// Created as a template for  Advanced Database Systems 2019

import java.io.*;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapreduce.*;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class SomeMapReduce_ex1a {
    public static class MyMapper extends Mapper<Object, Text, Text, TextPair> {
        public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
            String[] result = CSVSplitter.split(value.toString());
            try{
                context.write(new Text(result[7]), new TextPair(result[6].toString(), Integer.toString(Integer.parseInt(result[5]))));
            }catch(NumberFormatException e){} // not an integer (csv header line) or no value.
        }
    }
    public static class MyReducer extends Reducer<Text, TextPair, Text, TextPair> {
        public void reduce(Text key, Iterable<TextPair> values, Context context) throws IOException, InterruptedException {
            TextPair max = null;
            for (TextPair val : values) {
                if (max == null){
                    max = val;
                    continue;
                }
                if (Integer.parseInt(max.getSecond().toString()) < Integer.parseInt(val.getSecond().toString())){
                    max = val;
                    continue;
                }
            }
            if(Integer.parseInt(max.getSecond().toString()) > 0) {
                context.write(key, max);
            }
        }
    }
    public static void main(String[] args) throws Exception {
        Configuration conf1 = new Configuration();
        conf1.set("mapreduce.output.textoutputformat.separator",",");  // This ensures that output is comma separated
        Job job = Job.getInstance(conf1);
        job.setJarByClass(SomeMapReduce_ex1a.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(TextPair.class);
        job.setMapperClass(MyMapper.class);
        job.setReducerClass(MyReducer.class);
        job.setCombinerClass(MyReducer.class); // To allow the reducer to be used as a Combiner too
//    job.setNumReduceTasks(8);     // Uncomment this to run the job with more than one Reduce tasks. Depending on the system, this may produce a speedup.
        FileInputFormat.setInputPaths(job, new Path(args[1]));
        FileOutputFormat.setOutputPath(job, new Path(args[0]));
        boolean status = job.waitForCompletion(true);
        if (status) {
            System.exit(0);
        } else {
            System.exit(1);
        }
    }
}