class REXML::Parsers::BaseParser

def parse_id_invalid_details(accept_external_id:,
                             accept_public_id:)
  public = /\A\s*PUBLIC/um
  system = /\A\s*SYSTEM/um
  if (accept_external_id or accept_public_id) and @source.match?(/#{public}/um)
    if @source.match?(/#{public}(?:\s+[^'"]|\s*[\[>])/um)
      return "public ID literal is missing"
    end
    unless @source.match?(/#{public}\s+#{PUBIDLITERAL}/um)
      return "invalid public ID literal"
    end
    if accept_public_id
      if @source.match?(/#{public}\s+#{PUBIDLITERAL}\s+[^'"]/um)
        return "system ID literal is missing"
      end
      unless @source.match?(/#{public}\s+#{PUBIDLITERAL}\s+#{SYSTEMLITERAL}/um)
        return "invalid system literal"
      end
      "garbage after system literal"
    else
      "garbage after public ID literal"
    end
  elsif accept_external_id and @source.match?(/#{system}/um)
    if @source.match?(/#{system}(?:\s+[^'"]|\s*[\[>])/um)
      return "system literal is missing"
    end
    unless @source.match?(/#{system}\s+#{SYSTEMLITERAL}/um)
      return "invalid system literal"
    end
    "garbage after system literal"
  else
    unless @source.match?(/\A\s*(?:PUBLIC|SYSTEM)\s/um)
      return "invalid ID type"
    end
    "ID type is missing"
  end
end