ui: Treat thread fallback the same as a regular reply

… for now, until we add proper support for threads.

crates/matrix-sdk-ui/src/timeline/event_item/content.rs

@@ -170,19 +170,11 @@ impl Message {
 
         let in_reply_to = c.relates_to.and_then(|relation| match relation {
             message::Relation::Reply { in_reply_to } => {
-                let event_id = in_reply_to.event_id;
-                let event = timeline_items
-                    .iter()
-                    .filter_map(|it| it.as_event())
-                    .find(|it| it.event_id() == Some(&*event_id))
-                    .and_then(RepliedToEvent::from_timeline_item)
-                    .map(Box::new);
-
-                Some(InReplyToDetails {
-                    event_id,
-                    event: TimelineDetails::from_initial_value(event),
-                })
+                Some(InReplyToDetails::new(in_reply_to.event_id, timeline_items))
             }
+            message::Relation::Thread(thread) => thread
+                .in_reply_to
+                .map(|in_reply_to| InReplyToDetails::new(in_reply_to.event_id, timeline_items)),
             _ => None,
         });
 
@@ -272,6 +264,22 @@ pub struct InReplyToDetails {
     pub event: TimelineDetails<Box<RepliedToEvent>>,
 }
 
+impl InReplyToDetails {
+    pub fn new(
+        event_id: OwnedEventId,
+        timeline_items: &Vector<Arc<TimelineItem>>,
+    ) -> InReplyToDetails {
+        let event = timeline_items
+            .iter()
+            .filter_map(|it| it.as_event())
+            .find(|it| it.event_id() == Some(&*event_id))
+            .and_then(RepliedToEvent::from_timeline_item)
+            .map(Box::new);
+
+        InReplyToDetails { event_id, event: TimelineDetails::from_initial_value(event) }
+    }
+}
+
 /// An event that is replied to.
 #[derive(Clone, Debug)]
 pub struct RepliedToEvent {