import type { Metadata } from "next";
import Link from "next/link";
import { notFound } from "next/navigation";
import { getBookMeta, getProseChapters } from "@/lib/api";
import { buildOgMeta } from "@/lib/og";
import { BOOK_NAMES } from "@/lib/constants";
import { PageHeader } from "@/components/layout/page-header";
import { Card, CardContent } from "@/components/ui/card";

export async function generateMetadata({
  params,
}: {
  params: Promise<{ volume: string }>;
}): Promise<Metadata> {
  const { volume } = await params;
  const title = BOOK_NAMES["kb"] || "KB";
  return buildOgMeta({ title, detail: `Volume ${volume}` });
}

export default async function KbVolumePage({
  params,
}: {
  params: Promise<{ volume: string }>;
}) {
  const { volume } = await params;
  const vol = parseInt(volume);
  if (isNaN(vol) || vol < 1 || vol > 2) notFound();

  const meta = await getBookMeta("kb");
  if (!meta) notFound();

  const title = meta.title as string;

  const [introSegments, chapters] = await Promise.all([
    getProseChapters("kb", vol, "intro-segment"),
    getProseChapters("kb", vol, "chapter"),
  ]);

  return (
    <div className="min-h-screen bg-background">
      <PageHeader>
        <Link
          href="/books/kb"
          className="text-sm text-muted-foreground hover:text-foreground transition-colors"
        >
          &larr; {title}
        </Link>
        <h1 className="mt-3 text-3xl font-bold text-foreground">
          Volume {vol}
        </h1>
        <p className="mt-1 text-muted-foreground">{chapters.length} chapters</p>
      </PageHeader>
      <main className="max-w-5xl mx-auto px-6 py-8 space-y-8">
        {/* Front Matter */}
        {introSegments.length > 0 && (
          <div>
            <h2 className="text-sm font-bold uppercase tracking-wider text-muted-foreground mb-3">
              Front Matter
            </h2>
            <Card className="divide-y divide-border">
              <CardContent className="p-0">
                <ul className="divide-y divide-border">
                  {introSegments.map((seg) => (
                    <li key={seg.slug}>
                      <Link
                        href={`/books/kb/${vol}/${seg.slug}`}
                        className="flex flex-col sm:flex-row sm:items-center sm:justify-between px-5 py-4 gap-1 sm:gap-0 hover:bg-muted transition-colors"
                      >
                        <div>
                          <p className="font-medium text-foreground">
                            {seg.title}
                          </p>
                        </div>
                        <span className="text-sm text-muted-foreground sm:shrink-0 sm:ml-4">
                        </span>
                      </Link>
                    </li>
                  ))}
                </ul>
              </CardContent>
            </Card>
          </div>
        )}

        {/* Chapters */}
        <div>
          <h2 className="text-sm font-bold uppercase tracking-wider text-muted-foreground mb-3">
            Chapters
          </h2>
          <Card className="divide-y divide-border">
            <CardContent className="p-0">
              <ul className="divide-y divide-border">
                {chapters.map((ch) => (
                  <li key={ch.slug}>
                    <Link
                      href={`/books/kb/${vol}/${ch.slug}`}
                      className="flex flex-col sm:flex-row sm:items-center sm:justify-between px-5 py-4 gap-1 sm:gap-0 hover:bg-muted transition-colors"
                    >
                      <div>
                        <span className="text-sm text-primary font-medium">
                          Chapter {ch.chapter}
                        </span>
                        <p className="font-medium text-foreground">
                          {ch.title}
                        </p>
                      </div>
                      <span className="text-sm text-muted-foreground sm:shrink-0 sm:ml-4">
                      </span>
                    </Link>
                  </li>
                ))}
              </ul>
            </CardContent>
          </Card>
        </div>
      </main>
    </div>
  );
}