import 'package:dio/dio.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:shared_preferences/shared_preferences.dart';
import '../config/app_config.dart';
import '../config/app_constants.dart';

const _kAccessToken = 'access_token';
const _kRefreshToken = 'refresh_token';
const _kUserId = 'user_id';
const _kUsername = 'username';
const _kRealName = 'real_name';
const _kShopNo = 'shop_no';
const _kShopId = 'shop_id';
const _kRole = 'role';

class AuthUser {
  final String accessToken;
  final String refreshToken;
  final int id;
  final String username;
  final String realName;
  final String shopNo;
  final int shopId;
  final String role;

  const AuthUser({
    required this.accessToken,
    required this.refreshToken,
    this.id = 0,
    required this.username,
    required this.realName,
    required this.shopNo,
    required this.shopId,
    this.role = 'operator',
  });

  // Kept for ApiClient compatibility
  String get token => accessToken;
}

class AuthState {
  final AuthUser? user;
  final bool initialized;
  const AuthState({this.user, this.initialized = false});
  bool get isLoggedIn => user != null;
}

class AuthNotifier extends StateNotifier<AuthState> {
  AuthNotifier() : super(const AuthState());

  /// 会话代号：每次 login/logout 自增，使「上一会话」遗留的异步持久化写入失效。
  /// 续期写回（updateAccessToken）是 fire-and-forget，若在并发登出清空 token 之后
  /// 才落盘，会把已失效的 token 重新写回；持有此代号即可在写入前丢弃过期操作。
  int _sessionGen = 0;

  /// 串行化 SharedPreferences 写入：保证 login / updateAccessToken / logout 的持久化
  /// 按调用顺序落盘，杜绝并发交错（如续期写入与登出 remove 交叉）。
  Future<void> _storageQueue = Future.value();

  Future<void> _runStorage(Future<void> Function() op) {
    final next = _storageQueue.then((_) => op());
    // 吞掉单次写入异常，避免队列被卡死。
    _storageQueue = next.catchError((_) {});
    return next;
  }

  /// Called at app startup to restore persisted session.
  Future<void> restore() async {
    try {
      final prefs = await SharedPreferences.getInstance();
      final accessToken = prefs.getString(_kAccessToken);
      final refreshToken = prefs.getString(_kRefreshToken);
      final username = prefs.getString(_kUsername);
      final realName = prefs.getString(_kRealName);
      final shopNo = prefs.getString(_kShopNo);
      final shopIdStr = prefs.getString(_kShopId);

      final role = prefs.getString(_kRole);
      final userId = prefs.getInt(_kUserId) ?? 0;
      if (accessToken != null && refreshToken != null && username != null) {
        state = AuthState(
          initialized: true,
          user: AuthUser(
            accessToken: accessToken,
            refreshToken: refreshToken,
            id: userId,
            username: username,
            realName: realName ?? username,
            shopNo: shopNo ?? '',
            shopId: int.tryParse(shopIdStr ?? '') ?? 0,
            role: role ?? 'operator',
          ),
        );
        return;
      }
    } catch (_) {
      // Storage unavailable — fall through to logged-out state
    }
    state = const AuthState(initialized: true);
  }

  Future<void> login(AuthUser user) async {
    debugPrint('[Auth] login() called, username=${user.username} shopId=${user.shopId}');
    final gen = ++_sessionGen;
    await _runStorage(() async {
      if (gen != _sessionGen) return; // 期间又发生 login/logout → 放弃这次写盘
      final prefs = await SharedPreferences.getInstance();
      await prefs.setString(_kAccessToken, user.accessToken);
      await prefs.setString(_kRefreshToken, user.refreshToken);
      await prefs.setInt(_kUserId, user.id);
      await prefs.setString(_kUsername, user.username);
      await prefs.setString(_kRealName, user.realName);
      await prefs.setString(_kShopNo, user.shopNo);
      await prefs.setString(_kShopId, user.shopId.toString());
      await prefs.setString(_kRole, user.role);
    });
    state = AuthState(initialized: true, user: user);
    debugPrint('[Auth] login() state set, isLoggedIn=${state.isLoggedIn}');
  }

  /// 续期后写回令牌。后端会**轮换 refresh token**（jti 轮换 + 盗用检测），
  /// 因此必须连同新的 refresh token 一起持久化；若仍沿用旧 refresh token，
  /// 下次续期会重放已被取代的 jti，触发盗用检测吊销整条会话，导致被强制登出。
  /// [newRefreshToken] 省略（如旧调用方）时保留原 refresh token。
  void updateAccessToken(String newToken, [String? newRefreshToken]) {
    if (state.user == null) return;
    final gen = _sessionGen;
    final refreshToken = newRefreshToken ?? state.user!.refreshToken;
    // fire-and-forget，但经队列串行 + 代号守卫：若落盘前发生过登出/重登，丢弃此次写入，
    // 避免把已失效的 token 写回 SharedPreferences。
    _runStorage(() async {
      if (gen != _sessionGen) return;
      final prefs = await SharedPreferences.getInstance();
      await prefs.setString(_kAccessToken, newToken);
      await prefs.setString(_kRefreshToken, refreshToken);
    });
    state = AuthState(
      initialized: true,
      user: AuthUser(
        accessToken: newToken,
        refreshToken: refreshToken,
        id: state.user!.id,
        username: state.user!.username,
        realName: state.user!.realName,
        shopNo: state.user!.shopNo,
        shopId: state.user!.shopId,
        role: state.user!.role,
      ),
    );
  }

  Future<void> logout() async {
    debugPrint('[Auth] logout() called! stack: ${StackTrace.current}');
    final token = state.user?.accessToken;
    // 先作废在途的令牌持久化并立即本地登出，使任何并发的续期写入在落盘前被丢弃。
    _sessionGen++;
    state = const AuthState(initialized: true);
    // 尽力通知后端撤销当前会话（离线/失败均忽略，不阻塞本地登出）
    if (token != null && token.isNotEmpty) {
      try {
        await Dio(BaseOptions(
          baseUrl: AppConfig.apiBaseUrl,
          connectTimeout: AppConstants.authProbeTimeout,
          receiveTimeout: AppConstants.authProbeTimeout,
          headers: {'Authorization': 'Bearer $token'},
        )).post('/auth/logout');
      } catch (_) {
        // ignore: 后端不可达或会话已失效都无所谓
      }
    }
    // 经队列串行清空 token，排在任何先前入队的续期写入之后，确保最终为已登出状态。
    await _runStorage(() async {
      final prefs = await SharedPreferences.getInstance();
      await prefs.remove(_kAccessToken);
      await prefs.remove(_kRefreshToken);
      await prefs.remove(_kUserId);
      await prefs.remove(_kUsername);
      await prefs.remove(_kRealName);
      await prefs.remove(_kShopNo);
      await prefs.remove(_kShopId);
      await prefs.remove(_kRole);
    });
  }
}

final authStateProvider = StateNotifierProvider<AuthNotifier, AuthState>(
  (ref) => AuthNotifier(),
);

/// 会话结束提示语（被踢下线 / 会话失效）。登录页监听后弹出提示并清空。
final sessionEndedMessageProvider = StateProvider<String?>((ref) => null);

/// 全局轻提示（如写请求被后端 403 拒绝时的原因说明）。
/// app_shell 监听后 showSnackBar 并清空，避免各业务层各自处理。
final apiMessageProvider = StateProvider<String?>((ref) => null);

/// 当前登录用户是否为只读角色（role == 'readonly'）。
/// 只读用户禁止任何写操作：UI 据此隐藏新增/编辑/删除/审核等按钮，
/// 后端亦有 middleware.ReadOnly() 兜底返回 403。
final isReadonlyProvider = Provider<bool>((ref) {
  final role = ref.watch(authStateProvider.select((s) => s.user?.role));
  return role == 'readonly';
});

/// 当前登录用户是否具备管理员权限（admin 或 superadmin）。
/// 与后端 middleware.AdminOnly() 一致（两者皆放行），用于「撤回审核中单据」等操作。
final isAdminProvider = Provider<bool>((ref) {
  final role = ref.watch(authStateProvider.select((s) => s.user?.role));
  return role == 'admin' || role == 'superadmin';
});

/// 当前登录用户 id（未登录为 0）。用于「撤回本人单据」等需要判断单据归属的场景。
final currentUserIdProvider = Provider<int>((ref) {
  return ref.watch(authStateProvider.select((s) => s.user?.id)) ?? 0;
});