//
   //  ========================================================================
   //  Copyright (c) 1995-2014 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.ScheduledFuture;
  import java.util.concurrent.ScheduledThreadPoolExecutor;
  import java.util.concurrent.ThreadFactory;
  import java.util.concurrent.TimeUnit;
  
  import org.eclipse.jetty.util.component.AbstractLifeCycle;
  
  /**
   * Implementation of {@link Scheduler} based on JDK's {@link ScheduledThreadPoolExecutor}.
   * <p />
   * While use of {@link ScheduledThreadPoolExecutor} creates futures that will not be used,
   * it has the advantage of allowing to set a property to remove cancelled tasks from its
   * queue even if the task did not fire, which provides a huge benefit in the performance
   * of garbage collection in young generation.
   */
  public class ScheduledExecutorScheduler extends AbstractLifeCycle implements Scheduler
  {
      private final String name;
      private final boolean daemon;
      private volatile ScheduledThreadPoolExecutor scheduler;
  
      public ScheduledExecutorScheduler()
      {
          this(null, false);
      }
  
      public ScheduledExecutorScheduler(String name, boolean daemon)
      {
          this.name = name == null ? "Scheduler-" + hashCode() : name;
          this.daemon = daemon;
      }
  
      @Override
      protected void doStart() throws Exception
      {
          scheduler = new ScheduledThreadPoolExecutor(1, new ThreadFactory()
          {
              @Override
              public Thread newThread(Runnable r)
              {
                  Thread thread = new Thread(r, name);
                  thread.setDaemon(daemon);
                  return thread;
              }
          });
          scheduler.setRemoveOnCancelPolicy(true);
          super.doStart();
      }
  
      @Override
      protected void doStop() throws Exception
      {
          scheduler.shutdownNow();
          super.doStop();
          scheduler = null;
      }
  
      @Override
      public Task schedule(Runnable task, long delay, TimeUnit unit)
      {
          ScheduledFuture<?> result = scheduler.schedule(task, delay, unit);
          return new ScheduledFutureTask(result);
      }
  
      private class ScheduledFutureTask implements Task
      {
          private final ScheduledFuture<?> scheduledFuture;
  
          public ScheduledFutureTask(ScheduledFuture<?> scheduledFuture)
          {
              this.scheduledFuture = scheduledFuture;
          }
  
          @Override
          public boolean cancel()
          {
              return scheduledFuture.cancel(false);
          }
      }
 }