Handle slave device message send failures

SignalServiceKit/src/Loki/Protocol/Multi Device/MultiDeviceProtocol.swift

@@ -41,7 +41,21 @@ public final class MultiDeviceProtocol : NSObject {
         return !(message is DeviceLinkMessage) && !message.thread.isGroupThread()
     }
 
-    private static func sendMessage(_ messageSend: OWSMessageSend, to destination: MultiDeviceDestination, in transaction: YapDatabaseReadTransaction) {
+    private static func copy(_ messageSend: OWSMessageSend, for destination: MultiDeviceDestination, with seal: Resolver<TSContactThread>) -> OWSMessageSend {
+        var recipient: SignalRecipient!
+        storage.dbReadConnection.read { transaction in
+            recipient = SignalRecipient.getOrBuildUnsavedRecipient(forRecipientId: destination.hexEncodedPublicKey, transaction: transaction)
+        }
+        // TODO: Apparently it's okay that the thread, sender certificate, etc. don't get changed?
+        return OWSMessageSend(message: messageSend.message, thread: messageSend.thread, recipient: recipient,
+            senderCertificate: messageSend.senderCertificate, udAccess: messageSend.udAccess, localNumber: messageSend.localNumber, success: {
+            seal.fulfill(messageSend.thread as! TSContactThread)
+        }, failure: { error in
+            seal.reject(error)
+        })
+    }
+
+    private static func sendMessage(_ messageSend: OWSMessageSend, to destination: MultiDeviceDestination, in transaction: YapDatabaseReadTransaction) -> Promise<Void> {
         let (promise, seal) = Promise<TSContactThread>.pending()
         let message = messageSend.message
         let messageSender = SSKEnvironment.shared.messageSender
@@ -50,7 +64,7 @@ public final class MultiDeviceProtocol : NSObject {
             let shouldSendAutoGeneratedFR = !thread.isContactFriend && !(message is FriendRequestMessage)
                 && !(message is SessionRequestMessage) && !isSessionResetMessage && !(message is TypingIndicatorMessage)
             if !shouldSendAutoGeneratedFR {
-                let messageSendCopy = messageSend.copy(with: destination)
+                let messageSendCopy = copy(messageSend, for: destination, with: seal)
                 messageSender.sendMessage(messageSendCopy)
             } else {
                 DispatchQueue.main.async {
@@ -76,6 +90,7 @@ public final class MultiDeviceProtocol : NSObject {
                 }
             }
         }
+        return promise.map { _ in }
     }
 
     @objc(sendMessageToDestinationAndLinkedDevices:in:)
@@ -92,16 +107,31 @@ public final class MultiDeviceProtocol : NSObject {
         print("[Loki] Sending \(type(of: message)) message using multi device routing.")
         let recipientID = messageSend.recipient.recipientId()
         getMultiDeviceDestinations(for: recipientID, in: transaction).done(on: OWSDispatch.sendingQueue()) { destinations in
+            var promises: [Promise<Void>] = []
             let masterDestination = destinations.first { $0.isMaster }
             if let masterDestination = masterDestination {
                 storage.dbReadConnection.read { transaction in
-                    sendMessage(messageSend, to: masterDestination, in: transaction)
+                    promises.append(sendMessage(messageSend, to: masterDestination, in: transaction))
                 }
             }
             let slaveDestinations = destinations.filter { !$0.isMaster }
             slaveDestinations.forEach { slaveDestination in
                 storage.dbReadConnection.read { transaction in
-                    sendMessage(messageSend, to: slaveDestination, in: transaction)
+                    promises.append(sendMessage(messageSend, to: slaveDestination, in: transaction))
+                }
+            }
+            when(resolved: promises).done(on: OWSDispatch.sendingQueue()) { results in
+                let errors = results.compactMap { result -> Error? in
+                    if case Result.rejected(let error) = result {
+                        return error
+                    } else {
+                        return nil
+                    }
+                }
+                if errors.isEmpty {
+                    messageSend.success()
+                } else {
+                    messageSend.failure(errors.first!)
                 }
             }
         }.catch(on: OWSDispatch.sendingQueue()) { error in

SignalServiceKit/src/Messages/OWSMessageSend.swift

@@ -93,14 +93,4 @@ public class OWSMessageSend: NSObject {
         // We "fail over" to non-UD sends after auth errors sending via UD.
         disableUD()
     }
-    
-    public func copy(with destination: MultiDeviceProtocol.MultiDeviceDestination) -> OWSMessageSend {
-        var recipient: SignalRecipient!
-        OWSPrimaryStorage.shared().dbReadConnection.read { transaction in
-            recipient = SignalRecipient.getOrBuildUnsavedRecipient(forRecipientId: destination.hexEncodedPublicKey, transaction: transaction)
-        }
-        let success = destination.isMaster ? self.success : { }
-        let failure = destination.isMaster ? self.failure : { _ in }
-        return OWSMessageSend(message: message, thread: thread, recipient: recipient, senderCertificate: senderCertificate, udAccess: udAccess, localNumber: localNumber, success: success, failure: failure)
-    }
 }