"use client";

import { createContext, useContext, useEffect, useMemo, useRef, useState, type ReactNode } from "react";
import { apiGetSettings, type PublicSettings } from "@/lib/api";
import { siteDocumentTitle, normalizeBrandLogoFit, normalizeBrandLogoSize, normalizeBrandMark, normalizeFooterLinks } from "@/lib/brand";
import { normalizeUrlStyle, type UrlStyle } from "@/lib/urlStyle";
import { realtime, RT_SETTINGS_CHANGED, type RtSettingsData } from "@/lib/realtime";
import { onDocumentVisible, VISIBLE_RECONCILE_GAP_MS } from "@/lib/visibilityReconcile";

export type SiteBrand = {
  site_name: string;
  site_wordmark: string;
  site_slogan: string;
  logo_light_url: string;
  logo_dark_url: string;
  favicon_url: string;
  brand_mark: PublicSettings["brand_mark"];
  brand_logo_size: PublicSettings["brand_logo_size"];
  brand_logo_fit: PublicSettings["brand_logo_fit"];
  footer_links: PublicSettings["footer_links"];
  url_style: UrlStyle;
};

const SiteBrandContext = createContext<SiteBrand | null>(null);

function fromSettings(s: PublicSettings): SiteBrand {
  return {
    site_name: s.site_name,
    site_wordmark: s.site_wordmark,
    site_slogan: s.site_slogan,
    logo_light_url: s.logo_light_url,
    logo_dark_url: s.logo_dark_url,
    favicon_url: s.favicon_url,
    brand_mark: s.brand_mark,
    brand_logo_size: s.brand_logo_size,
    brand_logo_fit: s.brand_logo_fit,
    footer_links: s.footer_links,
    url_style: s.url_style,
  };
}

function sameBrand(a: SiteBrand, b: SiteBrand): boolean {
  return (
    a.site_name === b.site_name &&
    a.site_wordmark === b.site_wordmark &&
    a.site_slogan === b.site_slogan &&
    a.logo_light_url === b.logo_light_url &&
    a.logo_dark_url === b.logo_dark_url &&
    a.favicon_url === b.favicon_url &&
    a.brand_mark === b.brand_mark &&
    a.brand_logo_size === b.brand_logo_size &&
    a.brand_logo_fit === b.brand_logo_fit &&
    a.url_style === b.url_style &&
    JSON.stringify(a.footer_links) === JSON.stringify(b.footer_links)
  );
}

function applyFavicon(url: string) {
  // 只管理 #j13-favicon，禁止 remove 其它 icon 节点：
  // Next Metadata 注入的 <link rel="icon"> 由 React 持有，手动删会导致 removeChild 空指针。
  let link = document.getElementById("j13-favicon") as HTMLLinkElement | null;
  if (!link) {
    link = document.createElement("link");
    link.id = "j13-favicon";
    link.rel = "icon";
  }
  const href = url || "/favicon.ico";
  if (link.getAttribute("href") !== href) link.href = href;
  // 挪到 head 末尾，优先于 SSR 注入的 icon
  document.head.appendChild(link);
}

function retitle(prev: SiteBrand, next: SiteBrand) {
  if (prev.site_name === next.site_name && prev.site_slogan === next.site_slogan) return;
  const oldDefault = siteDocumentTitle(prev.site_name, prev.site_slogan);
  const nextDefault = siteDocumentTitle(next.site_name, next.site_slogan);
  const cur = document.title;
  if (cur === oldDefault) {
    document.title = nextDefault;
    return;
  }
  const oldName = prev.site_name.trim() || "姜十三论坛";
  const newName = next.site_name.trim() || "姜十三论坛";
  const suffix = ` · ${oldName}`;
  if (oldName !== newName && cur.endsWith(suffix)) {
    document.title = cur.slice(0, -suffix.length) + ` · ${newName}`;
  }
}

export function useSiteBrand(): SiteBrand {
  const ctx = useContext(SiteBrandContext);
  if (!ctx) {
    return {
      site_name: "姜十三论坛",
      site_wordmark: "",
      site_slogan: "",
      logo_light_url: "",
      logo_dark_url: "",
      favicon_url: "",
      brand_mark: "image_text",
      brand_logo_size: "sq",
      brand_logo_fit: "contain",
      footer_links: [],
      url_style: "default",
    };
  }
  return ctx;
}

/** 详情页伪静态风格（SSR 初值与水合一致，设置保存后 realtime 热更） */
export function useUrlStyle(): UrlStyle {
  return useSiteBrand().url_style;
}

/** SSR 初值 + settings:changed：页眉/页脚/标题/favicon 不必整页刷新 */
export default function SiteBrandProvider({
  initial,
  children,
}: {
  initial: PublicSettings;
  children: ReactNode;
}) {
  const [brand, setBrand] = useState<SiteBrand>(() => fromSettings(initial));
  const brandRef = useRef(brand);
  brandRef.current = brand;

  const value = useMemo(() => brand, [brand]);

  useEffect(() => {
    const next = fromSettings(initial);
    setBrand((prev) => {
      if (sameBrand(prev, next)) return prev;
      retitle(prev, next);
      if (prev.favicon_url !== next.favicon_url) applyFavicon(next.favicon_url);
      return next;
    });
  }, [initial]);

  useEffect(() => {
    const apply = (raw: Partial<PublicSettings> | RtSettingsData) => {
      const prev = brandRef.current;
      const next: SiteBrand = {
        site_name: typeof raw.site_name === "string" && raw.site_name.trim() ? raw.site_name : prev.site_name,
        site_wordmark: typeof raw.site_wordmark === "string" ? raw.site_wordmark : prev.site_wordmark,
        site_slogan: typeof raw.site_slogan === "string" ? raw.site_slogan : prev.site_slogan,
        logo_light_url: typeof raw.logo_light_url === "string" ? raw.logo_light_url : prev.logo_light_url,
        logo_dark_url: typeof raw.logo_dark_url === "string" ? raw.logo_dark_url : prev.logo_dark_url,
        favicon_url: typeof raw.favicon_url === "string" ? raw.favicon_url : prev.favicon_url,
        brand_mark: normalizeBrandMark(raw.brand_mark ?? prev.brand_mark),
        brand_logo_size: normalizeBrandLogoSize(raw.brand_logo_size ?? prev.brand_logo_size),
        brand_logo_fit: normalizeBrandLogoFit(raw.brand_logo_fit ?? prev.brand_logo_fit),
        footer_links: Array.isArray(raw.footer_links)
          ? normalizeFooterLinks(raw.footer_links)
          : prev.footer_links,
        url_style: raw.url_style !== undefined ? normalizeUrlStyle(raw.url_style) : prev.url_style,
      };
      if (sameBrand(prev, next)) return;
      retitle(prev, next);
      if (prev.favicon_url !== next.favicon_url) applyFavicon(next.favicon_url);
      brandRef.current = next;
      setBrand(next);
    };

    const off = realtime.on<RtSettingsData>(RT_SETTINGS_CHANGED, (data) => {
      if (data) apply(data);
    });

    let last = 0;
    const offVisible = onDocumentVisible(() => {
      const now = Date.now();
      if (now - last < VISIBLE_RECONCILE_GAP_MS) return;
      last = now;
      void apiGetSettings()
        .then(apply)
        .catch(() => {});
    }, VISIBLE_RECONCILE_GAP_MS);

    return () => {
      off();
      offVisible();
    };
  }, []);

  return <SiteBrandContext.Provider value={value}>{children}</SiteBrandContext.Provider>;
}