digital-psychology/apps/api/internal/star/natal/natal.go

// Package natal computes tropical whole-sign natal charts via Swiss Ephemeris.
package natal

import (
	"fmt"
	"math"
	"time"

	"github.com/yuxingu/digital-psychology/apps/api/internal/star/ephemeris"
)

// Body is a chart point.
type Body struct {
	Key      string  `json:"key"`
	Title    string  `json:"title"`
	Lon      float64 `json:"lon"`
	SignKey  string  `json:"sign_key"`
	Sign     string  `json:"sign"`
	Degree   float64 `json:"degree"` // 0–30 within sign
	House    int     `json:"house"`
	Element  string  `json:"element"`
	Modality string  `json:"modality"`
}

// House is a whole-sign house.
type House struct {
	Num  int    `json:"num"`
	Sign string `json:"sign"`
	Key  string `json:"sign_key"`
}

// Chart is a natal chart snapshot.
type Chart struct {
	Sun, Moon, Rise Body
	Planets         []Body
	Houses          []House
	Lat, Lng        float64
	PlaceLabel      string
	HasTime         bool
	HasPlace        bool
	Note            string
	// Instant is the UTC moment used for ephemeris (noon default when time missing).
	Instant time.Time `json:"-"`
}

type signMeta struct {
	Key, Label, Element, Modality string
}

var signs = []signMeta{
	{"aries", "白羊", "火", "开创"},
	{"taurus", "金牛", "土", "固定"},
	{"gemini", "双子", "风", "变动"},
	{"cancer", "巨蟹", "水", "开创"},
	{"leo", "狮子", "火", "固定"},
	{"virgo", "处女", "土", "变动"},
	{"libra", "天秤", "风", "开创"},
	{"scorpio", "天蝎", "水", "固定"},
	{"sagittarius", "射手", "火", "变动"},
	{"capricorn", "摩羯", "土", "开创"},
	{"aquarius", "水瓶", "风", "固定"},
	{"pisces", "双鱼", "水", "变动"},
}

var bodyTitles = map[string]string{
	"sun": "太阳", "moon": "月亮", "rise": "上升",
	"mercury": "水星", "venus": "金星", "mars": "火星",
	"jupiter": "木星", "saturn": "土星", "uranus": "天王星",
	"neptune": "海王星", "pluto": "冥王星",
}

// Compute builds a natal chart. birthTime is HH:MM local; place is city name.
func Compute(birthDate time.Time, birthTime *string, place *string) (Chart, error) {
	lat, lng := DefaultLat, DefaultLng
	placeLabel := "默认（未填出生地）"
	hasPlace := false
	if place != nil && *place != "" {
		if la, ln, name, ok := ResolvePlace(*place); ok {
			lat, lng, placeLabel, hasPlace = la, ln, name, true
		} else {
			placeLabel = *place + "（未匹配城市，用默认坐标）"
		}
	}

	h, mi := 12, 0 // noon default when time missing
	hasTime := false
	if birthTime != nil && *birthTime != "" {
		if hh, mm, ok := parseHM(*birthTime); ok {
			h, mi, hasTime = hh, mm, true
		}
	}

	// Treat civil time as UTC+8 for CN MVP (deterministic).
	loc := time.FixedZone("CST", 8*3600)
	local := time.Date(birthDate.Year(), birthDate.Month(), birthDate.Day(), h, mi, 0, 0, loc)
	utc := local.UTC()

	return ComputeAt(utc, lat, lng, placeLabel, hasTime, hasPlace)
}

// ComputeAt builds a chart for an exact UTC instant and coordinates.
func ComputeAt(utc time.Time, lat, lng float64, placeLabel string, hasTime, hasPlace bool) (Chart, error) {
	utc = utc.UTC()
	jd := ephemeris.JulianDayUT(utc)
	lons, err := ephemeris.AllPlanetLons(jd)
	if err != nil {
		return Chart{}, fmt.Errorf("ephemeris: %w", err)
	}
	asc, err := ephemeris.Ascendant(jd, lat, lng)
	if err != nil {
		return Chart{}, fmt.Errorf("ephemeris asc: %w", err)
	}

	ch := ChartFromLons(lons, asc, lat, lng, placeLabel, hasTime, hasPlace)
	ch.Instant = utc
	ch.Note = fmt.Sprintf("热带黄道 · 整宫制 · 星历 %s。", ephemeris.Backend())
	if !hasTime {
		ch.Note += " 未填出生时，上升与宫位按正午估算。"
	}
	if !hasPlace {
		ch.Note += " 填写出生地可提升上升准确度。"
	}
	return ch, nil
}

// ChartFromLons builds a whole-sign chart from body longitudes and ASC.
func ChartFromLons(lons map[string]float64, asc float64, lat, lng float64, placeLabel string, hasTime, hasPlace bool) Chart {
	ascSignIdx := signIndex(asc)
	mk := func(key string, lon float64) Body {
		title := bodyTitles[key]
		if title == "" {
			title = key
		}
		idx := signIndex(lon)
		s := signs[idx]
		house := wholeSignHouse(ascSignIdx, idx)
		return Body{
			Key: key, Title: title, Lon: norm360(lon),
			SignKey: s.Key, Sign: s.Label, Degree: math.Mod(norm360(lon), 30),
			House: house, Element: s.Element, Modality: s.Modality,
		}
	}

	sun := mk("sun", lons["sun"])
	moon := mk("moon", lons["moon"])
	rise := mk("rise", asc)

	planets := []Body{
		sun, moon, rise,
		mk("mercury", lons["mercury"]),
		mk("venus", lons["venus"]),
		mk("mars", lons["mars"]),
		mk("jupiter", lons["jupiter"]),
		mk("saturn", lons["saturn"]),
		mk("uranus", lons["uranus"]),
		mk("neptune", lons["neptune"]),
		mk("pluto", lons["pluto"]),
	}

	houses := make([]House, 12)
	for i := 0; i < 12; i++ {
		idx := (ascSignIdx + i) % 12
		houses[i] = House{Num: i + 1, Sign: signs[idx].Label, Key: signs[idx].Key}
	}

	return Chart{
		Sun: sun, Moon: moon, Rise: rise, Planets: planets, Houses: houses,
		Lat: lat, Lng: lng, PlaceLabel: placeLabel, HasTime: hasTime, HasPlace: hasPlace,
	}
}

// BodyLon returns longitude for a key, or 0.
func BodyLon(c Chart, key string) float64 {
	for _, p := range c.Planets {
		if p.Key == key {
			return p.Lon
		}
	}
	return 0
}

// SignMetaByKey returns label/element for a sign key.
func SignMetaByKey(key string) (label, element, modality string) {
	for _, s := range signs {
		if s.Key == key {
			return s.Label, s.Element, s.Modality
		}
	}
	return key, "", ""
}

// SignByIndex returns sign meta.
func SignByIndex(i int) (key, label, element, modality string) {
	s := signs[((i%12)+12)%12]
	return s.Key, s.Label, s.Element, s.Modality
}

func wholeSignHouse(ascIdx, bodyIdx int) int {
	return ((bodyIdx-ascIdx)%12+12)%12 + 1
}

func signIndex(lon float64) int {
	return int(math.Floor(norm360(lon)/30.0)) % 12
}

func parseHM(s string) (h, m int, ok bool) {
	var hh, mm int
	n, err := fmt.Sscanf(s, "%d:%d", &hh, &mm)
	if err != nil || n < 1 || hh < 0 || hh > 23 {
		return 0, 0, false
	}
	if n == 1 {
		mm = 0
	}
	if mm < 0 || mm > 59 {
		return 0, 0, false
	}
	return hh, mm, true
}

func norm360(x float64) float64 {
	x = math.Mod(x, 360)
	if x < 0 {
		x += 360
	}
	return x
}

// AngleDiff returns smallest absolute ecliptic separation.
func AngleDiff(a, b float64) float64 {
	d := math.Abs(norm360(a) - norm360(b))
	if d > 180 {
		d = 360 - d
	}
	return d
}

// MidpointLon returns the shorter-arc midpoint of two longitudes.
func MidpointLon(a, b float64) float64 {
	a, b = norm360(a), norm360(b)
	d := b - a
	if d > 180 {
		d -= 360
	} else if d < -180 {
		d += 360
	}
	return norm360(a + d/2)
}

// SignIndex is exported for overlay house mapping.
func SignIndex(lon float64) int { return signIndex(lon) }

// WholeSignHouse exported for overlay.
func WholeSignHouse(ascIdx, bodyIdx int) int { return wholeSignHouse(ascIdx, bodyIdx) }