Send delivery receipts.

SignalServiceKit/src/Messages/OWSDeliveryReceiptManager.m

@@ -110,11 +110,11 @@ NSString *const kDeliveryReceiptManagerCollection = @"kDeliveryReceiptManagerCol
                                               usingBlock:^(NSString *key, id object, BOOL *stop) {
                                                   NSString *recipientId = key;
                                                   NSSet<NSNumber *> *timestamps = object;
-                                                  deliveryReceiptMap[recipientId] = timestamps;
+                                                  deliveryReceiptMap[recipientId] = [timestamps copy];
                                               }];
     }];
 
-    BOOL didWork = NO;
+    NSMutableArray<AnyPromise *> *sendPromises = [NSMutableArray array];
 
     for (NSString *recipientId in deliveryReceiptMap) {
         NSSet<NSNumber *> *timestamps = deliveryReceiptMap[recipientId];
@@ -128,41 +128,47 @@ NSString *const kDeliveryReceiptManagerCollection = @"kDeliveryReceiptManagerCol
             [OWSReceiptsForSenderMessage deliveryReceiptsForSenderMessageWithThread:thread
                                                                   messageTimestamps:timestamps.allObjects];
 
-        [self.messageSender enqueueMessage:message
-            success:^{
-                OWSLogInfo(@"Successfully sent %lu delivery receipts to sender.", (unsigned long)timestamps.count);
-            }
-            failure:^(NSError *error) {
-                OWSLogError(@"Failed to send delivery receipts to sender with error: %@", error);
-            }];
+        AnyPromise *sendPromise = [AnyPromise promiseWithResolverBlock:^(PMKResolver resolve) {
+            [self.messageSender enqueueMessage:message
+                success:^{
+                    OWSLogInfo(@"Successfully sent %lu delivery receipts to sender.", (unsigned long)timestamps.count);
 
-        didWork = YES;
-    }
+                    [self dequeueDeliveryReceiptsWithRecipientId:recipientId timestamps:timestamps];
 
-    // Now that they've been processed, remove all enqueued delivery receipts.
-    //
-    // NOTE: we don't need to worry about race conditions; this
-    // collection will only be mutated on serialQueue.
-    [self.dbConnection readWriteWithBlock:^(YapDatabaseReadWriteTransaction *transaction) {
-        [transaction removeAllObjectsInCollection:kDeliveryReceiptManagerCollection];
-    }];
+                    // The value doesn't matter, we just need any non-NSError value.
+                    resolve(@(1));
+                }
+                failure:^(NSError *error) {
+                    OWSLogError(@"Failed to send delivery receipts to sender with error: %@", error);
 
-    if (!didWork) {
+                    resolve(error);
+                }];
+        }];
+        [sendPromises addObject:sendPromise];
+    }
+
+    if (sendPromises.count < 1) {
+        // No work to do; abort.
         self.isProcessing = NO;
         return;
     }
 
-    // Wait N seconds before processing delivery receipts again.
-    // This allows time for a batch to accumulate.
-    //
-    // We want a value high enough to allow us to effectively de-duplicate,
-    // delivery receipts without being so high that we risk not sending delivery
-    // receipts due to app exit.
-    const CGFloat kProcessingFrequencySeconds = 3.f;
-    dispatch_after(
-        dispatch_time(DISPATCH_TIME_NOW, (int64_t)(kProcessingFrequencySeconds * NSEC_PER_SEC)), self.serialQueue, ^{
-            [self process];
-        });
+    AnyPromise *completionPromise = PMKJoin(sendPromises);
+    completionPromise.always(^() {
+        // Wait N seconds before processing delivery receipts again.
+        // This allows time for a batch to accumulate.
+        //
+        // We want a value high enough to allow us to effectively de-duplicate,
+        // delivery receipts without being so high that we risk not sending delivery
+        // receipts due to app exit.
+        const CGFloat kProcessingFrequencySeconds = 3.f;
+        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(kProcessingFrequencySeconds * NSEC_PER_SEC)),
+            self.serialQueue,
+            ^{
+                [self process];
+            });
+    });
+    [completionPromise retainUntilComplete];
 }
 
 - (void)envelopeWasReceived:(SSKProtoEnvelope *)envelope {