/******************************************************************************
 * This program implements the XOR stream cipher.
 * 
 * Copyright © 2021 Richard Lesh.  All rights reserved.
 *****************************************************************************/

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import org.pureprogrammer.Utils;

public class XORCipher {

    static void processFile(String fromFilespec, String toFilespec, String password) throws IOException {
        BufferedOutputStream ofh = new BufferedOutputStream(new FileOutputStream(toFilespec));

        BufferedInputStream ifh = new BufferedInputStream(new FileInputStream(fromFilespec));
        int c;
        final int PLEN = Utils.cpLength(password);
        int count = 0;
        while ((c = Utils.getbyte(ifh)) != -1) {
            int x = c ^ Utils.cpAt(password, count % PLEN);
            ofh.write(x);
            ++count;
        }
        try {ofh.close();} catch (IOException ex) {};
        try {ifh.close();} catch (IOException ex) {};
    }

    public static void main(String[] args) {
        if (args.length != 3) {
            System.out.println(Utils.join("", "Syntax: ", "XORCipher", " {fromFilespec} {toFilespec} {password}"));
            System.exit(1);
        }
        String fromFilespec = args[0];
        String toFilespec = args[1];
        String password = args[2];

        try {
            processFile(fromFilespec, toFilespec, password);
        } catch (IOException ex) {
            System.out.println(Utils.join("", "Error: ", Utils.exceptionMessage(ex)));
        }
    }
}