use v6.d.PREVIEW;

class Ultramarine::Model::DirScanner {
    has IO $.root is required;
    submethod BUILD(IO() :$!root!) {}

    class EndOfScan {}

    method scan(--> Supply) {
        my $ret = Supplier::Preserving.new;

        my sub inner-scan(IO() $path) {
            my @todo = $path;
            while @todo {
                my $next = @todo.pop;
                $ret.emit($next);
                next unless $next ~~ :d & :r & :x;
                $next.watch().tap({ inner-scan($^event.path) });
                for $next.dir(:CWD($next.CWD)) -> $child {
                    @todo.push($child);
                }
                CATCH {
                    when X::IO::Dir { }
                }
            }
        }

        (start {
            inner-scan(IO::Path.new('.',:CWD($.root)));
            $ret.emit(EndOfScan);
        }).then(-> $p { $ret.quit($p.cause) if $p.status ~~ Broken });

        CATCH { $ret.quit($_) };
        return $ret.Supply;
    }
}