replacing Auth by C++ auth implementation (#802)

* lazy replacing FST(Firebase)CredentialsProvider by (Firebase)CredentialsProvider

* lazy replacing FSTUser by User

* adding error-code parameter to TokenListener

* actually use const user& instead of pointer; also add an error util

* add HashUser and pass into the unordered_map

* use User in test

* use c++ CredentialsProvider and subclass in test

* fix unit test

* use explicit capture in lambda instead of capture all by reference

* cache currentUser explicitly when reset sync engineer test driver

* objc object should be captured by value in lambda

* replacing Auth/FSTUser by C++ auth implementation

* address changes

* replacing FSTGetTokenResult by C++ Token implementation

* address changes

* fix unintentional change in merging

* patch the change in objc Auth up-stream

* somehow, the lambda-version of set-user-change-listener does not work... fallback to block

* address changes

* fix another const& v.s. dispatch bug

* fix more const& v.s. dispatch bug  zxu123 committed

* fix a bad sync line

* address changes

* address change

* address change

* fix upstream change from merge

* fix upstream changes

* Suggested fixes for cpp/port_auth (#846)

* Get rid of MockDatastore factory

This avoids the need to statically allocate (and leak) a credentials
provider

* Use absl::make_unique

std::make_unique technically does not exist until C++14.

* #include <utility> for std::move

* Use std::future for the initial user

* fix style

2 files changed, 36 insertions, 28 deletions

diff --git a/Firestore/Source/Core/FSTFirestoreClient.h b/Firestore/Source/Core/FSTFirestoreClient.h
index 56101ab..6da5ed3 100644
--- a/Firestore/Source/Core/FSTFirestoreClient.h
+++ b/Firestore/Source/Core/FSTFirestoreClient.h
@@ -20,6 +20,7 @@
 #import "Firestore/Source/Core/FSTViewSnapshot.h"
 #import "Firestore/Source/Remote/FSTRemoteStore.h"
 
+#include "Firestore/core/src/firebase/firestore/auth/credentials_provider.h"
 #include "Firestore/core/src/firebase/firestore/core/database_info.h"
 #include "Firestore/core/src/firebase/firestore/model/database_id.h"
 
@@ -30,7 +31,6 @@
 @class FSTQuery;
 @class FSTQueryListener;
 @class FSTTransaction;
-@protocol FSTCredentialsProvider;
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -48,7 +48,8 @@ NS_ASSUME_NONNULL_BEGIN
  */
 + (instancetype)clientWithDatabaseInfo:(const firebase::firestore::core::DatabaseInfo &)databaseInfo
                         usePersistence:(BOOL)usePersistence
-                   credentialsProvider:(id<FSTCredentialsProvider>)credentialsProvider
+                   credentialsProvider:(firebase::firestore::auth::CredentialsProvider *)
+                                           credentialsProvider  // no passing ownership
                      userDispatchQueue:(FSTDispatchQueue *)userDispatchQueue
                    workerDispatchQueue:(FSTDispatchQueue *)workerDispatchQueue;
 
diff --git a/Firestore/Source/Core/FSTFirestoreClient.mm b/Firestore/Source/Core/FSTFirestoreClient.mm
index c60bb7c..fb86e0b 100644
--- a/Firestore/Source/Core/FSTFirestoreClient.mm
+++ b/Firestore/Source/Core/FSTFirestoreClient.mm
@@ -16,7 +16,8 @@
 
 #import "Firestore/Source/Core/FSTFirestoreClient.h"
 
-#import "Firestore/Source/Auth/FSTCredentialsProvider.h"
+#import <future>
+
 #import "Firestore/Source/Core/FSTEventManager.h"
 #import "Firestore/Source/Core/FSTSyncEngine.h"
 #import "Firestore/Source/Core/FSTTransaction.h"
@@ -34,11 +35,13 @@
 #import "Firestore/Source/Util/FSTDispatchQueue.h"
 #import "Firestore/Source/Util/FSTLogger.h"
 
+#include "Firestore/core/src/firebase/firestore/auth/credentials_provider.h"
 #include "Firestore/core/src/firebase/firestore/core/database_info.h"
 #include "Firestore/core/src/firebase/firestore/model/database_id.h"
 #include "Firestore/core/src/firebase/firestore/util/string_apple.h"
 
 namespace util = firebase::firestore::util;
+using firebase::firestore::auth::CredentialsProvider;
 using firebase::firestore::auth::User;
 using firebase::firestore::core::DatabaseInfo;
 using firebase::firestore::model::DatabaseId;
@@ -51,7 +54,8 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (instancetype)initWithDatabaseInfo:(const DatabaseInfo &)databaseInfo
                       usePersistence:(BOOL)usePersistence
-                 credentialsProvider:(id<FSTCredentialsProvider>)credentialsProvider
+                 credentialsProvider:
+                     (CredentialsProvider *)credentialsProvider  // no passing ownership
                    userDispatchQueue:(FSTDispatchQueue *)userDispatchQueue
                  workerDispatchQueue:(FSTDispatchQueue *)queue NS_DESIGNATED_INITIALIZER;
 
@@ -70,7 +74,8 @@ NS_ASSUME_NONNULL_BEGIN
  */
 @property(nonatomic, strong, readonly) FSTDispatchQueue *workerDispatchQueue;
 
-@property(nonatomic, strong, readonly) id<FSTCredentialsProvider> credentialsProvider;
+// Does not own the CredentialsProvider instance.
+@property(nonatomic, assign, readonly) CredentialsProvider *credentialsProvider;
 
 @end
 
@@ -78,7 +83,8 @@ NS_ASSUME_NONNULL_BEGIN
 
 + (instancetype)clientWithDatabaseInfo:(const DatabaseInfo &)databaseInfo
                         usePersistence:(BOOL)usePersistence
-                   credentialsProvider:(id<FSTCredentialsProvider>)credentialsProvider
+                   credentialsProvider:
+                       (CredentialsProvider *)credentialsProvider  // no passing ownership
                      userDispatchQueue:(FSTDispatchQueue *)userDispatchQueue
                    workerDispatchQueue:(FSTDispatchQueue *)workerDispatchQueue {
   return [[FSTFirestoreClient alloc] initWithDatabaseInfo:databaseInfo
@@ -90,7 +96,8 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (instancetype)initWithDatabaseInfo:(const DatabaseInfo &)databaseInfo
                       usePersistence:(BOOL)usePersistence
-                 credentialsProvider:(id<FSTCredentialsProvider>)credentialsProvider
+                 credentialsProvider:
+                     (CredentialsProvider *)credentialsProvider  // no passing ownership
                    userDispatchQueue:(FSTDispatchQueue *)userDispatchQueue
                  workerDispatchQueue:(FSTDispatchQueue *)workerDispatchQueue {
   if (self = [super init]) {
@@ -99,32 +106,32 @@ NS_ASSUME_NONNULL_BEGIN
     _userDispatchQueue = userDispatchQueue;
     _workerDispatchQueue = workerDispatchQueue;
 
-    dispatch_semaphore_t initialUserAvailable = dispatch_semaphore_create(0);
-    __block bool initialized = false;
-    __block User initialUser;
-    FSTWeakify(self);
-    _credentialsProvider.userChangeListener = ^(User user) {
-      FSTStrongify(self);
-      if (self) {
-        if (!initialized) {
-          initialUser = user;
-          initialized = true;
-          dispatch_semaphore_signal(initialUserAvailable);
-        } else {
-          [workerDispatchQueue dispatchAsync:^{
-            [self userDidChange:user];
-          }];
-        }
+    auto userPromise = std::make_shared<std::promise<User>>();
+
+    __weak typeof(self) weakSelf = self;
+    auto userChangeListener = [initialized = false, userPromise, weakSelf,
+                               workerDispatchQueue](User user) mutable {
+      typeof(self) strongSelf = weakSelf;
+      if (!strongSelf) return;
+
+      if (!initialized) {
+        initialized = true;
+        userPromise->set_value(user);
+      } else {
+        [workerDispatchQueue dispatchAsync:^{
+          [strongSelf userDidChange:user];
+        }];
       }
     };
 
+    _credentialsProvider->SetUserChangeListener(userChangeListener);
+
     // Defer initialization until we get the current user from the userChangeListener. This is
     // guaranteed to be synchronously dispatched onto our worker queue, so we will be initialized
     // before any subsequently queued work runs.
     [_workerDispatchQueue dispatchAsync:^{
-      dispatch_semaphore_wait(initialUserAvailable, DISPATCH_TIME_FOREVER);
-
-      [self initializeWithUser:initialUser usePersistence:usePersistence];
+      User user = userPromise->get_future().get();
+      [self initializeWithUser:user usePersistence:usePersistence];
     }];
   }
   return self;
@@ -172,7 +179,7 @@ NS_ASSUME_NONNULL_BEGIN
 
   FSTDatastore *datastore = [FSTDatastore datastoreWithDatabase:self.databaseInfo
                                             workerDispatchQueue:self.workerDispatchQueue
-                                                    credentials:self.credentialsProvider];
+                                                    credentials:_credentialsProvider];
 
   _remoteStore = [FSTRemoteStore remoteStoreWithLocalStore:_localStore datastore:datastore];
 
@@ -229,7 +236,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (void)shutdownWithCompletion:(nullable FSTVoidErrorBlock)completion {
   [self.workerDispatchQueue dispatchAsync:^{
-    self.credentialsProvider.userChangeListener = nil;
+    self->_credentialsProvider->SetUserChangeListener(nullptr);
 
     [self.remoteStore shutdown];
     [self.localStore shutdown];