Element Call: Send rtc.decline event when incoming call is declined (#4499)

ElementX/Sources/Services/ElementCall/ElementCallService.swift

@@ -16,6 +16,7 @@ class ElementCallService: NSObject, ElementCallServiceProtocol, PKPushRegistryDe
     private struct CallID: Equatable {
         let callKitID: UUID
         let roomID: String
+        let rtcNotificationID: String?
     }
     
     private let pushRegistry: PKPushRegistry
@@ -93,7 +94,7 @@ class ElementCallService: NSObject, ElementCallServiceProtocol, PKPushRegistryDe
         let callID = if let incomingCallID, incomingCallID.roomID == roomID {
             incomingCallID
         } else {
-            CallID(callKitID: UUID(), roomID: roomID)
+            CallID(callKitID: UUID(), roomID: roomID, rtcNotificationID: nil)
         }
         
         incomingCallID = nil
@@ -146,12 +147,17 @@ class ElementCallService: NSObject, ElementCallServiceProtocol, PKPushRegistryDe
             return
         }
         
+        guard let rtcNotificationID = payload.dictionaryPayload[ElementCallServiceNotificationKey.rtcNotifyEventID.rawValue] as? String else {
+            MXLog.error("Something went wrong, missing rtc notification event identifier for incoming voip call: \(payload)")
+            return
+        }
+        
         guard ongoingCallID?.roomID != roomID else {
             MXLog.warning("Call already ongoing for room \(roomID), ignoring incoming push")
             return
         }
         
-        let callID = CallID(callKitID: UUID(), roomID: roomID)
+        let callID = CallID(callKitID: UUID(), roomID: roomID, rtcNotificationID: rtcNotificationID)
         incomingCallID = callID
         
         let roomDisplayName = payload.dictionaryPayload[ElementCallServiceNotificationKey.roomDisplayName.rawValue] as? String
@@ -253,6 +259,12 @@ class ElementCallService: NSObject, ElementCallServiceProtocol, PKPushRegistryDe
             actionsSubject.send(.endCall(roomID: ongoingCallID.roomID))
         }
         
+        if let incomingCallID {
+            Task {
+                await sendDeclineCallEvent(incomingCallID)
+            }
+        }
+        
         tearDownCallSession(sendEndCallAction: false)
         
         action.fulfill()
@@ -274,6 +286,25 @@ class ElementCallService: NSObject, ElementCallServiceProtocol, PKPushRegistryDe
         ongoingCallID = nil
     }
     
+    private func sendDeclineCallEvent(_ incomingCallID: CallID) async {
+        guard let rtcNotificationID = incomingCallID.rtcNotificationID else {
+            MXLog.info("No rtc notification event to decline.")
+            return
+        }
+        
+        guard let clientProxy else {
+            MXLog.warning("A ClientProxy is needed to fetch the room.")
+            return
+        }
+        
+        guard case let .joined(roomProxy) = await clientProxy.roomForIdentifier(incomingCallID.roomID) else {
+            MXLog.warning("Failed to fetch a joined room for the incoming call.")
+            return
+        }
+        
+        _ = await roomProxy.declineCall(notificationID: rtcNotificationID)
+    }
+    
     private func observeIncomingCallRoomInfo() async {
         incomingCallRoomInfoCancellable = nil
         

ElementX/Sources/Services/ElementCall/ElementCallServiceConstants.swift

@@ -10,6 +10,9 @@ import Foundation
 enum ElementCallServiceNotificationKey: String {
     case roomID
     case roomDisplayName
+    /// When an incoming call is set to ring, there will be a `m.rtc.notification`event  (MSC4075).
+    /// Keep the notification event id as it is needed to decline calls (MSC4310).
+    case rtcNotifyEventID
 }
 
 let ElementCallServiceNotificationDiscardDelta = 15.0

ElementX/Sources/Services/Room/JoinedRoomProxy.swift

@@ -639,6 +639,16 @@ class JoinedRoomProxy: JoinedRoomProxyProtocol {
         ElementCallWidgetDriver(room: room, deviceID: deviceID)
     }
     
+    func declineCall(notificationID: String) async -> Result<Void, RoomProxyError> {
+        do {
+            try await room.declineCall(rtcNotificationEventId: notificationID)
+            return .success(())
+        } catch {
+            MXLog.error("Failed to decline rtc notification \(notificationID) with error: \(error)")
+            return .failure(.sdkError(error))
+        }
+    }
+    
     // MARK: - Permalinks
     
     func matrixToPermalink() async -> Result<URL, RoomProxyError> {

ElementX/Sources/Services/Room/RoomProxyProtocol.swift

@@ -169,6 +169,7 @@ protocol JoinedRoomProxyProtocol: RoomProxyProtocol {
     // MARK: - Element Call
     
     func elementCallWidgetDriver(deviceID: String) -> ElementCallWidgetDriverProtocol
+    func declineCall(notificationID: String) async -> Result<Void, RoomProxyError>
     
     // MARK: - Permalinks