class TreeWatch
{
    has %.taps;
    has IO $.root;
    has $.supplier;

    method new( IO() $root )
    {
        my $ich = self.bless( :$root, supplier => Supplier.new );
        $ich.taps{ $root } = 
        $ich.scan( $root );
        return $ich;
    }

    method retap( IO $path, &block )
    {
        my $old = %.taps{$path};
        %.taps{$path} = $path.watch.tap( &block );
        $old.close if $old;
    }

    method scan( $dir )
    {
        self.retap: $dir,
        {
            say "dir $dir tap fired";
            self.scan( $dir );
            $.supplier.emit( $_ );
        };

        for dir( $dir )
        {
            if .IO.d
            {
                self.scan( $_ );
            }
            else
            {
                self.retap( $_, { $.supplier.emit( $_ ) } );
            }
        }
    }

    method Supply()
    {
        $.supplier.Supply;
    }
}