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 WordCount {
    
    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();
        conf.addResource(new Path("/usr/hadoop-1.0.3/conf/core-site.xml"));
        String[] otherArgs = new GenericOptionsParser(conf,args).getRemainingArgs();
        
        Job job = new Job(conf,"WordCount");
        
        job.setJarByClass(WordCount.class);
        
        job.setMapperClass(TokenizerMapper.class);
        job.setCombinerClass(IntSumReducer.class);
        job.setReducerClass(IntSumReducer.class);
        
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        
        FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
        FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
        
        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}