[backport rh-test] refactor: centralize all download utils across app and apply special cloud-specific behavior (#6230)

Backport of #6188 to `rh-test`

Automatically created by backport workflow.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6230-backport-rh-test-refactor-centralize-all-download-utils-across-app-and-apply-special-c-2956d73d3650810d980fc30dfea02cc5)
by [Unito](https://www.unito.io)

Co-authored-by: Christian Byrne <cbyrne@comfy.org>

src/base/common/downloadUtil.ts

@@ -1,29 +1,64 @@
 /**
  * Utility functions for downloading files
  */
+import { isCloud } from '@/platform/distribution/types'
 
 // Constants
 const DEFAULT_DOWNLOAD_FILENAME = 'download.png'
 
+/**
+ * Trigger a download by creating a temporary anchor element
+ * @param href - The URL or blob URL to download
+ * @param filename - The filename to suggest to the browser
+ */
+function triggerLinkDownload(href: string, filename: string): void {
+  const link = document.createElement('a')
+  link.href = href
+  link.download = filename
+  link.style.display = 'none'
+
+  document.body.appendChild(link)
+  link.click()
+  document.body.removeChild(link)
+}
+
 /**
  * Download a file from a URL by creating a temporary anchor element
  * @param url - The URL of the file to download (must be a valid URL string)
  * @param filename - Optional filename override (will use URL filename or default if not provided)
  * @throws {Error} If the URL is invalid or empty
  */
-export const downloadFile = (url: string, filename?: string): void => {
+export function downloadFile(url: string, filename?: string): void {
   if (!url || typeof url !== 'string' || url.trim().length === 0) {
     throw new Error('Invalid URL provided for download')
   }
-  const link = document.createElement('a')
-  link.href = url
-  link.download =
+
+  const inferredFilename =
     filename || extractFilenameFromUrl(url) || DEFAULT_DOWNLOAD_FILENAME
 
-  // Trigger download
-  document.body.appendChild(link)
-  link.click()
-  document.body.removeChild(link)
+  if (isCloud) {
+    // Assets from cross-origin (e.g., GCS) cannot be downloaded this way
+    void downloadViaBlobFetch(url, inferredFilename).catch((error) => {
+      console.error('Failed to download file', error)
+    })
+    return
+  }
+
+  triggerLinkDownload(url, inferredFilename)
+}
+
+/**
+ * Download a Blob by creating a temporary object URL and anchor element
+ * @param filename - The filename to suggest to the browser
+ * @param blob - The Blob to download
+ */
+export function downloadBlob(filename: string, blob: Blob): void {
+  const url = URL.createObjectURL(blob)
+
+  triggerLinkDownload(url, filename)
+
+  // Revoke on the next microtask to give the browser time to start the download
+  queueMicrotask(() => URL.revokeObjectURL(url))
 }
 
 /**
@@ -39,3 +74,15 @@ const extractFilenameFromUrl = (url: string): string | null => {
     return null
   }
 }
+
+const downloadViaBlobFetch = async (
+  href: string,
+  filename: string
+): Promise<void> => {
+  const response = await fetch(href)
+  if (!response.ok) {
+    throw new Error(`Failed to fetch ${href}: ${response.status}`)
+  }
+  const blob = await response.blob()
+  downloadBlob(filename, blob)
+}