indent.rb

def indent(input)
  @lexer.set_input StringIO.new(input)
  output = ""
  last_seek = 0
  seek = 0
  while token = @lexer.token
    # Check for newline
    if token.is_a? RubyToken::TkNL
      seek = token.seek
      # Take all characters that were from the previous line and add them
      # to the output. I'm not sure if eating the spaces at the start would
      # be proper in this case.
      output << input[last_seek..seek]
      indent_level = @lexer.indent
      # This check is because when RubyLex is complete, it returns a -1
      # indent.
      @indent_level = if indent_level > 0 then (SPACES * indent_level) else ('') end
      # Add the indent prefix.
      output << indent_level
      # Shift a character.
      last_seek = seek+1
    end
  end
  output
end

# To get indent level, you would pass the string to indent, and then access the attribute