Ensure both session state and event existence when loading room data …

…source, fixes element-hq/element-ios#3290
matrix-org · Jun 2, 2020 · feafeb5 · feafeb5
1 parent 65a0975
commit feafeb5
Showing 1 changed file with 54 additions and 17 deletions.
diff --git a/MatrixKit/Models/Room/MXKRoomDataSource.m b/MatrixKit/Models/Room/MXKRoomDataSource.m
@@ -167,41 +167,78 @@ @implementation MXKRoomDataSource
 + (void)loadRoomDataSourceWithRoomId:(NSString*)roomId andMatrixSession:(MXSession*)mxSession onComplete:(void (^)(id roomDataSource))onComplete
 {
     MXKRoomDataSource *roomDataSource = [[self alloc] initWithRoomId:roomId andMatrixSession:mxSession];
+    [self ensureSessionStateForDataSource:roomDataSource initialEventId:nil andMatrixSession:mxSession onComplete:onComplete];
+}
+
++ (void)loadRoomDataSourceWithRoomId:(NSString*)roomId initialEventId:(NSString*)initialEventId andMatrixSession:(MXSession*)mxSession onComplete:(void (^)(id roomDataSource))onComplete
+{
+    MXKRoomDataSource *roomDataSource = [[self alloc] initWithRoomId:roomId initialEventId:initialEventId andMatrixSession:mxSession];
+    [self ensureSessionStateForDataSource:roomDataSource initialEventId:initialEventId andMatrixSession:mxSession onComplete:onComplete];
+}
+
++ (void)loadRoomDataSourceWithPeekingRoom:(MXPeekingRoom*)peekingRoom andInitialEventId:(NSString*)initialEventId onComplete:(void (^)(id roomDataSource))onComplete
+{
+    MXKRoomDataSource *roomDataSource = [[self alloc] initWithPeekingRoom:peekingRoom andInitialEventId:initialEventId];
+    [self finalizeRoomDataSource:roomDataSource onComplete:onComplete];
+}
+
+/// Ensure session state to be store data ready for the roomDataSource.
++ (void)ensureSessionStateForDataSource:(MXKRoomDataSource*)roomDataSource initialEventId:(NSString*)initialEventId andMatrixSession:(MXSession*)mxSession onComplete:(void (^)(id roomDataSource))onComplete
+{
     //  if store is not ready, roomDataSource.room will be nil. So onComplete block will never be called.
     //  In order to successfully fetch the room, we should wait for store to be ready.
     if (mxSession.state >= MXSessionStateStoreDataReady)
     {
-        if (!roomDataSource.room)
-        {
-            [self finalizeRoomDataSource:roomDataSource onComplete:onComplete];
-        }
+        [self ensureInitialEventExistenceForDataSource:roomDataSource initialEventId:initialEventId andMatrixSession:mxSession onComplete:onComplete];
     }
     else
     {
+        //  wait for session state to be store data ready
         id sessionStateObserver = nil;
         sessionStateObserver = [[NSNotificationCenter defaultCenter] addObserverForName:kMXSessionStateDidChangeNotification object:mxSession queue:nil usingBlock:^(NSNotification * _Nonnull note) {
             if (mxSession.state >= MXSessionStateStoreDataReady)
             {
                 [[NSNotificationCenter defaultCenter] removeObserver:sessionStateObserver];
-                if (!roomDataSource.room)
-                {
-                    [self finalizeRoomDataSource:roomDataSource onComplete:onComplete];
-                }
+                [self ensureInitialEventExistenceForDataSource:roomDataSource initialEventId:initialEventId andMatrixSession:mxSession onComplete:onComplete];
             }
         }];
     }
 }
 
-+ (void)loadRoomDataSourceWithRoomId:(NSString*)roomId initialEventId:(NSString*)initialEventId andMatrixSession:(MXSession*)mxSession onComplete:(void (^)(id roomDataSource))onComplete
+/// Ensure initial event existence for the roomDataSource.
++ (void)ensureInitialEventExistenceForDataSource:(MXKRoomDataSource*)roomDataSource initialEventId:(NSString*)initialEventId andMatrixSession:(MXSession*)mxSession onComplete:(void (^)(id roomDataSource))onComplete
 {
-    MXKRoomDataSource *roomDataSource = [[self alloc] initWithRoomId:roomId initialEventId:initialEventId andMatrixSession:mxSession];
-    [self finalizeRoomDataSource:roomDataSource onComplete:onComplete];
-}
-
-+ (void)loadRoomDataSourceWithPeekingRoom:(MXPeekingRoom*)peekingRoom andInitialEventId:(NSString*)initialEventId onComplete:(void (^)(id roomDataSource))onComplete
-{
-    MXKRoomDataSource *roomDataSource = [[self alloc] initWithPeekingRoom:peekingRoom andInitialEventId:initialEventId];
-    [self finalizeRoomDataSource:roomDataSource onComplete:onComplete];
+    if (roomDataSource.room)
+    {
+        //  already finalized
+        return;
+    }
+
+    if (initialEventId == nil)
+    {
+        //  if an initialEventId not provided, finalize
+        [self finalizeRoomDataSource:roomDataSource onComplete:onComplete];
+        return;
+    }
+
+    //  ensure event with id 'initialEventId' exists in the session store
+    if ([mxSession.store eventExistsWithEventId:initialEventId inRoom:roomDataSource.roomId])
+    {
+        [self finalizeRoomDataSource:roomDataSource onComplete:onComplete];
+    }
+    else
+    {
+        //  wait for the specific event to be existent
+        //  use kMXSessionDidSyncNotification here instead of MXSessionStateRunning, because session does not send this state update if it's already in this state
+        id syncObserver = nil;
+        syncObserver = [[NSNotificationCenter defaultCenter] addObserverForName:kMXSessionDidSyncNotification object:mxSession queue:nil usingBlock:^(NSNotification * _Nonnull note) {
+            if ([mxSession.store eventExistsWithEventId:initialEventId inRoom:roomDataSource.roomId])
+            {
+                [[NSNotificationCenter defaultCenter] removeObserver:syncObserver];
+                [self finalizeRoomDataSource:roomDataSource onComplete:onComplete];
+            }
+        }];
+    }
 }
 
 + (void)finalizeRoomDataSource:(MXKRoomDataSource*)roomDataSource onComplete:(void (^)(id roomDataSource))onComplete