port FieldMask to C++ (#998)

* port FieldMask to C++

* address changes

* address changes

* fix test

* address change

* fix lint

* address changes

* Revert "address changes"

This reverts commit c75bb42851b785ab0838bb23679f87dfad9df4bb.

2 files changed, 24 insertions, 78 deletions

diff --git a/Firestore/Source/Model/FSTMutation.h b/Firestore/Source/Model/FSTMutation.h
index 4e4357d..2b81af6 100644
--- a/Firestore/Source/Model/FSTMutation.h
+++ b/Firestore/Source/Model/FSTMutation.h
@@ -19,6 +19,7 @@
 #include <vector>
 
 #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"
 
 @class FSTDocument;
@@ -30,31 +31,6 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
-#pragma mark - FSTFieldMask
-
-/**
- * Provides a set of fields that can be used to partially patch a document. FieldMask is used in
- * conjunction with ObjectValue.
- *
- * Examples:
- *   foo - Overwrites foo entirely with the provided value. If foo is not present in the companion
- *       ObjectValue, the field is deleted.
- *   foo.bar - Overwrites only the field bar of the object foo. If foo is not an object, foo is
- *       replaced with an object containing bar.
- */
-@interface FSTFieldMask : NSObject
-- (id)init __attribute__((unavailable("Use initWithFields:")));
-
-/**
- * Initializes the field mask with the given field paths. Caller is expected to either copy or
- * or release the array of fields.
- */
-- (instancetype)initWithFields:(std::vector<firebase::firestore::model::FieldPath>)fields
-    NS_DESIGNATED_INITIALIZER;
-
-- (const std::vector<firebase::firestore::model::FieldPath> &)fields;
-@end
-
 #pragma mark - FSTFieldTransform
 
 /** Represents a transform within a TransformMutation. */
@@ -267,7 +243,7 @@ typedef NS_ENUM(NSUInteger, FSTPreconditionExists) {
                precondition:(FSTPrecondition *)precondition NS_UNAVAILABLE;
 
 /**
- * Initializes a new patch mutation with an explicit FSTFieldMask and FSTObjectValue representing
+ * Initializes a new patch mutation with an explicit FieldMask and FSTObjectValue representing
  * the updates to perform
  *
  * @param key Identifies the location of the document to mutate.
@@ -278,18 +254,18 @@ typedef NS_ENUM(NSUInteger, FSTPreconditionExists) {
  * @param precondition The precondition for this mutation.
  */
 - (instancetype)initWithKey:(firebase::firestore::model::DocumentKey)key
-                  fieldMask:(FSTFieldMask *)fieldMask
+                  fieldMask:(firebase::firestore::model::FieldMask)fieldMask
                       value:(FSTObjectValue *)value
                precondition:(FSTPrecondition *)precondition NS_DESIGNATED_INITIALIZER;
 
-/** The fields and associated values to use when patching the document. */
-@property(nonatomic, strong, readonly) FSTObjectValue *value;
-
 /**
  * A mask to apply to |value|, where only fields that are in both the fieldMask and the value
  * will be updated.
  */
-@property(nonatomic, strong, readonly) FSTFieldMask *fieldMask;
+- (const firebase::firestore::model::FieldMask &)fieldMask;
+
+/** The fields and associated values to use when patching the document. */
+@property(nonatomic, strong, readonly) FSTObjectValue *value;
 
 @end
 
diff --git a/Firestore/Source/Model/FSTMutation.mm b/Firestore/Source/Model/FSTMutation.mm
index 253a853..df95155 100644
--- a/Firestore/Source/Model/FSTMutation.mm
+++ b/Firestore/Source/Model/FSTMutation.mm
@@ -27,51 +27,15 @@
 #import "Firestore/Source/Util/FSTClasses.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_path.h"
 
 using firebase::firestore::model::DocumentKey;
+using firebase::firestore::model::FieldMask;
 using firebase::firestore::model::FieldPath;
 
 NS_ASSUME_NONNULL_BEGIN
 
-#pragma mark - FSTFieldMask
-
-@implementation FSTFieldMask {
-  std::vector<FieldPath> _fields;
-}
-
-- (instancetype)initWithFields:(std::vector<FieldPath>)fields {
-  if (self = [super init]) {
-    _fields = std::move(fields);
-  }
-  return self;
-}
-
-- (BOOL)isEqual:(id)other {
-  if (other == self) {
-    return YES;
-  }
-  if (![other isKindOfClass:[FSTFieldMask class]]) {
-    return NO;
-  }
-
-  FSTFieldMask *otherMask = (FSTFieldMask *)other;
-  return _fields == otherMask->_fields;
-}
-
-- (NSUInteger)hash {
-  NSUInteger hashResult = 0;
-  for (const FieldPath &field : _fields) {
-    hashResult = hashResult * 31u + field.Hash();
-  }
-  return hashResult;
-}
-
-- (const std::vector<FieldPath> &)fields {
-  return _fields;
-}
-@end
-
 #pragma mark - FSTServerTimestampTransform
 
 @implementation FSTServerTimestampTransform
@@ -354,20 +318,26 @@ NS_ASSUME_NONNULL_BEGIN
 
 #pragma mark - FSTPatchMutation
 
-@implementation FSTPatchMutation
+@implementation FSTPatchMutation {
+  FieldMask _fieldMask;
+}
 
 - (instancetype)initWithKey:(DocumentKey)key
-                  fieldMask:(FSTFieldMask *)fieldMask
+                  fieldMask:(FieldMask)fieldMask
                       value:(FSTObjectValue *)value
                precondition:(FSTPrecondition *)precondition {
   self = [super initWithKey:std::move(key) precondition:precondition];
   if (self) {
-    _fieldMask = fieldMask;
+    _fieldMask = std::move(fieldMask);
     _value = value;
   }
   return self;
 }
 
+- (const firebase::firestore::model::FieldMask &)fieldMask {
+  return _fieldMask;
+}
+
 - (BOOL)isEqual:(id)other {
   if (other == self) {
     return YES;
@@ -377,7 +347,7 @@ NS_ASSUME_NONNULL_BEGIN
   }
 
   FSTPatchMutation *otherMutation = (FSTPatchMutation *)other;
-  return [self.key isEqual:otherMutation.key] && [self.fieldMask isEqual:otherMutation.fieldMask] &&
+  return [self.key isEqual:otherMutation.key] && self.fieldMask == otherMutation.fieldMask &&
          [self.value isEqual:otherMutation.value] &&
          [self.precondition isEqual:otherMutation.precondition];
 }
@@ -385,15 +355,15 @@ NS_ASSUME_NONNULL_BEGIN
 - (NSUInteger)hash {
   NSUInteger result = [self.key hash];
   result = 31 * result + [self.precondition hash];
-  result = 31 * result + [self.fieldMask hash];
+  result = 31 * result + self.fieldMask.Hash();
   result = 31 * result + [self.value hash];
   return result;
 }
 
 - (NSString *)description {
-  return [NSString stringWithFormat:@"<FSTPatchMutation key=%s mask=%@ value=%@ precondition=%@>",
-                                    self.key.ToString().c_str(), self.fieldMask, self.value,
-                                    self.precondition];
+  return [NSString stringWithFormat:@"<FSTPatchMutation key=%s mask=%s value=%@ precondition=%@>",
+                                    self.key.ToString().c_str(), self.fieldMask.ToString().c_str(),
+                                    self.value, self.precondition];
 }
 
 - (nullable FSTMaybeDocument *)applyTo:(nullable FSTMaybeDocument *)maybeDoc
@@ -434,7 +404,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (FSTObjectValue *)patchObjectValue:(FSTObjectValue *)objectValue {
   FSTObjectValue *result = objectValue;
-  for (const FieldPath &fieldPath : self.fieldMask.fields) {
+  for (const FieldPath &fieldPath : self.fieldMask) {
     FSTFieldValue *newValue = [self.value valueForPath:fieldPath];
     if (newValue) {
       result = [result objectBySettingValue:newValue forPath:fieldPath];