Андрей Молодык

может кому нибудь пригодится мое решение:

файл api/upload/route.ts

import mime from "mime";
import { join } from "path";
import { stat, mkdir, writeFile } from "fs/promises";
import { NextRequest, NextResponse } from "next/server";

export async function POST(request: NextRequest) {
  const formData = await request.formData();
  const file = formData.get("file") as Blob | null;

  if (!file) {
    return NextResponse.json(
      { error: "File blob is required." },
      { status: 400 }
    );
  }
  const folder = formData.get("folder") as string;

  const relativeUploadDir = `/portfolio/${folder}`;
  const uploadDir = join(process.cwd(), "public/", relativeUploadDir);

  try {
    await stat(uploadDir);
  } catch (e: any) {
    if (e.code === "ENOENT") {
      await mkdir(uploadDir, { recursive: true });
    } else {
      console.error(
        "Ошибка при попытке создать каталог при загрузке файла\n",
        e
      );
      return NextResponse.json(
        { error: "Что-то пошло не так." },
        { status: 500 }
      );
    }
  }

  try {
    const folderArray = [];
    const formDataEntryValues = Array.from(formData.values()) as [];
    for (const formDataEntryValue of formDataEntryValues) {
      if (
        typeof formDataEntryValue === "object" &&
        "arrayBuffer" in formDataEntryValue
      ) {
        const file = formDataEntryValue as unknown as Blob;
        const buffer = Buffer.from(await file.arrayBuffer());
        await writeFile(`${uploadDir}/${file.name}`, buffer);
        folderArray.push(`${relativeUploadDir}/${file.name}`);
      }
    }
    return NextResponse.json({ filename: folderArray });
  } catch (e) {
    console.error("Error while trying to upload a file\n", e);
    return NextResponse.json({ error: "Что-то пошло не так" }, { status: 500 });
  }
}