"use client";

import { useEffect, useRef } from "react";
import { usePathname } from "next/navigation";
import { apiGetSettings } from "@/lib/api";
import { applyAccentTheme } from "@/lib/theme";
import { applyCustomCSS } from "@/lib/customCode";
import { realtime, RT_SETTINGS_CHANGED, type RtSettingsData } from "@/lib/realtime";
import {
  VISIBLE_RECONCILE_GAP_MS,
  onDocumentVisible,
} from "@/lib/visibilityReconcile";

// 站点外观同步器：
// 主题色 / 自定义 CSS 由管理员在后台修改后，其他用户已打开的标签页不会因软导航重新执行根布局
// SSR，本组件通过 WS 推送 + 标签页重新可见时探测公开设置，发现变化即热替换。
// 自定义 JS 只在整页加载时执行，不在此热替换（避免重复绑定）。
const MIN_FETCH_GAP_MS = VISIBLE_RECONCILE_GAP_MS;

export default function ThemeSync({
  initialAccent,
  initialCustomCSS,
}: {
  initialAccent: string;
  initialCustomCSS: string;
}) {
  const pathname = usePathname();
  const currentRef = useRef((initialAccent || "").trim().toLowerCase());
  const cssRef = useRef((initialCustomCSS || "").trim());
  const lastFetchAtRef = useRef(0);
  const inFlightRef = useRef(false);

  useEffect(() => {
    // 外观设置页存在未保存的本地实时预览，暂停同步避免覆盖草稿
    if (pathname?.startsWith("/admin/appearance")) return;

    let cancelled = false;

    const applyAccent = (next: string) => {
      if (cancelled || next === currentRef.current) return;
      currentRef.current = next;
      applyAccentTheme(next || null);
    };

    const applyCSS = (next: string) => {
      if (cancelled) return;
      const text = (next || "").trim();
      if (text === cssRef.current) return;
      cssRef.current = text;
      applyCustomCSS(text);
    };

    const sync = async () => {
      if (inFlightRef.current) return;
      const now = Date.now();
      if (now - lastFetchAtRef.current < MIN_FETCH_GAP_MS) return;
      lastFetchAtRef.current = now;
      inFlightRef.current = true;
      try {
        const settings = await apiGetSettings();
        if (cancelled) return;
        applyAccent((settings.accent || "").trim().toLowerCase());
        applyCSS(settings.custom_css || "");
      } catch {
        // 同步失败静默，下次回前台再试
      } finally {
        inFlightRef.current = false;
      }
    };

    const offPush = realtime.on<RtSettingsData>(RT_SETTINGS_CHANGED, (data) => {
      if (!data) return;
      applyAccent((data.accent || "").trim().toLowerCase());
      if (typeof data.custom_css === "string") applyCSS(data.custom_css);
    });

    const offVisible = onDocumentVisible(() => void sync(), MIN_FETCH_GAP_MS);
    void sync();

    return () => {
      cancelled = true;
      offPush();
      offVisible();
    };
  }, [pathname]);

  return null;
}