package venus

import (
	"b612.me/astro/basic"
	"b612.me/astro/calendar"
	"b612.me/astro/planet"
	"errors"
	"time"
)

var (
	ERR_VENUS_NEVER_RISE = errors.New("ERROR:极夜，金星今日永远在地平线下！")
	ERR_VENUS_NEVER_SET  = errors.New("ERROR:极昼，金星今日永远在地平线上！")
	// ERR_VENUS_NEVER_DOWN deprecated: -- use ERR_VENUS_NEVER_SET instead
	ERR_VENUS_NEVER_DOWN = ERR_VENUS_NEVER_SET
)

func riseSetResult(date time.Time, jde float64, err error) (time.Time, error) {
	if err != nil {
		switch {
		case errors.Is(err, basic.ErrNeverRise):
			return time.Time{}, ERR_VENUS_NEVER_RISE
		case errors.Is(err, basic.ErrNeverSet):
			return time.Time{}, ERR_VENUS_NEVER_SET
		default:
			return time.Time{}, err
		}
	}
	return basic.JDE2DateByZone(jde, date.Location(), true), nil
}

// ApparentLo 视黄经 / apparent ecliptic longitude.
//
// 返回金星在 date 对应绝对时刻的瞬时视黄经，单位度。
// Returns the apparent ecliptic longitude of Venus at the instant represented by date, in degrees.
func ApparentLo(date time.Time) float64 {
	jde := calendar.Date2JDE(date.UTC())
	return basic.VenusApparentLo(basic.TD2UT(jde, true))
}

// ApparentBo 视黄纬 / apparent ecliptic latitude.
//
// 返回金星在 date 对应绝对时刻的瞬时视黄纬，单位度。
// Returns the apparent ecliptic latitude of Venus at the instant represented by date, in degrees.
func ApparentBo(date time.Time) float64 {
	jde := calendar.Date2JDE(date.UTC())
	return basic.VenusApparentBo(basic.TD2UT(jde, true))
}

// ApparentRa 视赤经 / apparent right ascension.
//
// 返回金星在 date 对应绝对时刻的瞬时视赤经，单位度。
// Returns the apparent right ascension of Venus at the instant represented by date, in degrees.
func ApparentRa(date time.Time) float64 {
	jde := calendar.Date2JDE(date.UTC())
	return basic.VenusApparentRa(basic.TD2UT(jde, true))
}

// ApparentDec 视赤纬 / apparent declination.
//
// 返回金星在 date 对应绝对时刻的瞬时视赤纬，单位度。
// Returns the apparent declination of Venus at the instant represented by date, in degrees.
func ApparentDec(date time.Time) float64 {
	jde := calendar.Date2JDE(date.UTC())
	return basic.VenusApparentDec(basic.TD2UT(jde, true))
}

// ApparentRaDec 视赤经、视赤纬 / apparent right ascension and declination.
//
// 返回金星在 date 对应绝对时刻的瞬时视赤经与视赤纬，单位度。
// Returns the apparent right ascension and declination of Venus at the instant represented by date, in degrees.
func ApparentRaDec(date time.Time) (float64, float64) {
	jde := calendar.Date2JDE(date.UTC())
	return basic.VenusApparentRaDec(basic.TD2UT(jde, true))
}

// ApparentMagnitude 视星等 / apparent magnitude.
//
// 返回金星在 date 对应绝对时刻的视星等。
// Returns the apparent visual magnitude of Venus at the instant represented by date.
func ApparentMagnitude(date time.Time) float64 {
	jde := calendar.Date2JDE(date.UTC())
	return basic.VenusMag(basic.TD2UT(jde, true))
}

// EarthDistance 地心距离 / Earth distance.
//
// 返回金星在 date 对应绝对时刻到地球的距离，单位 AU。
// Returns the distance from Venus to Earth at the instant represented by date, in astronomical units.
func EarthDistance(date time.Time) float64 {
	jde := calendar.Date2JDE(date.UTC())
	return basic.EarthVenusAway(basic.TD2UT(jde, true))
}

// SunDistance 日心距离 / Sun distance.
//
// 返回金星在 date 对应绝对时刻到太阳的距离，单位 AU。
// Returns the distance from Venus to the Sun at the instant represented by date, in astronomical units.
func SunDistance(date time.Time) float64 {
	jde := calendar.Date2JDE(date.UTC())
	return planet.WherePlanet(2, 2, basic.TD2UT(jde, true))
}

// Altitude 高度角 / altitude.
//
// date 表示观测时刻，会读取其时区参与地方时计算；lon 为观测者经度，东正西负；lat 为观测者纬度，北正南负。返回值单位度。
// date is the observing instant and its zone offset participates in local-time calculations. lon is east-positive longitude, lat is north-positive latitude, and the result is in degrees.
func Altitude(date time.Time, lon, lat float64) float64 {
	jde := basic.Date2JDE(date)
	_, loc := date.Zone()
	timezone := float64(loc) / 3600.0
	return basic.VenusHeight(jde, lon, lat, timezone)
}

// Zenith 天顶距 / zenith distance.
//
// 参数与 Altitude 相同，返回值为对应时刻的天顶距，单位度。
// Uses the same inputs as Altitude and returns the zenith distance in degrees.
func Zenith(date time.Time, lon, lat float64) float64 {
	return 90 - Altitude(date, lon, lat)
}

// Azimuth 方位角 / azimuth.
//
// date 表示观测时刻，会读取其时区参与地方时计算；lon 为观测者经度，东正西负；lat 为观测者纬度，北正南负。返回值按正北为 0°、向东增加。
// date is the observing instant and its zone offset participates in local-time calculations. lon is east-positive longitude, lat is north-positive latitude, and azimuth is measured from north toward east.
func Azimuth(date time.Time, lon, lat float64) float64 {
	jde := basic.Date2JDE(date)
	_, loc := date.Zone()
	timezone := float64(loc) / 3600.0
	return basic.VenusAzimuth(jde, lon, lat, timezone)
}

// HourAngle 时角 / hour angle.
//
// date 表示观测时刻，会读取其时区参与地方时计算；lon 为观测者经度，东正西负。返回值单位度。
// date is the observing instant and its zone offset participates in local-time calculations. lon is east-positive longitude and the returned hour angle is in degrees.
func HourAngle(date time.Time, lon float64) float64 {
	jde := basic.Date2JDE(date)
	_, loc := date.Zone()
	timezone := float64(loc) / 3600.0
	return basic.VenusHourAngle(jde, lon, timezone)
}

// CulminationTime 中天时刻 / culmination time.
//
// date 取其所在时区的当地日期，返回值保持相同时区；lon 为观测者经度，东正西负。
// date is interpreted on its local civil day and the result keeps the same time zone. lon is east-positive longitude.
func CulminationTime(date time.Time, lon float64) time.Time {
	if date.Hour() > 12 {
		date = date.Add(time.Hour * -12)
	}
	jde := basic.Date2JDE(date)
	_, loc := date.Zone()
	timezone := float64(loc) / 3600.0
	calcJde := basic.VenusCulminationTime(jde, lon, timezone) - timezone/24.00
	return basic.JDE2DateByZone(calcJde, date.Location(), false)
}

// RiseTime 升起时间 / rise time.
//
// date 取其所在时区的当地日期，返回值保持相同时区；lon 为东正西负经度，lat 为北正南负纬度；height 为观测点海拔高度（米）；aero 为 true 时加入标准大气折射。
// date is interpreted on its local civil day and the result keeps the same time zone. lon is east-positive longitude, lat is north-positive latitude, height is observer elevation in meters, and aero enables standard atmospheric refraction.
func RiseTime(date time.Time, lon, lat, height float64, aero bool) (time.Time, error) {
	var aeroFloat float64
	if aero {
		aeroFloat = 1
	}
	if date.Hour() > 12 {
		date = date.Add(time.Hour * -12)
	}
	jde := basic.Date2JDE(date)
	_, loc := date.Zone()
	timezone := float64(loc) / 3600.0
	riseJde, err := basic.VenusRiseTime(jde, lon, lat, timezone, aeroFloat, height)
	return riseSetResult(date, riseJde, err)
}

// DownTime 落下时间别名 / deprecated set-time alias.
//
// Deprecated: use SetTime instead.
//
// 参数与 SetTime 相同，仅为兼容旧接口保留。
// Same as SetTime and kept only for backward compatibility.
func DownTime(date time.Time, lon, lat, height float64, aero bool) (time.Time, error) {
	return SetTime(date, lon, lat, height, aero)
}

// SetTime 落下时间 / set time.
//
// 参数与 RiseTime 相同，返回给定当地日期内的落下时刻。
// Uses the same inputs as RiseTime and returns the set time on the corresponding local civil day.
func SetTime(date time.Time, lon, lat, height float64, aero bool) (time.Time, error) {
	var aeroFloat float64
	if aero {
		aeroFloat = 1
	}
	if date.Hour() > 12 {
		date = date.Add(time.Hour * -12)
	}
	jde := basic.Date2JDE(date)
	_, loc := date.Zone()
	timezone := float64(loc) / 3600.0
	riseJde, err := basic.VenusSetTime(jde, lon, lat, timezone, aeroFloat, height)
	return riseSetResult(date, riseJde, err)
}

// LastConjunction 上一次合日 / previous conjunction with the Sun.
//
// 返回 date 之前最近一次与太阳的合日时刻，结果保持 date 的时区。
// Returns the most recent conjunction with the Sun relative to date, keeping date's time zone.
func LastConjunction(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.LastVenusConjunction(jde), date.Location(), false)
}

// NextConjunction 下一次合日 / next conjunction with the Sun.
//
// 返回 date 之后最近一次与太阳的合日时刻，结果保持 date 的时区。
// Returns the next conjunction with the Sun relative to date, keeping date's time zone.
func NextConjunction(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.NextVenusConjunction(jde), date.Location(), false)
}

// LastInferiorConjunction 上一次下合 / previous inferior conjunction.
//
// 返回 date 之前最近一次下合时刻，结果保持 date 的时区。
// Returns the most recent inferior conjunction relative to date, keeping date's time zone.
func LastInferiorConjunction(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.LastVenusInferiorConjunction(jde), date.Location(), false)
}

// NextInferiorConjunction 下一次下合 / next inferior conjunction.
//
// 返回 date 之后最近一次下合时刻，结果保持 date 的时区。
// Returns the next inferior conjunction relative to date, keeping date's time zone.
func NextInferiorConjunction(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.NextVenusInferiorConjunction(jde), date.Location(), false)
}

// LastSuperiorConjunction 上一次上合 / previous superior conjunction.
//
// 返回 date 之前最近一次上合时刻，结果保持 date 的时区。
// Returns the most recent superior conjunction relative to date, keeping date's time zone.
func LastSuperiorConjunction(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.LastVenusSuperiorConjunction(jde), date.Location(), false)
}

// NextSuperiorConjunction 下一次上合 / next superior conjunction.
//
// 返回 date 之后最近一次上合时刻，结果保持 date 的时区。
// Returns the next superior conjunction relative to date, keeping date's time zone.
func NextSuperiorConjunction(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.NextVenusSuperiorConjunction(jde), date.Location(), false)
}

// LastRetrograde 上一次留 / previous stationary point.
//
// 返回 date 之前最近一次留时刻，不区分顺转逆还是逆转顺，结果保持 date 的时区。
// Returns the most recent stationary point relative to date without distinguishing direction, keeping date's time zone.
func LastRetrograde(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.LastVenusRetrograde(jde), date.Location(), false)
}

// NextRetrograde 下一次留 / next stationary point.
//
// 返回 date 之后最近一次留时刻，不区分顺转逆还是逆转顺，结果保持 date 的时区。
// Returns the next stationary point relative to date without distinguishing direction, keeping date's time zone.
func NextRetrograde(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.NextVenusRetrograde(jde), date.Location(), false)
}

// LastProgradeToRetrograde 上一次顺行转逆行留 / previous station from prograde to retrograde.
//
// 返回 date 之前最近一次由顺行转为逆行的留时刻，结果保持 date 的时区。
// Returns the most recent stationary point where motion changes from prograde to retrograde relative to date, keeping date's time zone.
func LastProgradeToRetrograde(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.LastVenusProgradeToRetrograde(jde), date.Location(), false)
}

// NextProgradeToRetrograde 下一次顺行转逆行留 / next station from prograde to retrograde.
//
// 返回 date 之后最近一次由顺行转为逆行的留时刻，结果保持 date 的时区。
// Returns the next stationary point where motion changes from prograde to retrograde relative to date, keeping date's time zone.
func NextProgradeToRetrograde(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.NextVenusProgradeToRetrograde(jde), date.Location(), false)
}

// LastRetrogradeToPrograde 上一次逆行转顺行留 / previous station from retrograde to prograde.
//
// 返回 date 之前最近一次由逆行转为顺行的留时刻，结果保持 date 的时区。
// Returns the most recent stationary point where motion changes from retrograde to prograde relative to date, keeping date's time zone.
func LastRetrogradeToPrograde(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.LastVenusRetrogradeToPrograde(jde), date.Location(), false)
}

// NextRetrogradeToPrograde 下一次逆行转顺行留 / next station from retrograde to prograde.
//
// 返回 date 之后最近一次由逆行转为顺行的留时刻，结果保持 date 的时区。
// Returns the next stationary point where motion changes from retrograde to prograde relative to date, keeping date's time zone.
func NextRetrogradeToPrograde(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.NextVenusRetrogradeToPrograde(jde), date.Location(), false)
}

// LastGreatestElongation 上一次大距 / previous greatest elongation.
//
// 返回 date 之前最近一次大距时刻，不区分东西大距，结果保持 date 的时区。
// Returns the most recent greatest elongation relative to date without distinguishing east or west, keeping date's time zone.
func LastGreatestElongation(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.LastVenusGreatestElongation(jde), date.Location(), false)
}

// NextGreatestElongation 下一次大距 / next greatest elongation.
//
// 返回 date 之后最近一次大距时刻，不区分东西大距，结果保持 date 的时区。
// Returns the next greatest elongation relative to date without distinguishing east or west, keeping date's time zone.
func NextGreatestElongation(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.NextVenusGreatestElongation(jde), date.Location(), false)
}

// LastGreatestElongationEast 上一次东大距 / previous greatest eastern elongation.
//
// 返回 date 之前最近一次东大距时刻，结果保持 date 的时区。
// Returns the most recent greatest eastern elongation relative to date, keeping date's time zone.
func LastGreatestElongationEast(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.LastVenusGreatestElongationEast(jde), date.Location(), false)
}

// NextGreatestElongationEast 下一次东大距 / next greatest eastern elongation.
//
// 返回 date 之后最近一次东大距时刻，结果保持 date 的时区。
// Returns the next greatest eastern elongation relative to date, keeping date's time zone.
func NextGreatestElongationEast(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.NextVenusGreatestElongationEast(jde), date.Location(), false)
}

// LastGreatestElongationWest 上一次西大距 / previous greatest western elongation.
//
// 返回 date 之前最近一次西大距时刻，结果保持 date 的时区。
// Returns the most recent greatest western elongation relative to date, keeping date's time zone.
func LastGreatestElongationWest(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.LastVenusGreatestElongationWest(jde), date.Location(), false)
}

// NextGreatestElongationWest 下一次西大距 / next greatest western elongation.
//
// 返回 date 之后最近一次西大距时刻，结果保持 date 的时区。
// Returns the next greatest western elongation relative to date, keeping date's time zone.
func NextGreatestElongationWest(date time.Time) time.Time {
	jde := basic.TD2UT(basic.Date2JDE(date.UTC()), true)
	return basic.JDE2DateByZone(basic.NextVenusGreatestElongationWest(jde), date.Location(), false)
}