pkgs/test/lib/src/runner/browser/post_message_channel.dart

// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'dart:js_interop';

import 'package:stream_channel/stream_channel.dart';

import 'dom.dart' as dom;

/// Constructs a [StreamChannel] wrapping a new [MessageChannel] communicating
/// with the host page.
///
/// Sends a [MessagePort] to the host page for the channel.
StreamChannel<Object?> postMessageChannel() {
  dom.window.console.log('Suite starting, sending channel to host'.toJS);
  var controller = StreamChannelController<Object?>(sync: true);
  var channel = dom.createMessageChannel();
  dom.window.parent.postMessage('port', dom.window.location.origin, [
    channel.port2,
  ]);
  var portSubscription = dom.Subscription(channel.port1, 'message', (
    dom.Event event,
  ) {
    controller.local.sink.add((event as dom.MessageEvent).data);
  });
  channel.port1.start();

  controller.local.stream.listen(
    channel.port1.postMessage,
    onDone: portSubscription.cancel,
  );

  return controller.foreign;
}