Mark stories as viewed if we have a view sync during modifyTargetMessage

ts/models/messages.ts

@@ -3021,10 +3021,27 @@ export class MessageModel extends window.Backbone.Model<MessageAttributesType> {
       }
     }
 
-    if (
+    if (isStory(message.attributes)) {
-      isStory(message.attributes) &&
+      const viewSyncs = ViewSyncs.getSingleton().forMessage(message);
-      !message.get('expirationStartTimestamp')
+
-    ) {
+      if (viewSyncs.length !== 0) {
+        message.set({
+          readStatus: ReadStatus.Viewed,
+          seenStatus: SeenStatus.Seen,
+        });
+        changed = true;
+
+        const markReadAt = Math.min(
+          Date.now(),
+          ...viewSyncs.map(sync => sync.get('viewedAt'))
+        );
+        this.pendingMarkRead = Math.min(
+          this.pendingMarkRead ?? Date.now(),
+          markReadAt
+        );
+      }
+
+      if (!message.get('expirationStartTimestamp')) {
         message.set(
           'expirationStartTimestamp',
           Math.min(
@@ -3034,6 +3051,7 @@ export class MessageModel extends window.Backbone.Model<MessageAttributesType> {
         );
         changed = true;
       }
+    }
 
     // Does this message have any pending, previously-received associated reactions?
     const reactions = Reactions.getSingleton().forMessage(message);