class Gem::RequestSet::Lockfile::Tokenizer

def self.from_file file
  new File.read(file), file
end

def empty?
  @tokens.empty?
end

def initialize input, filename = nil, line = 0, pos = 0
  @line     = line
  @line_pos = pos
  @tokens   = []
  @filename = filename
  tokenize input
end

def make_parser set, platforms
  Gem::RequestSet::Lockfile::Parser.new self, set, platforms, @filename
end

def next_token
  @tokens.shift
end

def peek
  @tokens.first || EOF
end

def skip type
  @tokens.shift while not @tokens.empty? and peek.type == type
end

def to_a
  @tokens.map { |token| [token.type, token.value, token.column, token.line] }
end

def token_pos byte_offset # :nodoc:
  [byte_offset - @line_pos, @line]
end

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

def unshift token
  @tokens.unshift token
end