package service

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

const wechatAPIBase = "https://api.weixin.qq.com"

// WechatTemplateKey 风险等级 → 订阅消息场景键（green 不推送）
func WechatTemplateKey(level string) string {
	switch level {
	case "yellow", "orange", "red":
		return "inspection"
	default:
		return ""
	}
}

// IsAuthorized 判断授权模板列表是否包含场景键
func IsAuthorized(authorized []string, key string) bool {
	for _, k := range authorized {
		if k == key {
			return true
		}
	}
	return false
}

// levelZh 风险等级中文
func levelZh(level string) string {
	switch level {
	case "green":
		return "绿"
	case "yellow":
		return "黄"
	case "orange":
		return "橙"
	case "red":
		return "红"
	default:
		return level
	}
}

// BuildSubscribeData 构造订阅消息 data（thing1=风险等级 thing2=评分；字段名需与微信模板字段一致）
func BuildSubscribeData(level string, score float64) map[string]map[string]string {
	return map[string]map[string]string{
		"thing1": {"value": levelZh(level)},
		"thing2": {"value": fmt.Sprintf("%.0f分", score)},
	}
}

// WechatService 微信小程序订阅消息服务（骨架；未配置时 Configured()=false，调用返回明确错误）
type WechatService struct {
	appID       string
	secret      string
	baseURL     string
	accessToken string
	tokenExpire time.Time
	mu          sync.Mutex
	httpClient  *http.Client
}

// NewWechatService 创建微信服务
func NewWechatService(appID, secret string) *WechatService {
	return &WechatService{
		appID:      appID,
		secret:     secret,
		baseURL:    wechatAPIBase,
		httpClient: &http.Client{Timeout: 15 * time.Second},
	}
}

// Configured 是否已配置 AppID/Secret
func (s *WechatService) Configured() bool {
	return s.appID != "" && s.secret != ""
}

// Code2Session 用 wx.login 的 code 换取 openid
func (s *WechatService) Code2Session(ctx context.Context, code string) (string, error) {
	if !s.Configured() {
		return "", fmt.Errorf("微信未配置（WECHAT_APPID/WECHAT_SECRET）")
	}
	u := s.baseURL + "/sns/jscode2session?appid=" + url.QueryEscape(s.appID) +
		"&secret=" + url.QueryEscape(s.secret) +
		"&js_code=" + url.QueryEscape(code) + "&grant_type=authorization_code"
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
	if err != nil {
		return "", err
	}
	resp, err := s.httpClient.Do(req)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return "", err
	}
	var out struct {
		OpenID  string `json:"openid"`
		ErrCode int    `json:"errcode"`
		ErrMsg  string `json:"errmsg"`
	}
	if err := json.Unmarshal(body, &out); err != nil {
		return "", err
	}
	if out.ErrCode != 0 {
		return "", fmt.Errorf("微信 code2session 失败 (%d): %s", out.ErrCode, out.ErrMsg)
	}
	return out.OpenID, nil
}

// getAccessToken 获取并缓存 access_token（提前 60 秒过期）
func (s *WechatService) getAccessToken(ctx context.Context) (string, error) {
	s.mu.Lock()
	if s.accessToken != "" && time.Now().Before(s.tokenExpire) {
		tok := s.accessToken
		s.mu.Unlock()
		return tok, nil
	}
	s.mu.Unlock()

	if !s.Configured() {
		return "", fmt.Errorf("微信未配置（WECHAT_APPID/WECHAT_SECRET）")
	}
	u := s.baseURL + "/cgi-bin/token?grant_type=client_credential&appid=" +
		url.QueryEscape(s.appID) + "&secret=" + url.QueryEscape(s.secret)
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
	if err != nil {
		return "", err
	}
	resp, err := s.httpClient.Do(req)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return "", err
	}
	var out struct {
		AccessToken string `json:"access_token"`
		ExpiresIn   int    `json:"expires_in"`
		ErrCode     int    `json:"errcode"`
		ErrMsg      string `json:"errmsg"`
	}
	if err := json.Unmarshal(body, &out); err != nil {
		return "", err
	}
	if out.AccessToken == "" {
		return "", fmt.Errorf("微信 access_token 获取失败 (%d): %s", out.ErrCode, out.ErrMsg)
	}
	s.mu.Lock()
	s.accessToken = out.AccessToken
	s.tokenExpire = time.Now().Add(time.Duration(out.ExpiresIn-60) * time.Second)
	s.mu.Unlock()
	return out.AccessToken, nil
}

// SendSubscribe 发送订阅消息
func (s *WechatService) SendSubscribe(ctx context.Context, openid, templateID string, data map[string]map[string]string, page string) error {
	token, err := s.getAccessToken(ctx)
	if err != nil {
		return err
	}
	payload := map[string]any{
		"touser":      openid,
		"template_id": templateID,
		"data":        data,
	}
	if page != "" {
		payload["page"] = page
	}
	raw, err := json.Marshal(payload)
	if err != nil {
		return err
	}
	u := s.baseURL + "/cgi-bin/message/subscribe/send?access_token=" + url.QueryEscape(token)
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, u, bytes.NewReader(raw))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")
	resp, err := s.httpClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return err
	}
	var out struct {
		ErrCode int    `json:"errcode"`
		ErrMsg  string `json:"errmsg"`
	}
	if err := json.Unmarshal(body, &out); err != nil {
		return err
	}
	if out.ErrCode != 0 {
		return fmt.Errorf("微信订阅消息发送失败 (%d): %s", out.ErrCode, out.ErrMsg)
	}
	return nil
}