"use client";

import { useEffect, useRef } from "react";
import { useSession, signOut } from "next-auth/react";
import { useVoteStore } from "@/lib/store";

/**
 * 把服务端 /api/me 的真相态同步进本地 vote store。
 *
 * - status === "authenticated" → 拉一次 /api/me,用 votedArtists 覆盖本地
 * - status === "unauthenticated" → 清本地(避免上一个用户的票残留给下一个登录者)
 * - 切换用户(uid 变化) → 重新拉一次
 *
 * 僵尸 session 兜底:NextAuth 用 JWT 策略,cookie 不会因 DB user 被删而失效。
 * 当 /api/me 返回 401(签名失效) 或 NOT_FOUND(DB 里 user 已不存在) 时,
 * 自动 signOut() 清 cookie —— 避免页面"假登录"假象(显示已登录但拉不到数据)。
 *
 * localStorage 仅作为本设备的缓存加速首屏渲染,服务端永远是唯一真相源。
 */
export function useSyncMe() {
  const { data, status } = useSession();
  const hydrateFromServer = useVoteStore((s) => s.hydrateFromServer);
  const reset = useVoteStore((s) => s.reset);
  const lastSyncedUidRef = useRef<string | null>(null);

  const sessionUser = data?.user as { id?: string } | undefined;
  const uid = sessionUser?.id ?? null;

  useEffect(() => {
    if (status === "loading") return;

    if (status === "unauthenticated") {
      if (lastSyncedUidRef.current !== null) {
        reset();
        lastSyncedUidRef.current = null;
      }
      return;
    }

    // authenticated
    if (!uid) return;
    if (lastSyncedUidRef.current === uid) return;

    let cancelled = false;
    const ctrl = new AbortController();
    const timer = setTimeout(() => ctrl.abort(), 8000);

    fetch("/api/me", {
      credentials: "include",
      signal: ctrl.signal,
    })
      .then(async (r) => {
        if (cancelled) return;
        const res = await r.json().catch(() => null);

        if (r.ok && res?.ok && Array.isArray(res.data?.votedArtists)) {
          hydrateFromServer(res.data.votedArtists as string[]);
          lastSyncedUidRef.current = uid;
          return;
        }

        // 僵尸 session:JWT 还有效,但 DB 里 user 已不存在(或鉴权失效)。
        // 直接登出清 cookie,UI 状态切换为未登录,避免"显示已登录但拉不到数据"。
        const code: string | undefined = res?.error?.code;
        if (r.status === 401 || code === "UNAUTHORIZED" || code === "NOT_FOUND") {
          signOut({ redirect: false });
          reset();
          lastSyncedUidRef.current = null;
        }
      })
      .catch(() => {
        // 网络失败容忍 —— 下次 status 变化或手动刷新会再试
      })
      .finally(() => clearTimeout(timer));

    return () => {
      cancelled = true;
      ctrl.abort();
      clearTimeout(timer);
    };
  }, [status, uid, hydrateFromServer, reset]);
}