import { db } from "../../../db/index";
import { courses, topics, userProgress, 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 progressRows = await db.query.userProgress.findMany({
    where: eq(userProgress.courseId, id),
  });

  const progressMap: Record<string, typeof progressRows[0]> = {};
  for (const p of progressRows) progressMap[p.topicId] = p;

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

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

  const lessonTopicIds = new Set(lessonRows.map((l) => l.topicId));

  return {
    ...course,
    topics: topicRows.map((t) => ({
      ...t,
      prerequisiteTopicIds: JSON.parse(t.prerequisiteTopicIds ?? "[]"),
      progress: progressMap[t.id] ?? null,
      hasLesson: lessonTopicIds.has(t.id),
    })),
  };
});