I’ve been attempting to upload a PDF to S3 using a Next.js route handler. However, I’m encountering a server error 500 when sending the post request. When I tried sending the request without the PDF file, it was successful. It seems that the code for uploading the PDF is the issue.

import { dbConnect } from "@/lib/db";
import { Program, User } from "@/models/userModel";
import { Upload } from "@aws-sdk/lib-storage";
import { NextRequest, NextResponse } from "next/server";
import { S3Client } from "@aws-sdk/client-s3";

const s3Client = new S3Client({
  region: process.env.AWS_S3_REGION,
  credentials: {
    accessKeyId: process.env.AWS_ACCESS_KEY_ID!,
    secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY!,
  },
});

async function uploadFileToS3(file: Buffer, fileName: string, userId: string) {
  const params = {
    Bucket: process.env.AWS_S3_BUCKET_NAME!,
    Key: `pdfs/${userId}-${Date.now()}-${fileName}`,
    Body: file,
    ContentType: "application/pdf",
  };

  try {
    const uploader = new Upload({
      client: s3Client,
      params: params,
    });

    const response = await uploader.done();
    console.log("Successfully uploaded file to S3", response);
    return response.Key;
  } catch (error) {
    console.error("Error uploading file to S3", error);
    throw error;
  }
}

// Add a user  program
export const POST = async (request: NextRequest) => {
  // Extract userId from query parameters
  const url = new URL(request.url);
  const userId = url.searchParams.get("userId");

  const { name, from, to, pdf } = await request.json();

  if (!name || !from || !to || !userId) {
    return NextResponse.json({
      message: "Missing required fields",
      status: 400,
    });
  }

  await dbConnect();

  // Validate the user ID
  const userExists = await User.findById(userId);
  if (!userExists) {
    return NextResponse.json({
      message: "User not found",
      status: 404,
    });
  }

  // Update DB
  try {
    let pdfUrl = null;
    if (pdf) {
      const buffer = Buffer.from(pdf, "base64");
      await uploadFileToS3(buffer, pdf.name, userId!);
      pdfUrl = `https://${process.env.AWS_S3_BUCKET_NAME}.s3.amazonaws.com/pdfs/${userId}-${pdf.name}`;
    }

    // Form a DB payload
    const newProgram = {
      name,
      from: new Date(from), // Ensure dates are properly formatted
      to: new Date(to),
      pdf: pdfUrl,
      user: userExists._id,
    };

    const createdProgram = await Program.create(newProgram);
    return NextResponse.json({
      message: "Program has been created",
      status: 201,
      program: createdProgram,
    });
  } catch (error) {
    console.error("Error creating program:", error);
    return NextResponse.json({
      error: error,
      // error: "An error occurred while creating the program. Please try again.",
      status: 500,
    });
  }
};

Upload images seems to work pretty well but pdf has some issues.