/**
 *        CloudGraph Community Edition (CE) License
 * 
 * This is a community release of CloudGraph, a dual-license suite of
 * Service Data Object (SDO) 2.1 services designed for relational and 
 * big-table style "cloud" databases, such as HBase and others. 
 * This particular copy of the software is released under the 
 * version 2 of the GNU General Public License. CloudGraph was developed by 
 * TerraMeta Software, Inc.
 * 
 * Copyright (c) 2013, TerraMeta Software, Inc. All rights reserved.
 * 
 * General License information can be found below.
 * 
 * This distribution may include materials developed by third
 * parties. For license and attribution notices for these
 * materials, please refer to the documentation that accompanies
 * this distribution (see the "Licenses for Third-Party Components"
 * appendix) or view the online documentation at 
 * <http://cloudgraph.org/licenses/>. 
 */
package org.cloudgraph.hbase.mapreduce;

import java.io.IOException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.Mapper;
import org.cloudgraph.mapreduce.GraphMutator;
import org.cloudgraph.mapreduce.GraphWritable;

import commonj.sdo.DataGraph;

/**
 * Supplies fully realized data {@link GraphWritable graphs} as the input value to MapReduce <code>Mapper</code> 
 * client subclasses, the input key being an HBase row key <a href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/io/ImmutableBytesWritable.html">bytes</a> and the
 * input value being a {@link GraphWritable} assembled from one or more underlying HBase table(s)/row(s).
 * 
 * The data graphs supplied to the code>Mapper</code> are ready to modify but the graph change
 * summary must be set to track changes, so changes will be detected.    
 * See the below code sample based on the Wikipedia domain model
 * which adds a fictitious category page link to each input graph.  
 *<p>
 *<pre>
 *public class PageGraphModifier extends GraphXmlMapper<ImmutableBytesWritable, GraphWritable> {
 *    public void map(ImmutableBytesWritable offset, GraphWritable graph, Context context) throws IOException {
 *    
 *        // track changes
 *        graph.getDataGraph().getChangeSummary().beginLogging();

 *        Page page = (Page)graph.getDataGraph().getRootObject();
 *        Categorylinks link = page.createCategorylinks();
 *        link.setClTo("Some Category Page");
 *        link.setClTimestamp((new Date()).toString());
 *
 *        // commit above changes
 *        super.commit(row, graph, context);
 *    }
 *}
 *</pre>
 *</p>
 * 
 * <p>
 * Data graphs of any size of complexity may be supplied to MapReduce jobs including graphs where the underlying
 * domain model contains instances of multiple inheritance. The set of data graphs is provided to
 * a MapReduce job using a <a href="http://plasma-sdo.org/org/plasma/query/Query.html">query</a>, typically 
 * supplied using {@link GraphMapReduceSetup}.    
 * </p>
 * <p>
 * Data graphs are assembled within a {@link GraphRecordReader} based on the detailed selection criteria within a given <a href="http://plasma-sdo.org/org/plasma/query/Query.html">query</a>, and
 * may be passed to a {@link GraphRecordRecognizer} and potentially screened from
 * client {@link GraphMapper} extensions potentially illuminating business logic dedicated to identifying
 * specific records.   
 * </p>
 * 
 * @param <KEYOUT> the output key type
 * @param <VALUEOUT> the output value type
 * 
 * @see org.cloudgraph.mapreduce.GraphWritable
 * @see org.cloudgraph.hbase.mapreduce.GraphRecordReader
 * @see org.cloudgraph.hbase.mapreduce.GraphMapReduceSetup
 * 
 * @author Scott Cinnamond
 * @since 0.5.8
 */
public class GraphMapper<KEYOUT, VALUEOUT>
extends Mapper<ImmutableBytesWritable, GraphWritable, KEYOUT, VALUEOUT> implements GraphMutator {
	
    private static Log log = LogFactory.getLog(GraphMapper.class);
    private GraphServiceDelegate serviceDelegate;
	
    /**
     * Default constructor
     */
	public GraphMapper() {
		this.serviceDelegate = new GraphServiceDelegate();
	}
	
	/*
	 * (non-Javadoc)
	 * @see org.apache.hadoop.mapreduce.Mapper#map(KEYIN, VALUEIN, org.apache.hadoop.mapreduce.Mapper.Context)
	 */
	@Override
	public void map(ImmutableBytesWritable row, GraphWritable graph,
			Context context) throws IOException {
        //no behavior
	}

	/*
	 * (non-Javadoc)
	 * @see org.cloudgraph.hbase.mapreduce.GraphMutator#commit(commonj.sdo.DataGraph, org.apache.hadoop.mapreduce.JobContext)
	 */
	@Override
	public void commit(DataGraph graph,
			JobContext jobContext) throws IOException {
		this.serviceDelegate.commit(graph, jobContext);
	}

	@Override
	public void commit(DataGraph[] graphs, JobContext jobContext)
			throws IOException {
		this.serviceDelegate.commit(graphs, jobContext);
	}
}