/*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project licenses this file to you under the Apache License,
    * version 2.0 (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.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
   * License for the specific language governing permissions and limitations
   * under the License.
   */
  package org.jboss.netty.handler.execution;
  
  import org.jboss.netty.channel.Channel;
  import org.jboss.netty.channel.ChannelEvent;
  import org.jboss.netty.channel.ChannelFuture;
  import org.jboss.netty.channel.ChannelFutureListener;
  import org.jboss.netty.util.ObjectSizeEstimator;
  
  import java.util.concurrent.Executor;
  import java.util.concurrent.Executors;
  import java.util.concurrent.RejectedExecutionException;
  import java.util.concurrent.ThreadFactory;
  import java.util.concurrent.TimeUnit;
  
  /**
   * {@link Executor} which should be used for downstream {@link ChannelEvent}'s. This implementation
   * will take care of preserve the order of the events in a {@link Channel}.  If you don't need to
   * preserve the order just use one of the {@link Executor} implementations provided by the static
   * methods of {@link Executors}.
   * <br>
   * <br>
   * For more informations about how the order is preserved see {@link OrderedMemoryAwareThreadPoolExecutor}
   */
  public final class OrderedDownstreamThreadPoolExecutor extends OrderedMemoryAwareThreadPoolExecutor {
  
      /**
       * Creates a new instance.
       *
       * @param corePoolSize          the maximum number of active threads
       */
      public OrderedDownstreamThreadPoolExecutor(int corePoolSize) {
          super(corePoolSize, 0L, 0L);
      }
  
      /**
       * Creates a new instance.
       *
       * @param corePoolSize          the maximum number of active threads
       * @param keepAliveTime         the amount of time for an inactive thread to shut itself down
       * @param unit                  the {@link TimeUnit} of {@code keepAliveTime}
       */
      public OrderedDownstreamThreadPoolExecutor(
              int corePoolSize, long keepAliveTime, TimeUnit unit) {
          super(corePoolSize, 0L, 0L, keepAliveTime, unit);
      }
  
      /**
       * Creates a new instance.
       *
       * @param corePoolSize          the maximum number of active threads
       * @param keepAliveTime         the amount of time for an inactive thread to shut itself down
       * @param unit                  the {@link TimeUnit} of {@code keepAliveTime}
       * @param threadFactory         the {@link ThreadFactory} of this pool
       */
      public OrderedDownstreamThreadPoolExecutor(
              int corePoolSize, long keepAliveTime, TimeUnit unit, ThreadFactory threadFactory) {
          super(corePoolSize, 0L, 0L,
                  keepAliveTime, unit, threadFactory);
      }
  
      /**
       * Return {@code null}
       */
      @Override
      public ObjectSizeEstimator getObjectSizeEstimator() {
          return null;
      }
  
      /**
       * Throws {@link UnsupportedOperationException} as there is not support for limit the memory
       * size in this implementation
       */
      @Override
      public void setObjectSizeEstimator(ObjectSizeEstimator objectSizeEstimator) {
          throw new UnsupportedOperationException("Not supported by this implementation");
      }
  
      /**
       * Returns {@code 0L}
       */
      @Override
      public long getMaxChannelMemorySize() {
          return 0L;
      }
 
     /**
      * Throws {@link UnsupportedOperationException} as there is not support for limit the memory
      * size in this implementation
      */
     @Override
     public void setMaxChannelMemorySize(long maxChannelMemorySize) {
         throw new UnsupportedOperationException("Not supported by this implementation");
     }
 
     /**
      * Returns {@code 0L}
      */
     @Override
     public long getMaxTotalMemorySize() {
         return 0L;
     }
 
     /**
      * Return {@code false} as we not need to cound the memory in this implementation
      */
     @Override
     protected boolean shouldCount(Runnable task) {
         return false;
     }
 
     @Override
     public void execute(Runnable command) {
 
         // check if the Runnable was of an unsupported type
         if (command instanceof ChannelUpstreamEventRunnable) {
             throw new RejectedExecutionException("command must be enclosed with an downstream event.");
         }
         doExecute(command);
     }
 
     @Override
     protected Executor getChildExecutor(ChannelEvent e) {
         final Object key = getChildExecutorKey(e);
         Executor executor = childExecutors.get(key);
         if (executor == null) {
             executor = new ChildExecutor();
             Executor oldExecutor = childExecutors.putIfAbsent(key, executor);
             if (oldExecutor != null) {
                 executor = oldExecutor;
             } else {
                 // register a listener so that the ChildExecutor will get removed once the channel was closed
                 e.getChannel().getCloseFuture().addListener(new ChannelFutureListener() {
 
                     public void operationComplete(ChannelFuture future) throws Exception {
                         removeChildExecutor(key);
                     }
                 });
             }
         }
 
         return executor;
     }
 }