import { getISOWeekYear } from "./getISOWeekYear.mjs";

/**
 * @name differenceInCalendarISOWeekYears
 * @category ISO Week-Numbering Year Helpers
 * @summary Get the number of calendar ISO week-numbering years between the given dates.
 *
 * @description
 * Get the number of calendar ISO week-numbering years between the given dates.
 *
 * ISO week-numbering year: http://en.wikipedia.org/wiki/ISO_week_date
 *
 * @typeParam DateType - The `Date` type, the function operates on. Gets inferred from passed arguments. Allows to use extensions like [`UTCDate`](https://github.com/date-fns/utc).
 *
 * @param dateLeft - The later date
 * @param dateRight - The earlier date
 *
 * @returns The number of calendar ISO week-numbering years
 *
 * @example
 * // How many calendar ISO week-numbering years are 1 January 2010 and 1 January 2012?
 * const result = differenceInCalendarISOWeekYears(
 *   new Date(2012, 0, 1),
 *   new Date(2010, 0, 1)
 * )
 * //=> 2
 */
export function differenceInCalendarISOWeekYears(dateLeft, dateRight) {
  return getISOWeekYear(dateLeft) - getISOWeekYear(dateRight);
}

// Fallback for modularized imports:
export default differenceInCalendarISOWeekYears;