/*

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF 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.apache.giraph.comm.netty;

 import java.net.InetSocketAddress;

 import java.util.List;

 import com.google.common.collect.Lists;

 import io.netty.channel.Channel;

 import io.netty.channel.ChannelFuture;

 import io.netty.channel.ChannelFutureListener;

 import org.apache.log4j.Logger;

 /**

  * Maintains multiple channels and rotates between them.  This is thread-safe.

  */

 public class ChannelRotater {

   /** Logger */

   private static final Logger LOG = Logger.getLogger(ChannelRotater.class);

   /** Index of last used channel */

   private int index = 0;

   /** Channel list */

   private final List<Channel> channelList = Lists.newArrayList();

   /** Task id of this channel */

   private final Integer taskId;

   /** Address these channels are associated with */

   private final InetSocketAddress address;

   /**

    * Constructor

    *

    * @param taskId Id of the task these channels as associated with

    * @param address Address these channels are associated with

    */

   public ChannelRotater(Integer taskId, InetSocketAddress address) {

     this.taskId = taskId;

     this.address = address;

   }

   public Integer getTaskId() {

     return taskId;

   }

   /**

    * Add a channel to the rotation

    *

    * @param channel Channel to add

    */

   public synchronized void addChannel(Channel channel) {

     synchronized (channelList) {

       channelList.add(channel);

     }

   }

   /**

    * Get the next channel

    *

    * @return Next channel

    */

   public synchronized Channel nextChannel() {

     if (channelList.isEmpty()) {

       LOG.warn("nextChannel: No channels exist for hostname " +

         address.getHostName());

       return null;

     }

     ++index;

     if (index >= channelList.size()) {

       index = 0;

     }

     return channelList.get(index);

   }

   /**

    * Remove the a channel

    *

    * @param channel Channel to remove

    * @return Return true if successful, false otherwise

    */

   public synchronized boolean removeChannel(Channel channel) {

     boolean success = channelList.remove(channel);

     if (index >= channelList.size()) {

       index = 0;

     }

     return success;

   }

   /**

    * Get the number of channels in this object

    *

    * @return Number of channels

    */

   public synchronized int size() {

     return channelList.size();

   }

   /**

    * Close the channels

    *

    * @param channelFutureListener If desired, pass in a channel future listener

    */

   public synchronized void closeChannels(

       ChannelFutureListener channelFutureListener) {

     for (Channel channel : channelList) {

       ChannelFuture channelFuture = channel.close();

       if (channelFutureListener != null) {

         channelFuture.addListener(channelFutureListener);

       }

     }

   }

   /**

    * Get a copy of the channels

    *

    * @return Copy of the channels

    */

   public synchronized Iterable<Channel> getChannels() {

     return Lists.newArrayList(channelList);

   }

 }