DateParts.of constructor

DateParts.of(List<DatePart> parts)

Implementation

factory DateParts.of(List<DatePart> parts) {
  final copy = {...parts.asMap()};
  int? monthIndex, yearIndex, dayIndex;
  int? month, year, day;
  parts.forEachIndexed((item, index) {
    if (item.period == Period.month) {
      monthIndex = index;
      month = item.value;
    } else if (item.value > 1000) {
      yearIndex = index;
      year = item.value;
    }
  });
  copy.remove(monthIndex);
  copy.remove(yearIndex);
  yearIndex = monthIndex = null;

  /// Second pass
  copy.values.forEachIndexed((item, index) {
    if (year != null && item.value > 12 && item.value <= 31) {
      /// We already have a year, so any value larger than 12 must be the day
      day = item.value;
      dayIndex = index;
    } else if (year == null && item.value > 31) {
      /// Any value larger than 31 must be a year
      year = item.value;
      yearIndex = index;
    }
  });
  copy.remove(dayIndex);
  copy.remove(yearIndex);

  dayIndex = yearIndex = monthIndex = null;

  List<int> toRemove = [];
  List<int> invalidValues = [];

  /// Last pass
  copy.values.forEachIndexed((item, index) {
    if (year != null && day != null && month == null && item.value < 12) {
      month = item.value;
      monthIndex = index;
    } else if (month != null && day != null && year == null) {
      year = item.value;
      yearIndex = index;
    } else if (month != null && year != null && item.value <= 31) {
      day = item.value;
      dayIndex = index;
    } else if (year != null && item.value > 31) {
      toRemove.add(index);
      invalidValues.add(item.value);
    }
  });
  copy.remove(dayIndex);
  copy.remove(yearIndex);
  copy.remove(monthIndex);
  toRemove.forEach(copy.remove);

  return DateParts(
    year,
    month,
    day,
    copy.values.map((v) => v.value).toList(),
    invalidValues,
  );
}