// payment_provider.dart — 支付流状态机:选档下单 → 等待支付(轮询查单)→ 成功/失败。
// 轮询成功判据是 server 的 activated(webhook 已开通),不是 pay 的 succeeded——
// 保证用户看到「成功」时权益一定已到账。
import 'dart:async';
import 'dart:io' show Platform;

import 'package:flutter/foundation.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../models/payment.dart';
import '../services/auth_api.dart';
import '../services/payment_api.dart';
import 'account_providers.dart';

final paymentApiProvider = Provider<PaymentApi>(
  (ref) => PaymentApi(ref.watch(apiClientProvider)),
);

final payCatalogProvider = FutureProvider<List<PayCatalogItem>>(
  (ref) => ref.watch(paymentApiProvider).catalog(),
);

enum PaymentPhase { idle, creating, awaitingPayment, succeeded, failed }

@immutable
class PaymentFlowState {
  const PaymentFlowState({
    this.phase = PaymentPhase.idle,
    this.item,
    this.method = '',
    this.order,
    this.status,
    this.errorZh,
    this.errorEn,
  });

  final PaymentPhase phase;
  final PayCatalogItem? item;
  final String method; // alipay | crypto
  final PayOrder? order;
  final PayOrderStatus? status;
  final String? errorZh;
  final String? errorEn;

  PaymentFlowState copyWith({
    PaymentPhase? phase,
    PayCatalogItem? item,
    String? method,
    PayOrder? order,
    PayOrderStatus? status,
    String? errorZh,
    String? errorEn,
  }) =>
      PaymentFlowState(
        phase: phase ?? this.phase,
        item: item ?? this.item,
        method: method ?? this.method,
        order: order ?? this.order,
        status: status ?? this.status,
        errorZh: errorZh,
        errorEn: errorEn,
      );
}

class PaymentFlowController extends StateNotifier<PaymentFlowState> {
  PaymentFlowController(Ref ref) : _ref = ref, super(const PaymentFlowState());

  /// 测试专用 fixture:直接给定固定状态,`_ref` 留空、不发网络、不起 Timer
  /// (widget 测试用来渲染某一支付阶段的界面,不驱动状态机)。[cancel] 对
  /// `_ref == null` 短路安全——支付页 dispose 时无条件可调,不炸 fixture。
  @visibleForTesting
  PaymentFlowController.fixed(super.state) : _ref = null;

  final Ref? _ref;
  Timer? _poll;
  bool _polling = false; // 再入保护(轮询慢于间隔时跳过本拍)

  static const _pollInterval = Duration(seconds: 3);

  bool get _isMobile {
    if (kIsWeb) return false;
    return Platform.isAndroid || Platform.isIOS;
  }

  Map<String, String> _metadata(String method) =>
      method == 'alipay' ? {'is_mobile': _isMobile ? '1' : '0'} : const {};

  Future<void> start(PayCatalogItem item, String method) async {
    _stopPolling();
    state = PaymentFlowState(phase: PaymentPhase.creating, item: item, method: method);
    try {
      final order = await _ref!
          .read(paymentApiProvider)
          .createOrder(sku: item.sku, method: method, metadata: _metadata(method));
      if (!mounted) return;
      state = state.copyWith(phase: PaymentPhase.awaitingPayment, order: order);
      _startPolling();
    } on AuthApiException catch (e) {
      if (!mounted) return;
      state = state.copyWith(phase: PaymentPhase.failed, errorZh: e.messageZh, errorEn: e.messageEn);
    }
  }

  /// 换支付方式:先 retry;pay 回 409 CURRENCY_MISMATCH(跨结算币种)时,
  /// 按契约「换币种必须新单」→ cancel 旧单 + 新 method 重新下单。
  Future<void> switchMethod(String method) async {
    final item = state.item;
    final order = state.order;
    if (item == null || order == null) return;
    try {
      final next = await _ref!
          .read(paymentApiProvider)
          .retry(order.orderNo, method: method, metadata: _metadata(method));
      if (!mounted) return;
      state = state.copyWith(phase: PaymentPhase.awaitingPayment, method: method, order: next);
    } on AuthApiException catch (e) {
      if (!mounted) return;
      if (e.code == 'CURRENCY_MISMATCH') {
        try {
          await _ref!.read(paymentApiProvider).cancel(order.orderNo);
        } catch (_) {} // 旧单取消失败不阻断新单
        await start(item, method);
        return;
      }
      state = state.copyWith(phase: PaymentPhase.failed, errorZh: e.messageZh, errorEn: e.messageEn);
    }
  }

  Future<void> cancel() async {
    final order = state.order;
    final ref = _ref;
    _stopPolling();
    if (order != null && ref != null) {
      try {
        await ref.read(paymentApiProvider).cancel(order.orderNo);
      } catch (_) {}
    }
    if (mounted) state = const PaymentFlowState();
  }

  /// 只停轮询 Timer,**不**远程 cancel、**不**改 state——供支付页 dispose()
  /// 用(离开页面 ≠ 放弃订单)。与 [cancel] 区分:后者是「取消订单」按钮的显式
  /// 放弃路径(远程 cancel + 状态归 idle)。
  void stopPolling() => _stopPolling();

  /// 单拍轮询(Timer 驱动;测试直接调用,不依赖真实时钟)。
  Future<void> pollOnce() async {
    final order = state.order;
    if (order == null || _polling) return;
    _polling = true;
    try {
      final st = await _ref!.read(paymentApiProvider).orderStatus(order.orderNo);
      if (!mounted) return;
      if (st.activated) {
        _stopPolling();
        state = state.copyWith(phase: PaymentPhase.succeeded, status: st);
        // 权益已变,best-effort 刷新「我的」——仅当 meProvider 已被真实页面读取过
        // (ref.exists)才刷新;测试容器/尚未触达账户页时是空操作,不会凭空触发
        // 首次网络请求(避免打真网络 / 触发 authProvider 的后台加载)。
        if (_ref.exists(meProvider)) {
          try {
            await _ref.read(meProvider.notifier).refresh();
          } catch (_) {}
        }
      } else {
        state = state.copyWith(status: st);
      }
    } on AuthApiException {
      // 单拍失败静默,下一拍重试(网络抖动不打断等待页)。
    } finally {
      _polling = false;
    }
  }

  void _startPolling() {
    _poll?.cancel();
    _poll = Timer.periodic(_pollInterval, (_) => pollOnce());
  }

  void _stopPolling() {
    _poll?.cancel();
    _poll = null;
  }

  @override
  void dispose() {
    _stopPolling();
    super.dispose();
  }
}

final paymentFlowProvider =
    StateNotifierProvider<PaymentFlowController, PaymentFlowState>(
  (ref) => PaymentFlowController(ref),
);