Range with padding about dart-petitparser HOT 5 CLOSED

Parser<String> _iso8601DateTime() {
  Parser<String> num2Digit({int min, int max}) =>
      digit().repeat(2).flatten().callCC(
        (continuation, context) {
          final result = continuation(context);
          if (result.isFailure) return result;

          final intValue = int.parse(result.value);

          if (max != null && intValue > max)
            return context.failure('Greater than $max');

          if (min != null && intValue < min)
            return context.failure('Less than $min');

          return result;
        },
      );

  final dateFullYear = digit().repeat(4).flatten();
  final dateMonth = num2Digit(min: 1, max: 12);
  final dateMday = num2Digit(min: 1, max: 31);

  final timeHour = num2Digit(max: 23);
  final timeMinute = num2Digit(max: 59);
  final timeSecond = num2Digit(max: 59);

  final timeSecFrac = (char('.') & digit().plus()).flatten();
  final timeOffset = char('Z');

  final partialTime = (timeHour &
      char(':') &
      timeMinute &
      char(':') &
      timeSecond &
      timeSecFrac.optional());

  final fullDate = dateFullYear & char('-') & dateMonth & char('-') & dateMday;
  final fullTime = partialTime & timeOffset;

  return (fullDate & char('T') & fullTime).flatten();
}

final iso8601DateTime = _iso8601DateTime();

import "package:test/test.dart";
import 'iso8601.dart';
import 'package:petitparser/petitparser.dart';

void main() {
  group('iso8601', () {
    test('valid time', () {
      final res = iso8601DateTime.parse('2020-10-08T21:57:50.118523Z');
      expect(res.value, '2020-10-08T21:57:50.118523Z');
    });
    test('time with month out of range', () {
      final res = iso8601DateTime.parse('2020-15-08T21:57:50.118523Z');
      expect(res.isSuccess, false);
    });
    test('skips over invalid times', () {
      final res = iso8601DateTime.matchesSkipping(
          'hi 2020-10-08T21:57:50.118523Z 2020-15-08T21:57:50.118523Z 2020-12-08T21:57:50.118523Z yay cool');
      expect(
          res, ['2020-10-08T21:57:50.118523Z', '2020-12-08T21:57:50.118523Z']);
    });
  });
}

Parser<String> num2Digit(int n) => digit().repeat(2).flatten().map((str) {
  final value = int.parse(str);
  if (value > n) throw InvalidArgument(str);
  return value;
}); 

List<DocumentToken> tokenizeBody(
  String message, {
  Iterable<User> users = const [],
}) =>
    documentTokenParser(users).matchesSkipping(message);

Parser<String> num2Digit(int n) => digit().repeat(2).flatten().callCC((continuation, context) {
  final result = continuation(context);
  if (result.isSuccess && int.parse(result.value) > n) {
    return context.failure('Larger than $n');
  } else {
    return result;
  }
});