/*
    * Copyright 2012 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.sctp;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.CompositeByteBuf;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelInboundHandler;
  import io.netty.channel.sctp.SctpMessage;
  import io.netty.handler.codec.CodecException;
  import io.netty.handler.codec.MessageToMessageDecoder;
  import io.netty.util.collection.IntObjectHashMap;
  import io.netty.util.collection.IntObjectMap;
  
  import java.util.ArrayList;
  import java.util.List;
  
  import static io.netty.util.internal.ObjectUtil.checkPositive;
  
  /**
   * {@link MessageToMessageDecoder} which will take care of handle fragmented {@link SctpMessage}s, so
   * only <strong>complete</strong> {@link SctpMessage}s will be forwarded to the next
   * {@link ChannelInboundHandler}.
   */
  public class SctpMessageCompletionHandler extends MessageToMessageDecoder<SctpMessage> {
      private static final int DEFAULT_MAX_BUFFERED_BYTES = 16 * 1024 * 1024;
  
      private final IntObjectMap<List<ByteBuf>> incompleteSctpMessages = new IntObjectHashMap<List<ByteBuf>>();
      private final int maxIncompleteSctpMessages;
      private final int maxFragments;
      private final int maxBufferedBytes;
      private long bufferedBytes;
  
      public SctpMessageCompletionHandler() {
          this(128, 128);
      }
  
      /**
       * Create a new instance.
       *
       * @param maxIncompleteSctpMessages the maximum number of incomplete sctp message inflight.
       * @param maxFragments              the maximum number of fragments per sctp message.
       */
      public SctpMessageCompletionHandler(int maxIncompleteSctpMessages, int maxFragments) {
          this(maxIncompleteSctpMessages, maxFragments, DEFAULT_MAX_BUFFERED_BYTES);
      }
  
      /**
       * Create a new instance.
       *
       * @param maxIncompleteSctpMessages the maximum number of incomplete sctp message inflight.
       * @param maxFragments              the maximum number of fragments per sctp message.
       * @param maxBufferedBytes          the maximum number of bytes buffered by incomplete sctp messages.
       */
      public SctpMessageCompletionHandler(int maxIncompleteSctpMessages, int maxFragments, int maxBufferedBytes) {
          super(SctpMessage.class);
          this.maxIncompleteSctpMessages = checkPositive(maxIncompleteSctpMessages, "maxIncompleteSctpMessages");
          this.maxFragments = checkPositive(maxFragments, "maxFragments");
          this.maxBufferedBytes = checkPositive(maxBufferedBytes, "maxBufferedBytes");
      }
  
      @Override
      protected void decode(ChannelHandlerContext ctx, SctpMessage msg, List<Object> out) throws Exception {
          final ByteBuf byteBuf = msg.content();
          final int protocolIdentifier = msg.protocolIdentifier();
          final int streamIdentifier = msg.streamIdentifier();
          final boolean isComplete = msg.isComplete();
          final boolean isUnordered = msg.isUnordered();
  
          List<ByteBuf> frag = incompleteSctpMessages.get(streamIdentifier);
          if (frag == null) {
              // No previous fragments.
              if (isComplete) {
                  out.add(msg.retain());
              } else {
                  if (maxIncompleteSctpMessages <= incompleteSctpMessages.size()) {
                      throw new CodecException(
                              "Too many incomplete sctp messages in flight: " + maxIncompleteSctpMessages);
                  }
                  checkBufferedBytes(byteBuf);
                  //first incomplete message
                  frag = new ArrayList<ByteBuf>();
                  frag.add(byteBuf.retain());
                  bufferedBytes += byteBuf.readableBytes();
                  incompleteSctpMessages.put(streamIdentifier, frag);
             }
         } else {
             if (maxFragments <= frag.size()) {
                 throw new CodecException("Too many fragments for sctp message: " + maxFragments);
             }
             checkBufferedBytes(byteBuf);
             frag.add(byteBuf.retain());
             bufferedBytes += byteBuf.readableBytes();
             if (isComplete) {
                 // Is complete so remove it.
                 incompleteSctpMessages.remove(streamIdentifier);
                 CompositeByteBuf composite = ctx.alloc().compositeBuffer();
 
                 for (int i = 0; i < frag.size(); i++) {
                     composite.addComponent(true, frag.get(i));
                 }
                 // last message to complete
                 SctpMessage assembledMsg = new SctpMessage(
                         protocolIdentifier,
                         streamIdentifier,
                         isUnordered,
                         composite);
                 out.add(assembledMsg);
                 removeBufferedBytes(frag);
             }
         }
     }
 
     private void checkBufferedBytes(ByteBuf byteBuf) {
         int readableBytes = byteBuf.readableBytes();
         if (readableBytes > maxBufferedBytes - bufferedBytes) {
             throw new CodecException("Too many buffered bytes for incomplete sctp messages: " + maxBufferedBytes);
         }
     }
 
     private void removeBufferedBytes(List<ByteBuf> buffers) {
         for (ByteBuf buffer : buffers) {
             bufferedBytes -= buffer.readableBytes();
         }
     }
 
     @Override
     public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
         for (List<ByteBuf> buffers: incompleteSctpMessages.values()) {
             for (ByteBuf buffer: buffers) {
                 buffer.release();
             }
         }
         incompleteSctpMessages.clear();
         bufferedBytes = 0;
         super.handlerRemoved(ctx);
     }
 
     @Override
     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
         super.exceptionCaught(ctx, cause);
         ctx.close();
     }
 }