/*
    * 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.giraph.writable.kryo.serializers;
  
  import java.io.DataInputStream;
  import java.io.DataOutputStream;
  import java.io.IOException;
  
  import org.apache.giraph.utils.ReflectionUtils;
  import org.apache.giraph.utils.WritableUtils;
  import org.apache.hadoop.io.Writable;
  
  import com.esotericsoftware.kryo.Kryo;
  import com.esotericsoftware.kryo.Serializer;
  import com.esotericsoftware.kryo.io.Input;
  import com.esotericsoftware.kryo.io.Output;
  
  /**
   * A custom Serializer that will call the Writable methods defined by the
   * object itself to serialize the object, instead of Kryo auto-magically
   * serializing
   *
   * @param <T> Object type, should implement Writable
   */
  
  public class DirectWritableSerializer<T extends Writable>
      extends Serializer<T> {
  
    @Override
    public void write(Kryo kryo, Output output, T object) {
      try {
        object.write(new DataOutputStream(output));
      } catch (IOException e) {
        throw new RuntimeException(
            "DirectWritableSerializer.write calling Writable method of class: " +
              object.getClass().getName() + " encountered issues", e);
      }
    }
  
    @Override
    public T read(Kryo kryo, Input input, Class<T> type) {
      try {
        T object = create(kryo, input, type);
        kryo.reference(object);
        object.readFields(new DataInputStream(input));
  
        return object;
      } catch (IOException e) {
        throw new RuntimeException(
            "DirectWritableSerializer.read calling Writable method of class: " +
            type.getName() + " encountered issues", e);
      }
    }
  
    @Override
    public T copy(Kryo kryo, T original) {
      return WritableUtils.createCopy(original);
    }
  
    /**
     * Used by {@link #read(Kryo, Input, Class)} to create the new object.
     * This can be overridden to customize object creation, eg to call a
     * constructor with arguments. The default implementation
     * uses {@link Kryo#newInstance(Class)}.
     *
     * @param kryo Kryo object instance
     * @param input Input
     * @param type Type of the class to create
     * @return New instance of wanted type
     */
    protected T create(Kryo kryo, Input input, Class<T> type) {
      return ReflectionUtils.newInstance(type);
    }
  }