// 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> takeWhile(bool test(T element))
/// Forwards data events while test is successful.
/// The returned stream provides the same events as this stream as long as test
/// returns true for the event data.
/// The stream is done when either this stream is done, or when this stream first
/// provides a value that test doesn't accept.
/// @description Checks that only first elements that passed the test are returned.
/// @author kaigorodov

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

/** index - first position in the stream where test() returns false
 */
void check(List data, bool test(var element), int index) {
  Stream s = IsolateStream.fromIterable(data);
  Stream t = s.takeWhile(test);
  asyncStart();
  int seen = -1;
  t.listen((value) {
    seen++;
    Expect.isTrue(test(value), "test($value)");
    Expect.isTrue(seen < index, "seen=$seen, index=$index");
    Expect.equals(data[seen], value);
  }, onDone: () {
    Expect.equals(index, seen + 1);
    if (index < data.length) {
      Expect.isFalse(test(data[index]));
    }
    asyncEnd();
  });
}

main() {
  check([], (element) => true, 0);
  check([-1, -2, -3, 1, 2, 3 - 1, -2, -3], (element) => element < 0, 3);
  check([1, 2, 3], (element) => true, 3);
  check([1, 2, 3, 1], (element) => element == 1, 1);
  check([1, 2, 3], (element) => false, 0);
}