fetch method

@override Future<ResponseBody> fetch(RequestOptions options, Stream<Uint8List>? requestStream, Future<void>? cancelFuture)

Implement this method to make real HTTP requests.

options are the request options.

requestStream is the request stream. It will not be null only when the request body is not empty. Use requestStream if your code rely on RequestOptions.onSendProgress.

cancelFuture corresponds to CancelToken handling. When the request is canceled, cancelFuture will be resolved. To await if a request has been canceled:

cancelFuture?.then((_) => print('request cancelled!'));

Implementation

@override
Future<ResponseBody> fetch(
  RequestOptions options,
  Stream<Uint8List>? requestStream,
  Future<void>? cancelFuture,
) async {
  // 1. Collect request body bytes (SOAP envelopes are small; streaming
  //    semantics aren't needed here).
  Uint8List? bodyBytes;
  if (requestStream != null) {
    final chunks = <int>[];
    await for (final chunk in requestStream) {
      chunks.addAll(chunk);
    }
    if (chunks.isNotEmpty) bodyBytes = Uint8List.fromList(chunks);
  }

  // 2. Build the JS init object for fetch().
  final init = JSObject();
  init.setProperty('method'.toJS, options.method.toJS);

  final headers = JSObject();
  options.headers.forEach((name, value) {
    if (value == null) return;
    headers.setProperty(name.toJS, value.toString().toJS);
  });
  init.setProperty('headers'.toJS, headers);

  if (bodyBytes != null) {
    init.setProperty('body'.toJS, bodyBytes.toJS);
  }

  // 3. Call globalThis.fetch(url, init).
  final fetchFn = jsGlobal.getProperty<JSFunction?>('fetch'.toJS);
  if (fetchFn == null) {
    throw StateError(
      'NodeFetchAdapter: `globalThis.fetch` is not available. '
      'Node.js >= 18 is required.',
    );
  }

  final responsePromise =
      fetchFn.callAsFunction(jsGlobal, options.uri.toString().toJS, init)
          as JSPromise;

  final response = (await responsePromise.toDart) as JSObject;

  final statusCode = (response.getProperty<JSNumber>(
    'status'.toJS,
  )).toDartInt;
  final statusText = response
      .getProperty<JSString?>('statusText'.toJS)
      ?.toDart;

  // 4. Collect response headers into Dio's Map<String, List<String>>.
  final respHeaders = <String, List<String>>{};
  final headersObj = response.getProperty<JSObject>('headers'.toJS);
  final entriesFn = headersObj.getProperty<JSFunction>('entries'.toJS);
  final iterator = entriesFn.callAsFunction(headersObj) as JSObject;

  while (true) {
    final nextFn = iterator.getProperty<JSFunction>('next'.toJS);
    final step = nextFn.callAsFunction(iterator) as JSObject;
    final done = step.getProperty<JSBoolean>('done'.toJS).toDart;
    if (done) break;

    final value = step.getProperty<JSArray>('value'.toJS);
    final name = (value.getProperty<JSString>(0.toJS)).toDart.toLowerCase();
    final val = (value.getProperty<JSString>(1.toJS)).toDart;
    respHeaders.putIfAbsent(name, () => <String>[]).add(val);
  }

  // 5. Read the body as ArrayBuffer -> Uint8List.
  final arrayBufferFn = response.getProperty<JSFunction>('arrayBuffer'.toJS);
  final bufferPromise = arrayBufferFn.callAsFunction(response) as JSPromise;
  final buffer = (await bufferPromise.toDart) as JSArrayBuffer;
  final bytes = buffer.toDart.asUint8List();

  return ResponseBody.fromBytes(
    bytes,
    statusCode,
    statusMessage: statusText,
    headers: respHeaders,
  );
}