@burglekitt/gmt/dist/plain/calculate/closestDateTo.js

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

import { Temporal } from "@js-temporal/polyfill";
import { isValidDate } from "../validate/index.js";
/**
 * Return the candidate date nearest to `target` by calendar distance.
 *
 * - Distance is measured in whole days using `Temporal.PlainDate.compare`.
 * - Returns `null` if the candidates array is empty or contains no valid dates.
 * - Returns `null` if `target` is invalid.
 * - On a tie (two equidistant candidates), returns the first one in array order.
 *
 * @param target ISO PlainDate string to measure distance from
 * @param candidates Array of ISO PlainDate strings to choose from
 * @returns The nearest candidate date string, or null on invalid input
 *
 * @example closestDateTo("2024-03-15", ["2024-03-01", "2024-03-20", "2024-03-18"]) // "2024-03-18"
 * @example closestDateTo("2024-03-15", ["2024-03-01", "2024-03-29"]) // "2024-03-01"
 * @example closestDateTo("2024-03-15", []) // null
 * @example closestDateTo("invalid", ["2024-03-01"]) // null
 */
export function closestDateTo(target, candidates) {
    if (!isValidDate(target) ||
        !candidates.length ||
        !candidates.some(isValidDate)) {
        return null;
    }
    try {
        const t = Temporal.PlainDate.from(target);
        const validCandidates = candidates.filter(isValidDate);
        const parsed = validCandidates.map((c) => ({
            str: c,
            date: Temporal.PlainDate.from(c),
        }));
        const closest = parsed.reduce((best, candidate) => {
            const bestDist = Math.abs(t.until(best.date).days);
            const candDist = Math.abs(t.until(candidate.date).days);
            return candDist < bestDist ? candidate : best;
        }, parsed[0]);
        return closest.str;
    }
    catch {
        return null;
    }
}