import { NextResponse } from "next/server";
import { getServerSession } from "next-auth";
import { authOptions } from "@/lib/auth-options";
import { prisma } from "@/lib/prisma";
import { syncCertificateForCourse } from "@/lib/certificates";

export async function POST(req: Request) {
  const session = await getServerSession(authOptions);
  if (!session?.user?.id) {
    return NextResponse.json({ error: "Nicht angemeldet." }, { status: 401 });
  }

  const body = (await req.json().catch(() => null)) as {
    lessonId?: string;
    completed?: boolean;
  } | null;

  const lessonId = body?.lessonId?.trim();
  if (!lessonId) {
    return NextResponse.json({ error: "lessonId fehlt." }, { status: 400 });
  }

  const lesson = await prisma.lesson.findUnique({
    where: { id: lessonId },
    include: { module: { include: { course: true } } },
  });
  if (!lesson) {
    return NextResponse.json({ error: "Lektion nicht gefunden." }, { status: 404 });
  }

  const courseId = lesson.module.course.id;
  const enrollment = await prisma.enrollment.findUnique({
    where: { userId_courseId: { userId: session.user.id, courseId } },
  });
  if (!enrollment) {
    return NextResponse.json({ error: "Nicht eingeschrieben." }, { status: 403 });
  }

  const completed =
    typeof body?.completed === "boolean" ? body.completed : true;

  if (completed) {
    await prisma.lessonProgress.upsert({
      where: { userId_lessonId: { userId: session.user.id, lessonId } },
      update: { completedAt: new Date() },
      create: { userId: session.user.id, lessonId, completedAt: new Date() },
    });
    await syncCertificateForCourse(session.user.id, courseId);
  } else {
    await prisma.lessonProgress.deleteMany({
      where: { userId: session.user.id, lessonId },
    });
    await syncCertificateForCourse(session.user.id, courseId);
  }

  return NextResponse.json({ ok: true });
}