public static function decode($cookie)
    {
        $params = (array) json_decode(base64_decode($cookie), true);

        return new self((string) array_value($params, 'user_email'),
                        (string) array_value($params, 'agent'),
                        (string) array_value($params, 'series'),
                        (string) array_value($params, 'token'));
    }