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

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

import { Temporal } from "@js-temporal/polyfill";
import { plainDateTime } from "../../regex/index.js";
/**
 * Return the overlapping span of two datetime intervals, or null when they do not overlap.
 *
 * - Uses `Temporal.PlainDateTime.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 datetime string for the first interval start
 * @param aEnd ISO 8601 datetime string for the first interval end
 * @param bStart ISO 8601 datetime string for the second interval start
 * @param bEnd ISO 8601 datetime string for the second interval end
 * @returns `{ start, end }` with the overlapping span, or null on invalid input / no overlap
 *
 * @example intervalIntersectionDateTime("2024-01-01T10:00:00", "2024-06-30T23:59:59", "2024-04-01T00:00:00", "2024-12-31T23:59:59") // { start: "2024-04-01T00:00:00", end: "2024-06-30T23:59:59" }
 * @example intervalIntersectionDateTime("2024-01-01T10:00:00", "2024-06-30T23:59:59", "2024-07-01T00:00:00", "2024-12-31T23:59:59") // null
 * @example intervalIntersectionDateTime("2024-01-01T10:00:00", "2024-06-30T23:59:59", "2024-07-02T00:00:00", "2024-12-31T23:59:59") // null
 * @example intervalIntersectionDateTime("invalid", "2024-06-30T23:59:59", "2024-04-01T00:00:00", "2024-12-31T23:59:59") // null
 */
export function intervalIntersectionDateTime(aStart, aEnd, bStart, bEnd) {
    if (typeof aStart !== "string" ||
        typeof aEnd !== "string" ||
        typeof bStart !== "string" ||
        typeof bEnd !== "string") {
        return null;
    }
    if (!plainDateTime.test(aStart) ||
        !plainDateTime.test(aEnd) ||
        !plainDateTime.test(bStart) ||
        !plainDateTime.test(bEnd)) {
        return null;
    }
    try {
        const aS = Temporal.PlainDateTime.from(aStart);
        const aE = Temporal.PlainDateTime.from(aEnd);
        const bS = Temporal.PlainDateTime.from(bStart);
        const bE = Temporal.PlainDateTime.from(bEnd);
        if (Temporal.PlainDateTime.compare(aS, aE) > 0) {
            return null;
        }
        if (Temporal.PlainDateTime.compare(bS, bE) > 0) {
            return null;
        }
        if (Temporal.PlainDateTime.compare(aE, bS) < 0 ||
            Temporal.PlainDateTime.compare(bE, aS) < 0) {
            return null;
        }
        const start = Temporal.PlainDateTime.compare(aS, bS) >= 0 ? aS : bS;
        const end = Temporal.PlainDateTime.compare(aE, bE) <= 0 ? aE : bE;
        return { start: start.toString(), end: end.toString() };
    }
    catch {
        return null;
    }
}