/* eslint-disable eslint-comments/no-unlimited-disable */
/* eslint-disable */
// @ts-nocheck

import { normalizeDates } from '../_lib/normalizeDates/index.ts';
import { compareAsc } from '../compareAsc/index.ts';
import { differenceInCalendarMonths } from '../differenceInCalendarMonths/index.ts';
import { isLastDayOfMonth } from '../isLastDayOfMonth/index.ts';
import type { ContextOptions, DateArg } from '../types.ts';

/**
 * The {@link differenceInMonths} function options.
 */
export interface DifferenceInMonthsOptions extends ContextOptions<Date> {}

/**
 * @name differenceInMonths
 * @category Month Helpers
 * @summary Get the number of full months between the given dates.
 *
 * @param laterDate - The later date
 * @param earlierDate - The earlier date
 * @param options - An object with options
 *
 * @returns The number of full months
 *
 * @example
 * // How many full months are between 31 January 2014 and 1 September 2014?
 * const result = differenceInMonths(new Date(2014, 8, 1), new Date(2014, 0, 31))
 * //=> 7
 */
export function differenceInMonths(
  laterDate: DateArg<Date> & {},
  earlierDate: DateArg<Date> & {},
  options?: DifferenceInMonthsOptions | undefined,
): number {
  const [laterDate_, workingLaterDate, earlierDate_] = normalizeDates(options?.in, laterDate, laterDate, earlierDate);

  const sign = compareAsc(workingLaterDate, earlierDate_);
  const difference = Math.abs(differenceInCalendarMonths(workingLaterDate, earlierDate_));

  if (difference < 1) return 0;

  if (workingLaterDate.getMonth() === 1 && workingLaterDate.getDate() > 27) workingLaterDate.setDate(30);

  workingLaterDate.setMonth(workingLaterDate.getMonth() - sign * difference);

  let isLastMonthNotFull = compareAsc(workingLaterDate, earlierDate_) === -sign;

  if (isLastDayOfMonth(laterDate_) && difference === 1 && compareAsc(laterDate_, earlierDate_) === 1) {
    isLastMonthNotFull = false;
  }

  const result = sign * (difference - +isLastMonthNotFull);
  return result === 0 ? 0 : result;
}

/* eslint-enable */