"use client";

import { useEffect, useRef } from "react";
import { usePathname } from "next/navigation";
import { apiGetSettings } from "@/lib/api";
import { applyAccentTheme } from "@/lib/theme";
import {
  applySiteBackground,
  bgConfigFromSettings,
  type SiteBgConfig,
  type SiteBgInput,
} from "@/lib/bg";
import { realtime, RT_SETTINGS_CHANGED, type RtSettingsData } from "@/lib/realtime";
import {
  VISIBLE_RECONCILE_GAP_MS,
  onDocumentVisible,
} from "@/lib/visibilityReconcile";

// 站点主题色 / 背景图同步器：
// 管理员保存后，其他已打开标签页不会因软导航重跑根布局 SSR。
// WS 推送 + 标签页重新可见时探测公开设置，热替换 accent 与背景。
const MIN_FETCH_GAP_MS = VISIBLE_RECONCILE_GAP_MS;

export default function ThemeSync({
  initialAccent,
  initialBg,
}: {
  initialAccent: string;
  initialBg: SiteBgConfig;
}) {
  const pathname = usePathname();
  const currentRef = useRef((initialAccent || "").trim().toLowerCase());
  const bgRef = useRef(initialBg);
  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 applyBg = (raw: SiteBgInput) => {
      if (cancelled) return;
      const next = bgConfigFromSettings(raw);
      bgRef.current = next;
      applySiteBackground(next);
    };

    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 s = await apiGetSettings();
        if (cancelled) return;
        applyAccent((s.accent || "").trim().toLowerCase());
        applyBg(s);
      } 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());
      applyBg(data);
    });

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

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

  return null;
}