import { GetObjectCommand, S3Client } from "@aws-sdk/client-s3"
import { HttpRequest } from "@aws-sdk/protocol-http"
import { S3RequestPresigner, getSignedUrl } from "@aws-sdk/s3-request-presigner"
import { formatUrl } from "@aws-sdk/util-format-url"
async function getPresignedDownloadUrl(params: {
 bucket: string
 key: string
 customParam: string
 fileName?: string
 downloadUrlExpirationSec?: number
}): Promise<string> {
 const apiUrl = new URL(
 `https://${params.bucket}.s3.amazonaws.com/${params.key}`
 )
 const presigner = new S3RequestPresigner({
 ...s3Client.config,
 })
 const httpRequest = new HttpRequest({
 query: {
 custom_param: params.customParam,
 "response-content-disposition":
 params.fileName != null
 ? `attachment; filename=${params.fileName}`
 : "attachment",
 },
 hostname: apiUrl.hostname,
 method: "GET",
 path: apiUrl.pathname,
 })
 const signedRequest = await presigner.presign(httpRequest, {
 expiresIn: params.downloadUrlExpirationSec ?? 60,
 })
 const downloadUrl = formatUrl(signedRequest)
 return downloadUrl
}
const url = await getPresignedUrl({
 bucket: "test_bucket",
 customParam: "customParamValue",
 key: "path/to/object", // Error occurs if "=" is included.
 fileName: "name_of_download_file",
 })
console.log(url)