#!/usr/bin/perl
#
# Written by Travis Kent Beste
# Wed Aug  1 17:56:12 CDT 2007
#
# $Id: rot16.pl,v 1.1 2007/09/13 02:26:47 travis Exp $
# $Source: /cvs_repository/encryption/rot16.pl,v $

# y/A-Za-z/N-ZA-Mn-za-m/;
# A character range may be specified with a hyphen, so
# tr/A-J/0-9/ does the same replacement as "tr/ACEGIBDFHJ/0246813579/".

use Getopt::Std;

my %opts;
getopts('f:s:dhev', \%opts);

#----------------------------------------#
# main
#----------------------------------------#
my $filename = $opts{'f'} || '';
my $string   = $opts{'s'} || '';
my $encrypt  = $opts{'e'} || 0;
my $decrypt  = $opts{'d'} || 0;
my $verbose  = $opts{'v'} || 0;
my $help     = $opts{'h'} || 0;

if ( ($help) || ( (!$filename) && (!$string) ) ) {
	usage();
}

# default to encrypt
$encrypt = 1 if ( (!$encrypt) && (!$decrypt) );

# process a file
if ($filename) {
	if (! -f $filename) {
		print "file '$filename' doesn't exist or isn't a file\n";
		exit(1);
	}

	open(FP, "< $filename") || die "Unable to encrypt file '$filename': $!\n";
	while(<FP>) {
		chomp(my $line = $_);
		$line = encrypt($line) if ($encrypt);
		$line = decrypt($line) if ($decrypt);
		print "$line\n";
	}
	close(FP);
}

# process a string
if ($string) {
	chomp(my $line = $string);
	$line = encrypt($line) if ($encrypt);
	$line = decrypt($line) if ($decrypt);
	print "$line\n";
}

exit(0);

#----------------------------------------#
# subroutines
#----------------------------------------#
# encrypt the input string
sub encrypt {
	my $str = shift;

	$str =~ y/A-Za-z0-9.\-/g-vw-z0-9.\-A-PQ-Za-f/;

	return $str;
}

# decrypt the input string
sub decrypt {
	my $str = shift;

	$str =~ y/A-Za-z0-9.\-/g-vw-z0-9.\-A-PQ-Za-f/;

	return $str;
}

# usage
sub usage {
	print "usage: $0\n";
	print "\t-e : encrypt (default)\n";
	print "\t-d : decrypt\n";
	print "\t-s : string to convert\n";
	print "\t-f : filename to process\n";
	print "\t-h : help, this menu\n";
	exit(0);
}