add predicate to convert alertdata to legacy endpoint event

x-pack/plugins/endpoint/public/applications/endpoint/store/alerts/selectors.ts

@@ -15,7 +15,7 @@ import {
   AlertsAPIQueryParams,
   CreateStructuredSelector,
 } from '../../types';
-import { Immutable, LegacyEndpointEvent } from '../../../../../common/types';
+import { Immutable, LegacyEndpointEvent, AlertEvent } from '../../../../../common/types';
 
 const createStructuredSelector: CreateStructuredSelector = createStructuredSelectorWithBadType;
 /**
@@ -93,14 +93,23 @@ export const hasSelectedAlert: (state: AlertListState) => boolean = createSelect
   ({ selected_alert: selectedAlert }) => selectedAlert !== undefined
 );
 
+/**
+ * Determine if the alert event is most likely compatible with LegacyEndpointEvent.
+ */
+function isAlertEventLegacyEndpointEvent(event: { endgame?: {} }): event is LegacyEndpointEvent {
+  return event.endgame !== undefined && 'unique_pid' in event.endgame;
+}
+
 export const selectedEvent: (
   state: AlertListState
 ) => LegacyEndpointEvent | undefined = createSelector(
   uiQueryParams,
   alertListData,
   ({ selected_alert: selectedAlert }, alertList) => {
-    return (alertList.find(
-      alert => alert.event.id === selectedAlert
-    ) as unknown) as LegacyEndpointEvent;
+    const found = alertList.find(alert => alert.event.id === selectedAlert);
+    if (!found) {
+      return found;
+    }
+    return isAlertEventLegacyEndpointEvent(found) ? found : undefined;
   }
 );