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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
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 * and Distribution License("CDDL") (collectively, the "License").  You
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 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
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 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
 * Sun designates this particular file as subject to the "Classpath" exception
 * as provided by Sun in the GPL Version 2 section of the License file that
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package com.google.code.hs4j.network.core.impl;

import java.util.concurrent.CancellationException;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.locks.ReentrantLock;


/**
 * Simple {@link Future} implementation, which uses {@link ReentrantLock} to
 * synchronize during the lifecycle.
 * 
 * @see Future
 * @see ReentrantLock
 * 
 * @author Alexey Stashok
 */
public class FutureLockImpl<R> implements Future<R> {

    private final ReentrantLock lock;

    private boolean isDone;

    private CountDownLatch latch;

    private boolean isCancelled;
    private Throwable failure;

    protected R result;


    public FutureLockImpl() {
        this(new ReentrantLock());
    }


    public FutureLockImpl(ReentrantLock lock) {
        this.lock = lock;
        latch = new CountDownLatch(1);
    }


    /**
     * Get current result value without any blocking.
     * 
     * @return current result value without any blocking.
     */
    public R getResult() {
        try {
            lock.lock();
            return result;
        }
        finally {
            lock.unlock();
        }
    }


    /**
     * Set the result value and notify about operation completion.
     * 
     * @param result
     *            the result value
     */
    public void setResult(R result) {
        try {
            lock.lock();
            this.result = result;
            notifyHaveResult();
        }
        finally {
            lock.unlock();
        }
    }


    /**
     * {@inheritDoc}
     */
    public boolean cancel(boolean mayInterruptIfRunning) {
        try {
            lock.lock();
            isCancelled = true;
            notifyHaveResult();
            return true;
        }
        finally {
            lock.unlock();
        }
    }


    /**
     * {@inheritDoc}
     */
    public boolean isCancelled() {
        try {
            lock.lock();
            return isCancelled;
        }
        finally {
            lock.unlock();
        }
    }


    /**
     * {@inheritDoc}
     */
    public boolean isDone() {
        try {
            lock.lock();
            return isDone;
        }
        finally {
            lock.unlock();
        }
    }


    /**
     * {@inheritDoc}
     */
    public R get() throws InterruptedException, ExecutionException {
        latch.await();

        try {
            lock.lock();
            if (isCancelled) {
                throw new CancellationException();
            }
            else if (failure != null) {
                throw new ExecutionException(failure);
            }

            return result;
        }
        finally {
            lock.unlock();
        }
    }


    /**
     * {@inheritDoc}
     */
    public R get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
        boolean isTimeOut = !latch.await(timeout, unit);
        try {
            lock.lock();
            if (!isTimeOut) {
                if (isCancelled) {
                    throw new CancellationException();
                }
                else if (failure != null) {
                    throw new ExecutionException(failure);
                }

                return result;
            }
            else {
                throw new TimeoutException();
            }
        }
        finally {
            lock.unlock();
        }
    }


    /**
     * Notify about the failure, occured during asynchronous operation
     * execution.
     * 
     * @param failure
     */
    public void failure(Throwable failure) {
        try {
            lock.lock();
            this.failure = failure;
            notifyHaveResult();
        }
        finally {
            lock.unlock();
        }
    }


    /**
     * Notify blocked listeners threads about operation completion.
     */
    protected void notifyHaveResult() {
        isDone = true;
        latch.countDown();
    }
}