package natal

import (
	"strings"
	"unicode/utf8"
)

// City is a built-in birth place with WGS84 coordinates.
type City struct {
	Name string
	Lat  float64
	Lng  float64
}

// Cities lists common CN cities for MVP geocode (no network).
var Cities = []City{
	{"北京", 39.9042, 116.4074},
	{"上海", 31.2304, 121.4737},
	{"广州", 23.1291, 113.2644},
	{"深圳", 22.5431, 114.0579},
	{"杭州", 30.2741, 120.1551},
	{"成都", 30.5728, 104.0668},
	{"重庆", 29.5630, 106.5516},
	{"武汉", 30.5928, 114.3055},
	{"西安", 34.3416, 108.9398},
	{"南京", 32.0603, 118.7969},
	{"天津", 39.3434, 117.3616},
	{"苏州", 31.2989, 120.5853},
	{"长沙", 28.2282, 112.9388},
	{"郑州", 34.7466, 113.6254},
	{"青岛", 36.0671, 120.3826},
	{"大连", 38.9140, 121.6147},
	{"厦门", 24.4798, 118.0894},
	{"福州", 26.0745, 119.2965},
	{"昆明", 25.0389, 102.7183},
	{"贵阳", 26.6470, 106.6302},
	{"南宁", 22.8170, 108.3665},
	{"海口", 20.0440, 110.1999},
	{"哈尔滨", 45.8038, 126.5349},
	{"长春", 43.8171, 125.3235},
	{"沈阳", 41.8057, 123.4315},
	{"石家庄", 38.0428, 114.5149},
	{"太原", 37.8706, 112.5489},
	{"济南", 36.6512, 117.1201},
	{"合肥", 31.8206, 117.2272},
	{"南昌", 28.6820, 115.8579},
	{"兰州", 36.0611, 103.8343},
	{"乌鲁木齐", 43.8256, 87.6168},
	{"拉萨", 29.6520, 91.1721},
	{"呼和浩特", 40.8414, 111.7519},
	{"银川", 38.4872, 106.2309},
	{"西宁", 36.6171, 101.7782},
	{"香港", 22.3193, 114.1694},
	{"澳门", 22.1987, 113.5439},
	{"台北", 25.0330, 121.5654},
	{"宁波", 29.8683, 121.5440},
	{"无锡", 31.4912, 120.3119},
	{"佛山", 23.0215, 113.1214},
	{"东莞", 23.0207, 113.7518},
	{"温州", 27.9943, 120.6994},
	{"泉州", 24.8741, 118.6759},
	{"珠海", 22.2710, 113.5767},
}

// DefaultCoords is used when place is missing (东八区中部近似).
const DefaultLat = 30.0
const DefaultLng = 114.0

// ResolvePlace returns lat/lng and whether a named city matched.
// Accepts plain city ("杭州") or 省市区 ("浙江省 杭州市 西湖区" / "北京市 市辖区 朝阳区").
func ResolvePlace(place string) (lat, lng float64, matched string, ok bool) {
	place = strings.TrimSpace(place)
	if place == "" {
		return DefaultLat, DefaultLng, "", false
	}
	// exact city table hit
	for _, c := range Cities {
		if c.Name == place {
			return c.Lat, c.Lng, c.Name, true
		}
	}
	tokens := splitPlace(place)
	// prefer matching city-level tokens (usually 2nd), then others
	order := append([]string{}, tokens...)
	if len(tokens) >= 2 {
		order = append([]string{tokens[1]}, tokens[0])
		if len(tokens) >= 3 {
			order = append(order, tokens[2:]...)
		}
	}
	for _, tok := range order {
		if tok == "" || tok == "市辖区" || tok == "县" {
			continue
		}
		key := normalizeAdmin(tok)
		for _, c := range Cities {
			if c.Name == key || strings.Contains(tok, c.Name) || strings.Contains(c.Name, key) {
				return c.Lat, c.Lng, c.Name, true
			}
		}
	}
	// province-only fallback: use first token city if 直辖市
	if len(tokens) > 0 {
		key := normalizeAdmin(tokens[0])
		for _, c := range Cities {
			if c.Name == key {
				return c.Lat, c.Lng, c.Name, true
			}
		}
	}
	return DefaultLat, DefaultLng, "", false
}

func splitPlace(s string) []string {
	s = strings.ReplaceAll(s, "/", " ")
	s = strings.ReplaceAll(s, "／", " ")
	s = strings.ReplaceAll(s, "，", " ")
	s = strings.ReplaceAll(s, ",", " ")
	parts := strings.Fields(s)
	out := make([]string, 0, len(parts))
	for _, p := range parts {
		p = strings.TrimSpace(p)
		if p != "" {
			out = append(out, p)
		}
	}
	return out
}

func normalizeAdmin(s string) string {
	s = strings.TrimSpace(s)
	suffixes := []string{"特别行政区", "维吾尔自治区", "壮族自治区", "回族自治区", "自治区", "省", "市", "地区", "盟"}
	for _, suf := range suffixes {
		if strings.HasSuffix(s, suf) && utf8.RuneCountInString(s) > utf8.RuneCountInString(suf) {
			return strings.TrimSuffix(s, suf)
		}
	}
	return s
}

// CityNames returns names for API/UI pickers.
func CityNames() []string {
	out := make([]string, len(Cities))
	for i, c := range Cities {
		out[i] = c.Name
	}
	return out
}