import { redirect } from "next/navigation";
import { notFound } from "next/navigation";
import { getChapterVerseIndex } from "@/lib/api";
import { Card, CardContent } from "@/components/ui/card";
import { PageHeader } from "@/components/page-header";
import Link from "next/link";
import fs from "fs";
import path from "path";

const NBS_JSON_DIR = path.join(process.cwd(), "lib", "jsons", "books", "nbs");

type IntroSegment = {
  slug: string;
  title: string;
  paragraphs: string[];
};

export default async function NbsChapterPage({
  params,
}: {
  params: Promise<{ chapter: string }>;
}) {
  const { chapter } = await params;

  // Handle intro segments (intro-introduction)
  if (chapter.startsWith("intro-")) {
    const rawSlug = chapter.replace(/^intro-/, "");
    const filePath = path.join(NBS_JSON_DIR, "intro", `${rawSlug}.json`);

    if (!fs.existsSync(filePath)) notFound();

    let segment: IntroSegment;
    try {
      segment = JSON.parse(fs.readFileSync(filePath, "utf-8"));
    } catch {
      notFound();
    }

    return (
      <div className="min-h-screen bg-background">
        <PageHeader sticky wide>
          <Link
            href="/books/nbs"
            className="text-sm text-muted-foreground hover:text-foreground transition-colors"
          >
            &larr; Nārada-bhakti-sūtra
          </Link>
          <h1 className="mt-3 text-2xl font-bold text-foreground">
            {segment.title}
          </h1>
        </PageHeader>

        <main className="max-w-3xl mx-auto px-6 py-8">
          <Card>
            <CardContent className="py-8 px-6 sm:px-8">
              <div className="space-y-4">
                {segment.paragraphs.map((paragraph: string, i: number) => (
                  <div
                    key={i}
                    className="text-base text-foreground leading-relaxed"
                    dangerouslySetInnerHTML={{ __html: paragraph }}
                  />
                ))}
              </div>
            </CardContent>
          </Card>
        </main>
      </div>
    );
  }

  // Handle numeric chapters — redirect to first verse
  const chapterNum = parseInt(chapter);
  if (isNaN(chapterNum)) notFound();

  // Try DB first
  const verseIndex = await getChapterVerseIndex("nbs", null, chapterNum);

  // Fallback to local JSON
  if (verseIndex.length === 0) {
    const versesDir = path.join(
      NBS_JSON_DIR,
      "chapters",
      String(chapterNum).padStart(2, "0"),
      "verses",
    );
    if (fs.existsSync(versesDir)) {
      const files = fs
        .readdirSync(versesDir)
        .filter((f: string) => f.endsWith(".json"))
        .sort();
      if (files.length > 0) {
        const first = JSON.parse(
          fs.readFileSync(path.join(versesDir, files[0]), "utf-8"),
        );
        redirect(`/books/nbs/${chapter}/${first.verse}`);
      }
    }
    notFound();
  }

  redirect(`/books/nbs/${chapter}/${verseIndex[0].verse}`);
}