Method _modifyDateValue

packages/main/src/DateRangePicker.ts:496–523

* @override

(amount: number, unit: string, preserveDate?: boolean)

	 * @override
	 */
	async _modifyDateValue(amount: number, unit: string, preserveDate?: boolean) {
		if (!this._endDateTimestamp) { // If empty or only one date -> treat as datepicker entirely
			return super._modifyDateValue(amount, unit, preserveDate);
		}

		let caretPos: number = this._dateTimeInput.getCaretPosition()!; // caret position is always number for input of type text;
		let newValue: string;

		if (caretPos <= this.value.indexOf(this._effectiveDelimiter)) { // The user is focusing the first date -> change it and keep the second date
			const startDateModified = modifyDateBy(CalendarDate.fromTimestamp(this._startDateTimestamp! * 1000), amount, unit, preserveDate, this._minDate, this._maxDate);
			const newStartDateTimestamp = startDateModified.valueOf() / 1000;
			if (newStartDateTimestamp > this._endDateTimestamp) { // dates flipped -> move the caret to the same position but on the last date
				caretPos += Math.ceil(this.value.length / 2);
			}
			newValue = this._buildValue(newStartDateTimestamp, this._endDateTimestamp); // the value will be normalized so we don't try to order them here
		} else {
			const endDateModified = modifyDateBy(CalendarDate.fromTimestamp(this._endDateTimestamp * 1000), amount, unit, preserveDate, this._minDate, this._maxDate);
			const newEndDateTimestamp = endDateModified.valueOf() / 1000;
			newValue = this._buildValue(this._startDateTimestamp, newEndDateTimestamp); // the value will be normalized so we don't try to order them here
			if (newEndDateTimestamp < this._startDateTimestamp!) { // dates flipped -> move the caret to the same position but on the first date
				caretPos -= Math.ceil(this.value.length / 2);
			}
		}
		this._updateValueAndFireEvents(newValue, true, ["change", "value-changed"]);

		await renderFinished();
		this._dateTimeInput.setCaretPosition(caretPos); // Return the caret to the previous (or the adjusted, if dates flipped) position after rendering
	}

	get _effectiveDelimiter(): string {
		return this.delimiter || DEFAULT_DELIMITER;