#!perl

sub command { NEXT }

sub hook_checkout {
    my ($class, $cart, $user, $transaction_id) = @_;

    # Hack42 for some reason used the dutch word in their revbank1 hack.
    my $filename = -e("revbank.voorraad")
        ? "revbank.voorraad"
        : "revbank.stock";

    my @items = $cart->select_items('product_id') or return;

    my %stock = do {
        my $in;
        open($in, '<', $filename)
        ? map { split " ", $_, 2 } readline $in
        : ()
    };

    $stock{ $_->{product_id} }-- for @items;

    open my $out, '>', "$filename.$$" or warn "$filename.$$: $!";
    printf {$out} "%-16s %+9d\n", $_, $stock{$_} for sort keys %stock;
    close $out or die "$filename.$$: $!";
    rename "$filename.$$", $filename or die $!;
}