port Firestore Auth module in C++ (#733)

* Implement firestore/auth/user

* add user to project and some fixes

* implement firestore/auth/{credentials_provider,empty_credentials_provider}

* implement firestore/auth/firebase_credentials_provider

* refactoring firebase_credentials_provider and add (disabled but working) unit test

* add auth test to project

* address changes

* small fix to style and project

* fix the firebase_credentials_provider_test

* fix style

* address changes

* revert the change to static mutex_

* remove my custom plist path

* fix style

* address changes

* refactoring FirebaseCredentialsProvider to fix the issue w.r.t. auth global dispatch queue

* add /*force_refresh=*/ tag to bool literal for style purpose

* Use a shared_ptr/weak_ptr handoff on FirebaseCredentialsProvider (#778)

* Revert "refactoring FirebaseCredentialsProvider to fix the issue w.r.t. auth global dispatch queue"

This reverts commit 87175a4146267d403a774f138b85f8d3b532fa4b.

* Use a shared_ptr/weak_ptr handoff on FirebaseCredentialsProvider

This avoids any problems with callsbacks retaining pointers to objects
destroyed by a C++ destructor

1 files changed, 112 insertions, 0 deletions

diff --git a/Firestore/core/src/firebase/firestore/auth/firebase_credentials_provider_apple.h b/Firestore/core/src/firebase/firestore/auth/firebase_credentials_provider_apple.h
new file mode 100644
index 0000000..65c4c65
--- /dev/null
+++ b/Firestore/core/src/firebase/firestore/auth/firebase_credentials_provider_apple.h
@@ -0,0 +1,112 @@
+/*
+ * Copyright 2018 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Right now, FirebaseCredentialsProvider only support APPLE build.
+#if !defined(__OBJC__)
+#error "This header only supports Objective-C++."
+#endif  // !defined(__OBJC__)
+
+#ifndef FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_AUTH_FIREBASE_CREDENTIALS_PROVIDER_APPLE_H_
+#define FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_AUTH_FIREBASE_CREDENTIALS_PROVIDER_APPLE_H_
+
+#import <Foundation/Foundation.h>
+
+#include <memory>
+#include <mutex>  // NOLINT(build/c++11)
+
+#include "Firestore/core/src/firebase/firestore/auth/credentials_provider.h"
+#include "Firestore/core/src/firebase/firestore/auth/user.h"
+#include "absl/strings/string_view.h"
+
+@class FIRApp;
+
+namespace firebase {
+namespace firestore {
+namespace auth {
+
+/**
+ * `FirebaseCredentialsProvider` uses Firebase Auth via `FIRApp` to get an auth
+ * token.
+ *
+ * NOTE: To simplify the implementation, it requires that you set
+ * `userChangeListener` with a non-`nil` value no more than once and don't call
+ * `getTokenForcingRefresh:` after setting it to `nil`.
+ *
+ * This class must be implemented in a thread-safe manner since it is accessed
+ * from the thread backing our internal worker queue and the callbacks from
+ * FIRAuth will be executed on an arbitrary different thread.
+ *
+ * For non-Apple desktop build, this is right now just a stub.
+ */
+class FirebaseCredentialsProvider : public CredentialsProvider {
+ public:
+  // TODO(zxu123): Provide a ctor to accept the C++ Firebase Games App, which
+  // deals all platforms. Right now, only works for FIRApp*.
+  /**
+   * Initializes a new FirebaseCredentialsProvider.
+   *
+   * @param app The Firebase app from which to get credentials.
+   */
+  explicit FirebaseCredentialsProvider(FIRApp* app);
+
+  ~FirebaseCredentialsProvider() override;
+
+  void GetToken(bool force_refresh, TokenListener completion) override;
+
+  void SetUserChangeListener(UserChangeListener listener) override;
+
+ private:
+  /**
+   * Most contents of the FirebaseCredentialProvider are kept in this
+   * Contents object and pointed to with a shared pointer. Callbacks
+   * registered with FirebaseAuth use weak pointers to the Contents to
+   * avoid races between notifications arriving and C++ object destruction.
+   */
+  struct Contents {
+    Contents(FIRApp* app, const absl::string_view uid)
+        : app(app), current_user(uid), mutex() {
+    }
+
+    const FIRApp* app;
+
+    /**
+     * The current user as reported to us via our AuthStateDidChangeListener.
+     */
+    User current_user;
+
+    /**
+     * Counter used to detect if the user changed while a
+     * -getTokenForcingRefresh: request was outstanding.
+     */
+    int user_counter = 0;
+
+    std::mutex mutex;
+  };
+
+  /**
+   * Handle used to stop receiving auth changes once userChangeListener is
+   * removed.
+   */
+  id<NSObject> auth_listener_handle_;
+
+  std::shared_ptr<Contents> contents_;
+};
+
+}  // namespace auth
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_AUTH_FIREBASE_CREDENTIALS_PROVIDER_APPLE_H_