// Copyright (c) 2018, 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.

// @dart = 2.9

/// @assertion Stream<E> asyncExpand<E>(Stream<E> convert(T event))
/// Transforms each element into a sequence of asynchronous events.
///
/// Returns a new stream and for each event of this stream, do the following:
/// . . .
/// - If the call returns null, no further action is taken for the elements.
///
/// @description Checks that if convert returns null, no value is put on the
/// output stream, just as if it returned an empty stream.
/// @author ngl@unipro.ru

import "dart:async";
import "dart:io";
import "../http_utils.dart";
import "../../../Utils/expect.dart";

var localhost = InternetAddress.loopbackIPv4;

main() async {
  RawDatagramSocket producer = await RawDatagramSocket.bind(localhost, 0);
  RawDatagramSocket receiver = await RawDatagramSocket.bind(localhost, 0);
  List<List<int>> toSend = [[0, 1, 2, 3], [1, 2, 3], [2, 3], [3]];

  bool wasSent =
  await sendDatagram(producer, toSend, localhost, receiver.port);
  Expect.isTrue(wasSent, "No datagram was sent");

  Stream stream = receiver.asyncExpand((e) => null);
  stream.length.then((value) {
    Expect.equals(0, value);
  });
  receiver.close();
}