import Link from "next/link";
import { notFound } from "next/navigation";
import { getServerSession } from "next-auth";
import { authOptions } from "@/lib/auth-options";
import { getCourseBySlug, firstLessonPath } from "@/lib/course-queries";
import { formatMoney, billingLabel } from "@/lib/format";
import { prisma } from "@/lib/prisma";
import { EnrollButton } from "@/components/enroll-button";

type Props = { params: Promise<{ slug: string }> };

export default async function CoursePage({ params }: Props) {
  const { slug } = await params;
  const course = await getCourseBySlug(slug);
  if (!course) notFound();

  const session = await getServerSession(authOptions);
  const enrollment =
    session?.user?.id &&
    (await prisma.enrollment.findUnique({
      where: { userId_courseId: { userId: session.user.id, courseId: course.id } },
    }));

  const startPath = firstLessonPath(course);
  const cats = course.categories.map((c) => c.category.name).join(", ");
  const priceSuffix = billingLabel(course.billingInterval);
  const isFree = course.priceCents === 0;

  return (
    <section className="section">
      <div className="container">
        <p className="muted">
          <Link href="/kurse">← Alle Kurse</Link>
        </p>
        <h1>{course.title}</h1>
        <p className="course-meta">
          Von <strong>{course.authorName}</strong>
          {cats ? <> · {cats}</> : null}
        </p>
        {!isFree && (
          <p className="course-price">
            {formatMoney(course.priceCents, course.currency)}
            {priceSuffix ? ` ${priceSuffix}` : ""}{" "}
            <span className="muted">(Zahlungsanbindung in Arbeit – aktuell nicht kaufbar)</span>
          </p>
        )}

        <div style={{ margin: "1.5rem 0" }}>
          {!session ? (
            <Link href={`/login?callbackUrl=/kurse/${course.slug}`} className="btn btn-primary">
              Anmelden, um fortzufahren
            </Link>
          ) : enrollment && startPath ? (
            <Link href={startPath} className="btn btn-primary">
              Mit dem Lernen beginnen
            </Link>
          ) : enrollment ? (
            <span className="muted">Noch keine Lektionen.</span>
          ) : isFree ? (
            <EnrollButton courseSlug={course.slug} />
          ) : (
            <p className="muted">Kostenpflichtige Kurse werden über Stripe angebunden.</p>
          )}
        </div>

        <div className="panel">
          <h2>Kurrikulum</h2>
          {course.description ? <p>{course.description}</p> : null}
          <ul className="curriculum">
            {course.modules.map((m) => (
              <li key={m.id}>
                <div className="module-title">{m.title}</div>
                <ul className="curriculum">
                  {m.lessons.map((lesson) => {
                    const href = `/kurse/${course.slug}/lektionen/${lesson.slug}`;
                    return (
                      <li key={lesson.id}>
                        <Link href={href}>{lesson.title}</Link>
                      </li>
                    );
                  })}
                </ul>
              </li>
            ))}
          </ul>
        </div>
      </div>
    </section>
  );
}