@burglekitt/gmt/dist/internal/dateTimeUnitHelpers.js

Temporal-based date and time utilities with timezone support and polyfill integration

/**
 * Return the start of the specified date-time `unit` for a `Temporal.PlainDateTime`.
 *
 * - Always uses Monday as the week start (consistent with roundDateTime semantics).
 * - Date units (year, month, week) reset the time to midnight.
 * - Does NOT validate the unit — caller ensures it is a DateTimeUnit.
 *
 * @param source Temporal.PlainDateTime to round
 * @param unit DateTimeUnit to specify the unit for the start
 * @returns Temporal.PlainDateTime at the start of the specified unit
 */
export function getStartOfDateTimeUnit(source, unit) {
    switch (unit) {
        case "year":
            return source.with({ month: 1, day: 1 }).withPlainTime();
        case "month":
            return source.with({ day: 1 }).withPlainTime();
        case "week": {
            const daysToSubtract = source.dayOfWeek - 1;
            return source.subtract({ days: daysToSubtract }).withPlainTime();
        }
        default:
            return source.withPlainTime();
    }
}
/**
 * Add `amount` units of the specified date-time `unit` to a `Temporal.PlainDateTime`.
 *
 * - Only year, month, and week are meaningful for the manual rounding path.
 * - Day and time units return the input unchanged (they are handled by
 *   `Temporal.PlainDateTime.round()` in the callers).
 * - Does NOT validate the unit — caller ensures it is a DateTimeUnit.
 *
 * @param date Temporal.PlainDateTime to advance
 * @param unit DateTimeUnit to add
 * @param amount number of units to add
 * @returns new Temporal.PlainDateTime advanced by the specified amount
 */
export function addDateTimeUnit(date, unit, amount) {
    switch (unit) {
        case "year":
            return date.add({ years: amount });
        case "month":
            return date.add({ months: amount });
        case "week":
            return date.add({ days: amount * 7 });
        default:
            return date;
    }
}