Port FieldTransform to C++ (#1033)

* port FieldMask to C++

* address changes

* address changes

* fix test

* address change

* Port transform operations (FSTTransformOperation, FSTServerTimestampTransform) to C++

* address changes

* address changes

* address changes

* implement `FieldTransform` in C++

* port `FieldTransform`

* make `fieldTransforms` shared inside `context`

* address changes

* fix lint

* address changes

2 files changed, 67 insertions, 34 deletions

diff --git a/Firestore/Source/API/FSTUserDataConverter.h b/Firestore/Source/API/FSTUserDataConverter.h
index 2b4b340..a2f947a 100644
--- a/Firestore/Source/API/FSTUserDataConverter.h
+++ b/Firestore/Source/API/FSTUserDataConverter.h
@@ -16,14 +16,16 @@
 
 #import <Foundation/Foundation.h>
 
+#include <vector>
+
 #include "Firestore/core/src/firebase/firestore/model/database_id.h"
 #include "Firestore/core/src/firebase/firestore/model/document_key.h"
 #include "Firestore/core/src/firebase/firestore/model/field_mask.h"
+#include "Firestore/core/src/firebase/firestore/model/field_transform.h"
 
 @class FIRSetOptions;
 @class FSTObjectValue;
 @class FSTFieldValue;
-@class FSTFieldTransform;
 @class FSTMutation;
 @class FSTPrecondition;
 @class FSTSnapshotVersion;
@@ -36,16 +38,19 @@ NS_ASSUME_NONNULL_BEGIN
 - (instancetype)init NS_UNAVAILABLE;
 
 - (instancetype)initWithData:(FSTObjectValue *)data
-             fieldTransforms:(NSArray<FSTFieldTransform *> *)fieldTransforms
+             fieldTransforms:
+                 (std::vector<firebase::firestore::model::FieldTransform>)fieldTransforms
     NS_DESIGNATED_INITIALIZER;
 
 - (instancetype)initWithData:(FSTObjectValue *)data
                    fieldMask:(firebase::firestore::model::FieldMask)fieldMask
-             fieldTransforms:(NSArray<FSTFieldTransform *> *)fieldTransforms
+             fieldTransforms:
+                 (std::vector<firebase::firestore::model::FieldTransform>)fieldTransforms
     NS_DESIGNATED_INITIALIZER;
 
+- (const std::vector<firebase::firestore::model::FieldTransform> &)fieldTransforms;
+
 @property(nonatomic, strong, readonly) FSTObjectValue *data;
-@property(nonatomic, strong, readonly) NSArray<FSTFieldTransform *> *fieldTransforms;
 @property(nonatomic, assign, readonly) BOOL isPatch;
 
 /**
@@ -64,13 +69,14 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (instancetype)initWithData:(FSTObjectValue *)data
                    fieldMask:(firebase::firestore::model::FieldMask)fieldMask
-             fieldTransforms:(NSArray<FSTFieldTransform *> *)fieldTransforms
+             fieldTransforms:
+                 (std::vector<firebase::firestore::model::FieldTransform>)fieldTransforms
     NS_DESIGNATED_INITIALIZER;
 
 - (const firebase::firestore::model::FieldMask &)fieldMask;
+- (const std::vector<firebase::firestore::model::FieldTransform> &)fieldTransforms;
 
 @property(nonatomic, strong, readonly) FSTObjectValue *data;
-@property(nonatomic, strong, readonly) NSArray<FSTFieldTransform *> *fieldTransforms;
 
 /**
  * Converts the parsed update data into 1 or 2 mutations (depending on whether there are any
diff --git a/Firestore/Source/API/FSTUserDataConverter.mm b/Firestore/Source/API/FSTUserDataConverter.mm
index c6a6e34..2eee878 100644
--- a/Firestore/Source/API/FSTUserDataConverter.mm
+++ b/Firestore/Source/API/FSTUserDataConverter.mm
@@ -37,6 +37,7 @@
 #include "Firestore/core/src/firebase/firestore/model/document_key.h"
 #include "Firestore/core/src/firebase/firestore/model/field_mask.h"
 #include "Firestore/core/src/firebase/firestore/model/field_path.h"
+#include "Firestore/core/src/firebase/firestore/model/field_transform.h"
 #include "Firestore/core/src/firebase/firestore/model/transform_operations.h"
 #include "Firestore/core/src/firebase/firestore/util/string_apple.h"
 #include "absl/memory/memory.h"
@@ -46,7 +47,9 @@ using firebase::firestore::model::DatabaseId;
 using firebase::firestore::model::DocumentKey;
 using firebase::firestore::model::FieldMask;
 using firebase::firestore::model::FieldPath;
+using firebase::firestore::model::FieldTransform;
 using firebase::firestore::model::ServerTimestampTransform;
+using firebase::firestore::model::TransformOperation;
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -56,14 +59,15 @@ static NSString *const RESERVED_FIELD_DESIGNATOR = @"__";
 
 @implementation FSTParsedSetData {
   FieldMask _fieldMask;
+  std::vector<FieldTransform> _fieldTransforms;
 }
 
 - (instancetype)initWithData:(FSTObjectValue *)data
-             fieldTransforms:(NSArray<FSTFieldTransform *> *)fieldTransforms {
+             fieldTransforms:(std::vector<FieldTransform>)fieldTransforms {
   self = [super init];
   if (self) {
     _data = data;
-    _fieldTransforms = fieldTransforms;
+    _fieldTransforms = std::move(fieldTransforms);
     _isPatch = NO;
   }
   return self;
@@ -71,17 +75,21 @@ static NSString *const RESERVED_FIELD_DESIGNATOR = @"__";
 
 - (instancetype)initWithData:(FSTObjectValue *)data
                    fieldMask:(FieldMask)fieldMask
-             fieldTransforms:(NSArray<FSTFieldTransform *> *)fieldTransforms {
+             fieldTransforms:(std::vector<FieldTransform>)fieldTransforms {
   self = [super init];
   if (self) {
     _data = data;
     _fieldMask = std::move(fieldMask);
-    _fieldTransforms = fieldTransforms;
+    _fieldTransforms = std::move(fieldTransforms);
     _isPatch = YES;
   }
   return self;
 }
 
+- (const std::vector<FieldTransform> &)fieldTransforms {
+  return _fieldTransforms;
+}
+
 - (NSArray<FSTMutation *> *)mutationsWithKey:(const DocumentKey &)key
                                 precondition:(FSTPrecondition *)precondition {
   NSMutableArray<FSTMutation *> *mutations = [NSMutableArray array];
@@ -95,7 +103,7 @@ static NSString *const RESERVED_FIELD_DESIGNATOR = @"__";
                                                        value:self.data
                                                 precondition:precondition]];
   }
-  if (self.fieldTransforms.count > 0) {
+  if (!self.fieldTransforms.empty()) {
     [mutations addObject:[[FSTTransformMutation alloc] initWithKey:key
                                                    fieldTransforms:self.fieldTransforms]];
   }
@@ -108,16 +116,17 @@ static NSString *const RESERVED_FIELD_DESIGNATOR = @"__";
 
 @implementation FSTParsedUpdateData {
   FieldMask _fieldMask;
+  std::vector<FieldTransform> _fieldTransforms;
 }
 
 - (instancetype)initWithData:(FSTObjectValue *)data
                    fieldMask:(FieldMask)fieldMask
-             fieldTransforms:(NSArray<FSTFieldTransform *> *)fieldTransforms {
+             fieldTransforms:(std::vector<FieldTransform>)fieldTransforms {
   self = [super init];
   if (self) {
     _data = data;
     _fieldMask = std::move(fieldMask);
-    _fieldTransforms = fieldTransforms;
+    _fieldTransforms = std::move(fieldTransforms);
   }
   return self;
 }
@@ -129,7 +138,7 @@ static NSString *const RESERVED_FIELD_DESIGNATOR = @"__";
                                                    fieldMask:self.fieldMask
                                                        value:self.data
                                                 precondition:precondition]];
-  if (self.fieldTransforms.count > 0) {
+  if (!self.fieldTransforms.empty()) {
     [mutations addObject:[[FSTTransformMutation alloc] initWithKey:key
                                                    fieldTransforms:self.fieldTransforms]];
   }
@@ -140,6 +149,10 @@ static NSString *const RESERVED_FIELD_DESIGNATOR = @"__";
   return _fieldMask;
 }
 
+- (const std::vector<FieldTransform> &)fieldTransforms {
+  return _fieldTransforms;
+}
+
 @end
 
 /**
@@ -168,7 +181,6 @@ typedef NS_ENUM(NSInteger, FSTUserDataSource) {
  * conditions apply during parsing and providing better error messages.
  */
 @property(nonatomic, assign) FSTUserDataSource dataSource;
-@property(nonatomic, strong, readonly) NSMutableArray<FSTFieldTransform *> *fieldTransforms;
 
 - (instancetype)init NS_UNAVAILABLE;
 /**
@@ -186,7 +198,7 @@ typedef NS_ENUM(NSInteger, FSTUserDataSource) {
 - (instancetype)initWithSource:(FSTUserDataSource)dataSource
                           path:(std::unique_ptr<FieldPath>)path
                   arrayElement:(BOOL)arrayElement
-               fieldTransforms:(NSMutableArray<FSTFieldTransform *> *)fieldTransforms
+               fieldTransforms:(std::shared_ptr<std::vector<FieldTransform>>)fieldTransforms
                      fieldMask:(std::shared_ptr<std::vector<FieldPath>>)fieldMask
     NS_DESIGNATED_INITIALIZER;
 
@@ -204,16 +216,22 @@ typedef NS_ENUM(NSInteger, FSTUserDataSource) {
 
 - (void)appendToFieldMaskWithFieldPath:(FieldPath)fieldPath;
 
+- (const std::vector<FieldTransform> *)fieldTransforms;
+
+- (void)appendToFieldTransformsWithFieldPath:(FieldPath)fieldPath
+                          transformOperation:
+                              (std::unique_ptr<TransformOperation>)transformOperation;
 @end
 
 @implementation FSTParseContext {
   /** The current path being parsed. */
   // TODO(b/34871131): path should never be nullptr, but we don't support array paths right now.
   std::unique_ptr<FieldPath> _path;
-  // _fieldMask is shared across all active context objects to accumulate the result. For example,
-  // the result of calling any of contextForField, contextForFieldPath and contextForArrayIndex
-  // shares the ownership of _fieldMask.
+  // _fieldMask and _fieldTransforms are shared across all active context objects to accumulate the
+  // result. For example, the result of calling any of contextForField, contextForFieldPath and
+  // contextForArrayIndex shares the ownership of _fieldMask and _fieldTransforms.
   std::shared_ptr<std::vector<FieldPath>> _fieldMask;
+  std::shared_ptr<std::vector<FieldTransform>> _fieldTransforms;
 }
 
 + (instancetype)contextWithSource:(FSTUserDataSource)dataSource
@@ -222,7 +240,7 @@ typedef NS_ENUM(NSInteger, FSTUserDataSource) {
       [[FSTParseContext alloc] initWithSource:dataSource
                                          path:std::move(path)
                                  arrayElement:NO
-                              fieldTransforms:[NSMutableArray array]
+                              fieldTransforms:std::make_shared<std::vector<FieldTransform>>()
                                     fieldMask:std::make_shared<std::vector<FieldPath>>()];
   [context validatePath];
   return context;
@@ -231,13 +249,13 @@ typedef NS_ENUM(NSInteger, FSTUserDataSource) {
 - (instancetype)initWithSource:(FSTUserDataSource)dataSource
                           path:(std::unique_ptr<FieldPath>)path
                   arrayElement:(BOOL)arrayElement
-               fieldTransforms:(NSMutableArray<FSTFieldTransform *> *)fieldTransforms
+               fieldTransforms:(std::shared_ptr<std::vector<FieldTransform>>)fieldTransforms
                      fieldMask:(std::shared_ptr<std::vector<FieldPath>>)fieldMask {
   if (self = [super init]) {
     _dataSource = dataSource;
     _path = std::move(path);
     _arrayElement = arrayElement;
-    _fieldTransforms = fieldTransforms;
+    _fieldTransforms = std::move(fieldTransforms);
     _fieldMask = std::move(fieldMask);
   }
   return self;
@@ -251,7 +269,7 @@ typedef NS_ENUM(NSInteger, FSTUserDataSource) {
   FSTParseContext *context = [[FSTParseContext alloc] initWithSource:self.dataSource
                                                                 path:std::move(path)
                                                         arrayElement:NO
-                                                     fieldTransforms:self.fieldTransforms
+                                                     fieldTransforms:_fieldTransforms
                                                            fieldMask:_fieldMask];
   [context validatePathSegment:fieldName];
   return context;
@@ -265,7 +283,7 @@ typedef NS_ENUM(NSInteger, FSTUserDataSource) {
   FSTParseContext *context = [[FSTParseContext alloc] initWithSource:self.dataSource
                                                                 path:std::move(path)
                                                         arrayElement:NO
-                                                     fieldTransforms:self.fieldTransforms
+                                                     fieldTransforms:_fieldTransforms
                                                            fieldMask:_fieldMask];
   [context validatePath];
   return context;
@@ -276,7 +294,7 @@ typedef NS_ENUM(NSInteger, FSTUserDataSource) {
   return [[FSTParseContext alloc] initWithSource:self.dataSource
                                             path:nil
                                     arrayElement:YES
-                                 fieldTransforms:self.fieldTransforms
+                                 fieldTransforms:_fieldTransforms
                                        fieldMask:_fieldMask];
 }
 
@@ -335,6 +353,16 @@ typedef NS_ENUM(NSInteger, FSTUserDataSource) {
   _fieldMask->push_back(std::move(fieldPath));
 }
 
+- (const std::vector<FieldTransform> *)fieldTransforms {
+  return _fieldTransforms.get();
+}
+
+- (void)appendToFieldTransformsWithFieldPath:(FieldPath)fieldPath
+                          transformOperation:
+                              (std::unique_ptr<TransformOperation>)transformOperation {
+  _fieldTransforms->emplace_back(std::move(fieldPath), std::move(transformOperation));
+}
+
 @end
 
 #pragma mark - FSTDocumentKeyReference
@@ -392,7 +420,7 @@ typedef NS_ENUM(NSInteger, FSTUserDataSource) {
 
   return [[FSTParsedSetData alloc] initWithData:updateData
                                       fieldMask:FieldMask{*context.fieldMask}
-                                fieldTransforms:context.fieldTransforms];
+                                fieldTransforms:*context.fieldTransforms];
 }
 
 - (FSTParsedSetData *)parsedSetData:(id)input {
@@ -407,7 +435,8 @@ typedef NS_ENUM(NSInteger, FSTUserDataSource) {
                                     path:absl::make_unique<FieldPath>(FieldPath::EmptyPath())];
   FSTObjectValue *updateData = (FSTObjectValue *)[self parseData:input context:context];
 
-  return [[FSTParsedSetData alloc] initWithData:updateData fieldTransforms:context.fieldTransforms];
+  return
+      [[FSTParsedSetData alloc] initWithData:updateData fieldTransforms:*context.fieldTransforms];
 }
 
 - (FSTParsedUpdateData *)parsedUpdateData:(id)input {
@@ -453,7 +482,7 @@ typedef NS_ENUM(NSInteger, FSTUserDataSource) {
 
   return [[FSTParsedUpdateData alloc] initWithData:updateData
                                          fieldMask:FieldMask{fieldMaskPaths}
-                                   fieldTransforms:context.fieldTransforms];
+                                   fieldTransforms:*context.fieldTransforms];
 }
 
 - (FSTFieldValue *)parsedQueryValue:(id)input {
@@ -462,7 +491,7 @@ typedef NS_ENUM(NSInteger, FSTUserDataSource) {
                                     path:absl::make_unique<FieldPath>(FieldPath::EmptyPath())];
   FSTFieldValue *_Nullable parsed = [self parseData:input context:context];
   FSTAssert(parsed, @"Parsed data should not be nil.");
-  FSTAssert(context.fieldTransforms.count == 0, @"Field transforms should have been disallowed.");
+  FSTAssert(context.fieldTransforms->empty(), @"Field transforms should have been disallowed.");
   return parsed;
 }
 
@@ -661,11 +690,9 @@ typedef NS_ENUM(NSInteger, FSTUserDataSource) {
             @"FieldValue.serverTimestamp() is not currently supported inside arrays%@",
             [context fieldDescription]);
       }
-      [context.fieldTransforms
-          addObject:[[FSTFieldTransform alloc]
-                        initWithPath:*context.path
-                           transform:absl::make_unique<ServerTimestampTransform>(
-                                         ServerTimestampTransform::Get())]];
+      [context appendToFieldTransformsWithFieldPath:*context.path
+                                 transformOperation:absl::make_unique<ServerTimestampTransform>(
+                                                        ServerTimestampTransform::Get())];
 
       // Return nil so this value is omitted from the parsed result.
       return nil;