use warnings;
use feature 'state';
use strict;
no strict 'refs';

use Data::Dumper;

my $MAX_BINARY = 4;

my @CANONICALS = qw(O S P N);

my %foo = (
    composer => 'S',
    subgraphs => [
        { composer => 'O' },
        { composer => 'P',
            subgraphs => [
                { composer => 'O' },
                { composer => 'O' },
            ]
        },
        { composer => 'N',
            subgraphs => [
                { composer => 'O' },
                { composer => 'O' },
                { composer => 'P',
                    subgraphs => [
                        { composer => 'O' },
                        { composer => 'O' },
                        { composer => 'O' },
                        { composer => 'O' },
                    ]
                },
                { composer => 'O' }
            ]
        }
    ]
);
# my $dot = to_dot(%foo);
my $dot = to_dot(%{gen(2)});
$dot =~ s/^/	/gm;
print "strict digraph {\nrankdir=BT;\n$dot\n}";

sub gen
{
    my $n = shift;
    return { composer => 'O' } if $n == 0;
    my $rand = int(rand(4));
    return { composer => 'O' } if $rand == 0;
    $n--;
    my $composer;
    my $num_subgraphs;
    if ($rand == 1) { $composer = 'S'; $num_subgraphs = int(rand(4))+1; }
    if ($rand == 2) { $composer = 'P'; $num_subgraphs = int(rand(4))+1; }
    if ($rand == 3) { $composer = 'N'; $num_subgraphs = 4; }
    my @subgraphs;
    for (my $i = 0; $i < $num_subgraphs; $i++)
    {
        push @subgraphs, gen($n);
    }
    return { composer => $composer, subgraphs => [ @subgraphs ] };
}

sub to_dot
{
    state $nodes = 0;
    my %graph = @_;
    return $nodes++ if ($graph{composer} eq 'O');
    my $inner = &{$graph{composer}}(@{$graph{subgraphs}});
    $inner =~ s/^/	/gm;
    return "subgraph { \n$inner\n}";
}

sub S
{
    my @rendered = map { to_dot(%$_) } @_;
    return join "\n->\n", @rendered;
}
sub P
{
    my @rendered = map { to_dot(%$_) } @_;
    return join "\n;\n", @rendered;
}
sub N
{
    my @rendered = map { to_dot(%$_) } @_;
    my $composed = "";
    $composed .= "{ $rendered[0] $rendered[1] }\n->\n$rendered[2]";
    $composed .= "\n;\n";
    $composed .= "$rendered[1]\n->\n$rendered[3]";
    return $composed;
}