src/utils/rangeContainsDayOfWeek.ts

import { type DateLib, defaultDateLib } from "../classes/DateLib.js";

/**
 * Checks if a date range contains one or more specified days of the week.
 *
 * @since 9.2.2
 * @param range - The date range to check.
 * @param dayOfWeek - The day(s) of the week to check for (`0-6`, where `0` is
 *   Sunday).
 * @param dateLib - The date utility library instance.
 * @returns `true` if the range contains the specified day(s) of the week,
 *   otherwise `false`.
 * @group Utilities
 */
export function rangeContainsDayOfWeek(
  range: { from: Date; to: Date },
  dayOfWeek: number | number[],
  dateLib: DateLib = defaultDateLib,
) {
  const dayOfWeekArr = !Array.isArray(dayOfWeek) ? [dayOfWeek] : dayOfWeek;
  let date = range.from;
  const totalDays = dateLib.differenceInCalendarDays(range.to, range.from);

  // iterate at maximum one week or the total days if the range is shorter than one week
  const totalDaysLimit = Math.min(totalDays, 6);
  for (let i = 0; i <= totalDaysLimit; i++) {
    if (dayOfWeekArr.includes(date.getDay())) {
      return true;
    }
    date = dateLib.addDays(date, 1);
  }
  return false;
}