/*
    * Copyright 2019 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.http2;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.util.internal.ObjectUtil;
  
  /**
   * Enforce a limit on the maximum number of consecutive empty DATA frames (without end_of_stream flag) that are allowed
   * before the connection will be closed.
   */
  final class Http2EmptyDataFrameListener extends Http2FrameListenerDecorator {
      private final int maxConsecutiveEmptyFrames;
  
      private boolean violationDetected;
      private int emptyDataFrames;
  
      Http2EmptyDataFrameListener(Http2FrameListener listener, int maxConsecutiveEmptyFrames) {
          super(listener);
          this.maxConsecutiveEmptyFrames = ObjectUtil.checkPositive(
                  maxConsecutiveEmptyFrames, "maxConsecutiveEmptyFrames");
      }
  
      @Override
      public int onDataRead(ChannelHandlerContext ctx, int streamId, ByteBuf data, int padding, boolean endOfStream)
              throws Http2Exception {
          if (endOfStream || data.isReadable()) {
              emptyDataFrames = 0;
          } else if (emptyDataFrames++ == maxConsecutiveEmptyFrames && !violationDetected) {
              violationDetected = true;
              throw Http2Exception.connectionError(Http2Error.ENHANCE_YOUR_CALM,
                      "Maximum number %d of empty data frames without end_of_stream flag received",
                      maxConsecutiveEmptyFrames);
          }
  
          return super.onDataRead(ctx, streamId, data, padding, endOfStream);
      }
  
      @Override
      public void onHeadersRead(ChannelHandlerContext ctx, int streamId, Http2Headers headers,
                                int padding, boolean endStream) throws Http2Exception {
          emptyDataFrames = 0;
          super.onHeadersRead(ctx, streamId, headers, padding, endStream);
      }
  
      @Override
      public void onHeadersRead(ChannelHandlerContext ctx, int streamId, Http2Headers headers, int streamDependency,
                                short weight, boolean exclusive, int padding, boolean endStream) throws Http2Exception {
          emptyDataFrames = 0;
          super.onHeadersRead(ctx, streamId, headers, streamDependency, weight, exclusive, padding, endStream);
      }
  }