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package com.openexchange.tools.timeout;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * {@link Timeout} - A simple timeout
 * 
 * @author <a href="mailto:thorben.betten@open-xchange.com">Thorben Betten</a>
 */
public final class Timeout implements Runnable {

    private static final org.apache.commons.logging.Log LOG = org.apache.commons.logging.LogFactory.getLog(Timeout.class);

    private final Lock lock;

    private final Condition condition;

    private final Thread target;

    private long timeoutMillis;

    private final Thread watcher;

    private boolean loop;

    private boolean enabled;

    /**
     * Timeout for current thread
     * 
     * @param timeoutMillis The timeout in milliseconds
     */
    public Timeout(final long timeoutMillis) {
        this(Thread.currentThread(), timeoutMillis);
    }

    /**
     * Timeout for given thread
     * 
     * @param target The target thread to kill if timeout elapsed
     * @param timeoutMillis The timeout in milliseconds
     */
    public Timeout(final Thread target, final long timeoutMillis) {
        super();
        lock = new ReentrantLock();
        condition = lock.newCondition();
        this.target = target;
        this.timeoutMillis = timeoutMillis;
        enabled = true;
        watcher = new Thread(this);
        watcher.start();
    }

    /**
     * Tell the timeout that target has finished
     */
    public void done() {
        lock.lock();
        try {
            loop = false;
            enabled = false;
            condition.signalAll();
        } finally {
            lock.unlock();
        }
    }

    /**
     * Restart the timeout from zero
     */
    public void reset() {
        lock.lock();
        try {
            loop = true;
            condition.signalAll();
        } finally {
            lock.unlock();
        }
    }

    /**
     * Reset
     * 
     * @param millis The new timeout in milliseconds
     */
    public void reset(final long timeoutMillis) {
        lock.lock();
        try {
            this.timeoutMillis = timeoutMillis;
            reset();
        } finally {
            lock.unlock();
        }
    }

    /*
     * (non-Javadoc)
     * @see java.lang.Runnable#run()
     */
    public void run() {
        lock.lock();
        try {
            final Thread current = Thread.currentThread();
            current.setPriority(Thread.MAX_PRIORITY);
            if (enabled) {
                do {
                    loop = false;
                    try {
                        condition.await(timeoutMillis, TimeUnit.MILLISECONDS);
                    } catch (final InterruptedException e) {
                        LOG.error(e.getMessage(), e);
                    }
                } while (enabled && loop);
            }
            if (enabled && target.isAlive()) {
                if (LOG.isInfoEnabled()) {
                    LOG.info(new StringBuilder("Timeout.run(): Stopping thread ").append(target.getName()).toString());
                }
                target.interrupt();
            }
        } finally {
            lock.unlock();
        }
    }
}
