/*
    * 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:
    *
    *   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 io.netty.handler.codec.serialization;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.ByteBufOutputStream;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.MessageToByteEncoder;
  import io.netty.util.Attribute;
  import io.netty.util.AttributeKey;
  
  import java.io.ObjectInputStream;
  import java.io.ObjectOutputStream;
  import java.io.OutputStream;
  import java.io.Serializable;
  
  /**
   * An encoder which serializes a Java object into a {@link ByteBuf}
   * (interoperability version).
   * <p>
   * This encoder is interoperable with the standard Java object streams such as
   * {@link ObjectInputStream} and {@link ObjectOutputStream}.
   */
  public class CompatibleObjectEncoder extends MessageToByteEncoder<Serializable> {
      private final int resetInterval;
      private int writtenObjects;
  
      /**
       * Creates a new instance with the reset interval of {@code 16}.
       */
      public CompatibleObjectEncoder() {
          this(16); // Reset at every sixteen writes
      }
  
      /**
       * Creates a new instance.
       *
       * @param resetInterval
       *        the number of objects between {@link ObjectOutputStream#reset()}.
       *        {@code 0} will disable resetting the stream, but the remote
       *        peer will be at the risk of getting {@link OutOfMemoryError} in
       *        the long term.
       */
      public CompatibleObjectEncoder(int resetInterval) {
          if (resetInterval < 0) {
              throw new IllegalArgumentException(
                      "resetInterval: " + resetInterval);
          }
          this.resetInterval = resetInterval;
      }
  
      /**
       * Creates a new {@link ObjectOutputStream} which wraps the specified
       * {@link OutputStream}.  Override this method to use a subclass of the
       * {@link ObjectOutputStream}.
       */
      protected ObjectOutputStream newObjectOutputStream(OutputStream out) throws Exception {
          return new ObjectOutputStream(out);
      }
  
      @Override
      protected void encode(ChannelHandlerContext ctx, Serializable msg, ByteBuf out) throws Exception {
          ObjectOutputStream oos = newObjectOutputStream(new ByteBufOutputStream(out));
          try {
              if (resetInterval != 0) {
                  // Resetting will prevent OOM on the receiving side.
                  writtenObjects ++;
                  if (writtenObjects % resetInterval == 0) {
                      oos.reset();
                  }
              }
  
              oos.writeObject(msg);
              oos.flush();
          } finally {
              oos.close();
          }
      }
  }