perf: remove intermediate activities after stream ends

Author: OEvgeny

packages/api-graph/src/private/GraphProvider.tsx

@@ -76,17 +76,21 @@ function GraphProvider(props: GraphProviderProps) {
     };
   }, [graph, setOrderedActivityNodes]);
 
-  const orderedActivitiesState = useMemo<readonly [readonly WebChatActivity[]]>(
-    () =>
-      Object.freeze([
-        Object.freeze(
-          orderedActivityNodes.map(
-            node => node['urn:microsoft:webchat:direct-line-activity:raw-json'][0]['@value'] as WebChatActivity
-          )
-        )
-      ] as const),
-    [orderedActivityNodes]
-  );
+  const orderedActivitiesState = useMemo<readonly [readonly WebChatActivity[]]>(() => {
+    // Filter out stale graph nodes for activities no longer in Redux (e.g. pruned livestream revisions).
+    // The graph does not support deletion, so stale nodes linger after computeSortedActivities prunes them.
+    const { activities: storeActivities } = store.getState();
+    const validActivitySet = new Set<WebChatActivity>(storeActivities);
+    const activities: WebChatActivity[] = [];
+
+    for (const node of orderedActivityNodes) {
+      const activity = node['urn:microsoft:webchat:direct-line-activity:raw-json'][0]['@value'] as WebChatActivity;
+
+      validActivitySet.has(activity) && activities.push(activity);
+    }
+
+    return Object.freeze([Object.freeze(activities)] as const);
+  }, [orderedActivityNodes, store]);
 
   const context = useMemo<GraphContextType>(
     () =>

packages/core/src/reducers/activities/sort/private/computeSortedActivities.ts

@@ -1,4 +1,21 @@
-import type { Activity, State } from '../types';
+import type { Activity, LivestreamSessionMap, State } from '../types';
+
+function* yieldSessionActivities(
+  session: NonNullable<ReturnType<LivestreamSessionMap['get']>>,
+  activityMap: State['activityMap']
+): Generator<Activity> {
+  if (session.finalized) {
+    // After finalization, only yield the final revision — intermediate revisions are pruned.
+    // eslint-disable-next-line no-magic-numbers
+    const lastEntry = session.activities.at(-1);
+
+    lastEntry && (yield activityMap.get(lastEntry.activityLocalId)!.activity);
+  } else {
+    for (const activityEntry of session.activities) {
+      yield activityMap.get(activityEntry.activityLocalId)!.activity;
+    }
+  }
+}
 
 export default function computeSortedActivities(
   temporalState: Pick<State, 'activityMap' | 'howToGroupingMap' | 'livestreamSessionMap' | 'sortedChatHistoryList'>
@@ -20,17 +37,13 @@ export default function computeSortedActivities(
             } else {
               howToPartEntry.type satisfies 'livestream session';
 
-              for (const activityEntry of livestreamSessionMap.get(howToPartEntry.livestreamSessionId)!.activities) {
-                yield activityMap.get(activityEntry.activityLocalId)!.activity;
-              }
+              yield* yieldSessionActivities(livestreamSessionMap.get(howToPartEntry.livestreamSessionId)!, activityMap);
             }
           }
         } else {
           sortedEntry.type satisfies 'livestream session';
 
-          for (const activityEntry of livestreamSessionMap.get(sortedEntry.livestreamSessionId)!.activities) {
-            yield activityMap.get(activityEntry.activityLocalId)!.activity;
-          }
+          yield* yieldSessionActivities(livestreamSessionMap.get(sortedEntry.livestreamSessionId)!, activityMap);
         }
       }
     })()