Use backend endpoint for attachment downloads

src/components/messageStream/utils/downloadFile.ts

@@ -1,3 +1,5 @@
+import { assetUrl } from "../../../api";
+
 type SaveFilePicker = (options?: {
   suggestedName?: string;
   types?: Array<{
@@ -20,6 +22,22 @@ type WindowWithSavePicker = Window & {
   showSaveFilePicker?: SaveFilePicker;
 };
 
+export function attachmentDownloadUrl(postId: string, attachmentId: string) {
+  return assetUrl(
+    `/api/posts/${encodeURIComponent(postId)}/attachments/${encodeURIComponent(
+      attachmentId,
+    )}/download`,
+  );
+}
+
+export async function downloadAttachment(
+  postId: string,
+  attachmentId: string,
+  filename: string,
+) {
+  return downloadFile(attachmentDownloadUrl(postId, attachmentId), filename);
+}
+
 export async function downloadFile(url: string, filename: string) {
   const res = await fetch(url, { credentials: "include" });
   if (!res.ok) throw new Error(await res.text());