import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.*;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapreduce.*;
import org.apache.hadoop.mapreduce.lib.input.*;
import org.apache.hadoop.mapreduce.lib.output.*;
import org.apache.hadoop.util.*;

public class ArticlesAndWords extends Configured implements Tool {
  public static class TheMapper extends Mapper<Text, Text, Text, IntWritable>{
    private Text word = new Text();
    private IntWritable zero = new IntWritable(0);
    private IntWritable one = new IntWritable(1);

    public void map(Text key, Text value, Context context) throws IOException, InterruptedException {
      context.write(key, zero);
      for (String token : value.toString().split("\\W+")) {
        word.set(token);
        context.write(word, one);
      }
    }
  }

  public static class ThePartitioner extends Partitioner<Text, IntWritable> {
    public int getPartition(Text key, IntWritable value, int numPartitions) {
      return value.get();
    }
  }

  public static class TheCombiner extends Reducer<Text, IntWritable, Text, IntWritable> {
    public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
      for (IntWritable value : values) {
        context.write(key, value);
        return;
      }
    }
  }

  public static class TheReducer extends Reducer<Text, IntWritable, Text, NullWritable> {
    public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
      context.write(key, NullWritable.get());
    }
  }
  
  public int run(String[] args) throws Exception {
    if (args.length < 2) {
      System.err.printf("Usage: %s.jar in-path out-path", this.getClass().getName());
      return 1;
    }

    Job job = new Job(getConf(), this.getClass().getName());

    job.setJarByClass(this.getClass());
    job.setMapperClass(TheMapper.class);
    job.setPartitionerClass(ThePartitioner.class);
    job.setCombinerClass(TheCombiner.class);
    job.setReducerClass(TheReducer.class);
    job.setOutputKeyClass(Text.class);
    job.setOutputValueClass(NullWritable.class);
    job.setMapOutputValueClass(IntWritable.class);

    job.setInputFormatClass(KeyValueTextInputFormat.class);

    FileInputFormat.addInputPath(job, new Path(args[0]));
    FileOutputFormat.setOutputPath(job, new Path(args[1]));

    return job.waitForCompletion(true) ? 0 : 1;
  }

  public static void main(String[] args) throws Exception {
    int res = ToolRunner.run(new ArticlesAndWords(), args);

    System.exit(res);
  }
}