/*
 * The contents of this file are subject to the Mozilla Public License Version 1.1
 * (the "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at <http://www.mozilla.org/MPL/>.
 * 
 * Software distributed under the License is distributed on an "AS IS" basis, WITHOUT
 * WARRANTY OF ANY KIND, either express or implied. See the License for the specific
 * language governing rights and limitations under the License.
 * 
 * The Original Code is the Venice Web Communities System.
 * 
 * The Initial Developer of the Original Code is Eric J. Bowersox <erbo@silcom.com>,
 * for Silverwrist Design Studios.  Portions created by Eric J. Bowersox are
 * Copyright (C) 2001 Eric J. Bowersox/Silverwrist Design Studios.  All Rights Reserved.
 * 
 * Contributor(s): 
 */
package com.silverwrist.util;

import java.util.Vector;

public class ParallelRunQueue implements Runnable
{
  /*--------------------------------------------------------------------------------
   * Attributes
   *--------------------------------------------------------------------------------
   */

  private Thread[] thrds;
  private Vector queue;
  private int priority;

  /*--------------------------------------------------------------------------------
   * Constructor
   *--------------------------------------------------------------------------------
   */

  public ParallelRunQueue(int nthread)
  {
    thrds = new Thread[nthread];
    for (int i=0; i<nthread; i++)
      thrds[i] = null;
    queue = new Vector();
    priority = Thread.currentThread().getPriority();

  } // end constructor

  /*--------------------------------------------------------------------------------
   * Implementations from interface Runnable
   *--------------------------------------------------------------------------------
   */

  public void run()
  {
    while (queue.size()>0)
    { // unqueue a new Runnable
      Runnable r = (Runnable)(queue.remove(0));
      for (int i=0; i<thrds.length; i++)
      { // scan through our threads list...
	if ((thrds[i]==null) || !(thrds[i].isAlive()))
	{ // a worker thread is available - start it running
	  thrds[i] = new Thread(r);
	  thrds[i].setPriority(priority);
	  thrds[i].start();
	  return;

	} // end if

      } // end for

      r.run();  // if all else fails, run it ourselves

    } // end while

  } // end run

  /*--------------------------------------------------------------------------------
   * External operations
   *--------------------------------------------------------------------------------
   */

  public void queue(Runnable r)
  {
    for (int i=0; i<thrds.length; i++)
    { // scan through our threads list...
      if ((thrds[i]==null) || !(thrds[i].isAlive()))
      { // a worker thread is available - start it running
	thrds[i] = new Thread(r);
	thrds[i].setPriority(priority);
	thrds[i].start();
	return;

      } // end if

    } // end for

    queue.add(r);  // if all else fails, queue it up

  } // end queue

} // end class ParallelRunQueue