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/*
 * Copyright (C) 2012 United States Government as represented by the Administrator of the
 * National Aeronautics and Space Administration.
 * All Rights Reserved.
 */

package gov.nasa.worldwind.util;

import gov.nasa.worldwind.WorldWind;

import java.util.concurrent.atomic.*;

/**
 * Periodically checks network availability.
 *
 * @author tag
 * @version $Id: NetworkCheckThread.java 1171 2013-02-11 21:45:02Z dcollins $
 */
public class NetworkCheckThread extends Thread
{
    protected static final long DEFAULT_NET_CHECK_INTERVAL = 1000; // milliseconds

    protected AtomicBoolean showNetStatus;
    protected AtomicBoolean isNetAvailable;
    protected AtomicLong netChecInterval = new AtomicLong(DEFAULT_NET_CHECK_INTERVAL);

    /**
     * Constructs a new instance of this class. Once started, the thread checks network availability at a specified
     * frequency and stores the result in an atomic variable specified to the constructor. The thread terminates when
     * it's interrupted or when a specified boolean atomic variable has the value false.
     *
     * @param showNetStatus  a reference to an atomic variable indicating whether the thread should continue running.
     *                       This variable is tested prior to each network check. The thread terminates when it becomes
     *                       false.
     * @param isNetAvailable a reference to an atomic variable in which to write the status of the network check.
     * @param interval       the interval at which to perform the network check, or null if the default interval of one
     *                       second is to be used.
     */
    public NetworkCheckThread(AtomicBoolean showNetStatus, AtomicBoolean isNetAvailable, Long interval)
    {
        if (showNetStatus == null)
        {
            String msg = Logging.getMessage("nullValue.StatusReferenceIsNull");
            Logging.logger().severe(msg);
            throw new IllegalArgumentException(msg);
        }

        if (isNetAvailable == null)
        {
            String msg = Logging.getMessage("nullValue.ReturnReferenceIsNull");
            Logging.logger().severe(msg);
            throw new IllegalArgumentException(msg);
        }

        this.showNetStatus = showNetStatus;
        this.isNetAvailable = isNetAvailable;

        if (interval != null && interval > 0)
            this.netChecInterval.set(interval);
    }

    @Override
    public void run()
    {
        while (showNetStatus.get() && !Thread.currentThread().isInterrupted())
        {
            //noinspection EmptyCatchBlock
            try
            {
                Thread.sleep(DEFAULT_NET_CHECK_INTERVAL);
                this.isNetAvailable.set(!WorldWind.getNetworkStatus().isNetworkUnavailable());
            }
            catch (InterruptedException e)
            {
                // Intentionally empty
            }
        }
    }
}