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   /*
    * 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:
    *
    *   https://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 io.netty.channel;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.ByteBufAllocator;
  import io.netty.util.Attribute;
  import io.netty.util.AttributeKey;
  import io.netty.util.AttributeMap;
  import io.netty.util.concurrent.EventExecutor;
  
  /**
   * Enables a {@link ChannelHandler} to interact with its {@link ChannelPipeline}
   * and other handlers. Among other things a handler can notify the next {@link ChannelHandler} in the
   * {@link ChannelPipeline} as well as modify the {@link ChannelPipeline} it belongs to dynamically.
   *
   * <h3>Notify</h3>
   *
   * You can notify the closest handler in the same {@link ChannelPipeline} by calling one of the various methods
   * provided here.
   *
   * Please refer to {@link ChannelPipeline} to understand how an event flows.
   *
   * <h3>Modifying a pipeline</h3>
   *
   * You can get the {@link ChannelPipeline} your handler belongs to by calling
   * {@link #pipeline()}.  A non-trivial application could insert, remove, or
   * replace handlers in the pipeline dynamically at runtime.
   *
   * <h3>Retrieving for later use</h3>
   *
   * You can keep the {@link ChannelHandlerContext} for later use, such as
   * triggering an event outside the handler methods, even from a different thread.
   * <pre>
   * public class MyHandler extends {@link ChannelDuplexHandler} {
   *
   *     <b>private {@link ChannelHandlerContext} ctx;</b>
   *
   *     public void beforeAdd({@link ChannelHandlerContext} ctx) {
   *         <b>this.ctx = ctx;</b>
   *     }
   *
   *     public void login(String username, password) {
   *         ctx.write(new LoginMessage(username, password));
   *     }
   *     ...
   * }
   * </pre>
   *
   * <h3>Storing stateful information</h3>
   *
   * {@link #attr(AttributeKey)} allow you to
   * store and access stateful information that is related with a {@link ChannelHandler} / {@link Channel} and its
   * context. Please refer to {@link ChannelHandler} to learn various recommended
   * ways to manage stateful information.
   *
   * <h3>A handler can have more than one {@link ChannelHandlerContext}</h3>
   *
   * Please note that a {@link ChannelHandler} instance can be added to more than
   * one {@link ChannelPipeline}.  It means a single {@link ChannelHandler}
   * instance can have more than one {@link ChannelHandlerContext} and therefore
   * the single instance can be invoked with different
   * {@link ChannelHandlerContext}s if it is added to one or more {@link ChannelPipeline}s more than once.
   * Also note that a {@link ChannelHandler} that is supposed to be added to multiple {@link ChannelPipeline}s should
   * be marked as {@link io.netty.channel.ChannelHandler.Sharable}.
   *
   * <h3>Additional resources worth reading</h3>
   * <p>
   * Please refer to the {@link ChannelHandler}, and
   * {@link ChannelPipeline} to find out more about inbound and outbound operations,
   * what fundamental differences they have, how they flow in a  pipeline,  and how to handle
   * the operation in your application.
   */
  public interface ChannelHandlerContext extends AttributeMap, ChannelInboundInvoker, ChannelOutboundInvoker {
  
      /**
       * Return the {@link Channel} which is bound to the {@link ChannelHandlerContext}.
       */
      Channel channel();
  
      /**
       * Returns the {@link EventExecutor} which is used to execute an arbitrary task.
       */
      EventExecutor executor();
  
      /**
      * The unique name of the {@link ChannelHandlerContext}.The name was used when then {@link ChannelHandler}
      * was added to the {@link ChannelPipeline}. This name can also be used to access the registered
      * {@link ChannelHandler} from the {@link ChannelPipeline}.
      */
     String name();
 
     /**
      * The {@link ChannelHandler} that is bound this {@link ChannelHandlerContext}.
      */
     ChannelHandler handler();
 
     /**
      * Return {@code true} if the {@link ChannelHandler} which belongs to this context was removed
      * from the {@link ChannelPipeline}. Note that this method is only meant to be called from with in the
      * {@link EventLoop}.
      */
     boolean isRemoved();
 
     @Override
     ChannelHandlerContext fireChannelRegistered();
 
     @Override
     ChannelHandlerContext fireChannelUnregistered();
 
     @Override
     ChannelHandlerContext fireChannelActive();
 
     @Override
     ChannelHandlerContext fireChannelInactive();
 
     @Override
     ChannelHandlerContext fireExceptionCaught(Throwable cause);
 
     @Override
     ChannelHandlerContext fireUserEventTriggered(Object evt);
 
     @Override
     ChannelHandlerContext fireChannelRead(Object msg);
 
     @Override
     ChannelHandlerContext fireChannelReadComplete();
 
     @Override
     ChannelHandlerContext fireChannelWritabilityChanged();
 
     @Override
     ChannelHandlerContext read();
 
     @Override
     ChannelHandlerContext flush();
 
     /**
      * Return the assigned {@link ChannelPipeline}
      */
     ChannelPipeline pipeline();
 
     /**
      * Return the assigned {@link ByteBufAllocator} which will be used to allocate {@link ByteBuf}s.
      */
     ByteBufAllocator alloc();
 
     /**
      * @deprecated Use {@link Channel#attr(AttributeKey)}
      */
     @Deprecated
     @Override
     <T> Attribute<T> attr(AttributeKey<T> key);
 
     /**
      * @deprecated Use {@link Channel#hasAttr(AttributeKey)}
      */
     @Deprecated
     @Override
     <T> boolean hasAttr(AttributeKey<T> key);
 }