import type { Metadata } from "next";
import Link from "next/link";
import { PageHeader } from "@/components/layout/page-header";
import { notFound } from "next/navigation";
import { Card, CardContent } from "@/components/ui/card";
import { FindInPage } from "@/components/layout/find-in-page";
import { ExtractedVerseCount } from "../../extracted-verse-count";
import { getBookMeta, getProseChapter } from "@/lib/api";
import { buildOgMeta } from "@/lib/og";
import { BOOK_NAMES } from "@/lib/constants";

export async function generateMetadata({
  params,
}: {
  params: Promise<{ canto: string }>;
}): Promise<Metadata> {
  const { canto } = await params;
  const title = BOOK_NAMES["sb"] || "Śrīmad-Bhāgavatam";
  // A non-numeric segment (preface, introduction) is front matter.
  if (isNaN(parseInt(canto))) {
    const segment = await getProseChapter("sb", 0, canto);
    if (segment) return buildOgMeta({ title, detail: segment.title });
  }
  return buildOgMeta({ title, detail: `Canto ${canto}` });
}

type ChapterInfo = {
  number: number;
  title: string;
  totalVerses: number;
};

type CantoInfo = {
  number: number;
  title: string;
  totalChapters: number;
  chapters: ChapterInfo[];
};

export default async function CantoPage({
  params,
}: {
  params: Promise<{ canto: string }>;
}) {
  const { canto } = await params;
  const cantoNum = parseInt(canto);

  // Front matter — a non-numeric param (preface, introduction) resolves to a
  // prose intro-segment.
  if (isNaN(cantoNum)) {
    const segment = await getProseChapter("sb", 0, canto);
    if (!segment) notFound();

    return (
      <div className="min-h-screen bg-background">
        <PageHeader sticky>
          <Link
            href="/books/sb"
            className="text-sm text-muted-foreground hover:text-foreground transition-colors"
          >
            &larr; Śrīmad-Bhāgavatam
          </Link>
          <div className="mt-3 flex items-start justify-between gap-3">
            <h1 className="text-2xl font-bold text-foreground">
              {segment.title}
            </h1>
            <FindInPage targetId="book-content" className="shrink-0 mt-0.5" />
          </div>
        </PageHeader>

        <main className="max-w-5xl mx-auto px-6 py-8">
          <Card id="book-content">
            <CardContent className="py-8 px-6 sm:px-8">
              <div className="space-y-4">
                {segment.paragraphs.map((paragraph, i) => (
                  <div
                    key={i}
                    className="text-base text-foreground leading-relaxed"
                    dangerouslySetInnerHTML={{ __html: paragraph }}
                  />
                ))}
              </div>
            </CardContent>
          </Card>
        </main>
      </div>
    );
  }

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

  const cantos = (meta as unknown as { cantos: CantoInfo[] }).cantos;
  const cantoInfo = cantos.find((c) => c.number === cantoNum);
  if (!cantoInfo) notFound();

  const totalVerses = cantoInfo.chapters.reduce(
    (sum, ch) => sum + ch.totalVerses,
    0,
  );

  return (
    <div className="min-h-screen bg-background">
      <PageHeader>
        <Link
          href="/books/sb"
          className="text-sm text-muted-foreground hover:text-foreground"
        >
          &larr; Śrīmad-Bhāgavatam
        </Link>
        <h1 className="mt-3 text-3xl font-bold text-foreground">
          Canto {cantoInfo.number}: {cantoInfo.title}
        </h1>
        <p className="mt-1 text-muted-foreground">
          {cantoInfo.totalChapters} chapters ·{" "}
          <ExtractedVerseCount count={totalVerses} label="extracted verses" />
        </p>
      </PageHeader>
      <main className="max-w-5xl mx-auto px-6 py-8">
        <Card className="divide-y divide-border">
          <CardContent className="p-0">
            <ul className="divide-y divide-border">
              {cantoInfo.chapters.map((ch) => (
                <li key={ch.number}>
                  <Link
                    href={`/books/sb/${cantoNum}/${ch.number}`}
                    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.number}
                      </span>
                      <p className="font-medium text-foreground">{ch.title}</p>
                    </div>
                    <span className="text-sm text-muted-foreground sm:shrink-0 sm:ml-4">
                      <ExtractedVerseCount count={ch.totalVerses} />
                    </span>
                  </Link>
                </li>
              ))}
            </ul>
          </CardContent>
        </Card>
      </main>
    </div>
  );
}