/*
    * 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.handler.codec.http.websocketx.extensions.compression;
  
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.http.websocketx.BinaryWebSocketFrame;
  import io.netty.handler.codec.http.websocketx.ContinuationWebSocketFrame;
  import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
  import io.netty.handler.codec.http.websocketx.WebSocketFrame;
  import io.netty.handler.codec.http.websocketx.extensions.WebSocketExtension;
  import io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionFilter;
  
  import java.util.List;
  
  /**
   * Per-message implementation of deflate decompressor.
   */
  class PerMessageDeflateDecoder extends DeflateDecoder {
  
      private boolean compressing;
  
      /**
       * Constructor
       *
       * @param noContext true to disable context takeover.
       */
      PerMessageDeflateDecoder(boolean noContext) {
          super(noContext, WebSocketExtensionFilter.NEVER_SKIP);
      }
  
      /**
       * Constructor
       *
       * @param noContext true to disable context takeover.
       * @param extensionDecoderFilter extension decoder for per message deflate decoder.
       */
      PerMessageDeflateDecoder(boolean noContext, WebSocketExtensionFilter extensionDecoderFilter) {
          super(noContext, extensionDecoderFilter);
      }
  
      @Override
      public boolean acceptInboundMessage(Object msg) throws Exception {
          if (!super.acceptInboundMessage(msg)) {
              return false;
          }
  
          WebSocketFrame wsFrame = (WebSocketFrame) msg;
          if (extensionDecoderFilter().mustSkip(wsFrame)) {
              if (compressing) {
                  throw new IllegalStateException("Cannot skip per message deflate decoder, compression in progress");
              }
              return false;
          }
  
          return ((wsFrame instanceof TextWebSocketFrame || wsFrame instanceof BinaryWebSocketFrame) &&
                  (wsFrame.rsv() & WebSocketExtension.RSV1) > 0) ||
                 (wsFrame instanceof ContinuationWebSocketFrame && compressing);
      }
  
      @Override
      protected int newRsv(WebSocketFrame msg) {
          return (msg.rsv() & WebSocketExtension.RSV1) > 0?
                  msg.rsv() ^ WebSocketExtension.RSV1 : msg.rsv();
      }
  
      @Override
      protected boolean appendFrameTail(WebSocketFrame msg) {
          return msg.isFinalFragment();
      }
  
      @Override
      protected void decode(ChannelHandlerContext ctx, WebSocketFrame msg,
                            List<Object> out) throws Exception {
          super.decode(ctx, msg, out);
  
          if (msg.isFinalFragment()) {
              compressing = false;
          } else if (msg instanceof TextWebSocketFrame || msg instanceof BinaryWebSocketFrame) {
              compressing = true;
          }
      }
  
  }