package principal;


import javax.swing.SwingUtilities;

/**
 * This is the 3rd version of SwingWorker (also known as
 * SwingWorker 3), an abstract class that you subclass to
 * perform GUI-related work in a dedicated thread.  For
 * instructions on and examples of using this class, see:
 * 
 * http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html
 *
 * Note that the API changed slightly in the 3rd version:
 * You must now invoke start() on the SwingWorker after
 * creating it.
 * 
 * @author	classe récupérée sur le site de Sun Microsystems.
 */
public abstract class SwingWorker
{	/**
     * see getValue(), setValue()
     */
    private Object value;  
    /**
     * -
     */
    private ThreadVar threadVar;

    /** 
     * Class to maintain reference to current worker thread
     * under separate synchronization control.
     */
    private static class ThreadVar 
    {	/**
         * -
         */
        private Thread thread;
        
        /**
         * -
         * @param	t	thread
         */
        ThreadVar(Thread t)
        {	thread = t; 
        }
        /**
         * -
         * @return	-
         */
        synchronized Thread get() 
        {	return thread;
        }
        /**
         * -
         */
        synchronized void clear()
        { 	thread = null;
        }
    }

    /** 
     * Get the value produced by the worker thread, or null if it 
     * hasn't been constructed yet.
     * 
     * @return	object
     */
    protected synchronized Object getValue()
    {	return value; 
    }

    /** 
     * Set the value produced by worker thread 
     * @param	x	x
     */
    private synchronized void setValue(Object x)
    { 
        value = x; 
    }

    /** 
     * Compute the value to be returned by the <code>get</code> method. 
     * 
     * @return	object
     */
    public abstract Object construct();

    /**
     * Called on the event dispatching thread (not on the worker thread)
     * after the <code>construct</code> method has returned.
     */
    public void finished()
    {
    }

    /**
     * A new method that interrupts the worker thread.  Call this method
     * to force the worker to stop what it's doing.
     */
    public void interrupt()
    {
        Thread t = threadVar.get();
        if (t != null) {
            t.interrupt();
        }
        threadVar.clear();
    }

    /**
     * Return the value created by the <code>construct</code> method.  
     * Returns null if either the constructing thread or the current
     * thread was interrupted before a value was produced.
     * 
     * @return the value created by the <code>construct</code> method
     */
    public Object get()
    {
        while (true) {  
            Thread t = threadVar.get();
            if (t == null)
            {
                return getValue();
            }
            try
            {
                t.join();
            }
            catch (InterruptedException e)
            {
                Thread.currentThread().interrupt(); // propagate
                return null;
            }
        }
    }


    /**
     * Start a thread that will call the <code>construct</code> method
     * and then exit.
     */
    public SwingWorker()
    {	/**
    	*
    	*/
        final Runnable doFinished = new Runnable()
        	{
            	public void run() { finished(); }
        	};

        Runnable doConstruct = new Runnable()
	        {	public void run()
	        	{	try
	            	{	setValue(construct());
	                }
	                finally
	                {	threadVar.clear();
	                }
	                SwingUtilities.invokeLater(doFinished);
	            }
	        };

        Thread t = new Thread(doConstruct);
        threadVar = new ThreadVar(t);
    }

    /**
     * Start the worker thread.
     */
    public void start()
    {	Thread t = threadVar.get();
        if (t != null)
        {	t.start();
        }
    }
}