module Erubis::Converter

def detect_spaces_at_bol(text, is_bol)
  lspace = nil
  if text.empty?
    lspace = "" if is_bol
  elsif text[-1] == ?\n
    lspace = ""
  else
    rindex = text.rindex(?\n)
    if rindex
      s = text[rindex+1..-1]
      if s =~ /\A[ \t]*\z/
        lspace = s
        #text = text[0..rindex]
        text[rindex+1..-1] = ''
      end
    else
      if is_bol && text =~ /\A[ \t]*\z/
        #lspace = text
        #text = nil
        lspace = text.dup
        text[0..-1] = ''
      end
    end
  end
  return lspace
end