/*
    * Copyright 2013 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 io.netty.handler.codec.http.websocketx;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.CompositeByteBuf;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.MessageToMessageDecoder;
  import io.netty.handler.codec.TooLongFrameException;
  
  import java.util.List;
  
  /**
   * Handler that aggregate fragmented WebSocketFrame's.
   *
   * Be aware if PING/PONG/CLOSE frames are send in the middle of a fragmented {@link WebSocketFrame} they will
   * just get forwarded to the next handler in the pipeline.
   */
  public class WebSocketFrameAggregator extends MessageToMessageDecoder<WebSocketFrame> {
      private final int maxFrameSize;
      private WebSocketFrame currentFrame;
      private boolean tooLongFrameFound;
  
      /**
       * Construct a new instance
       *
       * @param maxFrameSize      If the size of the aggregated frame exceeds this value,
       *                          a {@link TooLongFrameException} is thrown.
       */
      public WebSocketFrameAggregator(int maxFrameSize) {
          if (maxFrameSize < 1) {
              throw new IllegalArgumentException("maxFrameSize must be > 0");
          }
          this.maxFrameSize = maxFrameSize;
      }
  
      @Override
      protected void decode(ChannelHandlerContext ctx, WebSocketFrame msg, List<Object> out) throws Exception {
          if (currentFrame == null) {
              tooLongFrameFound = false;
              if (msg.isFinalFragment()) {
                  out.add(msg.retain());
                  return;
              }
              ByteBuf buf = ctx.alloc().compositeBuffer().addComponent(msg.content().retain());
              buf.writerIndex(buf.writerIndex() + msg.content().readableBytes());
  
              if (msg instanceof TextWebSocketFrame) {
                  currentFrame = new TextWebSocketFrame(true, msg.rsv(), buf);
              } else if (msg instanceof BinaryWebSocketFrame) {
                  currentFrame = new BinaryWebSocketFrame(true, msg.rsv(), buf);
              } else {
                  buf.release();
                  throw new IllegalStateException(
                          "WebSocket frame was not of type TextWebSocketFrame or BinaryWebSocketFrame");
              }
              return;
          }
          if (msg instanceof ContinuationWebSocketFrame) {
              if (tooLongFrameFound) {
                  if (msg.isFinalFragment()) {
                      currentFrame = null;
                  }
                  return;
              }
              CompositeByteBuf content = (CompositeByteBuf) currentFrame.content();
              if (content.readableBytes() > maxFrameSize - msg.content().readableBytes()) {
                  // release the current frame
                  currentFrame.release();
                  tooLongFrameFound = true;
                  throw new TooLongFrameException(
                          "WebSocketFrame length exceeded " + content +
                                  " bytes.");
              }
              content.addComponent(msg.content().retain());
              content.writerIndex(content.writerIndex() + msg.content().readableBytes());
  
              if (msg.isFinalFragment()) {
                  WebSocketFrame currentFrame = this.currentFrame;
                  this.currentFrame = null;
                  out.add(currentFrame);
                  return;
              } else {
                  return;
              }
          }
         // It is possible to receive CLOSE/PING/PONG frames during fragmented frames so just pass them to the next
         // handler in the chain
         out.add(msg.retain());
     }
 
     @Override
     public void channelInactive(ChannelHandlerContext ctx) throws Exception {
         super.channelInactive(ctx);
         // release current frame if it is not null as it may be a left-over
         if (currentFrame != null) {
             currentFrame.release();
             currentFrame = null;
         }
     }
 
     @Override
     public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
         super.handlerRemoved(ctx);
         // release current frame if it is not null as it may be a left-over as there is not much more we can do in
         // this case
         if (currentFrame != null) {
             currentFrame.release();
             currentFrame = null;
         }
     }
 }