Port autoid to C++ and remove FSTUtil (#475)

* Port autoid to C++
* Reimplement FSTUtil on top of firestore::CreateAutoId directly
* Migrate FSTUtil callers to directly use firestore::CreateAutoId
* Remove FSTUtil

11 files changed, 157 insertions, 68 deletions

diff --git a/Firestore/CMakeLists.txt b/Firestore/CMakeLists.txt
index 4274056..119af5e 100644
--- a/Firestore/CMakeLists.txt
+++ b/Firestore/CMakeLists.txt
@@ -16,3 +16,6 @@ include(${PROJECT_SOURCE_DIR}/cmake/external/googletest.cmake)
 
 add_subdirectory(src/support)
 add_subdirectory(test/support)
+
+add_subdirectory(src/core/util)
+add_subdirectory(test/core/util)
diff --git a/Firestore/Example/Firestore.xcodeproj/project.pbxproj b/Firestore/Example/Firestore.xcodeproj/project.pbxproj
index 034a96e..f56af4c 100644
--- a/Firestore/Example/Firestore.xcodeproj/project.pbxproj
+++ b/Firestore/Example/Firestore.xcodeproj/project.pbxproj
@@ -25,6 +25,7 @@
 /* Begin PBXBuildFile section */
 		3B843E4C1F3A182900548890 /* remote_store_spec_test.json in Resources */ = {isa = PBXBuildFile; fileRef = 3B843E4A1F3930A400548890 /* remote_store_spec_test.json */; };
 		5463926E1FBEDE28005031AA /* secure_random_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = 5463926D1FBEDE28005031AA /* secure_random_test.cc */; };
+		5471DCF91FBF99AC00656CD3 /* autoid_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = 5471DCF71FBF99A300656CD3 /* autoid_test.cc */; };
 		54764FAB1FAA0C320085E60A /* string_util_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = 54764FAA1FAA0C320085E60A /* string_util_test.cc */; };
 		54764FAF1FAA21B90085E60A /* FSTGoogleTestTests.mm in Sources */ = {isa = PBXBuildFile; fileRef = 54764FAE1FAA21B90085E60A /* FSTGoogleTestTests.mm */; };
 		5491BC721FB44593008B3588 /* FSTIntegrationTestCase.mm in Sources */ = {isa = PBXBuildFile; fileRef = 5491BC711FB44593008B3588 /* FSTIntegrationTestCase.mm */; };
@@ -135,7 +136,6 @@
 		DE51B1FF1F0D493A0013853F /* FSTAssertTests.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B1861F0D48AC0013853F /* FSTAssertTests.m */; };
 		DE51B2001F0D493A0013853F /* FSTComparisonTests.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B1871F0D48AC0013853F /* FSTComparisonTests.m */; };
 		DE51B2011F0D493E0013853F /* FSTHelpers.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B1891F0D48AC0013853F /* FSTHelpers.m */; };
-		DE51B2021F0D493E0013853F /* FSTUtilTests.m in Sources */ = {isa = PBXBuildFile; fileRef = DE51B18A1F0D48AC0013853F /* FSTUtilTests.m */; };
 		F104BBD69BC3F0796E3A77C1 /* Pods_Firestore_Tests.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 69F6A10DBD6187489481CD76 /* Pods_Firestore_Tests.framework */; };
 /* End PBXBuildFile section */
 
@@ -185,6 +185,7 @@
 		42491D7DC8C8CD245CC22B93 /* Pods-SwiftBuildTest.debug.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-SwiftBuildTest.debug.xcconfig"; path = "Pods/Target Support Files/Pods-SwiftBuildTest/Pods-SwiftBuildTest.debug.xcconfig"; sourceTree = "<group>"; };
 		4EBC5F5ABE1FD097EFE5E224 /* Pods-Firestore_Example.release.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-Firestore_Example.release.xcconfig"; path = "Pods/Target Support Files/Pods-Firestore_Example/Pods-Firestore_Example.release.xcconfig"; sourceTree = "<group>"; };
 		5463926D1FBEDE28005031AA /* secure_random_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = secure_random_test.cc; path = ../../test/support/secure_random_test.cc; sourceTree = "<group>"; };
+		5471DCF71FBF99A300656CD3 /* autoid_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = autoid_test.cc; path = ../../test/core/util/autoid_test.cc; sourceTree = "<group>"; };
 		54764FAA1FAA0C320085E60A /* string_util_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = string_util_test.cc; path = ../../Port/string_util_test.cc; sourceTree = "<group>"; };
 		54764FAE1FAA21B90085E60A /* FSTGoogleTestTests.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; name = FSTGoogleTestTests.mm; path = GoogleTest/FSTGoogleTestTests.mm; sourceTree = "<group>"; };
 		5491BC711FB44593008B3588 /* FSTIntegrationTestCase.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = FSTIntegrationTestCase.mm; sourceTree = "<group>"; };
@@ -281,7 +282,6 @@
 		DE51B1871F0D48AC0013853F /* FSTComparisonTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTComparisonTests.m; sourceTree = "<group>"; };
 		DE51B1881F0D48AC0013853F /* FSTHelpers.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = FSTHelpers.h; sourceTree = "<group>"; };
 		DE51B1891F0D48AC0013853F /* FSTHelpers.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTHelpers.m; sourceTree = "<group>"; };
-		DE51B18A1F0D48AC0013853F /* FSTUtilTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTUtilTests.m; sourceTree = "<group>"; };
 		DE51B1941F0D48AC0013853F /* FSTLevelDBSpecTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTLevelDBSpecTests.m; sourceTree = "<group>"; };
 		DE51B1951F0D48AC0013853F /* FSTMemorySpecTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = FSTMemorySpecTests.m; sourceTree = "<group>"; };
 		DE51B1961F0D48AC0013853F /* FSTMockDatastore.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = FSTMockDatastore.h; sourceTree = "<group>"; };
@@ -374,9 +374,26 @@
 			name = support;
 			sourceTree = "<group>";
 		};
+		5471DCFA1FBF99B100656CD3 /* core */ = {
+			isa = PBXGroup;
+			children = (
+				5471DCFB1FBF99B800656CD3 /* util */,
+			);
+			name = core;
+			sourceTree = "<group>";
+		};
+		5471DCFB1FBF99B800656CD3 /* util */ = {
+			isa = PBXGroup;
+			children = (
+				5471DCF71FBF99A300656CD3 /* autoid_test.cc */,
+			);
+			name = util;
+			sourceTree = "<group>";
+		};
 		54764FAC1FAA0C390085E60A /* GoogleTests */ = {
 			isa = PBXGroup;
 			children = (
+				5471DCFA1FBF99B100656CD3 /* core */,
 				54764FAD1FAA0C650085E60A /* Port */,
 				5463926F1FBEDE2F005031AA /* support */,
 				54764FAE1FAA21B90085E60A /* FSTGoogleTestTests.mm */,
@@ -595,7 +612,6 @@
 				DE51B1871F0D48AC0013853F /* FSTComparisonTests.m */,
 				DE51B1881F0D48AC0013853F /* FSTHelpers.h */,
 				DE51B1891F0D48AC0013853F /* FSTHelpers.m */,
-				DE51B18A1F0D48AC0013853F /* FSTUtilTests.m */,
 				54E9282A1F339CAD00C1953E /* XCTestCase+Await.h */,
 				54E9282B1F339CAD00C1953E /* XCTestCase+Await.m */,
 				D5B259DAA9149B80D6245B57 /* FSTTestDispatchQueue.h */,
@@ -1163,11 +1179,11 @@
 				DE51B1E11F0D490D0013853F /* FSTMemoryRemoteDocumentCacheTests.m in Sources */,
 				DE51B1FF1F0D493A0013853F /* FSTAssertTests.m in Sources */,
 				DE51B1D31F0D48CD0013853F /* FSTViewSnapshotTest.m in Sources */,
-				DE51B2021F0D493E0013853F /* FSTUtilTests.m in Sources */,
 				DE51B1F91F0D491F0013853F /* FSTWatchChangeTests.m in Sources */,
 				DE51B1F81F0D491F0013853F /* FSTWatchChange+Testing.m in Sources */,
 				DE51B1EB1F0D490D0013853F /* FSTWriteGroupTests.mm in Sources */,
 				DE51B2011F0D493E0013853F /* FSTHelpers.m in Sources */,
+				5471DCF91FBF99AC00656CD3 /* autoid_test.cc in Sources */,
 				DE51B1F61F0D491B0013853F /* FSTSerializerBetaTests.m in Sources */,
 				DE51B1F01F0D49140013853F /* FSTFieldValueTests.m in Sources */,
 				5491BC721FB44593008B3588 /* FSTIntegrationTestCase.mm in Sources */,
diff --git a/Firestore/Example/Tests/Util/FSTIntegrationTestCase.mm b/Firestore/Example/Tests/Util/FSTIntegrationTestCase.mm
index 47d6e76..2c29bf0 100644
--- a/Firestore/Example/Tests/Util/FSTIntegrationTestCase.mm
+++ b/Firestore/Example/Tests/Util/FSTIntegrationTestCase.mm
@@ -21,12 +21,13 @@
 #import <GRPCClient/GRPCCall+ChannelArg.h>
 #import <GRPCClient/GRPCCall+Tests.h>
 
+#include "Firestore/src/core/util/autoid.h"
+
 #import "Firestore/Source/API/FIRFirestore+Internal.h"
 #import "Firestore/Source/Auth/FSTEmptyCredentialsProvider.h"
 #import "Firestore/Source/Local/FSTLevelDB.h"
 #import "Firestore/Source/Model/FSTDatabaseID.h"
 #import "Firestore/Source/Util/FSTDispatchQueue.h"
-#import "Firestore/Source/Util/FSTUtil.h"
 
 #import "Firestore/Example/Tests/Util/FSTEventAccumulator.h"
 #import "Firestore/Example/Tests/Util/FSTTestDispatchQueue.h"
@@ -164,7 +165,8 @@ NS_ASSUME_NONNULL_BEGIN
 }
 
 - (NSString *)documentPath {
-  return [@"test-collection/" stringByAppendingString:[FSTUtil autoID]];
+  std::string autoId = firestore::CreateAutoId();
+  return [NSString stringWithFormat:@"test-collection/%s", autoId.c_str()];
 }
 
 - (FIRDocumentReference *)documentRef {
@@ -172,7 +174,8 @@ NS_ASSUME_NONNULL_BEGIN
 }
 
 - (FIRCollectionReference *)collectionRef {
-  NSString *collectionName = [@"test-collection-" stringByAppendingString:[FSTUtil autoID]];
+  std::string autoId = firestore::CreateAutoId();
+  NSString *collectionName = [NSString stringWithFormat:@"test-collection-%s", autoId.c_str()];
   return [self.db collectionWithPath:collectionName];
 }
 
diff --git a/Firestore/Source/API/FIRCollectionReference.m b/Firestore/Source/API/FIRCollectionReference.mm
index f90bff5..7b487c6 100644
--- a/Firestore/Source/API/FIRCollectionReference.m
+++ b/Firestore/Source/API/FIRCollectionReference.mm
@@ -16,6 +16,8 @@
 
 #import "FIRCollectionReference.h"
 
+#include "Firestore/src/core/util/autoid.h"
+
 #import "Firestore/Source/API/FIRDocumentReference+Internal.h"
 #import "Firestore/Source/API/FIRQuery+Internal.h"
 #import "Firestore/Source/API/FIRQuery_Init.h"
@@ -24,7 +26,6 @@
 #import "Firestore/Source/Model/FSTPath.h"
 #import "Firestore/Source/Util/FSTAssert.h"
 #import "Firestore/Source/Util/FSTUsageValidation.h"
-#import "Firestore/Source/Util/FSTUtil.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -102,7 +103,7 @@ NS_ASSUME_NONNULL_BEGIN
 }
 
 - (FIRDocumentReference *)documentWithAutoID {
-  NSString *autoID = [FSTUtil autoID];
+  NSString *autoID = [NSString stringWithUTF8String:firestore::CreateAutoId().c_str()];
   FSTDocumentKey *key =
       [FSTDocumentKey keyWithPath:[self.query.path pathByAppendingSegment:autoID]];
   return [FIRDocumentReference referenceWithKey:key firestore:self.firestore];
diff --git a/Firestore/Source/Util/FSTUsageValidation.h b/Firestore/Source/Util/FSTUsageValidation.h
index a80dafa..34a3d64 100644
--- a/Firestore/Source/Util/FSTUsageValidation.h
+++ b/Firestore/Source/Util/FSTUsageValidation.h
@@ -18,6 +18,10 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+#if __cplusplus
+extern "C" {
+#endif
+
 /** Helper for creating a general exception for invalid usage of an API. */
 NSException *FSTInvalidUsage(NSString *exceptionName, NSString *format, ...);
 
@@ -42,4 +46,8 @@ NSException *FSTInvalidUsage(NSString *exceptionName, NSString *format, ...);
     @throw FSTInvalidUsage(@"FIRInvalidArgumentException", format, ##__VA_ARGS__); \
   } while (0)
 
+#if __cplusplus
+}  // extern "C"
+#endif
+
 NS_ASSUME_NONNULL_END
diff --git a/Firestore/Source/Util/FSTUtil.m b/Firestore/Source/Util/FSTUtil.m
deleted file mode 100644
index 47a8821..0000000
--- a/Firestore/Source/Util/FSTUtil.m
+++ /dev/null
@@ -1,38 +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/Util/FSTUtil.h"
-
-NS_ASSUME_NONNULL_BEGIN
-
-static const int kAutoIDLength = 20;
-static NSString *const kAutoIDAlphabet =
-    @"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
-
-@implementation FSTUtil
-
-+ (NSString *)autoID {
-  unichar autoID[kAutoIDLength];
-  for (int i = 0; i < kAutoIDLength; i++) {
-    uint32_t randIndex = arc4random_uniform((uint32_t)kAutoIDAlphabet.length);
-    autoID[i] = [kAutoIDAlphabet characterAtIndex:randIndex];
-  }
-  return [NSString stringWithCharacters:autoID length:kAutoIDLength];
-}
-
-@end
-
-NS_ASSUME_NONNULL_END
diff --git a/Firestore/src/core/util/CMakeLists.txt b/Firestore/src/core/util/CMakeLists.txt
new file mode 100644
index 0000000..6b08d8e
--- /dev/null
+++ b/Firestore/src/core/util/CMakeLists.txt
@@ -0,0 +1,22 @@
+# 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.
+
+add_library(
+  firestore_core_util
+  autoid.cc
+)
+target_link_libraries(
+  firestore_core_util
+  firestore_support
+)
diff --git a/Firestore/src/core/util/autoid.cc b/Firestore/src/core/util/autoid.cc
new file mode 100644
index 0000000..762bbcc
--- /dev/null
+++ b/Firestore/src/core/util/autoid.cc
@@ -0,0 +1,52 @@
+/*
+ * 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.
+ */
+
+#include "Firestore/src/core/util/autoid.h"
+
+#include <random>
+#include <string>
+
+#include "Firestore/src/support/secure_random.h"
+
+namespace {
+
+const int kAutoIdLength = 20;
+const char kAutoIdAlphabet[] =
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
+
+firestore::SecureRandom shared_random;
+
+}  // namespace
+
+namespace firestore {
+
+std::string CreateAutoId() {
+  std::string auto_id;
+  auto_id.reserve(kAutoIdLength);
+
+  // -2 here because:
+  //   * sizeof(kAutoIdAlphabet) includes the trailing null terminator
+  //   * uniform_int_distribution is inclusive on both sizes
+  std::uniform_int_distribution<int> letters(0, sizeof(kAutoIdAlphabet) - 2);
+
+  for (int i = 0; i < kAutoIdLength; i++) {
+    int rand_index = letters(shared_random);
+    auto_id.append(1, kAutoIdAlphabet[rand_index]);
+  }
+  return auto_id;
+}
+
+}  // namespace firestore
diff --git a/Firestore/Source/Util/FSTUtil.h b/Firestore/src/core/util/autoid.h
index 230c72a..13486af 100644
--- a/Firestore/Source/Util/FSTUtil.h
+++ b/Firestore/src/core/util/autoid.h
@@ -14,15 +14,16 @@
  * limitations under the License.
  */
 
-#import <Foundation/Foundation.h>
+#ifndef FIRESTORE_SRC_CORE_UTIL_AUTOID_H_
+#define FIRESTORE_SRC_CORE_UTIL_AUTOID_H_
 
-NS_ASSUME_NONNULL_BEGIN
+#include <string>
 
-@interface FSTUtil : NSObject
+namespace firestore {
 
-/** Generates a random ID suitable for use as a document ID. */
-+ (NSString *)autoID;
+// Generates a random ID suitable for use as a document ID.
+std::string CreateAutoId();
 
-@end
+}  // namespace firestore
 
-NS_ASSUME_NONNULL_END
+#endif  // FIRESTORE_SRC_CORE_UTIL_AUTOID_H_
diff --git a/Firestore/test/core/util/CMakeLists.txt b/Firestore/test/core/util/CMakeLists.txt
new file mode 100644
index 0000000..1989c0e
--- /dev/null
+++ b/Firestore/test/core/util/CMakeLists.txt
@@ -0,0 +1,22 @@
+# 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.
+
+cc_test(
+  firestore_core_util_test
+  autoid_test.cc
+)
+target_link_libraries(
+  firestore_core_util_test
+  firestore_core_util
+)
diff --git a/Firestore/Example/Tests/Util/FSTUtilTests.m b/Firestore/test/core/util/autoid_test.cc
index d59ed7a..c936194 100644
--- a/Firestore/Example/Tests/Util/FSTUtilTests.m
+++ b/Firestore/test/core/util/autoid_test.cc
@@ -14,22 +14,21 @@
  * limitations under the License.
  */
 
-#import "Firestore/Source/Util/FSTUtil.h"
+#include "Firestore/src/core/util/autoid.h"
 
-#import <XCTest/XCTest.h>
+#include <ctype.h>
 
-@interface FSTUtilTests : XCTestCase
-@end
+#include "gtest/gtest.h"
 
-@implementation FSTUtilTests
-
-- (void)testAutoID {
-  NSString *autoID = [FSTUtil autoID];
-  XCTAssertEqual([autoID length], 20);
-  for (NSUInteger i = 0; i < 20; i++) {
-    unichar c = [autoID characterAtIndex:i];
-    XCTAssert(c >= ' ' && c <= '~', @"Should be printable ascii characters.");
+TEST(AutoId, IsSane) {
+  for (int i = 0; i < 50; i++) {
+    std::string auto_id = firestore::CreateAutoId();
+    EXPECT_EQ(20, auto_id.length());
+    for (int pos = 0; pos < 20; pos++) {
+      char c = auto_id[pos];
+      EXPECT_TRUE(isalpha(c) || isdigit(c))
+          << "Should be printable ascii character: '" << c << "' in \"" << auto_id
+          << "\"";
+    }
   }
 }
-
-@end