#! /usr/bin/perl -w

use strict;
use Data::Dumper;

# this is ugly, and overkill
sub min
{
    my $x = shift;
    return $x if scalar @_ == 0;
    my $y = &min(@_);
    return $x > $y ? $y : $x;
}

sub perfect_shuffle
{
    my ($a, $b) = @_;

    my @res   = ();
    my $n_els = @$a;

    if(@$a != @$b) {
        warn "perfect_shuffle: lists must have equal length!\n";
        $n_els = &min(scalar @$a, scalar @$b);
    }

    while($n_els--) {
        push @res, shift @$a, shift @$b;
    }

    return \@res;
}

sub build_deck
{
    my $deck = ();

    for my $suit (('c', 'd', 'h', 's')) {
        for my $card ((2..9, 'T', 'J', 'Q', 'K', 'A')) {
            push @$deck, [$suit, $card];
        }
    }

    return $deck;
}

sub show_deck
{
    my ($deck) = @_;

    # print suits, then values
    # primo candidate for extraction into sub
    {
        local $\ = ' ';
        for (@$deck) { print $_->[0] }
    }
    print "\n";

    {
        local $\ = ' ';
        for (@$deck) { print $_->[1] }
    }
    print "\n";
}

sub split_deck
{
    my ($deck) = @_;

    my $mid = @$deck / 2;

    my @left  = @$deck[0..($mid-1)];
    my @right = @$deck[$mid..@$deck-1];

    return (\@left, \@right);
}

my $deck    = &build_deck();

for my $shuffle (1..10) {
    print "shuffle $shuffle:\n";
    my ($l, $r) = &split_deck($deck);
    $deck = &perfect_shuffle($l, $r);
    &show_deck($deck);
}
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