cardReviewedAtDateLength method
Implementation
int cardReviewedAtDateLength(DateTime date) {
return _state!.cardStates.values.where((st) {
final dueDate = calculateDueDate(st!);
return dueDate == null ||
dueDate.year == date.year &&
dueDate.month == date.month &&
dueDate.day == date.day;
}).length;
}