/*
    * 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.timeout;
  
  import static org.jboss.netty.channel.Channels.*;
  
  import java.util.concurrent.TimeUnit;
  
  import org.jboss.netty.bootstrap.ServerBootstrap;
  import org.jboss.netty.channel.Channel;
  import org.jboss.netty.channel.ChannelHandler;
  import org.jboss.netty.channel.ChannelHandler.Sharable;
  import org.jboss.netty.channel.ChannelHandlerContext;
  import org.jboss.netty.channel.ChannelPipeline;
  import org.jboss.netty.channel.ChannelPipelineFactory;
  import org.jboss.netty.channel.ChannelStateEvent;
  import org.jboss.netty.channel.Channels;
  import org.jboss.netty.channel.LifeCycleAwareChannelHandler;
  import org.jboss.netty.channel.MessageEvent;
  import org.jboss.netty.channel.SimpleChannelUpstreamHandler;
  import org.jboss.netty.channel.WriteCompletionEvent;
  import org.jboss.netty.util.ExternalResourceReleasable;
  import org.jboss.netty.util.HashedWheelTimer;
  import org.jboss.netty.util.Timeout;
  import org.jboss.netty.util.Timer;
  import org.jboss.netty.util.TimerTask;
  
  /**
   * Triggers an {@link IdleStateEvent} when a {@link Channel} has not performed
   * read, write, or both operation for a while.
   *
   * <h3>Supported idle states</h3>
   * <table border="1">
   * <tr>
   * <th>Property</th><th>Meaning</th>
   * </tr>
   * <tr>
   * <td>{@code readerIdleTime}</td>
   * <td>an {@link IdleStateEvent} whose state is {@link IdleState#READER_IDLE}
   *     will be triggered when no read was performed for the specified period of
   *     time.  Specify {@code 0} to disable.</td>
   * </tr>
   * <tr>
   * <td>{@code writerIdleTime}</td>
   * <td>an {@link IdleStateEvent} whose state is {@link IdleState#WRITER_IDLE}
   *     will be triggered when no write was performed for the specified period of
   *     time.  Specify {@code 0} to disable.</td>
   * </tr>
   * <tr>
   * <td>{@code allIdleTime}</td>
   * <td>an {@link IdleStateEvent} whose state is {@link IdleState#ALL_IDLE}
   *     will be triggered when neither read nor write was performed for the
   *     specified period of time.  Specify {@code 0} to disable.</td>
   * </tr>
   * </table>
   *
   * <pre>
   * // An example that sends a ping message when there is no outbound traffic
   * // for 30 seconds.  The connection is closed when there is no inbound traffic
   * // for 60 seconds.
   *
   * public class MyPipelineFactory implements {@link ChannelPipelineFactory} {
   *
   *     private final {@link Timer} timer;
   *     private final {@link ChannelHandler} idleStateHandler;
   *
   *     public MyPipelineFactory({@link Timer} timer) {
   *         this.timer = timer;
   *         this.idleStateHandler = <b>new {@link IdleStateHandler}(timer, 60, 30, 0), // timer must be shared.</b>
   *     }
   *
   *     public {@link ChannelPipeline} getPipeline() {
   *         return {@link Channels}.pipeline(
   *             idleStateHandler,
   *             new MyHandler());
   *     }
   * }
   *
   * // Handler should handle the {@link IdleStateEvent} triggered by {@link IdleStateHandler}.
   * public class MyHandler extends {@link IdleStateAwareChannelHandler} {
   *
   *     {@code @Override}
   *     public void channelIdle({@link ChannelHandlerContext} ctx, {@link IdleStateEvent} e) {
   *         if (e.getState() == {@link IdleState}.READER_IDLE) {
   *             e.getChannel().close();
   *         } else if (e.getState() == {@link IdleState}.WRITER_IDLE) {
  *             e.getChannel().write(new PingMessage());
  *         }
  *     }
  * }
  *
  * {@link ServerBootstrap} bootstrap = ...;
  * {@link Timer} timer = new {@link HashedWheelTimer}();
  * ...
  * bootstrap.setPipelineFactory(new MyPipelineFactory(timer));
  * ...
  * </pre>
  *
  * The {@link Timer} which was specified when the {@link IdleStateHandler} is
  * created should be stopped manually by calling {@link #releaseExternalResources()}
  * or {@link Timer#stop()} when your application shuts down.
  * @see ReadTimeoutHandler
  * @see WriteTimeoutHandler
  *
  * @apiviz.landmark
  * @apiviz.uses org.jboss.netty.util.HashedWheelTimer
  * @apiviz.has org.jboss.netty.handler.timeout.IdleStateEvent oneway - - triggers
  */
 @Sharable
 public class IdleStateHandler extends SimpleChannelUpstreamHandler
                              implements LifeCycleAwareChannelHandler,
                                         ExternalResourceReleasable {
 
     final Timer timer;
 
     final long readerIdleTimeMillis;
     final long writerIdleTimeMillis;
     final long allIdleTimeMillis;
 
     /**
      * Creates a new instance.
      *
      * @param timer
      *        the {@link Timer} that is used to trigger the scheduled event.
      *        The recommended {@link Timer} implementation is {@link HashedWheelTimer}.
      * @param readerIdleTimeSeconds
      *        an {@link IdleStateEvent} whose state is {@link IdleState#READER_IDLE}
      *        will be triggered when no read was performed for the specified
      *        period of time.  Specify {@code 0} to disable.
      * @param writerIdleTimeSeconds
      *        an {@link IdleStateEvent} whose state is {@link IdleState#WRITER_IDLE}
      *        will be triggered when no write was performed for the specified
      *        period of time.  Specify {@code 0} to disable.
      * @param allIdleTimeSeconds
      *        an {@link IdleStateEvent} whose state is {@link IdleState#ALL_IDLE}
      *        will be triggered when neither read nor write was performed for
      *        the specified period of time.  Specify {@code 0} to disable.
      */
     public IdleStateHandler(
             Timer timer,
             int readerIdleTimeSeconds,
             int writerIdleTimeSeconds,
             int allIdleTimeSeconds) {
 
         this(timer,
              readerIdleTimeSeconds, writerIdleTimeSeconds, allIdleTimeSeconds,
              TimeUnit.SECONDS);
     }
 
     /**
      * Creates a new instance.
      *
      * @param timer
      *        the {@link Timer} that is used to trigger the scheduled event.
      *        The recommended {@link Timer} implementation is {@link HashedWheelTimer}.
      * @param readerIdleTime
      *        an {@link IdleStateEvent} whose state is {@link IdleState#READER_IDLE}
      *        will be triggered when no read was performed for the specified
      *        period of time.  Specify {@code 0} to disable.
      * @param writerIdleTime
      *        an {@link IdleStateEvent} whose state is {@link IdleState#WRITER_IDLE}
      *        will be triggered when no write was performed for the specified
      *        period of time.  Specify {@code 0} to disable.
      * @param allIdleTime
      *        an {@link IdleStateEvent} whose state is {@link IdleState#ALL_IDLE}
      *        will be triggered when neither read nor write was performed for
      *        the specified period of time.  Specify {@code 0} to disable.
      * @param unit
      *        the {@link TimeUnit} of {@code readerIdleTime},
      *        {@code writeIdleTime}, and {@code allIdleTime}
      */
     public IdleStateHandler(
             Timer timer,
             long readerIdleTime, long writerIdleTime, long allIdleTime,
             TimeUnit unit) {
 
         if (timer == null) {
             throw new NullPointerException("timer");
         }
         if (unit == null) {
             throw new NullPointerException("unit");
         }
 
         this.timer = timer;
         if (readerIdleTime <= 0) {
             readerIdleTimeMillis = 0;
         } else {
             readerIdleTimeMillis = Math.max(unit.toMillis(readerIdleTime), 1);
         }
         if (writerIdleTime <= 0) {
             writerIdleTimeMillis = 0;
         } else {
             writerIdleTimeMillis = Math.max(unit.toMillis(writerIdleTime), 1);
         }
         if (allIdleTime <= 0) {
             allIdleTimeMillis = 0;
         } else {
             allIdleTimeMillis = Math.max(unit.toMillis(allIdleTime), 1);
         }
     }
 
     /**
      * Return the readerIdleTime that was given when instance this class in milliseconds.
      *
      */
     public long getReaderIdleTimeInMillis() {
         return readerIdleTimeMillis;
     }
 
     /**
      * Return the writerIdleTime that was given when instance this class in milliseconds.
      *
      */
     public long getWriterIdleTimeInMillis() {
         return writerIdleTimeMillis;
     }
 
     /**
      * Return the allIdleTime that was given when instance this class in milliseconds.
      *
      */
     public long getAllIdleTimeInMillis() {
         return allIdleTimeMillis;
     }
 
     /**
      * Stops the {@link Timer} which was specified in the constructor of this
      * handler.  You should not call this method if the {@link Timer} is in use
      * by other objects.
      */
     public void releaseExternalResources() {
         timer.stop();
     }
 
     public void beforeAdd(ChannelHandlerContext ctx) throws Exception {
         if (ctx.getPipeline().isAttached()) {
             // channelOpen event has been fired already, which means
             // this.channelOpen() will not be invoked.
             // We have to initialize here instead.
             initialize(ctx);
         } else {
             // channelOpen event has not been fired yet.
             // this.channelOpen() will be invoked and initialization will occur there.
         }
     }
 
     public void afterAdd(ChannelHandlerContext ctx) throws Exception {
         // NOOP
     }
 
     public void beforeRemove(ChannelHandlerContext ctx) throws Exception {
         destroy(ctx);
     }
 
     public void afterRemove(ChannelHandlerContext ctx) throws Exception {
         // NOOP
     }
 
     @Override
     public void channelOpen(ChannelHandlerContext ctx, ChannelStateEvent e)
             throws Exception {
         // This method will be invoked only if this handler was added
         // before channelOpen event is fired.  If a user adds this handler
         // after the channelOpen event, initialize() will be called by beforeAdd().
         initialize(ctx);
         ctx.sendUpstream(e);
     }
 
     @Override
     public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e)
             throws Exception {
         destroy(ctx);
         ctx.sendUpstream(e);
     }
 
     @Override
     public void messageReceived(ChannelHandlerContext ctx, MessageEvent e)
             throws Exception {
         State state = (State) ctx.getAttachment();
         state.lastReadTime = System.currentTimeMillis();
         ctx.sendUpstream(e);
     }
 
     @Override
     public void writeComplete(ChannelHandlerContext ctx, WriteCompletionEvent e)
             throws Exception {
         if (e.getWrittenAmount() > 0) {
             State state = (State) ctx.getAttachment();
             state.lastWriteTime = System.currentTimeMillis();
         }
         ctx.sendUpstream(e);
     }
 
     private void initialize(ChannelHandlerContext ctx) {
         State state = state(ctx);
 
         // Avoid the case where destroy() is called before scheduling timeouts.
         // See: https://github.com/netty/netty/issues/143
         synchronized (state) {
             switch (state.state) {
             case 1:
             case 2:
                 return;
             }
             state.state = 1;
         }
 
         state.lastReadTime = state.lastWriteTime = System.currentTimeMillis();
         if (readerIdleTimeMillis > 0) {
             state.readerIdleTimeout = timer.newTimeout(
                     new ReaderIdleTimeoutTask(ctx),
                     readerIdleTimeMillis, TimeUnit.MILLISECONDS);
         }
         if (writerIdleTimeMillis > 0) {
             state.writerIdleTimeout = timer.newTimeout(
                     new WriterIdleTimeoutTask(ctx),
                     writerIdleTimeMillis, TimeUnit.MILLISECONDS);
         }
         if (allIdleTimeMillis > 0) {
             state.allIdleTimeout = timer.newTimeout(
                     new AllIdleTimeoutTask(ctx),
                     allIdleTimeMillis, TimeUnit.MILLISECONDS);
         }
     }
 
     private static void destroy(ChannelHandlerContext ctx) {
         State state = state(ctx);
         synchronized (state) {
             if (state.state != 1) {
                 return;
             }
             state.state = 2;
         }
 
         if (state.readerIdleTimeout != null) {
             state.readerIdleTimeout.cancel();
             state.readerIdleTimeout = null;
         }
         if (state.writerIdleTimeout != null) {
             state.writerIdleTimeout.cancel();
             state.writerIdleTimeout = null;
         }
         if (state.allIdleTimeout != null) {
             state.allIdleTimeout.cancel();
             state.allIdleTimeout = null;
         }
     }
 
     private static State state(ChannelHandlerContext ctx) {
         State state;
         synchronized (ctx) {
             // FIXME: It could have been better if there is setAttachmentIfAbsent().
             state = (State) ctx.getAttachment();
             if (state != null) {
                 return state;
             }
             state = new State();
             ctx.setAttachment(state);
         }
         return state;
     }
 
     private void fireChannelIdle(
             final ChannelHandlerContext ctx, final IdleState state, final long lastActivityTimeMillis) {
        ctx.getPipeline().execute(new Runnable() {
 
             public void run() {
                 try {
                     channelIdle(ctx, state, lastActivityTimeMillis);
                 } catch (Throwable t) {
                     fireExceptionCaught(ctx, t);
                 }
             }
         });
     }
 
     protected void channelIdle(
             ChannelHandlerContext ctx, IdleState state, long lastActivityTimeMillis) throws Exception {
         ctx.sendUpstream(new DefaultIdleStateEvent(ctx.getChannel(), state, lastActivityTimeMillis));
     }
 
     private final class ReaderIdleTimeoutTask implements TimerTask {
 
         private final ChannelHandlerContext ctx;
 
         ReaderIdleTimeoutTask(ChannelHandlerContext ctx) {
             this.ctx = ctx;
         }
 
         public void run(Timeout timeout) throws Exception {
             if (timeout.isCancelled() || !ctx.getChannel().isOpen()) {
                 return;
             }
 
             State state = (State) ctx.getAttachment();
             long currentTime = System.currentTimeMillis();
             long lastReadTime = state.lastReadTime;
             long nextDelay = readerIdleTimeMillis - (currentTime - lastReadTime);
             if (nextDelay <= 0) {
                 // Reader is idle - set a new timeout and notify the callback.
                 state.readerIdleTimeout =
                     timer.newTimeout(this, readerIdleTimeMillis, TimeUnit.MILLISECONDS);
                 fireChannelIdle(ctx, IdleState.READER_IDLE, lastReadTime);
             } else {
                 // Read occurred before the timeout - set a new timeout with shorter delay.
                 state.readerIdleTimeout =
                     timer.newTimeout(this, nextDelay, TimeUnit.MILLISECONDS);
             }
         }
     }
 
     private final class WriterIdleTimeoutTask implements TimerTask {
 
         private final ChannelHandlerContext ctx;
 
         WriterIdleTimeoutTask(ChannelHandlerContext ctx) {
             this.ctx = ctx;
         }
 
         public void run(Timeout timeout) throws Exception {
             if (timeout.isCancelled() || !ctx.getChannel().isOpen()) {
                 return;
             }
 
             State state = (State) ctx.getAttachment();
             long currentTime = System.currentTimeMillis();
             long lastWriteTime = state.lastWriteTime;
             long nextDelay = writerIdleTimeMillis - (currentTime - lastWriteTime);
             if (nextDelay <= 0) {
                 // Writer is idle - set a new timeout and notify the callback.
                 state.writerIdleTimeout =
                     timer.newTimeout(this, writerIdleTimeMillis, TimeUnit.MILLISECONDS);
                 fireChannelIdle(ctx, IdleState.WRITER_IDLE, lastWriteTime);
             } else {
                 // Write occurred before the timeout - set a new timeout with shorter delay.
                 state.writerIdleTimeout =
                     timer.newTimeout(this, nextDelay, TimeUnit.MILLISECONDS);
             }
         }
     }
 
     private final class AllIdleTimeoutTask implements TimerTask {
 
         private final ChannelHandlerContext ctx;
 
         AllIdleTimeoutTask(ChannelHandlerContext ctx) {
             this.ctx = ctx;
         }
 
         public void run(Timeout timeout) throws Exception {
             if (timeout.isCancelled() || !ctx.getChannel().isOpen()) {
                 return;
             }
 
             State state = (State) ctx.getAttachment();
             long currentTime = System.currentTimeMillis();
             long lastIoTime = Math.max(state.lastReadTime, state.lastWriteTime);
             long nextDelay = allIdleTimeMillis - (currentTime - lastIoTime);
             if (nextDelay <= 0) {
                 // Both reader and writer are idle - set a new timeout and
                 // notify the callback.
                 state.allIdleTimeout =
                     timer.newTimeout(this, allIdleTimeMillis, TimeUnit.MILLISECONDS);
                 fireChannelIdle(ctx, IdleState.ALL_IDLE, lastIoTime);
             } else {
                 // Either read or write occurred before the timeout - set a new
                 // timeout with shorter delay.
                 state.allIdleTimeout =
                     timer.newTimeout(this, nextDelay, TimeUnit.MILLISECONDS);
             }
         }
     }
 
     private static final class State {
         // 0 - none, 1 - initialized, 2 - destroyed
         int state;
 
         volatile Timeout readerIdleTimeout;
         volatile long lastReadTime;
 
         volatile Timeout writerIdleTimeout;
         volatile long lastWriteTime;
 
         volatile Timeout allIdleTimeout;
 
         State() {
         }
     }
 }