<?php
class Object_Cache_Factory {

    private static $instance = null;

    public static function newInstance()
    {
        if( self::$instance == null ) {
            self::$instance = self::getCache();
        }
        return self::$instance;
    }

    public static function getCache() {
        if(self::$instance == null) {
            $cache = 'default';
            if( defined('OSC_CACHE') ) {
                $cache = OSC_CACHE;
            }

            $cache_class = 'Object_Cache_'.$cache;
            $file = dirname(__FILE__) . '/caches/' . $cache_class. '.php';

            if(strpos($file, '../')===false && strpos($file, '..\\')===false && file_exists($file)) {
                require_once $file;
                if(class_exists($cache_class)) {
                    // all correct ?
                    if( call_user_func(array($cache_class, 'is_supported')) ) {
                        self::$instance = new $cache_class();
                    } else {
                        $file = dirname(__FILE__) . '/caches/Object_Cache_default.php';
                        require_once $file;
                        self::$instance = new Object_Cache_default();
                        error_log('Cache '. $cache .' NOT SUPPORTED - loaded Object_Cache_default cache');
                    }
                    return self::$instance;
                }
            }
            throw new Exception('Unknown cache');
        } else {
            return self::$instance;
        }
    }
}