/*******************************************************************************
 * 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.internal;


import org.eclipse.core.runtime.Platform;
import org.eclipse.jface.util.ListenerList;
import org.eclipse.jface.util.SafeRunnable;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.ui.*;

/**
 * Provides per-part selection tracking for the selection service.
 */
public abstract class AbstractPartSelectionTracker {
	/**
	 * List of selection listeners for this tracker
	 */
	private ListenerList fListeners = new ListenerList(2);
	/**
	 * List of post selection listeners for this tracker
	 */
	private ListenerList postListeners = new ListenerList(2);			
	/**
	 * The id of the part this tracls
	 */
	private String fPartId;
	
	/**
	 * Constructs a part selection tracker for the part with the given id.
	 * 
	 * @param id part identifier
	 */
	public AbstractPartSelectionTracker(String partId) {
		setPartId(partId);
	}
	
	/**
	 * Adds a selection listener to this tracker
	 * 
	 * @param listener the listener to add
	 */
	public void addSelectionListener(ISelectionListener listener) {
		fListeners.add(listener);
	}
	/**
	 * Adds a post selection listener to this tracker
	 * 
	 * @param listener the listener to add
	 */
	public void addPostSelectionListener(ISelectionListener listener) {
		postListeners.add(listener);
	}
	/**
	 * Returns the selection from the part being tracked, 
	 * or <code>null</code> if the part is closed or has no selection.
	 */
	public abstract ISelection getSelection();

	/**
	 * Removes a selection listener from this tracker.
	 * 
	 * @param listener the listener to remove
	 */
	public void removeSelectionListener(ISelectionListener listener) {
		fListeners.remove(listener);
	}
	/**
	 * Removes a post selection listener from this tracker.
	 * 
	 * @param listener the listener to remove
	 */
	public void removePostSelectionListener(ISelectionListener listener) {
		postListeners.remove(listener);
	}
	/**
	 * Disposes this selection tracker.  This removes all listeners currently registered.
	 */
	public void dispose() {
		synchronized (fListeners) {
			Object[] listeners = fListeners.getListeners();
			for (int i = 0; i < listeners.length; i++) {
				fListeners.remove(listeners[i]);
				postListeners.remove(listeners[i]);
			}
		}
	}
	
	/**
	 * Fires a selection event to the listeners.
	 * 
	 * @param part the part or <code>null</code> if no active part
	 * @param sel the selection or <code>null</code> if no active selection
	 * @param listeners the list of listeners to notify
	 */
	protected void fireSelection(final IWorkbenchPart part, final ISelection sel) {
		Object [] array = fListeners.getListeners();
		for (int i = 0; i < array.length; i ++) {
			final ISelectionListener l = (ISelectionListener)array[i];
			if ((part != null && sel != null) || l instanceof INullSelectionListener) {
				Platform.run(new SafeRunnable() {
					public void run() {
						l.selectionChanged(part, sel);
					}
					public void handleException(Throwable e) {
						super.handleException(e);
						// If an unexpected exception happens, remove the listener
						// to make sure the workbench keeps running.
						removeSelectionListener(l);
					}
				});
			}
		}
	}
	/**
	 * Fires a post selection event to the listeners.
	 * 
	 * @param part the part or <code>null</code> if no active part
	 * @param sel the selection or <code>null</code> if no active selection
	 * @param listeners the list of listeners to notify
	 */
	protected void firePostSelection(final IWorkbenchPart part, final ISelection sel) {
		Object [] array = postListeners.getListeners();
		for (int i = 0; i < array.length; i ++) {
			final ISelectionListener l = (ISelectionListener)array[i];
			if ((part != null && sel != null) || l instanceof INullSelectionListener) {
				Platform.run(new SafeRunnable() {
					public void run() {
						l.selectionChanged(part, sel);
					}
					public void handleException(Throwable e) {
						super.handleException(e);
						// If an unexpected exception happens, remove the listener
						// to make sure the workbench keeps running.
						removePostSelectionListener(l);
					}
				});
			}
		}
	}		
	/**
	 * Sets the id of the part that this tracks.
	 * 
	 * @param id view identifier
	 */
	private void setPartId(String partId) {
		fPartId = partId;
	}
	
	/**
	 * Returns the id of the part that this tracks.
	 * 
	 * @return part identifier
	 */
	protected String getPartId() {
		return fPartId;
	}	

}