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

typedef TokenProvider = String? Function();
typedef UnauthorizedHandler = Future<void> Function();

class ApiService {
  final String baseUrl;
  TokenProvider? _getToken;
  UnauthorizedHandler? _onUnauthorized;

  ApiService({required this.baseUrl});

  void setTokenProvider(TokenProvider provider) {
    _getToken = provider;
  }

  void setUnauthorizedHandler(UnauthorizedHandler handler) {
    _onUnauthorized = handler;
  }

  Map<String, String> _buildHeaders(Map<String, String>? extra) {
    final token = _getToken?.call();
    final headers = {'accept': 'application/json', ...?extra};
    if (token != null && token.isNotEmpty) {
      headers['Authorization'] = 'Bearer $token';
    }
    return headers;
  }

  Future<dynamic> get(String endpoint, {Map<String, String>? headers}) async {
    final response = await http.get(
      Uri.parse('$baseUrl$endpoint'),
      headers: _buildHeaders(headers),
    );
    return _processResponse(response);
  }

  Future<dynamic> post(
    String endpoint,
    dynamic data, {
    Map<String, String>? headers,
  }) async {
    final hasBody = data != null;
    final response = await http.post(
      Uri.parse('$baseUrl$endpoint'),
      headers: _buildHeaders(hasBody ? _jsonHeaders(headers) : headers),
      body: hasBody ? jsonEncode(data) : null,
    );
    return _processResponse(response);
  }

  Future<dynamic> postForm(String endpoint, Map<String, String> data) async {
    final response = await http.post(
      Uri.parse('$baseUrl$endpoint'),
      headers: _buildHeaders({
        'Content-Type': 'application/x-www-form-urlencoded',
        'accept': 'application/json',
      }),
      body: data, // http package handles form-encoding for Map<String, String>
    );
    return _processResponse(response);
  }

  Future<dynamic> put(
    String endpoint,
    dynamic data, {
    Map<String, String>? headers,
  }) async {
    final hasBody = data != null;
    final response = await http.put(
      Uri.parse('$baseUrl$endpoint'),
      headers: _buildHeaders(hasBody ? _jsonHeaders(headers) : headers),
      body: hasBody ? jsonEncode(data) : null,
    );
    return _processResponse(response);
  }

  Future<dynamic> delete(
    String endpoint, {
    Map<String, String>? headers,
  }) async {
    final response = await http.delete(
      Uri.parse('$baseUrl$endpoint'),
      headers: _buildHeaders(headers),
    );
    return _processResponse(response);
  }

  Map<String, String> _jsonHeaders(Map<String, String>? extra) {
    return {'Content-Type': 'application/json', if (extra != null) ...extra};
  }

  Future<dynamic> _processResponse(http.Response res) async {
    final body = res.body.isNotEmpty ? jsonDecode(res.body) : null;
    if (res.statusCode >= 200 && res.statusCode < 300) {
      return body;
    }

    if (res.statusCode == 401 &&
        body is Map<String, dynamic> &&
        body['detail'] == 'Not authenticated' &&
        _onUnauthorized != null) {
      await _onUnauthorized!();
    }

    throw Exception('API error ${res.statusCode}: $body');
  }
}