package com.myFirstHadoop;

import java.io.IOException;

import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.Path;

import org.apache.hadoop.io.IntWritable;

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.output.FileOutputFormat;

import org.apache.hadoop.util.GenericOptionsParser;

public class WorkCount {

    public static class TokenizerMapper extends Mapper<Object, Text, Text, IntWritable>{

        private final static IntWritable one=new IntWritable(1);

        private Text word=new Text();

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

            StringTokenizer itr=new StringTokenizer(value.toString());

            while(itr.hasMoreTokens()){

                word.set(itr.nextToken());

                context.write(word, one);

            }

        }

    }

    public static class IntSumReducer extends Reducer<Text, IntWritable, Text, IntWritable>{

        private IntWritable result=new IntWritable();

        public void reduce(Text key,Iterable<IntWritable> values,Context context) throws IOException, InterruptedException{

            int sum=0;

            for(IntWritable val:values){

                sum+=val.get();

            }

            result.set(sum);

            context.write(key, result);

        }

    }

    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {

        Configuration conf=new Configuration();

        String[] otherArgs=new GenericOptionsParser(conf,args).getRemainingArgs();

        if(otherArgs.length<2){

            System.err.println("Useage:wordCount <in> [<in> ...] <out>");

            System.exit(2);

        }

        Job job=new Job(conf,"word count");

        job.setJarByClass(WorkCount.class);

        job.setMapperClass(TokenizerMapper.class);

        job.setCombinerClass(IntSumReducer.class);

        job.setReducerClass(IntSumReducer.class);

        job.setOutputKeyClass(Text.class);

        job.setOutputValueClass(IntWritable.class);

        for(int i=0;i<otherArgs.length-1;++i){

            FileInputFormat.addInputPath(job, new Path(otherArgs[i]));

            FileOutputFormat.setOutputPath(job,new Path(otherArgs[otherArgs.length-1]));

            System.exit(job.waitForCompletion(true)?0:1);

        }

    }

}