class Sass::Script::Lexer

def _variable(rx)
  return unless scan(rx)
  [:const, Sass::Util.normalize_ident_escapes(@scanner[2])]
end

def after_interpolation?
  @prev && @prev.type == :end_interpolation
end

def char(pos = @scanner.pos)
  @scanner.string[pos, 1]
end

def color
  return unless @scanner.match?(REGULAR_EXPRESSIONS[:color])
  unless @scanner[0].length == 4 || @scanner[0].length == 5 ||
         @scanner[0].length == 7 || @scanner[0].length == 9
    return
  end
  script_color = Script::Value::Color.from_hex(scan(REGULAR_EXPRESSIONS[:color]))
  [:color, script_color]
end

def done?
  return if @next_tok
  whitespace unless after_interpolation? && !@interpolation_stack.empty?
  @scanner.eos? && @tok.nil?
end

def expected!(name)
  unpeek!
  Sass::SCSS::Parser.expected(@scanner, name, @line)
end

def id
  # Colors and ids are tough to tell apart, because they overlap but
  # neither is a superset of the other. "#xyz" is an id but not a color,
  # "#000" is a color but not an id, "#abc" is both, and "#0" is neither.
  # We need to handle all these cases correctly.
  #
  # To do so, we first try to parse something as an id. If this works and
  # the id is also a valid color, we return the color. Otherwise, we
  # return the id. If it didn't parse as an id, we then try to parse it as
  # a color. If *this* works, we return the color, and if it doesn't we
  # give up and throw an error.
  #
  # IDs in properties are used in the Basic User Interface Module
  # (http://www.w3.org/TR/css3-ui/).
  return unless scan(REGULAR_EXPRESSIONS[:id])
  if @scanner[0] =~ /^\#[0-9a-fA-F]+$/ &&
    (@scanner[0].length == 4 || @scanner[0].length == 5 ||
     @scanner[0].length == 7 || @scanner[0].length == 9)
    return [:color, Script::Value::Color.from_hex(@scanner[0])]
  end
  [:ident, Sass::Util.normalize_ident_escapes(@scanner[0])]
end

def ident
  return unless scan(REGULAR_EXPRESSIONS[:ident])
  [@scanner[2] ? :funcall : :ident, Sass::Util.normalize_ident_escapes(@scanner[1])]
end

def ident_op
  op = scan(REGULAR_EXPRESSIONS[:ident_op])
  return unless op
  [OPERATORS[op]]
end

def initialize(str, line, offset, options)
  @scanner = str.is_a?(StringScanner) ? str : Sass::Util::MultibyteStringScanner.new(str)
  @line = line
  @offset = offset
  @options = options
  @interpolation_stack = []
  @prev = nil
  @tok = nil
  @next_tok = nil
end

def line
  return @line unless @tok
  @tok.source_range.start_pos.line
end

def next
  @tok ||= read_token
  @tok, tok = nil, @tok
  @prev = tok
  tok
end

def next_char
  unpeek!
  scan(/./)
end

def number
  # Handling unary minus is complicated by the fact that whitespace is an
  # operator in SassScript. We want "1-2" to be parsed as "1 - 2", but we
  # want "1 -2" to be parsed as "1 (-2)". To accomplish this, we only
  # parse a unary minus as part of a number literal if there's whitespace
  # before and not after it. Cases like "(-2)" are handled by the unary
  # minus logic in the parser instead.
  if @scanner.peek(1) == '-'
    return if @scanner.pos == 0
    unary_minus_allowed =
      case @scanner.string[@scanner.pos - 1, 1]
      when /\s/; true
      when '/'; @scanner.pos != 1 && @scanner.string[@scanner.pos - 2, 1] == '*'
      else; false
      end
    return unless unary_minus_allowed
    return unless scan(REGULAR_EXPRESSIONS[:unary_minus_number])
    minus = true
  else
    return unless scan(REGULAR_EXPRESSIONS[:number])
    minus = false
  end
  value = (@scanner[1] ? @scanner[1].to_f : @scanner[2].to_i) * (minus ? -1 : 1)
  value *= 10**@scanner[3].to_i if @scanner[3]
  units = @scanner[4]
  units = Sass::Util::normalize_ident_escapes(units) if units
  script_number = Script::Value::Number.new(value, Array(units))
  [:number, script_number]
end

def offset
  return @offset unless @tok
  @tok.source_range.start_pos.offset
end

def op
  op = scan(REGULAR_EXPRESSIONS[:op])
  return unless op
  name = OPERATORS[op]
  @interpolation_stack << nil if name == :begin_interpolation
  [name]
end

def peek
  @tok ||= read_token
end

def range(start_pos, end_pos = source_position)
  Sass::Source::Range.new(start_pos, end_pos, @options[:filename], @options[:importer])
end

def raw(rx)
  val = scan(rx)
  return unless val
  [:raw, val]
end

def read_token
  if (tok = @next_tok)
    @next_tok = nil
    return tok
  end
  return if done?
  start_pos = source_position
  value = token
  return unless value
  type, val = value
  Token.new(type, val, range(start_pos), @scanner.pos - @scanner.matched_size)
end

def scan(re)
  str = @scanner.scan(re)
  return unless str
  c = str.count("\n")
  @line += c
  @offset = (c == 0 ? @offset + str.size : str.size - str.rindex("\n"))
  str
end

def selector
  start_pos = source_position
  return unless scan(REGULAR_EXPRESSIONS[:selector])
  if @scanner.peek(1) == '&'
    filename = @options[:filename]
    Sass::Util.sass_warn <<MESSAGE
G on line #{line}, column #{offset}#{" of #{filename}" if filename}:
s, "&&" means two copies of the parent selector. You probably want to use "and" instead.
E
  end
  script_selector = Script::Tree::Selector.new
  script_selector.source_range = range(start_pos)
  [:selector, script_selector]
end

def source_position
  Sass::Source::Position.new(@line, @offset)
end

def special_fun
  prefix = scan(/((-[\w-]+-)?(calc|element)|expression|progid:[a-z\.]*)\(/i)
  return unless prefix
  special_fun_body(1, prefix)
end

def special_fun_body(parens, prefix = nil)
  str = prefix || ''
  while (scanned = scan(/.*?([()]|\#\{)/m))
    str << scanned
    if scanned[-1] == ?(
      parens += 1
      next
    elsif scanned[-1] == ?)
      parens -= 1
      next unless parens == 0
    else
      raise "[BUG] Unreachable" unless @scanner[1] == '#{' # '
      str.slice!(-2..-1)
      @interpolation_stack << [:special_fun, parens]
      start_pos = Sass::Source::Position.new(@line, @offset - 2)
      @next_tok = Token.new(:string_interpolation, range(start_pos), @scanner.pos - 2)
    end
    return [:special_fun, Sass::Script::Value::String.new(str)]
  end
  scan(/.*/)
  expected!('")"')
end

def special_val
  return unless scan(/!#{W}important/i)
  [:string, Script::Value::String.new("!important")]
end

def str
  old_pos = @tok ? @tok.pos : @scanner.pos
  yield
  new_pos = @tok ? @tok.pos : @scanner.pos
  @scanner.string[old_pos...new_pos]
end

def string(re, open)
  line, offset = @line, @offset
  return unless scan(STRING_REGULAR_EXPRESSIONS[re][open])
  if @scanner[0] =~ /([^\\]|^)\n/
    filename = @options[:filename]
    Sass::Util.sass_warn <<MESSAGE
ATION WARNING on line #{line}, column #{offset}#{" of #{filename}" if filename}:
ped multiline strings are deprecated and will be removed in a future version of Sass.
lude a newline in a string, use "\\a" or "\\a " as in CSS.
E
  end
  if @scanner[2] == '#{' # '
    @interpolation_stack << [:string, re]
    start_pos = Sass::Source::Position.new(@line, @offset - 2)
    @next_tok = Token.new(:string_interpolation, range(start_pos), @scanner.pos - 2)
  end
  str =
    if re == :uri
      url = "#{'url(' unless open}#{@scanner[1]}#{')' unless @scanner[2] == '#{'}"
      Script::Value::String.new(url)
    else
      Script::Value::String.new(Sass::Script::Value::String.value(@scanner[1]), :string)
    end
  [:string, str]
end

def string_re(open, close)
  /#{open}((?:\\.|\#(?!\{)|[^#{close}\\#])*)(#{close}|#\{)/m
end

def token
  if after_interpolation?
    interp_type, interp_value = @interpolation_stack.pop
    if interp_type == :special_fun
      return special_fun_body(interp_value)
    elsif interp_type.nil?
      if @scanner.string[@scanner.pos - 1] == '}' && scan(REGULAR_EXPRESSIONS[:ident])
        return [@scanner[2] ? :funcall : :ident, Sass::Util.normalize_ident_escapes(@scanner[1], start: false)]
      end
    else
      raise "[BUG]: Unknown interp_type #{interp_type}" unless interp_type == :string
      return string(interp_value, true)
    end
  end
  variable || string(:double, false) || string(:single, false) || number || id || color ||
    selector || string(:uri, false) || raw(UNICODERANGE) || special_fun || special_val ||
    ident_op || ident || op
end

def try
  old_pos = @scanner.pos
  old_line = @line
  old_offset = @offset
  old_interpolation_stack = @interpolation_stack.dup
  old_prev = @prev
  old_tok = @tok
  old_next_tok = @next_tok
  result = yield
  return result if result
  @scanner.pos = old_pos
  @line = old_line
  @offset = old_offset
  @interpolation_stack = old_interpolation_stack
  @prev = old_prev
  @tok = old_tok
  @next_tok = old_next_tok
  nil
end

def unpeek!
  raise "[BUG] Can't unpeek before a queued token!" if @next_tok
  return unless @tok
  @scanner.pos = @tok.pos
  @line = @tok.source_range.start_pos.line
  @offset = @tok.source_range.start_pos.offset
end

def variable
  _variable(REGULAR_EXPRESSIONS[:variable])
end

def whitespace
  nil while scan(REGULAR_EXPRESSIONS[:whitespace]) ||
    scan(REGULAR_EXPRESSIONS[:comment]) ||
    scan(REGULAR_EXPRESSIONS[:single_line_comment])
end

def whitespace?(tok = @tok)
  if tok
    @scanner.string[0...tok.pos] =~ /\s\Z/
  else
    @scanner.string[@scanner.pos, 1] =~ /^\s/ ||
      @scanner.string[@scanner.pos - 1, 1] =~ /\s\Z/
  end
end