Implement Firestore DatabaseInfo and port both Database{Id,Info} C++ to the iOS code (#738)

* implement Firestore DatabaseInfo in C++

* temporary stash changes; blocking on the massive renaming of .m to .mm

* add database_info_test to project

* finish port DatabaseId and fix style, modular fixing DatabaseInfo

* port DatabaseInfo

* remove FSTDatabase{ID,Info} and their tests from project

* fix unit test

* use namespace alias

* use namespace alias, leftover

* address more changes

* refactoring to use raw pointer instead of value for property

* address changes

* remove self->

* fix style

* remove the name suffix Alloc

* fix a bug

4 files changed, 22 insertions, 148 deletions

diff --git a/Firestore/Source/Model/FSTDatabaseID.h b/Firestore/Source/Model/FSTDatabaseID.h
deleted file mode 100644
index 442e764..0000000
--- a/Firestore/Source/Model/FSTDatabaseID.h
+++ /dev/null
@@ -1,48 +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>
-
-NS_ASSUME_NONNULL_BEGIN
-
-/** FSTDatabaseID represents a particular database in the datastore. */
-@interface FSTDatabaseID : NSObject
-
-/**
- * Creates and returns a new FSTDatabaseID.
- * @param projectID The project for the database.
- * @param databaseID The database in the project to use.
- * @return A new instance of FSTDatabaseID.
- */
-+ (instancetype)databaseIDWithProject:(NSString *)projectID database:(NSString *)databaseID;
-
-/** The project. */
-@property(nonatomic, copy, readonly) NSString *projectID;
-
-/** The database. */
-@property(nonatomic, copy, readonly) NSString *databaseID;
-
-/** Whether this is the default database of the project. */
-- (BOOL)isDefaultDatabase;
-
-- (NSComparisonResult)compare:(FSTDatabaseID *)other;
-- (BOOL)isEqualToDatabaseId:(FSTDatabaseID *)databaseID;
-
-@end
-
-extern NSString *const kDefaultDatabaseID;
-
-NS_ASSUME_NONNULL_END
diff --git a/Firestore/Source/Model/FSTDatabaseID.mm b/Firestore/Source/Model/FSTDatabaseID.mm
deleted file mode 100644
index bff5855..0000000
--- a/Firestore/Source/Model/FSTDatabaseID.mm
+++ /dev/null
@@ -1,90 +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/Model/FSTDatabaseID.h"
-
-#import "Firestore/Source/Util/FSTAssert.h"
-
-NS_ASSUME_NONNULL_BEGIN
-
-/** The default name for "unset" database ID in resource names. */
-NSString *const kDefaultDatabaseID = @"(default)";
-
-#pragma mark - FSTDatabaseID
-
-@implementation FSTDatabaseID
-
-+ (instancetype)databaseIDWithProject:(NSString *)projectID database:(NSString *)databaseID {
-  return [[FSTDatabaseID alloc] initWithProject:projectID database:databaseID];
-}
-
-/**
- * Designated initializer.
- *
- * @param projectID The project for the database.
- * @param databaseID The database in the datastore.
- */
-- (instancetype)initWithProject:(NSString *)projectID database:(NSString *)databaseID {
-  if (self = [super init]) {
-    FSTAssert(databaseID, @"databaseID cannot be nil");
-    _projectID = [projectID copy];
-    _databaseID = [databaseID copy];
-  }
-  return self;
-}
-
-- (BOOL)isEqual:(id)other {
-  if (other == self) return YES;
-  if (![[other class] isEqual:[self class]]) return NO;
-
-  return [self isEqualToDatabaseId:other];
-}
-
-- (NSUInteger)hash {
-  NSUInteger hash = [self.projectID hash];
-  hash = hash * 31u + [self.databaseID hash];
-  return hash;
-}
-
-- (NSString *)description {
-  return [NSString
-      stringWithFormat:@"<FSTDatabaseID: project:%@ database:%@>", self.projectID, self.databaseID];
-}
-
-- (NSComparisonResult)compare:(FSTDatabaseID *)other {
-  NSComparisonResult cmp = [self.projectID compare:other.projectID];
-  return cmp == NSOrderedSame ? [self.databaseID compare:other.databaseID] : cmp;
-}
-
-- (BOOL)isDefaultDatabase {
-  return [self.databaseID isEqualToString:kDefaultDatabaseID];
-}
-
-- (BOOL)isEqualToDatabaseId:(FSTDatabaseID *)databaseID {
-  if (self == databaseID) return YES;
-  if (databaseID == nil) return NO;
-  if (self.projectID != databaseID.projectID &&
-      ![self.projectID isEqualToString:databaseID.projectID])
-    return NO;
-  if (self.databaseID != databaseID.databaseID &&
-      ![self.databaseID isEqualToString:databaseID.databaseID])
-    return NO;
-  return YES;
-}
-
-@end
-
-NS_ASSUME_NONNULL_END
diff --git a/Firestore/Source/Model/FSTFieldValue.h b/Firestore/Source/Model/FSTFieldValue.h
index 93fd5c4..c8118c6 100644
--- a/Firestore/Source/Model/FSTFieldValue.h
+++ b/Firestore/Source/Model/FSTFieldValue.h
@@ -18,7 +18,8 @@
 
 #import "Firestore/third_party/Immutable/FSTImmutableSortedDictionary.h"
 
-@class FSTDatabaseID;
+#include "Firestore/core/src/firebase/firestore/model/database_id.h"
+
 @class FSTDocumentKey;
 @class FSTFieldPath;
 @class FSTTimestamp;
@@ -208,9 +209,11 @@ typedef NS_ENUM(NSInteger, FSTServerTimestampBehavior) {
  * A reference value stored in Firestore.
  */
 @interface FSTReferenceValue : FSTFieldValue <FSTDocumentKey *>
-+ (instancetype)referenceValue:(FSTDocumentKey *)value databaseID:(FSTDatabaseID *)databaseID;
++ (instancetype)referenceValue:(FSTDocumentKey *)value
+                    databaseID:(const firebase::firestore::model::DatabaseId *)databaseID;
 - (FSTDocumentKey *)valueWithOptions:(FSTFieldValueOptions *)options;
-@property(nonatomic, strong, readonly) FSTDatabaseID *databaseID;
+// Does not own this DatabaseId.
+@property(nonatomic, assign, readonly) const firebase::firestore::model::DatabaseId *databaseID;
 @end
 
 /**
diff --git a/Firestore/Source/Model/FSTFieldValue.mm b/Firestore/Source/Model/FSTFieldValue.mm
index 8ffc98e..3f3548c 100644
--- a/Firestore/Source/Model/FSTFieldValue.mm
+++ b/Firestore/Source/Model/FSTFieldValue.mm
@@ -22,12 +22,16 @@
 #import "Firestore/Source/API/FIRGeoPoint+Internal.h"
 #import "Firestore/Source/API/FIRSnapshotOptions+Internal.h"
 #import "Firestore/Source/Core/FSTTimestamp.h"
-#import "Firestore/Source/Model/FSTDatabaseID.h"
 #import "Firestore/Source/Model/FSTDocumentKey.h"
 #import "Firestore/Source/Model/FSTPath.h"
 #import "Firestore/Source/Util/FSTAssert.h"
 #import "Firestore/Source/Util/FSTClasses.h"
 
+#include "Firestore/core/src/firebase/firestore/model/database_id.h"
+#include "Firestore/core/src/firebase/firestore/util/string_apple.h"
+
+namespace util = firebase::firestore::util;
+using firebase::firestore::model::DatabaseId;
 using firebase::firestore::util::Comparator;
 using firebase::firestore::util::CompareMixedNumber;
 using firebase::firestore::util::DoubleBitwiseEquals;
@@ -650,11 +654,11 @@ static NSComparisonResult CompareBytes(NSData *left, NSData *right) {
 
 @implementation FSTReferenceValue
 
-+ (instancetype)referenceValue:(FSTDocumentKey *)value databaseID:(FSTDatabaseID *)databaseID {
++ (instancetype)referenceValue:(FSTDocumentKey *)value databaseID:(const DatabaseId *)databaseID {
   return [[FSTReferenceValue alloc] initWithValue:value databaseID:databaseID];
 }
 
-- (id)initWithValue:(FSTDocumentKey *)value databaseID:(FSTDatabaseID *)databaseID {
+- (id)initWithValue:(FSTDocumentKey *)value databaseID:(const DatabaseId *)databaseID {
   self = [super init];
   if (self) {
     _key = value;
@@ -680,12 +684,11 @@ static NSComparisonResult CompareBytes(NSData *left, NSData *right) {
   }
 
   FSTReferenceValue *otherRef = (FSTReferenceValue *)other;
-  return [self.key isEqualToKey:otherRef.key] &&
-         [self.databaseID isEqualToDatabaseId:otherRef.databaseID];
+  return [self.key isEqualToKey:otherRef.key] && *self.databaseID == *otherRef.databaseID;
 }
 
 - (NSUInteger)hash {
-  NSUInteger result = [self.databaseID hash];
+  NSUInteger result = self.databaseID->Hash();
   result = 31 * result + [self.key hash];
   return result;
 }
@@ -693,7 +696,13 @@ static NSComparisonResult CompareBytes(NSData *left, NSData *right) {
 - (NSComparisonResult)compare:(FSTFieldValue *)other {
   if ([other isKindOfClass:[FSTReferenceValue class]]) {
     FSTReferenceValue *ref = (FSTReferenceValue *)other;
-    NSComparisonResult cmp = [self.databaseID compare:ref.databaseID];
+    NSComparisonResult cmp = [util::WrapNSStringNoCopy(self.databaseID->project_id())
+        compare:util::WrapNSStringNoCopy(ref.databaseID->project_id())];
+    if (cmp != NSOrderedSame) {
+      return cmp;
+    }
+    cmp = [util::WrapNSStringNoCopy(self.databaseID->database_id())
+        compare:util::WrapNSStringNoCopy(ref.databaseID->database_id())];
     return cmp != NSOrderedSame ? cmp : [self.key compare:ref.key];
   } else {
     return [self defaultCompare:other];