Pinned Messages (#2081)

* add pinned room events hook

* room pinned message - WIP

* add room event hook

* fetch pinned messages before displaying

* use react-query in room event hook

* disable staleTime and gc to 1 hour in room event hook

* use room event hook in reply component

* render pinned messages

* add option to pin/unpin messages

* remove message base from message placeholders and add variant

* display message placeholder while loading pinned messages

* render pinned event error

* show no pinned message placeholder

* fix message placeholder flickering

src/app/hooks/useRoomEvent.ts

@@ -0,0 +1,56 @@
+import { MatrixEvent, Room } from 'matrix-js-sdk';
+import { useCallback, useMemo } from 'react';
+import to from 'await-to-js';
+import { CryptoBackend } from 'matrix-js-sdk/lib/common-crypto/CryptoBackend';
+import { useQuery } from '@tanstack/react-query';
+import { useMatrixClient } from './useMatrixClient';
+
+const useFetchEvent = (room: Room, eventId: string) => {
+  const mx = useMatrixClient();
+
+  const fetchEventCallback = useCallback(async () => {
+    const evt = await mx.fetchRoomEvent(room.roomId, eventId);
+    const mEvent = new MatrixEvent(evt);
+
+    if (mEvent.isEncrypted() && mx.getCrypto()) {
+      await to(mEvent.attemptDecryption(mx.getCrypto() as CryptoBackend));
+    }
+
+    return mEvent;
+  }, [mx, room.roomId, eventId]);
+
+  return fetchEventCallback;
+};
+
+/**
+ *
+ * @param room
+ * @param eventId
+ * @returns `MatrixEvent`, `undefined` means loading, `null` means failure
+ */
+export const useRoomEvent = (
+  room: Room,
+  eventId: string,
+  getLocally?: () => MatrixEvent | undefined
+) => {
+  const event = useMemo(() => {
+    if (getLocally) return getLocally();
+    return room.findEventById(eventId);
+  }, [room, eventId, getLocally]);
+
+  const fetchEvent = useFetchEvent(room, eventId);
+
+  const { data, error } = useQuery({
+    enabled: event === undefined,
+    queryKey: [room.roomId, eventId],
+    queryFn: fetchEvent,
+    staleTime: Infinity,
+    gcTime: 60 * 60 * 1000, // 1hour
+  });
+
+  if (event) return event;
+  if (data) return data;
+  if (error) return null;
+
+  return undefined;
+};