class HTML::WhiteListSanitizer

def process_node(node, result, options)
  result << case node
    when HTML::Tag
      if node.closing == :close
        options[:parent].shift
      else
        options[:parent].unshift node.name
      end
      process_attributes_for node, options
      options[:tags].include?(node.name) ? node : nil
    else
      bad_tags.include?(options[:parent].first) ? nil : node.to_s.gsub(/</, "&lt;")
  end
end