LibTest/async/Stream/distinct_A03_t01.test.dart

// Copyright (c) 2011, 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.

/// @assertion Stream<T> distinct([bool equals(T previous, T next)])
///    If a broadcast stream is listened to more than once, each subscription
/// will individually perform the equals test.
/// @description Checks that [equals] is called for each subscription.
/// @issue #29638
/// @author a.semenov@unipro.ru

library distinct_A03_t01;

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

class Key<T> {
  T previous;
  T next;

  Key(this.previous, this.next);

  bool operator ==(other) =>
      (other is Key) &&
      other.previous == this.previous &&
      other.next == this.next;

  int get hashCode {
    return previous.hashCode ^ next.hashCode;
  }

  String toString() {
    return "[$previous,$next]";
  }
}

Future<List<T>> subscribe<T>(Stream<T> stream) {
  Completer<List<T>> completer = new Completer<List<T>>();
  List<T> received = [];
  stream.listen((T event) {
    received.add(event);
  }, onDone: () {
    completer.complete(received);
  });
  return completer.future;
}

void check<T>(Stream<T> s) {
  Map<Key<T>, int> equalsLog = new Map<Key<T>, int>();

  bool equals(T p, T n) {
    Key<T> key = new Key<T>(p, n);
    equalsLog[key] = 1 + equalsLog.putIfAbsent(key, () => 0);
    return p == n;
  }

  asyncStart();
  Stream<T> d = s.asBroadcastStream().distinct(equals);
  Future.wait([subscribe(d), subscribe(d), subscribe(d)])
      .then((List<List<T>> result) {
    result.forEach((received) => Expect.listEquals(result[0], received));
    equalsLog.values.forEach((v) => Expect.equals(3, v));
    asyncEnd();
  });
}

void test(CreateStreamFunction create) {
  check(create([]));
  check(create([1, 2, 4, 3]));
  check(create([1, 2, 2, 3]));
  check(create(["a", "b", null, null]));
}