import { Temporal } from "@js-temporal/polyfill";
import type { RoundingOptions, TimeDurationUnit } from "../../types/index.js";
/**
 * Return the difference between two PlainTime values in the requested unit.
 *
 * - Returns `null` for invalid inputs.
 * - Uses Temporal.PlainTime.until with `largestUnit` and extracts the requested unit.
 *
 * `smallestUnit`, `roundingIncrement`, and `roundingMode` control optional rounding of the result,
 * per Temporal's DifferenceOptions — e.g. `{ smallestUnit: "minute", roundingMode: "halfExpand" }`
 * rounds the difference to the nearest minute before extracting the requested unit.
 * - When `units` is an array, `smallestUnit` must not be coarser than the largest unit in the
 *   array (e.g. `["minute", "second"]` with `smallestUnit: "hour"`) — this combination is
 *   rejected by Temporal and returns null, same as other invalid input.
 *
 * @param time1 ISO PlainTime string for the start
 * @param time2 ISO PlainTime string for the end
 * @param units TimeDurationUnit | TimeDurationUnit[] to measure the difference
 * @param options optional: smallestUnit, roundingIncrement, roundingMode (Temporal.DifferenceOptions rounding controls)
 * @returns numeric difference in the requested unit, or null on invalid input
 *
 * @example diffTime("12:00:00", "14:30:00", "hour") // 2
 * @example diffTime("invalid", "14:30:00", "hour") // null
 */
export declare function diffTime(time1: string, time2: string, units: TimeDurationUnit | TimeDurationUnit[], options?: RoundingOptions<Temporal.TimeUnit>): number | Record<TimeDurationUnit, number> | null;