/*
 * Moonlight|3D Copyright (C) 2005 The Moonlight|3D team
 * 
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 * 
 * This library 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 Lesser General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 * 
 * Created on Nov 2, 2005
 */
package ml.core.tasks;
/**
 * \package ml.core.tasks
 * 
 * This is the basic framework for background tasks.
 * 
 * This package is part of the core program.
 */

import java.util.ArrayList;
import java.util.List;

import ml.core.helper.Observed;

/**
 * This class acts as a manager for background tasks. Once
 * a task is registered with the manager it is started
 * automatically and is automatically unregistered once
 * it is finished. Observers of this task manager are
 * notified on every change of the list of running
 * background tasks.
 *
 * @author gregor
 */
public class TaskManager extends Observed {
	private ArrayList<Task> tasks;
	
	/**
	 * Helper class to wrap a task in its own thread. 
	 *
	 * @author gregor
	 */
	private class TaskThread extends Thread {
		private final Task task;
		
		public TaskThread(Task task)
		{
			super();
			this.task=task;
		}
		
		@Override
		public void run()
		{
			try {
				task.run();
			} catch(Throwable e) {
				// TODO handle exception here
				e.printStackTrace();
			}
			removeTask(task);
		}
	}
	
	public TaskManager()
	{
		super();
		tasks=new ArrayList<Task>();
	}
	
	/**
	 * Register a new task, start it in a new thread and
	 * notify any observers about that new task.
	 * 
	 * @param task the task to be run
	 */
	public void addTask(Task task)
	{
		synchronized(tasks) {
			tasks.add(task);
			TaskThread thread=new TaskThread(task);
			thread.start();
			notifyObservers();
		}
	}
	
	/**
	 * Return a list of all tasks that are currently running
	 * @return a list of running tasks
	 */
	public List<Task> getTasks() {
		return (ArrayList<Task>) tasks.clone();
	}
	
	/**
	 * Remove a task from the task list and notify any
	 * observers about this change. This does not
	 * stop the background thread.
	 * 
	 * @param task the task to remove from the list
	 */
	private void removeTask(Task task)
	{
		synchronized(tasks) {
			for (int i = 0; i < tasks.size(); i++) {
				if (tasks.get(i) == task) {
					tasks.remove(i);
					break;
				}
			}
			notifyObservers();
		}
	}
}