port TargetIdGenerator to iOS (#709)

* port TargetIdGenerator to iOS

* fix style

* move pointer property to instance variable

* TriggerTravis

7 files changed, 24 insertions, 272 deletions

diff --git a/Firestore/Example/Firestore.xcodeproj/project.pbxproj b/Firestore/Example/Firestore.xcodeproj/project.pbxproj
index 7bc57fc..7c6508a 100644
--- a/Firestore/Example/Firestore.xcodeproj/project.pbxproj
+++ b/Firestore/Example/Firestore.xcodeproj/project.pbxproj
@@ -111,7 +111,6 @@
 		DE51B1CE1F0D48CD0013853F /* FSTEventManagerTests.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B1AA1F0D48AC0013853F /* FSTEventManagerTests.m */; };
 		DE51B1CF1F0D48CD0013853F /* FSTQueryListenerTests.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B1AB1F0D48AC0013853F /* FSTQueryListenerTests.m */; };
 		DE51B1D01F0D48CD0013853F /* FSTQueryTests.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B1AC1F0D48AC0013853F /* FSTQueryTests.m */; };
-		DE51B1D11F0D48CD0013853F /* FSTTargetIDGeneratorTests.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B1AE1F0D48AC0013853F /* FSTTargetIDGeneratorTests.m */; };
 		DE51B1D21F0D48CD0013853F /* FSTTimestampTests.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B1AF1F0D48AC0013853F /* FSTTimestampTests.m */; };
 		DE51B1D31F0D48CD0013853F /* FSTViewSnapshotTest.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B1B01F0D48AC0013853F /* FSTViewSnapshotTest.m */; };
 		DE51B1D41F0D48CD0013853F /* FSTViewTests.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B1B11F0D48AC0013853F /* FSTViewTests.m */; };
@@ -331,7 +330,6 @@
 		DE51B1AB1F0D48AC0013853F /* FSTQueryListenerTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTQueryListenerTests.m; sourceTree = "<group>"; };
 		DE51B1AC1F0D48AC0013853F /* FSTQueryTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTQueryTests.m; sourceTree = "<group>"; };
 		DE51B1AD1F0D48AC0013853F /* FSTSyncEngine+Testing.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = "FSTSyncEngine+Testing.h"; sourceTree = "<group>"; };
-		DE51B1AE1F0D48AC0013853F /* FSTTargetIDGeneratorTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTTargetIDGeneratorTests.m; sourceTree = "<group>"; };
 		DE51B1AF1F0D48AC0013853F /* FSTTimestampTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTTimestampTests.m; sourceTree = "<group>"; };
 		DE51B1B01F0D48AC0013853F /* FSTViewSnapshotTest.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTViewSnapshotTest.m; sourceTree = "<group>"; };
 		DE51B1B11F0D48AC0013853F /* FSTViewTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTViewTests.m; sourceTree = "<group>"; };
@@ -718,7 +716,6 @@
 				DE51B1AA1F0D48AC0013853F /* FSTEventManagerTests.m */,
 				DE51B1AB1F0D48AC0013853F /* FSTQueryListenerTests.m */,
 				DE51B1AC1F0D48AC0013853F /* FSTQueryTests.m */,
-				DE51B1AE1F0D48AC0013853F /* FSTTargetIDGeneratorTests.m */,
 				DE51B1AF1F0D48AC0013853F /* FSTTimestampTests.m */,
 				DE51B1B01F0D48AC0013853F /* FSTViewSnapshotTest.m */,
 				DE51B1B11F0D48AC0013853F /* FSTViewTests.m */,
@@ -1253,7 +1250,6 @@
 				DE51B1F41F0D491B0013853F /* FSTRemoteEventTests.m in Sources */,
 				548DB927200D590300E00ABC /* assert_test.cc in Sources */,
 				54E928241F33953300C1953E /* FSTEventAccumulator.m in Sources */,
-				DE51B1D11F0D48CD0013853F /* FSTTargetIDGeneratorTests.m in Sources */,
 				5436F32420008FAD006E51E3 /* string_printf_test.cc in Sources */,
 				DE51B1EF1F0D49140013853F /* FSTDocumentTests.m in Sources */,
 				DE51B1DC1F0D490D0013853F /* FSTLocalSerializerTests.m in Sources */,
diff --git a/Firestore/Example/Tests/Core/FSTTargetIDGeneratorTests.m b/Firestore/Example/Tests/Core/FSTTargetIDGeneratorTests.m
deleted file mode 100644
index 6f54fd1..0000000
--- a/Firestore/Example/Tests/Core/FSTTargetIDGeneratorTests.m
+++ /dev/null
@@ -1,94 +0,0 @@
-/*
- * 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 "Firestore/Source/Core/FSTTargetIDGenerator.h"
-
-#import <XCTest/XCTest.h>
-
-NS_ASSUME_NONNULL_BEGIN
-
-@interface FSTTargetIDGenerator ()
-- (instancetype)initWithGeneratorID:(NSInteger)generatorID startingAfterID:(FSTTargetID)after;
-@end
-
-@interface FSTTargetIDGeneratorTests : XCTestCase
-@end
-
-@implementation FSTTargetIDGeneratorTests
-
-- (void)testConstructor {
-  XCTAssertEqual([[[FSTTargetIDGenerator alloc] initWithGeneratorID:0 startingAfterID:0] nextID],
-                 2);
-  XCTAssertEqual([[[FSTTargetIDGenerator alloc] initWithGeneratorID:1 startingAfterID:0] nextID],
-                 1);
-
-  XCTAssertEqual([[FSTTargetIDGenerator generatorForLocalStoreStartingAfterID:0] nextID], 2);
-  XCTAssertEqual([[FSTTargetIDGenerator generatorForSyncEngineStartingAfterID:0] nextID], 1);
-}
-
-- (void)testSkipPast {
-  FSTTargetIDGenerator *gen =
-      [[FSTTargetIDGenerator alloc] initWithGeneratorID:1 startingAfterID:-1];
-  XCTAssertEqual([gen nextID], 1);
-
-  gen = [[FSTTargetIDGenerator alloc] initWithGeneratorID:1 startingAfterID:2];
-  XCTAssertEqual([gen nextID], 3);
-
-  gen = [[FSTTargetIDGenerator alloc] initWithGeneratorID:1 startingAfterID:4];
-  XCTAssertEqual([gen nextID], 5);
-
-  for (int i = 4; i < 12; ++i) {
-    FSTTargetIDGenerator *gen0 =
-        [[FSTTargetIDGenerator alloc] initWithGeneratorID:0 startingAfterID:i];
-    FSTTargetIDGenerator *gen1 =
-        [[FSTTargetIDGenerator alloc] initWithGeneratorID:1 startingAfterID:i];
-    XCTAssertEqual([gen0 nextID], i + 2 & ~1, @"Skip failed for index %d", i);
-    XCTAssertEqual([gen1 nextID], i + 1 | 1, @"Skip failed for index %d", i);
-  }
-
-  gen = [[FSTTargetIDGenerator alloc] initWithGeneratorID:1 startingAfterID:12];
-  XCTAssertEqual([gen nextID], 13);
-
-  gen = [[FSTTargetIDGenerator alloc] initWithGeneratorID:0 startingAfterID:22];
-  XCTAssertEqual([gen nextID], 24);
-}
-
-- (void)testIncrement {
-  FSTTargetIDGenerator *gen =
-      [[FSTTargetIDGenerator alloc] initWithGeneratorID:0 startingAfterID:0];
-  XCTAssertEqual([gen nextID], 2);
-  XCTAssertEqual([gen nextID], 4);
-  XCTAssertEqual([gen nextID], 6);
-  gen = [[FSTTargetIDGenerator alloc] initWithGeneratorID:0 startingAfterID:46];
-  XCTAssertEqual([gen nextID], 48);
-  XCTAssertEqual([gen nextID], 50);
-  XCTAssertEqual([gen nextID], 52);
-  XCTAssertEqual([gen nextID], 54);
-
-  gen = [[FSTTargetIDGenerator alloc] initWithGeneratorID:1 startingAfterID:0];
-  XCTAssertEqual([gen nextID], 1);
-  XCTAssertEqual([gen nextID], 3);
-  XCTAssertEqual([gen nextID], 5);
-  gen = [[FSTTargetIDGenerator alloc] initWithGeneratorID:1 startingAfterID:46];
-  XCTAssertEqual([gen nextID], 47);
-  XCTAssertEqual([gen nextID], 49);
-  XCTAssertEqual([gen nextID], 51);
-  XCTAssertEqual([gen nextID], 53);
-}
-
-@end
-
-NS_ASSUME_NONNULL_END
diff --git a/Firestore/Source/Core/FSTSyncEngine.m b/Firestore/Source/Core/FSTSyncEngine.mm
index f90c5dd..d82cc99 100644
--- a/Firestore/Source/Core/FSTSyncEngine.m
+++ b/Firestore/Source/Core/FSTSyncEngine.mm
@@ -22,7 +22,6 @@
 #import "Firestore/Source/Auth/FSTUser.h"
 #import "Firestore/Source/Core/FSTQuery.h"
 #import "Firestore/Source/Core/FSTSnapshotVersion.h"
-#import "Firestore/Source/Core/FSTTargetIDGenerator.h"
 #import "Firestore/Source/Core/FSTTransaction.h"
 #import "Firestore/Source/Core/FSTView.h"
 #import "Firestore/Source/Core/FSTViewSnapshot.h"
@@ -41,6 +40,8 @@
 #import "Firestore/Source/Util/FSTDispatchQueue.h"
 #import "Firestore/Source/Util/FSTLogger.h"
 
+#include "Firestore/core/src/firebase/firestore/core/target_id_generator.h"
+
 NS_ASSUME_NONNULL_BEGIN
 
 // Limbo documents don't use persistence, and are eagerly GC'd. So, listens for them don't need
@@ -141,14 +142,14 @@ static const FSTListenSequenceNumber kIrrelevantSequenceNumber = -1;
     NSMutableDictionary<FSTUser *, NSMutableDictionary<NSNumber *, FSTVoidErrorBlock> *>
         *mutationCompletionBlocks;
 
-/** Used for creating the FSTTargetIDs for the listens used to resolve limbo documents. */
-@property(nonatomic, strong, readonly) FSTTargetIDGenerator *targetIdGenerator;
-
 @property(nonatomic, strong) FSTUser *currentUser;
 
 @end
 
-@implementation FSTSyncEngine
+@implementation FSTSyncEngine {
+  /** Used for creating the FSTTargetIDs for the listens used to resolve limbo documents. */
+  firebase::firestore::core::TargetIdGenerator _targetIdGenerator;
+}
 
 - (instancetype)initWithLocalStore:(FSTLocalStore *)localStore
                        remoteStore:(FSTRemoteStore *)remoteStore
@@ -167,7 +168,8 @@ static const FSTListenSequenceNumber kIrrelevantSequenceNumber = -1;
     [_limboCollector addGarbageSource:_limboDocumentRefs];
 
     _mutationCompletionBlocks = [NSMutableDictionary dictionary];
-    _targetIdGenerator = [FSTTargetIDGenerator generatorForSyncEngineStartingAfterID:0];
+    _targetIdGenerator =
+        firebase::firestore::core::TargetIdGenerator::SyncEngineTargetIdGenerator(0);
     _currentUser = initialUser;
   }
   return self;
@@ -490,7 +492,7 @@ static const FSTListenSequenceNumber kIrrelevantSequenceNumber = -1;
 
   if (!self.limboTargetsByKey[key]) {
     FSTLog(@"New document in limbo: %@", key);
-    FSTTargetID limboTargetID = [self.targetIdGenerator nextID];
+    FSTTargetID limboTargetID = _targetIdGenerator.NextId();
     FSTQuery *query = [FSTQuery queryWithPath:key.path];
     FSTQueryData *queryData = [[FSTQueryData alloc] initWithQuery:query
                                                          targetID:limboTargetID
diff --git a/Firestore/Source/Core/FSTTargetIDGenerator.h b/Firestore/Source/Core/FSTTargetIDGenerator.h
deleted file mode 100644
index 0b230ae..0000000
--- a/Firestore/Source/Core/FSTTargetIDGenerator.h
+++ /dev/null
@@ -1,55 +0,0 @@
-/*
- * 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 "Firestore/Source/Core/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
diff --git a/Firestore/Source/Core/FSTTargetIDGenerator.m b/Firestore/Source/Core/FSTTargetIDGenerator.m
deleted file mode 100644
index 58092ec..0000000
--- a/Firestore/Source/Core/FSTTargetIDGenerator.m
+++ /dev/null
@@ -1,105 +0,0 @@
-/*
- * 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 "Firestore/Source/Core/FSTTargetIDGenerator.h"
-
-#import <libkern/OSAtomic.h>
-
-NS_ASSUME_NONNULL_BEGIN
-
-#pragma mark - FSTTargetIDGenerator
-
-static const int kReservedBits = 1;
-
-/** FSTTargetIDGeneratorID is the set of all valid generators. */
-typedef NS_ENUM(NSInteger, FSTTargetIDGeneratorID) {
-  FSTTargetIDGeneratorIDLocalStore = 0,
-  FSTTargetIDGeneratorIDSyncEngine = 1
-};
-
-@interface FSTTargetIDGenerator () {
-  // This is volatile so it can be used with OSAtomicAdd32.
-  volatile FSTTargetID _previousID;
-}
-
-/**
- * Initializes the generator.
- *
- * @param generatorID A unique ID indicating which generator this is.
- * @param after Every call to nextID will return a number > @a after.
- */
-- (instancetype)initWithGeneratorID:(FSTTargetIDGeneratorID)generatorID
-                    startingAfterID:(FSTTargetID)after NS_DESIGNATED_INITIALIZER;
-
-// This is typed as FSTTargetID because we need to do bitwise operations with them together.
-@property(nonatomic, assign) FSTTargetID generatorID;
-@end
-
-@implementation FSTTargetIDGenerator
-
-#pragma mark - Constructors
-
-- (instancetype)initWithGeneratorID:(FSTTargetIDGeneratorID)generatorID
-                    startingAfterID:(FSTTargetID)after {
-  self = [super init];
-  if (self) {
-    _generatorID = generatorID;
-
-    // Replace the generator part of |after| with this generator's ID.
-    FSTTargetID afterWithoutGenerator = (after >> kReservedBits) << kReservedBits;
-    FSTTargetID afterGenerator = after - afterWithoutGenerator;
-    if (afterGenerator >= _generatorID) {
-      // For example, if:
-      //   self.generatorID = 0b0000
-      //   after = 0b1011
-      //   afterGenerator = 0b0001
-      // Then:
-      //   previous = 0b1010
-      //   next = 0b1100
-      _previousID = afterWithoutGenerator | self.generatorID;
-    } else {
-      // For example, if:
-      //   self.generatorID = 0b0001
-      //   after = 0b1010
-      //   afterGenerator = 0b0000
-      // Then:
-      //   previous = 0b1001
-      //   next = 0b1011
-      _previousID = (afterWithoutGenerator | self.generatorID) - (1 << kReservedBits);
-    }
-  }
-  return self;
-}
-
-+ (instancetype)generatorForLocalStoreStartingAfterID:(FSTTargetID)after {
-  return [[FSTTargetIDGenerator alloc] initWithGeneratorID:FSTTargetIDGeneratorIDLocalStore
-                                           startingAfterID:after];
-}
-
-+ (instancetype)generatorForSyncEngineStartingAfterID:(FSTTargetID)after {
-  return [[FSTTargetIDGenerator alloc] initWithGeneratorID:FSTTargetIDGeneratorIDSyncEngine
-                                           startingAfterID:after];
-}
-
-#pragma mark - Public methods
-
-- (FSTTargetID)nextID {
-  return OSAtomicAdd32(1 << kReservedBits, &_previousID);
-}
-
-@end
-
-NS_ASSUME_NONNULL_END
diff --git a/Firestore/Source/Local/FSTLocalStore.m b/Firestore/Source/Local/FSTLocalStore.mm
index 3a5b0b4..fa77e37 100644
--- a/Firestore/Source/Local/FSTLocalStore.m
+++ b/Firestore/Source/Local/FSTLocalStore.mm
@@ -20,7 +20,6 @@
 #import "Firestore/Source/Core/FSTListenSequence.h"
 #import "Firestore/Source/Core/FSTQuery.h"
 #import "Firestore/Source/Core/FSTSnapshotVersion.h"
-#import "Firestore/Source/Core/FSTTargetIDGenerator.h"
 #import "Firestore/Source/Core/FSTTimestamp.h"
 #import "Firestore/Source/Local/FSTGarbageCollector.h"
 #import "Firestore/Source/Local/FSTLocalDocumentsView.h"
@@ -42,6 +41,8 @@
 #import "Firestore/Source/Util/FSTAssert.h"
 #import "Firestore/Source/Util/FSTLogger.h"
 
+#include "Firestore/core/src/firebase/firestore/core/target_id_generator.h"
+
 NS_ASSUME_NONNULL_BEGIN
 
 @interface FSTLocalStore ()
@@ -74,9 +75,6 @@ NS_ASSUME_NONNULL_BEGIN
 /** Maps a targetID to data about its query. */
 @property(nonatomic, strong) NSMutableDictionary<NSNumber *, FSTQueryData *> *targetIDs;
 
-/** Used to generate targetIDs for queries tracked locally. */
-@property(nonatomic, strong) FSTTargetIDGenerator *targetIDGenerator;
-
 @property(nonatomic, strong) FSTListenSequence *listenSequence;
 
 /**
@@ -92,7 +90,10 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
-@implementation FSTLocalStore
+@implementation FSTLocalStore {
+  /** Used to generate targetIDs for queries tracked locally. */
+  firebase::firestore::core::TargetIdGenerator _targetIDGenerator;
+}
 
 - (instancetype)initWithPersistence:(id<FSTPersistence>)persistence
                    garbageCollector:(id<FSTGarbageCollector>)garbageCollector
@@ -113,6 +114,9 @@ NS_ASSUME_NONNULL_BEGIN
 
     _targetIDs = [NSMutableDictionary dictionary];
     _heldBatchResults = [NSMutableArray array];
+
+    _targetIDGenerator =
+        firebase::firestore::core::TargetIdGenerator::LocalStoreTargetIdGenerator(0);
   }
   return self;
 }
@@ -150,7 +154,8 @@ NS_ASSUME_NONNULL_BEGIN
   [self.queryCache start];
 
   FSTTargetID targetID = [self.queryCache highestTargetID];
-  self.targetIDGenerator = [FSTTargetIDGenerator generatorForLocalStoreStartingAfterID:targetID];
+  _targetIDGenerator =
+      firebase::firestore::core::TargetIdGenerator::LocalStoreTargetIdGenerator(targetID);
   FSTListenSequenceNumber sequenceNumber = [self.queryCache highestListenSequenceNumber];
   self.listenSequence = [[FSTListenSequence alloc] initStartingAfter:sequenceNumber];
 }
@@ -393,7 +398,7 @@ NS_ASSUME_NONNULL_BEGIN
   } else {
     FSTWriteGroup *group = [self.persistence startGroupWithAction:@"Allocate query"];
 
-    targetID = [self.targetIDGenerator nextID];
+    targetID = _targetIDGenerator.NextId();
     cached = [[FSTQueryData alloc] initWithQuery:query
                                         targetID:targetID
                             listenSequenceNumber:sequenceNumber
diff --git a/Firestore/core/src/firebase/firestore/core/target_id_generator.h b/Firestore/core/src/firebase/firestore/core/target_id_generator.h
index 345f141..7d30cf9 100644
--- a/Firestore/core/src/firebase/firestore/core/target_id_generator.h
+++ b/Firestore/core/src/firebase/firestore/core/target_id_generator.h
@@ -37,6 +37,9 @@ enum class TargetIdGeneratorId { LocalStore = 0, SyncEngine = 1 };
  */
 class TargetIdGenerator {
  public:
+  // Makes Objective-C++ code happy to provide a default ctor.
+  TargetIdGenerator() = default;
+
   TargetIdGenerator(const TargetIdGenerator& value);
 
   /**