/*
 * Copyright 2004 - 2008 Christian Sprajc. All rights reserved.
 *
 * This file is part of PowerFolder.
 *
 * PowerFolder is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation.
 *
 * PowerFolder is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with PowerFolder. If not, see <http://www.gnu.org/licenses/>.
 *
 * $Id$
 */
package de.dal33t.powerfolder.ui.util;

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.
 * 
 * @deprecated Please use {@link javax.swing.SwingWorker}
 */
@Deprecated
public abstract class SwingWorker {
    private Object value; // see getValue(), setValue()
    private Throwable throwable;

    /**
     * Class to maintain reference to current worker thread under separate
     * synchronization control.
     */
    private static class ThreadVar {
        private Thread thread;

        ThreadVar(Thread t) {
            thread = t;
        }

        synchronized Thread get() {
            return thread;
        }

        synchronized void clear() {
            thread = null;
        }
    }

    private ThreadVar threadVar;

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

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

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

    /**
     * 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;
            }
        }
    }

    /**
     * Return the Throwable that occurred by the <code>construct</code> method.
     * Returns null if either the constructing thread, the current thread was
     * interrupted before a value was produced or now exception occurred.
     * 
     * @return the value created by the <code>construct</code> method
     */
    public Throwable getThrowable() {
        get();
        return throwable;
    }

    /**
     * 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 {
                    beforeConstruct();
                    setValue(construct());
                } catch (Throwable t) {
                    throwable = t;
                } finally {
                    afterConstruct();
                    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();
        }
    }

    // For callbacks **********************************************************

    protected void beforeConstruct() {
        // Left empty = default impl, do nothing
    }

    protected void afterConstruct() {
        // Left empty = default impl, do nothing
    }
}