/*
    * Copyright 2014 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.example.spdy.client;
  
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelOutboundHandlerAdapter;
  import io.netty.channel.ChannelPromise;
  import io.netty.handler.codec.http.HttpMessage;
  import io.netty.handler.codec.spdy.SpdyHttpHeaders;
  import io.netty.handler.codec.spdy.SpdyHttpHeaders.Names;
  
  /**
   * Adds a unique client stream ID to the SPDY header. Client stream IDs MUST be odd.
   */
  public class SpdyClientStreamIdHandler extends ChannelOutboundHandlerAdapter {
  
      private int currentStreamId = 1;
  
      public boolean acceptOutboundMessage(Object msg) {
          return msg instanceof HttpMessage;
      }
  
      @Override
      public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
          if (acceptOutboundMessage(msg)) {
              HttpMessage httpMsg = (HttpMessage) msg;
              if (!httpMsg.headers().contains(SpdyHttpHeaders.Names.STREAM_ID)) {
                  httpMsg.headers().setInt(Names.STREAM_ID, currentStreamId);
                  // Client stream IDs are always odd
                  currentStreamId += 2;
              }
          }
          ctx.write(msg, promise);
      }
  }