sub format {
      my $self = shift;
      my $source = shift;

      $previndent = 0;
      $prevtype = 0;
      @indentstack = (0);
      @rulestack = (0);	# prime the pump with the null ruleset

      html();

      foreach ( split("\n", $source) ) {
          ($indent, $type, $line, $info) = classify_line($_);
          $indent = $previndent if $type == $BLANK;
	
          if ( not maybe_new_scope() ) {
              while ( maybe_exit_scope() ) {
              }
              maybe_new_scope();
          }

          maybe_emit_markup();
          emit($self->markup($line));
          $previndent = $indent;
          $prevtype = $type;
      }

      exit_scopes();

      my $html = html();

      return cleanup_html($html);
}