global

def page_classes(*additional)
  path = request.path_info
  path << "index.html" if path.match(%r{/$})
  path.gsub!(%r{^/}, '')
  
  classes = []
  parts = path.split('.')[0].split('/')
  parts.each_with_index { |path, i| classes << parts.first(i+1).join('_') }

  classes << "index" if classes.empty?
  classes += additional unless additional.empty?
  classes.join(' ')
end