// 认证 BLoC — 管理用户登录状态和认证流程
//
// 状态机: AuthInitial → AuthLoading → Unauthenticated/Authenticated
//                                     ↕
//                                  Authenticating → Authenticated/AuthError

import 'package:dio/dio.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:logger/logger.dart';

import '../../../data/models/auth_token.dart';
import '../../../data/models/user.dart';
import '../../../data/remote/api_client.dart';
import '../../../data/repositories/auth_repository.dart';
import '../../../data/repositories/class_repository.dart';

part 'auth_event.dart';
part 'auth_state.dart';

/// 认证 BLoC — 处理所有认证相关的状态转换
class AuthBloc extends Bloc<AuthEvent, AuthState> {
  final AuthRepository _authRepository;
  final ClassRepository? _classRepository;
  final Logger _logger = Logger(printer: PrettyPrinter(methodCount: 0));

  AuthBloc({
    required AuthRepository authRepository,
    ClassRepository? classRepository,
  })  : _authRepository = authRepository,
        _classRepository = classRepository,
        super(const AuthInitial()) {
    // 注册事件处理器
    on<AppStarted>(_onAppStarted);
    on<LoginRequested>(_onLoginRequested);
    on<RegisterRequested>(_onRegisterRequested);
    on<RoleSelected>(_onRoleSelected);
    on<ParentalConsentAccepted>(_onParentalConsentAccepted);
    on<ClassCodeSubmitted>(_onClassCodeSubmitted);
    on<LogoutRequested>(_onLogoutRequested);
    on<TokenRefreshed>(_onTokenRefreshed);
    on<AuthExpired>(_onAuthExpired);
  }

  /// App 启动 — 从本地存储恢复认证状态
  Future<void> _onAppStarted(
    AppStarted event,
    Emitter<AuthState> emit,
  ) async {
    emit(const AuthLoading());
    try {
      final user = await _authRepository.restoreAuth();
      if (user != null) {
        emit(Authenticated(
          user: user,
          needsRoleSelection: !user.hasRole,
        ));
      } else {
        emit(const Unauthenticated());
      }
    } catch (e) {
      _logger.e('恢复认证状态失败: $e');
      emit(const Unauthenticated());
    }
  }

  /// 用户登录
  Future<void> _onLoginRequested(
    LoginRequested event,
    Emitter<AuthState> emit,
  ) async {
    emit(const Authenticating());
    try {
      final user = await _authRepository.login(
        username: event.username,
        password: event.password,
      );
      emit(Authenticated(
        user: user,
        needsRoleSelection: !user.hasRole,
      ));
    } on AuthException catch (e) {
      _logger.w('登录失败: ${e.message}');
      emit(AuthError(e.message));
    } on OfflineException {
      emit(const AuthError('网络不可用，请检查网络连接', retryable: true));
    } catch (e) {
      _logger.e('登录异常: $e');
      emit(const AuthError('登录失败，请稍后重试'));
    }
  }

  /// 用户注册
  Future<void> _onRegisterRequested(
    RegisterRequested event,
    Emitter<AuthState> emit,
  ) async {
    emit(const Authenticating(isRegister: true));
    try {
      final user = await _authRepository.register(
        username: event.username,
        password: event.password,
        displayName: event.displayName,
      );
      // 注册成功后需要选择角色
      emit(Authenticated(
        user: user,
        needsRoleSelection: true,
      ));
    } on AuthException catch (e) {
      _logger.w('注册失败: ${e.message}');
      emit(AuthError(e.message));
    } on OfflineException {
      emit(const AuthError('网络不可用，请检查网络连接', retryable: true));
    } catch (e) {
      _logger.e('注册异常: $e');
      emit(const AuthError('注册失败，请稍后重试'));
    }
  }

  /// 用户选择角色
  Future<void> _onRoleSelected(
    RoleSelected event,
    Emitter<AuthState> emit,
  ) async {
    final currentState = state;
    if (currentState is! Authenticated) return;

    // 学生角色需要先经过家长同意确认（PIPL 第28条）
    final needsParentalConsent = event.role == UserRoleType.student;

    // 根据角色决定下一步
    final needsClassCode =
        event.role == UserRoleType.student || event.role == UserRoleType.parent;

    emit(currentState.copyWith(
      needsRoleSelection: false,
      needsParentalConsent: needsParentalConsent,
      needsClassCode: needsClassCode && !needsParentalConsent,
      selectedRole: event.role,
    ));

    _logger.i('角色选择: ${event.role.name}, 需要家长同意: $needsParentalConsent');
  }

  /// 家长/监护人同意信息收集（PIPL 合规）
  Future<void> _onParentalConsentAccepted(
    ParentalConsentAccepted event,
    Emitter<AuthState> emit,
  ) async {
    final currentState = state;
    if (currentState is! Authenticated) return;

    _logger.i('家长同意已确认: ${event.consentAt}');

    emit(currentState.copyWith(
      needsParentalConsent: false,
      needsClassCode: true,
      parentalConsentAt: event.consentAt,
    ));
  }

  /// 班级码加入
  Future<void> _onClassCodeSubmitted(
    ClassCodeSubmitted event,
    Emitter<AuthState> emit,
  ) async {
    final currentState = state;
    if (currentState is! Authenticated) return;

    // 如果没有 ClassRepository（离线模式），直接跳过
    final classRepo = _classRepository;
    if (classRepo == null) {
      _logger.w('ClassRepository 不可用，跳过班级码验证');
      emit(currentState.copyWith(needsClassCode: false));
      return;
    }

    emit(currentState.copyWith(isLoading: true));

    try {
      // 调用后端 API 验证班级码并加入班级
      await classRepo.joinClass(
        event.classCode,
        nickname: currentState.user.displayName,
      );

      // 成功 — 清除班级码需求
      emit(currentState.copyWith(
        needsClassCode: false,
        isLoading: false,
      ));

      _logger.i('班级码加入成功: ${event.classCode}');
    } on DioException catch (e) {
      final statusCode = e.response?.statusCode;
      String errorMessage = '加入班级失败，请重试';

      if (statusCode == 400) {
        // 班级码无效或已过期
        final body = e.response?.data;
        if (body is Map && body['message'] is String) {
          errorMessage = body['message'] as String;
        } else {
          errorMessage = '班级码无效，请检查后重新输入';
        }
      } else if (statusCode == 429) {
        // 尝试次数过多 — 锁定
        errorMessage = '尝试次数过多，请等待 30 分钟后再试';
      }

      _logger.w('班级码验证失败 ($statusCode): $errorMessage');
      emit(currentState.copyWith(
        isLoading: false,
        classCodeError: errorMessage,
      ));
    } on OfflineException {
      emit(currentState.copyWith(
        isLoading: false,
        classCodeError: '网络不可用，请检查网络后重试',
      ));
    } catch (e) {
      _logger.e('班级码验证异常: $e');
      emit(currentState.copyWith(
        isLoading: false,
        classCodeError: '加入班级失败，请稍后重试',
      ));
    }
  }

  /// 用户登出
  Future<void> _onLogoutRequested(
    LogoutRequested event,
    Emitter<AuthState> emit,
  ) async {
    try {
      await _authRepository.logout();
    } catch (e) {
      _logger.w('登出失败（忽略）: $e');
    }
    emit(const Unauthenticated());
  }

  /// 令牌刷新成功
  Future<void> _onTokenRefreshed(
    TokenRefreshed event,
    Emitter<AuthState> emit,
  ) async {
    _logger.d('令牌已刷新');
    // 不改变当前状态，仅更新令牌
  }

  /// 认证过期（401 拦截器触发）
  Future<void> _onAuthExpired(
    AuthExpired event,
    Emitter<AuthState> emit,
  ) async {
    _logger.w('认证过期，需要重新登录');
    emit(const Unauthenticated());
  }
}