/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * ident	"%Z%%M%	%I%	%E% SMI"
 *
 * Copyright (c) 1998-1999 by Sun Microsystems, Inc.
 * All rights reserved.
 */
package com.sun.dhcpmgr.ui;

import javax.swing.SwingUtilities;

/**
 * An abstract class that you subclass to perform
 * GUI-related work in a dedicated thread.
 * For instructions on using this class, see 
 * http://java.sun.com/products/jfc/swingdoc-current/threads2.html
 */
public abstract class SwingWorker {
    private Object value;
    private Thread thread;

    /** 
     * Compute the value to be returned by the <code>get</code> method. 
     */
    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 abort what it's doing.
     */
    public void interrupt() {
        Thread t = thread;
        if (t != null) {
            t.interrupt();
        }
        thread = null;
    }

    /**
     * Return the value created by the <code>construct</code> method.  
     */
    public Object get() {
        while (true) {  // keep trying if we're interrupted
            Thread t;
            synchronized (SwingWorker.this) {
                t = thread;
                if (t == null) {
                    return value;
                }
            }
            try {
                t.join();
            }
            catch (InterruptedException e) {
            }
        }
    }

    /**
     * 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() {
                synchronized (SwingWorker.this) {
                    value = construct();
                    thread = null;
                }
                SwingUtilities.invokeLater(doFinished);
            }
        };

        thread = new Thread(doConstruct);
        thread.start();
    }
}