// 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<RawSocketEvent> distinct([bool equals(T previous, T next)])
/// Skips data events if they are equal to the previous data event.
///
/// The returned stream provides the same events as this stream, except that it
/// never provides two consecutive data events that are equal. That is, errors
/// are passed through to the returned stream, and data events are passed through
/// if they are distinct from the most recently emitted data event.
///
/// Equality is determined by the provided equals method. If that is omitted,
/// the '==' operator on the last provided data element is used.
///
/// If equals throws, the data event is replaced by an error event containing the
/// thrown error. The behavior is equivalent to the original stream emitting the
/// error event, and it doesn't change the what the most recently emitted data
/// event is.
///
/// @description Checks that the returned stream contains only the last event
/// when equals is '(previous, next) => false' and this stream was canceled
/// before method distinct usage.
/// @author ngl@unipro.ru

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

var localhost = InternetAddress.loopbackIPv4;

Future<List> checkDistant() 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], [4, 5], [5]];
  List<RawSocketEvent> received = [];
      Completer<List<RawSocketEvent>> completer =
  new Completer<List<RawSocketEvent>>();
  Future<List<RawSocketEvent>> f = completer.future;

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

  Stream s = receiver.distinct((previous, next) => previous == next);

  s.listen((event) {
    received.add(event);
    receiver.receive();
    if (event == RawSocketEvent.closed) {
      if (!completer.isCompleted) {
        completer.complete(received);
      }
    }
  });

  return f;
}

main() async {
  int attempts = 5;
  int expectedLen = 1;

  for (int i = 0; i < attempts; i++) {
    List list = await checkDistant();
    int listLen = list.length;
    if (listLen == 0) {
      continue;
    }
    if (listLen == 1) {
      break;
    }
    if (listLen > expectedLen) {
      Expect.fail("$listLen elements found instead of $expectedLen.");
    }
    if (i == attempts - 1) {
      print('$listLen elements found. Look like test failed.');
    }
  }
}