package dailygeo

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strings"
	"time"
)

type Address struct{ Province, City, Region, Adcode string }
type Resolver interface {
	Resolve(context.Context, float64, float64) (Address, error)
}
type AMap struct {
	Key, BaseURL string
	Client       *http.Client
}

func (a *AMap) Resolve(ctx context.Context, lng, lat float64) (Address, error) {
	if a.Key == "" {
		return Address{}, fmt.Errorf("AMAP_API_KEY is not configured")
	}
	base := a.BaseURL
	if base == "" {
		base = "https://restapi.amap.com"
	}
	u, e := url.Parse(base + "/v3/geocode/regeo")
	if e != nil {
		return Address{}, fmt.Errorf("invalid geocoder URL")
	}
	x, y := WGS84ToGCJ02(lng, lat)
	q := u.Query()
	q.Set("key", a.Key)
	q.Set("location", fmt.Sprintf("%.6f,%.6f", x, y))
	q.Set("extensions", "base")
	q.Set("radius", "1000")
	u.RawQuery = q.Encode()
	req, e := http.NewRequestWithContext(ctx, http.MethodGet, u.String(), nil)
	if e != nil {
		return Address{}, fmt.Errorf("invalid geocoder request")
	}
	client := a.Client
	if client == nil {
		client = &http.Client{Timeout: 10 * time.Second}
	}
	resp, e := client.Do(req)
	if e != nil {
		return Address{}, fmt.Errorf("geocoder request failed")
	}
	defer resp.Body.Close()
	if resp.StatusCode != 200 {
		return Address{}, fmt.Errorf("geocoder HTTP %d", resp.StatusCode)
	}
	var body struct {
		Status    string
		Infocode  string
		Regeocode struct {
			AddressComponent struct{ Province, City, District, Adcode json.RawMessage } `json:"addressComponent"`
		}
	}
	if e = json.NewDecoder(io.LimitReader(resp.Body, 1<<20)).Decode(&body); e != nil {
		return Address{}, fmt.Errorf("invalid geocoder response")
	}
	if body.Status != "1" {
		return Address{}, fmt.Errorf("geocoder rejected: %s", body.Infocode)
	}
	p, c := textValue(body.Regeocode.AddressComponent.Province), textValue(body.Regeocode.AddressComponent.City)
	if c == "" {
		switch p {
		case "北京市", "上海市", "天津市", "重庆市", "香港特别行政区", "澳门特别行政区":
			c = p
		}
	}
	// Province-administered county-level cities (for example 潜江市) are
	// returned in district, with city=[], by AMap.
	if c == "" && p != "" {
		district := textValue(body.Regeocode.AddressComponent.District)
		if strings.HasSuffix(district, "市") {
			c = district
		}
	}
	if p == "" || c == "" {
		return Address{}, fmt.Errorf("geocoder returned incomplete province/city")
	}
	return Address{p, c, Region(p), textValue(body.Regeocode.AddressComponent.Adcode)}, nil
}
func textValue(raw json.RawMessage) string {
	var s string
	if json.Unmarshal(raw, &s) == nil {
		return s
	}
	var ss []string
	if json.Unmarshal(raw, &ss) == nil {
		return strings.Join(ss, "")
	}
	return ""
}
func Region(province string) string {
	groups := []struct {
		name      string
		provinces []string
	}{
		{"华东", []string{"上海", "江苏", "浙江", "安徽", "福建", "江西", "山东", "台湾"}},
		{"华北", []string{"北京", "天津", "河北", "山西", "内蒙古"}},
		{"华中", []string{"河南", "湖北", "湖南"}},
		{"华南", []string{"广东", "广西", "海南", "香港", "澳门"}},
		{"东北", []string{"辽宁", "吉林", "黑龙江"}},
		{"西南", []string{"重庆", "四川", "贵州", "云南", "西藏"}},
		{"西北", []string{"陕西", "甘肃", "青海", "宁夏", "新疆"}},
	}
	for _, g := range groups {
		for _, p := range g.provinces {
			if strings.HasPrefix(province, p) {
				return g.name
			}
		}
	}
	return ""
}