Avoid empty participant list in voice chats

submodules/TelegramCallsUI/Sources/PresentationGroupCall.swift

@@ -742,9 +742,9 @@ public final class PresentationGroupCallImpl: PresentationGroupCall {
         if let initialCall = initialCall, let temporaryParticipantsContext = (self.accountContext.cachedGroupCallContexts as? AccountGroupCallContextCacheImpl)?.impl.syncWith({ impl in
             impl.get(account: accountContext.account, peerId: peerId, call: CachedChannelData.ActiveCall(id: initialCall.id, accessHash: initialCall.accessHash, title: initialCall.title))
         }) {
-            if let participantsContext = temporaryParticipantsContext.context.participantsContext, let immediateState = participantsContext.immediateState {
+            self.switchToTemporaryParticipantsContext(sourceContext: temporaryParticipantsContext.context.participantsContext, oldMyPeerId: self.joinAsPeerId)
-                self.switchToTemporaryParticipantsContext(sourceContext: participantsContext, initialState: immediateState, oldMyPeerId: self.joinAsPeerId)
+        } else {
-            }
+            self.switchToTemporaryParticipantsContext(sourceContext: nil, oldMyPeerId: self.joinAsPeerId)
         }
         
         self.removedChannelMembersDisposable = (accountContext.peerChannelMemberCategoriesContextsManager.removedChannelMembers
@@ -817,7 +817,7 @@ public final class PresentationGroupCallImpl: PresentationGroupCall {
         self.removedChannelMembersDisposable?.dispose()
     }
     
-    private func switchToTemporaryParticipantsContext(sourceContext: GroupCallParticipantsContext, initialState: GroupCallParticipantsContext.State, oldMyPeerId: PeerId) {
+    private func switchToTemporaryParticipantsContext(sourceContext: GroupCallParticipantsContext?, oldMyPeerId: PeerId) {
         let myPeerId = self.joinAsPeerId
         let myPeer = self.accountContext.account.postbox.transaction { transaction -> (Peer, CachedPeerData?)? in
             if let peer = transaction.getPeer(myPeerId) {
@@ -826,6 +826,7 @@ public final class PresentationGroupCallImpl: PresentationGroupCall {
                 return nil
             }
         }
+        if let sourceContext = sourceContext, let initialState = sourceContext.immediateState {
             let temporaryParticipantsContext = GroupCallParticipantsContext(account: self.account, peerId: self.peerId, myPeerId: myPeerId, id: sourceContext.id, accessHash: sourceContext.accessHash, state: initialState)
             self.temporaryParticipantsContext = temporaryParticipantsContext
             self.participantsContextStateDisposable.set((combineLatest(queue: .mainQueue(),
@@ -922,6 +923,69 @@ public final class PresentationGroupCallImpl: PresentationGroupCall {
                     strongSelf.invitedPeersValue = updatedInvitedPeers
                 }
             }))
+        } else {
+            self.temporaryParticipantsContext = nil
+            self.participantsContextStateDisposable.set((myPeer
+            |> deliverOnMainQueue
+            |> take(1)).start(next: { [weak self] myPeerAndCachedData in
+                guard let strongSelf = self else {
+                    return
+                }
+
+                var topParticipants: [GroupCallParticipantsContext.Participant] = []
+
+                var members = PresentationGroupCallMembers(
+                    participants: [],
+                    speakingParticipants: [],
+                    totalCount: 0,
+                    loadMoreToken: nil
+                )
+
+                var participants: [GroupCallParticipantsContext.Participant] = []
+
+                if !participants.contains(where: { $0.peer.id == myPeerId }) {
+                    if let (myPeer, cachedData) = myPeerAndCachedData {
+                        let about: String?
+                        if let cachedData = cachedData as? CachedUserData {
+                            about = cachedData.about
+                        } else if let cachedData = cachedData as? CachedUserData {
+                            about = cachedData.about
+                        } else {
+                            about = nil
+                        }
+                        participants.append(GroupCallParticipantsContext.Participant(
+                            peer: myPeer,
+                            ssrc: nil,
+                            jsonParams: nil,
+                            joinTimestamp: strongSelf.temporaryJoinTimestamp,
+                            raiseHandRating: nil,
+                            hasRaiseHand: false,
+                            activityTimestamp: strongSelf.temporaryActivityTimestamp,
+                            activityRank: strongSelf.temporaryActivityRank,
+                            muteState: GroupCallParticipantsContext.Participant.MuteState(canUnmute: true, mutedByYou: false),
+                            volume: nil,
+                            about: about
+                        ))
+                        participants.sort()
+                    }
+                }
+
+                for participant in participants {
+                    members.participants.append(participant)
+
+                    if topParticipants.count < 3 {
+                        topParticipants.append(participant)
+                    }
+                }
+
+                strongSelf.membersValue = members
+
+                var stateValue = strongSelf.stateValue
+                stateValue.myPeerId = strongSelf.joinAsPeerId
+
+                strongSelf.stateValue = stateValue
+            }))
+        }
     }
     
     private func updateSessionState(internalState: InternalState, audioSessionControl: ManagedAudioSessionControl?) {
@@ -1671,7 +1735,7 @@ public final class PresentationGroupCallImpl: PresentationGroupCall {
                         strongSelf.temporaryActivityRank = participant.activityRank
                     }
                 }
-                strongSelf.switchToTemporaryParticipantsContext(sourceContext: participantsContext, initialState: immediateState, oldMyPeerId: previousPeerId)
+                strongSelf.switchToTemporaryParticipantsContext(sourceContext: participantsContext, oldMyPeerId: previousPeerId)
             } else {
                 strongSelf.stateValue.myPeerId = peerId
             }