import 'package:flutter/foundation.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:shared_preferences/shared_preferences.dart';

class AuthService extends ChangeNotifier {
  final FirebaseAuth _auth = FirebaseAuth.instance;
  User? _user;
  bool _isCommunityUnlocked = false;

  static const String _prefKeyUnlocked = 'community_unlocked';
  static const String defaultCommunityCode = 'oggau';

  User? get user => _user;
  bool get isAuthenticated => _user != null;
  bool get isAnonymous => _user?.isAnonymous ?? true;
  bool get isRegisteredUser => _user != null && !_user!.isAnonymous;
  bool get isCommunityUnlocked => _isCommunityUnlocked || isRegisteredUser;
  String? get email => _user?.email;
  String? get displayName => _user?.displayName;

  AuthService() {
    _initAuth();
  }

  Future<void> _initAuth() async {
    final prefs = await SharedPreferences.getInstance();
    _isCommunityUnlocked = prefs.getBool(_prefKeyUnlocked) ?? false;

    _auth.authStateChanges().listen((User? user) {
      _user = user;
      notifyListeners();
    });

    if (_user == null && _isCommunityUnlocked) {
      await signInAnonymously();
    }
  }

  /// Verifies community access code
  Future<bool> verifyCommunityCode(String enteredCode) async {
    final cleanCode = enteredCode.trim().toLowerCase();
    if (cleanCode == defaultCommunityCode ||
        cleanCode == 'oggau2024' ||
        cleanCode == 'oggau7063') {
      _isCommunityUnlocked = true;
      final prefs = await SharedPreferences.getInstance();
      await prefs.setBool(_prefKeyUnlocked, true);
      if (_user == null) {
        await signInAnonymously();
      }
      notifyListeners();
      return true;
    }
    return false;
  }

  /// Lock community access and log out
  Future<void> lockCommunityAccess() async {
    _isCommunityUnlocked = false;
    final prefs = await SharedPreferences.getInstance();
    await prefs.setBool(_prefKeyUnlocked, false);
    await signOut();
    notifyListeners();
  }

  /// Sign in with Email and Password
  Future<String?> signInWithEmail(String email, String password) async {
    try {
      final credential = await _auth.signInWithEmailAndPassword(
        email: email.trim(),
        password: password,
      );
      _user = credential.user;
      notifyListeners();
      return null; // success
    } on FirebaseAuthException catch (e) {
      return _getLocalizedErrorMessage(e.code);
    } catch (e) {
      return 'Ein unerwarteter Fehler ist aufgetreten: $e';
    }
  }

  /// Sign up with Email, Password, and Full Name
  Future<String?> signUpWithEmail({
    required String email,
    required String password,
    required String name,
  }) async {
    try {
      final credential = await _auth.createUserWithEmailAndPassword(
        email: email.trim(),
        password: password,
      );
      _user = credential.user;
      if (_user != null && name.isNotEmpty) {
        await _user!.updateDisplayName(name.trim());
      }
      notifyListeners();
      return null; // success
    } on FirebaseAuthException catch (e) {
      return _getLocalizedErrorMessage(e.code);
    } catch (e) {
      return 'Ein unerwarteter Fehler ist aufgetreten: $e';
    }
  }

  /// Send password reset email
  Future<String?> sendPasswordReset(String email) async {
    try {
      await _auth.sendPasswordResetEmail(email: email.trim());
      return null; // success
    } on FirebaseAuthException catch (e) {
      return _getLocalizedErrorMessage(e.code);
    } catch (e) {
      return 'Fehler beim Senden der E-Mail: $e';
    }
  }

  /// Anonymous login
  Future<void> signInAnonymously() async {
    try {
      await _auth.signInAnonymously();
    } catch (e) {
      if (kDebugMode) {
        debugPrint('Sign in anonymously error: $e');
      }
    }
  }

  /// Sign out
  Future<void> signOut() async {
    try {
      await _auth.signOut();
    } catch (e) {
      if (kDebugMode) {
        debugPrint('Sign out error: $e');
      }
    }
  }

  String _getLocalizedErrorMessage(String code) {
    switch (code) {
      case 'user-not-found':
        return 'Kein Benutzer mit dieser E-Mail-Adresse gefunden.';
      case 'wrong-password':
      case 'invalid-credential':
        return 'Falsches Passwort oder ungültige Anmeldedaten.';
      case 'email-already-in-use':
        return 'Diese E-Mail-Adresse wird bereits für ein Konto verwendet.';
      case 'invalid-email':
        return 'Bitte gib eine gültige E-Mail-Adresse ein.';
      case 'weak-password':
        return 'Das Passwort ist zu schwach (mindestens 6 Zeichen erforderlich).';
      case 'too-many-requests':
        return 'Zu viele fehlgeschlagene Versuche. Bitte warte kurz.';
      case 'network-request-failed':
        return 'Keine Internetverbindung vorhanden.';
      default:
        return 'Authentifizierungsfehler ($code).';
    }
  }
}