/**

This program was created to anonymize files/folders and produce a key file mapping random file names back to the original file names.

**/

import java.io.*;
import java.util.*;

public class Anonymize{
    
    /**
    * Main method that does all of the work. Usage:
    *
    * java Anonymize folderName keyFile.csv
    *
    * @param args[0]=folderName folder that contains the files/folders you wish to anonymize.
    * @param args[1]=keyFile.csv a csv file that is created that contains "New Filename","Original Filename" pairs.    
    */
    public static void main(String[] args) throws Exception{
        if(args.length != 2){
            System.out.println("Program usage is:\njava Anonymize nameOfFolder keyFile.csv");
            System.exit(1);
        }
        File folderName = new File(args[0]);
        if(folderName.isDirectory()){
            HashSet<Integer> usedAlready = new HashSet<>();
            PrintWriter fout = new PrintWriter(new FileWriter(args[1]));
            fout.println("New Name, Original Name");
            Random random = new Random();
            int numberFiles = folderName.listFiles().length;
            for(File current : folderName.listFiles()){
                String name = current.getName();
                String extension = "";
                //get extension if it's a file instead of a folder
                if(name.contains(".")){
                    extension = name.substring(name.lastIndexOf("."));
                }
                //pick a random number to change the folder/file name to
                int rename = random.nextInt(numberFiles*10);
                while(usedAlready.contains(rename)){
                    //increment the random number in the unlikely event of a collision
                    rename = rename+1;
                }
                current.renameTo(new File(folderName+File.separator+Integer.toString(rename)+extension));
                //store random number so it isn't used again
                usedAlready.add(rename);
                fout.println(Integer.toString(rename)+extension+","+name);
            }
            fout.close();
        } else{
            System.out.println("Folder required. Program usage is:\njava Anonymize nameOfFolder keyFile.csv");
            System.exit(1);
        }
    }
}