gistfile1.pl

sub vine_commit {
    my ( $vines, $rev, $parents ) = @_;

    my @graph_chars = map vine_character( $_, $rev ), @{$vines};

    my $is_tip = !grep { $_ eq 'C' } @graph_chars;

    @graph_chars = insert_branch_tip_into_rightmost_empty_even_vine_slot( $rev, $vines, @graph_chars ) if $is_tip;

    my $graph_line = join '', @graph_chars;

    remove_trailing_blanks( $vines );

    # tree root
    $graph_line =~ tr/C/r/ if !@$parents;

    return $graph_line;
}

sub insert_branch_tip_into_rightmost_empty_even_vine_slot {
    my ( $rev, $vines, @graph_chars ) = @_;

    my @even_slots = grep !( $_ % 2 ), 0 .. $#graph_chars;
    my @free_slots = grep $graph_chars[$_] eq ' ', @even_slots;

    my $right_most_slot = 0;
    $right_most_slot = $even_slots[-1] + 2 if @even_slots;
    $right_most_slot = $free_slots[-1] if @free_slots;

    $vines->[$right_most_slot] = $rev;
    $graph_chars[$right_most_slot] = 't';

    $_ //= ' ' for @graph_chars;

    return @graph_chars;
}