/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.ui.views.framelist;


import java.net.MalformedURLException;
import java.net.URL;

import org.eclipse.core.runtime.Platform;
import org.eclipse.jface.action.Action;
import org.eclipse.jface.resource.ImageDescriptor;
import org.eclipse.jface.util.IPropertyChangeListener;
import org.eclipse.jface.util.PropertyChangeEvent;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.plugin.AbstractUIPlugin;

/**
 * Abstract superclass for actions dealing with frames or a frame list.
 * This listens for changes to the frame list and updates itself
 * accordingly.
 */
public abstract class FrameAction extends Action {
	private FrameList frameList;

	private IPropertyChangeListener propertyChangeListener = new IPropertyChangeListener() {
		public void propertyChange(PropertyChangeEvent event) {
			FrameAction.this.handlePropertyChange(event);
		}
	};

	/**
	 * Constructs a new action for the specified frame list.
	 * and adds a property change listener on it.
	 * 
	 * @param frameList the frame list
	 */
	protected FrameAction(FrameList frameList) {
		this.frameList = frameList;
		frameList.addPropertyChangeListener(propertyChangeListener);
	}

	/**
	 * Disposes this frame action.
	 * This implementation removes the property change listener from the frame list.
	 */
	public void dispose() {
		frameList.removePropertyChangeListener(propertyChangeListener);
	}

	/**
	 * Returns the frame list.
	 */
	public FrameList getFrameList() {
		return frameList;
	}

	/**
	 * Returns the image descriptor with the given relative path.
	 */
	static ImageDescriptor getImageDescriptor(String relativePath) {
		String iconPath = "icons/full/"; //$NON-NLS-1$
		try {
			AbstractUIPlugin plugin = (AbstractUIPlugin) Platform.getPlugin(PlatformUI.PLUGIN_ID);
			URL installURL = plugin.getDescriptor().getInstallURL();
			URL url = new URL(installURL, iconPath + relativePath);
			return ImageDescriptor.createFromURL(url);
		} catch (MalformedURLException e) {
			// should not happen
			return ImageDescriptor.getMissingImageDescriptor();
		}
	}

	/**
	 * Handles a property change event from the frame list.
	 * This implementation calls <code>update()</code>.
	 */
	protected void handlePropertyChange(PropertyChangeEvent event) {
		update();
	}

	/**
	 * Updates this action.  This implementation does nothing.
	 * Most implementations will override this method.
	 */
	public void update() {
	}

}