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 *  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
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package com.soteradefense.dga.louvain.mapreduce;

import com.soteradefense.dga.DGAConfiguration;
import com.soteradefense.dga.DGALoggingUtil;
import com.soteradefense.dga.louvain.giraph.LouvainVertexWritable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map.Entry;

 * Map reduce job to compress a graph in such a way that each community is represented by a single node.
 * <p/>
 * input format:  see LouvainVertexOutputFormat
 * output format  see LouvainVertexInputFormat
 * *** the input to this job is output of the BSP computation, the output of this job is the input to the next stage of BSP.
public class CommunityCompression extends Configured implements Tool {

    private static final Logger logger = LoggerFactory.getLogger(CommunityCompression.class);

    private String inputPath;
    private String outputPath;
    private DGAConfiguration dgaConfiguration;

    public CommunityCompression(String inputPath, String outputPath, DGAConfiguration dgaConfiguration) {
        this.inputPath = inputPath;
        this.outputPath = outputPath;
        this.dgaConfiguration = dgaConfiguration;

    public int run(String[] args) throws Exception {
        Configuration mrConf = this.getConf();
        for (java.util.Map.Entry<String, String> entry : dgaConfiguration.getSystemProperties().entrySet()) {
            mrConf.set(entry.getKey(), entry.getValue());

        Job job = Job.getInstance(mrConf);
        Path in = new Path(inputPath);
        Path out = new Path(outputPath);

        FileInputFormat.setInputPaths(job, in);
        FileOutputFormat.setOutputPath(job, out);




        logger.debug("Running Mapreduce step with job configuration: {}", job);

        return job.waitForCompletion(false) ? 0 : 1;

    public static class Map extends Mapper<LongWritable, Text, Text, LouvainVertexWritable> {

        public void setup(Context context) throws IOException, InterruptedException {

        public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {

            String[] tokens = value.toString().trim().split("\t");
            if (3 > tokens.length) {
                throw new IllegalArgumentException("Expected 4 cols: got " + tokens.length + "  from line: " + tokens.toString());

            Text outKey = new Text(tokens[1]); // group by community
            String edgeListStr = (tokens.length == 3) ? "" : tokens[3];
            LouvainVertexWritable outValue = LouvainVertexWritable.fromTokens(tokens[2], edgeListStr);
            context.write(outKey, outValue);

    public static class Reduce extends Reducer<Text, LouvainVertexWritable, Text, Text> {

        public void setup(Context context) throws IOException, InterruptedException {

        public void reduce(Text key, Iterable<LouvainVertexWritable> values, Context context) throws IOException, InterruptedException {
            String communityId = key.toString();
            long weight = 0;
            HashMap<String, Long> edgeMap = new HashMap<String, Long>();
            for (LouvainVertexWritable vertex : values) {
                weight += vertex.getWeight();
                for (Entry<String, Long> entry : vertex.getEdges().entrySet()) {
                    String entryKey = entry.getKey();

                    if (entryKey.equals(communityId)) {
                        weight += entry.getValue();
                    } else if (edgeMap.containsKey(entryKey)) {
                        long w = edgeMap.get(entryKey) + entry.getValue();
                        edgeMap.put(entryKey, w);
                    } else {
                        edgeMap.put(entry.getKey(), entry.getValue());

            StringBuilder b = new StringBuilder();
            for (Entry<String, Long> entry : edgeMap.entrySet()) {
            b.setLength(b.length() - 1);

            context.write(new Text(key.toString()), new Text(b.toString()));