1 files changed, 67 insertions, 0 deletions
diff --git a/Firestore/core/src/firebase/firestore/model/precondition.cc b/Firestore/core/src/firebase/firestore/model/precondition.cc
new file mode 100644
index 0000000..423d5a2
--- /dev/null
+++ b/Firestore/core/src/firebase/firestore/model/precondition.cc
@@ -0,0 +1,67 @@
+/*
+ * 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/precondition.h"
+
+#include "Firestore/core/src/firebase/firestore/model/maybe_document.h"
+#include "Firestore/core/src/firebase/firestore/model/snapshot_version.h"
+#include "Firestore/core/src/firebase/firestore/util/firebase_assert.h"
+
+namespace firebase {
+namespace firestore {
+namespace model {
+
+Precondition::Precondition(Type type, SnapshotVersion update_time, bool exists)
+    : type_(type), update_time_(std::move(update_time)), exists_(exists) {
+}
+
+/* static */
+Precondition Precondition::Exists(bool exists) {
+  return Precondition{Type::Exists, SnapshotVersion::None(), exists};
+}
+
+/* static */
+Precondition Precondition::UpdateTime(SnapshotVersion update_time) {
+  // update_time could be SnapshotVersion::None() in particular for locally
+  // deleted documents.
+  return Precondition{Type::UpdateTime, std::move(update_time), false};
+}
+
+/* static */
+Precondition Precondition::None() {
+  return Precondition{Type::None, SnapshotVersion::None(), false};
+}
+
+bool Precondition::IsValidFor(const MaybeDocument& maybe_doc) const {
+  switch (type_) {
+    case Type::UpdateTime:
+      return maybe_doc.type() == MaybeDocument::Type::Document &&
+             maybe_doc.version() == update_time_;
+    case Type::Exists:
+      if (exists_) {
+        return maybe_doc.type() == MaybeDocument::Type::Document;
+      } else {
+        return maybe_doc.type() == MaybeDocument::Type::NoDocument;
+      }
+    case Type::None:
+      return true;
+  }
+  FIREBASE_UNREACHABLE();
+}
+
+}  // namespace model
+}  // namespace firestore
+}  // namespace firebase