/*
    * 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;
  import org.apache.giraph.comm.requests.WritableRequest;
  import org.apache.giraph.conf.GiraphConfiguration;
  import org.apache.giraph.conf.GiraphConstants;
  import org.apache.giraph.time.SystemTime;
  import org.apache.giraph.time.Time;
  import org.apache.giraph.time.Times;
  import org.apache.log4j.Logger;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelOutboundHandlerAdapter;
  import io.netty.channel.ChannelPromise;
  
  import static org.apache.giraph.utils.ByteUtils.SIZE_OF_BYTE;
  import static org.apache.giraph.utils.ByteUtils.SIZE_OF_INT;
  
  /**
   * Requests have a request type and an encoded request.
   */
  public class RequestEncoder extends ChannelOutboundHandlerAdapter {
    /** Class logger */
    private static final Logger LOG = Logger.getLogger(RequestEncoder.class);
    /** Time class to use */
    private static final Time TIME = SystemTime.get();
    /** Buffer starting size */
    private final int bufferStartingSize;
    /** Start nanoseconds for the encoding time */
    private long startEncodingNanoseconds = -1;
  
    /**
     * Constructor.
     *
     * @param conf Giraph configuration
     */
    public RequestEncoder(GiraphConfiguration conf) {
      bufferStartingSize =
          GiraphConstants.NETTY_REQUEST_ENCODER_BUFFER_SIZE.get(conf);
    }
  
    @Override
    public void write(ChannelHandlerContext ctx, Object msg,
      ChannelPromise promise) throws Exception {
      if (!(msg instanceof WritableRequest)) {
        throw new IllegalArgumentException(
            "encode: Got a message of type " + msg.getClass());
      }
  
      // Encode the request
      if (LOG.isDebugEnabled()) {
        startEncodingNanoseconds = TIME.getNanoseconds();
      }
  
      ByteBuf buf;
      WritableRequest request = (WritableRequest) msg;
      int requestSize = request.getSerializedSize();
      if (requestSize == WritableRequest.UNKNOWN_SIZE) {
        buf = ctx.alloc().buffer(bufferStartingSize);
      } else {
        requestSize +=  SIZE_OF_INT + SIZE_OF_BYTE;
        buf = ctx.alloc().buffer(requestSize);
      }
      ByteBufOutputStream output = new ByteBufOutputStream(buf);
  
      // This will later be filled with the correct size of serialized request
      output.writeInt(0);
      output.writeByte(request.getType().ordinal());
      try {
        request.write(output);
      } catch (IndexOutOfBoundsException e) {
        LOG.error("write: Most likely the size of request was not properly " +
            "specified (this buffer is too small) - see getSerializedSize() " +
            "in " + request.getType().getRequestClass());
        throw new IllegalStateException(e);
      }
      output.flush();
      output.close();
  
      // Set the correct size at the end
     buf.setInt(0, buf.writerIndex() - SIZE_OF_INT);
     if (LOG.isDebugEnabled()) {
       LOG.debug("write: Client " + request.getClientId() + ", " +
           "requestId " + request.getRequestId() +
           ", size = " + buf.readableBytes() + ", " +
           request.getType() + " took " +
           Times.getNanosSince(TIME, startEncodingNanoseconds) + " ns");
     }
     ctx.write(buf, promise);
   }
 }