import { 
	parseISO, 
	differenceInMilliseconds, differenceInSeconds, differenceInMinutes, differenceInHours, 
	differenceInDays, differenceInWeeks, differenceInMonths, differenceInYears 
} from 'date-fns'
import isDate from "../.internal/isDate"

const enum DateDiffUnit {
	Year = "year",
	Month = "month",
	Week = "week",
	Day = "day",
	Hour = "hour",
	Minute = "minute",
	Second = "second",
	Millisecond = "millisecond"
}

/**
 * @module utils
 */

/**
 * @name dateDiff
 * @static
 * 
 * @description
 * 두 날짜를 비교하여 차이를 반환합니다.
 *
 * @param {Date|Number|String} leftDate - 원래 날짜
 * @param {Date|Number|String} rightDate - 비교할 날짜
 * @param {String} unit - 비교 단위
 * 
 **/ 

function dateDiff(leftDate: Date | string | number, rightDate: Date | string | number, unit: DateDiffUnit = DateDiffUnit.Second): number {
	let d1: Date = isDate(leftDate) ? leftDate as Date : parseISO(leftDate as string)
	let d2: Date = isDate(rightDate) ? rightDate as Date : parseISO(rightDate as string)
	let diff: number = 0
	
	switch(unit) {
		case DateDiffUnit.Millisecond:
			diff = differenceInMilliseconds(d1, d2)
			break

		case DateDiffUnit.Second:
			diff = differenceInSeconds(d1, d2)
			break

		case DateDiffUnit.Minute:
			diff = differenceInMinutes(d1, d2)
			break

		case DateDiffUnit.Hour:
			diff = differenceInHours(d1, d2)
			break

		case DateDiffUnit.Day:
			diff = differenceInDays(d1, d2)
			break

		case DateDiffUnit.Week:
			diff = differenceInWeeks(d1, d2)
			break

		case DateDiffUnit.Month:
			diff = differenceInMonths(d1, d2)
			break

		case DateDiffUnit.Year:
			diff = differenceInYears(d1, d2)
			break
		
		default:
			break
	}

	return diff
}

export default dateDiff