import 'dart:convert';
import 'package:flutter/foundation.dart';
import 'package:http/http.dart' as http;
import 'package:shared_preferences/shared_preferences.dart';
import '../config/app_config.dart';
import '../services/melo_logger.dart';

/// Baka-Auth Service – JWT-basierte Authentifizierung
/// Integriert mit https://baka-net.de/auth
class AuthService {
  static final AuthService _instance = AuthService._();
  factory AuthService() => _instance;
  AuthService._();

  String? _token;
  String _user = '';
  bool _initialisiert = false;

  bool get istEingeloggt => _token != null && _token!.isNotEmpty;
  String get benutzer => _user;
  String? get token => _token;

  /// Auth-Header für API-Requests
  Map<String, String> get authHeader {
    final headers = <String, String>{
      'Content-Type': 'application/json',
    };
    if (_token != null && _token!.isNotEmpty) {
      headers['Authorization'] = 'Bearer $_token';
    }
    return headers;
  }

  /// Lädt gespeicherten Token beim App-Start
  Future<void> initialisieren() async {
    if (_initialisiert) return;
    try {
      final prefs = await SharedPreferences.getInstance();
      _token = prefs.getString('baka_token');
      _user = prefs.getString('baka_user') ?? '';
      if (_token != null && _token!.isNotEmpty) {
        MeloLogger().zustand('auth_restored', {'user': _user});
      }
    } catch (e) {
      MeloLogger().fehler('auth_init', e);
    }
    _initialisiert = true;
  }

  /// Login über Baka-Auth-Server
  /// Gibt true zurück bei Erfolg, false bei Fehler
  Future<AuthResult> login(String user, String password) async {
    try {
      final response = await http
          .post(
            Uri.parse('${AppConfig.authUrl}/login'),
            headers: {'Content-Type': 'application/json'},
            body: jsonEncode({
              'username': user,
              'password': password,
            }),
          )
          .timeout(const Duration(seconds: 10));

      if (response.statusCode == 200) {
        final data = jsonDecode(response.body);
        _token = data['token'] as String?;
        _user = user;

        if (_token != null && _token!.isNotEmpty) {
          final prefs = await SharedPreferences.getInstance();
          await prefs.setString('baka_token', _token!);
          await prefs.setString('baka_user', _user);
          MeloLogger().aktion('auth_login_ok', {'user': _user});
          return AuthResult.ok;
        }
        // 200 aber kein Token → Fehler vom Server
        final serverMsg = data['message'] as String? ?? data['error'] as String? ?? 'Unbekannt';
        return AuthResult.fehlgeschlagen(serverMsg);
      }

      // Nicht-200
      String fehler = 'Login fehlgeschlagen (${response.statusCode})';

      MeloLogger().fehler('auth_login_fail', fehler);
      return AuthResult.fehlgeschlagen(fehler);
    } catch (e) {
      final msg = 'Keine Verbindung zum Auth-Server';
      MeloLogger().fehler('auth_login_error', e);
      return AuthResult.fehlgeschlagen(msg);
    }
  }

  /// Registrierung über Baka-Auth-Server
  Future<AuthResult> registrieren(String user, String password, String email) async {
    try {
      final response = await http
          .post(
            Uri.parse('${AppConfig.authUrl}/register'),
            headers: {'Content-Type': 'application/json'},
            body: jsonEncode({
              'username': user,
              'password': password,
              'email': email,
            }),
          )
          .timeout(const Duration(seconds: 10));

      if (response.statusCode == 200 || response.statusCode == 201) {
        final data = jsonDecode(response.body);
        _token = data['token'] as String?;
        _user = user;

        if (_token != null && _token!.isNotEmpty) {
          final prefs = await SharedPreferences.getInstance();
          await prefs.setString('baka_token', _token!);
          await prefs.setString('baka_user', _user);

          MeloLogger().aktion('auth_register_ok', {'user': _user});
          return AuthResult.ok;
        }
      }

      String fehler = 'Registrierung fehlgeschlagen';
      try {
        final data = jsonDecode(response.body);
        fehler = data['error'] as String? ?? fehler;
      } catch (_) {}

      return AuthResult.fehlgeschlagen(fehler);
    } catch (e) {
      return AuthResult.fehlgeschlagen('Keine Verbindung zum Server');
    }
  }

  /// Token beim Server validieren
  Future<bool> tokenPruefen() async {
    if (_token == null) return false;
    try {
      final response = await http
          .get(
            Uri.parse('${AppConfig.authUrl}/verify'),
            headers: authHeader,
          )
          .timeout(const Duration(seconds: 5));
      return response.statusCode == 200;
    } catch (_) {
      return false;
    }
  }

  /// Ausloggen – Token löschen
  Future<void> logout() async {
    _token = null;
    _user = '';
    final prefs = await SharedPreferences.getInstance();
    await prefs.remove('baka_token');
    await prefs.remove('baka_user');
    MeloLogger().aktion('auth_logout', {});
  }
}

/// Ergebnis eines Auth-Versuchs
class AuthResult {
  final bool erfolg;
  final String? fehler;

  const AuthResult._(this.erfolg, this.fehler);

  static const ok = AuthResult._(true, null);
  static AuthResult fehlgeschlagen(String msg) => AuthResult._(false, msg);
}