toRanges function

Implementation

List<(int, int)> toRanges(List<Object> ranges) {
  if (ranges.isEmpty) {
    throw ArgumentError.value(ranges, 'ranges', 'Must not be empty');
  }

  final result = <(int, int)>[];
  for (final element in ranges) {
    Never error() {
      throw ArgumentError.value(element, 'range', ' Invalid range');
    }

    int toInt(String value) {
      final runes = value.runes.toList();
      if (runes.length == 1) {
        return runes[0];
      }

      error();
    }

    var done = false;
    if (element is String) {
      final runes = element.runes.toList();
      if (runes.isNotEmpty) {
        done = true;
        for (var i = 0; i < runes.length; i++) {
          final rune = runes[i];
          result.add((rune, rune));
        }
      }
    }

    if (!done) {
      final range = switch (element) {
        final int i => (i, i),
        final (String, String) i => (toInt(i.$1), toInt(i.$2)),
        final (String, int) i => (toInt(i.$1), i.$2),
        final (int, String) i => (i.$1, toInt(i.$2)),
        final (int, int) i => (i.$1, i.$2),
        _ => error(),
      };
      result.add(range);
    }
  }

  return normalizeRanges(result);
}