use strict;
use warnings;
use utf8;

our $AUTHOR  = "cpan:potatogim";
our $VERSION = "0.1";

package My::Generator;

use Generator::Object;

our %tree = (
    'dir1'      => [ 'dira', 'dirb', 'dirc' ],
    'dir1/dirc' => [ 'dird', 'dire', 'dirf' ],
    'dir2'      => [ 'dirg', 'dirh' ],
    'dir2/dirg' => [ 'diri' ],
);

sub scandir
{
    my $self = shift;
    my %args = @_;

    return generator
    {
        my $path = $args{path};

        foreach my $entry (@{$tree{$path}})
        {
            $_->yield($entry);
        }
    };
}

sub walk
{
    my $self = shift;
    my %args = @_;

    return generator
    {
        my $gen     = $_;
        my $top     = $args{top};
        my $topdown = $args{topdown};
        my $follow  = $args{followlinks};
        my $onerror = $args{onerror};

        my @dirs    = ();
        my @nondirs = ();

        my $direntry = $self->scandir(path => $top);

        while (my $entry = $direntry->next)
        {
            push(@dirs, $entry);
        }

#        printf "TOP     : %s\n", $top;
#        printf "TOPDOWN : %s\n", $topdown;
#        printf "FOLLOW  : %s\n", $follow;
#        printf "DIRS    : %s\n", join(', ', @dirs);

        if ($topdown)
        {
            $gen->yield($top, \@dirs, \@nondirs);
        }

        foreach my $dir (@dirs)
        {
            my $new_top = join('/', $top, $dir);

            my $c_gen = $self->walk(
                top         => $new_top,
                topdown     => $topdown,
                followlinks => $follow,
                onerror     => $onerror);

            while (my ($c_top, $c_dirs, $c_nondirs) = $c_gen->next)
            {
                $gen->yield($c_top, $c_dirs, $c_nondirs);
            }
        }

        if (!$topdown)
        {
            $gen->yield($top, \@dirs, \@nondirs);
        }
    };
}

sub new
{
    bless {}, shift;
}

package main;

my $obj = My::Generator->new();

print "NON-TOPDOWN\n";

my $gen = $obj->walk(top => 'dir1', topdown => 0, followlinks => 1, onerror => undef);

while (my ($top, $dirs, $nondirs) = $gen->next)
{
    printf "\nTOP  : %s\n", $top // 'undef';
    printf "DIRS : %s\n", defined($dirs) ? join(', ', @{$dirs}) : 'undef';
}

print "TOPDOWN\n";

$gen = $obj->walk(top => 'dir1', topdown => 1, followlinks => 1, onerror => undef);

while (my ($top, $dirs, $nondirs) = $gen->next)
{
    printf "\nTOP  : %s\n", $top // 'undef';
    printf "DIRS : %s\n", defined($dirs) ? join(', ', @{$dirs}) : 'undef';
}