content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF 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 com.datastax.oss.driver.internal.core.protocol;
  
  import com.datastax.oss.driver.shaded.guava.common.collect.ImmutableList;
  import com.datastax.oss.protocol.internal.Frame;
  import com.datastax.oss.protocol.internal.FrameCodec;
  import com.datastax.oss.protocol.internal.PrimitiveCodec;
  import com.datastax.oss.protocol.internal.Segment;
  import com.datastax.oss.protocol.internal.SegmentBuilder;
  import edu.umd.cs.findbugs.annotations.NonNull;
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelPromise;
  import io.netty.util.concurrent.Future;
  import io.netty.util.concurrent.GenericFutureListener;
  import java.util.ArrayList;
  import java.util.List;
  import net.jcip.annotations.NotThreadSafe;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  @NotThreadSafe
  public class ByteBufSegmentBuilder extends SegmentBuilder<ByteBuf, ChannelPromise> {
  
    private static final Logger LOG = LoggerFactory.getLogger(ByteBufSegmentBuilder.class);
  
    private final ChannelHandlerContext context;
    private final String logPrefix;
  
    public ByteBufSegmentBuilder(
        @NonNull ChannelHandlerContext context,
        @NonNull PrimitiveCodec<ByteBuf> primitiveCodec,
        @NonNull FrameCodec<ByteBuf> frameCodec,
        @NonNull String logPrefix) {
      super(primitiveCodec, frameCodec);
      this.context = context;
      this.logPrefix = logPrefix;
    }
  
    @Override
    @NonNull
    protected ChannelPromise mergeStates(@NonNull List<ChannelPromise> framePromises) {
      if (framePromises.size() == 1) {
        return framePromises.get(0);
      }
      // We concatenate multiple frames into one segment. When the segment is written, all the frames
      // are written.
      ChannelPromise segmentPromise = context.newPromise();
      ImmutableList<ChannelPromise> dependents = ImmutableList.copyOf(framePromises);
      segmentPromise.addListener(
          future -> {
            if (future.isSuccess()) {
              for (ChannelPromise framePromise : dependents) {
                framePromise.setSuccess();
              }
            } else {
              Throwable cause = future.cause();
              for (ChannelPromise framePromise : dependents) {
                framePromise.setFailure(cause);
              }
            }
          });
      return segmentPromise;
    }
  
    @Override
    @NonNull
    protected List<ChannelPromise> splitState(@NonNull ChannelPromise framePromise, int sliceCount) {
      // We split one frame into multiple slices. When all slices are written, the frame is written.
      List<ChannelPromise> slicePromises = new ArrayList<>(sliceCount);
      for (int i = 0; i < sliceCount; i++) {
        slicePromises.add(context.newPromise());
      }
      GenericFutureListener<Future<Void>> sliceListener =
          new SliceWriteListener(framePromise, slicePromises);
      for (int i = 0; i < sliceCount; i++) {
        slicePromises.get(i).addListener(sliceListener);
      }
      return slicePromises;
    }
  
    @Override
    protected void processSegment(
        @NonNull Segment<ByteBuf> segment, @NonNull ChannelPromise segmentPromise) {
      context.write(segment, segmentPromise);
    }
  
    @Override
    protected void onLargeFrameSplit(@NonNull Frame frame, int frameLength, int sliceCount) {
      LOG.trace(
          "[{}] Frame {} is too large ({} > {}), splitting into {} segments",
          logPrefix,
          frame.streamId,
          frameLength,
          Segment.MAX_PAYLOAD_LENGTH,
          sliceCount);
    }
  
    @Override
    protected void onSegmentFull(
        @NonNull Frame frame, int frameLength, int currentPayloadLength, int currentFrameCount) {
      LOG.trace(
          "[{}] Current self-contained segment is full ({}/{} bytes, {} frames), processing now",
          logPrefix,
          currentPayloadLength,
          Segment.MAX_PAYLOAD_LENGTH,
          currentFrameCount);
    }
  
    @Override
    protected void onSmallFrameAdded(
        @NonNull Frame frame, int frameLength, int currentPayloadLength, int currentFrameCount) {
      LOG.trace(
          "[{}] Added frame {} to current self-contained segment "
              + "(bringing it to {}/{} bytes, {} frames)",
          logPrefix,
          frame.streamId,
          currentPayloadLength,
          Segment.MAX_PAYLOAD_LENGTH,
          currentFrameCount);
    }
  
    @Override
    protected void onLastSegmentFlushed(int currentPayloadLength, int currentFrameCount) {
      LOG.trace(
          "[{}] Flushing last self-contained segment ({}/{} bytes, {} frames)",
          logPrefix,
          currentPayloadLength,
          Segment.MAX_PAYLOAD_LENGTH,
          currentFrameCount);
    }
  
    @NotThreadSafe
    static class SliceWriteListener implements GenericFutureListener<Future<Void>> {
  
      private final ChannelPromise parentPromise;
      private final List<ChannelPromise> slicePromises;
  
      // All slices are written to the same channel, and the segment is built from the Flusher which
      // also runs on the same event loop, so we don't need synchronization.
      private int remainingSlices;
  
      SliceWriteListener(@NonNull ChannelPromise parentPromise, List<ChannelPromise> slicePromises) {
        this.parentPromise = parentPromise;
        this.slicePromises = slicePromises;
        this.remainingSlices = slicePromises.size();
      }
  
      @Override
      public void operationComplete(@NonNull Future<Void> future) {
        if (!parentPromise.isDone()) {
          if (future.isSuccess()) {
            remainingSlices -= 1;
            if (remainingSlices == 0) {
              parentPromise.setSuccess();
            }
          } else {
            // If any slice fails, we can immediately mark the whole frame as failed:
            parentPromise.setFailure(future.cause());
            // Cancel any remaining slice, Netty will not send the bytes.
            for (ChannelPromise slicePromise : slicePromises) {
              slicePromise.cancel(/*Netty ignores this*/ false);
            }
          }
        }
      }
    }
  }
  