#!/usr/bin/perl
# usage: 
# vigenere.pl -e key inputfile   (for encryption of inputfile with key)
# vigenere.pl -d key inputfile   (for decryption)

($mode, $key, $infile, $optQ) = @ARGV;
$quiet = ($optQ eq "-q");

print "Vigenere cipher by nicZ\n" unless ($quiet);

&checkForFile($infile);
$text = &stripText(`cat $infile`);    
@inputText = split('', $text);

@key = split('', $key);
@keyCodes = &encode(@key);
$keyLen = scalar(@key);

print "Key is $key\n"  unless ($quiet);
print "\nPlaintext is\n" unless ($quiet);

&doEncryption() if ($mode eq "-e");
&doDecryption() if ($mode eq "-d");

sub doEncryption {
    &blockPrint(@inputText) unless ($quiet);
    
    @cipherText = &encrypt(@inputText);
    print "\nCiphertext is\n" unless ($quiet);
    &blockPrint(@cipherText);
}

sub doDecryption {
    @plainText = &decrypt(@inputText);
    &blockPrint(@plainText);    
}

sub encrypt {
    return &crypt(1, @_);
}

sub decrypt {
    return &crypt(-1, @_);
}

sub stripText{
    while ($text = shift) {
	chomp $text;
	$stext .= $text;
    }
    $stext =~ s/( |\.|,|\n)//g;
    return lc($stext);
}

sub crypt {
    my $ende = shift;
    my @cypher = ();
    my @codes = &encode(@_);
    my $lim = scalar(@_);
    foreach $i (0 .. $lim-1) {
	push @cypher, ((shift(@codes) + $ende*$keyCodes[$i % $keyLen]) % 26);
    }
    return &decode(@cypher);
}

sub encode {
    return map(ord($_) - ord('a'), @_);
}

sub decode {
    return map(chr($_ + ord('a')), @_);
}

sub blockPrint {
    my $i = 0;
    while ($char = shift) {
	print " "  if ($i %  5 == 0 && $i > 0);
	print "\n" if ($i % 40 == 0 && $i > 0);
	print uc($char);
	$i++;
    }
    print "\n";
}

sub checkForFile {
    my ($fn) = @_;
    die "Error : file $fn does not exist!\n" unless (-e $fn);
    warn "Warning : file $fn has zero size!\n" if (-z $fn);
}