class ExampleEndpoint extends Endpoint {
  Stream<String> echoStream(Session session, Stream<String> stream) async* {
    await for (var message in stream) {
      yield message;
    }
  }
}

var inStream = StreamController<String>();
var outStream = client.example.echoStream(inStream.stream);

outStream.listen((message) => print('Received: $message'));
inStream.add('Hello');

class PixelDrawingEndpoint extends Endpoint {
  static const _channelPixelAdded = 'pixel-added';
  final _pixelData = Uint8List(_numPixels);

  Future<void> setPixel(
    Session session, {
    required int colorIndex,
    required int pixelIndex,
  }) async {
    _pixelData[pixelIndex] = colorIndex;

    // Notify all connected clients that we set a pixel, by posting a message
    // to the _channelPixelAdded channel.
    session.messages.postMessage(
      _channelPixelAdded,
      ImageUpdate(
        pixelIndex: pixelIndex,
        colorIndex: colorIndex,
      ),
    );
  }

  /// Returns a stream of image updates. The first message will always be a
  /// `ImageData` object, which contains the full image. Sequential updates
  /// will be `ImageUpdate` objects, which contains a single updated pixel.
  Stream imageUpdates(Session session) async* {
    var updateStream =
        session.messages.createStream<ImageUpdate>(_channelPixelAdded);

    yield ImageData(
      pixels: _pixelData.buffer.asByteData(),
      width: _imageWidth,
      height: _imageHeight,
    );

    await for (var imageUpdate in updateStream) {
      yield imageUpdate;
    }
  }
}