package org.opencraft.server.task;

/*
 * OpenCraft License
 * 
 * Copyright (c) 2009 Graham Edgecombe, Sren Enevoldsen and Brett Russell.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *     * Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *       
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *       
 *     * Neither the name of the OpenCraft nor the names of its
 *       contributors may be used to endorse or promote products derived from
 *       this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Manages the task queue.
 * @author Graham Edgecombe
 */
public final class TaskQueue {
	
	/**
	 * The task queue singleton.
	 */
	private static final TaskQueue INSTANCE = new TaskQueue();
	
	/**
	 * Logger instance.
	 */
	private static final Logger logger = Logger.getLogger(TaskQueue.class.getName());
	
	/**
	 * Gets the task queue instance.
	 * @return The task queue instance.
	 */
	public static TaskQueue getTaskQueue() {
		return INSTANCE;
	}
	
	/**
	 * The scheduled executor service backing this task queue.
	 */
	private ScheduledExecutorService service = Executors.newScheduledThreadPool(1);
	
	/**
	 * Default private constructor.
	 */
	private TaskQueue() {
		/* empty */
	}
	
	/**
	 * Pushes a task onto the task queue.
	 * @param task The task to be executed.
	 */
	public void push(final Task task) {
		service.submit(new Runnable() {
			public void run() {
				try {
					task.execute();
				} catch (Throwable t) {
					logger.log(Level.SEVERE, "Error during task execution.", t);
				}
			}
		});
	}
	
	/**
	 * Schedules a task to run in the future.
	 * @param task The scheduled task.
	 */
	public void schedule(final ScheduledTask task) {
		schedule(task, task.getDelay());
	}
	
	/**
	 * Internally schedules the task.
	 * @param task The task.
	 * @param delay The remaining delay.
	 */
	private void schedule(final ScheduledTask task, final long delay) {
		service.schedule(new Runnable() {
			public void run() {
				long start = System.currentTimeMillis();
				try {
					task.execute();
				} catch (Throwable t) {
					logger.log(Level.SEVERE, "Error during task execution.", t);
				}
				if (!task.isRunning()) {
					return;
				}
				long elapsed = System.currentTimeMillis() - start;
				long waitFor = task.getDelay() - elapsed;
				if (waitFor < 0) {
					waitFor = 0;
				}
				schedule(task, waitFor);
			}
		}, delay, TimeUnit.MILLISECONDS);
	}
	
}

@@ -2586,9 +2586,9 @@
 ool(
-1
+3
 );%0D%0A

Add more threads to the pool