<?php
/**
 * AKSRT Topic Pay — forum topic multi-gateway cashier.
 *
 * Contract:
 * - visibility = pay topics only (credits path stays on unlock_topic_with_credits)
 * - product_type = resource, product_id = topic_id
 * - order note.topic_pay = 1
 * - unlock: has_user_paid_topic (order OR unlock list OR VIP free)
 * - coupon: _aksrt_topic_coupon_s + AKSRT_Coupon (cash only; no affiliate stack)
 *
 * @package AKSRT
 */

defined('ABSPATH') || exit;

class AKSRT_Topic_Pay {

    private static $instance = null;

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

    public function init(): void {
        add_action('rest_api_init', [$this, 'register_routes']);
        add_action('aksrt_order_paid', [$this, 'on_order_paid'], 16, 2);
    }

    public function register_routes(): void {
        register_rest_route('aksrt/v1', '/pay/topic/(?P<id>\\d+)', [
            [
                'methods'             => 'GET',
                'callback'            => [$this, 'rest_preview'],
                'permission_callback' => [$this, 'check_rest_nonce'],
            ],
            [
                'methods'             => 'POST',
                'callback'            => [$this, 'rest_purchase'],
                'permission_callback' => [$this, 'check_rest_nonce'],
            ],
        ]);
    }

    /**
     * @param WP_REST_Request $request
     * @return true|WP_Error
     */
    public function check_rest_nonce(WP_REST_Request $request) {
        $nonce = $request->get_header('x-wp-nonce');
        if (!$nonce) {
            return new WP_Error('aksrt_rest_no_nonce', __('缺少安全令牌', 'aksrt'), ['status' => 403]);
        }
        if (!wp_verify_nonce($nonce, 'wp_rest')) {
            return new WP_Error('aksrt_rest_bad_nonce', __('安全令牌已过期，请刷新页面', 'aksrt'), ['status' => 403]);
        }
        return true;
    }

    public function rest_preview(WP_REST_Request $request) {
        $topic_id = (int) $request['id'];
        $uid = get_current_user_id();
        $coupon_code = sanitize_text_field((string) ($request->get_param('coupon_code') ?? $request->get_param('coupon') ?? ''));
        $preview = $this->preview($topic_id, $uid, $coupon_code);
        if (is_wp_error($preview)) {
            return $preview;
        }
        return new WP_REST_Response($preview, 200);
    }

    public function rest_purchase(WP_REST_Request $request) {
        $topic_id = (int) $request['id'];
        $uid = get_current_user_id();
        if ($uid <= 0) {
            $post = get_post($topic_id);
            return new WP_Error('aksrt_need_login', __('请先登录后再购买。', 'aksrt'), [
                'status' => 401,
                'login_url' => wp_login_url($post ? get_permalink($post) : home_url('/')),
            ]);
        }

        $params = $request->get_json_params();
        if (!is_array($params)) {
            $params = $request->get_params();
        }

        $payment_method = sanitize_key((string) ($params['payment_method'] ?? 'balance'));
        if ($payment_method === '' || $payment_method === 'cash') {
            $payment_method = 'balance';
        }
        $coupon_code = sanitize_text_field((string) ($params['coupon_code'] ?? $params['coupon'] ?? ''));

        return $this->rest_wrap_result(
            $this->create_cash_order($topic_id, $uid, $payment_method, $coupon_code)
        );
    }

    /**
     * @param mixed $result
     * @return WP_REST_Response|WP_Error
     */
    private function rest_wrap_result($result) {
        if (is_wp_error($result)) {
            return $result;
        }
        if (empty($result['success'])) {
            $code = sanitize_key((string) ($result['code'] ?? 'aksrt_pay_failed'));
            $status = (int) ($result['status'] ?? 400);
            return new WP_Error(
                $code !== '' ? $code : 'aksrt_pay_failed',
                (string) ($result['message'] ?? __('支付失败', 'aksrt')),
                array_merge(
                    ['status' => $status > 0 ? $status : 400],
                    is_array($result['data'] ?? null) ? $result['data'] : []
                )
            );
        }
        return new WP_REST_Response($result, 200);
    }

    /**
     * Cashier preview payload (content-pay field subset for cms-download).
     *
     * @return array|WP_Error
     */
    public function preview(int $topic_id, int $user_id = 0, string $coupon_code = '') {
        $assert = $this->assert_topic($topic_id);
        if (is_wp_error($assert)) {
            return $assert;
        }
        /** @var WP_Post $post */
        $post = $assert['post'];
        $uid = $user_id > 0 ? $user_id : get_current_user_id();
        $coupon_code = sanitize_text_field($coupon_code);

        if ($uid <= 0) {
            return [
                'post_id' => $topic_id,
                'title' => get_the_title($post),
                'permalink' => get_permalink($post),
                'pay_modo' => '0',
                'pay_type' => 'topic',
                'pay_type_label' => __('付费主题', 'aksrt'),
                'amount' => 0,
                'base' => 0,
                'list_amount' => 0,
                'payable' => 0,
                'currency' => '￥',
                'amount_label' => '',
                'base_label' => '',
                'list_amount_label' => '',
                'is_free' => false,
                'has_paid_access' => false,
                'need_login' => true,
                'allow_guest' => false,
                'need_vip' => false,
                'need_purchase' => true,
                'logged_in' => false,
                'balance' => 0,
                'balance_enough' => false,
                'payment_methods' => [],
                'login_url' => wp_login_url(get_permalink($post)),
                'vip_url' => home_url('/'),
                'credits_url' => home_url('/'),
                'coupon_allowed' => false,
                'coupon_desc' => '',
                'coupon_code' => '',
                'coupon' => null,
                'coupon_error' => '',
                'coupon_discount' => 0,
                'coupon_discount_label' => '',
                'rebate_discount' => 0,
                'rebate_discount_label' => '',
                'points_deduction_allowed' => false,
                'card_pass_allowed' => false,
                'price_type' => '',
            ];
        }

        $priced = $this->resolve_price($topic_id, $uid);
        $list_amount = round((float) ($priced['amount'] ?? 0), 2);
        $base = round((float) ($priced['base'] ?? $list_amount), 2);
        $vip_free = !empty($priced['is_free']) || ($list_amount <= 0 && !empty($priced['is_vip_price']));
        $has_paid = $this->user_has_paid($uid, $topic_id);

        $balance = 0;
        if (class_exists('AKSRT_Credits')) {
            $balance = (int) AKSRT_Credits::balance($uid);
        }

        $methods = function_exists('aksrt_list_cash_payment_methods')
            ? aksrt_list_cash_payment_methods(true)
            : [['id' => 'balance', 'name' => __('站内余额', 'aksrt')]];

        $coupon_allowed = $this->is_coupon_allowed($topic_id);
        $coupon_error = '';
        $coupon_discount = 0.0;
        $coupon_meta = null;
        $applied_code = '';
        $payable = $list_amount;

        if (!$vip_free && $list_amount > 0) {
            $discounted = $this->apply_topic_cash_discounts($priced, $topic_id, $uid, $coupon_code, true);
            if (is_wp_error($discounted)) {
                $coupon_error = $discounted->get_error_message();
                $discounted = $this->apply_topic_cash_discounts($priced, $topic_id, $uid, '', true);
            }
            if (!is_wp_error($discounted)) {
                $list_amount = round((float) ($discounted['list_amount'] ?? $list_amount), 2);
                $payable = round((float) ($discounted['payable'] ?? $list_amount), 2);
                $coupon_discount = round((float) ($discounted['coupon_discount'] ?? 0), 2);
                $coupon_meta = !empty($discounted['coupon']) ? $discounted['coupon'] : null;
                $applied_code = (string) ($discounted['coupon_code'] ?? ($coupon_meta['code'] ?? ''));
                if ($coupon_error === '' && !empty($discounted['coupon_error'])) {
                    $coupon_error = (string) $discounted['coupon_error'];
                }
            }
        } elseif ($vip_free) {
            $payable = 0.0;
            $list_amount = 0.0;
        }

        $is_free = $vip_free || $payable <= 0;
        $amount_label = $is_free
            ? __('免费', 'aksrt')
            : sprintf('¥%s', number_format($payable, 2, '.', ''));
        $list_label = sprintf('¥%s', number_format($list_amount > 0 ? $list_amount : $base, 2, '.', ''));
        $base_label = sprintf('¥%s', number_format($base, 2, '.', ''));

        return [
            'post_id' => $topic_id,
            'title' => get_the_title($post),
            'permalink' => get_permalink($post),
            'pay_modo' => '0',
            'pay_type' => 'topic',
            'pay_type_label' => __('付费主题', 'aksrt'),
            'amount' => $payable,
            'base' => $base,
            'list_amount' => $list_amount > 0 ? $list_amount : $base,
            'list_amount_label' => $list_label,
            'payable' => $payable,
            'currency' => '￥',
            'amount_label' => $amount_label,
            'base_label' => $base_label,
            'is_free' => $is_free,
            'has_paid_access' => $has_paid,
            'paid_order' => null,
            'pending_order' => null,
            'need_login' => false,
            'allow_guest' => false,
            'need_vip' => false,
            'need_purchase' => !$has_paid && !$is_free,
            'logged_in' => true,
            'balance' => $balance,
            'balance_enough' => true,
            'payment_methods' => $methods,
            'login_url' => wp_login_url(get_permalink($post)),
            'vip_url' => home_url('/'),
            'credits_url' => home_url('/'),
            'coupon_allowed' => $coupon_allowed,
            'coupon_desc' => $coupon_allowed ? __('支持优惠码', 'aksrt') : '',
            'coupon_code' => $applied_code,
            'coupon' => $coupon_meta,
            'coupon_error' => $coupon_error,
            'coupon_discount' => $coupon_discount,
            'coupon_discount_label' => $coupon_discount > 0
                ? ('-' . sprintf('¥%s', number_format($coupon_discount, 2, '.', '')))
                : '',
            'rebate_discount' => 0,
            'rebate_discount_label' => '',
            'points_deduction_allowed' => false,
            'card_pass_allowed' => false,
            'price_type' => '',
            'vip_level' => (int) ($priced['vip_level'] ?? 0),
            'is_vip_price' => !empty($priced['is_vip_price']),
        ];
    }

    /**
     * Create cash order and invoke gateway.
     *
     * @return array|WP_Error
     */
    public function create_cash_order(int $topic_id, int $user_id, string $payment_method = 'balance', string $coupon_code = '') {
        if ($user_id <= 0) {
            return new WP_Error('aksrt_need_login', __('请先登录后再购买。', 'aksrt'), ['status' => 401]);
        }

        $assert = $this->assert_topic($topic_id);
        if (is_wp_error($assert)) {
            return $assert;
        }
        /** @var WP_Post $post */
        $post = $assert['post'];

        if ($this->user_has_paid($user_id, $topic_id)) {
            return new WP_Error('aksrt_already_paid', __('已购买，可直接查看。', 'aksrt'), ['status' => 400]);
        }

        $priced = $this->resolve_price($topic_id, $user_id);
        $list_amount = round((float) ($priced['amount'] ?? 0), 2);
        $base = round((float) ($priced['base'] ?? $list_amount), 2);
        $vip_free = !empty($priced['is_free']) || ($list_amount <= 0 && !empty($priced['is_vip_price']));
        $coupon_code = sanitize_text_field($coupon_code);

        // VIP free (no purchase price) — no coupon stack.
        if ($vip_free) {
            return $this->create_free_paid_order($topic_id, $user_id, $post, $priced, [
                'list_amount' => 0.0,
                'payable' => 0.0,
                'coupon_code' => '',
                'coupon_discount' => 0.0,
                'coupon' => [],
                'message' => __('VIP 免费解锁成功', 'aksrt'),
                'paid_note' => __('VIP 免费解锁主题。', 'aksrt'),
            ]);
        }

        if ($list_amount <= 0) {
            return new WP_Error('aksrt_price_unset', __('价格未设置', 'aksrt'), ['status' => 400]);
        }

        $discounted = $this->apply_topic_cash_discounts($priced, $topic_id, $user_id, $coupon_code, false);
        if (is_wp_error($discounted)) {
            return $discounted;
        }

        $list_amount = round((float) ($discounted['list_amount'] ?? $list_amount), 2);
        $amount = round((float) ($discounted['payable'] ?? $list_amount), 2);
        $coupon_discount = round((float) ($discounted['coupon_discount'] ?? 0), 2);
        $coupon_meta = is_array($discounted['coupon'] ?? null) ? $discounted['coupon'] : [];
        $coupon_code_norm = (string) ($coupon_meta['code'] ?? $discounted['coupon_code'] ?? $coupon_code);

        // Free after coupon discount.
        if ($amount <= 0) {
            return $this->create_free_paid_order($topic_id, $user_id, $post, $priced, [
                'list_amount' => $list_amount,
                'payable' => 0.0,
                'coupon_code' => $coupon_code_norm,
                'coupon_discount' => $coupon_discount,
                'coupon' => $coupon_meta,
                'message' => __('无需支付，已可访问。', 'aksrt'),
                'paid_note' => __('优惠后无需支付。', 'aksrt'),
            ]);
        }

        if (!class_exists('AKSRT_Order') || !class_exists('AKSRT_Order_Repository')) {
            return new WP_Error('aksrt_pay_unavailable', __('支付系统不可用。', 'aksrt'), ['status' => 500]);
        }

        $payment_method = sanitize_key($payment_method);
        if ($payment_method === '') {
            $payment_method = 'balance';
        }

        $pending = $this->find_pending_topic_order($user_id, $topic_id);
        $can_resume = false;
        if ($pending && abs((float) ($pending['amount'] ?? 0) - $amount) < 0.001) {
            $pending_meta = $this->decode_order_note_meta($pending);
            $pending_coupon = (string) ($pending_meta['coupon_code'] ?? '');
            if (is_array($pending_meta['coupon'] ?? null)) {
                $pending_coupon = (string) ($pending_meta['coupon']['code'] ?? $pending_coupon);
            }
            if ($pending_coupon === $coupon_code_norm) {
                $can_resume = true;
            }
        }

        if ($can_resume) {
            $order_number = (string) ($pending['order_number'] ?? '');
            $order = $pending;
        } else {
            $note = wp_json_encode([
                'topic_pay' => 1,
                'topic_id' => $topic_id,
                'pay_modo' => '0',
                'vip_level' => (int) ($priced['vip_level'] ?? 0),
                'base' => $base,
                'list_amount' => $list_amount,
                'amount' => $amount,
                'payable' => $amount,
                'coupon_code' => $coupon_code_norm,
                'coupon_discount' => $coupon_discount,
                'coupon' => $coupon_meta,
                'ip_address' => function_exists('aksrt_pay_client_ip') ? aksrt_pay_client_ip() : (string) ($_SERVER['REMOTE_ADDR'] ?? ''),
            ], JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);

            $order_number = AKSRT_Order_Repository::get_instance()->create([
                'user_id' => $user_id,
                'product_type' => AKSRT_Domain_Model::ORDER_PRODUCT_RESOURCE,
                'product_id' => $topic_id,
                'amount' => $amount,
                'currency' => 'CNY',
                'status' => AKSRT_Order::STATUS_PENDING,
                'payment_method' => $payment_method,
                'note' => is_string($note) ? $note : '',
                'expires_at' => gmdate('Y-m-d H:i:s', time() + 30 * MINUTE_IN_SECONDS),
            ]);

            if ($order_number === '') {
                return new WP_Error('aksrt_order_create_failed', __('创建订单失败。', 'aksrt'), ['status' => 500]);
            }

            $order = AKSRT_Order_Repository::get_instance()->get($order_number);
            if (!$order) {
                return new WP_Error('aksrt_order_create_failed', __('创建订单失败。', 'aksrt'), ['status' => 500]);
            }
        }

        $order['subject'] = sprintf(
            /* translators: %s: topic title */
            __('购买论坛主题「%s」', 'aksrt'),
            get_the_title($post)
        );
        $order['payment_method'] = $payment_method;
        $order['amount'] = $amount;

        if (!class_exists('AKSRT_Payment_Gateway')) {
            return new WP_Error('aksrt_pay_unavailable', __('支付网关不可用。', 'aksrt'), ['status' => 500]);
        }

        $gateway_manager = AKSRT_Payment_Gateway::get_instance();
        $gateway = $gateway_manager->get_gateway($payment_method);
        if (!$gateway) {
            return new WP_Error('aksrt_gateway_unavailable', __('当前支付方式不可用。', 'aksrt'), [
                'status' => 400,
                'order_number' => $order_number,
            ]);
        }
        if (method_exists($gateway, 'is_configured') && !$gateway->is_configured()) {
            return new WP_Error('aksrt_gateway_unconfigured', __('该支付方式尚未配置，请联系站长。', 'aksrt'), [
                'status' => 400,
                'order_number' => $order_number,
            ]);
        }

        $payment_result = $gateway->create_payment($order);
        if (empty($payment_result['success'])) {
            $msg = (string) ($payment_result['message'] ?? __('支付失败。', 'aksrt'));
            $code = ($payment_method === 'balance' && (str_contains($msg, '余额') || str_contains($msg, '不足')))
                ? 'aksrt_balance_insufficient'
                : 'aksrt_pay_failed';
            return new WP_Error($code, $msg, [
                'status' => 402,
                'order_number' => $order_number,
            ]);
        }

        $code_url = (string) ($payment_result['payment_data']['code_url'] ?? '');
        $payment_url = (string) ($payment_result['payment_url'] ?? '');
        if ($payment_url !== '' || $code_url !== '') {
            return [
                'success' => true,
                'data' => [
                    'redirect' => true,
                    'payment_url' => $payment_url,
                    'qr_content' => $code_url,
                    'order_number' => $order_number,
                    'amount' => $amount,
                    'pay_modo' => '0',
                    'message' => $payment_result['message'] ?? __('请在新页面完成支付。', 'aksrt'),
                    'reload' => false,
                    'poll' => true,
                ],
            ];
        }

        // Sync gateway (balance): mark paid.
        $paid = AKSRT_Order::get_instance()->update_status($order_number, AKSRT_Order::STATUS_PAID, [
            'payment_method' => $payment_method,
            'payment_transaction_id' => sanitize_text_field((string) ($payment_result['transaction_id'] ?? '')),
            'note' => __('用户完成论坛主题购买支付。', 'aksrt'),
        ]);
        if (!$paid) {
            return new WP_Error('aksrt_order_confirm_failed', __('订单确认失败。', 'aksrt'), ['status' => 500]);
        }

        $this->mark_unlocked($user_id, $topic_id);

        return [
            'success' => true,
            'data' => [
                'order_number' => $order_number,
                'amount' => $amount,
                'pay_modo' => '0',
                'message' => $payment_result['message'] ?? __('支付成功', 'aksrt'),
                'reload' => true,
            ],
        ];
    }

    /**
     * On paid: unlock topic + burn coupon (idempotent).
     */
    public function on_order_paid(string $order_number, array $paid_order): void {
        $product_type = sanitize_key((string) ($paid_order['product_type'] ?? ''));
        if ($product_type !== AKSRT_Domain_Model::ORDER_PRODUCT_RESOURCE) {
            return;
        }

        $topic_id = (int) ($paid_order['product_id'] ?? 0);
        $user_id = (int) ($paid_order['user_id'] ?? 0);
        if ($topic_id <= 0 || $user_id <= 0) {
            return;
        }

        $meta = $this->decode_order_note_meta($paid_order);
        $is_topic_pay = !empty($meta['topic_pay']);
        if (!$is_topic_pay) {
            $post = get_post($topic_id);
            if (!($post instanceof WP_Post) || $post->post_type !== 'aksrt_forum_topic') {
                return;
            }
        }

        $this->mark_unlocked($user_id, $topic_id);
        $this->finalize_topic_order_side_effects($order_number, $paid_order);
    }

    /**
     * @return array{post:WP_Post}|WP_Error
     */
    private function assert_topic(int $topic_id) {
        $post = get_post($topic_id);
        if (!($post instanceof WP_Post) || $post->post_type !== 'aksrt_forum_topic') {
            return new WP_Error('aksrt_invalid', __('主题不存在', 'aksrt'), ['status' => 404]);
        }
        if ($post->post_status !== 'publish') {
            return new WP_Error('aksrt_invalid', __('主题不可购买', 'aksrt'), ['status' => 404]);
        }

        $visibility = sanitize_key((string) get_post_meta($topic_id, '_aksrt_visibility', true));
        if ($visibility !== AKSRT_Forum::VISIBILITY_PAY) {
            return new WP_Error('aksrt_not_paid', __('该主题不是付费可见内容', 'aksrt'), ['status' => 400]);
        }

        return ['post' => $post];
    }

    /**
     * @return array{amount:float,is_vip_price:bool,is_free:bool,label:string,base:float,vip_set:bool,vip_level:int}
     */
    private function resolve_price(int $topic_id, int $user_id): array {
        if (class_exists('AKSRT_Forum')) {
            return AKSRT_Forum::get_instance()->resolve_topic_pay_price($topic_id, $user_id);
        }
        return [
            'amount' => max(0.0, (float) get_post_meta($topic_id, '_aksrt_pay_price', true)),
            'is_vip_price' => false,
            'is_free' => false,
            'label' => '',
            'base' => max(0.0, (float) get_post_meta($topic_id, '_aksrt_pay_price', true)),
            'vip_set' => false,
            'vip_level' => 0,
        ];
    }

    private function user_has_paid(int $user_id, int $topic_id): bool {
        if (class_exists('AKSRT_Forum')) {
            return AKSRT_Forum::get_instance()->has_user_paid_topic($user_id, $topic_id);
        }
        if (class_exists('AKSRT_Order')) {
            return AKSRT_Order::get_instance()->has_paid_access(
                $user_id,
                AKSRT_Domain_Model::ORDER_PRODUCT_RESOURCE,
                $topic_id
            );
        }
        return false;
    }

    private function mark_unlocked(int $user_id, int $topic_id): void {
        if (class_exists('AKSRT_Forum') && method_exists('AKSRT_Forum', 'mark_topic_unlocked')) {
            AKSRT_Forum::get_instance()->mark_topic_unlocked($user_id, $topic_id);
            return;
        }
        if ($user_id <= 0 || $topic_id <= 0) {
            return;
        }
        $unlocked = get_user_meta($user_id, 'aksrt_unlocked_topics', true);
        if (!is_array($unlocked)) {
            $unlocked = [];
        }
        $unlocked[] = $topic_id;
        update_user_meta($user_id, 'aksrt_unlocked_topics', array_values(array_unique(array_map('intval', $unlocked))));
    }

    private function is_coupon_allowed(int $topic_id): bool {
        return (int) get_post_meta($topic_id, '_aksrt_topic_coupon_s', true) === 1;
    }

    /**
     * VIP list price → coupon → payable. No affiliate rebate on topics.
     *
     * @param array<string,mixed> $priced
     * @return array|WP_Error
     */
    private function apply_topic_cash_discounts(array $priced, int $topic_id, int $user_id, string $coupon_code = '', bool $soft_coupon = false) {
        $list_amount = round(max(0.0, (float) ($priced['amount'] ?? 0)), 2);
        $pay = $list_amount;
        $coupon_discount = 0.0;
        $coupon_meta = [];
        $coupon_error = '';
        $coupon_code = sanitize_text_field($coupon_code);

        if ($coupon_code !== '') {
            if (!$this->is_coupon_allowed($topic_id)) {
                $err = new WP_Error('aksrt_coupon_not_allowed', __('当前主题不支持优惠码。', 'aksrt'), ['status' => 400]);
                if (!$soft_coupon) {
                    return $err;
                }
                $coupon_error = $err->get_error_message();
                $coupon_code = '';
            } elseif (!class_exists('AKSRT_Coupon')) {
                $err = new WP_Error('aksrt_coupon_unavailable', __('优惠券系统不可用。', 'aksrt'), ['status' => 500]);
                if (!$soft_coupon) {
                    return $err;
                }
                $coupon_error = $err->get_error_message();
                $coupon_code = '';
            } else {
                $result = AKSRT_Coupon::get_instance()->validate($coupon_code, $pay, [
                    'user_id'     => max(0, $user_id),
                    'product_ids' => [$topic_id],
                    'context'     => 'topic',
                ]);
                if (empty($result['valid'])) {
                    $err = new WP_Error(
                        'aksrt_coupon_error',
                        (string) ($result['message'] ?? __('优惠码不可用。', 'aksrt')),
                        ['status' => 400]
                    );
                    if (!$soft_coupon) {
                        return $err;
                    }
                    $coupon_error = $err->get_error_message();
                    $coupon_code = '';
                } else {
                    $coupon_discount = round(max(0.0, (float) ($result['discount'] ?? 0)), 2);
                    if ($coupon_discount > $pay) {
                        $coupon_discount = $pay;
                    }
                    $pay = round(max(0.0, $pay - $coupon_discount), 2);
                    $c = is_array($result['coupon'] ?? null) ? $result['coupon'] : [];
                    $coupon_meta = [
                        'id' => (int) ($c['id'] ?? 0),
                        'code' => (string) ($c['code'] ?? $coupon_code),
                        'type' => (string) ($c['type'] ?? ''),
                        'value' => (float) ($c['value'] ?? 0),
                        'discount' => $coupon_discount,
                    ];
                    $coupon_code = (string) $coupon_meta['code'];
                }
            }
        }

        return [
            'list_amount' => $list_amount,
            'coupon_discount' => $coupon_discount,
            'coupon' => $coupon_meta,
            'coupon_code' => $coupon_code,
            'coupon_error' => $coupon_error,
            'payable' => round(max(0.0, $pay), 2),
        ];
    }

    /**
     * Burn coupon after paid (idempotent via coupon_usage.order_number).
     */
    private function finalize_topic_order_side_effects(string $order_number, array $order): void {
        $meta = $this->decode_order_note_meta($order);
        if (empty($meta['topic_pay'])) {
            return;
        }
        if (($meta['pay_modo'] ?? '') === 'points') {
            return;
        }

        $buyer_id = (int) ($order['user_id'] ?? 0);
        $coupon = is_array($meta['coupon'] ?? null) ? $meta['coupon'] : [];
        $coupon_code = sanitize_text_field((string) ($coupon['code'] ?? $meta['coupon_code'] ?? ''));
        $coupon_discount = (float) ($meta['coupon_discount'] ?? $meta['discount'] ?? ($coupon['discount'] ?? 0));
        if ($coupon_code === '' || !class_exists('AKSRT_Coupon') || $this->coupon_usage_exists($order_number)) {
            return;
        }

        $coupon_api = AKSRT_Coupon::get_instance();
        $coupon_api->use_coupon($coupon_code);
        $validated = $coupon_api->validate($coupon_code, max(0.01, $coupon_discount), ['user_id' => $buyer_id]);
        $coupon_id = (int) ($validated['coupon']['id'] ?? $coupon['id'] ?? 0);
        if ($coupon_id <= 0 && !empty($coupon['id'])) {
            $coupon_id = (int) $coupon['id'];
        }
        if ($coupon_id > 0) {
            $coupon_api->log_usage($coupon_id, max(0, $buyer_id), $order_number, max(0.0, $coupon_discount));
        }
    }

    private function coupon_usage_exists(string $order_number): bool {
        if ($order_number === '' || !class_exists('AKSRT_DB_Migrator')) {
            return false;
        }
        global $wpdb;
        $table = AKSRT_DB_Migrator::table('coupon_usage');
        if ($table === '') {
            return false;
        }
        $found = $wpdb->get_var($wpdb->prepare(
            "SELECT id FROM {$table} WHERE order_number = %s LIMIT 1",
            $order_number
        ));
        return !empty($found);
    }

    /**
     * Free VIP or free-after-discount paid order.
     *
     * @param array{
     *   list_amount?:float,
     *   payable?:float,
     *   coupon_code?:string,
     *   coupon_discount?:float,
     *   coupon?:array,
     *   message?:string,
     *   paid_note?:string
     * } $opts
     * @return array|WP_Error
     */
    private function create_free_paid_order(int $topic_id, int $user_id, WP_Post $post, array $priced, array $opts = []) {
        $list_amount = round((float) ($opts['list_amount'] ?? 0), 2);
        $payable = round((float) ($opts['payable'] ?? 0), 2);
        $coupon_code = sanitize_text_field((string) ($opts['coupon_code'] ?? ''));
        $coupon_discount = round((float) ($opts['coupon_discount'] ?? 0), 2);
        $coupon_meta = is_array($opts['coupon'] ?? null) ? $opts['coupon'] : [];
        $message = (string) ($opts['message'] ?? __('VIP 免费解锁成功', 'aksrt'));
        $paid_note = (string) ($opts['paid_note'] ?? __('VIP 免费解锁主题。', 'aksrt'));

        if (!class_exists('AKSRT_Order') || !class_exists('AKSRT_Order_Repository')) {
            $this->mark_unlocked($user_id, $topic_id);
            return [
                'success' => true,
                'data' => [
                    'order_number' => '',
                    'amount' => 0,
                    'pay_modo' => '0',
                    'free' => true,
                    'message' => $message,
                    'reload' => true,
                ],
            ];
        }

        $note = wp_json_encode([
            'topic_pay' => 1,
            'topic_id' => $topic_id,
            'pay_modo' => '0',
            'vip_level' => (int) ($priced['vip_level'] ?? 0),
            'base' => (float) ($priced['base'] ?? 0),
            'list_amount' => $list_amount,
            'amount' => $payable,
            'payable' => $payable,
            'coupon_code' => $coupon_code,
            'coupon_discount' => $coupon_discount,
            'coupon' => $coupon_meta,
            'free' => 1,
            'ip_address' => function_exists('aksrt_pay_client_ip') ? aksrt_pay_client_ip() : (string) ($_SERVER['REMOTE_ADDR'] ?? ''),
        ], JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);

        $order_number = AKSRT_Order_Repository::get_instance()->create([
            'user_id' => $user_id,
            'product_type' => AKSRT_Domain_Model::ORDER_PRODUCT_RESOURCE,
            'product_id' => $topic_id,
            'amount' => 0.0,
            'currency' => 'CNY',
            'status' => AKSRT_Order::STATUS_PENDING,
            'payment_method' => 'free',
            'note' => is_string($note) ? $note : '',
            'expires_at' => gmdate('Y-m-d H:i:s', time() + 30 * MINUTE_IN_SECONDS),
        ]);

        if ($order_number === '') {
            $this->mark_unlocked($user_id, $topic_id);
            return [
                'success' => true,
                'data' => [
                    'order_number' => '',
                    'amount' => 0,
                    'free' => true,
                    'message' => $message,
                    'reload' => true,
                ],
            ];
        }

        $paid = AKSRT_Order::get_instance()->update_status($order_number, AKSRT_Order::STATUS_PAID, [
            'payment_method' => 'free',
            'payment_transaction_id' => 'free_' . $order_number,
            'note' => $paid_note,
        ]);
        if (!$paid) {
            return new WP_Error('aksrt_order_confirm_failed', __('订单确认失败。', 'aksrt'), ['status' => 500]);
        }

        $this->mark_unlocked($user_id, $topic_id);

        return [
            'success' => true,
            'data' => [
                'order_number' => $order_number,
                'amount' => 0,
                'pay_modo' => '0',
                'free' => true,
                'message' => $message,
                'reload' => true,
            ],
        ];
    }

    private function find_pending_topic_order(int $user_id, int $topic_id): ?array {
        if ($user_id <= 0 || $topic_id <= 0 || !class_exists('AKSRT_Order_Repository')) {
            return null;
        }
        $orders = AKSRT_Order_Repository::get_instance()->get_user_orders($user_id, [
            'product_type' => AKSRT_Domain_Model::ORDER_PRODUCT_RESOURCE,
            'status' => AKSRT_Domain_Model::ORDER_STATUS_PENDING,
            'limit' => 20,
            'offset' => 0,
        ]);
        foreach ($orders as $order) {
            if ((int) ($order['product_id'] ?? 0) !== $topic_id) {
                continue;
            }
            $meta = $this->decode_order_note_meta($order);
            if (!empty($meta['topic_pay']) || $this->is_forum_topic_id($topic_id)) {
                return $order;
            }
        }
        return null;
    }

    private function is_forum_topic_id(int $topic_id): bool {
        $post = get_post($topic_id);
        return $post instanceof WP_Post && $post->post_type === 'aksrt_forum_topic';
    }

    private function decode_order_note_meta(array $order): array {
        $note = (string) ($order['note'] ?? '');
        if ($note === '') {
            return [];
        }
        $decoded = json_decode($note, true);
        return is_array($decoded) ? $decoded : [];
    }
}