import { db } from "../../../db/index";
import { uploads, courses } from "../../../db/schema";
import { eq } from "drizzle-orm";
import { randomUUID } from "crypto";
import { writeFile, mkdir } from "fs/promises";
import { resolve } from "path";
import { parsePdf } from "../../../utils/parsePdf";
import { detectUploadType } from "../../../utils/detectUploadType";

const UUID_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i;

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

  if (!UUID_RE.test(id)) {
    throw createError({ statusCode: 400, message: "Invalid course id" });
  }

  const course = await db.query.courses.findFirst({ where: eq(courses.id, id) });
  if (!course) throw createError({ statusCode: 404, message: "Course not found" });

  const formData = await readFormData(event);
  const file = formData.get("file") as File | null;

  if (!file) {
    throw createError({ statusCode: 400, message: "file is required" });
  }

  // 50mb limit
  if (file.size > 50 * 1024 * 1024) {
    throw createError({ statusCode: 400, message: "File exceeds 50MB limit" });
  }

  const buffer = Buffer.from(await file.arrayBuffer());

  // check pdf magic bytes: %PDF = 0x25 0x50 0x44 0x46
  if (buffer[0] !== 0x25 || buffer[1] !== 0x50 || buffer[2] !== 0x44 || buffer[3] !== 0x46) {
    throw createError({ statusCode: 400, message: "File does not appear to be a valid PDF" });
  }

  const uploadDir = resolve(process.cwd(), "uploads", id);
  await mkdir(uploadDir, { recursive: true });

  const uploadId = randomUUID();
  const safeFilename = `${uploadId}-${file.name.replace(/[^a-zA-Z0-9._-]/g, "_")}`;

  // safeFilename shouldnt be just dots/underscores
  if (/^[._]+$/.test(safeFilename.replace(uploadId + "-", ""))) {
    throw createError({ statusCode: 400, message: "Invalid filename" });
  }

  const storedPath = resolve(uploadDir, safeFilename);
  await writeFile(storedPath, buffer);

  let extractedText: string | null = null;
  let pdfWarning: string | undefined;

  try {
    extractedText = await parsePdf(buffer);
  } catch (err: any) {
    console.error(`[upload] PDF text extraction failed for file size ${buffer.length}: ${err?.message ?? err}`);
    pdfWarning = "PDF text extraction failed";
  }

  const detectedType = await detectUploadType(file.name, extractedText ?? "");

  await db.insert(uploads).values({
    id: uploadId,
    courseId: id,
    filename: file.name,
    type: detectedType,
    storedPath,
    extractedText,
  });

  if (pdfWarning) {
    return { uploadId, filename: file.name, type: detectedType, warning: pdfWarning };
  }

  return { uploadId, filename: file.name, type: detectedType };
});