class Listener
{
    /**
     * AmazonPay module object
     *
     * @var AmazonPay
     */
    private $module;

    /**
     * Sets `$module` member var with dependency injection.
     *
     * @author Evan D Shaw <evandanielshaw@gmail.com>
     * @param AmazonPay $module
     * @return void
     */
    public function __construct(AmazonPay $module) {
        $this->module = $module;
    }

    /**
     * Listens for IPN messages from Amazon
     *
     * If the IPN is valid, the associated Welcart order object is updated
     *
     * @author Evan D Shaw <evandanielshaw@gmail.com>
     * @return void
     */
    public function listen() {
        $body = file_get_contents('php://input');
        $message = json_decode($body, true);
        if (empty($message)) {
            return;
        }
        if (!isset($message['Message'])) {
            return;
        }
        $response = json_decode($message['Message'], true);
        if (!isset($response['ObjectType']) || !isset($response['ObjectId'])) {
            return;
        }

        $opts = $this->module->getActingOpts();
        $opts['ipn_verified'] = true;
        $this->module->updateActingOpts($opts);

        switch ($response['ObjectType']) {
            case EventNames::CHARGE:
                $orderId = $this->getOrderIdFromChargeId($response['ObjectId']);
                if ($orderId !== null) {
                    $order = new Models\OrderMeta($orderId);
                    if (!in_array($response['NotificationId'], $order->getIpnNotificationIds(), true)) {
                        $order->updateNotificationIds($response['NotificationId']);
                        $this->updateChargeState($order);
                    }
                }
                break;
            case EventNames::REFUND:
                $orderId = $this->getOrderIdFromRefundId($response['ObjectId']);
                if ($orderId !== null) {
                    $order = new Models\OrderMeta($orderId);
                    if (!in_array($response['NotificationId'], $order->getIpnNotificationIds(), true)) {
                        $order->updateNotificationIds($response['NotificationId']);
                        $this->updateRefundState($order);
                    }
                }
                break;
        }
    }

    /**
     * Updates charge state
     *
     * @author Evan D Shaw <evandanielshaw@gmail.com>
     * @param Models\OrderMeta $order
     * @return void
     */
    public function updateChargeState(Models\OrderMeta $order) {
        // order state is updated automatically by this API
        $result = (new API\Charge\Get($this->module, $order))->get($order->getChargeId());
        if ($result instanceof GenericError) {
            // 100 tells Amazon to retry later
            http_response_code(100);
            exit();
        }
    }

    /**
     * Updates refund state
     *
     * @author Evan D Shaw <evandanielshaw@gmail.com>
     * @param Models\OrderMeta $order
     * @return void
     */
    public function updateRefundState(Models\OrderMeta $order) {
        // order state is updated automatically by this API
        $result = (new API\Refund\Get($this->module, $order))->get($order->getRefundId());
        if ($result instanceof GenericError) {
            // 100 tells Amazon to retry later
            http_response_code(100);
            exit();
        }
    }

    /**
     * Returns the order_id associated with an Amazon Pay chargeId, if one exists
     *
     * @author Evan D Shaw <evandanielshaw@gmail.com>
     * @global \wpdb $wpdb
     * @param string $chargeId
     * @return int|null
     */
    public function getOrderIdFromChargeId($chargeId) {
        global $wpdb;

        $order_meta_table_name = $wpdb->prefix . 'usces_order_meta';
        $query = $wpdb->prepare(
            "SELECT order_id
            FROM {$order_meta_table_name}
            WHERE meta_key = %s
            AND meta_value = %s
            ORDER BY order_id ASC
            LIMIT 1",
            Models\OrderMeta::CHARGE_ID,
            $chargeId
        );
        $orderId = $wpdb->get_var($query);
        if (empty($orderId)) {
            return null;
        }

        return $orderId;
    }

    /**
     * Returns the order_id associated with an Amazon Pay refundId, if one exists
     *
     * @author Evan D Shaw <evandanielshaw@gmail.com>
     * @global \wpdb $wpdb
     * @param string $refundId
     * @return int|null
     */
    public function getOrderIdFromRefundId($refundId) {
        global $wpdb;

        $order_meta_table_name = $wpdb->prefix . 'usces_order_meta';
        $query = $wpdb->prepare(
            "SELECT order_id
            FROM {$order_meta_table_name}
            WHERE meta_key = %s
            AND meta_value = %s
            ORDER BY order_id ASC
            LIMIT 1",
            Models\OrderMeta::REFUND_ID,
            $refundId
        );
        $orderId = $wpdb->get_var($query);
        if (empty($orderId)) {
            return null;
        }

        return $orderId;
    }
}