//
   //  ========================================================================
   //  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.http.spi;
  
  import java.util.concurrent.Executor;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.ThreadPoolExecutor;
  import java.util.concurrent.TimeUnit;
  
  import org.eclipse.jetty.util.component.ContainerLifeCycle;
  import org.eclipse.jetty.util.component.LifeCycle;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  import org.eclipse.jetty.util.thread.ThreadPool;
  
  public class DelegatingThreadPool extends ContainerLifeCycle implements ThreadPool
  {
      private static final Logger LOG = Log.getLogger(DelegatingThreadPool.class);
      
      private Executor _executor; // memory barrier provided by start/stop semantics
  
      public DelegatingThreadPool(Executor executor)
      {
          _executor=executor;
          addBean(_executor);
      }
  
      /* ------------------------------------------------------------ */
      public Executor getExecutor()
      {
          return _executor;
      }
      
      /* ------------------------------------------------------------ */
      public void setExecutor(Executor executor)
      {
          if (isRunning())
              throw new IllegalStateException(getState());
          updateBean(_executor,executor);
          _executor=executor;
      }
      
      /* ------------------------------------------------------------ */
      @Override
      public void execute(Runnable job)
      {
          _executor.execute(job);
      }
  
      /* ------------------------------------------------------------ */
      @Override
      public int getIdleThreads()
      {
          final Executor executor=_executor;
          if (executor instanceof ThreadPool)
              return ((ThreadPool)executor).getIdleThreads();
          
          if (executor instanceof ThreadPoolExecutor)
          {
              final ThreadPoolExecutor tpe = (ThreadPoolExecutor)executor;
              return tpe.getPoolSize() - tpe.getActiveCount();
          }
          return -1;
      }
  
      /* ------------------------------------------------------------ */
      @Override
      public int getThreads()
      {
          final Executor executor=_executor;
          if (executor instanceof ThreadPool)
              return ((ThreadPool)executor).getThreads();
          
          if (executor instanceof ThreadPoolExecutor)
          {
              final ThreadPoolExecutor tpe = (ThreadPoolExecutor)executor;
              return tpe.getPoolSize();
          }
          return -1;
      }
  
      /* ------------------------------------------------------------ */
      @Override
     public boolean isLowOnThreads()
     {
         final Executor executor=_executor;
         if (executor instanceof ThreadPool)
             return ((ThreadPool)executor).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;
     }
 
     /* ------------------------------------------------------------ */
     @Override
     public void join() throws InterruptedException
     {
         final Executor executor=_executor;
         if (executor instanceof ThreadPool)
             ((ThreadPool)executor).join();
         else if (executor instanceof ExecutorService)
             ((ExecutorService)executor).awaitTermination(Long.MAX_VALUE, TimeUnit.MILLISECONDS);
         else
             throw new IllegalStateException();
     }
 
     /* ------------------------------------------------------------ */
     @Override
     protected void doStop() throws Exception
     {
         super.doStop();
         if (!(_executor instanceof LifeCycle) && (_executor instanceof ExecutorService))
             ((ExecutorService)_executor).shutdownNow();
     }
 
 }