/**
    *
    * 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.mapreduce;
  
  import java.io.IOException;
  import java.util.TreeMap;
  
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.HBaseConfiguration;
  import org.apache.hadoop.hbase.client.Put;
  import org.apache.hadoop.hbase.client.Result;
  import org.apache.hadoop.hbase.client.Scan;
  import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.mapreduce.Job;
  import org.apache.hadoop.mapreduce.Mapper;
  import org.apache.hadoop.util.GenericOptionsParser;
  
  /**
   * Example map/reduce job to construct index tables that can be used to quickly
   * find a row based on the value of a column. It demonstrates:
   * <ul>
   * <li>Using TableInputFormat and TableMapReduceUtil to use an HTable as input
   * to a map/reduce job.</li>
   * <li>Passing values from main method to children via the configuration.</li>
   * <li>Using MultiTableOutputFormat to output to multiple tables from a
   * map/reduce job.</li>
   * <li>A real use case of building a secondary index over a table.</li>
   * </ul>
   *
   * <h3>Usage</h3>
   *
   * <p>
   * Modify ${HADOOP_HOME}/conf/hadoop-env.sh to include the hbase jar, the
   * zookeeper jar (can be found in lib/ directory under HBase root, the examples output directory,
   * and the hbase conf directory in HADOOP_CLASSPATH, and then run
   * <tt><strong>bin/hadoop org.apache.hadoop.hbase.mapreduce.IndexBuilder TABLE_NAME COLUMN_FAMILY ATTR [ATTR ...]</strong></tt>
   * </p>
   *
   * <p>
   * To run with the sample data provided in index-builder-setup.rb, use the
   * arguments <strong><tt>people attributes name email phone</tt></strong>.
   * </p>
   *
   * <p>
   * This code was written against HBase 0.21 trunk.
   * </p>
   */
  public class IndexBuilder {
    /** the column family containing the indexed row key */
    public static final byte[] INDEX_COLUMN = Bytes.toBytes("INDEX");
    /** the qualifier containing the indexed row key */
    public static final byte[] INDEX_QUALIFIER = Bytes.toBytes("ROW");
  
    /**
     * Internal Mapper to be run by Hadoop.
     */
    public static class Map extends
        Mapper<ImmutableBytesWritable, Result, ImmutableBytesWritable, Put> {
      private byte[] family;
      private TreeMap<byte[], ImmutableBytesWritable> indexes;
  
      @Override
      protected void map(ImmutableBytesWritable rowKey, Result result, Context context)
          throws IOException, InterruptedException {
        for(java.util.Map.Entry<byte[], ImmutableBytesWritable> index : indexes.entrySet()) {
          byte[] qualifier = index.getKey();
          ImmutableBytesWritable tableName = index.getValue();
          byte[] value = result.getValue(family, qualifier);
          if (value != null) {
            // original: row 123 attribute:phone 555-1212
            // index: row 555-1212 INDEX:ROW 123
            Put put = new Put(value);
            put.add(INDEX_COLUMN, INDEX_QUALIFIER, rowKey.get());
            context.write(tableName, put);
          }
        }
      }
  
      @Override
      protected void setup(Context context) throws IOException,
          InterruptedException {
        Configuration configuration = context.getConfiguration();
       String tableName = configuration.get("index.tablename");
       String[] fields = configuration.getStrings("index.fields");
       String familyName = configuration.get("index.familyname");
       family = Bytes.toBytes(familyName);
       indexes = new TreeMap<byte[], ImmutableBytesWritable>(Bytes.BYTES_COMPARATOR);
       for(String field : fields) {
         // if the table is "people" and the field to index is "email", then the
         // index table will be called "people-email"
         indexes.put(Bytes.toBytes(field),
             new ImmutableBytesWritable(Bytes.toBytes(tableName + "-" + field)));
       }
     }
   }
 
   /**
    * Job configuration.
    */
   public static Job configureJob(Configuration conf, String [] args)
   throws IOException {
     String tableName = args[0];
     String columnFamily = args[1];
     System.out.println("****" + tableName);
     conf.set(TableInputFormat.SCAN, TableMapReduceUtil.convertScanToString(new Scan()));
     conf.set(TableInputFormat.INPUT_TABLE, tableName);
     conf.set("index.tablename", tableName);
     conf.set("index.familyname", columnFamily);
     String[] fields = new String[args.length - 2];
     System.arraycopy(args, 2, fields, 0, fields.length);
     conf.setStrings("index.fields", fields);
     Job job = new Job(conf, tableName);
     job.setJarByClass(IndexBuilder.class);
     job.setMapperClass(Map.class);
     job.setNumReduceTasks(0);
     job.setInputFormatClass(TableInputFormat.class);
     job.setOutputFormatClass(MultiTableOutputFormat.class);
     return job;
   }
 
   public static void main(String[] args) throws Exception {
     Configuration conf = HBaseConfiguration.create();
     String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
     if(otherArgs.length < 3) {
       System.err.println("Only " + otherArgs.length + " arguments supplied, required: 3");
       System.err.println("Usage: IndexBuilder <TABLE_NAME> <COLUMN_FAMILY> <ATTR> [<ATTR> ...]");
       System.exit(-1);
     }
     Job job = configureJob(conf, otherArgs);
     System.exit(job.waitForCompletion(true) ? 0 : 1);
   }
 }