class Syntax::CSS21

def step
  case
  # scanning selectors only
  when @selector && scan(@tokens[:LBRACE])
    @selector = false
    start_group :normal, matched
  when @selector && scan(@tokens[:IMPORT_SYM])
    start_group :import, matched
  when @selector && scan(@tokens[:PAGE_SYM])
    start_group :page, matched
  when @selector && scan(@tokens[:MEDIA_SYM])
    start_group :media, matched
  when @selector && scan(@tokens[:CHARSET_SYM])
    start_group :charset, matched
  when @selector && scan(@tokens[:HASH])
    start_group :normal, matched
  when @selector && scan(@tokens[:URI])
    start_group :uri, matched
  when @selector && scan(@tokens[:IDENT])
    if MY_TAGS.include?( matched )
      start_group :tag, matched
    else
      start_group :ident, matched
    end
  # scanning declarations only
  when !@selector && scan(@tokens[:RBRACE])
    @selector = true
    start_group :normal, matched
  when !@selector && scan(@tokens[:FUNCTION])
    start_group :function, matched
  when !@selector && scan(@tokens[:EMS])
    start_group :ems, matched
  when !@selector && scan(@tokens[:EXS])
    start_group :exs, matched
  when !@selector && scan(@tokens[:LENGTH])
    start_group :length, matched
  when !@selector && scan(@tokens[:ANGLE])
    start_group :angle, matched
  when !@selector && scan(@tokens[:TIME])
    start_group :time, matched
  when !@selector && scan(@tokens[:FREQ])
    start_group :freq, matched
  when !@selector && scan(@tokens[:PERCENTAGE])
    start_group :percentage, matched
  when !@selector && scan(@tokens[:DIMENSION])
    start_group :dimension, matched
  when !@selector && scan(@tokens[:NUMBER])
    start_group :number, matched
  when !@selector && scan(@tokens[:HEXNUM])
    start_group :number, matched
  when !@selector && scan(@tokens[:IMPORTANT_SYM])
    start_group :important, matched
  when !@selector && scan(@tokens[:IDENT])
    if CSS21_PROPERTIES.include?( matched ) # are they disjoint?
      start_group :property, matched
    elsif CSS21_KEYWORDS.include?( matched )
      start_group :keyword, matched
    else
      start_group :ident, matched
    end
  # scanning both
  when scan(@tokens[:S])
    start_group :normal, matched
  when scan(@tokens[:COMMENT])
    start_group :comment, matched
  when scan(@tokens[:STRING])
    start_group :string, matched
  when scan(@tokens[:CDO])
    start_group :cdo, matched
  when scan(@tokens[:CDC])
    start_group :cdc, matched
  when scan(@tokens[:INVALID])
    start_group :invalid, matched
  else
    start_group :normal, scan(/./x)
  end
end