import 'dart:convert';

import 'package:http/http.dart' as http;
import 'package:shared_preferences/shared_preferences.dart';

/// Gleiche Basis-Idee wie im React-Client (frontend/src/api/client.ts):
/// gemeinsamer JSON-Wrapper, Token aus persistentem Speicher, ApiException
/// mit HTTP-Status, damit aufrufender Code gezielt reagieren kann (z.B. 409
/// bei Objekt-Sperre).
class ApiException implements Exception {
  final int status;
  final dynamic detail;
  ApiException(this.status, this.detail);

  @override
  String toString() => 'ApiException($status, $detail)';
}

class ApiClient {
  ApiClient({required this.baseUrl, http.Client? httpClient}) : _http = httpClient ?? http.Client();

  final String baseUrl;
  final http.Client _http;
  String? _token;

  Future<void> ladeToken() async {
    final prefs = await SharedPreferences.getInstance();
    _token = prefs.getString('mabea_token');
  }

  Future<void> setzeToken(String? token) async {
    _token = token;
    final prefs = await SharedPreferences.getInstance();
    if (token == null) {
      await prefs.remove('mabea_token');
    } else {
      await prefs.setString('mabea_token', token);
    }
  }

  bool get istEingeloggt => _token != null;

  Future<String> login(String username, String password) async {
    final response = await _http.post(
      Uri.parse('$baseUrl/auth/login'),
      headers: {'Content-Type': 'application/x-www-form-urlencoded'},
      body: {'username': username, 'password': password},
    );
    if (response.statusCode != 200) {
      throw ApiException(response.statusCode, _tryDecode(response.body));
    }
    final data = jsonDecode(response.body) as Map<String, dynamic>;
    final token = data['access_token'] as String;
    await setzeToken(token);
    return token;
  }

  Future<dynamic> request(
    String path, {
    String method = 'GET',
    Object? body,
  }) async {
    final uri = Uri.parse('$baseUrl$path');
    final headers = {
      'Content-Type': 'application/json',
      if (_token != null) 'Authorization': 'Bearer $_token',
    };
    final encodedBody = body != null ? jsonEncode(body) : null;

    late http.Response response;
    switch (method) {
      case 'POST':
        response = await _http.post(uri, headers: headers, body: encodedBody);
        break;
      case 'PUT':
        response = await _http.put(uri, headers: headers, body: encodedBody);
        break;
      case 'PATCH':
        response = await _http.patch(uri, headers: headers, body: encodedBody);
        break;
      case 'DELETE':
        response = await _http.delete(uri, headers: headers);
        break;
      default:
        response = await _http.get(uri, headers: headers);
    }

    if (response.statusCode >= 400) {
      throw ApiException(response.statusCode, _tryDecode(response.body));
    }
    if (response.body.isEmpty) return null;
    return jsonDecode(response.body);
  }

  dynamic _tryDecode(String body) {
    try {
      return jsonDecode(body);
    } catch (_) {
      return null;
    }
  }
}