import { db } from "../../../db/index";
import { courses, topics, lessons } from "../../../db/schema";
import { eq, inArray } from "drizzle-orm";

export default defineEventHandler(async (event) => {
  const id = getRouterParam(event, "id")!;

  const course = await db.query.courses.findFirst({
    where: eq(courses.id, id),
  });

  if (!course) throw createError({ statusCode: 404, message: "Course not found" });

  const topicRows = await db.query.topics.findMany({
    where: eq(topics.courseId, id),
    orderBy: (t, { asc }) => asc(t.order),
  });

  const topicIds = topicRows.map((t) => t.id);

  const lessonRows = topicIds.length
    ? await db.query.lessons.findMany({ where: inArray(lessons.topicId, topicIds) })
    : [];

  const lessonMap: Record<string, typeof lessonRows[0]> = {};
  for (const l of lessonRows) lessonMap[l.topicId] = l;

  return {
    ...course,
    topics: topicRows.map((t) => ({
      ...t,
      prerequisiteTopicIds: JSON.parse(t.prerequisiteTopicIds ?? "[]"),
      hasLesson: !!lessonMap[t.id],
      lessonCost: lessonMap[t.id]?.costTotal ?? null,
    })),
  };
});