<?php
/* $Id$ */
namespace Mammut\Storage\CachedStore;

(defined('MAMMUT') && (basename(__FILE__) != basename($_SERVER['PHP_SELF']))) or die('ACCESS DENIED');

use Mammut\Storage\KeyValue\iKeyValueStore;
use Mammut\Cache\None;
use Mammut\Cache\Simple;

/**
 * Stroage helper which provides a caching layer.
 * 
 * @author Stefan Daurer <s.daurer@q-spot.org>
 * @package Mammut\Storage\CachedStore
 * @since 1.1.0.0
 */
abstract class CachedStore extends \Mammut\StdObject {
	protected $cache;
	protected $ttl = 60;
	protected $cacheKeyPrefix = '';

	public function __construct() {
		$this->cache = new Simple();
	}
	
	public function setTTL($ttl) {
		$this->ttl = (int) $ttl;
	}
	
	public function getTTL() {
		return $this->ttl;
	}

	public function store($key, $value) {
		$this->storePersistend($key, $value);
		$this->cache->set($this->cacheKeyPrefix . $key, $value, $this->ttl);
	}

	public function fetch($key) {
		$val = NULL;
		if($this->cache->keyExists($key))
			$val = $this->cache->get($key);
		if(is_null($val))
			$val = $this->fetchPersistend($key);
		if(!is_null($val))
			$this->cache->set($key, $val, $this->ttl);
		return $val;
	}

	public function exist($key) {
		if($this->cache->keyExists($key))
			return true;
		return $this->existPersistend($key);
	}

	public function delete($key) {
		$this->deletePersistend($key);
		$this->cache->delete($key);
	}

	/**
	 * Method which is called when a value should be stored to save the value in the
	 * persistend storage.
	 *
	 * @param string $key
	 *        	the value key
	 * @param mixed $value
	 *        	the new value
	 */
	protected abstract function storePersistend($key, $value);

	protected abstract function fetchPersistend($key);

	protected abstract function existPersistend($key);

	protected abstract function deletePersistend($key);
}