package controllers

import (
	"bytes"
	"encoding/json"
	"io"
	"net/http"
	"strconv"
	"strings"
	"time"

	beego "github.com/beego/beego/v2/server/web"
)

// BackendWeatherController 天气实时数据代理。
//
// 数据源：中国天气网 d1.weather.com.cn（国内真实数据）。
// 该接口有防盗链，浏览器直连会被 Referer 校验拦掉、也会跨域，
// 因此由服务端带 Referer 抓取后统一返回 JSON。
type BackendWeatherController struct {
	beego.Controller
}

// 常用城市编码（中国天气网 citycode），未命中时按入参 code 直取
var weatherCityCodes = map[string]string{
	"连云港": "101191001",
	"南京":  "101190101",
	"苏州":  "101190401",
	"无锡":  "101190201",
	"常州":  "101191101",
	"南通":  "101190501",
	"扬州":  "101190601",
	"徐州":  "101190801",
	"盐城":  "101190701",
	"淮安":  "101190901",
	"镇江":  "101190301",
	"泰州":  "101191201",
	"宿迁":  "101191301",
	"北京":  "101010100",
	"上海":  "101020100",
	"广州":  "101280101",
	"深圳":  "101280601",
	"杭州":  "101210101",
}

const defaultWeatherCity = "连云港"

// Now GET /backend/weather/now?city=连云港 或 ?code=101191201
func (c *BackendWeatherController) Now() {
	city := strings.TrimSpace(c.GetString("city"))
	code := strings.TrimSpace(c.GetString("code"))
	if code == "" {
		code = weatherCityCodes[city]
	}
	if code == "" {
		code = weatherCityCodes[defaultWeatherCity]
		city = defaultWeatherCity
	}

	client := &http.Client{Timeout: 8 * time.Second}
	ts := strconv.FormatInt(time.Now().UnixMilli(), 10)
	referer := "https://www.weather.com.cn/weather1d/" + code + ".shtml"

	// 主数据源：dingzhi（含天气现象 + 气温）。中国天气网已拒绝 http 明文连接，必须走 https。
	info := weatherFetchJSON(client, "https://d1.weather.com.cn/dingzhi/"+code+".html?_="+ts, referer)
	if wi, ok := info["weatherinfo"].(map[string]interface{}); ok {
		info = wi
	}
	// 兜底：sk_2d（实况气温，无天气现象）
	if len(info) == 0 {
		info = weatherFetchJSON(client, "https://d1.weather.com.cn/sk_2d/"+code+".html?_="+ts, referer)
	}

	if len(info) == 0 {
		c.Ctx.Output.SetStatus(http.StatusBadGateway)
		c.Data["json"] = map[string]interface{}{"code": 502, "msg": "天气数据获取失败，请稍后重试"}
		_ = c.ServeJSON()
		return
	}

	cityName := weatherStr(info, "cityname", "city", "name")
	if cityName == "" {
		cityName = city
	}
	temp := strings.TrimSuffix(weatherStr(info, "temp", "real"), "℃")
	text := weatherStr(info, "weather", "weather1")

	c.Data["json"] = map[string]interface{}{
		"code": 200,
		"msg":  "ok",
		"data": map[string]interface{}{
			"city":   cityName,
			"temp":   temp,
			"text":   text,
			"update": weatherStr(info, "time", "fctime", "date"),
			"code":   code,
		},
	}
	_ = c.ServeJSON()
}

// weatherFetchJSON 带 Referer/UA 抓取中国天气网页面并解析其中的 JSON 对象
func weatherFetchJSON(client *http.Client, url, referer string) map[string]interface{} {
	req, err := http.NewRequest(http.MethodGet, url, nil)
	if err != nil {
		return nil
	}
	req.Header.Set("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36")
	req.Header.Set("Referer", referer)
	req.Header.Set("Accept", "*/*")

	resp, err := client.Do(req)
	if err != nil {
		return nil
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	if err != nil {
		return nil
	}

	// 返回体形如：var cityDZ101191001 ={"weatherinfo":{...}};var alarmDZ101191001 ={"w":[]}
	// 从第一个 '{' 起用 json.Decoder 只解出第一个完整对象（正则贪婪匹配会跨越多个对象导致解析失败）
	idx := bytes.IndexByte(body, '{')
	if idx < 0 {
		return nil
	}
	var out map[string]interface{}
	if json.NewDecoder(bytes.NewReader(body[idx:])).Decode(&out) != nil {
		return nil
	}
	return out
}

// weatherStr 按候选字段顺序取第一个非空字符串值
func weatherStr(m map[string]interface{}, keys ...string) string {
	for _, k := range keys {
		if v, ok := m[k]; ok {
			if s, ok := v.(string); ok && strings.TrimSpace(s) != "" {
				return strings.TrimSpace(s)
			}
		}
	}
	return ""
}