Fix thread events ordering

MatrixSDK/Data/EventTimeline/Thread/MXThreadEventTimeline.swift

@@ -136,6 +136,11 @@ public class MXThreadEventTimeline: NSObject, MXEventTimeline {
 
         // Reset store pagination
         storeMessagesEnumerator = store.messagesEnumerator(forRoom: thread.roomId)
+
+        if isLiveTimeline {
+            hasReachedHomeServerBackwardsPaginationEnd = false
+            hasReachedHomeServerForwardsPaginationEnd = false
+        }
     }
 
     public func __resetPaginationAroundInitialEvent(withLimit limit: UInt,
@@ -376,33 +381,38 @@ public class MXThreadEventTimeline: NSObject, MXEventTimeline {
     //  MARK: - Private
 
     private func processPaginationResponse(_ response: MXAggregationPaginatedResponse, direction: MXTimelineDirection) {
-        let dispatchGroup = DispatchGroup()
+        MXLog.debug("[MXThreadEventTimeline][\(self.timelineId)] processPaginationResponse: \(response.chunk.count) messages from the server, direction: \(direction)")
 
-        dispatchGroup.enter()
         decryptEvents(response.chunk) {
+            //  process chunk first
             for event in response.chunk {
                 self.addEvent(event, direction: direction, fromStore: false)
             }
-            dispatchGroup.leave()
-        }
-        if let rootEvent = response.originalEvent, response.nextBatch == nil {
-            dispatchGroup.enter()
-            decryptEvents([rootEvent]) {
-                self.addEvent(rootEvent, direction: direction, fromStore: false)
-                dispatchGroup.leave()
+
+            let updatePaginationInfo = {
+                switch direction {
+                case .backwards:
+                    self.backwardsPaginationToken = response.nextBatch
+                    self.hasReachedHomeServerBackwardsPaginationEnd = response.nextBatch == nil
+                    MXLog.debug("[MXThreadEventTimeline][\(self.timelineId)] processPaginationResponse: hasReachedHomeServerBackwardsPaginationEnd: \(self.hasReachedHomeServerBackwardsPaginationEnd)")
+                case .forwards:
+                    self.forwardsPaginationToken = response.nextBatch
+                    self.hasReachedHomeServerForwardsPaginationEnd = response.nextBatch == nil
+                    MXLog.debug("[MXThreadEventTimeline][\(self.timelineId)] processPaginationResponse: hasReachedHomeServerForwardsPaginationEnd: \(self.hasReachedHomeServerForwardsPaginationEnd)")
+                @unknown default:
+                    fatalError("[MXThreadEventTimeline][\(self.timelineId)] processPaginationResponse: Unknown direction")
+                }
             }
-        }
 
-        dispatchGroup.notify(queue: .main) {
-            switch direction {
-            case .backwards:
-                self.backwardsPaginationToken = response.nextBatch
-                self.hasReachedHomeServerBackwardsPaginationEnd = response.nextBatch == nil
-            case .forwards:
-                self.forwardsPaginationToken = response.nextBatch
-                self.hasReachedHomeServerForwardsPaginationEnd = response.nextBatch == nil
-            @unknown default:
-                fatalError("[MXThreadEventTimeline][\(self.timelineId)] processPaginationResponse: Unknown direction")
+            //  then process the root if there is no more messages in server
+
+            if let rootEvent = response.originalEvent, response.nextBatch == nil {
+                self.decryptEvents([rootEvent]) {
+                    self.addEvent(rootEvent, direction: direction, fromStore: false)
+                    updatePaginationInfo()
+                }
+            } else {
+                updatePaginationInfo()
             }
         }
     }
@@ -435,13 +445,8 @@ public class MXThreadEventTimeline: NSObject, MXEventTimeline {
         if fromStore {
             notifyListeners(event, direction: direction)
         } else {
-            if let threadingService = thread.session?.threadingService {
-                threadingService.handleEvent(event, direction: direction) { handled in
-                    if handled {
-                        self.notifyListeners(event, direction: direction)
-                    }
-                }
-            }
+            self.notifyListeners(event, direction: direction)
+            thread.session?.threadingService.handleEvent(event, direction: direction, completion: nil)
 
             if !isLiveTimeline {
                 store.storeEvent(forRoom: thread.roomId, event: event, direction: direction)

changelog.d/5840.bugfix

@@ -0,0 +1 @@
+MXThreadEventTimeline: Fix processing order of thread events & fix empty thread screen issue.