Fixes #3078 - Trim number of resolved alias vias and always default to a join button in the room preview screen

ElementX/Sources/Screens/JoinRoomScreen/JoinRoomScreenViewModel.swift

@@ -81,6 +81,7 @@ class JoinRoomScreenViewModel: JoinRoomScreenViewModelType, JoinRoomScreenViewMo
         
         defer {
             hideLoadingIndicator()
+            updateRoomDetails()
         }
         
         // Using only the preview API isn't enough as it's not capable
@@ -105,10 +106,6 @@ class JoinRoomScreenViewModel: JoinRoomScreenViewModelType, JoinRoomScreenViewMo
     }
     
     private func updateRoomDetails() {
-        if roomProxy == nil, roomPreviewDetails == nil {
-            return
-        }
-        
         let name = roomProxy?.name ?? roomPreviewDetails?.name
         state.roomDetails = JoinRoomScreenRoomDetails(name: name,
                                                       topic: roomProxy?.topic ?? roomPreviewDetails?.topic,
@@ -120,11 +117,6 @@ class JoinRoomScreenViewModel: JoinRoomScreenViewModelType, JoinRoomScreenViewMo
     }
     
     private func updateMode() {
-        if roomProxy == nil, roomPreviewDetails == nil {
-            state.mode = .unknown
-            return
-        }
-        
         if roomProxy?.isPublic ?? false || roomPreviewDetails?.isPublic ?? false {
             state.mode = .join
         } else if roomProxy?.membership == .invited || roomPreviewDetails?.isInvited ?? false {
@@ -132,7 +124,9 @@ class JoinRoomScreenViewModel: JoinRoomScreenViewModelType, JoinRoomScreenViewMo
         } else if roomPreviewDetails?.canKnock ?? false, allowKnocking { // Knocking is not supported yet, the flag is purely for preview tests.
             state.mode = .knock
         } else {
-            state.mode = .unknown
+            // If everything else fails fallback to showing the join button and
+            // letting the server figure it out.
+            state.mode = .join
         }
     }
     

ElementX/Sources/Services/Client/ClientProxy.swift

@@ -608,7 +608,14 @@ class ClientProxy: ClientProxyProtocol {
     
     func resolveRoomAlias(_ alias: String) async -> Result<ResolvedRoomAlias, ClientProxyError> {
         do {
-            return try await .success(client.resolveRoomAlias(roomAlias: alias))
+            let resolvedAlias = try await client.resolveRoomAlias(roomAlias: alias)
+            
+            // Resolving aliases is done through the directory/room API which returns too many / all known
+            // vias, which in turn results in invalid join requests. Trim them to something manageable
+            // https://github.com/element-hq/synapse/issues/17298
+            let limitedAlias = ResolvedRoomAlias(roomId: resolvedAlias.roomId, servers: Array(resolvedAlias.servers.prefix(50)))
+            
+            return .success(limitedAlias)
         } catch {
             MXLog.error("Failed resolving room alias: \(alias) with error: \(error)")
             return .failure(.sdkError(error))