package analytics

import (
	"fmt"
	"strings"
	"time"
)

var jalaliBreaks = [...]int{-61, 9, 38, 199, 426, 686, 756, 818, 1111, 1181, 1210, 1635, 2060, 2097, 2192, 2262, 2324, 2394, 2456, 3178}

var jalaliMonthNames = [...]string{
	"فروردین", "اردیبهشت", "خرداد", "تیر", "مرداد", "شهریور",
	"مهر", "آبان", "آذر", "دی", "بهمن", "اسفند",
}

var persianSeasonNames = [...]string{"بهار", "تابستان", "پاییز", "زمستان"}

type jalaliCalculation struct {
	leap  int
	gy    int
	march int
}

func jalaliCalendar(jy int) jalaliCalculation {
	gy := jy + 621
	leapJ := -14
	jp := jalaliBreaks[0]
	jump := 0
	for index := 1; index < len(jalaliBreaks); index++ {
		jm := jalaliBreaks[index]
		jump = jm - jp
		if jy < jm {
			break
		}
		leapJ += jump/33*8 + (jump%33)/4
		jp = jm
	}
	n := jy - jp
	leapJ += n/33*8 + (n%33+3)/4
	if jump%33 == 4 && jump-n == 4 {
		leapJ++
	}
	leapG := gy/4 - ((gy/100+1)*3)/4 - 150
	march := 20 + leapJ - leapG
	if jump-n < 6 {
		n = n - jump + (jump+4)/33*33
	}
	leap := ((n+1)%33 - 1) % 4
	if leap == -1 {
		leap = 4
	}
	return jalaliCalculation{leap: leap, gy: gy, march: march}
}

func gregorianDayNumber(gy, gm, gd int) int {
	d := ((gy+(gm-8)/6+100100)*1461)/4 + (153*((gm+9)%12)+2)/5 + gd - 34840408
	d = d - (((gy+100100+(gm-8)/6)/100)*3)/4 + 752
	return d
}

func gregorianFromDayNumber(dayNumber int) (int, int, int) {
	j := 4*dayNumber + 139361631
	j = j + (((4*dayNumber+183187720)/146097)*3/4)*4 - 3908
	i := ((j % 1461) / 4 * 5) + 308
	gd := (i%153)/5 + 1
	gm := (i/153)%12 + 1
	gy := j/1461 - 100100 + (8-gm)/6
	return gy, gm, gd
}

func jalaliDayNumber(jy, jm, jd int) int {
	calculation := jalaliCalendar(jy)
	return gregorianDayNumber(calculation.gy, 3, calculation.march) + (jm-1)*31 - (jm/7)*(jm-7) + jd - 1
}

func jalaliToGregorian(jy, jm, jd int) (int, int, int) {
	return gregorianFromDayNumber(jalaliDayNumber(jy, jm, jd))
}

func gregorianToJalali(gy, gm, gd int) (int, int, int) {
	jy := gy - 621
	calculation := jalaliCalendar(jy)
	dayNumber := gregorianDayNumber(gy, gm, gd)
	firstFarvardin := gregorianDayNumber(gy, 3, calculation.march)
	k := dayNumber - firstFarvardin
	if k >= 0 {
		if k <= 185 {
			return jy, 1 + k/31, k%31 + 1
		}
		k -= 186
	} else {
		jy--
		k += 179
		if calculation.leap == 1 {
			k++
		}
	}
	return jy, 7 + k/30, k%30 + 1
}

func jalaliDate(jy, jm, jd int, location *time.Location) time.Time {
	gy, gm, gd := jalaliToGregorian(jy, jm, jd)
	return time.Date(gy, time.Month(gm), gd, 0, 0, 0, 0, location)
}

func previousJalaliMonth(jy, jm int) (int, int) {
	jm--
	if jm == 0 {
		return jy - 1, 12
	}
	return jy, jm
}

func nextJalaliMonth(jy, jm int) (int, int) {
	jm++
	if jm == 13 {
		return jy + 1, 1
	}
	return jy, jm
}

func latestCompletePeriods(datasetStart, datasetMax time.Time, location *time.Location) []Period {
	localStart := datasetStart.In(location)
	localMax := datasetMax.In(location)
	datasetStartDay := time.Date(localStart.Year(), localStart.Month(), localStart.Day(), 0, 0, 0, 0, location)
	dayStart := time.Date(localMax.Year(), localMax.Month(), localMax.Day(), 0, 0, 0, 0, location)
	datasetEnd := dayStart.AddDate(0, 0, 1)

	weekEnd := datasetEnd
	for weekEnd.Weekday() != time.Saturday {
		weekEnd = weekEnd.AddDate(0, 0, -1)
	}
	weekStart := weekEnd.AddDate(0, 0, -7)

	jy, jm, _ := gregorianToJalali(localMax.Year(), int(localMax.Month()), localMax.Day())
	monthStart := jalaliDate(jy, jm, 1, location)
	nextYear, nextMonth := nextJalaliMonth(jy, jm)
	monthEnd := jalaliDate(nextYear, nextMonth, 1, location)
	if monthEnd.After(datasetEnd) {
		jy, jm = previousJalaliMonth(jy, jm)
		monthStart = jalaliDate(jy, jm, 1, location)
		nextYear, nextMonth = nextJalaliMonth(jy, jm)
		monthEnd = jalaliDate(nextYear, nextMonth, 1, location)
	}

	seasonStartMonth := ((jm-1)/3)*3 + 1
	seasonYear := jy
	seasonStart := jalaliDate(seasonYear, seasonStartMonth, 1, location)
	seasonEndYear, seasonEndMonth := seasonYear, seasonStartMonth+3
	if seasonEndMonth > 12 {
		seasonEndYear++
		seasonEndMonth -= 12
	}
	seasonEnd := jalaliDate(seasonEndYear, seasonEndMonth, 1, location)
	if seasonEnd.After(datasetEnd) {
		seasonStartMonth -= 3
		if seasonStartMonth < 1 {
			seasonYear--
			seasonStartMonth += 12
		}
		seasonStart = jalaliDate(seasonYear, seasonStartMonth, 1, location)
		seasonEndYear, seasonEndMonth = seasonYear, seasonStartMonth+3
		if seasonEndMonth > 12 {
			seasonEndYear++
			seasonEndMonth -= 12
		}
		seasonEnd = jalaliDate(seasonEndYear, seasonEndMonth, 1, location)
	}

	dayJY, dayJM, dayJD := gregorianToJalali(dayStart.Year(), int(dayStart.Month()), dayStart.Day())
	weekEndJY, weekEndJM, weekEndJD := gregorianToJalali(weekEnd.AddDate(0, 0, -1).Year(), int(weekEnd.AddDate(0, 0, -1).Month()), weekEnd.AddDate(0, 0, -1).Day())
	weekStartJY, weekStartJM, weekStartJD := gregorianToJalali(weekStart.Year(), int(weekStart.Month()), weekStart.Day())

	periods := []Period{
		newPeriod("d-"+dayStart.Format(time.DateOnly), "DAY", dayStart, datasetEnd,
			fmt.Sprintf("روز %s %s %s", persianNumber(dayJD), jalaliMonthNames[dayJM-1], persianNumber(dayJY)), false),
		newPeriod("w-"+weekStart.Format(time.DateOnly), "WEEK", weekStart, weekEnd,
			fmt.Sprintf("هفته %s %s تا %s %s", persianNumber(weekStartJD), jalaliMonthNames[weekStartJM-1], persianNumber(weekEndJD), jalaliMonthNames[weekEndJM-1]), false),
		newPeriod(fmt.Sprintf("jm-%04d-%02d", jy, jm), "JALALI_MONTH", monthStart, monthEnd,
			fmt.Sprintf("%s %s", jalaliMonthNames[jm-1], persianNumber(jy)), true),
		newPeriod(fmt.Sprintf("ps-%04d-%02d", seasonYear, seasonStartMonth), "PERSIAN_SEASON", seasonStart, seasonEnd,
			fmt.Sprintf("%s %s", persianSeasonNames[(seasonStartMonth-1)/3], persianNumber(seasonYear)), false),
	}
	for index := range periods {
		periods[index].IsComplete = !periods[index].LocalStartAt.Before(datasetStartDay)
	}
	_ = weekEndJY
	_ = weekStartJY
	return periods
}

func newPeriod(id, kind string, localStart, localEnd time.Time, label string, isDefault bool) Period {
	return Period{
		PeriodID: id, PeriodType: kind, StartAt: localStart.UTC(), EndAt: localEnd.UTC(),
		LocalStartAt: localStart, LocalEndAt: localEnd, Timezone: "Asia/Tehran",
		JalaliLabelFA: label, IsComplete: true, IsDefault: isDefault,
	}
}

func persianNumber(value int) string {
	replacer := strings.NewReplacer("0", "۰", "1", "۱", "2", "۲", "3", "۳", "4", "۴", "5", "۵", "6", "۶", "7", "۷", "8", "۸", "9", "۹")
	return replacer.Replace(fmt.Sprint(value))
}