/// 后端 API 服务：dio 封装 + 各支付渠道创建/查询/收银台接口
library;

import 'package:dio/dio.dart';

import '../constants.dart';
import '../models/checkout.dart';
import '../models/payment.dart';

/// 统一 API 客户端（单例）
class APIServer {
  APIServer._() : dio = Dio() {
    dio.options
      ..baseUrl = kApiBaseUrl
      ..connectTimeout = const Duration(seconds: 15)
      ..receiveTimeout = const Duration(seconds: 15)
      ..responseType = ResponseType.json;
  }

  static final APIServer _instance = APIServer._();

  /// 获取单例
  factory APIServer() => _instance;

  final Dio dio;

  /// 后端返回的是否 mock 模式（判断依据：stripe publishable_key 是否为 mock）
  static bool isMockPublishableKey(String key) =>
      key.startsWith('pk_test_mock');

  /// 发起 POST 请求并解析
  Future<T> post<T>(
    String path,
    T Function(Map<String, dynamic> json) parse, {
    Map<String, dynamic>? body,
  }) async {
    final resp = await dio.post<Map<String, dynamic>>(path, data: body);
    return parse(resp.data!);
  }

  /// 发起 GET 请求并解析
  Future<T> get<T>(
    String path,
    T Function(Map<String, dynamic> json) parse,
  ) async {
    final resp = await dio.get<Map<String, dynamic>>(path);
    return parse(resp.data!);
  }

  // ===== 支付创建 =====

  /// 创建微信支付（source: app=App支付, web=Native扫码）
  Future<WechatPaymentCreatedResponse> createWechatPayment({
    required String productId,
    String source = 'app',
  }) {
    return post<WechatPaymentCreatedResponse>(
      '/v1/payment/wechatpay/',
      WechatPaymentCreatedResponse.fromJson,
      body: {'product_id': productId, 'source': source},
    );
  }

  /// 创建支付宝支付（source: app=App支付, web=手机网站支付）
  Future<OtherPayCreatedReponse> createAlipayPayment({
    required String productId,
    String source = 'app',
  }) {
    return post<OtherPayCreatedReponse>(
      '/v1/payment/alipay/',
      OtherPayCreatedReponse.fromJson,
      body: {'product_id': productId, 'source': source},
    );
  }

  /// 创建云闪付支付（source: app=App支付返回 tn 拉起云闪付, web=手机网站跳转）
  Future<UnionPayCreatedResponse> createUnionPayPayment({
    required String productId,
    String source = 'app',
  }) {
    return post<UnionPayCreatedResponse>(
      '/v1/payment/unionpay/',
      UnionPayCreatedResponse.fromJson,
      body: {'product_id': productId, 'source': source},
    );
  }

  /// 创建 Stripe 支付（PaymentIntent）
  Future<StripePaymentCreatedResponse> createStripePayment({
    required String productId,
    String source = 'app',
    String currency = 'cny',
  }) {
    return post<StripePaymentCreatedResponse>(
      '/v1/payment/stripe/',
      StripePaymentCreatedResponse.fromJson,
      body: {
        'product_id': productId,
        'source': source,
        'currency': currency,
      },
    );
  }

  /// 创建 Apple Pay 支付（PSP 模式，响应与 Stripe 一致）
  Future<StripePaymentCreatedResponse> createApplePayment({
    required String productId,
    String source = 'app',
    String currency = 'usd',
  }) {
    return post<StripePaymentCreatedResponse>(
      '/v1/payment/apple/',
      StripePaymentCreatedResponse.fromJson,
      body: {
        'product_id': productId,
        'source': source,
        'currency': currency,
      },
    );
  }

  /// 创建 Google Pay 支付（PSP 模式，响应与 Stripe 一致）
  Future<StripePaymentCreatedResponse> createGooglePayment({
    required String productId,
    String source = 'app',
    String currency = 'usd',
  }) {
    return post<StripePaymentCreatedResponse>(
      '/v1/payment/google/',
      StripePaymentCreatedResponse.fromJson,
      body: {
        'product_id': productId,
        'source': source,
        'currency': currency,
      },
    );
  }

  // ===== 状态查询 =====

  /// 查询支付状态（最终确认 / 轮询）
  Future<PaymentStatus> queryPaymentStatus(String paymentId) {
    return get<PaymentStatus>(
      '/v1/payment/$paymentId',
      PaymentStatus.fromJson,
    );
  }

  // ===== 收银台 =====

  /// 创建网页收银台会话
  Future<CheckoutSessionResponse> createCheckoutSession({
    required String channel,
    required String productId,
    String? returnUrl,
  }) {
    return post<CheckoutSessionResponse>(
      '/v1/checkout/session',
      CheckoutSessionResponse.fromJson,
      body: {
        'channel': channel,
        'product_id': productId,
        'return_url': returnUrl,
      },
    );
  }

  /// 查询收银台会话状态
  Future<CheckoutSessionStatus> queryCheckoutStatus(String paymentId) {
    return get<CheckoutSessionStatus>(
      '/v1/checkout/session/$paymentId',
      CheckoutSessionStatus.fromJson,
    );
  }

  // ===== 商品 =====

  /// 拉取商品列表
  Future<PaymentProducts> fetchProducts() {
    return get<PaymentProducts>(
      '/v1/products',
      PaymentProducts.fromJson,
    );
  }

  // ===== Mock 模拟成功（仅后端 MOCK_MODE） =====

  /// 模拟支付成功（走与真实回调相同的幂等流程）
  Future<void> simulatePaymentSuccess(String paymentId) async {
    await dio.post<Map<String, dynamic>>(
      '/v1/payment/simulate/success',
      data: {'payment_id': paymentId},
    );
  }

  // ===== 错误解析 =====

  /// 将异常统一解析为友好中文提示
  String resolveError(Object error) {
    if (error is DioException) {
      final data = error.response?.data;
      if (data is Map) {
        final err = data['error'];
        if (err is Map && err['message'] != null) {
          return '服务端错误：${err['message']}';
        }
      }
      switch (error.type) {
        case DioExceptionType.connectionTimeout:
        case DioExceptionType.receiveTimeout:
        case DioExceptionType.sendTimeout:
          return '网络超时，请稍后重试';
        case DioExceptionType.connectionError:
          return '无法连接服务器，请检查网络或后端是否启动';
        default:
          return '请求失败：${error.message}';
      }
    }
    return error.toString();
  }
}