/// 支付编排服务：7 种支付渠道的统一入口
///
/// 统一原则（与 docs 一致）：
/// - 客户端回调结果仅做 UI 提示
/// - 最终支付状态一律以 `GET /v1/payment/{payment_id}` 后端查询为准
/// - Mock 模式（无真实商户密钥）下，微信 Native 走扫码弹窗内「模拟支付成功」，
///   网页跳转渠道走「模拟支付成功（Mock）」按钮，实现端到端演示
library;

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter_stripe/flutter_stripe.dart';
import 'package:url_launcher/url_launcher.dart';

import '../models/payment.dart';
import '../pages/wechat_qr_dialog.dart';
import '../utils/dialog.dart';
import '../utils/pay_result.dart';
import '../utils/platform.dart';
import '../utils/toast.dart';
import 'api_service.dart';
import 'platform/alipay_interface.dart';
import 'platform/stripe_flow.dart';
import 'platform/wechat_flow.dart';

/// 支付编排服务（单例）
class PayService {
  PayService._() {
    // 注册微信支付结果回调（App 启动后即可接收）
    WechatFlow.instance.onPayResult = _onWechatResult;
  }

  static final PayService instance = PayService._();

  final APIServer _api = APIServer();

  /// 微信 App 支付结果等待器（pay 拉起后阻塞直到 SDK 回调）
  Completer<int>? _wechatCompleter;

  /// 微信 SDK 回调：errCode 0=成功 / -1=失败 / -2=取消
  void _onWechatResult(int errCode, String errStr) {
    final c = _wechatCompleter;
    if (c != null && !c.isCompleted) c.complete(errCode);
  }

  /// 打开外部链接（网页支付跳转）
  Future<void> _launchUrl(String url) async {
    final ok = await launchUrl(
      Uri.parse(url),
      mode: LaunchMode.externalApplication,
    );
    if (!ok) showErrorMessage('无法打开支付页面：$url');
  }

  /// 最终状态确认：以后端查询为准（最多轮询约 12s 覆盖回调延迟），
  /// 成功后弹出「支付结果」对话框展示订单号与渠道，回到商品页。
  Future<void> _queryFinalStatus(
    BuildContext context,
    String paymentId, {
    required String channelName,
  }) async {
    for (int i = 0; i < 12; i++) {
      try {
        final status = await _api.queryPaymentStatus(paymentId);
        if (status.success) {
          if (context.mounted) {
            await showPayResultDialog(
              context,
              success: true,
              paymentId: paymentId,
              channelName: channelName,
              note: status.note,
            );
          }
          return;
        }
        if ((status.note ?? '').contains('关闭')) {
          showErrorMessage('订单已关闭：${status.note}');
          return;
        }
      } catch (_) {
        // 网络抖动重试
      }
      await Future.delayed(const Duration(seconds: 1));
    }
    // 轮询超时仍未入账：提示用户稍后查询
    showErrorMessage('支付结果确认中，请稍后在订单中查询');
  }

  /// 网页跳转支付确认弹窗
  ///
  /// 用于支付宝 WAP / 收银台跳转类渠道：
  /// - 打开支付页：真实模式，用户完成付款后回来
  /// - 模拟支付成功（Mock）：演示环境直接走通
  Future<void> _handleWebRedirect({
    required BuildContext context,
    required String url,
    required String paymentId,
    required String channelName,
  }) async {
    final choice = await showDialog<String>(
      context: context,
      builder: (ctx) => AlertDialog(
        title: const Text('网页支付'),
        content: SingleChildScrollView(
          child: Text('请在支付页面完成付款。\n\n支付单号：$paymentId\n支付地址：$url'),
        ),
        actions: [
          TextButton(
            onPressed: () => Navigator.of(ctx).pop('open'),
            child: const Text('打开支付页'),
          ),
          TextButton(
            onPressed: () => Navigator.of(ctx).pop('simulate'),
            child: const Text('模拟支付成功（Mock）'),
          ),
          TextButton(
            onPressed: () => Navigator.of(ctx).pop('cancel'),
            child: const Text('取消'),
          ),
        ],
      ),
    );

    switch (choice) {
      case 'open':
        await _launchUrl(url);
        if (!context.mounted) return;
        await _queryFinalStatus(context, paymentId, channelName: channelName);
      case 'simulate':
        startLoading(status: '模拟支付中...');
        try {
          await _api.simulatePaymentSuccess(paymentId);
          stopLoading();
          showSuccessMessage('模拟支付成功');
          if (!context.mounted) return;
          await _queryFinalStatus(context, paymentId, channelName: channelName);
        } on Exception catch (e) {
          stopLoading();
          showErrorMessage(_api.resolveError(e));
        }
      default:
        return;
    }
  }

  // ===== 1. 微信支付 =====

  /// 微信支付
  /// - 移动端：App 支付（fluwx 拉起微信）
  /// - Web/桌面：Native 扫码（二维码弹窗轮询）
  Future<void> payWithWechat(
    BuildContext context, {
    required String productId,
  }) async {
    startLoading(status: '正在发起微信支付...');
    try {
      final created = await _api.createWechatPayment(
        productId: productId,
        source: PlatformTool.isMobile ? 'app' : 'web',
      );
      stopLoading();

      if (PlatformTool.isMobile) {
        // ---- App 支付 ----
        final installed = await WechatFlow.instance.isInstalled();
        if (!installed) {
          showErrorMessage('未安装微信，请安装后重试');
          return;
        }
        final completer = _wechatCompleter = Completer<int>();
        final invoked = await WechatFlow.instance.payWith(created);
        if (!invoked) {
          _wechatCompleter = null;
          showErrorMessage('拉起微信失败');
          return;
        }
        // 等待微信 SDK 回调（超时哨兵值 -999，避免永远阻塞）
        final errCode = await completer.future
            .timeout(const Duration(seconds: 20), onTimeout: () => -999);
        _wechatCompleter = null;
        switch (errCode) {
          case WechatPayResultCode.success:
            showSuccessMessage('支付成功');
          case WechatPayResultCode.cancelled:
            showErrorMessage('已取消支付');
          case -999:
            showErrorMessage('支付结果确认中，请稍后查询');
          default:
            showErrorMessage('支付失败（$errCode）');
        }
        // 最终以后端状态为准
        if (!context.mounted) return;
        await _queryFinalStatus(context, created.paymentId,
            channelName: '微信支付');
      } else {
        // ---- Web/桌面：Native 扫码 ----
        final codeUrl = created.codeUrl;
        if (codeUrl == null || codeUrl.isEmpty) {
          showErrorMessage('未获取到支付二维码');
          return;
        }
        if (!context.mounted) return;
        await openDialog(
          context,
          builder: (_) => WechatQrDialog(
            codeUrl: codeUrl,
            paymentId: created.paymentId,
            onClose: (success) {
              // 扫码弹窗关闭后回到商品页，弹出支付结果（失败时给出提示）
              if (!success) {
                showErrorMessage('订单已关闭或未完成支付');
              }
            },
          ),
        );
      }
    } on Exception catch (e) {
      stopLoading();
      showErrorMessage(_api.resolveError(e));
    }
  }

  // ===== 2. 支付宝支付 =====

  /// 支付宝支付
  /// - 移动端：App 支付（alipay_kit 拉起支付宝）
  /// - Web：手机网站支付（后端返回 WAP 跳转链接）
  Future<void> payWithAlipay(
    BuildContext context, {
    required String productId,
  }) async {
    startLoading(status: '正在发起支付宝支付...');
    try {
      final created = await _api.createAlipayPayment(
        productId: productId,
        source: PlatformTool.isMobile ? 'app' : 'web',
      );
      stopLoading();

      if (PlatformTool.isMobile) {
        // ---- App 支付 ----
        final result = await AlipayFlow.instance.pay(created.params);
        if (result.isSuccessful) {
          showSuccessMessage('支付成功');
        } else if (result.isCancelled) {
          showErrorMessage('已取消支付');
        } else {
          showErrorMessage('支付失败：${result.memo ?? '未知错误'}');
        }
        // 最终以后端状态为准
        if (!context.mounted) return;
        await _queryFinalStatus(context, created.paymentId,
            channelName: '支付宝支付');
      } else {
        // ---- Web：WAP 跳转 ----
        final url = created.redirectUrl;
        if (url == null || url.isEmpty) {
          showErrorMessage('未获取到支付跳转链接');
          return;
        }
        if (!context.mounted) return;
        await _handleWebRedirect(
          context: context,
          url: url,
          paymentId: created.paymentId,
          channelName: '支付宝支付',
        );
      }
    } on Exception catch (e) {
      stopLoading();
      showErrorMessage(_api.resolveError(e));
    }
  }

  // ===== 3. 银联云闪付 =====

  /// 云闪付支付
  /// - 移动端：App 支付（后端返回 tn，拉起云闪付 App）
  /// - Web/桌面：手机网站跳转（银联收银台）
  Future<void> payWithUnionPay(
    BuildContext context, {
    required String productId,
  }) async {
    startLoading(status: '正在发起云闪付支付...');
    try {
      final created = await _api.createUnionPayPayment(
        productId: productId,
        source: PlatformTool.isMobile ? 'app' : 'web',
      );
      stopLoading();

      if (PlatformTool.isMobile) {
        // ---- App 支付：tn 是调起云闪付 App 的唯一凭证 ----
        final tn = created.tn;
        if (tn == null || tn.isEmpty) {
          showErrorMessage('未获取到云闪付交易流水号');
          return;
        }
        // Mock 模式：tn 以 mock_ 开头，不拉起 App，直接模拟支付成功
        if (tn.startsWith('mock_')) {
          startLoading(status: '模拟支付中...');
          await _api.simulatePaymentSuccess(created.paymentId);
          stopLoading();
          showSuccessMessage('模拟云闪付支付成功');
          if (!context.mounted) return;
          await _queryFinalStatus(context, created.paymentId,
              channelName: '云闪付');
          return;
        }
        // 真实模式：通过 uppay:// scheme 调起云闪付 App
        // （正式接入推荐集成银联官方 SDK 拉起，此处用 scheme 演示）
        final invoked = await launchUrl(
          Uri.parse('uppay://sdkpay?tn=$tn'),
          mode: LaunchMode.externalApplication,
        );
        if (!invoked) {
          showErrorMessage('拉起云闪付失败，请确认已安装云闪付 App');
          return;
        }
        // 用户支付完成后回到 App，轮询后端确认最终状态
        if (!context.mounted) return;
        await _queryFinalStatus(context, created.paymentId,
            channelName: '云闪付');
      } else {
        // ---- Web：银联收银台跳转 ----
        final url = created.redirectUrl;
        if (url == null || url.isEmpty) {
          showErrorMessage('未获取到云闪付跳转链接');
          return;
        }
        if (!context.mounted) return;
        await _handleWebRedirect(
          context: context,
          url: url,
          paymentId: created.paymentId,
          channelName: '云闪付',
        );
      }
    } on Exception catch (e) {
      stopLoading();
      showErrorMessage(_api.resolveError(e));
    }
  }

  // ===== 5. Stripe PaymentSheet =====

  /// Stripe 支付（PaymentSheet 卡片支付）
  Future<void> payWithStripe(
    BuildContext context, {
    required String productId,
  }) async {
    startLoading(status: '正在创建 Stripe 支付...');
    try {
      final created = await _api.createStripePayment(productId: productId);
      stopLoading();

      // Mock 模式（pk_test_mock）：不弹原生面板，直接模拟成功
      if (StripeFlow.isMock(created)) {
        startLoading(status: '模拟支付中...');
        await _api.simulatePaymentSuccess(created.paymentId);
        stopLoading();
        showSuccessMessage('模拟 Stripe 支付成功');
        return;
      }

      // 真实模式：弹出 PaymentSheet
      await StripeFlow.instance.presentPaymentSheet(created);
      if (!context.mounted) return;
      await _queryFinalStatus(context, created.paymentId,
          channelName: 'Stripe 支付');
    } on StripeException catch (e) {
      stopLoading();
      final cancelled = e.error.code == FailureCode.Canceled;
      showErrorMessage(
        cancelled ? '已取消支付' : '支付失败：${e.error.localizedMessage}',
      );
    } on Exception catch (e) {
      stopLoading();
      showErrorMessage(_api.resolveError(e));
    }
  }

  // ===== 6. Apple Pay =====

  /// Apple Pay（经 Stripe 确认）
  Future<void> payWithApple(
    BuildContext context, {
    required PaymentProduct product,
  }) async {
    startLoading(status: '正在创建 Apple Pay...');
    try {
      final created = await _api.createApplePayment(productId: product.id);
      stopLoading();

      if (StripeFlow.isMock(created)) {
        startLoading(status: '模拟支付中...');
        await _api.simulatePaymentSuccess(created.paymentId);
        stopLoading();
        showSuccessMessage('模拟 Apple Pay 成功');
        return;
      }

      if (!await StripeFlow.instance.isApplePaySupported()) {
        showErrorMessage('当前设备不支持 Apple Pay');
        return;
      }
      await StripeFlow.instance.confirmApplePay(
        created,
        product.name,
        product.retailPriceUSD,
      );
      if (!context.mounted) return;
      await _queryFinalStatus(context, created.paymentId,
          channelName: 'Apple Pay');
    } on StripeException catch (e) {
      stopLoading();
      showErrorMessage('Apple Pay 失败：${e.error.localizedMessage}');
    } on Exception catch (e) {
      stopLoading();
      showErrorMessage(_api.resolveError(e));
    }
  }

  // ===== 7. Google Pay =====

  /// Google Pay（经 Stripe 确认）
  Future<void> payWithGoogle(
    BuildContext context, {
    required PaymentProduct product,
  }) async {
    startLoading(status: '正在创建 Google Pay...');
    try {
      final created = await _api.createGooglePayment(productId: product.id);
      stopLoading();

      if (StripeFlow.isMock(created)) {
        startLoading(status: '模拟支付中...');
        await _api.simulatePaymentSuccess(created.paymentId);
        stopLoading();
        showSuccessMessage('模拟 Google Pay 成功');
        return;
      }

      if (!await StripeFlow.instance.isGooglePaySupported()) {
        showErrorMessage('当前设备不支持 Google Pay');
        return;
      }
      await StripeFlow.instance.confirmGooglePay(
        created,
        product.name,
        product.retailPriceUSD,
      );
      if (!context.mounted) return;
      await _queryFinalStatus(context, created.paymentId,
          channelName: 'Google Pay');
    } on StripeException catch (e) {
      stopLoading();
      showErrorMessage('Google Pay 失败：${e.error.localizedMessage}');
    } on Exception catch (e) {
      stopLoading();
      showErrorMessage(_api.resolveError(e));
    }
  }

  // ===== 8. 网页收银台 =====

  /// 网页收银台（聚合支付）
  /// - wechat：Native 扫码弹窗轮询
  /// - alipay / stripe：跳转 + 确认
  Future<void> payWithCheckout(
    BuildContext context, {
    required String channel,
    required String productId,
  }) async {
    startLoading(status: '正在创建收银台会话...');
    try {
      final session = await _api.createCheckoutSession(
        channel: channel,
        productId: productId,
      );
      stopLoading();

      if (channel == 'wechat') {
        final codeUrl = session.codeUrl;
        if (codeUrl == null || codeUrl.isEmpty) {
          showErrorMessage('未获取到支付二维码');
          return;
        }
        if (!context.mounted) return;
        await openDialog(
          context,
          builder: (_) => WechatQrDialog(
            codeUrl: codeUrl,
            paymentId: session.paymentId,
            onClose: (success) {
              // 扫码弹窗关闭后回到商品页，失败时给出提示
              if (!success) {
                showErrorMessage('订单已关闭或未完成支付');
              }
            },
          ),
        );
      } else {
        final url = session.redirectUrl;
        if (url == null || url.isEmpty) {
          showErrorMessage('未获取到支付跳转链接');
          return;
        }
        if (!context.mounted) return;
        // 收银台渠道展示名（与渠道选择弹窗一致）
        final displayName = switch (channel) {
          'wechat' => '微信支付',
          'alipay' => '支付宝支付',
          _ => 'Stripe 支付',
        };
        await _handleWebRedirect(
          context: context,
          url: url,
          paymentId: session.paymentId,
          channelName: displayName,
        );
      }
    } on Exception catch (e) {
      stopLoading();
      showErrorMessage(_api.resolveError(e));
    }
  }
}