public function productId(array $condition, array $data)
    {
        if (empty($data['cart']['items']) || !in_array($condition['operator'], array('=', '!='))) {
            return false;
        }

        $ids = array();

        foreach ($data['cart']['items'] as $item) {
            $ids[] = $item['product_id'];
        }

        return $this->compare($ids, $condition['value'], $condition['operator']);
    }