<?php
/**
 * TAPCCache class file
 *
 * @author Alban Hanry <compte_messagerie@hotmail.com>
 * @link http://www.pradosoft.com/
 * @copyright Copyright &copy; 2005-2012 PradoSoft
 * @license http://www.pradosoft.com/license/
 * @version $Id$
 * @package System.Caching
 */

/**
 * TAPCCache class
 *
 * TAPCCache implements a cache application module based on {@link http://www.php.net/apc APC}.
 *
 * By definition, cache does not ensure the existence of a value
 * even if it never expires. Cache is not meant to be an persistent storage.
 *
 * To use this module, the APC PHP extension must be loaded and set in the php.ini file the following:
 * <code>
 * apc.cache_by_default=0
 * </code>
 *
 * Some usage examples of TAPCCache are as follows,
 * <code>
 * $cache=new TAPCCache;  // TAPCCache may also be loaded as a Prado application module
 * $cache->init(null);
 * $cache->add('object',$object);
 * $object2=$cache->get('object');
 * </code>
 *
 * If loaded, TAPCCache will register itself with {@link TApplication} as the
 * cache module. It can be accessed via {@link TApplication::getCache()}.
 *
 * TAPCCache may be configured in application configuration file as follows
 * <code>
 * <module id="cache" class="System.Caching.TAPCCache" />
 * </code>
 *
 * @author Alban Hanry <compte_messagerie@hotmail.com>
 * @author Knut Urdalen <knut.urdalen@gmail.com>
 * @version $Id$
 * @package System.Caching
 * @since 3.0b
 */
class TAPCCache extends TCache
{
   /**
    * Initializes this module.
    * This method is required by the IModule interface.
    * @param TXmlElement configuration for this module, can be null
    * @throws TConfigurationException if apc extension is not installed or not started, check your php.ini
    */
	public function init($config)
	{
		if(!extension_loaded('apc'))
			throw new TConfigurationException('apccache_extension_required');
				
		if(ini_get('apc.enabled') == false)
			throw new TConfigurationException('apccache_extension_not_enabled');	
			
		if(substr(php_sapi_name(), 0, 3) === 'cli' and ini_get('apc.enable_cli') == false)
			throw new TConfigurationException('apccache_extension_not_enabled_cli');

		parent::init($config);
	}

	/**
	 * Retrieves a value from cache with a specified key.
	 * This is the implementation of the method declared in the parent class.
	 * @param string a unique key identifying the cached value
	 * @return string the value stored in cache, false if the value is not in the cache or expired.
	 */
	protected function getValue($key)
	{
		return apc_fetch($key);
	}

	/**
	 * Stores a value identified by a key in cache.
	 * This is the implementation of the method declared in the parent class.
	 *
	 * @param string the key identifying the value to be cached
	 * @param string the value to be cached
	 * @param integer the number of seconds in which the cached value will expire. 0 means never expire.
	 * @return boolean true if the value is successfully stored into cache, false otherwise
	 */
	protected function setValue($key,$value,$expire)
	{
		return apc_store($key,$value,$expire);
	}

	/**
	 * Stores a value identified by a key into cache if the cache does not contain this key.
	 * This is the implementation of the method declared in the parent class.
	 *
	 * @param string the key identifying the value to be cached
	 * @param string the value to be cached
	 * @param integer the number of seconds in which the cached value will expire. 0 means never expire.
	 * @return boolean true if the value is successfully stored into cache, false otherwise
	 */
	protected function addValue($key,$value,$expire)
	{
		if(function_exists('apc_add')) {
			return apc_add($key,$value,$expire);
		} else {
			throw new TNotSupportedException('apccache_add_unsupported');
		}
	}

	/**
	 * Deletes a value with the specified key from cache
	 * This is the implementation of the method declared in the parent class.
	 * @param string the key of the value to be deleted
	 * @return boolean if no error happens during deletion
	 */
	protected function deleteValue($key)
	{
		return apc_delete($key);
	}

	/**
	 * Deletes all values from cache.
	 * Be careful of performing this operation if the cache is shared by multiple applications.
	 */
	public function flush()
	{
		return apc_clear_cache('user');
	}
}