class Gem::RequestSet::Lockfile::Tokenizer

def tokenize input
  s = StringScanner.new input
  until s.eos? do
    pos = s.pos
    pos = s.pos if leading_whitespace = s.scan(/ +/)
    if s.scan(/[<|=>]{7}/) then
      message = "your #{@filename} contains merge conflict markers"
      column, line = token_pos pos
      raise Gem::RequestSet::Lockfile::ParseError.new message, column, line, @filename
    end
    @tokens <<
      case
      when s.scan(/\r?\n/) then
        token = Token.new(:newline, nil, *token_pos(pos))
        @line_pos = s.pos
        @line += 1
        token
      when s.scan(/[A-Z]+/) then
        if leading_whitespace then
          text = s.matched
          text += s.scan(/[^\s)]*/).to_s # in case of no match
          Token.new(:text, text, *token_pos(pos))
        else
          Token.new(:section, s.matched, *token_pos(pos))
        end
      when s.scan(/([a-z]+):\s/) then
        s.pos -= 1 # rewind for possible newline
        Token.new(:entry, s[1], *token_pos(pos))
      when s.scan(/\(/) then
        Token.new(:l_paren, nil, *token_pos(pos))
      when s.scan(/\)/) then
        Token.new(:r_paren, nil, *token_pos(pos))
      when s.scan(/<=|>=|=|~>|<|>|!=/) then
        Token.new(:requirement, s.matched, *token_pos(pos))
      when s.scan(/,/) then
        Token.new(:comma, nil, *token_pos(pos))
      when s.scan(/!/) then
        Token.new(:bang, nil, *token_pos(pos))
      when s.scan(/[^\s),!]*/) then
        Token.new(:text, s.matched, *token_pos(pos))
      else
        raise "BUG: can't create token for: #{s.string[s.pos..-1].inspect}"
      end
  end
  @tokens
end