import type { Metadata } from "next";
import { notFound } from "next/navigation";
import { Megaphone } from "lucide-react";
import { fetchSitePageBySlug, fetchOverview } from "@/lib/api";
import { getPublicSettingsCached } from "@/lib/serverData";
import { extractToc, estimateReadingMinutes, markdownHeadingToc } from "@/lib/toc";
import MarkdownBody from "@/components/MarkdownBody";
import PostToc from "@/components/PostToc";
import {
  SiteDocShell,
  SiteDocIdentity,
  SiteDocPageNav,
  SiteDocAnnoNav,
  SiteDocMasthead,
  SiteDocBreadcrumb,
} from "@/components/site-doc";

interface PageProps {
  params: Promise<{ slug: string }>;
}

export async function generateMetadata({ params }: PageProps): Promise<Metadata> {
  const { slug } = await params;
  const data = await fetchSitePageBySlug(slug).catch(() => null);
  if (!data) return { title: "页面不存在" };
  const p = data.page;
  return {
    title: p.title,
    description: p.excerpt || p.title,
    openGraph: {
      title: p.title,
      description: p.excerpt || p.title,
      type: "article",
      publishedTime: p.created_at,
    },
  };
}

export default async function SitePagePublic({ params }: PageProps) {
  const { slug } = await params;
  const [data, overview, settings] = await Promise.all([
    fetchSitePageBySlug(slug).catch(() => null),
    fetchOverview().catch(() => null),
    getPublicSettingsCached(),
  ]);
  if (!data) notFound();

  const p = data.page;
  const sidebarPages = overview?.sidebar_pages ?? [];
  const announcements = overview?.announcements ?? [];
  const siteLead = settings.site_description?.trim() || undefined;
  const toc = extractToc(p.content);
  const headingToc = markdownHeadingToc(toc);
  const readingMinutes = estimateReadingMinutes(p.content, p.title.length);

  let headingIndex = 0;
  const headingRenderer = (Tag: "h2" | "h3") =>
    function Heading({ children }: { children?: React.ReactNode }) {
      const item = headingToc[headingIndex++];
      return (
        <Tag id={item?.id} style={{ scrollMarginTop: 90 }}>
          {children}
        </Tag>
      );
    };

  const jsonLd = {
    "@context": "https://schema.org",
    "@type": "WebPage",
    name: p.title,
    description: p.excerpt || undefined,
    datePublished: p.created_at,
    dateModified: p.updated_at,
  };

  const left = (
    <>
      <SiteDocIdentity kind="about" lead={siteLead} />
      <SiteDocPageNav pages={sidebarPages} currentSlug={slug} />
    </>
  );

  const right =
    toc.length > 0 ? (
      <PostToc items={toc} />
    ) : (
      <SiteDocAnnoNav items={announcements} />
    );

  return (
    <>
      <script
        type="application/ld+json"
        dangerouslySetInnerHTML={{ __html: JSON.stringify(jsonLd) }}
      />

      <SiteDocShell
        left={left}
        right={right}
        breadcrumb={
          <SiteDocBreadcrumb
            items={[
              { href: "/", label: "首页" },
              { label: "关于本站" },
              { label: p.title },
            ]}
          />
        }
        mobileExtras={
          <>
            {toc.length > 0 ? <PostToc items={toc} /> : null}
            <SiteDocPageNav pages={sidebarPages} currentSlug={slug} title="文档目录" />
            {toc.length === 0 && announcements.length > 0 ? (
              <SiteDocAnnoNav items={announcements} />
            ) : null}
          </>
        }
      >
        <article className="panel p-6 sm:p-8">
          <SiteDocMasthead
            kicker="官方文件"
            title={p.title}
            excerpt={p.excerpt || undefined}
            createdAt={p.created_at}
            updatedAt={p.updated_at}
            readingMinutes={readingMinutes}
            showTimeOfDay
          />

          <MarkdownBody
            content={p.content}
            components={
              headingToc.length > 0
                ? { h2: headingRenderer("h2"), h3: headingRenderer("h3") }
                : undefined
            }
          />
        </article>

        <div className="mt-5 flex items-center gap-2 text-[12.5px] meta">
          <Megaphone size={14} style={{ color: "var(--accent)" }} />
          <span>由站点管理团队维护</span>
        </div>
      </SiteDocShell>
    </>
  );
}