1 files changed, 55 insertions, 0 deletions
diff --git a/Firestore/Source/Core/FSTTargetIDGenerator.h b/Firestore/Source/Core/FSTTargetIDGenerator.h
new file mode 100644
index 0000000..5b9db10
--- /dev/null
+++ b/Firestore/Source/Core/FSTTargetIDGenerator.h
@@ -0,0 +1,55 @@
+/*
+ * 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>
+
+#import "FSTTypes.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * FSTTargetIDGenerator generates monotonically increasing integer IDs. There are separate
+ * generators for different scopes. While these generators will operate independently of each
+ * other, they are scoped, such that no two generators will ever produce the same ID. This is
+ * useful, because sometimes the backend may group IDs from separate parts of the client into the
+ * same ID space.
+ */
+@interface FSTTargetIDGenerator : NSObject
+
+/**
+ * Creates and returns the FSTTargetIDGenerator for the local store.
+ *
+ * @param after An ID to start at. Every call to nextID will return an ID > @a after.
+ * @return A shared instance of FSTTargetIDGenerator.
+ */
++ (instancetype)generatorForLocalStoreStartingAfterID:(FSTTargetID)after;
+
+/**
+ * Creates and returns the FSTTargetIDGenerator for the sync engine.
+ *
+ * @param after An ID to start at. Every call to nextID will return an ID > @a after.
+ * @return A shared instance of FSTTargetIDGenerator.
+ */
++ (instancetype)generatorForSyncEngineStartingAfterID:(FSTTargetID)after;
+
+- (id)init __attribute__((unavailable("Use a static constructor method.")));
+
+/** Returns the next ID in the sequence. */
+- (FSTTargetID)nextID;
+
+@end
+
+NS_ASSUME_NONNULL_END