@burglekitt/gmt/dist/plain/interval/intervalIntersectionTime.js

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

import { Temporal } from "@js-temporal/polyfill";
import { plainTime } from "../../regex/index.js";
/**
 * Return the overlapping span of two time intervals, or null when they do not overlap.
 *
 * - Uses `Temporal.PlainTime.compare` for comparison.
 * - 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).
 *
 * @param aStart ISO 8601 time string for the first interval start
 * @param aEnd ISO 8601 time string for the first interval end
 * @param bStart ISO 8601 time string for the second interval start
 * @param bEnd ISO 8601 time string for the second interval end
 * @returns `{ start, end }` with the overlapping span, or null on invalid input / no overlap
 *
 * @example intervalIntersectionTime("09:00:00", "17:00:00", "12:00:00", "18:00:00") // { start: "12:00:00", end: "17:00:00" }
 * @example intervalIntersectionTime("09:00:00", "17:00:00", "17:00:00", "18:00:00") // { start: "17:00:00", end: "17:00:00" }
 * @example intervalIntersectionTime("09:00:00", "17:00:00", "18:00:00", "20:00:00") // null
 * @example intervalIntersectionTime("09:00:00", "17:00:00", "10:00:00", "11:00:00") // { start: "10:00:00", end: "11:00:00" }
 * @example intervalIntersectionTime("invalid", "17:00:00", "12:00:00", "18:00:00") // null
 */
export function intervalIntersectionTime(aStart, aEnd, bStart, bEnd) {
    if (typeof aStart !== "string" ||
        typeof aEnd !== "string" ||
        typeof bStart !== "string" ||
        typeof bEnd !== "string") {
        return null;
    }
    if (!plainTime.test(aStart) ||
        !plainTime.test(aEnd) ||
        !plainTime.test(bStart) ||
        !plainTime.test(bEnd)) {
        return null;
    }
    try {
        const aS = Temporal.PlainTime.from(aStart);
        const aE = Temporal.PlainTime.from(aEnd);
        const bS = Temporal.PlainTime.from(bStart);
        const bE = Temporal.PlainTime.from(bEnd);
        if (Temporal.PlainTime.compare(aS, aE) > 0) {
            return null;
        }
        if (Temporal.PlainTime.compare(bS, bE) > 0) {
            return null;
        }
        if (Temporal.PlainTime.compare(aE, bS) < 0 ||
            Temporal.PlainTime.compare(bE, aS) < 0) {
            return null;
        }
        const start = Temporal.PlainTime.compare(aS, bS) >= 0 ? aS : bS;
        const end = Temporal.PlainTime.compare(aE, bE) <= 0 ? aE : bE;
        return { start: start.toString(), end: end.toString() };
    }
    catch {
        return null;
    }
}