Adds copy auth state API (#1018)

* Adds copy auth state API

* improvements

* Addresses comments

8 files changed, 104 insertions, 4 deletions

diff --git a/Firebase/Auth/Source/FIRAuth.m b/Firebase/Auth/Source/FIRAuth.m
index dc3154f..d4ced9c 100644
--- a/Firebase/Auth/Source/FIRAuth.m
+++ b/Firebase/Auth/Source/FIRAuth.m
@@ -1137,6 +1137,52 @@ static NSMutableDictionary *gKeychainServiceNameForAppName;
   });
 }
 
+- (void)updateCurrentUser:(FIRUser *)user completion:(nullable FIRUserUpdateCallback)completion {
+  dispatch_async(FIRAuthGlobalWorkQueue(), ^{
+    if (!user) {
+      if (completion) {
+        dispatch_async(dispatch_get_main_queue(), ^{
+          completion([FIRAuthErrorUtils nullUserErrorWithMessage:nil]);
+        });
+      }
+      return;
+    }
+    void (^updateUserBlock)(FIRUser *user) = ^(FIRUser *user) {
+      NSError *error;
+      [self updateCurrentUser:user byForce:YES savingToDisk:YES error:(&error)];
+      if (error) {
+        if (completion) {
+          dispatch_async(dispatch_get_main_queue(), ^{
+            completion(error);
+          });
+        }
+        return;
+      } if (completion) {
+        dispatch_async(dispatch_get_main_queue(), ^{
+          completion(nil);
+        });
+      }
+    };
+    if (![user.requestConfiguration.APIKey isEqualToString:self->_requestConfiguration.APIKey]) {
+      // If the API keys are different, then we need to confirm that the user belongs to the same
+      // project before proceeding.
+      user.requestConfiguration = self->_requestConfiguration;
+      [user reloadWithCompletion:^(NSError *_Nullable error) {
+        if (error) {
+          if (completion) {
+            dispatch_async(dispatch_get_main_queue(), ^{
+              completion(error);
+            });
+          }
+          return;
+        }
+        updateUserBlock(user);
+      }];
+    } else {
+      updateUserBlock(user);
+    }
+  });
+}
 
 - (BOOL)signOut:(NSError *_Nullable __autoreleasing *_Nullable)error {
   __block BOOL result = YES;
diff --git a/Firebase/Auth/Source/FIRAuthErrorUtils.h b/Firebase/Auth/Source/FIRAuthErrorUtils.h
index c3fad0d..5b8205f 100644
--- a/Firebase/Auth/Source/FIRAuthErrorUtils.h
+++ b/Firebase/Auth/Source/FIRAuthErrorUtils.h
@@ -481,6 +481,13 @@ NS_ASSUME_NONNULL_BEGIN
  */
 + (NSError *)URLResponseErrorWithCode:(NSString *)code message:(nullable NSString *)message;
 
+/** @fn nullUserErrorWithMessage:
+    @brief Constructs an @c NSError with the code and message provided.
+    @param message Error message from the backend, if any.
+    @return The nullable NSError instance associated with the given error message, if one is found.
+ */
++ (NSError *)nullUserErrorWithMessage:(nullable NSString *)message;
+
 /** @fn keychainErrorWithFunction:status:
     @brief Constructs an @c NSError with the @c FIRAuthErrorCodeKeychainError code.
     @param keychainFunction The keychain function which was invoked and yielded an unexpected
diff --git a/Firebase/Auth/Source/FIRAuthErrorUtils.m b/Firebase/Auth/Source/FIRAuthErrorUtils.m
index 3748048..f4dbb94 100644
--- a/Firebase/Auth/Source/FIRAuthErrorUtils.m
+++ b/Firebase/Auth/Source/FIRAuthErrorUtils.m
@@ -139,8 +139,9 @@ static NSString *const kFIRAuthErrorMessageNoSuchProvider = @"User was not linke
 /** @var kFIRAuthErrorMessageInvalidUserToken
     @brief Message for @c FIRAuthErrorCodeInvalidUserToken error code.
  */
-static NSString *const kFIRAuthErrorMessageInvalidUserToken = @"The user's credential is no longer "
-    "valid. The user must sign in again.";
+static NSString *const kFIRAuthErrorMessageInvalidUserToken = @"This user's credential isn't valid "
+    "for this project. This can happen if the user's token has been tampered with, or if the user "
+    "doesn’t belong to the project associated with the API key used in your request.";
 
 /** @var kFIRAuthErrorMessageNetworkError
     @brief Message for @c FIRAuthErrorCodeNetworkError error code.
@@ -400,6 +401,12 @@ static NSString *const kFIRAuthErrorMessageWebInternalError = @"An internal erro
 static NSString *const kFIRAuthErrorMessageAppVerificationUserInteractionFailure = @"The app "
   "verification process has failed, print and inspect the error details for more information";
 
+/** @var kFIRAuthErrorMessageNullUser
+    @brief Message for @c FIRAuthErrorCodeNullUser error code.
+ */
+static NSString *const kFIRAuthErrorMessageNullUser = @"A null user object was provided as the "
+    "argument for an operation which requires a non-null user object.";
+
 /** @var kFIRAuthErrorMessageInternalError
     @brief Message for @c FIRAuthErrorCodeInternalError error code.
  */
@@ -520,6 +527,8 @@ static NSString *FIRAuthErrorDescription(FIRAuthErrorCode code) {
       return kFIRAuthErrorMessageAppVerificationUserInteractionFailure;
     case FIRAuthErrorCodeWebNetworkRequestFailed:
       return kFIRAuthErrorMessageWebRequestFailed;
+    case FIRAuthErrorCodeNullUser:
+      return kFIRAuthErrorMessageNullUser;
     case FIRAuthErrorCodeWebInternalError:
       return kFIRAuthErrorMessageWebInternalError;
   }
@@ -639,6 +648,8 @@ static NSString *const FIRAuthErrorCodeString(FIRAuthErrorCode code) {
       return @"ERROR_APP_VERIFICATION_FAILED";
     case FIRAuthErrorCodeWebNetworkRequestFailed:
       return @"ERROR_WEB_NETWORK_REQUEST_FAILED";
+    case FIRAuthErrorCodeNullUser:
+      return @"ERROR_NULL_USER";
     case FIRAuthErrorCodeWebInternalError:
       return @"ERROR_WEB_INTERNAL_ERROR";
   }
@@ -981,6 +992,10 @@ static NSString *const FIRAuthErrorCodeString(FIRAuthErrorCode code) {
   return nil;
 }
 
++ (NSError *)nullUserErrorWithMessage:(nullable NSString *)message {
+  return [self errorWithCode:FIRAuthInternalErrorCodeNullUser message:message];
+}
+
 + (NSError *)keychainErrorWithFunction:(NSString *)keychainFunction status:(OSStatus)status {
   NSString *failureReason = [NSString stringWithFormat:@"%@ (%li)", keychainFunction, (long)status];
   return [self errorWithCode:FIRAuthInternalErrorCodeKeychainError userInfo:@{
diff --git a/Firebase/Auth/Source/FIRAuthInternalErrors.h b/Firebase/Auth/Source/FIRAuthInternalErrors.h
index d2905cc..fd08022 100644
--- a/Firebase/Auth/Source/FIRAuthInternalErrors.h
+++ b/Firebase/Auth/Source/FIRAuthInternalErrors.h
@@ -370,6 +370,12 @@ typedef NS_ENUM(NSInteger, FIRAuthInternalErrorCode) {
   FIRAuthInternalErrorCodeAppNotVerified =
       FIRAuthPublicErrorCodeFlag | FIRAuthErrorCodeAppNotVerified,
 
+  /** Indicates that a non-null user was expected as an argmument to the operation but a null
+        user was provided.
+   */
+  FIRAuthInternalErrorCodeNullUser =
+      FIRAuthPublicErrorCodeFlag | FIRAuthErrorCodeNullUser,
+
   /** @var FIRAuthInternalErrorCodeRPCRequestEncodingError
       @brief Indicates an error encoding the RPC request.
       @remarks This is typically due to some sort of unexpected input value.
diff --git a/Firebase/Auth/Source/FIRUser.m b/Firebase/Auth/Source/FIRUser.m
index fc7930f..1b10976 100644
--- a/Firebase/Auth/Source/FIRUser.m
+++ b/Firebase/Auth/Source/FIRUser.m
@@ -251,6 +251,7 @@ static void callInMainThreadWithAuthDataResultAndError(
                                                      refreshToken:refreshToken];
   FIRUser *user = [[self alloc] initWithTokenService:tokenService];
   user.auth = auth;
+  user.requestConfiguration = auth.requestConfiguration;
   [user internalGetTokenWithCallback:^(NSString *_Nullable accessToken, NSError *_Nullable error) {
     if (error) {
       callback(nil, error);
@@ -316,6 +317,8 @@ static void callInMainThreadWithAuthDataResultAndError(
       [aDecoder decodeObjectOfClass:[FIRSecureTokenService class] forKey:kTokenServiceCodingKey];
   FIRUserMetadata *metadata =
       [aDecoder decodeObjectOfClass:[FIRUserMetadata class] forKey:kMetadataCodingKey];
+  NSString *APIKey =
+      [aDecoder decodeObjectOfClass:[FIRUserMetadata class] forKey:kAPIKeyCodingKey];
   if (!userID || !tokenService) {
     return nil;
   }
@@ -334,6 +337,7 @@ static void callInMainThreadWithAuthDataResultAndError(
     _providerData = providerData;
     _phoneNumber = phoneNumber;
     _metadata = metadata ?: [[FIRUserMetadata alloc] initWithCreationDate:nil lastSignInDate:nil];
+    _requestConfiguration = [[FIRAuthRequestConfiguration alloc] initWithAPIKey:APIKey];
   }
   return self;
 }
@@ -349,8 +353,6 @@ static void callInMainThreadWithAuthDataResultAndError(
   [aCoder encodeObject:_photoURL forKey:kPhotoURLCodingKey];
   [aCoder encodeObject:_displayName forKey:kDisplayNameCodingKey];
   [aCoder encodeObject:_metadata forKey:kMetadataCodingKey];
-  // The API key is encoded even it is not used in decoding to be compatible with previous versions
-  // of the library.
   [aCoder encodeObject:_auth.requestConfiguration.APIKey forKey:kAPIKeyCodingKey];
   [aCoder encodeObject:_tokenService forKey:kTokenServiceCodingKey];
 }
diff --git a/Firebase/Auth/Source/FIRUser_Internal.h b/Firebase/Auth/Source/FIRUser_Internal.h
index 9a069bb..4f89c00 100644
--- a/Firebase/Auth/Source/FIRUser_Internal.h
+++ b/Firebase/Auth/Source/FIRUser_Internal.h
@@ -17,6 +17,7 @@
 #import "FIRUser.h"
 
 @class FIRAuth;
+@class FIRAuthRequestConfiguration;
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -42,6 +43,11 @@ typedef void(^FIRRetrieveUserCallback)(FIRUser *_Nullable user, NSError *_Nullab
  */
 @property(nonatomic, weak) FIRAuth *auth;
 
+/** @property auth
+    @brief A strong reference to a requestConfiguration instance associated with this user instance.
+ */
+@property(nonatomic, strong) FIRAuthRequestConfiguration *requestConfiguration;
+
 /** @var accessTokenExpirationDate
     @brief The expiration date of the cached access token.
  */
diff --git a/Firebase/Auth/Source/Public/FIRAuth.h b/Firebase/Auth/Source/Public/FIRAuth.h
index aefba57..7d5ea42 100644
--- a/Firebase/Auth/Source/Public/FIRAuth.h
+++ b/Firebase/Auth/Source/Public/FIRAuth.h
@@ -32,6 +32,11 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+/** @typedef FIRUserUpdateCallback
+    @brief The type of block invoked when a request to update a current user is completed.
+ */
+typedef void (^FIRUserUpdateCallback)(NSError *_Nullable error) NS_SWIFT_NAME(UserUpdateCallback);
+
 /** @typedef FIRAuthStateDidChangeListenerHandle
     @brief The type of handle returned by `FIRAuth.addAuthStateDidChangeListener:`.
  */
@@ -297,6 +302,14 @@ NS_SWIFT_NAME(Auth)
  */
 - (instancetype)init NS_UNAVAILABLE;
 
+/** @fn updateCurrentUser:completion:
+    @brief Sets the currentUser on the calling Auth instance to the provided user object.
+    @param  user The user object to be set as the current user of the calling Auth instance.
+    @param completion Optionally; a block invoked after the user of the calling Auth instance has
+        been updated or an error was encountered.
+ */
+- (void)updateCurrentUser:(FIRUser *)user completion:(nullable FIRUserUpdateCallback)completion;
+
 /** @fn fetchProvidersForEmail:completion:
     @brief Fetches the list of IdPs that can be used for signing in with the provided email address.
         Useful for an "identifier-first" sign-in flow.
diff --git a/Firebase/Auth/Source/Public/FIRAuthErrors.h b/Firebase/Auth/Source/Public/FIRAuthErrors.h
index b8e5fb6..4a1a6f1 100644
--- a/Firebase/Auth/Source/Public/FIRAuthErrors.h
+++ b/Firebase/Auth/Source/Public/FIRAuthErrors.h
@@ -299,6 +299,11 @@ typedef NS_ENUM(NSInteger, FIRAuthErrorCode) {
      */
     FIRAuthErrorCodeWebInternalError = 17062,
 
+    /** Indicates that a non-null user was expected as an argmument to the operation but a null
+        user was provided.
+     */
+    FIRAuthErrorCodeNullUser = 17067,
+
     /** Indicates an error occurred while attempting to access the keychain.
      */
     FIRAuthErrorCodeKeychainError = 17995,