//
   //  ========================================================================
   //  Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
   //  ------------------------------------------------------------------------
   //  All rights reserved. This program and the accompanying materials
   //  are made available under the terms of the Eclipse Public License v1.0
   //  and Apache License v2.0 which accompanies this distribution.
   //
   //      The Eclipse Public License is available at
  //      http://www.eclipse.org/legal/epl-v10.html
  //
  //      The Apache License v2.0 is available at
  //      http://www.opensource.org/licenses/apache2.0.php
  //
  //  You may elect to redistribute this code under either of these licenses.
  //  ========================================================================
  //
  
  package org.eclipse.jetty.util.thread;
  
  import java.util.concurrent.ArrayBlockingQueue;
  import java.util.concurrent.BlockingQueue;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.LinkedBlockingQueue;
  import java.util.concurrent.RejectedExecutionException;
  import java.util.concurrent.SynchronousQueue;
  import java.util.concurrent.ThreadPoolExecutor;
  import java.util.concurrent.TimeUnit;
  
  import org.eclipse.jetty.util.component.AbstractLifeCycle;
  import org.eclipse.jetty.util.component.LifeCycle;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  
  /* ------------------------------------------------------------ */
  /**
   * Jetty ThreadPool using java 5 ThreadPoolExecutor
   * This class wraps a {@link ExecutorService} as a {@link ThreadPool} and
   * {@link LifeCycle} interfaces so that it may be used by the Jetty <code>org.eclipse.jetty.server.Server</code>
   */
  public class ExecutorThreadPool extends AbstractLifeCycle implements ThreadPool, LifeCycle
  {
      private static final Logger LOG = Log.getLogger(ExecutorThreadPool.class);
      private final ExecutorService _executor;
  
      /* ------------------------------------------------------------ */
      public ExecutorThreadPool(ExecutorService executor)
      {
          _executor = executor;
      }
  
      /* ------------------------------------------------------------ */
      /**
       * Wraps an {@link ThreadPoolExecutor}.
       * Max pool size is 256, pool thread timeout after 60 seconds and
       * an unbounded {@link LinkedBlockingQueue} is used for the job queue;
       */
      public ExecutorThreadPool()
      {
          // Using an unbounded queue makes the maxThreads parameter useless
          // Refer to ThreadPoolExecutor javadocs for details
          this(new ThreadPoolExecutor(256, 256, 60, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>()));
      }
  
      /* ------------------------------------------------------------ */
      /**
       * Wraps an {@link ThreadPoolExecutor}.
       * Max pool size is 256, pool thread timeout after 60 seconds, and core pool size is 32 when queueSize &gt;= 0.
       * @param queueSize can be -1 for using an unbounded {@link LinkedBlockingQueue}, 0 for using a
       * {@link SynchronousQueue}, greater than 0 for using a {@link ArrayBlockingQueue} of the given size.
       */
      public ExecutorThreadPool(int queueSize)
      {
          this(queueSize < 0 ? new ThreadPoolExecutor(256, 256, 60, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>()) :
                  queueSize == 0 ? new ThreadPoolExecutor(32, 256, 60, TimeUnit.SECONDS, new SynchronousQueue<Runnable>()) :
                          new ThreadPoolExecutor(32, 256, 60, TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(queueSize)));
      }
  
      /* ------------------------------------------------------------ */
      /**
       * Wraps an {@link ThreadPoolExecutor} using
       * an unbounded {@link LinkedBlockingQueue} is used for the jobs queue;
       * @param corePoolSize must be equal to maximumPoolSize
       * @param maximumPoolSize the maximum number of threads to allow in the pool
       * @param keepAliveTime the max time a thread can remain idle, in milliseconds
       */
      public ExecutorThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime)
      {
          this(corePoolSize, maximumPoolSize, keepAliveTime, TimeUnit.MILLISECONDS);
      }
  
      /* ------------------------------------------------------------ */
      /**
       * Wraps an {@link ThreadPoolExecutor} using
       * an unbounded {@link LinkedBlockingQueue} is used for the jobs queue.
       * @param corePoolSize must be equal to maximumPoolSize
       * @param maximumPoolSize the maximum number of threads to allow in the pool
       * @param keepAliveTime the max time a thread can remain idle
       * @param unit the unit for the keepAliveTime
      */
     public ExecutorThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit)
     {
         this(corePoolSize, maximumPoolSize, keepAliveTime, unit, new LinkedBlockingQueue<Runnable>());
     }
 
     /* ------------------------------------------------------------ */
 
     /**
      * Wraps an {@link ThreadPoolExecutor}
      * @param corePoolSize the number of threads to keep in the pool, even if they are idle
      * @param maximumPoolSize the maximum number of threads to allow in the pool
      * @param keepAliveTime the max time a thread can remain idle
      * @param unit the unit for the keepAliveTime
      * @param workQueue the queue to use for holding tasks before they are executed
      */
     public ExecutorThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue)
     {
         this(new ThreadPoolExecutor(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue));
     }
 
 
     /* ------------------------------------------------------------ */
     @Override
     public void execute(Runnable job)
     {
         _executor.execute(job);
     }
 
     /* ------------------------------------------------------------ */
     public boolean dispatch(Runnable job)
     {
         try
         {
             _executor.execute(job);
             return true;
         }
         catch(RejectedExecutionException e)
         {
             LOG.warn(e);
             return false;
         }
     }
 
     /* ------------------------------------------------------------ */
     public int getIdleThreads()
     {
         if (_executor instanceof ThreadPoolExecutor)
         {
             final ThreadPoolExecutor tpe = (ThreadPoolExecutor)_executor;
             return tpe.getPoolSize() - tpe.getActiveCount();
         }
         return -1;
     }
 
     /* ------------------------------------------------------------ */
     public int getThreads()
     {
         if (_executor instanceof ThreadPoolExecutor)
         {
             final ThreadPoolExecutor tpe = (ThreadPoolExecutor)_executor;
             return tpe.getPoolSize();
         }
         return -1;
     }
 
     /* ------------------------------------------------------------ */
     public boolean isLowOnThreads()
     {
         if (_executor instanceof ThreadPoolExecutor)
         {
             final ThreadPoolExecutor tpe = (ThreadPoolExecutor)_executor;
             // getActiveCount() locks the thread pool, so execute it last
             return tpe.getPoolSize() == tpe.getMaximumPoolSize() &&
                     tpe.getQueue().size() >= tpe.getPoolSize() - tpe.getActiveCount();
         }
         return false;
     }
 
     /* ------------------------------------------------------------ */
     public void join() throws InterruptedException
     {
         _executor.awaitTermination(Long.MAX_VALUE, TimeUnit.MILLISECONDS);
     }
 
     /* ------------------------------------------------------------ */
     @Override
     protected void doStop() throws Exception
     {
         super.doStop();
         _executor.shutdownNow();
     }
 }