src/helpers/getDays.ts

import type { CalendarDay, CalendarMonth } from "../classes/index.js";

/**
 * Returns all the days belonging to the calendar by merging the days in the
 * weeks for each month.
 *
 * @param calendarMonths The array of calendar months.
 * @returns An array of `CalendarDay` objects representing all the days in the
 *   calendar.
 */
export function getDays(calendarMonths: CalendarMonth[]) {
  const initialDays: CalendarDay[] = [];
  return calendarMonths.reduce((days, month) => {
    const weekDays: CalendarDay[] = month.weeks.reduce((weekDays, week) => {
      return weekDays.concat(week.days.slice());
    }, initialDays.slice());
    return days.concat(weekDays.slice());
  }, initialDays.slice());
}