1 files changed, 45 insertions, 0 deletions
diff --git a/Firestore/Source/Local/FSTWriteGroupTracker.h b/Firestore/Source/Local/FSTWriteGroupTracker.h
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--- /dev/null
+++ b/Firestore/Source/Local/FSTWriteGroupTracker.h
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+/*
+ * Copyright 2017 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.
+ */
+
+#import <Foundation/Foundation.h>
+
+@class FSTWriteGroup;
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * Helper class for FSTPersistence implementations to create WriteGroups and verify internal
+ * contracts are maintained:
+ * 1. Can't create a group when an uncommitted group exists (no nesting).
+ * 2. Can't commit a group that differs from the last created one.
+ */
+@interface FSTWriteGroupTracker : NSObject
+
+/** Creates and returns an FSTWriteGroupTracker instance. */
++ (instancetype)tracker;
+
+/**
+ * Verifies there's no active group already and then creates a new group and stores it for later
+ * validation with `endGroup`.
+ */
+- (FSTWriteGroup *)startGroupWithAction:(NSString *)action;
+
+/** Ends a group previously started with `startGroupWithAction`. */
+- (void)endGroup:(FSTWriteGroup *)group;
+
+@end
+
+NS_ASSUME_NONNULL_END