EmbraceDioInterceptor that also respects sending the http status code for onError

CustomEmbraceDioInterceptor.dart

class CustomEmbraceDioInterceptor extends Interceptor {
  CustomEmbraceDioInterceptor({String Function(RequestOptions)? spanNameBuilder})
      : _spanNameBuilder = spanNameBuilder ?? _defaultName;

  static const String _contentLengthHeader = 'Content-Length';

  final String Function(RequestOptions) _spanNameBuilder;
  final _startTimes = HashMap<RequestOptions, int>();

  static String _defaultName(RequestOptions o) => '${o.method} ${o.uri.path}';

  @override
  void onRequest(
    RequestOptions options,
    RequestInterceptorHandler handler,
  ) async {
    _startTimes[options] = DateTime.now().millisecondsSinceEpoch;
    await _injectTraceparent(options);
    handler.next(options);
  }

  @override
  void onResponse(
    Response<dynamic> response,
    ResponseInterceptorHandler handler,
  ) {
    try {
      final request = response.requestOptions;
      final startTimeMs = _startTimes.remove(request) ?? 0;
      final endTimeMs = DateTime.now().millisecondsSinceEpoch;

      Embrace.instance.recordCompletedSpan(
        _spanNameBuilder(request),
        startTimeMs,
        endTimeMs,
        attributes: {
          'http.request.method': request.method,
          'url.full': request.uri.toString(),
          'http.response.status_code': '${response.statusCode ?? 0}',
          'http.request.body.size': '${_bytesSent(request)}',
          'http.response.body.size': '${_bytesReceived(response)}',
        },
      );
    } catch (e) {
      EmbracePlatform.instance
          .logInternalError('Could not capture network request', e.toString());
    } finally {
      handler.next(response);
    }
  }

  @override
  void onError(DioException err, ErrorInterceptorHandler handler) {
    try {
      final request = err.requestOptions;
      final startTimeMs = _startTimes.remove(request) ?? 0;
      final endTimeMs = DateTime.now().millisecondsSinceEpoch;
      final statusCode = err.response?.statusCode;
      Logger.getLogger().info("onError - Recording Span");

      Embrace.instance.recordCompletedSpan(
        _spanNameBuilder(request),
        startTimeMs,
        endTimeMs,
        errorCode: statusCode != null ? ErrorCode.failure : ErrorCode.unknown,
        attributes: {
          'http.request.method': request.method,
          'url.full': request.uri.toString(),
          if (statusCode != null) ...{
            'http.response.status_code': '$statusCode',
            'http.request.body.size': '${_bytesSent(request)}',
            'http.response.body.size': '${_bytesReceived(err.response)}',
          } else
            'error.message': err.message ?? '',
        },
      );
    } catch (e) {
      EmbracePlatform.instance
          .logInternalError('Could not capture network error', e.toString());
    } finally {
      handler.next(err);
    }
  }

  Future<void> _injectTraceparent(RequestOptions options) async {
    if (options.headers.containsKey('traceparent')) return;
    final traceparent =
        await Embrace.instance.generateW3cTraceparent(null, null);
    if (traceparent != null) {
      options.headers['traceparent'] = traceparent;
    }
  }

  int _bytesSent(RequestOptions request) {
    final data = request.data;
    // TODO: do better calculation
    return data is String ? data.length : 0;
  }

  int _bytesReceived(Response<dynamic>? response) {
    if (response == null) return 0;
    final header = response.headers.value(_contentLengthHeader);
    if (header != null) return int.tryParse(header) ?? 0;
    final type = response.requestOptions.responseType;
    if (response.data != null &&
        (type == ResponseType.plain || type == ResponseType.json)) {
      return response.data.toString().length;
    }
    return 0;
  }
}