($this->_cacheModuleID==='')
			throw new TConfigurationException('cachesession_cachemoduleid_required');
		else if(($cache=$this->getApplication()->getModule($this->_cacheModuleID))===null)
			throw new TConfigurationException('cachesession_cachemodule_inexistent',$this->_cacheModuleID);
		else if($cache instanceof ICache)
			$this->_cache=$cache;
		else
			throw new TConfigurationException('cachesession_cachemodule_invalid',$this->_cacheModuleID);
		$this->setUseCustomStorage(true);
		parent::init($config);
    }

	/**
	 * @return string the ID of the cache module.
	 */
	public function getCacheModuleID()
	{
		return $this->_cacheModuleID;
	}

	/**
	 * @param string the ID of the cache module.
	 */
	public function setCacheModuleID($value)
	{
		$this->_cacheModuleID=$value;
	}

	/**
	 * @return ICache the cache module being used for data storage
	 */
	public function getCache()
	{
		return $this->_cache;
	}

	/**
	 * Session read handler.
	 * @param string session ID
	 * @return string the session data
	 */
	public function _read($id)
	{
	    return $this->_cache->get($this->calculateKey($id));
	}

	/**
	 * Session write handler.
	 * @param string session ID
	 * @param string session data
	 * @return boolean whether session write is successful
	 */
	public function _write($id,$data)
	{
		return $this->_cache->set($this->calculateKey($id),$data,$this->getTimeout());
	}

	/**
	 * Session destroy handler.
	 * This method should be overriden if {@link setUseCustomStorage UseCustomStorage} is set true.
	 * @param string session ID
	 * @return boolean whether session is destroyed successfully
	 */
	public function _destroy($id)
	{
	    return $this->_cache->delete($this->calculateKey($id));
	}

	/**
	 * @return string prefix of session variable name to avoid conflict with other cache data. Defaults to 'session'.
	 */
	public function getKeyPrefix()
	{
	    return $this->_prefix;
	}

	/**
     * @param string prefix of session variable name to avoid conflict with other cache data
     */
	public function setKeyPrefix($value)
	{
	    $this->_prefix=$value;
	}

	/**
	 * @param string session variable name
	 * @return string a safe cache key associated with the session variable name
	 */
	protected function calculateKey($id)
	{
	    return $this->_prefix.':'.$id;
	}
}