/*
    * 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.handler;
  
  import io.netty.buffer.ByteBufOutputStream;
  /*if[HADOOP_NON_SECURE]
  else[HADOOP_NON_SECURE]*/
  import org.apache.giraph.comm.requests.RequestType;
  /*end[HADOOP_NON_SECURE]*/
  import org.apache.giraph.comm.requests.WritableRequest;
  import org.apache.log4j.Logger;
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelPromise;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelOutboundHandlerAdapter;
  
  import static org.apache.giraph.utils.ByteUtils.SIZE_OF_INT;
  
  /**
   * How a server should respond to a client. Currently only used for
   * responding to client's SASL messages, and removed after client
   * authenticates.
   */
  public class ResponseEncoder extends ChannelOutboundHandlerAdapter {
    /** Class logger. */
    private static final Logger LOG = Logger.getLogger(ResponseEncoder.class);
  
    @Override
    public void write(ChannelHandlerContext ctx, Object msg,
      ChannelPromise promise) throws Exception {
      if (LOG.isDebugEnabled()) {
        LOG.debug("write(" + ctx + "," + msg);
      }
  
      if (!(msg instanceof WritableRequest)) {
        throw new IllegalArgumentException(
            "encode: cannot encode message of type " + msg.getClass() +
                " since it is not an instance of an implementation of " +
                " WritableRequest.");
      }
      @SuppressWarnings("unchecked")
      WritableRequest writableRequest = (WritableRequest) msg;
  
      ByteBuf buf = ctx.alloc().buffer(10);
      ByteBufOutputStream output = new ByteBufOutputStream(buf);
  
      if (LOG.isDebugEnabled()) {
        LOG.debug("encode: Encoding a message of type " + msg.getClass());
      }
  
      // Space is reserved now to be filled later by the serialize request size
      output.writeInt(0);
      // write type of object.
      output.writeByte(writableRequest.getType().ordinal());
      // write the object itself.
      writableRequest.write(output);
  
      output.flush();
      output.close();
  
      // Set the correct size at the end.
      buf.setInt(0, buf.writerIndex() - SIZE_OF_INT);
  
      if (LOG.isDebugEnabled()) {
        LOG.debug("encode: Encoding a message of type " + msg.getClass());
      }
      ctx.write(buf, promise);
  /*if[HADOOP_NON_SECURE]
  else[HADOOP_NON_SECURE]*/
      if (writableRequest.getType() == RequestType.SASL_COMPLETE_REQUEST) {
        // We are sending to the client a SASL_COMPLETE response (created by
        // the SaslServer handler). The SaslServer handler has removed itself
        // from the pipeline after creating this response, and now it's time for
        // the ResponseEncoder to remove itself also.
        if (LOG.isDebugEnabled()) {
          LOG.debug("encode: Removing RequestEncoder handler: no longer needed," +
              " since client: " + ctx.channel().remoteAddress() + " has " +
              "completed authenticating.");
        }
        ctx.pipeline().remove(this);
      }
  /*end[HADOOP_NON_SECURE]*/
      ctx.write(buf, promise);
   }
 }