/**
 * Copyright 2007-2016, Kaazing Corporation. All rights reserved.
 *
 * Licensed 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.mina.core.future;

import java.util.concurrent.atomic.AtomicInteger;

import org.apache.mina.core.IoUtil;

/**
 * An {@link IoFuture} of {@link IoFuture}s.  It is useful when you want to
 * get notified when all {@link IoFuture}s are complete.  It is not recommended
 * to use {@link CompositeIoFuture} if you just want to wait for all futures.
 * In that case, please use {@link IoUtil#await(Iterable)} instead
 * for better performance.
 * 
 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
 *
 * @param <E> the type of the child futures.
 */
public class CompositeIoFuture<E extends IoFuture> extends DefaultIoFuture {
    
    private final NotifyingListener listener = new NotifyingListener();
    private final AtomicInteger unnotified = new AtomicInteger();
    private volatile boolean constructionFinished;
    
    public CompositeIoFuture(Iterable<E> children) {
        super(null);
        
        for (E f: children) {
            f.addListener(listener);
            unnotified.incrementAndGet();
        }
        
        constructionFinished = true;
        if (unnotified.get() == 0) {
            setValue(true);
        }
    }
    
    private class NotifyingListener implements IoFutureListener<IoFuture> {
        public void operationComplete(IoFuture future) {
            if (unnotified.decrementAndGet() == 0 && constructionFinished) {
                setValue(true);
            }
        }
    }
}
