import type { Metadata } from "next";
import type { CSSProperties } from "react";
import { notFound } from "next/navigation";
import Link from "next/link";
import { BookOpen, Download, Paperclip } from "lucide-react";
import { fetchLibraryDocBySlug, type LibraryFileItem } from "@/lib/api";
import { coverHue } from "@/lib/coverColor";
import { getPublicSettingsCached } from "@/lib/serverData";
import MarkdownBody from "@/components/MarkdownBody";
import { SiteDocMasthead } from "@/components/site-doc";
import { requestCanonical } from "@/lib/canonicalMeta";
import { libraryDocPath, libraryDocReadPath, userPath } from "@/lib/urlStyle";
import { webPageJsonLd } from "@/lib/jsonLd";
import JsonLd from "@/components/JsonLd";
import { estimateReadingMinutes } from "@/lib/toc";
import { groupSections } from "@/lib/librarySections";
import LightboxImage from "@/components/LightboxImage";
import AdaptiveCoverSlot from "@/components/AdaptiveCoverSlot";
import Avatar from "@/components/Avatar";

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

function formatSize(n: number): string {
  if (!Number.isFinite(n) || n <= 0) return "0 B";
  if (n < 1024) return `${n} B`;
  if (n < 1024 * 1024) return `${(n / 1024).toFixed(1)} KB`;
  return `${(n / (1024 * 1024)).toFixed(1)} MB`;
}

/** 无封面时：完整书名 + 书名派生稳定色相渐变块（有图封面走 AdaptiveCoverSlot 按横竖版自适应摆放） */
function CoverFallback({ title }: { title: string }) {
  const name = title.trim() || "书";
  return (
    <div
      className="j13-text-cover w-full aspect-[3/4] rounded-2xl flex items-center justify-center px-6 select-none"
      style={{ "--cover-h": coverHue(name) } as CSSProperties}
      aria-hidden
    >
      <span className="text-[26px] font-extrabold leading-relaxed text-center line-clamp-5 break-all">
        {name}
      </span>
    </div>
  );
}

// 附件仅下载分发（书籍正文走阅读页逐章阅读）

function ExtChip({ ext }: { ext: string }) {
  return (
    <span
      className="text-[10.5px] font-semibold px-1.5 py-0.5 rounded-md uppercase tracking-wide shrink-0"
      style={{
        color: "var(--accent)",
        background: "var(--accent-soft)",
        border: "1px solid color-mix(in srgb, var(--accent) 30%, transparent)",
      }}
    >
      {ext}
    </span>
  );
}

function FileRow({ f }: { f: LibraryFileItem }) {
  return (
    <div
      className="rounded-xl px-3 py-2.5"
      style={{ border: "1px solid var(--line)", background: "var(--bg)" }}
    >
      {/* 紧凑两行式：适配左栏窄列，文件名过长截断（悬停可见全名），避免被压成逐字换行 */}
      <div className="flex items-center gap-2 min-w-0">
        <ExtChip ext={f.ext} />
        <span
          className="text-[13px] font-medium min-w-0 truncate"
          style={{ color: "var(--ink)" }}
          title={f.name}
        >
          {f.name}
        </span>
      </div>
      <div className="mt-2 flex items-center justify-between gap-2">
        <span className="meta text-[11.5px] shrink-0">
          {formatSize(f.size)} · {f.download_count} 次下载
        </span>
        <a
          href={`/api/library/files/${f.id}/download`}
          className="btn btn-sm btn-primary inline-flex items-center gap-1.5 shrink-0"
        >
          <Download size={13} /> 下载
        </a>
      </div>
    </div>
  );
}

export async function generateMetadata({ params }: PageProps): Promise<Metadata> {
  const { slug } = await params;
  const data = await fetchLibraryDocBySlug(slug).catch(() => null);
  if (!data) return { title: "条目不存在" };
  const d = data.doc;
  return {
    title: d.title,
    description: d.description ? d.description.slice(0, 150) : d.title,
    openGraph: {
      title: d.title,
      description: d.description ? d.description.slice(0, 150) : d.title,
      type: "article",
      publishedTime: d.created_at,
    },
    ...(await requestCanonical(libraryDocPath((await getPublicSettingsCached()).url_style, d.slug))),
  };
}

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

  const d = data.doc;
  const urlStyle = settings.url_style;
  const chapterCount = groupSections(d.sections ?? []).length;

  const readingMinutes = estimateReadingMinutes(
    [d.description, ...(d.sections ?? []).map((s) => s.content)].filter(Boolean).join("\n\n")
  );

  const jsonLd = webPageJsonLd({
    name: d.title,
    description: d.description ? d.description.slice(0, 150) : undefined,
    path: libraryDocPath(urlStyle, d.slug),
    datePublished: d.created_at,
    dateModified: d.updated_at,
  });

  return (
    <>
      <JsonLd data={jsonLd} />
      <div className="max-w-[1200px] 2xl:max-w-[1320px] mx-auto min-w-0">
        {/* 手机端水平内边距收窄（px-3），介绍内容近全宽；sm 起恢复常规面板内距 */}
        <article className="panel px-3 py-5 sm:p-8">
          <SiteDocMasthead
            kicker="书库"
            title={d.title}
            createdAt={d.created_at}
            updatedAt={d.updated_at}
            showTimeOfDay
            readingMinutes={readingMinutes}
            badges={
              chapterCount > 0 ? (
                <span
                  className="inline-flex items-center rounded-full px-2.5 py-0.5 text-[11.5px] font-semibold"
                  style={{ background: "var(--panel-2)", color: "var(--ink-2)", border: "1px solid var(--line)" }}
                >
                  {chapterCount} 章
                </span>
              ) : undefined
            }
          />

          {/* 横版封面（宽>高且足够大）：全宽置于内容上方；竖版或过小的横版图时此槽位不渲染。
              小图不强行放大占满全宽：max-w-full 下保持自然尺寸，容器随内容收缩并水平居中 */}
          {d.cover_url ? (
            <AdaptiveCoverSlot
              orientation="landscape"
              src={d.cover_url}
              naturalWidth={d.cover_width}
              naturalHeight={d.cover_height}
            >
              <div
                className="mt-6 w-fit max-w-full mx-auto overflow-hidden rounded-2xl"
                style={{ border: "1px solid var(--line)" }}
              >
                <LightboxImage
                  src={d.cover_url}
                  alt={d.title}
                  className="max-w-full h-auto block"
                  variantWidths={[768, 1080, 1920]}
                  sizes="(max-width:1280px) 92vw, 1080px"
                />
              </div>
            </AdaptiveCoverSlot>
          ) : null}

          <div className="mt-6 lg:grid lg:grid-cols-[minmax(0,340px)_minmax(0,1fr)] lg:gap-8">
            {/* 左栏：封面 + 元信息 + 开始阅读 */}
            <aside className="lg:sticky lg:top-[84px] self-start">
              {d.cover_url ? (
                // 竖版封面（长>宽）及过小的横版封面：按图片自然比例显示在左栏；
                // 小图不强行放大占满：保持自然尺寸，在槽位最大区域内水平垂直居中
                <AdaptiveCoverSlot
                  orientation="portrait"
                  src={d.cover_url}
                  naturalWidth={d.cover_width}
                  naturalHeight={d.cover_height}
                >
                  <div
                    className="w-fit max-w-full mx-auto overflow-hidden rounded-2xl"
                    style={{ border: "1px solid var(--line)" }}
                  >
                    <LightboxImage
                      src={d.cover_url}
                      alt={d.title}
                      className="max-w-full h-auto block"
                      variantWidths={[384, 768]}
                      sizes="(max-width:1023px) 92vw, 340px"
                    />
                  </div>
                </AdaptiveCoverSlot>
              ) : (
                <CoverFallback title={d.title} />
              )}
              <dl className="mt-4 flex flex-col gap-2 text-[13px]">
                {d.author ? (
                  <div className="flex items-start justify-between gap-3">
                    <dt className="meta shrink-0">作者</dt>
                    <dd
                      className="font-semibold text-right min-w-0"
                      style={{ color: "var(--ink)" }}
                    >
                      {d.author}
                    </dd>
                  </div>
                ) : null}
                <div className="flex items-center justify-between">
                  <dt className="meta">章节数</dt>
                  <dd className="tabular-nums font-semibold" style={{ color: "var(--ink)" }}>
                    {chapterCount}
                  </dd>
                </div>
                <div className="flex items-center justify-between">
                  <dt className="meta">附件数</dt>
                  <dd className="tabular-nums font-semibold" style={{ color: "var(--ink)" }}>
                    {d.files.length}
                  </dd>
                </div>
                {d.creator ? (
                  <div className="flex items-center justify-between gap-2">
                    <dt className="meta shrink-0">创建者</dt>
                    <dd className="min-w-0">
                      <Link
                        href={userPath(urlStyle, d.creator.id)}
                        className="inline-flex items-center gap-1.5 min-w-0"
                        title={`@${d.creator.username}`}
                      >
                        <Avatar
                          size={20}
                          name={d.creator.nickname || d.creator.username}
                          src={d.creator.avatar}
                        />
                        <span
                          className="text-[12.5px] font-medium truncate max-w-[9rem]"
                          style={{ color: "var(--ink)" }}
                        >
                          {d.creator.nickname || d.creator.username}
                        </span>
                      </Link>
                    </dd>
                  </div>
                ) : null}
              </dl>
              {chapterCount > 0 ? (
                <Link
                  href={libraryDocReadPath(urlStyle, d.slug)}
                  className="btn btn-primary mt-4 w-full justify-center inline-flex items-center gap-2"
                >
                  <BookOpen size={15} aria-hidden /> 开始阅读
                </Link>
              ) : null}

              {/* 附件下载紧跟阅读按钮：左栏桌面端 sticky 常驻，移动端排在介绍之前，
                  避免介绍过长时用户需要长距离滚动寻找下载入口 */}
              {d.files.length > 0 ? (
                <section id="files" className="mt-5 scroll-mt-24">
                  <h2
                    className="text-[13.5px] font-bold inline-flex items-center gap-2"
                    style={{ color: "var(--ink)" }}
                  >
                    <Download size={14} style={{ color: "var(--accent)" }} aria-hidden />
                    附件下载（{d.files.length}）
                  </h2>
                  <div className="mt-2.5 flex flex-col gap-2">
                    {d.files.map((f) => (
                      <FileRow key={f.id} f={f} />
                    ))}
                  </div>
                </section>
              ) : null}
            </aside>

            {/* 右栏：介绍（附件下载已移至左栏阅读按钮下方） */}
            <div className="mt-6 lg:mt-0 min-w-0">
              <section>
                <h2
                  className="text-[15px] font-bold inline-flex items-center gap-2"
                  style={{ color: "var(--ink)" }}
                >
                  <Paperclip size={15} style={{ color: "var(--accent)" }} aria-hidden />
                  介绍
                </h2>
                <div className="mt-3">
                  {d.description ? (
                    <MarkdownBody content={d.description} />
                  ) : (
                    <p className="meta text-[13px]">这本书还没有介绍。</p>
                  )}
                </div>
              </section>
            </div>
          </div>
        </article>

        <div className="mt-5 flex items-center gap-2 text-[12.5px] meta">
          <BookOpen size={14} style={{ color: "var(--accent)" }} aria-hidden />
          <span>来自站点书库</span>
        </div>
      </div>
    </>
  );
}