package handler

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"io"
	"log"
	"net/http"
	"strings"
	"sync"
	"time"

	"github.com/gin-gonic/gin"

	"github.com/sundynix/sundynix-gateway/internal/wechat"
)

// 微信公众号「带参数二维码 + 关注/扫码事件」登录。设计见 internal/wechat/mp.go。
//
// 端点：
//   POST /api/v1/wx/mp/ticket    建 login ticket + 微信二维码，返回二维码图 URL
//   GET  /wx/mp/callback         服务器配置 URL 验证（echostr）
//   POST /wx/mp/callback         事件推送：关注/扫码 → 置 ticket 已授权
//   GET  /api/v1/wx/mp/poll?t=   PC 轮询登录态，已授权则签发 JWT

const (
	SettingWechatMP = "wechat_mp"     // 公众号登录配置（setting 表）
	wxTicketTTL     = 5 * time.Minute // 二维码/ticket 有效期
)

// access_token 拉取的进程内串行化：单实例下杜绝并发拉取互相失效（多实例靠 Redis 缓存兜大头）。
var wxTokenMu sync.Mutex

type wxTicketState struct {
	Status string `json:"status"` // pending / authorized / consumed
	UserID string `json:"user_id"`
}

func (h *Handler) loadWechatMP(ctx context.Context) wechat.Config {
	raw := h.db.GetSetting(ctx, SettingWechatMP)
	if raw == "" {
		return wechat.Config{}
	}
	var c wechat.Config
	if json.Unmarshal([]byte(raw), &c) != nil {
		return wechat.Config{}
	}
	return c.DecryptFromStore()
}

// accessToken 取（缓存优先）微信 access_token。
func (h *Handler) accessToken(ctx context.Context, cfg wechat.Config) (string, error) {
	if t := h.cache.WxTokenGet(ctx, cfg.AppID); t != "" {
		return t, nil
	}
	wxTokenMu.Lock()
	defer wxTokenMu.Unlock()
	if t := h.cache.WxTokenGet(ctx, cfg.AppID); t != "" { // 双检
		return t, nil
	}
	token, ttl, err := cfg.FetchAccessToken(ctx)
	if err != nil {
		return "", err
	}
	if ttl > 200 {
		ttl -= 200 // 安全边界，避免临界过期
	}
	h.cache.WxTokenSet(ctx, cfg.AppID, token, time.Duration(ttl)*time.Second)
	return token, nil
}

func newTicket() string {
	b := make([]byte, 16)
	_, _ = rand.Read(b)
	return hex.EncodeToString(b)
}

// WxMPTicket: POST /api/v1/wx/mp/ticket
func (h *Handler) WxMPTicket(c *gin.Context) {
	ctx := c.Request.Context()
	cfg := h.loadWechatMP(ctx)
	if !cfg.Enabled() {
		c.JSON(http.StatusServiceUnavailable, gin.H{"error": "微信登录未配置"})
		return
	}
	token, err := h.accessToken(ctx, cfg)
	if err != nil {
		log.Printf("[wxlogin] 取 access_token 失败: %v", err)
		c.JSON(http.StatusBadGateway, gin.H{"error": "微信登录暂不可用"})
		return
	}
	ticket := newTicket()
	qrURL, err := cfg.CreateLoginQR(ctx, token, ticket, int(wxTicketTTL.Seconds()))
	if err != nil {
		log.Printf("[wxlogin] 建二维码失败: %v", err)
		c.JSON(http.StatusBadGateway, gin.H{"error": "生成二维码失败"})
		return
	}
	st, _ := json.Marshal(wxTicketState{Status: "pending"})
	if err := h.cache.WxTicketSet(ctx, ticket, string(st), wxTicketTTL); err != nil {
		c.JSON(http.StatusBadGateway, gin.H{"error": "创建登录票据失败"})
		return
	}
	c.JSON(http.StatusOK, gin.H{"ticket": ticket, "qr_image": qrURL, "expires_in": int(wxTicketTTL.Seconds())})
}

// WxMPVerify: GET /wx/mp/callback —— 服务器配置 URL 验证。
func (h *Handler) WxMPVerify(c *gin.Context) {
	cfg := h.loadWechatMP(c.Request.Context())
	if cfg.Token == "" || !cfg.CheckSignature(c.Query("signature"), c.Query("timestamp"), c.Query("nonce")) {
		c.String(http.StatusForbidden, "signature check failed")
		return
	}
	c.String(http.StatusOK, c.Query("echostr"))
}

// WxMPEvent: POST /wx/mp/callback —— 事件推送。
// 无论如何回 "success"（微信要求），否则会重试并给用户端弹"公众号服务故障"。
func (h *Handler) WxMPEvent(c *gin.Context) {
	ctx := c.Request.Context()
	cfg := h.loadWechatMP(ctx)
	// 验签：拒绝伪造事件（否则任何人 POST 一个 openid 就能登录别人）
	if cfg.Token == "" || !cfg.CheckSignature(c.Query("signature"), c.Query("timestamp"), c.Query("nonce")) {
		c.String(http.StatusForbidden, "signature check failed")
		return
	}
	body, _ := io.ReadAll(c.Request.Body)
	ev, err := wechat.ParseEvent(body)
	if err != nil || !ev.IsLoginScan() {
		c.String(http.StatusOK, "success") // 非登录扫码事件忽略，照常回执
		return
	}

	ticket, openID := ev.Scene(), ev.FromUserName
	if h.cache.WxTicketGet(ctx, ticket) == "" { // ticket 必须仍有效
		c.String(http.StatusOK, "success")
		return
	}
	u, err := h.db.GetUserByWechatOpenID(ctx, openID)
	if err != nil {
		c.String(http.StatusOK, "success")
		return
	}
	if u == nil {
		u, err = h.db.CreateWechatUser(ctx, openID, "微信用户")
		if err != nil {
			log.Printf("[wxlogin] 建微信用户失败 openid=%s: %v", openID, err)
			c.String(http.StatusOK, "success")
			return
		}
		if _, e := h.db.EnsureDefaultTenant(ctx, u.ID, "我的空间"); e != nil {
			log.Printf("[wxlogin] 建默认租户失败 uid=%s: %v", u.ID, e)
		}
	}
	st, _ := json.Marshal(wxTicketState{Status: "authorized", UserID: u.ID})
	_ = h.cache.WxTicketSet(ctx, ticket, string(st), wxTicketTTL)
	c.String(http.StatusOK, "success")
}

// WxMPPoll: GET /api/v1/wx/mp/poll?t=<ticket>
func (h *Handler) WxMPPoll(c *gin.Context) {
	ticket := c.Query("t")
	if ticket == "" {
		c.JSON(http.StatusBadRequest, gin.H{"error": "缺少票据"})
		return
	}
	ctx := c.Request.Context()
	raw := h.cache.WxTicketGet(ctx, ticket)
	if raw == "" {
		c.JSON(http.StatusOK, gin.H{"status": "expired"})
		return
	}
	var st wxTicketState
	if json.Unmarshal([]byte(raw), &st) != nil {
		c.JSON(http.StatusOK, gin.H{"status": "expired"})
		return
	}
	if st.Status != "authorized" {
		c.JSON(http.StatusOK, gin.H{"status": st.Status})
		return
	}
	// 一次性消费：先置 consumed 再签发，避免同一 ticket 被轮询两次拿两个令牌
	consumed, _ := json.Marshal(wxTicketState{Status: "consumed", UserID: st.UserID})
	_ = h.cache.WxTicketSet(ctx, ticket, string(consumed), time.Minute)

	u, err := h.db.GetUserByID(ctx, st.UserID)
	if err != nil || u == nil {
		c.JSON(http.StatusOK, gin.H{"status": "expired"})
		return
	}
	issueToken(c, u)
}

// ---- 管理端配置 ----

func (h *Handler) AdminGetWechatMP(c *gin.Context) {
	cfg := h.loadWechatMP(c.Request.Context())
	c.JSON(http.StatusOK, gin.H{
		"appid":          cfg.AppID,
		"token":          cfg.Token,
		"has_app_secret": cfg.AppSecret != "",
		"enabled":        cfg.Enabled(),
	})
}

func (h *Handler) AdminSaveWechatMP(c *gin.Context) {
	var b struct {
		AppID     string `json:"appid"`
		AppSecret string `json:"app_secret"`
		Token     string `json:"token"`
	}
	if err := c.ShouldBindJSON(&b); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "参数错误"})
		return
	}
	ctx := c.Request.Context()
	secret := strings.TrimSpace(b.AppSecret)
	if secret == "" {
		secret = h.loadWechatMP(ctx).AppSecret
	}
	cfg := wechat.Config{AppID: strings.TrimSpace(b.AppID), AppSecret: secret, Token: strings.TrimSpace(b.Token)}
	stored, err := cfg.EncryptedForStore()
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "密钥加密失败: " + err.Error()})
		return
	}
	raw, _ := json.Marshal(stored)
	if err := h.db.SetSetting(ctx, SettingWechatMP, string(raw)); err != nil {
		c.JSON(http.StatusBadGateway, gin.H{"error": err.Error()})
		return
	}
	h.cache.WxTokenSet(ctx, cfg.AppID, "", time.Millisecond) // 换密钥→旧 token 作废
	c.JSON(http.StatusOK, gin.H{"status": "ok", "enabled": cfg.Enabled()})
}