import 'package:dio/dio.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:flutter_web_auth_2/flutter_web_auth_2.dart';

import '../core/api_client.dart';
import '../core/env.dart';
import 'session_store.dart';

class AuthState {
  const AuthState({required this.status, this.user, this.profile, this.streakCount = 0});

  final AuthStatus status;
  final User? user;
  final Profile? profile;
  final int streakCount;

  AuthState copyWith({AuthStatus? status, User? user, Profile? profile, int? streakCount}) =>
      AuthState(
        status: status ?? this.status,
        user: user ?? this.user,
        profile: profile ?? this.profile,
        streakCount: streakCount ?? this.streakCount,
      );
}

enum AuthStatus { unknown, signedOut, noProfile, ready }

class User {
  const User({required this.id, required this.hfUsername, this.email, this.avatarUrl});
  final String id;
  final String hfUsername;
  final String? email;
  final String? avatarUrl;

  factory User.fromJson(Map<String, dynamic> j) => User(
        id: (j['id'] ?? j['hfId']) as String,
        hfUsername: j['hfUsername'] as String,
        email: j['email'] as String?,
        avatarUrl: j['avatarUrl'] as String?,
      );
}

class Profile {
  const Profile({
    required this.nativeLang,
    required this.targetLang,
    required this.targetLangs,
    required this.level,
  });
  final String nativeLang;
  final String targetLang;
  final List<String> targetLangs;
  final String level;

  factory Profile.fromJson(Map<String, dynamic> j) {
    final tg = j['targetLang'] as String;
    final list = (j['targetLangs'] as List?)?.map((e) => e.toString()).toList();
    return Profile(
      nativeLang: j['nativeLang'] as String,
      targetLang: tg,
      targetLangs: (list == null || list.isEmpty) ? [tg] : list,
      level: j['level'] as String,
    );
  }

  Map<String, dynamic> toJson() => {
        'nativeLang': nativeLang,
        'targetLang': targetLang,
        'targetLangs': targetLangs,
        'level': level,
      };

  Profile copyWith({String? nativeLang, String? targetLang, List<String>? targetLangs, String? level}) =>
      Profile(
        nativeLang: nativeLang ?? this.nativeLang,
        targetLang: targetLang ?? this.targetLang,
        targetLangs: targetLangs ?? this.targetLangs,
        level: level ?? this.level,
      );
}

class AuthController extends StateNotifier<AuthState> {
  AuthController(this._api, this._store) : super(const AuthState(status: AuthStatus.unknown)) {
    _initFromCache();
  }

  final ApiClient _api;
  final SessionStore _store;

  /// On startup: immediately restore any cached profile so the UI is not blank,
  /// then kick off a background refresh from the server.
  Future<void> _initFromCache() async {
    final token = await _store.read();
    if (token == null) {
      state = const AuthState(status: AuthStatus.signedOut);
      return;
    }
    // Try to restore profile from local cache for instant UI.
    final cached = await _store.readProfile();
    if (cached != null) {
      final profile = Profile.fromJson(cached);
      state = AuthState(status: AuthStatus.ready, profile: profile);
    }
    // Always refresh from server in the background.
    await refresh();
  }

  Future<void> refresh() async {
    final token = await _store.read();
    if (token == null) {
      state = const AuthState(status: AuthStatus.signedOut);
      return;
    }
    try {
      final res = await _api.dio.get<Map<String, dynamic>>('/api/me');
      if (res.statusCode == 200 && res.data != null) {
        final user = User.fromJson(res.data!['user'] as Map<String, dynamic>);
        final pjson = res.data!['profile'] as Map<String, dynamic>?;
        final profile = pjson == null ? null : Profile.fromJson(pjson);
        final streak = (res.data!['streakCount'] as num?)?.toInt() ?? 0;
        // Persist locally.
        if (profile != null) {
          await _store.writeProfile(profile.toJson());
        } else {
          await _store.clearProfile();
        }
        state = AuthState(
          status: profile == null ? AuthStatus.noProfile : AuthStatus.ready,
          user: user,
          profile: profile,
          streakCount: streak,
        );
      } else {
        await _store.clear();
        state = const AuthState(status: AuthStatus.signedOut);
      }
    } catch (e) {
      debugPrint('auth refresh failed: $e');
      // Keep the cached state if we already have one; only fall back to signedOut
      // if there is nothing cached.
      if (state.status == AuthStatus.unknown) {
        state = const AuthState(status: AuthStatus.signedOut);
      }
    }
  }

  Future<void> signInWithHuggingFace() async {
    final loginUrl = '${Env.apiBaseUrl}/api/auth/login?client=mobile';
    debugPrint('[auth] launching OAuth via $loginUrl (callback scheme=${Env.oauthCallbackScheme})');
    try {
      final result = await FlutterWebAuth2.authenticate(
        url: loginUrl,
        callbackUrlScheme: Env.oauthCallbackScheme,
      );
      debugPrint('[auth] received callback: $result');
      final token = Uri.parse(result).queryParameters['token'];
      if (token == null || token.isEmpty) {
        throw Exception('OAuth callback missing token: $result');
      }
      await _store.write(token);
      await refresh();
    } on DioException catch (e) {
      debugPrint('[auth] dio error during refresh: $e');
      rethrow;
    } catch (e, st) {
      debugPrint('[auth] sign-in failed: $e\n$st');
      rethrow;
    }
  }

  Future<void> signOut() async {
    await _store.clear(); // clears JWT + profile cache
    state = const AuthState(status: AuthStatus.signedOut);
  }

  Future<void> saveProfile({
    required String nativeLang,
    required String targetLang,
    required String level,
    List<String>? targetLangs,
  }) async {
    final res = await _api.dio.put<Map<String, dynamic>>(
      '/api/me/profile',
      data: {
        'nativeLang': nativeLang,
        'targetLang': targetLang,
        'level': level,
        if (targetLangs != null) 'targetLangs': targetLangs,
      },
    );
    if (res.statusCode == 200 && res.data != null) {
      final token = res.data!['token'] as String?;
      if (token != null && token.isNotEmpty) {
        await _store.write(token);
      }
      final p = Profile.fromJson(res.data!['profile'] as Map<String, dynamic>);
      await _store.writeProfile(p.toJson());
      state = state.copyWith(status: AuthStatus.ready, profile: p);
    } else {
      throw Exception((res.data?['message'] ?? res.data?['error'] ?? 'save failed').toString());
    }
  }

  /// Change only the CEFR level without a full profile re-save form.
  Future<void> updateLevel(String level) async {
    final current = state.profile;
    if (current == null) return;
    await saveProfile(
      nativeLang: current.nativeLang,
      targetLang: current.targetLang,
      targetLangs: current.targetLangs,
      level: level,
    );
  }

  /// Update the list of languages the user is actively learning.
  /// The first entry becomes the primary `targetLang`.
  Future<void> setLearningLanguages(List<String> langs) async {
    final current = state.profile;
    if (current == null || langs.isEmpty) return;
    await saveProfile(
      nativeLang: current.nativeLang,
      targetLang: langs.first,
      targetLangs: langs,
      level: current.level,
    );
  }

  /// Ping the server to register today's activity and update the streak.
  Future<void> pingStreak() async {
    try {
      final res = await _api.dio.post<Map<String, dynamic>>('/api/me/streak');
      if (res.statusCode == 200 && res.data != null) {
        final count = (res.data!['streakCount'] as num?)?.toInt() ?? state.streakCount;
        state = state.copyWith(streakCount: count);
      }
    } catch (_) {
      // streak ping is best-effort; ignore failures
    }
  }
}

final authControllerProvider = StateNotifierProvider<AuthController, AuthState>((ref) {
  final api = ref.watch(apiClientProvider);
  final store = ref.watch(sessionStoreProvider);
  return AuthController(api, store);
});