caeate interceptor in flutter

injector.dart

class Injector {
  static final Injector _singleton = new Injector._internal();
  static final dio = Dio();
  factory Injector() {
    return _singleton;
  }
  Injector._internal();
  RestApiClient getClient() {
    // dio.options.connectTimeout = 10000;
    // dio.options.receiveTimeout = 3000;
    dio.options.baseUrl = ApiService.baseurl;
    dio.options.followRedirects = false;
    dio.options.headers["Content-Type"] = "application/json";
    String token =  UserPrefs().getLoggedIUserToken();
    if (token != "") {
      HopLogs.printInfo(filename: "injector:: 1 ", info: "token=" + token);
      dio.options.headers["Authorization"] = token;
      dio.options.headers["Content-Type"] = "application/json";
    }
    dio.interceptors.clear();
    final client = RestApiClient(dio);
    dio.interceptors.add(new LoggingInterceptors(client: client));
    return client;
  }
}

class LoggingInterceptors extends Interceptor {
final RestApiClient client;
  LoggingInterceptors({required this.client});
  @override
  void onRequest(RequestOptions options, RequestInterceptorHandler handler) async{
    HopLogs.printInfo(filename: "injector:: 2", info :'REQUEST[${options.method}] => PATH: ${options.baseUrl}${options.path}');
    options.headers.forEach((k, v) =>  HopLogs.printInfo(filename: "injector:: ", info :'$k: $v'));
    HopLogs.printInfo(filename: "injector:: 3", info : "queryParameters:");
    options.queryParameters.forEach((k, v) =>  HopLogs.printInfo(filename: "injector:: ", info :'$k: $v',));
    if (options.data != null) {
      HopLogs.printInfo(filename: "injector:: 4", info:"Body: ${options.data}");
    }
    HopLogs.printInfo(filename: "injector:: 5", info:
        "--> END ${options.method != null? options.method.toUpperCase() : 'METHOD'}",);
     super.onRequest(options, handler);
  }
  @override
  void onError(DioException err, ErrorInterceptorHandler handler) {
    HopLogs.printError(filename: "injector:: 6", error:
        'ERROR[${err.response?.statusCode}] => PATH: ${err.requestOptions.path}');
    // Reset the request status after completion
     super.onError(err, handler);
  }
@override
void onResponse(Response response, ResponseInterceptorHandler handler) async{
  HopLogs.printInfo(filename: "injector:: 7", info: 'RESPONSE[${response.statusCode}] => PATH: ${response.requestOptions.path}');
  HopLogs.printInfo(filename: "injector:: 8", info: "Headers:");
  response.headers.forEach((k, v) => HopLogs.printInfo(filename: "injector:: ", info: '$k: $v'));
  try {
    var data = response.data;
    HopLogs.printInfo(filename: "injector:: 9", info: "Response: ${jsonEncode(data)}");
    if (data is Map && data.containsKey("code") && data["code"] == 401 &&(response.requestOptions.path != ApiService.refreshConst)) {
      await _handle401Error(response, handler);
    }
    super.onResponse(response, handler);
  } catch (e) {
    HopLogs.printError(filename:'injector:: 10',error: e);
    // Handle response parsing errors
  }
}

Future<void> _handle401Error(Response response, ResponseInterceptorHandler handler) async {
    try {
      HopLogs.printInfo(filename: "injector:: 11", info: "Handling 401 Unauthorized error - Retry");
      // Call the function to refresh the token
      RefreshResponseModel value = await client.doRefreshonSessionExpire();
      if (value.code == 200 && value.data != null) {
        await UserPrefs().setString(AppUserPrefKeys.token, "Bearer ${value.data ?? ""}");
        await _retryFunction(response, handler);
      }
    } catch (error) {
      // Handle the retry error, if needed
      HopLogs.printError(filename: "injector:: 12", error: "Error during retry: $error");
      onResponse(response, handler);
    }
}

Future<void> _retryFunction(Response response,ResponseInterceptorHandler handler ) async {
  try {
    HopLogs.printInfo(filename: "injector:: 13", info: "Retrying the function...");
    // Create a new Options object with updated headers or other parameters
    Options newOptions = Options(
      method: response.requestOptions.method,
      headers: {'Authorization':  UserPrefs().getLoggedIUserToken()},
    );
    // Make the retry request
    Response retryResponse = await Injector.dio.request(
      response.requestOptions.path,
      options: newOptions,
      data: response.requestOptions.data,
      queryParameters: response.requestOptions.queryParameters,
      cancelToken: response.requestOptions.cancelToken,
      onSendProgress: response.requestOptions.onSendProgress,
      onReceiveProgress: response.requestOptions.onReceiveProgress
    );
    // Handle the retry response as needed
    onResponse(retryResponse, handler); // Pass a dummy handler since it's not used in onResponse
  } catch (error) {
    // Handle the retry error, if needed
    HopLogs.printError(filename: "injector:: 14", error: "Error during retry: $error");
    onResponse(response, handler);
  }
}
}