C++ migration: port FSTOnlineStateTracker (#2325)

Author: var-const

Firestore/Example/Tests/Integration/FSTDatastoreTests.mm

@@ -55,6 +55,7 @@
 using firebase::firestore::model::DocumentKey;
 using firebase::firestore::model::DocumentKeySet;
 using firebase::firestore::model::Precondition;
+using firebase::firestore::model::OnlineState;
 using firebase::firestore::model::TargetId;
 using firebase::firestore::remote::Datastore;
 using firebase::firestore::remote::GrpcConnection;
@@ -186,7 +187,8 @@ - (void)setUp {
 
   _remoteStore = [[FSTRemoteStore alloc] initWithLocalStore:_localStore
                                                   datastore:_datastore
-                                                workerQueue:_testWorkerQueue.get()];
+                                                workerQueue:_testWorkerQueue.get()
+                                         onlineStateHandler:[](OnlineState) {}];
 
   _testWorkerQueue->Enqueue([=] { [_remoteStore start]; });
 }

Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.h

@@ -86,7 +86,7 @@ typedef std::unordered_map<firebase::firestore::auth::User,
  *
  * Each method on the driver injects a different event into the system.
  */
-@interface FSTSyncEngineTestDriver : NSObject <FSTOnlineStateDelegate>
+@interface FSTSyncEngineTestDriver : NSObject
 
 /**
  * Initializes the underlying FSTSyncEngine with the given local persistence implementation and

Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.mm

@@ -153,18 +153,21 @@ - (instancetype)initWithPersistence:(id<FSTPersistence>)persistence
 
     _datastore =
         std::make_shared<MockDatastore>(_databaseInfo, _workerQueue.get(), &_credentialProvider);
-    _remoteStore = [[FSTRemoteStore alloc] initWithLocalStore:_localStore
-                                                    datastore:_datastore
-                                                  workerQueue:_workerQueue.get()];
+    _remoteStore =
+        [[FSTRemoteStore alloc] initWithLocalStore:_localStore
+                                         datastore:_datastore
+                                       workerQueue:_workerQueue.get()
+                                onlineStateHandler:[self](OnlineState onlineState) {
+                                  [self.syncEngine applyChangedOnlineState:onlineState];
+                                  [self.eventManager applyChangedOnlineState:onlineState];
+                                }];
 
     _syncEngine = [[FSTSyncEngine alloc] initWithLocalStore:_localStore
                                                 remoteStore:_remoteStore
                                                 initialUser:initialUser];
     _remoteStore.syncEngine = _syncEngine;
     _eventManager = [FSTEventManager eventManagerWithSyncEngine:_syncEngine];
 
-    _remoteStore.onlineStateDelegate = self;
-
     // Set up internal event tracking for the spec tests.
     NSMutableArray<FSTQueryEvent *> *events = [NSMutableArray array];
     _eventHandler = ^(FSTQueryEvent *e) {
@@ -203,11 +206,6 @@ - (void)drainQueue {
   return _currentUser;
 }
 
-- (void)applyChangedOnlineState:(OnlineState)onlineState {
-  [self.syncEngine applyChangedOnlineState:onlineState];
-  [self.eventManager applyChangedOnlineState:onlineState];
-}
-
 - (void)start {
   _workerQueue->EnqueueBlocking([&] {
     [self.localStore start];

Firestore/Source/Core/FSTEventManager.h

@@ -75,7 +75,7 @@ NS_ASSUME_NONNULL_BEGIN
  * EventManager is responsible for mapping queries to query event emitters. It handles "fan-out."
  * (Identical queries will re-use the same watch on the backend.)
  */
-@interface FSTEventManager : NSObject <FSTOnlineStateDelegate>
+@interface FSTEventManager : NSObject
 
 + (instancetype)eventManagerWithSyncEngine:(FSTSyncEngine *)syncEngine;
 
@@ -84,6 +84,8 @@ NS_ASSUME_NONNULL_BEGIN
 - (firebase::firestore::model::TargetId)addListener:(FSTQueryListener *)listener;
 - (void)removeListener:(FSTQueryListener *)listener;
 
+- (void)applyChangedOnlineState:(firebase::firestore::model::OnlineState)onlineState;
+
 @end
 
 NS_ASSUME_NONNULL_END

Firestore/Source/Core/FSTFirestoreClient.h

@@ -49,7 +49,7 @@ NS_ASSUME_NONNULL_BEGIN
  * SDK architecture. It is responsible for creating the worker queue that is shared by all of the
  * other components in the system.
  */
-@interface FSTFirestoreClient : NSObject <FSTOnlineStateDelegate>
+@interface FSTFirestoreClient : NSObject
 
 /**
  * Creates and returns a FSTFirestoreClient with the given parameters.

Firestore/Source/Core/FSTFirestoreClient.mm

@@ -228,7 +228,10 @@ - (void)initializeWithUser:(const User &)user settings:(FIRFirestoreSettings *)s
 
   _remoteStore = [[FSTRemoteStore alloc] initWithLocalStore:_localStore
                                                   datastore:std::move(datastore)
-                                                workerQueue:_workerQueue.get()];
+                                                workerQueue:_workerQueue.get()
+                                         onlineStateHandler:[self](OnlineState onlineState) {
+                                           [self.syncEngine applyChangedOnlineState:onlineState];
+                                         }];
 
   _syncEngine = [[FSTSyncEngine alloc] initWithLocalStore:_localStore
                                               remoteStore:_remoteStore
@@ -239,8 +242,6 @@ - (void)initializeWithUser:(const User &)user settings:(FIRFirestoreSettings *)s
   // Setup wiring for remote store.
   _remoteStore.syncEngine = _syncEngine;
 
-  _remoteStore.onlineStateDelegate = self;
-
   // NOTE: RemoteStore depends on LocalStore (for persisting stream tokens, refilling mutation
   // queue, etc.) so must be started after LocalStore.
   [_localStore start];
@@ -267,10 +268,6 @@ - (void)credentialDidChangeWithUser:(const User &)user {
   [self.syncEngine credentialDidChangeWithUser:user];
 }
 
-- (void)applyChangedOnlineState:(OnlineState)onlineState {
-  [self.syncEngine applyChangedOnlineState:onlineState];
-}
-
 - (void)disableNetworkWithCompletion:(nullable FSTVoidErrorBlock)completion {
   _workerQueue->Enqueue([self, completion] {
     [self.remoteStore disableNetwork];