WIP gappy sync handling

Author: hughns

src/utils/matrix.ts

@@ -9,8 +9,10 @@ import { IndexedDBStore } from "matrix-js-sdk/src/store/indexeddb";
 import { MemoryStore } from "matrix-js-sdk/src/store/memory";
 import {
   createClient,
+  Filter,
   ICreateClientOpts,
   Preset,
+  RoomEvent,
   Visibility,
 } from "matrix-js-sdk/src/matrix";
 import { ClientEvent } from "matrix-js-sdk/src/client";
@@ -126,6 +128,10 @@ export async function initClient(
     store: new MemoryStore(),
   });
 
+  client.on(RoomEvent.TimelineReset, () => {
+    logger.warn("Received TimelineReset indicating limited sync response");
+  });
+
   // In case of logging in a new matrix account but there is still crypto local store. This is needed for:
   // - We lost the auth tokens and cannot restore the client resulting in registering a new user.
   // - We start the sign in flow but are registered with a guest user. (It should additionally log out the guest before)
@@ -165,7 +171,20 @@ export async function initClient(
   // Otherwise, a sync may complete before the listener gets applied,
   // and we will miss it.
   const syncPromise = waitForSync(client);
-  await client.startClient({ clientWellKnownPollPeriod: 60 * 10 });
+  await client.startClient({
+    clientWellKnownPollPeriod: 60 * 10,
+    // TODO: ask for a high limit to avoid gappy syncs
+    filter: Filter.fromJson(undefined, "element-call", {
+      room: {
+        timeline: {
+          limit: 1,
+        },
+      },
+    }),
+    // we only ask for 1 past message as we really only care about future messages
+    // n.b. past reactions are then not visible
+    initialSyncLimit: 1,
+  });
   await syncPromise;
 
   return client;