@burglekitt/gmt/dist/zoned/calculate/startOfQuarterForZoned.js

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

import { Temporal } from "@js-temporal/polyfill";
import { isValidZonedDateTime } from "../validate/index.js";
/**
 * Return the start of the quarter for a given zoned ISO datetime.
 *
 * - Calculates which quarter (1-4) the date falls into and returns the first day of that quarter.
 * - `disambiguation` controls DST gap/overlap resolution when the quarter-start boundary lands on an ambiguous local time: "compatible" (default, matches Temporal's default), "earlier", "later", or "reject" (throws, resulting in "").
 * - `offset` controls whether the source's existing UTC offset is kept when computing the new boundary: "prefer" (Temporal's own default — keeps the source offset whenever still valid, which **makes `disambiguation` inert** in the (rare) common-zone case since quarter boundaries don't fall on DST transitions), "use", "ignore" (**this function's default** — always recomputes from time zone + local time, discarding the stale offset; this is what makes `disambiguation` actually take effect where a quarter boundary does coincide with a transition), or "reject" (throws if the source offset is invalid for the new fields, independent of `disambiguation`). Leave `offset` at its default unless you specifically need Temporal's raw `.with()` semantics.
 * - `fractionalSecondDigits` controls how many fractional seconds are included in the output: 0 (default — no fractional seconds), 3 (milliseconds), 6 (microseconds), or 9 (nanoseconds).
 * - Validation is performed on the input.
 *
 * @param value ISO ZonedDateTime string
 * @param optionsArg optional: disambiguation ("compatible" | "earlier" | "later" | "reject"), offset ("prefer" | "use" | "ignore" | "reject", default "ignore"), fractionalSecondDigits (0 | 3 | 6 | 9, default 0)
 * @returns ISO ZonedDateTime string for the start of the quarter, or "" on invalid input
 *
 * @example startOfQuarterForZoned("2024-02-15T14:30:00+00:00[UTC]") // "2024-01-01T00:00:00+00:00[UTC]"
 * @example startOfQuarterForZoned("2024-05-10T10:00:00+00:00[UTC]") // "2024-04-01T00:00:00+00:00[UTC]"
 * @example startOfQuarterForZoned("2024-11-20T08:00:00+00:00[UTC]") // "2024-10-01T00:00:00+00:00[UTC]"
 * @example startOfQuarterForZoned("2024-02-15T14:30:00+00:00[UTC]", { fractionalSecondDigits: 3 }) // "2024-01-01T00:00:00.000+00:00[UTC]"
 * @example startOfQuarterForZoned("invalid") // ""
 */
export function startOfQuarterForZoned(value, optionsArg) {
    if (!isValidZonedDateTime(value)) {
        return "";
    }
    const disambiguation = optionsArg?.disambiguation ?? "compatible";
    const offset = optionsArg?.offset ?? "ignore";
    const fractionalSecondDigits = optionsArg?.fractionalSecondDigits ?? 0;
    try {
        const zdt = Temporal.ZonedDateTime.from(value);
        const month = zdt.month;
        const quarterStartMonth = Math.floor((month - 1) / 3) * 3 + 1;
        return zdt
            .with({ month: quarterStartMonth, day: 1, hour: 0, minute: 0, second: 0 }, { disambiguation, offset })
            .toString({ fractionalSecondDigits });
    }
    catch {
        return "";
    }
}