port paths to FSTDocumentKey (#877)

* replace path with C++ implementation in FSTDocumentKey.{h,mm} only

* address changes

* address changes

3 files changed, 45 insertions, 27 deletions

diff --git a/Firestore/Source/Model/FSTDocument.mm b/Firestore/Source/Model/FSTDocument.mm
index bf416e7..58d3629 100644
--- a/Firestore/Source/Model/FSTDocument.mm
+++ b/Firestore/Source/Model/FSTDocument.mm
@@ -94,8 +94,8 @@ NS_ASSUME_NONNULL_BEGIN
 }
 
 - (NSString *)description {
-  return [NSString stringWithFormat:@"<FSTDocument: key:%@ version:%@ localMutations:%@ data:%@>",
-                                    self.key.path, self.version,
+  return [NSString stringWithFormat:@"<FSTDocument: key:%s version:%@ localMutations:%@ data:%@>",
+                                    self.key.path.CanonicalString().c_str(), self.version,
                                     self.localMutations ? @"YES" : @"NO", self.data];
 }
 
diff --git a/Firestore/Source/Model/FSTDocumentKey.h b/Firestore/Source/Model/FSTDocumentKey.h
index 2af1c9a..dbcff2c 100644
--- a/Firestore/Source/Model/FSTDocumentKey.h
+++ b/Firestore/Source/Model/FSTDocumentKey.h
@@ -16,7 +16,9 @@
 
 #import <Foundation/Foundation.h>
 
-@class FSTResourcePath;
+#include <initializer_list>
+
+#include "Firestore/core/src/firebase/firestore/model/resource_path.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -29,16 +31,14 @@ NS_ASSUME_NONNULL_BEGIN
  * @param path The path to the document.
  * @return A new instance of FSTDocumentKey.
  */
-+ (instancetype)keyWithPath:(FSTResourcePath *)path;
-
++ (instancetype)keyWithPath:(firebase::firestore::model::ResourcePath)path;
 /**
  * Creates and returns a new document key with a path with the given segments.
  *
  * @param segments The segments of the path to the document.
  * @return A new instance of FSTDocumentKey.
  */
-+ (instancetype)keyWithSegments:(NSArray<NSString *> *)segments;
-
++ (instancetype)keyWithSegments:(std::initializer_list<std::string>)segments;
 /**
  * Creates and returns a new document key from the given resource path string.
  *
@@ -48,13 +48,12 @@ NS_ASSUME_NONNULL_BEGIN
 + (instancetype)keyWithPathString:(NSString *)resourcePath;
 
 /** Returns true iff the given path is a path to a document. */
-+ (BOOL)isDocumentKey:(FSTResourcePath *)path;
-
++ (BOOL)isDocumentKey:(const firebase::firestore::model::ResourcePath &)path;
 - (BOOL)isEqualToKey:(FSTDocumentKey *)other;
 - (NSComparisonResult)compare:(FSTDocumentKey *)other;
 
 /** The path to the document. */
-@property(strong, nonatomic, readonly) FSTResourcePath *path;
+- (const firebase::firestore::model::ResourcePath &)path;
 
 @end
 
diff --git a/Firestore/Source/Model/FSTDocumentKey.mm b/Firestore/Source/Model/FSTDocumentKey.mm
index a382a55..269748f 100644
--- a/Firestore/Source/Model/FSTDocumentKey.mm
+++ b/Firestore/Source/Model/FSTDocumentKey.mm
@@ -16,35 +16,43 @@
 
 #import "Firestore/Source/Model/FSTDocumentKey.h"
 
+#include <utility>
+
 #import "Firestore/Source/Core/FSTFirestoreClient.h"
-#import "Firestore/Source/Model/FSTPath.h"
 #import "Firestore/Source/Util/FSTAssert.h"
 
+#include "Firestore/core/src/firebase/firestore/model/resource_path.h"
+#include "Firestore/core/src/firebase/firestore/util/string_apple.h"
+
+namespace util = firebase::firestore::util;
+using firebase::firestore::model::ResourcePath;
+
 NS_ASSUME_NONNULL_BEGIN
 
-@interface FSTDocumentKey ()
-/** The path to the document. */
-@property(strong, nonatomic, readwrite) FSTResourcePath *path;
+@interface FSTDocumentKey () {
+  /** The path to the document. */
+  ResourcePath _path;
+}
 @end
 
 @implementation FSTDocumentKey
 
-+ (instancetype)keyWithPath:(FSTResourcePath *)path {
-  return [[FSTDocumentKey alloc] initWithPath:path];
++ (instancetype)keyWithPath:(ResourcePath)path {
+  return [[FSTDocumentKey alloc] initWithPath:std::move(path)];
 }
 
-+ (instancetype)keyWithSegments:(NSArray<NSString *> *)segments {
-  return [FSTDocumentKey keyWithPath:[FSTResourcePath pathWithSegments:segments]];
++ (instancetype)keyWithSegments:(std::initializer_list<std::string>)segments {
+  return [FSTDocumentKey keyWithPath:ResourcePath(segments)];
 }
 
 + (instancetype)keyWithPathString:(NSString *)resourcePath {
-  NSArray<NSString *> *segments = [resourcePath componentsSeparatedByString:@"/"];
-  return [FSTDocumentKey keyWithSegments:segments];
+  return [FSTDocumentKey keyWithPath:ResourcePath::FromString(util::MakeStringView(resourcePath))];
 }
 
 /** Designated initializer. */
-- (instancetype)initWithPath:(FSTResourcePath *)path {
-  FSTAssert([FSTDocumentKey isDocumentKey:path], @"invalid document key path: %@", path);
+- (instancetype)initWithPath:(ResourcePath)path {
+  FSTAssert([FSTDocumentKey isDocumentKey:path], @"invalid document key path: %s",
+            path.CanonicalString().c_str());
 
   if (self = [super init]) {
     _path = path;
@@ -63,11 +71,11 @@ NS_ASSUME_NONNULL_BEGIN
 }
 
 - (NSUInteger)hash {
-  return self.path.hash;
+  return _path.Hash();
 }
 
 - (NSString *)description {
-  return [NSString stringWithFormat:@"<FSTDocumentKey: %@>", self.path];
+  return [NSString stringWithFormat:@"<FSTDocumentKey: %s>", _path.CanonicalString().c_str()];
 }
 
 /** Implements NSCopying without actually copying because FSTDocumentKeys are immutable. */
@@ -89,15 +97,26 @@ NS_ASSUME_NONNULL_BEGIN
   };
 }
 
-+ (BOOL)isDocumentKey:(FSTResourcePath *)path {
-  return path.length % 2 == 0;
++ (BOOL)isDocumentKey:(const ResourcePath &)path {
+  return path.size() % 2 == 0;
+}
+
+- (const firebase::firestore::model::ResourcePath &)path {
+  return _path;
 }
 
 @end
 
 const NSComparator FSTDocumentKeyComparator =
     ^NSComparisonResult(FSTDocumentKey *key1, FSTDocumentKey *key2) {
-      return [key1.path compare:key2.path];
+      if (key1.path < key2.path) {
+        return NSOrderedAscending;
+      } else if (key1.path > key2.path) {
+        return NSOrderedDescending;
+      } else {
+        return NSOrderedSame;
+      }
+
     };
 
 NSString *const kDocumentKeyPath = @"__name__";