import toDate from '../toDate/index'
import requiredArgs from '../_lib/requiredArgs/index'

/**
 * @name max
 * @category Common Helpers
 * @summary Return the latest of the given dates.
 *
 * @description
 * Return the latest of the given dates.
 *
 * ### v2.0.0 breaking changes:
 *
 * - [Changes that are common for the whole library](https://github.com/date-fns/date-fns/blob/master/docs/upgradeGuide.md#Common-Changes).
 *
 * - `max` function now accepts an array of dates rather than spread arguments.
 *
 *   ```javascript
 *   // Before v2.0.0
 *   var date1 = new Date(1989, 6, 10)
 *   var date2 = new Date(1987, 1, 11)
 *   var maxDate = max(date1, date2)
 *
 *   // v2.0.0 onward:
 *   var dates = [new Date(1989, 6, 10), new Date(1987, 1, 11)]
 *   var maxDate = max(dates)
 *   ```
 *
 * @param {Date[]|Number[]} datesArray - the dates to compare
 * @returns {Date} the latest of the dates
 * @throws {TypeError} 1 argument required
 *
 * @example
 * // Which of these dates is the latest?
 * var result = max([
 *   new Date(1989, 6, 10),
 *   new Date(1987, 1, 11),
 *   new Date(1995, 6, 2),
 *   new Date(1990, 0, 1)
 * ])
 * //=> Sun Jul 02 1995 00:00:00
 */
export default function max(dirtyDatesArray: Date[] | string[] | number[]): Date {
  requiredArgs(1, arguments)

  let datesArray
  // `dirtyDatesArray` is Array, Set or Map, or object with custom `forEach` method
  if (dirtyDatesArray && typeof dirtyDatesArray.forEach === 'function') {
    datesArray = dirtyDatesArray

    // If `dirtyDatesArray` is Array-like Object, convert to Array.
  } else if (typeof dirtyDatesArray === 'object' && dirtyDatesArray !== null) {
    datesArray = Array.prototype.slice.call(dirtyDatesArray)
  } else {
    // `dirtyDatesArray` is non-iterable, return Invalid Date
    return new Date(NaN)
  }

  let result: Date | undefined
  datesArray.forEach(function(dirtyDate) {
    const currentDate = toDate(dirtyDate)

    if (result === undefined || result < currentDate || isNaN(Number(currentDate))) {
      result = currentDate
    }
  })

  return result || new Date(NaN)
}
