import { randomBytes } from "crypto";
import { prisma } from "@/lib/prisma";
import { getUserCourseProgress } from "@/lib/course-progress";

function makeCode() {
  return `FA-${randomBytes(5).toString("hex").toUpperCase()}`;
}

export async function syncCertificateForCourse(userId: string, courseId: string) {
  const { total, completed } = await getUserCourseProgress(userId, courseId);

  const existing = await prisma.certificate.findUnique({
    where: { userId_courseId: { userId, courseId } },
  });

  if (total === 0 || completed < total) {
    if (existing) {
      await prisma.certificate.delete({ where: { id: existing.id } });
    }
    return { issued: false as const };
  }

  if (existing) {
    return { issued: true as const, code: existing.code };
  }

  let code = makeCode();
  for (let i = 0; i < 8; i++) {
    const clash = await prisma.certificate.findUnique({ where: { code } });
    if (!clash) break;
    code = makeCode();
  }

  await prisma.certificate.create({
    data: { userId, courseId, code },
  });

  return { issued: true as const, code };
}

export async function clearCourseProgress(userId: string, courseId: string) {
  const lessons = await prisma.lesson.findMany({
    where: { module: { courseId } },
    select: { id: true },
  });
  await prisma.lessonProgress.deleteMany({
    where: { userId, lessonId: { in: lessons.map((l) => l.id) } },
  });
  await prisma.certificate.deleteMany({ where: { userId, courseId } });
}