import java.io.IOException;
import java.util.Iterator;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.KeyValueTextInputFormat;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

public class CitationHistogram extends Configured implements Tool {
    
    public static class MapClass extends MapReduceBase
        implements Mapper<Text, Text, IntWritable, IntWritable> {
        
        private final static IntWritable uno = new IntWritable(1);
        private IntWritable citationCount = new IntWritable();
        
        public void map(Text key, Text value,
                        OutputCollector<IntWritable, IntWritable> output,
                        Reporter reporter) throws IOException {
                        
	    if (key.toString().indexOf("CITING") == -1)
            {
	    	System.out.println("key = "+key+ " input = " + key);
            	citationCount.set(Integer.parseInt(value.toString()));
            	output.collect(citationCount, uno);
	    }
        }
    }
    
    public static class Reduce extends MapReduceBase
        implements Reducer<IntWritable,IntWritable,IntWritable,IntWritable>
    {
        
        public void reduce(IntWritable key, Iterator<IntWritable> values,
                           OutputCollector<IntWritable, IntWritable>output,
                           Reporter reporter) throws IOException {
                           
            int count = 0;
            while (values.hasNext()) {
                count += values.next().get();
            }
            output.collect(key, new IntWritable(count));
        }
    }
    
    public int run(String[] args) throws Exception {
        Configuration conf = getConf();
        
        JobConf job = new JobConf(conf, CitationHistogram.class);
        
        Path in = new Path(args[0]);
        Path out = new Path(args[1]);
        FileInputFormat.setInputPaths(job, in);
        FileOutputFormat.setOutputPath(job, out);
        
        job.setJobName("CitationHistogram");
        job.setMapperClass(MapClass.class);
        job.setReducerClass(Reduce.class);
        
        job.setInputFormat(KeyValueTextInputFormat.class);
        job.setOutputFormat(TextOutputFormat.class);
        job.setOutputKeyClass(IntWritable.class);
        job.setOutputValueClass(IntWritable.class);
	job.set("key.value.separator.in.input.line", ",");

        
        JobClient.runJob(job);
        
        return 0;
    }
    
    public static void main(String[] args) throws Exception { 
        int res = ToolRunner.run(new Configuration(), 
                                 new CitationHistogram(), 
                                 args);
        
        System.exit(res);
    }
}