Pre-signed S3 upload from the browser

                  import { S3Client, PutObjectCommand } from '@aws-sdk/client-s3';
import { getSignedUrl } from '@aws-sdk/s3-request-presigner';
import crypto from 'node:crypto';

const s3 = new S3Client({ region: process.env.AWS_REGION });

export async function presignUpload(userId: string, contentType: string) {
  if (!['image/png', 'image/jpeg', 'application/pdf'].includes(contentType)) {
    throw new Error('Unsupported content type');
  }

  const key = `uploads/${userId}/${crypto.randomUUID()}`;

  const cmd = new PutObjectCommand({
    Bucket: process.env.S3_BUCKET!,
    Key: key,
    ContentType: contentType
  });

  const url = await getSignedUrl(s3, cmd, { expiresIn: 60 });
  return { url, key };
}