/**
 * 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.horn.bsp;

import java.io.IOException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hama.bsp.BSP;
import org.apache.hama.bsp.BSPPeer;
import org.apache.hama.bsp.sync.SyncException;
import org.apache.hama.commons.io.VectorWritable;
import org.apache.hama.ml.perception.MLPMessage;
import org.apache.hama.ml.util.DefaultFeatureTransformer;
import org.apache.hama.ml.util.FeatureTransformer;

/**
 * The trainer that is used to train the {@link SmallLayeredNeuralNetwork} with
 * BSP. The trainer would read the training data and obtain the trained
 * parameters of the model.
 * 
 */
public abstract class NeuralNetworkTrainer extends
    BSP<LongWritable, VectorWritable, NullWritable, NullWritable, MLPMessage> {

  protected static final Log LOG = LogFactory
      .getLog(NeuralNetworkTrainer.class);

  protected Configuration conf;
  protected int maxIteration;
  protected int batchSize;
  protected String trainingMode;
  
  protected FeatureTransformer featureTransformer;
  
  @Override
  final public void setup(
      BSPPeer<LongWritable, VectorWritable, NullWritable, NullWritable, MLPMessage> peer)
      throws IOException, SyncException, InterruptedException {
    conf = peer.getConfiguration();
    featureTransformer = new DefaultFeatureTransformer();
    this.extraSetup(peer);
  }

  /**
   * Handle extra setup for sub-classes.
   * 
   * @param peer
   * @throws IOException
   * @throws SyncException
   * @throws InterruptedException
   */
  protected void extraSetup(
      BSPPeer<LongWritable, VectorWritable, NullWritable, NullWritable, MLPMessage> peer)
      throws IOException, SyncException, InterruptedException {

  }

  /**
   * {@inheritDoc}
   */
  @Override
  public abstract void bsp(
      BSPPeer<LongWritable, VectorWritable, NullWritable, NullWritable, MLPMessage> peer)
      throws IOException, SyncException, InterruptedException;

  @Override
  public void cleanup(
      BSPPeer<LongWritable, VectorWritable, NullWritable, NullWritable, MLPMessage> peer)
      throws IOException {
    this.extraCleanup(peer);
    // write model to modelPath
  }

  /**
   * Handle cleanup for sub-classes. Write the trained model back.
   * 
   * @param peer
   * @throws IOException
   * @throws SyncException
   * @throws InterruptedException
   */
  protected void extraCleanup(
      BSPPeer<LongWritable, VectorWritable, NullWritable, NullWritable, MLPMessage> peer)
      throws IOException {

  }

}