/**
    * 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 org.apache.hadoop.hbase.security;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.Unpooled;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelOutboundHandlerAdapter;
  import io.netty.channel.ChannelPromise;
  import io.netty.channel.CoalescingBufferQueue;
  import io.netty.util.ReferenceCountUtil;
  import io.netty.util.concurrent.PromiseCombiner;
  
  import java.io.IOException;
  
  import javax.security.sasl.SaslClient;
  
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  
  /**
   * wrap sasl messages.
   */
  @InterfaceAudience.Private
  public class SaslWrapHandler extends ChannelOutboundHandlerAdapter {
  
    private final SaslClient saslClient;
  
    private CoalescingBufferQueue queue;
  
    public SaslWrapHandler(SaslClient saslClient) {
      this.saslClient = saslClient;
    }
  
    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
      queue = new CoalescingBufferQueue(ctx.channel());
    }
  
    @Override
    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise)
        throws Exception {
      if (msg instanceof ByteBuf) {
        queue.add((ByteBuf) msg, promise);
      } else {
        ctx.write(msg, promise);
      }
    }
  
    @Override
    public void flush(ChannelHandlerContext ctx) throws Exception {
      if (queue.isEmpty()) {
        return;
      }
      ByteBuf buf = null;
      try {
        ChannelPromise promise = ctx.newPromise();
        int readableBytes = queue.readableBytes();
        buf = queue.remove(readableBytes, promise);
        byte[] bytes = new byte[readableBytes];
        buf.readBytes(bytes);
        byte[] wrapperBytes = saslClient.wrap(bytes, 0, bytes.length);
        ChannelPromise lenPromise = ctx.newPromise();
        ctx.write(ctx.alloc().buffer(4).writeInt(wrapperBytes.length), lenPromise);
        ChannelPromise contentPromise = ctx.newPromise();
        ctx.write(Unpooled.wrappedBuffer(wrapperBytes), contentPromise);
        PromiseCombiner combiner = new PromiseCombiner();
        combiner.addAll(lenPromise, contentPromise);
        combiner.finish(promise);
        ctx.flush();
      } finally {
        if (buf != null) {
          ReferenceCountUtil.safeRelease(buf);
        }
      }
    }
  
    @Override
    public void close(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
      if (!queue.isEmpty()) {
        queue.releaseAndFailAll(new IOException("Connection closed"));
      }
      ctx.close(promise);
    }
  }