Merge remote-tracking branch 'origin/master' into rsgowman/protobuf_cpp

Also "fixed" BadFieldValueTagWithOtherValidTagsPresent test by changing
'false' to 'true'. Details: Depending on the version of nanopb, nanopb
would explicitly encode 'false', which shouldn't be done in proto3. When
it's explicitly encoded, the test worked properly. But when it was
(properly) dropped, the invalid tag is the only field that's actually
encoded, thus violating the assumptions of the test, leading to a test
failure. s/false/true fixes it, as now the boolean_value field is
(properly) encoded regardless of version.

18 files changed, 650 insertions, 77 deletions

diff --git a/Firestore/core/include/firebase/firestore/CMakeLists.txt b/Firestore/core/include/firebase/firestore/CMakeLists.txt
index e4e7acd..0c7fd48 100644
--- a/Firestore/core/include/firebase/firestore/CMakeLists.txt
+++ b/Firestore/core/include/firebase/firestore/CMakeLists.txt
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# Hack to make the headers show up in IDEs
+# Workaround to make the headers show up in IDEs
 # (see https://stackoverflow.com/questions/27039019/ and open issue on CMake
 # issue tracker: https://gitlab.kitware.com/cmake/cmake/issues/15234)
 add_custom_target(firebase_firestore_types_ide SOURCES
diff --git a/Firestore/core/include/firebase/firestore/collection_reference.h b/Firestore/core/include/firebase/firestore/collection_reference.h
new file mode 100644
index 0000000..4d47248
--- /dev/null
+++ b/Firestore/core/include/firebase/firestore/collection_reference.h
@@ -0,0 +1,98 @@
+/*
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_COLLECTION_REFERENCE_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_COLLECTION_REFERENCE_H_
+
+namespace firebase {
+namespace firestore {
+
+class CollectionReferenceInternal;
+class FirestoreInternal;
+
+/**
+ * A CollectionReference refers to a collection of documents location in a
+ * Firestore database and can be used for adding documents, getting document
+ * references, and querying for documents.
+ */
+// TODO(zxu123): add more methods to complete the class and make it useful.
+class CollectionReference {
+ public:
+  /**
+   * @brief Default constructor. This creates an invalid CollectionReference.
+   * Attempting to perform any operations on this reference will fail unless a
+   * valid CollectionReference has been assigned to it.
+   */
+  CollectionReference();
+
+  /**
+   * @brief Copy constructor. It's totally okay (and efficient) to copy
+   * CollectionReference instances, as they simply point to the same location in
+   * the database.
+   *
+   * @param[in] reference CollectionReference to copy from.
+   */
+  CollectionReference(const CollectionReference& reference);
+
+  /**
+   * @brief Move constructor. Moving is an efficient operation for
+   * CollectionReference instances.
+   *
+   * @param[in] reference CollectionReference to move data from.
+   */
+  CollectionReference(CollectionReference&& reference);
+
+  /** @brief Required virtual destructor. */
+  virtual ~CollectionReference();
+
+  /**
+   * @brief Copy assignment operator. It's totally okay (and efficient) to copy
+   * CollectionReference instances, as they simply point to the same location in
+   * the database.
+   *
+   * @param[in] reference CollectionReference to copy from.
+   *
+   * @returns Reference to the destination CollectionReference.
+   */
+  CollectionReference& operator=(const CollectionReference& reference);
+
+  /**
+   * @brief Move assignment operator. Moving is an efficient operation for
+   * CollectionReference instances.
+   *
+   * @param[in] reference CollectionReference to move data from.
+   *
+   * @returns Reference to the destination CollectionReference.
+   */
+  CollectionReference& operator=(CollectionReference&& reference);
+
+ protected:
+  explicit CollectionReference(CollectionReferenceInternal* internal);
+
+ private:
+  friend class DocumentReference;
+  friend class DocumentReferenceInternal;
+  friend class FirestoreInternal;
+
+  // TODO(zxu123): investigate possibility to use std::unique_ptr or
+  // firebase::UniquePtr.
+  CollectionReferenceInternal* internal_ = nullptr;
+};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_COLLECTION_REFERENCE_H_
diff --git a/Firestore/core/include/firebase/firestore/document_change.h b/Firestore/core/include/firebase/firestore/document_change.h
new file mode 100644
index 0000000..4812290
--- /dev/null
+++ b/Firestore/core/include/firebase/firestore/document_change.h
@@ -0,0 +1,34 @@
+/*
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_DOCUMENT_CHANGE_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_DOCUMENT_CHANGE_H_
+
+namespace firebase {
+namespace firestore {
+
+/**
+ * A DocumentChange represents a change to the documents matching a query. It
+ * contains the document affected and the type of change that occurred (added,
+ * modified, or removed).
+ */
+// TODO(zxu123): add more methods to complete the class and make it useful.
+class DocumentChange {};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_DOCUMENT_CHANGE_H_
diff --git a/Firestore/core/include/firebase/firestore/document_reference.h b/Firestore/core/include/firebase/firestore/document_reference.h
index d295188..9385ed3 100644
--- a/Firestore/core/include/firebase/firestore/document_reference.h
+++ b/Firestore/core/include/firebase/firestore/document_reference.h
@@ -29,6 +29,17 @@
 #include <functional>
 #endif
 
+#include "firebase/app.h"
+#include "firebase/firestore/collection_reference.h"
+#include "firebase/firestore/document_snapshot.h"
+#include "firebase/firestore/event_listener.h"
+#include "firebase/firestore/field_value.h"
+#include "firebase/firestore/firestore.h"
+#include "firebase/firestore/firestore_errors.h"
+#include "firebase/firestore/listener_registration.h"
+#include "firebase/firestore/set_options.h"
+#include "firebase/future.h"
+
 // TODO(rsgowman): Note that RTDB uses:
 //   #if defined(FIREBASE_USE_MOVE_OPERATORS) || defined(DOXYGEN
 // to protect move operators from older compilers. But all our supported
@@ -36,34 +47,12 @@
 // here so we don't forget to mention this during the API review, and should be
 // removed once this note has migrated to the API review doc.
 
-// TODO(rsgowman): replace these forward decls with appropriate includes (once
-// they exist)
-namespace firebase {
-class App;
-template <typename T>
-class Future;
-}  // namespace firebase
-
 namespace firebase {
 namespace firestore {
 
-// TODO(rsgowman): replace these forward decls with appropriate includes (once
-// they exist)
-class FieldValue;
-class DocumentSnapshot;
+class DocumentReferenceInternal;
 class Firestore;
-class Error;
-template <typename T>
-class EventListener;
-class ListenerRegistration;
-class CollectionReference;
-class DocumentListenOptions;
-// TODO(rsgowman): not quite a forward decl, but required to make the default
-// parameter to Set() "compile".
-class SetOptions {
- public:
-  SetOptions();
-};
+class FirestoreInternal;
 
 // TODO(rsgowman): move this into the FieldValue header
 #ifdef STLPORT
@@ -80,12 +69,19 @@ using MapFieldValue = std::unordered_map<std::string, FieldValue>;
  *
  * Create a DocumentReference via Firebase::Document(const string& path).
  *
+ * NOT thread-safe: an instance should not be used from multiple threads
+ *
  * Subclassing Note: Firestore classes are not meant to be subclassed except for
  * use in test mocks. Subclassing is not supported in production code and new
  * SDK releases may break code that does so.
  */
 class DocumentReference {
  public:
+  enum class MetadataChanges {
+    kExclude,
+    kInclude,
+  };
+
   /**
    * @brief Default constructor. This creates an invalid DocumentReference.
    * Attempting to perform any operations on this reference will fail (and cause
@@ -269,28 +265,15 @@ class DocumentReference {
    * this DocumentReference. (Ownership is not transferred; you are responsible
    * for making sure that listener is valid as long as this DocumentReference is
    * valid and the listener is registered.)
+   * @param[in] metadata_changes Indicates whether metadata-only changes (i.e.
+   * only DocumentSnapshot.getMetadata() changed) should trigger snapshot
+   * events.
    *
    * @return A registration object that can be used to remove the listener.
    */
   virtual ListenerRegistration AddSnapshotListener(
-      EventListener<DocumentSnapshot>* listener);
-
-  /**
-   * @brief Starts listening to the document referenced by this
-   * DocumentReference.
-   *
-   * @param[in] options The options to use for this listen.
-   * @param[in] listener The event listener that will be called with the
-   * snapshots, which must remain in memory until you remove the listener from
-   * this DocumentReference. (Ownership is not transferred; you are responsible
-   * for making sure that listener is valid as long as this DocumentReference is
-   * valid and the listener is registered.)
-   *
-   * @return A registration object that can be used to remove the listener.
-   */
-  virtual ListenerRegistration AddSnapshotListener(
-      const DocumentListenOptions& options,
-      EventListener<DocumentSnapshot>* listener);
+      EventListener<DocumentSnapshot>* listener,
+      MetadataChanges metadata_changes = MetadataChanges::kExclude);
 
 #if defined(FIREBASE_USE_STD_FUNCTION) || defined(DOXYGEN)
   /**
@@ -299,6 +282,9 @@ class DocumentReference {
    *
    * @param[in] callback function or lambda to call. When this function is
    * called, exactly one of the parameters will be non-null.
+   * @param[in] metadata_changes Indicates whether metadata-only changes (i.e.
+   * only DocumentSnapshot.getMetadata() changed) should trigger snapshot
+   * events.
    *
    * @return A registration object that can be used to remove the listener.
    *
@@ -306,28 +292,21 @@ class DocumentReference {
    * std::function is not supported on STLPort.
    */
   virtual ListenerRegistration AddSnapshotListener(
-      std::function<void(const DocumentSnapshot*, const Error*)> callback);
-
-  /**
-   * @brief Starts listening to the document referenced by this
-   * DocumentReference.
-   *
-   * @param[in] options The options to use for this listen.
-   * @param[in] callback function or lambda to call. When this function is
-   * called, exactly one of the parameters will be non-null.
-   *
-   * @return A registration object that can be used to remove the listener.
-   *
-   * @note This method is not available when using STLPort on Android, as
-   * std::function is not supported on STLPort.
-   */
-  virtual ListenerRegistration AddSnapshotListener(
-      const DocumentListenOptions& options,
-      std::function<void(const DocumentSnapshot*, const Error*)> callback);
+      std::function<void(const DocumentSnapshot*, const Error*)> callback,
+      MetadataChanges metadata_changes = MetadataChanges::kExclude);
 #endif  // defined(FIREBASE_USE_STD_FUNCTION) || defined(DOXYGEN)
+
+ protected:
+  explicit DocumentReference(DocumentReferenceInternal* internal);
+
+ private:
+  friend class FirestoreInternal;
+
+  // TODO(zxu123): investigate possibility to use std::unique_ptr or
+  // firebase::UniquePtr.
+  DocumentReferenceInternal* internal_ = nullptr;
 };
 
-// TODO(rsgowman): probably define and inline here.
 bool operator==(const DocumentReference& lhs, const DocumentReference& rhs);
 
 inline bool operator!=(const DocumentReference& lhs,
diff --git a/Firestore/core/include/firebase/firestore/document_snapshot.h b/Firestore/core/include/firebase/firestore/document_snapshot.h
new file mode 100644
index 0000000..3be72b5
--- /dev/null
+++ b/Firestore/core/include/firebase/firestore/document_snapshot.h
@@ -0,0 +1,38 @@
+/*
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_DOCUMENT_SNAPSHOT_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_DOCUMENT_SNAPSHOT_H_
+
+namespace firebase {
+namespace firestore {
+
+/**
+ * A DocumentSnapshot contains data read from a document in your Firestore
+ * database. The data can be extracted with the data() method or by using
+ * FooValue() to access a specific field, where Foo is the type of that field.
+ *
+ * For a DocumentSnapshot that points to a non-existing document, any data
+ * access will cause a failed assertion. You can use the exists() method to
+ * explicitly verify a documents existence.
+ */
+// TODO(zxu123): add more methods to complete the class and make it useful.
+class DocumentSnapshot {};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_DOCUMENT_SNAPSHOT_H_
diff --git a/Firestore/core/include/firebase/firestore/event_listener.h b/Firestore/core/include/firebase/firestore/event_listener.h
index 6c94428..cbe8a28 100644
--- a/Firestore/core/include/firebase/firestore/event_listener.h
+++ b/Firestore/core/include/firebase/firestore/event_listener.h
@@ -22,19 +22,19 @@
 #ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_EVENT_LISTENER_H_
 #define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_EVENT_LISTENER_H_
 
+#include "firebase/firestore/firestore_errors.h"
+
 namespace firebase {
 namespace firestore {
 
-// TODO(rsgowman): replace these forward decl's with appropriate includes (once
-// they exist)
-class Error;
-
 /**
  * @brief An interface for event listeners.
  */
 template <typename T>
 class EventListener {
  public:
+  virtual ~EventListener() {
+  }
   /**
    * @brief OnEvent will be called with the new value or the error if an error
    * occurred.
@@ -44,7 +44,7 @@ class EventListener {
    * @param value The value of the event. null if there was an error.
    * @param error The error if there was error. null otherwise.
    */
-  void OnEvent(const T* value, const Error* error);
+  virtual void OnEvent(const T* value, const Error* error) = 0;
 };
 
 }  // namespace firestore
diff --git a/Firestore/core/include/firebase/firestore/field_path.h b/Firestore/core/include/firebase/firestore/field_path.h
new file mode 100644
index 0000000..29e1dea
--- /dev/null
+++ b/Firestore/core/include/firebase/firestore/field_path.h
@@ -0,0 +1,34 @@
+/*
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_FIELD_PATH_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_FIELD_PATH_H_
+
+namespace firebase {
+namespace firestore {
+
+/**
+ * A FieldPath refers to a field in a document. The path may consist of a single
+ * field name (referring to a top level field in the document), or a list of
+ * field names (referring to a nested field in the document).
+ */
+// TODO(zxu123): add more methods to complete the class and make it useful.
+class FieldPath {};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_FIELD_PATH_H_
diff --git a/Firestore/core/include/firebase/firestore/field_value.h b/Firestore/core/include/firebase/firestore/field_value.h
new file mode 100644
index 0000000..d919de4
--- /dev/null
+++ b/Firestore/core/include/firebase/firestore/field_value.h
@@ -0,0 +1,33 @@
+/*
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_FIELD_VALUE_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_FIELD_VALUE_H_
+
+namespace firebase {
+namespace firestore {
+
+/**
+ * Sentinel values that can be used when writing document fields with setData()
+ * or updateData().
+ */
+// TODO(zxu123): add more methods to complete the class and make it useful.
+class FieldValue {};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_FIELD_VALUE_H_
diff --git a/Firestore/core/include/firebase/firestore/firestore.h b/Firestore/core/include/firebase/firestore/firestore.h
index 793fdd0..6591a72 100644
--- a/Firestore/core/include/firebase/firestore/firestore.h
+++ b/Firestore/core/include/firebase/firestore/firestore.h
@@ -22,23 +22,19 @@
 #ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_FIRESTORE_H_
 #define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_FIRESTORE_H_
 
+#include <memory>
 #include <string>
 
-// TODO(rsgowman): replace these forward decl's with appropriate includes (once
-// they exist)
-namespace firebase {
-class App;
-class InitResult;
-}  // namespace firebase
+#include "firebase/app.h"
+#include "firebase/firestore/collection_reference.h"
+#include "firebase/firestore/document_reference.h"
+#include "firebase/firestore/settings.h"
 
 namespace firebase {
 namespace firestore {
 
-// TODO(rsgowman): replace these forward decl's with appropriate includes (once
-// they exist)
 class DocumentReference;
-class CollectionReference;
-class Settings;
+class FirestoreInternal;
 
 /**
  * @brief Entry point for the Firebase Firestore C++ SDK.
@@ -152,6 +148,16 @@ class Firestore {
 
   /** Globally enables / disables Firestore logging for the SDK. */
   static void set_logging_enabled(bool logging_enabled);
+
+  Firestore(const Firestore& src) = delete;
+  Firestore& operator=(const Firestore& src) = delete;
+
+ private:
+  explicit Firestore(::firebase::App* app);
+
+  // TODO(zxu123): investigate possibility to use std::unique_ptr or
+  // firebase::UniquePtr.
+  FirestoreInternal* internal_ = nullptr;
 };
 
 }  // namespace firestore
diff --git a/Firestore/core/include/firebase/firestore/firestore_errors.h b/Firestore/core/include/firebase/firestore/firestore_errors.h
index 7a0ff7c..92c0c92 100644
--- a/Firestore/core/include/firebase/firestore/firestore_errors.h
+++ b/Firestore/core/include/firebase/firestore/firestore_errors.h
@@ -109,6 +109,10 @@ enum FirestoreErrorCode {
   Unauthenticated = 16
 };
 
+// TODO(zxu123): decide whether we actually want an Error class or just use
+// enum.
+using Error = FirestoreErrorCode;
+
 }  // namespace firestore
 }  // namespace firebase
 
diff --git a/Firestore/core/include/firebase/firestore/listener_registration.h b/Firestore/core/include/firebase/firestore/listener_registration.h
new file mode 100644
index 0000000..a37c2aa
--- /dev/null
+++ b/Firestore/core/include/firebase/firestore/listener_registration.h
@@ -0,0 +1,92 @@
+/*
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_LISTENER_REGISTRATION_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_LISTENER_REGISTRATION_H_
+
+namespace firebase {
+namespace firestore {
+
+class FirestoreInternal;
+class ListenerRegistrationInternal;
+
+/** Represents a listener that can be removed by calling remove. */
+class ListenerRegistration {
+ public:
+  /**
+   * @brief Default constructor. This creates a no-op instance.
+   */
+  ListenerRegistration();
+
+  /**
+   * @brief Copy constructor. It's totally okay to copy ListenerRegistration
+   * instances.
+   *
+   * @param[in] registration ListenerRegistration to copy from.
+   */
+  ListenerRegistration(const ListenerRegistration& registration);
+
+  /**
+   * @brief Move constructor. Moving is an efficient operation for
+   * ListenerRegistration instances.
+   *
+   * @param[in] registration ListenerRegistration to move data from.
+   */
+  ListenerRegistration(ListenerRegistration&& registration);
+
+  ~ListenerRegistration();
+
+  /**
+   * @brief Copy assignment operator. It's totally okay to copy
+   * ListenerRegistration instances.
+   *
+   * @param[in] registration ListenerRegistration to copy from.
+   *
+   * @returns Reference to the destination ListenerRegistration.
+   */
+  ListenerRegistration& operator=(const ListenerRegistration& registration);
+
+  /**
+   * @brief Move assignment operator. Moving is an efficient operation for
+   * ListenerRegistration instances.
+   *
+   * @param[in] registration ListenerRegistration to move data from.
+   *
+   * @returns Reference to the destination ListenerRegistration.
+   */
+  ListenerRegistration& operator=(ListenerRegistration&& registration);
+
+  /**
+   * Removes the listener being tracked by this ListenerRegistration. After the
+   * initial call, subsequent calls have no effect.
+   */
+  void Remove();
+
+ private:
+  friend class DocumentReferenceInternal;
+  friend class ListenerRegistrationInternal;
+  friend class FirestoreInternal;
+
+  explicit ListenerRegistration(ListenerRegistrationInternal* internal);
+
+  FirestoreInternal* firestore_ = nullptr;
+  ListenerRegistrationInternal* internal_ = nullptr;
+};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_LISTENER_REGISTRATION_H_
diff --git a/Firestore/core/include/firebase/firestore/query.h b/Firestore/core/include/firebase/firestore/query.h
new file mode 100644
index 0000000..da6dfdd
--- /dev/null
+++ b/Firestore/core/include/firebase/firestore/query.h
@@ -0,0 +1,33 @@
+/*
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_QUERY_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_QUERY_H_
+
+namespace firebase {
+namespace firestore {
+
+/**
+ * A Query which you can read or listen to. You can also construct refined
+ * Query objects by adding filters and ordering.
+ */
+// TODO(zxu123): add more methods to complete the class and make it useful.
+class Query {};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_QUERY_H_
diff --git a/Firestore/core/include/firebase/firestore/query_snapshot.h b/Firestore/core/include/firebase/firestore/query_snapshot.h
new file mode 100644
index 0000000..ffa2bd6
--- /dev/null
+++ b/Firestore/core/include/firebase/firestore/query_snapshot.h
@@ -0,0 +1,34 @@
+/*
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_QUERY_SNAPSHOT_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_QUERY_SNAPSHOT_H_
+
+namespace firebase {
+namespace firestore {
+
+/**
+ * A QuerySnapshot contains zero or more DocumentSnapshot objects. It can be
+ * iterated using a range-based for loop and its size can be inspected with
+ * empty() and count().
+ */
+// TODO(zxu123): add more methods to complete the class and make it useful.
+class QuerySnapshot {};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_QUERY_SNAPSHOT_H_
diff --git a/Firestore/core/include/firebase/firestore/set_options.h b/Firestore/core/include/firebase/firestore/set_options.h
new file mode 100644
index 0000000..802f3b5
--- /dev/null
+++ b/Firestore/core/include/firebase/firestore/set_options.h
@@ -0,0 +1,39 @@
+/*
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_SET_OPTIONS_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_SET_OPTIONS_H_
+
+namespace firebase {
+namespace firestore {
+
+/**
+ * An options object that configures the behavior of Set() calls. By providing
+ * the SetOptions objects returned by Merge(), the Set() methods in
+ * DocumentReference, WriteBatch and Transaction can be configured to perform
+ * granular merges instead of overwriting the target documents in their
+ * entirety.
+ */
+// TODO(zxu123): add more methods to complete the class and make it useful.
+class SetOptions {
+ public:
+  SetOptions();
+};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_SET_OPTIONS_H_
diff --git a/Firestore/core/include/firebase/firestore/settings.h b/Firestore/core/include/firebase/firestore/settings.h
new file mode 100644
index 0000000..9356b26
--- /dev/null
+++ b/Firestore/core/include/firebase/firestore/settings.h
@@ -0,0 +1,32 @@
+/*
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_SETTINGS_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_SETTINGS_H_
+
+namespace firebase {
+namespace firestore {
+
+class SettingsInternal;
+
+/** Settings used to configure a Firestore instance. */
+// TODO(zxu123): add more methods to complete the class and make it useful.
+class Settings {};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_SETTINGS_H_
diff --git a/Firestore/core/include/firebase/firestore/snapshot_metadata.h b/Firestore/core/include/firebase/firestore/snapshot_metadata.h
new file mode 100644
index 0000000..9bcc54c
--- /dev/null
+++ b/Firestore/core/include/firebase/firestore/snapshot_metadata.h
@@ -0,0 +1,46 @@
+/*
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_SNAPSHOT_METADATA_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_SNAPSHOT_METADATA_H_
+
+namespace firebase {
+namespace firestore {
+
+/** Metadata about a snapshot, describing the state of the snapshot. */
+class SnapshotMetadata {
+ public:
+  SnapshotMetadata(bool has_pending_writes, bool is_from_cache)
+      : has_pending_writes_(has_pending_writes), is_from_cache_(is_from_cache) {
+  }
+
+  bool has_pending_writes() const {
+    return has_pending_writes_;
+  }
+
+  bool is_from_cache() const {
+    return is_from_cache_;
+  }
+
+ private:
+  const bool has_pending_writes_;
+  const bool is_from_cache_;
+};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_SNAPSHOT_METADATA_H_
diff --git a/Firestore/core/include/firebase/firestore/transaction.h b/Firestore/core/include/firebase/firestore/transaction.h
new file mode 100644
index 0000000..be043b8
--- /dev/null
+++ b/Firestore/core/include/firebase/firestore/transaction.h
@@ -0,0 +1,32 @@
+/*
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_TRANSACTION_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_TRANSACTION_H_
+
+namespace firebase {
+namespace firestore {
+
+/**
+ * Transaction provides methods to read and write data within a transaction.
+ */
+// TODO(zxu123): add more methods to complete the class and make it useful.
+class Transaction {};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_TRANSACTION_H_
diff --git a/Firestore/core/include/firebase/firestore/write_batch.h b/Firestore/core/include/firebase/firestore/write_batch.h
new file mode 100644
index 0000000..bd2c12f
--- /dev/null
+++ b/Firestore/core/include/firebase/firestore/write_batch.h
@@ -0,0 +1,39 @@
+/*
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_WRITE_BATCH_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_WRITE_BATCH_H_
+
+namespace firebase {
+namespace firestore {
+
+/**
+ * A write batch is used to perform multiple writes as a single atomic unit.
+ *
+ * A WriteBatch object provides methods for adding writes to the write batch.
+ * None of the writes will be committed (or visible locally) until commit() is
+ * called.
+ *
+ * Unlike transactions, write batches are persisted offline and therefore are
+ * preferable when you don't need to condition your writes on read data.
+ */
+// TODO(zxu123): add more methods to complete the class and make it useful.
+class WriteBatch {};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_WRITE_BATCH_H_