@burglekitt/gmt/dist/utc/interval/intervalIntersectionUtc.js

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

import { Temporal } from "@js-temporal/polyfill";
import { isLeapSecond } from "../../plain/validate/isLeapSecond.js";
import { utcDateTime } from "../../regex/utc-date-time.js";
/**
 * Return the overlapping span of two UTC intervals, or null when they do not overlap.
 *
 * - Uses `Temporal.Instant.compare` for comparison (same instant semantics).
 * - Adjacent intervals (e.g. `aEnd === bStart`) share one instant and DO overlap.
 * - Returns `null` if either interval is invalid (`start > end`).
 * - Returns `null` on invalid input (wrong type, malformed strings, leap seconds).
 *
 * @param aStart ISO 8601 UTC datetime string for the first interval start
 * @param aEnd ISO 8601 UTC datetime string for the first interval end
 * @param bStart ISO 8601 UTC datetime string for the second interval start
 * @param bEnd ISO 8601 UTC datetime string for the second interval end
 * @returns `{ start, end }` with the overlapping span, or null on invalid input / no overlap
 *
 * @example intervalIntersectionUtc("2024-01-01T00:00:00Z", "2024-06-30T23:59:59Z", "2024-04-01T00:00:00Z", "2024-12-31T23:59:59Z") // { start: "2024-04-01T00:00:00Z", end: "2024-06-30T23:59:59Z" }
 * @example intervalIntersectionUtc("2024-01-01T00:00:00Z", "2024-06-30T23:59:59Z", "2024-07-01T00:00:00Z", "2024-12-31T23:59:59Z") // null
 * @example intervalIntersectionUtc("2024-01-01T00:00:00Z", "2024-06-30T23:59:59Z", "2024-07-02T00:00:00Z", "2024-12-31T23:59:59Z") // null
 * @example intervalIntersectionUtc("invalid", "2024-06-30T23:59:59Z", "2024-04-01T00:00:00Z", "2024-12-31T23:59:59Z") // null
 */
export function intervalIntersectionUtc(aStart, aEnd, bStart, bEnd) {
    if (typeof aStart !== "string" ||
        typeof aEnd !== "string" ||
        typeof bStart !== "string" ||
        typeof bEnd !== "string") {
        return null;
    }
    if (!utcDateTime.test(aStart) ||
        !utcDateTime.test(aEnd) ||
        !utcDateTime.test(bStart) ||
        !utcDateTime.test(bEnd)) {
        return null;
    }
    if (isLeapSecond(aStart) ||
        isLeapSecond(aEnd) ||
        isLeapSecond(bStart) ||
        isLeapSecond(bEnd)) {
        return null;
    }
    try {
        const aSI = Temporal.Instant.from(aStart);
        const aEI = Temporal.Instant.from(aEnd);
        const bSI = Temporal.Instant.from(bStart);
        const bEI = Temporal.Instant.from(bEnd);
        if (Temporal.Instant.compare(aSI, aEI) > 0) {
            return null;
        }
        if (Temporal.Instant.compare(bSI, bEI) > 0) {
            return null;
        }
        if (Temporal.Instant.compare(aEI, bSI) < 0 ||
            Temporal.Instant.compare(bEI, aSI) < 0) {
            return null;
        }
        const start = Temporal.Instant.compare(aSI, bSI) >= 0 ? aSI : bSI;
        const end = Temporal.Instant.compare(aEI, bEI) <= 0 ? aEI : bEI;
        return { start: start.toString(), end: end.toString() };
    }
    catch {
        return null;
    }
}