Attempt to fix background crash in a different way

SignalServiceKit/src/Loki/API/LokiAPI.swift

@@ -120,26 +120,27 @@ public final class LokiAPI : NSObject {
         }.map { Set($0) }.retryingIfNeeded(maxRetryCount: maxRetryCount)
     }
     
-    public static func getDestinations(for hexEncodedPublicKey: String) -> Promise<[Destination]> {
-        var result: Promise<[Destination]>!
+    public static func getDestinations(for hexEncodedPublicKey: String) -> Promise<Set<Destination>> {
+        var result: Promise<Set<Destination>>!
         storage.dbReadWriteConnection.readWrite { transaction in
             result = getDestinations(for: hexEncodedPublicKey, in: transaction)
         }
         return result
     }
     
-    public static func getDestinations(for hexEncodedPublicKey: String, in transaction: YapDatabaseReadWriteTransaction) -> Promise<[Destination]> {
+    public static func getDestinations(for hexEncodedPublicKey: String, in transaction: YapDatabaseReadWriteTransaction) -> Promise<Set<Destination>> {
         // All of this has to happen on DispatchQueue.global() due to the way OWSMessageManager works
-        let (promise, seal) = Promise<[Destination]>.pending()
+        let (promise, seal) = Promise<Set<Destination>>.pending()
         func getDestinations(in transaction: YapDatabaseReadTransaction? = nil) {
             func getDestinationsInternal(in transaction: YapDatabaseReadTransaction) {
-                var destinations: [Destination] = []
-                let masterHexEncodedPublicKey = storage.getMasterHexEncodedPublicKey(for: hexEncodedPublicKey, in: transaction) ?? hexEncodedPublicKey
-                let masterDestination = Destination(hexEncodedPublicKey: masterHexEncodedPublicKey, kind: .master)
-                destinations.append(masterDestination)
-                let deviceLinks = storage.getDeviceLinks(for: masterHexEncodedPublicKey, in: transaction)
-                let slaveDestinations = deviceLinks.map { Destination(hexEncodedPublicKey: $0.slave.hexEncodedPublicKey, kind: .slave) }
-                destinations.append(contentsOf: slaveDestinations)
+                let query = YapDatabaseQuery(string: "WHERE \(DeviceLinkIndex.slaveHexEncodedPublicKey) = ? OR \(DeviceLinkIndex.masterHexEncodedPublicKey) = ?", parameters: [ hexEncodedPublicKey, hexEncodedPublicKey ])
+                let deviceLinks = Set(DeviceLinkIndex.getDeviceLinks(for: query, in: transaction))
+                var destinations = Set(deviceLinks.flatMap {
+                    return [ Destination(hexEncodedPublicKey: $0.master.hexEncodedPublicKey, kind: .master), Destination(hexEncodedPublicKey: $0.slave.hexEncodedPublicKey, kind: .slave) ]
+                })
+                if destinations.isEmpty {
+                    destinations.insert(Destination(hexEncodedPublicKey: hexEncodedPublicKey, kind: .master))
+                }
                 seal.fulfill(destinations)
             }
             if let transaction = transaction, transaction.connection.pendingTransactionCount != 0 {

SignalServiceKit/src/Loki/Database/OWSPrimaryStorage+Loki.swift

@@ -29,8 +29,13 @@ public extension OWSPrimaryStorage {
     }
     
     public func getDeviceLinks(for masterHexEncodedPublicKey: String, in transaction: YapDatabaseReadTransaction) -> Set<DeviceLink> {
-        let query = YapDatabaseQuery(string: "WHERE \(DeviceLinkIndex.masterHexEncodedPublicKey) = ?", parameters: [ masterHexEncodedPublicKey ])
-        return Set(DeviceLinkIndex.getDeviceLinks(for: query, in: transaction))
+        let collection = getDeviceLinkCollection(for: masterHexEncodedPublicKey)
+        var result: Set<DeviceLink> = []
+        transaction.enumerateRows(inCollection: collection) { _, object, _, _ in
+            guard let deviceLink = object as? DeviceLink else { return }
+            result.insert(deviceLink)
+        }
+        return result
     }
     
     public func getDeviceLink(for slaveHexEncodedPublicKey: String, in transaction: YapDatabaseReadTransaction) -> DeviceLink? {

SignalServiceKit/src/Messages/OWSMessageSender.m

@@ -995,11 +995,11 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
         BOOL isFriendRequestMessage = [message isKindOfClass:LKFriendRequestMessage.class];
         BOOL isSessionRequestMessage = [message isKindOfClass:LKSessionRequestMessage.class];
         [[LKAPI getDestinationsFor:contactID]
-        .thenOn(OWSDispatch.sendingQueue, ^(NSArray<LKDestination *> *destinations) {
+        .thenOn(OWSDispatch.sendingQueue, ^(NSSet<LKDestination *> *destinations) {
             // Get master destination
             LKDestination *masterDestination = [destinations filtered:^BOOL(LKDestination *destination) {
                 return [destination.kind isEqual:@"master"];
-            }].firstObject;
+            }].allObjects.firstObject;
             // Send to master destination
             if (masterDestination != nil) {
                 TSContactThread *thread = [TSContactThread getOrCreateThreadWithContactId:masterDestination.hexEncodedPublicKey];
@@ -1012,7 +1012,7 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
                 }
             }
             // Get slave destinations
-            NSArray *slaveDestinations = [destinations filtered:^BOOL(LKDestination *destination) {
+            NSSet *slaveDestinations = [destinations filtered:^BOOL(LKDestination *destination) {
                 return [destination.kind isEqual:@"slave"];
             }];
             // Send to slave destinations (using a best attempt approach (i.e. ignoring the message send result) for now)