Port the feedback from the Java port (#1199)

* Port the feedback from the port

* Fix comment grammar

3 files changed, 24 insertions, 26 deletions

diff --git a/Firestore/Source/Core/FSTSyncEngine.mm b/Firestore/Source/Core/FSTSyncEngine.mm
index ca15e64..775f865 100644
--- a/Firestore/Source/Core/FSTSyncEngine.mm
+++ b/Firestore/Source/Core/FSTSyncEngine.mm
@@ -303,8 +303,7 @@ static const FSTListenSequenceNumber kIrrelevantSequenceNumber = -1;
     if (iter == self->_limboKeysByTarget.end()) {
       FSTQueryView *qv = self.queryViewsByTarget[targetID];
       FSTAssert(qv, @"Missing queryview for non-limbo query: %i", [targetID intValue]);
-      [remoteEvent filterUpdatesFromTargetChange:targetChange
-                               existingDocuments:qv.view.syncedDocuments];
+      [targetChange.mapping filterUpdatesUsingExistingKeys:qv.view.syncedDocuments];
     } else {
       [remoteEvent synthesizeDeleteForLimboTargetChange:targetChange key:iter->second];
     }
diff --git a/Firestore/Source/Remote/FSTRemoteEvent.h b/Firestore/Source/Remote/FSTRemoteEvent.h
index 322cb63..06099c7 100644
--- a/Firestore/Source/Remote/FSTRemoteEvent.h
+++ b/Firestore/Source/Remote/FSTRemoteEvent.h
@@ -43,6 +43,14 @@ NS_ASSUME_NONNULL_BEGIN
  * base class.
  */
 @interface FSTTargetMapping : NSObject
+
+/**
+ * Strips out mapping changes that aren't actually changes. That is, if the document already
+ * existed in the target, and is being added in the target, and this is not a reset, we can
+ * skip doing the work to associate the document with the target because it has already been done.
+ */
+- (void)filterUpdatesUsingExistingKeys:(FSTDocumentKeySet *)existingKeys;
+
 @end
 
 #pragma mark - FSTResetMapping
@@ -184,14 +192,6 @@ initWithSnapshotVersion:(firebase::firestore::model::SnapshotVersion)snapshotVer
 - (void)synthesizeDeleteForLimboTargetChange:(FSTTargetChange *)targetChange
                                          key:(const firebase::firestore::model::DocumentKey &)key;
 
-/**
- * Strips out mapping changes that aren't actually changes. That is, if the document already
- * existed in the target, and is being added in the target, and this is not a reset, we can
- * skip doing the work to associate the document with the target because it has already been done.
- */
-- (void)filterUpdatesFromTargetChange:(FSTTargetChange *)targetChange
-                    existingDocuments:(FSTDocumentKeySet *)existingDocuments;
-
 @end
 
 #pragma mark - FSTWatchChangeAggregator
diff --git a/Firestore/Source/Remote/FSTRemoteEvent.mm b/Firestore/Source/Remote/FSTRemoteEvent.mm
index 26c32a2..4f7e344 100644
--- a/Firestore/Source/Remote/FSTRemoteEvent.mm
+++ b/Firestore/Source/Remote/FSTRemoteEvent.mm
@@ -104,6 +104,10 @@ NS_ASSUME_NONNULL_BEGIN
   self.documents = [self.documents setByRemovingObject:documentKey];
 }
 
+- (void)filterUpdatesUsingExistingKeys:(FSTDocumentKeySet *)existingKeys {
+  // No-op. Resets are not filtered.
+}
+
 @end
 
 #pragma mark - FSTUpdateMapping
@@ -174,6 +178,16 @@ NS_ASSUME_NONNULL_BEGIN
   self.removedDocuments = [self.removedDocuments setByAddingObject:documentKey];
 }
 
+- (void)filterUpdatesUsingExistingKeys:(FSTDocumentKeySet *)existingKeys {
+  __block FSTDocumentKeySet *result = _addedDocuments;
+  [_addedDocuments enumerateObjectsUsingBlock:^(FSTDocumentKey *docKey, BOOL *stop) {
+    if ([existingKeys containsObject:docKey]) {
+      result = [result setByRemovingObject:docKey];
+    }
+  }];
+  _addedDocuments = result;
+}
+
 @end
 
 #pragma mark - FSTTargetChange
@@ -287,21 +301,6 @@ initWithSnapshotVersion:(SnapshotVersion)snapshotVersion
   return self;
 }
 
-- (void)filterUpdatesFromTargetChange:(FSTTargetChange *)targetChange
-                    existingDocuments:(FSTDocumentKeySet *)existingDocuments {
-  if ([targetChange.mapping isKindOfClass:[FSTUpdateMapping class]]) {
-    FSTUpdateMapping *update = (FSTUpdateMapping *)targetChange.mapping;
-    FSTDocumentKeySet *added = update.addedDocuments;
-    __block FSTDocumentKeySet *result = added;
-    [added enumerateObjectsUsingBlock:^(FSTDocumentKey *docKey, BOOL *stop) {
-      if ([existingDocuments containsObject:docKey]) {
-        result = [result setByRemovingObject:docKey];
-      }
-    }];
-    update.addedDocuments = result;
-  }
-}
-
 - (void)synthesizeDeleteForLimboTargetChange:(FSTTargetChange *)targetChange
                                          key:(const DocumentKey &)key {
   if (targetChange.currentStatusUpdate == FSTCurrentStatusUpdateMarkCurrent &&
@@ -320,7 +319,7 @@ initWithSnapshotVersion:(SnapshotVersion)snapshotVersion
     // However, if the document doesn't exist and the current marker arrives, the document is
     // not present in the snapshot and our normal view handling would consider the document to
     // remain in limbo indefinitely because there are no updates to the document. To avoid this,
-    // we specially handle this just this case here: synthesizing a delete.
+    // we specially handle this case here: synthesizing a delete.
     //
     // TODO(dimond): Ideally we would have an explicit lookup query instead resulting in an
     // explicit delete message and we could remove this special logic.