Port Firestore Document to C++ (#777)

* implement SnapshotVersion and test

* update project

* implement MaybeDocument and test

* move snapshot-version from core to model

* fix a bug

* implement Document and test

* implement NoDocument

* adding type tag and fix style

* fix a few bugs, discovered after merging and test run.

* add assert to check FieldValue type and more test for comparision.

* address changes

* allow moving FieldValue to construct Document.

* address changes

* add document tests to project

* use std::less convention

* make Type::Unknown static initializer

1 files changed, 36 insertions, 0 deletions

diff --git a/Firestore/core/src/firebase/firestore/model/no_document.h b/Firestore/core/src/firebase/firestore/model/no_document.h
new file mode 100644
index 0000000..7cfd47c
--- /dev/null
+++ b/Firestore/core/src/firebase/firestore/model/no_document.h
@@ -0,0 +1,36 @@
+/*
+ * 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_SRC_FIREBASE_FIRESTORE_MODEL_NO_DOCUMENT_H_
+#define FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_MODEL_NO_DOCUMENT_H_
+
+#include "Firestore/core/src/firebase/firestore/model/maybe_document.h"
+
+namespace firebase {
+namespace firestore {
+namespace model {
+
+/** Represents that no documents exists for the key at the given version. */
+class NoDocument : public MaybeDocument {
+ public:
+  NoDocument(DocumentKey key, SnapshotVersion version);
+};
+
+}  // namespace model
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_MODEL_NO_DOCUMENT_H_