use v6;




my constant @common-words = <the was who not did with have does and one that>;

sub infix:<XOR>(@cipher, @password) {
    @cipher Z+^ flat (@password xx *);
}

sub as-code(Str $w) {
    my @x = $w.comb.map(*.ord)
}

sub as-word(*@s) {
    @s.map(*.chr).join
}

sub guess-password(Str $w, @cipher) {
    my @word = as-code $w;

    my @chunks = @cipher.rotor((@word.elems) => -(@word.elems - 1));
    my %tries;
    my $offset = 0;

    for @chunks -> @chunk {
        
        my @password  = @chunk[^3] XOR @word;
        
        my $password  = as-word @password;
        
        next unless $password ~~ /^^ <[a..z]> ** 3 $$/ ;
        my $decrypted = as-word @cipher[$offset .. *] XOR @password;
        
        my $count =  [+] do for @common-words.grep({$_ !~~ $w}) -> $word {
            elems $decrypted ~~ m:g:i/$word/
        }

        %tries{$password} += $count if $count > 0;

        return %tries if $count > @common-words.elems;

        $offset   += 1;
        $offset div= $w.chars;
    }
    %tries;
}

sub MAIN(Bool :$verbose = False,
        :$file = $*SPEC.catdir($*PROGRAM-NAME.IO.dirname, 'cipher.txt'),
        :$word = @common-words[0],
        :$pass is copy,
        Bool :$test = False) {
    return TEST if $test;
    die "'$file' is missing" unless $file.IO.e ;
    my @cipher     = map *.Int, split /<[,]>/ , slurp $file;

    unless $pass {
        my %variants = guess-password $word, @cipher;
        $pass  = %variants.pairs.max(*.value).key;
        say "The password is more likely to be '$pass'. " if $verbose;
    }

    my $decrypted =  as-word @cipher XOR as-code($pass);
    
    say "The message: {$decrypted.perl}" if $verbose;
    say [+] as-code $decrypted;
    say "Done in {now - BEGIN now}" if $verbose;
}

sub TEST {
    use Test;
    is as-code("abc"), [97,98,99], "as-code works";
    is as-word(100,101,102), "def", "as-word works";
    is as-word([79,59,12] XOR [103,111,100]), "(Th", "XOR works";
    done;
}

# vim: expandtab shiftwidth=4 ft=perl6
See Also
