module Nanaimo::Unicode

def quotify_string(string)
  string.gsub(QUOTE_REGEXP, QUOTE_MAP)
end

def unquotify_string(string)
  formatted_string = ::String.new
  extracted_string = string
  string_length = string.size
  index = 0
  while index < string_length
    if escape_index = extracted_string.index('\\', index)
      formatted_string << extracted_string[index...escape_index] unless index == escape_index
      index = escape_index + 1
      next_char = extracted_string[index]
      if ESCAPE_PREFIXES.include?(next_char)
        index += 1
        if unquoted = UNQUOTE_MAP[next_char]
          formatted_string << unquoted
        elsif next_char == 'U'
          length = 4
          unicode_numbers = extracted_string[index, length]
          unless unicode_numbers =~ /\A\h{4}\z/
            raise InvalidEscapeSequenceError, "Unicode '\\U' escape sequence terminated without 4 following hex characters"
          end
          index += length
          formatted_string << [unicode_numbers.to_i(16)].pack('U')
        elsif OCTAL_DIGITS.include?(next_char) # https://twitter.com/Catfish_Man/status/658014170055507968
          octal_string = extracted_string[index - 1, 3]
          if octal_string =~ /\A[0-7]{3}\z/
            index += 2
            code_point = octal_string.to_i(8)
            unless code_point <= 0x80 || converted = NEXT_STEP_MAPPING[code_point]
              raise InvalidEscapeSequenceError, "Invalid octal escape sequence #{octal_string}"
            end
            formatted_string << [converted].pack('U')
          else
            formatted_string << next_char
          end
        else
          raise UnsupportedEscapeSequenceError, "Failed to handle #{next_char} which is in the list of possible escapes"
        end
      else
        index += 1
        formatted_string << next_char
      end
    else
      formatted_string << extracted_string[index..-1]
      index = string_length
    end
  end
  formatted_string
end

def xml_escape_string(string)
  string.to_s.gsub(XML_STRING_ESCAPE_REGEXP, XML_STRING_ESCAPES)
end