<?php
/**
 * Implementation methode Memoization
 *
 * @package SPIP\memoization\Memo
 **/

// Sécurité
if (!defined('_ECRIRE_INC_VERSION')){
	return;
}

# http://php.net/memcache

if (!defined('_CACHE_NAMESPACE')){
	define('_CACHE_NAMESPACE', $_SERVER["SERVER_NAME"] . ":" . $_SERVER["SERVER_PORT"] . ":");
}
if (!defined('_LOCK_MAX')){
	define('_LOCK_MAX', 30);
} # max lock time (seconds)

class MCacheBackend_memcache implements MCacheBackend {
	private $memcache = null;
	private $ok = false;

	/* Interface */

	public function init($params = null){
		foreach (MCache::config_memcache_servers() as $server){
			list($host, $port) = explode(':', $server);
			if (!$this->memcache){
				$this->memcache = @memcache_connect($host, $port);
			} else {
				@memcache_add_server($this->memcache, $host, $port);
			}
		}
		if ($this->memcache){
			$this->ok = true;
		}
	}

	public function get($key){
		if (!$this->ok){
			return null;
		}
		$a = memcache_get($this->memcache, _CACHE_NAMESPACE . $key);
		// maybe_unserialize
		if (is_array($a)){
			return @unserialize($a[0]);
		} else {
			return $a;
		}
	}

	public function set($key, $value, $ttl = null){
		if (!$this->ok){
			return null;
		}
		// maybe_serialize
		if (is_object($value) or is_array($value) or is_null($value)){
			$value = array(serialize($value));
		}
		$flag = strlen(is_array($value) ? $value[0] : $value)>16000
			? MEMCACHE_COMPRESSED : 0;
		return is_null($ttl)
			? memcache_set($this->memcache, _CACHE_NAMESPACE . $key, $value)
			: memcache_set($this->memcache, _CACHE_NAMESPACE . $key, $value, $flag, $ttl);
	}

	public function exists($key){
		if (!$this->ok){
			return null;
		}
		return memcache_get($this->memcache, _CACHE_NAMESPACE . $key)!==FALSE;
	}

	public function del($key){
		if (!$this->ok){
			return null;
		}
		return memcache_delete($this->memcache, _CACHE_NAMESPACE . $key, 0);
	}

	public function inc($key, $value = null, $ttl = null){
		if (!$this->ok){
			return null;
		}

		// set if not exists
		@memcache_add($this->memcache, _CACHE_NAMESPACE . $key, 0, $ttl);

		if (!isset($value)){
			$value = 1;
		}
		return memcache_increment($this->memcache, _CACHE_NAMESPACE . $key, $value);
	}

	public function dec($key, $value = null, $ttl = null){
		if (!$this->ok){
			return null;
		}

		// set if not exists
		memcache_add($this->memcache, _CACHE_NAMESPACE . $key, 0, $ttl);

		if (!isset($value)){
			$value = 1;
		}
		return memcache_decrement($this->memcache, _CACHE_NAMESPACE . $key, $value);
	}

	public function lock($key, /* private */ $unlock = false){
		static $locks = array();

		if (!$this->ok){
			return null;
		}

		/* unlock */
		if ($unlock){
			unset($locks[$key]);
			$this->del('lock::' . $key);
		} /* lock */
		else {
			# si on l'a deja, ok
			if (isset($locks[$key])){
				return true;
			}

			# sinon s'il existe, on attend qu'il se libere
			$wait = 0;
			while ($this->exists('lock::' . $key)){
				if ($wait++<_LOCK_MAX){
					sleep(1);
				} else {
					return false;
				}
			}

			# ... puis on le pose
			# attention inc() renvoie parfois false (??)
			if ($this->inc('lock::' . $key, 1, _LOCK_MAX)<=1){
				$this->set('lock::' . $key, 2, _LOCK_MAX);
				$locks[$key] = true;
				register_shutdown_function(array($this, 'unlock'), $key);
				return true;
			}

			return false;
		}
	}

	public function unlock($key){
		if (!$this->ok){
			return null;
		}
		$this->lock($key, true);
	}

	public function size(){
		return false;
	}

	public function purge(){
		return false;
	}

}