/*

 * Copyright (c) 1999, 2011, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package javax.swing;

import java.beans.PropertyChangeEvent;

import java.beans.PropertyChangeListener;

import java.io.*;

import java.lang.ref.WeakReference;

import java.lang.ref.ReferenceQueue;

/**

 * A package-private PropertyChangeListener which listens for

 * property changes on an Action and updates the properties

 * of an ActionEvent source.

 * <p>

 * Subclasses must override the actionPropertyChanged method,

 * which is invoked from the propertyChange method as long as

 * the target is still valid.

 * </p>

 * <p>

 * WARNING WARNING WARNING WARNING WARNING WARNING:<br>

 * Do NOT create an annonymous inner class that extends this!  If you do

 * a strong reference will be held to the containing class, which in most

 * cases defeats the purpose of this class.

 *

 * @param T the type of JComponent the underlying Action is attached to

 *

 * @author Georges Saab

 * @see AbstractButton

 */

abstract class ActionPropertyChangeListener<T extends JComponent>

        implements PropertyChangeListener, Serializable {

    private static ReferenceQueue<JComponent> queue;

    // WeakReference's aren't serializable.

    private transient OwnedWeakReference<T> target;

    // The Component's that reference an Action do so through a strong

    // reference, so that there is no need to check for serialized.

    private Action action;

    private static ReferenceQueue<JComponent> getQueue() {

        synchronized(ActionPropertyChangeListener.class) {

            if (queue == null) {

                queue = new ReferenceQueue<JComponent>();

            }

        }

        return queue;

    }

    public ActionPropertyChangeListener(T c, Action a) {

        super();

        setTarget(c);

        this.action = a;

    }

    /**

     * PropertyChangeListener method.  If the target has been gc'ed this

     * will remove the <code>PropertyChangeListener</code> from the Action,

     * otherwise this will invoke actionPropertyChanged.

     */

    public final void propertyChange(PropertyChangeEvent e) {

        T target = getTarget();

        if (target == null) {

            getAction().removePropertyChangeListener(this);

        } else {

            actionPropertyChanged(target, getAction(), e);

        }

    }

    /**

     * Invoked when a property changes on the Action and the target

     * still exists.

     */

    protected abstract void actionPropertyChanged(T target, Action action,

                                                  PropertyChangeEvent e);

    private void setTarget(T c) {

        ReferenceQueue<JComponent> queue = getQueue();

        // Check to see whether any old buttons have

        // been enqueued for GC.  If so, look up their

        // PCL instance and remove it from its Action.

        OwnedWeakReference<?> r;

        while ((r = (OwnedWeakReference)queue.poll()) != null) {

            ActionPropertyChangeListener<?> oldPCL = r.getOwner();

            Action oldAction = oldPCL.getAction();

            if (oldAction!=null) {

                oldAction.removePropertyChangeListener(oldPCL);

            }

        }

        this.target = new OwnedWeakReference<T>(c, queue, this);

    }

    public T getTarget() {

        if (target == null) {

            // Will only happen if serialized and real target was null

            return null;

        }

        return this.target.get();

    }

    public Action getAction() {

          return action;

    }

    private void writeObject(ObjectOutputStream s) throws IOException {

        s.defaultWriteObject();

        s.writeObject(getTarget());

    }

    @SuppressWarnings("unchecked")

    private void readObject(ObjectInputStream s)

                     throws IOException, ClassNotFoundException {

        s.defaultReadObject();

        T target = (T)s.readObject();

        if (target != null) {

            setTarget(target);

        }

    }

    private static class OwnedWeakReference<U extends JComponent> extends

                              WeakReference<U> {

        private ActionPropertyChangeListener<?> owner;

        OwnedWeakReference(U target, ReferenceQueue<? super U> queue,

                           ActionPropertyChangeListener<?> owner) {

            super(target, queue);

            this.owner = owner;

        }

        public ActionPropertyChangeListener<?> getOwner() {

            return owner;

        }

    }

}