Function cycleDate

packages/@internationalized/date/src/manipulation.ts:296–364

(
  value: CalendarDate | CalendarDateTime,
  field: DateField,
  amount: number,
  options?: CycleOptions
)

  options?: CycleOptions
): CalendarDate;
export function cycleDate(
  value: CalendarDate | CalendarDateTime,
  field: DateField,
  amount: number,
  options?: CycleOptions
): Mutable<CalendarDate | CalendarDateTime> {
  let mutable: Mutable<CalendarDate | CalendarDateTime> = value.copy();

  switch (field) {
    case 'era': {
      let eras = value.calendar.getEras();
      let eraIndex = eras.indexOf(value.era);
      if (eraIndex < 0) {
        throw new Error('Invalid era: ' + value.era);
      }
      eraIndex = cycleValue(eraIndex, amount, 0, eras.length - 1, options?.round);
      mutable.era = eras[eraIndex];

      // Constrain the year and other fields within the era, so the era doesn't change when we balance below.
      constrain(mutable);
      break;
    }
    case 'year': {
      if (mutable.calendar.isInverseEra?.(mutable)) {
        amount = -amount;
      }

      // The year field should not cycle within the era as that can cause weird behavior affecting other fields.
      // We need to also allow values < 1 so that decrementing goes to the previous era. If we get -Infinity back
      // we know we wrapped around after reaching 9999 (the maximum), so set the year back to 1.
      mutable.year = cycleValue(value.year, amount, -Infinity, 9999, options?.round);
      if (mutable.year === -Infinity) {
        mutable.year = 1;
      }

      if (mutable.calendar.balanceYearMonth) {
        mutable.calendar.balanceYearMonth(mutable, value);
      }
      break;
    }
    case 'month':
      mutable.month = cycleValue(
        value.month,
        amount,
        1,
        value.calendar.getMonthsInYear(value),
        options?.round
      );
      break;
    case 'day':
      mutable.day = cycleValue(
        value.day,
        amount,
        1,
        value.calendar.getDaysInMonth(value),
        options?.round
      );
      break;