feat: auto-download YouTube channel images on create/update

Adds channelThumbnailUrl field to store YouTube API URL.
afterChange hook downloads image to Payload Media when branding.logo is empty.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/collections/YouTubeChannels.ts

@@ -2,6 +2,7 @@
 
 import type { CollectionConfig } from 'payload'
 import { isYouTubeManager, hasYouTubeAccess } from '../lib/youtubeAccess'
+import { downloadChannelImage } from '../hooks/youtubeChannels/downloadChannelImage'
 
 /**
  * YouTubeChannels Collection
@@ -27,6 +28,9 @@ export const YouTubeChannels: CollectionConfig = {
     update: isYouTubeManager,
     delete: isYouTubeManager,
   },
+  hooks: {
+    afterChange: [downloadChannelImage],
+  },
   fields: [
     {
       name: 'name',
@@ -108,6 +112,16 @@ export const YouTubeChannels: CollectionConfig = {
         position: 'sidebar',
       },
     },
+    {
+      name: 'channelThumbnailUrl',
+      type: 'text',
+      label: 'Kanal-Thumbnail URL',
+      admin: {
+        readOnly: true,
+        description: 'Profil-Thumbnail URL von YouTube (automatisch befüllt)',
+        position: 'sidebar',
+      },
+    },
     // Branding
     {
       name: 'branding',

src/hooks/youtubeChannels/downloadChannelImage.ts

@@ -0,0 +1,41 @@
+import type { CollectionAfterChangeHook } from 'payload'
+import { downloadAndUploadImage } from '../../lib/utils/media-download'
+
+/**
+ * After a YouTubeChannels document is created or updated,
+ * automatically download the channel profile image if the branding.logo field is empty
+ * and a channelThumbnailUrl is available.
+ */
+export const downloadChannelImage: CollectionAfterChangeHook = async ({ doc, req }) => {
+  // Skip if logo already exists
+  if (doc.branding?.logo) return doc
+
+  // Need channelThumbnailUrl (set from YouTube API or manually)
+  const thumbnailUrl = doc.channelThumbnailUrl
+  if (!thumbnailUrl) return doc
+
+  const channelId = doc.youtubeChannelId
+  if (!channelId) return doc
+
+  const filename = `yt-channel-${channelId}.jpg`
+  const tenantId = typeof doc.tenant === 'object' ? doc.tenant?.id : doc.tenant
+
+  const mediaId = await downloadAndUploadImage(req.payload, {
+    url: thumbnailUrl,
+    filename,
+    alt: doc.name ? `Kanal: ${typeof doc.name === 'string' ? doc.name : doc.name?.de || channelId}` : `YouTube Channel ${channelId}`,
+    tenantId: tenantId || undefined,
+  })
+
+  if (mediaId) {
+    await req.payload.update({
+      collection: 'youtube-channels',
+      id: doc.id,
+      data: { branding: { ...(doc.branding || {}), logo: mediaId } },
+      depth: 0,
+    })
+    console.log(`[yt-thumbnail] Auto-downloaded channel image for ${channelId} (media: ${mediaId})`)
+  }
+
+  return doc
+}