import toDate from '../toDate/index'
import type { Interval } from '../types'
import requiredArgs from '../_lib/requiredArgs/index'

/**
 * @name eachMonthOfInterval
 * @category Interval Helpers
 * @summary Return the array of months within the specified time interval.
 *
 * @description
 * Return the array of months within the specified time interval.
 *
 * @param {Interval} interval - the interval. See [Interval]{@link https://date-fns.org/docs/Interval}
 * @returns {Date[]} the array with starts of months from the month of the interval start to the month of the interval end
 * @throws {TypeError} 1 argument required
 * @throws {RangeError} The start of an interval cannot be after its end
 * @throws {RangeError} Date in interval cannot be `Invalid Date`
 *
 * @example
 * // Each month between 6 February 2014 and 10 August 2014:
 * const result = eachMonthOfInterval({
 *   start: new Date(2014, 1, 6),
 *   end: new Date(2014, 7, 10)
 * })
 * //=> [
 * //   Sat Feb 01 2014 00:00:00,
 * //   Sat Mar 01 2014 00:00:00,
 * //   Tue Apr 01 2014 00:00:00,
 * //   Thu May 01 2014 00:00:00,
 * //   Sun Jun 01 2014 00:00:00,
 * //   Tue Jul 01 2014 00:00:00,
 * //   Fri Aug 01 2014 00:00:00
 * // ]
 */
export default function eachMonthOfInterval(dirtyInterval: Interval): Date[] {
  requiredArgs(1, arguments)

  const interval = dirtyInterval || {}
  const startDate = toDate(interval.start)
  const endDate = toDate(interval.end)

  const endTime = endDate.getTime()
  const dates = []

  // Throw an exception if start date is after end date or if any date is `Invalid Date`
  if (!(startDate.getTime() <= endTime)) {
    throw new RangeError('Invalid interval')
  }

  const currentDate = startDate
  currentDate.setHours(0, 0, 0, 0)
  currentDate.setDate(1)

  while (currentDate.getTime() <= endTime) {
    dates.push(toDate(currentDate))
    currentDate.setMonth(currentDate.getMonth() + 1)
  }

  return dates
}