Support ServerTimestamps

Author: schmidt-sebastian

Firestore/core/src/model/server_timestamp_util.cc

@@ -28,6 +28,38 @@ const char kLocalWriteTimeKey[] = "__local_write_time__";
 const char kPreviousValueKey[] = "__previous_value__";
 const char kServerTimestampSentinel[] = "server_timestamp";
 
+google_firestore_v1_Value EncodeServerTimestamp(
+    google_protobuf_Timestamp local_write_time,
+    absl::optional<google_firestore_v1_Value> previous_value) {
+  google_firestore_v1_Value result{};
+  result.which_value_type = google_firestore_v1_Value_map_value_tag;
+
+  pb_size_t count = previous_value ? 3 : 2;
+
+  auto& map_value = result.map_value;
+  map_value.fields_count = count;
+  map_value.fields =
+      nanopb::MakeArray<google_firestore_v1_MapValue_FieldsEntry>(count);
+
+  auto field = map_value.fields;
+  field->key = nanopb::MakeBytesArray(kTypeKey);
+  field->value.which_value_type = google_firestore_v1_Value_string_value_tag;
+  field->value.string_value = nanopb::MakeBytesArray(kServerTimestampSentinel);
+
+  ++field;
+  field->key = nanopb::MakeBytesArray(kLocalWriteTimeKey);
+  field->value.which_value_type = google_firestore_v1_Value_timestamp_value_tag;
+  field->value.timestamp_value = local_write_time;
+
+  if (previous_value) {
+    ++field;
+    field->key = nanopb::MakeBytesArray(kPreviousValueKey);
+    field->value = *previous_value;
+  }
+
+  return result;
+}
+
 bool IsServerTimestamp(const google_firestore_v1_Value& value) {
   if (value.which_value_type != google_firestore_v1_Value_map_value_tag) {
     return false;

Firestore/core/src/model/server_timestamp_util.h

@@ -27,6 +27,12 @@ namespace model {
 // Utility methods to handle ServerTimestamps, which are stored using special
 // sentinel fields in MapValues.
 
+/**
+ * Encodes the backing data for a server timestamp in a Value proto.
+ */
+google_firestore_v1_Value EncodeServerTimestamp(
+    google_protobuf_Timestamp local_write_time,
+    absl::optional<google_firestore_v1_Value> previous_value);
 /**
  * Returns whether the provided value is a field map that contains the
  * sentinel values of a ServerTimestamp.

Firestore/core/src/remote/serializer.cc

@@ -42,6 +42,7 @@
 #include "Firestore/core/src/model/no_document.h"
 #include "Firestore/core/src/model/patch_mutation.h"
 #include "Firestore/core/src/model/resource_path.h"
+#include "Firestore/core/src/model/server_timestamp_util.h"
 #include "Firestore/core/src/model/set_mutation.h"
 #include "Firestore/core/src/model/verify_mutation.h"
 #include "Firestore/core/src/nanopb/byte_string.h"
@@ -78,6 +79,7 @@ using model::DeleteMutation;
 using model::Document;
 using model::DocumentKey;
 using model::DocumentState;
+using model::EncodeServerTimestamp;
 using model::FieldMask;
 using model::FieldPath;
 using model::FieldTransform;
@@ -218,8 +220,7 @@ google_firestore_v1_Value Serializer::EncodeFieldValue(
     }
 
     case FieldValue::Type::ServerTimestamp:
-      HARD_FAIL("Unhandled type %s on %s", field_value.type(),
-                field_value.ToString());
+      return EncodeServerTimestampValue(field_value.server_timestamp_value());
   }
   UNREACHABLE();
 }
@@ -260,6 +261,17 @@ google_firestore_v1_Value Serializer::EncodeTimestampValue(
   return result;
 }
 
+google_firestore_v1_Value Serializer::EncodeServerTimestampValue(
+    const FieldValue::ServerTimestamp& value) const {
+  auto previous_value =
+      value.previous_value()
+          ? absl::optional<google_firestore_v1_Value>{EncodeFieldValue(
+                *value.previous_value())}
+          : absl::nullopt;
+  return EncodeServerTimestamp(EncodeTimestamp(value.local_write_time()),
+                               previous_value);
+}
+
 google_firestore_v1_Value Serializer::EncodeStringValue(
     const std::string& value) const {
   google_firestore_v1_Value result{};

Firestore/core/src/remote/serializer.h

@@ -264,6 +264,8 @@ class Serializer {
   google_firestore_v1_Value EncodeInteger(int64_t value) const;
   google_firestore_v1_Value EncodeDouble(double value) const;
   google_firestore_v1_Value EncodeTimestampValue(Timestamp value) const;
+  google_firestore_v1_Value EncodeServerTimestampValue(
+      const model::FieldValue::ServerTimestamp& value) const;
   google_firestore_v1_Value EncodeStringValue(const std::string& value) const;
   google_firestore_v1_Value EncodeBlob(const nanopb::ByteString& value) const;
   google_firestore_v1_Value EncodeReference(