convert digitis into words

main.dart

library digits_to_words;

class DigitsToWords {
  static const List<String> _units = [
    "", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"
  ];

  static const List<String> _tens = [
    "", "", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"
  ];

  static const List<String> _teens = [
    "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen",
    "seventeen", "eighteen", "nineteen"
  ];

  static const List<String> _ordersOfMagnitude = [
    "", "thousand", "million", "billion", "trillion", "quadrillion", "quintillion",
    "sextillion", "septillion", "octillion", "nonillion", "decillion"
  ];

  static String convert(int number) {
    if (number == 0) {
      return "zero";
    }

    String result = "";
    int i = 0;

    while (number > 0) {
      int hundreds = number % 1000;
      if (hundreds != 0) {
        result = "${_convertHundreds(hundreds)} ${_ordersOfMagnitude[i]} $result";
      }
      i++;
      number ~/= 1000;
    }

    return result.trim();
  }

  static String _convertHundreds(int number) {
    String result = "";
    int digit = number ~/ 100;
    if (digit != 0) {
      result = "${_units[digit]} hundred";
    }
    digit = (number % 100) ~/ 10;
    if (digit == 1) {
      result += " ${_teens[number % 10]}";
    } else {
      if (digit != 0) {
        result += " ${_tens[digit]}";
      }
      digit = number % 10;
      if (digit != 0) {
        result += " ${_units[digit]}";
      }
    }
    return result.trim();
  }
}