/*
 * 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.mapred;

import java.io.IOException;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reporter;
import org.apache.yetus.audience.InterfaceAudience;

/**
 * Pass the given key and record as-is to reduce
 */
@InterfaceAudience.Public
public class IdentityTableMap extends MapReduceBase
  implements TableMap<ImmutableBytesWritable, Result> {

  /** constructor */
  public IdentityTableMap() {
    super();
  }

  /**
   * Use this before submitting a TableMap job. It will appropriately set up the JobConf.
   * @param table   table name
   * @param columns columns to scan
   * @param mapper  mapper class
   * @param job     job configuration
   */
  @SuppressWarnings("unchecked")
  public static void initJob(String table, String columns, Class<? extends TableMap> mapper,
    JobConf job) {
    TableMapReduceUtil.initTableMapJob(table, columns, mapper, ImmutableBytesWritable.class,
      Result.class, job);
  }

  /**
   * Pass the key, value to reduce
   */
  public void map(ImmutableBytesWritable key, Result value,
    OutputCollector<ImmutableBytesWritable, Result> output, Reporter reporter) throws IOException {

    // convert
    output.collect(key, value);
  }
}
