class Syntax::CSS21

def macro(name, regex=nil)
  regex ? @macros[name] = regex : @macros[name].source
end

def setup
  @selector = true
  @macros = {}
  @tokens = {}
  # http://www.w3.org/TR/CSS21/syndata.html
  macro(:h, /([0-9a-fA-F])/ ) # uppercase A-Z added?
  macro(:nonascii, /([^\000-\177])/ )
  macro(:nl, /(\n|\r\n|\r|\f)/ )
  macro(:unicode, /(\\#{m(:h)}{1,6}(\r\n|[ \t\r\n\f])?)/ )
  macro(:escape, /(#{m(:unicode)}|\\[^\r\n\f0-9a-f])/ )
  macro(:nmstart, /([_a-z]|#{m(:nonascii)}|#{m(:escape)})/ )
  macro(:nmchar, /([_a-z0-9-]|#{m(:nonascii)}|#{m(:escape)})/ )
  macro(:string1, /(\"([^\n\r\f\\\"]|\\#{m(:nl)}|#{m(:escape)})*\")/ )
  macro(:string2, /(\'([^\n\r\f\\']|\\#{m(:nl)}|#{m(:escape)})*\')/ )
  macro(:invalid1, /(\"([^\n\r\f\\\"]|\\#{m(:nl)}|#{m(:escape)})*)/ )
  macro(:invalid2, /(\'([^\n\r\f\\']|\\#{m(:nl)}|#{m(:escape)})*)/ )
  macro(:comment, /(\/\*[^*]*\*+([^\/*][^*]*\*+)*\/)/ )
  macro(:ident, /(-?#{m(:nmstart)}#{m(:nmchar)}*)/ )
  macro(:name, /(#{m(:nmchar)}+)/ )
  macro(:num, /([0-9]+|[0-9]*\.[0-9]+)/ )
  macro(:string, /(#{m(:string1)}|#{m(:string2)})/ )
  macro(:invalid, /(#{m(:invalid1)}|#{m(:invalid2)})/ )
  macro(:s, /([ \t\r\n\f]+)/ )
  macro(:w, /(#{m(:s)}?)/ )
  macro(:A, /(a|\\0{0,4}(41|61)(\r\n|[ \t\r\n\f])?)/ )
  macro(:C, /(c|\\0{0,4}(43|63)(\r\n|[ \t\r\n\f])?)/ )
  macro(:D, /(d|\\0{0,4}(44|64)(\r\n|[ \t\r\n\f])?)/ )
  macro(:E, /(e|\\0{0,4}(45|65)(\r\n|[ \t\r\n\f])?)/ )
  macro(:G, /(g|\\0{0,4}(47|67)(\r\n|[ \t\r\n\f])?|\\g)/ )
  macro(:H, /(h|\\0{0,4}(48|68)(\r\n|[ \t\r\n\f])?|\\h)/ )
  macro(:I, /(i|\\0{0,4}(49|69)(\r\n|[ \t\r\n\f])?|\\i)/ )
  macro(:K, /(k|\\0{0,4}(4b|6b)(\r\n|[ \t\r\n\f])?|\\k)/ )
  macro(:M, /(m|\\0{0,4}(4d|6d)(\r\n|[ \t\r\n\f])?|\\m)/ )
  macro(:N, /(n|\\0{0,4}(4e|6e)(\r\n|[ \t\r\n\f])?|\\n)/ )
  macro(:O, /(o|\\0{0,4}(51|71)(\r\n|[ \t\r\n\f])?|\\o)/ )
  macro(:P, /(p|\\0{0,4}(50|70)(\r\n|[ \t\r\n\f])?|\\p)/ )
  macro(:R, /(r|\\0{0,4}(52|72)(\r\n|[ \t\r\n\f])?|\\r)/ )
  macro(:S, /(s|\\0{0,4}(53|73)(\r\n|[ \t\r\n\f])?|\\s)/ )
  macro(:T, /(t|\\0{0,4}(54|74)(\r\n|[ \t\r\n\f])?|\\t)/ )
  macro(:X, /(x|\\0{0,4}(58|78)(\r\n|[ \t\r\n\f])?|\\x)/ )
  macro(:Z, /(z|\\0{0,4}(5a|7a)(\r\n|[ \t\r\n\f])?|\\z)/ )
  token(:COMMENT, /#{m(:comment)}/)
  token(:HASH, /\#/)
  token(:IDENT, /#{m(:ident)}/)
  token(:LBRACE, /#{m(:w)}\{/)
  token(:RBRACE, /#{m(:w)}\}/)
  token(:S, /#{m(:s)}/)
  token(:FUNCTION, /#{m(:ident)}(?=\()/)
  token(:PLUS, /#{m(:w)}\+/)
  token(:GREATER, /#{m(:w)}>/)
  token(:COMMA, /#{m(:w)},/)
  token(:CDO, /<!--/)
  token(:CDC, /-->/)
  token(:INCLUDES, /~=/)
  token(:DASHMATCH, /\|=/)
  token(:STRING, /#{m(:string)}/)
  token(:INVALID, /#{m(:invalid)}/)
  token(:IMPORT_SYM, /@#{m(:I)}#{m(:M)}#{m(:P)}#{m(:O)}#{m(:R)}#{m(:T)}/)
  token(:PAGE_SYM, /@#{m(:P)}#{m(:A)}#{m(:G)}#{m(:E)}/)
  token(:MEDIA_SYM, /@#{m(:M)}#{m(:E)}#{m(:D)}#{m(:I)}#{m(:A)}/)
  token(:CHARSET_SYM, /@#{m(:C)}#{m(:H)}#{m(:A)}#{m(:R)}#{m(:S)}#{m(:E)}#{m(:T)}/)
  token(:IMPORTANT_SYM, /!(#{m(:w)}|#{m(:comment)})*#{m(:I)}#{m(:M)}#{m(:P)}#{m(:O)}#{m(:R)}#{m(:T)}#{m(:A)}#{m(:N)}#{m(:T)}/)
  token(:EMS, /#{m(:num)}#{m(:E)}#{m(:M)}/)
  token(:EXS, /#{m(:num)}#{m(:E)}#{m(:X)}/)
  token :LENGTH do |patterns|
    patterns << /#{m(:num)}#{m(:P)}#{m(:X)}/
    patterns << /#{m(:num)}#{m(:C)}#{m(:M)}/
    patterns << /#{m(:num)}#{m(:M)}#{m(:M)}/
    patterns << /#{m(:num)}#{m(:I)}#{m(:N)}/
    patterns << /#{m(:num)}#{m(:P)}#{m(:T)}/
    patterns << /#{m(:num)}#{m(:P)}#{m(:C)}/
  end
  token :ANGLE do |patterns|
    patterns << /#{m(:num)}#{m(:D)}#{m(:E)}#{m(:G)}/
    patterns << /#{m(:num)}#{m(:R)}#{m(:A)}#{m(:D)}/
    patterns << /#{m(:num)}#{m(:G)}#{m(:R)}#{m(:A)}#{m(:D)}/
  end
  token :TIME do |patterns|
    patterns << /#{m(:num)}#{m(:M)}#{m(:S)}/
    patterns << /#{m(:num)}#{m(:S)}/
  end
  token :FREQ do |patterns|
    patterns << /#{m(:num)}#{m(:H)}#{m(:Z)}/
    patterns << /#{m(:num)}#{m(:K)}#{m(:H)}#{m(:Z)}/
  end
  token :URI do |patterns|
    patterns << /url\(#{m(:w)}#{m(:string)}#{m(:w)}\)/
    patterns << /url\(#{m(:w)}([!$%&*-~]|#{m(:nonascii)}|#{m(:escape)})*#{m(:w)}\)/
  end
  token(:DIMENSION, /#{m(:num)}#{m(:ident)}/)
  token(:PERCENTAGE, /#{m(:num)}%/)
  token(:HEXNUM, /##{m(:h)}{2,6}/)
  token(:NUMBER, /#{m(:num)}/)
end

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

def token(name, pattern=nil, &block)
  raise ArgumentError, "name required" unless name
  patterns = []
  patterns << pattern if pattern
  yield(patterns) if block_given?
  if patterns.empty?
    raise ArgumentError, "at least one pattern required"
  end
  patterns.collect! do |pattern|
    source = pattern.source
    source = "\\A#{source}"
    Regexp.new(source, Regexp::IGNORECASE + Regexp::MULTILINE)
  end
  @tokens[name] = Regexp.union(*patterns)
end