next method

LunarMonth next(int n)

Implementation

LunarMonth next(int n) {
  if (0 == n) {
    return LunarMonth.fromYm(_year, _month)!;
  } else if (n > 0) {
    int rest = n;
    int ny = _year;
    int iy = ny;
    int im = _month;
    int index = 0;
    List<LunarMonth> months = LunarYear.fromYear(ny).getMonths();
    while (true) {
      int size = months.length;
      for (int i = 0; i < size; i++) {
        LunarMonth m = months[i];
        if (m.getYear() == iy && m.getMonth() == im) {
          index = i;
          break;
        }
      }
      int more = size - index - 1;
      if (rest < more) {
        break;
      }
      rest -= more;
      LunarMonth lastMonth = months[size - 1];
      iy = lastMonth.getYear();
      im = lastMonth.getMonth();
      ny++;
      months = LunarYear.fromYear(ny).getMonths();
    }
    return months[index + rest];
  } else {
    int rest = -n;
    int ny = _year;
    int iy = ny;
    int im = _month;
    int index = 0;
    List<LunarMonth> months = LunarYear.fromYear(ny).getMonths();
    while (true) {
      int size = months.length;
      for (int i = 0; i < size; i++) {
        LunarMonth m = months[i];
        if (m.getYear() == iy && m.getMonth() == im) {
          index = i;
          break;
        }
      }
      if (rest <= index) {
        break;
      }
      rest -= index;
      LunarMonth firstMonth = months[0];
      iy = firstMonth.getYear();
      im = firstMonth.getMonth();
      ny--;
      months = LunarYear.fromYear(ny).getMonths();
    }
    return months[index - rest];
  }
}