@burglekitt/gmt/dist/unix/interval/intervalIntersectionUnix.js

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

/**
 * Return the overlapping span of two Unix epoch intervals, or null when they do not overlap.
 *
 * - Compares numeric Unix epoch values directly.
 * - 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 (non-numeric types, non-finite values).
 *
 * @param aStart Unix epoch value (seconds or milliseconds) — first interval start
 * @param aEnd Unix epoch value (seconds or milliseconds) — first interval end
 * @param bStart Unix epoch value (seconds or milliseconds) — second interval start
 * @param bEnd Unix epoch value (seconds or milliseconds) — second interval end
 * @returns `{ start, end }` with the overlapping span, or null on invalid input / no overlap
 *
 * @example intervalIntersectionUnix(0, 1700000000, 1000000, 2000000) // { start: 1000000, end: 1700000000 }
 * @example intervalIntersectionUnix(0, 1000000, 1000000, 2000000) // { start: 1000000, end: 1000000 }
 * @example intervalIntersectionUnix(0, 1000000, 1000001, 2000000) // null
 * @example intervalIntersectionUnix(NaN, 1700000000, 1000000, 2000000) // null
 * @example intervalIntersectionUnix("0", "1700000000", "1000000", "2000000") // { start: 1000000, end: 1700000000 }
 */
export function intervalIntersectionUnix(aStart, aEnd, bStart, bEnd) {
    if (typeof aStart !== "number" && typeof aStart !== "string") {
        return null;
    }
    if (typeof aEnd !== "number" && typeof aEnd !== "string") {
        return null;
    }
    if (typeof bStart !== "number" && typeof bStart !== "string") {
        return null;
    }
    if (typeof bEnd !== "number" && typeof bEnd !== "string") {
        return null;
    }
    const a1 = typeof aStart === "number" ? aStart : Number(aStart);
    const a2 = typeof aEnd === "number" ? aEnd : Number(aEnd);
    const b1 = typeof bStart === "number" ? bStart : Number(bStart);
    const b2 = typeof bEnd === "number" ? bEnd : Number(bEnd);
    if (!Number.isFinite(a1) ||
        !Number.isFinite(a2) ||
        !Number.isFinite(b1) ||
        !Number.isFinite(b2)) {
        return null;
    }
    if (a1 > a2) {
        return null;
    }
    if (b1 > b2) {
        return null;
    }
    if (a2 < b1 || b2 < a1) {
        return null;
    }
    return {
        start: Math.max(a1, b1),
        end: Math.min(a2, b2),
    };
}