/*
    * Copyright 2023 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.channel.ChannelHandlerContext;
  import io.netty.util.concurrent.Ticker;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import java.util.concurrent.TimeUnit;
  
  
  final class Http2MaxRstFrameListener extends Http2FrameListenerDecorator {
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(Http2MaxRstFrameListener.class);
      private static final Http2Exception RST_FRAME_RATE_EXCEEDED = Http2Exception.newStatic(Http2Error.ENHANCE_YOUR_CALM,
              "Maximum number of RST frames reached",
              Http2Exception.ShutdownHint.HARD_SHUTDOWN, Http2MaxRstFrameListener.class, "onRstStreamRead(..)");
  
      private final long nanosPerWindow;
      private final int maxRstFramesPerWindow;
      private final Ticker ticker;
      private long lastRstFrameNano;
      private int receivedRstInWindow;
  
      Http2MaxRstFrameListener(Http2FrameListener listener, int maxRstFramesPerWindow, int secondsPerWindow,
                               Ticker ticker) {
          super(listener);
          this.maxRstFramesPerWindow = maxRstFramesPerWindow;
          this.nanosPerWindow = TimeUnit.SECONDS.toNanos(secondsPerWindow);
          this.ticker = ticker;
          this.lastRstFrameNano = ticker.nanoTime() - nanosPerWindow;
      }
  
      @Override
      public void onRstStreamRead(ChannelHandlerContext ctx, int streamId, long errorCode) throws Http2Exception {
          long currentNano = ticker.nanoTime();
          if (currentNano - lastRstFrameNano >= nanosPerWindow) {
              lastRstFrameNano = currentNano;
              receivedRstInWindow = 1;
          } else {
              receivedRstInWindow++;
              if (receivedRstInWindow > maxRstFramesPerWindow) {
                  logger.debug("{} Maximum number {} of RST frames reached within {} seconds, " +
                                  "closing connection with {} error", ctx.channel(), maxRstFramesPerWindow,
                          TimeUnit.NANOSECONDS.toSeconds(nanosPerWindow), RST_FRAME_RATE_EXCEEDED.error(),
                          RST_FRAME_RATE_EXCEEDED);
                  throw RST_FRAME_RATE_EXCEEDED;
              }
          }
          super.onRstStreamRead(ctx, streamId, errorCode);
      }
  }