/*******************************************************************************
 * Copyright (c) 2004, 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.ant.internal.ui.editor;

import org.eclipse.ant.internal.ui.editor.utils.ProjectHelper;


public class DecayCodeCompletionDataStructuresThread extends Thread {
	
	private static final int fgDelay= 6000 * 5; //5 minutes 
	
	private static DecayCodeCompletionDataStructuresThread fgInstance;
	
	public static DecayCodeCompletionDataStructuresThread getDefault() {
		if (fgInstance == null) {
			fgInstance= new DecayCodeCompletionDataStructuresThread();
		}
		return fgInstance;
	}
	
	/**
	 * Creates a new background thread. The thread 
	 * runs with minimal priority.
	 */
	private DecayCodeCompletionDataStructuresThread() {
		super("Decay Ant Data Structures"); //$NON-NLS-1$
		setPriority(Thread.MIN_PRIORITY);
		setDaemon(true);
		fgInstance= this;
        setContextClassLoader(null); //don't hold on to any class loaders
	}
	
	/**
	 * The background activity that is triggered when the last <code>AntModel</code> is disposed.
	 * Waits for the required delay and then nulls out the memory expensive Ant code
	 * completion data structures and reset the ProjectHelper.
	 * If an <code>AntModel</code> is created during the wait, the thread is
	 * interrupted and no nulling out occurs.
	 */
	public void run() {
		synchronized (this) {
			try {
				wait(fgDelay);
				AntEditorCompletionProcessor.resetCodeCompletionDataStructures();
                ProjectHelper.reset();
			} catch (InterruptedException x) {
			}
		}
	}
	
	/**
	 * Cancels the background thread.
	 */
	public static void cancel() {
		if (fgInstance != null) {
			synchronized (fgInstance) {
				fgInstance.interrupt();
				fgInstance= null;
			}
		}
	}
}