port Firestore SnapshotVersion in C++ (#767)

* implement SnapshotVersion and test

3 files changed, 110 insertions, 0 deletions

diff --git a/Firestore/core/src/firebase/firestore/model/CMakeLists.txt b/Firestore/core/src/firebase/firestore/model/CMakeLists.txt
index df602f9..169e310 100644
--- a/Firestore/core/src/firebase/firestore/model/CMakeLists.txt
+++ b/Firestore/core/src/firebase/firestore/model/CMakeLists.txt
@@ -22,6 +22,8 @@ cc_library(
     field_path.h
     field_value.cc
     field_value.h
+    snapshot_version.cc
+    snapshot_version.h
     resource_path.cc
     resource_path.h
     timestamp.cc
diff --git a/Firestore/core/src/firebase/firestore/model/snapshot_version.cc b/Firestore/core/src/firebase/firestore/model/snapshot_version.cc
new file mode 100644
index 0000000..114e313
--- /dev/null
+++ b/Firestore/core/src/firebase/firestore/model/snapshot_version.cc
@@ -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.
+ */
+
+#include "Firestore/core/src/firebase/firestore/model/snapshot_version.h"
+
+namespace firebase {
+namespace firestore {
+namespace model {
+
+SnapshotVersion::SnapshotVersion(const Timestamp& timestamp)
+    : timestamp_(timestamp) {
+}
+
+const SnapshotVersion& SnapshotVersion::None() {
+  static const SnapshotVersion kNone(Timestamp{});
+  return kNone;
+}
+
+}  // namespace model
+}  // namespace firestore
+}  // namespace firebase
diff --git a/Firestore/core/src/firebase/firestore/model/snapshot_version.h b/Firestore/core/src/firebase/firestore/model/snapshot_version.h
new file mode 100644
index 0000000..70f6f4a
--- /dev/null
+++ b/Firestore/core/src/firebase/firestore/model/snapshot_version.h
@@ -0,0 +1,74 @@
+/*
+ * 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_SNAPSHOT_VERSION_H_
+#define FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_MODEL_SNAPSHOT_VERSION_H_
+
+#include "Firestore/core/src/firebase/firestore/model/timestamp.h"
+
+namespace firebase {
+namespace firestore {
+namespace model {
+
+/**
+ * A version of a document in Firestore. This corresponds to the version
+ * timestamp, such as update_time or read_time.
+ */
+class SnapshotVersion {
+ public:
+  explicit SnapshotVersion(const Timestamp& timestamp);
+
+  const Timestamp& timestamp() const {
+    return timestamp_;
+  }
+
+  /** Creates a new version that is smaller than all other versions. */
+  static const SnapshotVersion& None();
+
+ private:
+  Timestamp timestamp_;
+};
+
+/** Compares against another SnapshotVersion. */
+inline bool operator<(const SnapshotVersion& lhs, const SnapshotVersion& rhs) {
+  return lhs.timestamp() < rhs.timestamp();
+}
+
+inline bool operator>(const SnapshotVersion& lhs, const SnapshotVersion& rhs) {
+  return lhs.timestamp() > rhs.timestamp();
+}
+
+inline bool operator>=(const SnapshotVersion& lhs, const SnapshotVersion& rhs) {
+  return lhs.timestamp() >= rhs.timestamp();
+}
+
+inline bool operator<=(const SnapshotVersion& lhs, const SnapshotVersion& rhs) {
+  return lhs.timestamp() <= rhs.timestamp();
+}
+
+inline bool operator!=(const SnapshotVersion& lhs, const SnapshotVersion& rhs) {
+  return lhs.timestamp() != rhs.timestamp();
+}
+
+inline bool operator==(const SnapshotVersion& lhs, const SnapshotVersion& rhs) {
+  return lhs.timestamp() == rhs.timestamp();
+}
+
+}  // namespace model
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_MODEL_SNAPSHOT_VERSION_H_