import type { Metadata } from "next";
import type { CSSProperties } from "react";
import Link from "next/link";
import { BookOpen, FileDown } from "lucide-react";
import { fetchLibraryList, type LibraryDocListItem } from "@/lib/api";
import { coverHue } from "@/lib/coverColor";
import { getPublicSettingsCached } from "@/lib/serverData";
import { requestCanonical } from "@/lib/canonicalMeta";
import { libraryPath, libraryDocPath } from "@/lib/urlStyle";

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`;
}

/** 文字封面：无图时用完整书名 + 书名派生稳定色相洗底（lib/coverColor.ts） */
function TextCover({ title }: { title: string }) {
  const name = title.trim() || "书";
  return (
    <div
      className="j13-text-cover w-full h-full flex items-center justify-center px-5 select-none"
      style={{ "--cover-h": coverHue(name) } as CSSProperties}
      aria-hidden
    >
      <span
        className="text-[22px] font-extrabold leading-snug text-center line-clamp-3 break-all"
      >
        {name}
      </span>
    </div>
  );
}

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

function DocCard({
  doc,
  href,
}: {
  doc: LibraryDocListItem;
  href: string;
}) {
  const exts = Array.from(new Set(doc.files.map((f) => f.ext))).slice(0, 4);
  const totalSize = doc.files.reduce((acc, f) => acc + f.size, 0);
  return (
    <Link
      href={href}
      className="group flex flex-col overflow-hidden rounded-[20px] transition-transform hover:-translate-y-0.5"
      style={{
        background: "var(--panel)",
        border: "1px solid var(--line)",
      }}
    >
      <div className="h-36 overflow-hidden" style={{ borderBottom: "1px solid var(--line)" }}>
        {doc.cover_url ? (
          // eslint-disable-next-line @next/next/no-img-element
          <img
            src={doc.cover_url}
            alt={doc.title}
            className="w-full h-full object-cover transition-transform duration-300 group-hover:scale-[1.03]"
            loading="lazy"
            decoding="async"
            draggable={false}
          />
        ) : (
          <TextCover title={doc.title} />
        )}
      </div>
      <div className="p-4 flex flex-col gap-2 flex-1">
        <h2
          className="text-[15px] font-bold leading-snug line-clamp-2"
          style={{ color: "var(--ink)" }}
        >
          {doc.title}
        </h2>
        <div className="mt-auto flex flex-wrap items-center gap-1.5">
          {exts.map((ext) => (
            <ExtChip key={ext} ext={ext} />
          ))}
          <span className="meta text-[11px] ml-auto inline-flex items-center gap-1">
            <FileDown size={11} />
            {doc.file_count > 0 ? `${doc.file_count} 个文件 · ${formatSize(totalSize)}` : "暂无文件"}
          </span>
        </div>
      </div>
    </Link>
  );
}

export async function generateMetadata(): Promise<Metadata> {
  const settings = await getPublicSettingsCached();
  return {
    title: "书库",
    description: settings.site_description,
    ...(await requestCanonical(libraryPath(settings.url_style))),
  };
}

export default async function LibraryPage() {
  const settings = await getPublicSettingsCached();
  const urlStyle = settings.url_style;

  // 接口失败降级为空态，不让页面 500
  let docs: LibraryDocListItem[] = [];
  try {
    const res = await fetchLibraryList();
    docs = res.docs ?? [];
  } catch {
    /* 降级空态 */
  }

  return (
    <div className="min-w-0">
      {/* Hero：渐变洗底（与排行榜同语言） */}
      <section
        className="relative overflow-hidden rounded-[28px] px-6 py-8 sm:px-10 sm:py-10 text-center"
        style={{
          background:
            "radial-gradient(120% 160% at 12% -10%, color-mix(in srgb, var(--accent) 16%, transparent), transparent 55%)," +
            "radial-gradient(90% 140% at 90% -20%, color-mix(in srgb, var(--accent) 8%, transparent), transparent 50%)",
          border: "1px solid var(--line)",
        }}
      >
        <div
          aria-hidden
          className="absolute -top-16 -right-10 w-56 h-56 rounded-full pointer-events-none"
          style={{
            background: "color-mix(in srgb, var(--accent) 14%, transparent)",
            filter: "blur(48px)",
          }}
        />
        <div className="relative">
          <h1
            className="text-[26px] sm:text-[32px] leading-tight font-extrabold tracking-tight inline-flex items-center gap-2.5"
            style={{ color: "var(--ink)" }}
          >
            <BookOpen size={26} style={{ color: "var(--accent)" }} />
            书库
          </h1>
          <p className="meta mt-2 text-[13.5px]">书籍、文档与页面作品，在线阅读或下载</p>
        </div>
      </section>

      {docs.length === 0 ? (
        <div
          className="mt-6 rounded-[20px] px-6 py-14 text-center"
          style={{ background: "var(--panel)", border: "1px solid var(--line)" }}
        >
          <p className="text-[14px] font-medium" style={{ color: "var(--ink-2)" }}>
            书库还没有内容
          </p>
          <p className="meta text-[12.5px] mt-1.5">管理员可在后台「书库管理」发布条目</p>
        </div>
      ) : (
        <div className="mt-6 grid gap-4 sm:grid-cols-2 xl:grid-cols-3">
          {docs.map((d) => (
            <DocCard key={d.id} doc={d} href={libraryDocPath(urlStyle, d.slug)} />
          ))}
        </div>
      )}
    </div>
  );
}