| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.aries.osgi.functional.test; |
| |
| import org.apache.aries.osgi.functional.Transformer; |
| |
| import java.util.Comparator; |
| import java.util.PriorityQueue; |
| import java.util.concurrent.atomic.AtomicReference; |
| import java.util.function.Function; |
| |
| import static org.apache.aries.osgi.functional.OSGi.NOOP; |
| |
| /** |
| * @author Carlos Sierra Andrés |
| */ |
| public class HighestRankingTransformer<T extends Comparable<? super T>> |
| implements Transformer<T, T> { |
| |
| @Override |
| public Function<T, Runnable> apply(Function<T, Runnable> publisher) { |
| PriorityQueue<T> set = new PriorityQueue<>(Comparator.reverseOrder()); |
| AtomicReference<Runnable> terminator = new AtomicReference<>(NOOP); |
| |
| return t -> { |
| synchronized (set) { |
| set.add(t); |
| |
| if (set.peek() == t) { |
| Runnable old = terminator.get(); |
| |
| old.run(); |
| |
| terminator.set(publisher.apply(t)); |
| } |
| } |
| |
| return () -> { |
| synchronized (set) { |
| T old = set.peek(); |
| |
| set.remove(t); |
| |
| T current = set.peek(); |
| |
| if (current != old) { |
| terminator.getAndSet(NOOP).run(); |
| |
| if (current != null) { |
| terminator.set(publisher.apply(current)); |
| } |
| } |
| } |
| }; |
| }; |
| } |
| } |