firebase-ios-sdk/FirebaseAuth/Sources/Backend/FIRAuthBackend.m

/*
 * 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 "FirebaseAuth/Sources/Backend/FIRAuthBackend.h"

#if SWIFT_PACKAGE
@import GTMSessionFetcherCore;
#else
#import <GTMSessionFetcher/GTMSessionFetcher.h>
#import <GTMSessionFetcher/GTMSessionFetcherService.h>
#endif

#import <FirebaseAppCheckInterop/FirebaseAppCheckInterop.h>

#import "FirebaseAuth/Sources/Public/FirebaseAuth/FirebaseAuth.h"

#import "FirebaseAuth/Sources/Auth/FIRAuthGlobalWorkQueue.h"
#import "FirebaseAuth/Sources/Auth/FIRAuth_Internal.h"
#import "FirebaseAuth/Sources/AuthProvider/OAuth/FIROAuthCredential_Internal.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRCreateAuthURIRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRCreateAuthURIResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRDeleteAccountRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRDeleteAccountResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIREmailLinkSignInRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIREmailLinkSignInResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRGetAccountInfoRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRGetAccountInfoResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRGetOOBConfirmationCodeRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRGetOOBConfirmationCodeResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRGetProjectConfigRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRGetProjectConfigResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRGetRecaptchaConfigRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRGetRecaptchaConfigResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRResetPasswordRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRResetPasswordResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRRevokeTokenRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRRevokeTokenResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRSecureTokenRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRSecureTokenResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRSendVerificationCodeRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRSendVerificationCodeResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRSetAccountInfoRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRSetAccountInfoResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRSignInWithGameCenterRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRSignInWithGameCenterResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRSignUpNewUserRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRSignUpNewUserResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRVerifyAssertionRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRVerifyAssertionResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRVerifyClientRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRVerifyClientResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRVerifyCustomTokenRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRVerifyCustomTokenResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRVerifyPasswordRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRVerifyPasswordResponse.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRVerifyPhoneNumberRequest.h"
#import "FirebaseAuth/Sources/Backend/RPC/FIRVerifyPhoneNumberResponse.h"
#import "FirebaseAuth/Sources/Utilities/FIRAuthErrorUtils.h"
#import "FirebaseCore/Extension/FirebaseCoreInternal.h"

#if TARGET_OS_IOS
#import "FirebaseAuth/Sources/Public/FirebaseAuth/FIRPhoneAuthProvider.h"

#import "FirebaseAuth/Sources/AuthProvider/Phone/FIRPhoneAuthCredential_Internal.h"
#import "FirebaseAuth/Sources/MultiFactor/Phone/FIRPhoneMultiFactorInfo+Internal.h"
#import "FirebaseAuth/Sources/MultiFactor/TOTP/FIRTOTPMultiFactorInfo.h"

#endif

NS_ASSUME_NONNULL_BEGIN

/** @var kClientVersionHeader
    @brief HTTP header name for the client version.
 */
static NSString *const kClientVersionHeader = @"X-Client-Version";

/** @var kIosBundleIdentifierHeader
    @brief HTTP header name for iOS bundle ID.
 */
static NSString *const kIosBundleIdentifierHeader = @"X-Ios-Bundle-Identifier";

/** @var kFirebaseLocalHeader
    @brief HTTP header name for the firebase locale.
 */
static NSString *const kFirebaseLocalHeader = @"X-Firebase-Locale";

/** @var kFirebaseAppIDHeader
    @brief HTTP header name for the Firebase app ID.
 */
static NSString *const kFirebaseAppIDHeader = @"X-Firebase-GMPID";

/** @var kFirebaseHeartbeatHeader
    @brief HTTP header name for a Firebase heartbeats payload.
 */
static NSString *const kFirebaseHeartbeatHeader = @"X-Firebase-Client";

/** @var kFirebaseAuthCoreFrameworkMarker
    @brief The marker in the HTTP header that indicates the request comes from Firebase Auth Core.
 */
static NSString *const kFirebaseAuthCoreFrameworkMarker = @"FirebaseCore-iOS";

/** @var kJSONContentType
    @brief The value of the HTTP content-type header for JSON payloads.
 */
static NSString *const kJSONContentType = @"application/json";

/** @var kErrorDataKey
    @brief Key for error data in NSError returned by @c GTMSessionFetcher.
 */
static NSString *const kErrorDataKey = @"data";

/** @var kErrorKey
    @brief The key for the "error" value in JSON responses from the server.
 */
static NSString *const kErrorKey = @"error";

/** @var kErrorsKey
    @brief The key for the "errors" value in JSON responses from the server.
 */
static NSString *const kErrorsKey = @"errors";

/** @var kReasonKey
    @brief The key for the "reason" value in JSON responses from the server.
 */
static NSString *const kReasonKey = @"reason";

/** @var kInvalidKeyReasonValue
    @brief The value for the "reason" key indicating an invalid API Key was received by the server.
 */
static NSString *const kInvalidKeyReasonValue = @"keyInvalid";

/** @var kAppNotAuthorizedReasonValue
    @brief The value for the "reason" key indicating the App is not authorized to use Firebase
        Authentication.
 */
static NSString *const kAppNotAuthorizedReasonValue = @"ipRefererBlocked";

/** @var kErrorMessageKey
    @brief The key for an error's "message" value in JSON responses from the server.
 */
static NSString *const kErrorMessageKey = @"message";

/** @var kReturnIDPCredentialErrorMessageKey
    @brief The key for "errorMessage" value in JSON responses from the server, In case
        returnIDPCredential of a verifyAssertion request is set to @YES.
 */
static NSString *const kReturnIDPCredentialErrorMessageKey = @"errorMessage";

/** @var kUserNotFoundErrorMessage
    @brief This is the error message returned when the user is not found, which means the user
        account has been deleted given the token was once valid.
 */
static NSString *const kUserNotFoundErrorMessage = @"USER_NOT_FOUND";

/** @var kUserDeletedErrorMessage
    @brief This is the error message the server will respond with if the user entered an invalid
        email address.
 */
static NSString *const kUserDeletedErrorMessage = @"EMAIL_NOT_FOUND";

/** @var kInvalidLocalIDErrorMessage
    @brief This is the error message the server responds with if the user local id in the id token
        does not exit.
 */
static NSString *const kInvalidLocalIDErrorMessage = @"INVALID_LOCAL_ID";

/** @var kUserTokenExpiredErrorMessage
    @brief The error returned by the server if the token issue time is older than the account's
        valid_since time.
 */
static NSString *const kUserTokenExpiredErrorMessage = @"TOKEN_EXPIRED";

/** @var kTooManyRequestsErrorMessage
    @brief This is the error message the server will respond with if too many requests were made to
        a server method.
 */
static NSString *const kTooManyRequestsErrorMessage = @"TOO_MANY_ATTEMPTS_TRY_LATER";

/** @var kInvalidCustomTokenErrorMessage
    @brief This is the error message the server will respond with if there is a validation error
        with the custom token.
 */
static NSString *const kInvalidCustomTokenErrorMessage = @"INVALID_CUSTOM_TOKEN";

/** @var kCustomTokenMismatch
    @brief This is the error message the server will respond with if the service account and API key
        belong to different projects.
 */
static NSString *const kCustomTokenMismatch = @"CREDENTIAL_MISMATCH";

/** @var kInvalidCredentialErrorMessage
    @brief This is the error message the server responds with if the IDP token or requestUri is
        invalid.
 */
static NSString *const kInvalidCredentialErrorMessage = @"INVALID_IDP_RESPONSE";

/** @var kUserDisabledErrorMessage
    @brief The error returned by the server if the user account is diabled.
 */
static NSString *const kUserDisabledErrorMessage = @"USER_DISABLED";

/** @var kOperationNotAllowedErrorMessage
    @brief This is the error message the server will respond with if Admin disables IDP specified by
        provider.
 */
static NSString *const kOperationNotAllowedErrorMessage = @"OPERATION_NOT_ALLOWED";

/** @var kPasswordLoginDisabledErrorMessage
    @brief This is the error message the server responds with if password login is disabled.
 */
static NSString *const kPasswordLoginDisabledErrorMessage = @"PASSWORD_LOGIN_DISABLED";

/** @var kEmailAlreadyInUseErrorMessage
    @brief This is the error message the server responds with if the email address already exists.
 */
static NSString *const kEmailAlreadyInUseErrorMessage = @"EMAIL_EXISTS";

/** @var kInvalidEmailErrorMessage
    @brief The error returned by the server if the email is invalid.
 */
static NSString *const kInvalidEmailErrorMessage = @"INVALID_EMAIL";

/** @var kInvalidIdentifierErrorMessage
    @brief The error returned by the server if the identifier is invalid.
 */
static NSString *const kInvalidIdentifierErrorMessage = @"INVALID_IDENTIFIER";

/** @var kWrongPasswordErrorMessage
    @brief This is the error message the server will respond with if the user entered a wrong
        password.
 */
static NSString *const kWrongPasswordErrorMessage = @"INVALID_PASSWORD";

/** @var kCredentialTooOldErrorMessage
    @brief This is the error message the server responds with if account change is attempted 5
        minutes after signing in.
 */
static NSString *const kCredentialTooOldErrorMessage = @"CREDENTIAL_TOO_OLD_LOGIN_AGAIN";

/** @var kFederatedUserIDAlreadyLinkedMessage
    @brief This is the error message the server will respond with if the federated user ID has been
        already linked with another account.
 */
static NSString *const kFederatedUserIDAlreadyLinkedMessage = @"FEDERATED_USER_ID_ALREADY_LINKED";

/** @var kInvalidUserTokenErrorMessage
    @brief This is the error message the server responds with if user's saved auth credential is
        invalid, and the user needs to sign in again.
 */
static NSString *const kInvalidUserTokenErrorMessage = @"INVALID_ID_TOKEN";

/** @var kWeakPasswordErrorMessagePrefix
    @brief This is the prefix for the error message the server responds with if user's new password
        to be set is too weak.
 */
static NSString *const kWeakPasswordErrorMessagePrefix = @"WEAK_PASSWORD";

/** @var kExpiredActionCodeErrorMessage
    @brief This is the error message the server will respond with if the action code is expired.
 */
static NSString *const kExpiredActionCodeErrorMessage = @"EXPIRED_OOB_CODE";

/** @var kInvalidActionCodeErrorMessage
    @brief This is the error message the server will respond with if the action code is invalid.
 */
static NSString *const kInvalidActionCodeErrorMessage = @"INVALID_OOB_CODE";

/** @var kMissingEmailErrorMessage
    @brief This is the error message the server will respond with if the email address is missing
        during a "send password reset email" attempt.
 */
static NSString *const kMissingEmailErrorMessage = @"MISSING_EMAIL";

/** @var kInvalidSenderEmailErrorMessage
    @brief This is the error message the server will respond with if the sender email is invalid
        during a "send password reset email" attempt.
 */
static NSString *const kInvalidSenderEmailErrorMessage = @"INVALID_SENDER";

/** @var kInvalidMessagePayloadErrorMessage
    @brief This is the error message the server will respond with if there are invalid parameters in
        the payload during a "send password reset email" attempt.
 */
static NSString *const kInvalidMessagePayloadErrorMessage = @"INVALID_MESSAGE_PAYLOAD";

/** @var kInvalidRecipientEmailErrorMessage
    @brief This is the error message the server will respond with if the recipient email is invalid.
 */
static NSString *const kInvalidRecipientEmailErrorMessage = @"INVALID_RECIPIENT_EMAIL";

/** @var kMissingIosBundleIDErrorMessage
    @brief This is the error message the server will respond with if iOS bundle ID is missing but
        the iOS App store ID is provided.
 */
static NSString *const kMissingIosBundleIDErrorMessage = @"MISSING_IOS_BUNDLE_ID";

/** @var kMissingAndroidPackageNameErrorMessage
    @brief This is the error message the server will respond with if Android Package Name is missing
        but the flag indicating the app should be installed is set to true.
 */
static NSString *const kMissingAndroidPackageNameErrorMessage = @"MISSING_ANDROID_PACKAGE_NAME";

/** @var kUnauthorizedDomainErrorMessage
    @brief This is the error message the server will respond with if the domain of the continue URL
        specified is not allowlisted in the Firebase console.
 */
static NSString *const kUnauthorizedDomainErrorMessage = @"UNAUTHORIZED_DOMAIN";

/** @var kInvalidProviderIDErrorMessage
    @brief This is the error message the server will respond with if the provider id given for the
        web operation is invalid.
 */
static NSString *const kInvalidProviderIDErrorMessage = @"INVALID_PROVIDER_ID";

/** @var kInvalidDynamicLinkDomainErrorMessage
    @brief This is the error message the server will respond with if the dynamic link domain
        provided in the request is invalid.
 */
static NSString *const kInvalidDynamicLinkDomainErrorMessage = @"INVALID_DYNAMIC_LINK_DOMAIN";

/** @var kInvalidContinueURIErrorMessage
    @brief This is the error message the server will respond with if the continue URL provided in
        the request is invalid.
 */
static NSString *const kInvalidContinueURIErrorMessage = @"INVALID_CONTINUE_URI";

/** @var kMissingContinueURIErrorMessage
    @brief This is the error message the server will respond with if there was no continue URI
        present in a request that required one.
 */
static NSString *const kMissingContinueURIErrorMessage = @"MISSING_CONTINUE_URI";

/** @var kInvalidPhoneNumberErrorMessage
    @brief This is the error message the server will respond with if an incorrectly formatted phone
        number is provided.
 */
static NSString *const kInvalidPhoneNumberErrorMessage = @"INVALID_PHONE_NUMBER";

/** @var kInvalidVerificationCodeErrorMessage
    @brief This is the error message the server will respond with if an invalid verification code is
        provided.
 */
static NSString *const kInvalidVerificationCodeErrorMessage = @"INVALID_CODE";

/** @var kInvalidSessionInfoErrorMessage
    @brief This is the error message the server will respond with if an invalid session info
        (verification ID) is provided.
 */
static NSString *const kInvalidSessionInfoErrorMessage = @"INVALID_SESSION_INFO";

/** @var kSessionExpiredErrorMessage
    @brief This is the error message the server will respond with if the SMS code has expired before
        it is used.
 */
static NSString *const kSessionExpiredErrorMessage = @"SESSION_EXPIRED";

/** @var kMissingOrInvalidNonceErrorMessage
    @brief This is the error message the server will respond with if the nonce is missing or
   invalid.
 */
static NSString *const kMissingOrInvalidNonceErrorMessage = @"MISSING_OR_INVALID_NONCE";

/** @var kMissingAppTokenErrorMessage
    @brief This is the error message the server will respond with if the APNS token is missing in a
        verifyClient request.
 */
static NSString *const kMissingAppTokenErrorMessage = @"MISSING_IOS_APP_TOKEN";

/** @var kMissingAppCredentialErrorMessage
    @brief This is the error message the server will respond with if the app token is missing in a
        sendVerificationCode request.
 */
static NSString *const kMissingAppCredentialErrorMessage = @"MISSING_APP_CREDENTIAL";

/** @var kInvalidAppCredentialErrorMessage
    @brief This is the error message the server will respond with if the app credential in a
        sendVerificationCode request is invalid.
 */
static NSString *const kInvalidAppCredentialErrorMessage = @"INVALID_APP_CREDENTIAL";

/** @var kQuoutaExceededErrorMessage
    @brief This is the error message the server will respond with if the quota for SMS text messages
        has been exceeded for the project.
 */
static NSString *const kQuoutaExceededErrorMessage = @"QUOTA_EXCEEDED";

/** @var kAppNotVerifiedErrorMessage
    @brief This is the error message the server will respond with if Firebase could not verify the
        app during a phone authentication flow.
 */
static NSString *const kAppNotVerifiedErrorMessage = @"APP_NOT_VERIFIED";

/** @var kCaptchaCheckFailedErrorMessage
    @brief This is the error message the server will respond with if the reCAPTCHA token provided is
        invalid.
 */
static NSString *const kCaptchaCheckFailedErrorMessage = @"CAPTCHA_CHECK_FAILED";

/** @var kTenantIDMismatch
    @brief This is the error message the server will respond with if the tenant id mismatches.
 */
static NSString *const kTenantIDMismatch = @"TENANT_ID_MISMATCH";

/** @var kUnsupportedTenantOperation
    @brief This is the error message the server will respond with if the operation does not support
   multi-tenant.
 */
static NSString *const kUnsupportedTenantOperation = @"UNSUPPORTED_TENANT_OPERATION";

/** @var kMissingMFAPendingCredentialErrorMessage
 @brief This is the error message the server will respond with if the MFA pending credential is
 missing.
 */
static NSString *const kMissingMFAPendingCredentialErrorMessage = @"MISSING_MFA_PENDING_CREDENTIAL";

/** @var kMissingMFAEnrollmentIDErrorMessage
 @brief This is the error message the server will respond with if the MFA enrollment ID is missing.
 */
static NSString *const kMissingMFAEnrollmentIDErrorMessage = @"MISSING_MFA_ENROLLMENT_ID";

/** @var kInvalidMFAPendingCredentialErrorMessage
 @brief This is the error message the server will respond with if the MFA pending credential is
 invalid.
 */
static NSString *const kInvalidMFAPendingCredentialErrorMessage = @"INVALID_MFA_PENDING_CREDENTIAL";

/** @var kMFAEnrollmentNotFoundErrorMessage
 @brief This is the error message the server will respond with if the MFA enrollment info is not
 found.
 */
static NSString *const kMFAEnrollmentNotFoundErrorMessage = @"MFA_ENROLLMENT_NOT_FOUND";

/** @var kAdminOnlyOperationErrorMessage
 @brief This is the error message the server will respond with if the operation is admin only.
 */
static NSString *const kAdminOnlyOperationErrorMessage = @"ADMIN_ONLY_OPERATION";

/** @var kUnverifiedEmailErrorMessage
 @brief This is the error message the server will respond with if the email is unverified.
 */
static NSString *const kUnverifiedEmailErrorMessage = @"UNVERIFIED_EMAIL";

/** @var kSecondFactorExistsErrorMessage
 @brief This is the error message the server will respond with if the second factor already exsists.
 */
static NSString *const kSecondFactorExistsErrorMessage = @"SECOND_FACTOR_EXISTS";

/** @var kSecondFactorLimitExceededErrorMessage
 @brief This is the error message the server will respond with if the number of second factor
 reaches the limit.
 */
static NSString *const kSecondFactorLimitExceededErrorMessage = @"SECOND_FACTOR_LIMIT_EXCEEDED";

/** @var kUnsupportedFirstFactorErrorMessage
 @brief This is the error message the server will respond with if the first factor doesn't support
 MFA.
 */
static NSString *const kUnsupportedFirstFactorErrorMessage = @"UNSUPPORTED_FIRST_FACTOR";

/** @var kBlockingCloudFunctionErrorResponse
 @brief This is the error message blocking Cloud Functions.
 */
static NSString *const kBlockingCloudFunctionErrorResponse = @"BLOCKING_FUNCTION_ERROR_RESPONSE";

/** @var kEmailChangeNeedsVerificationErrorMessage
 @brief This is the error message the server will respond with if changing an unverified email.
 */
static NSString *const kEmailChangeNeedsVerificationErrorMessage =
    @"EMAIL_CHANGE_NEEDS_VERIFICATION";

/** @var kInvalidPendingToken
    @brief Generic IDP error codes.
 */
static NSString *const kInvalidPendingToken = @"INVALID_PENDING_TOKEN";

/** @var kInvalidRecaptchaScore
    @brief This is the error message the server will respond with if the recaptcha score is invalid.
 */
static NSString *const kInvalidRecaptchaScore = @"INVALID_RECAPTCHA_SCORE";

/** @var kMissingRecaptchaToken
    @brief This is the error message the server will respond with if the recaptcha token is missing
   in the request.
 */
static NSString *const kMissingRecaptchaToken = @"MISSING_RECAPTCHA_TOKEN";

/** @var kInvalidRecaptchaToken
    @brief This is the error message the server will respond with if the recaptcha token is invalid.
 */
static NSString *const kInvalidRecaptchaToken = @"INVALID_RECAPTCHA_TOKEN";

/** @var kInvalidRecaptchaAction
    @brief This is the error message the server will respond with if the recaptcha action is
   invalid.
 */
static NSString *const kInvalidRecaptchaAction = @"INVALID_RECAPTCHA_ACTION";

/** @var kInvalidRecaptchaEnforcementState
    @brief This is the error message the server will respond with if the recaptcha enforcement state
   is invalid.
 */
static NSString *const kInvalidRecaptchaEnforcementState = @"INVALID_RECAPTCHA_ENFORCEMENT_STATE";

/** @var kRecaptchaNotEnabled
    @brief This is the error message the server will respond with if recaptcha is not enabled.
 */
static NSString *const kRecaptchaNotEnabled = @"RECAPTCHA_NOT_ENABLED";

/** @var kMissingClientIdentifier
    @brief This is the error message the server will respond with if Firebase could not verify the
        app during a phone authentication flow when a real phone number is used and app verification
        is disabled for testing.
 */
static NSString *const kMissingClientIdentifier = @"MISSING_CLIENT_IDENTIFIER";

/** @var kMissingClientType
    @brief This is the error message the server will respond with if Firebase could not verify the
        app during a phone authentication flow when a real phone number is used and app verification
        is disabled for testing.
 */
static NSString *const kMissingClientType = @"MISSING_CLIENT_TYPE";

/** @var kMissingRecaptchaToken
    @brief This is the error message the server will respond with if the recaptcha token is missing
   in the request.
 */
static NSString *const kMissingRecaptchaVersion = @"MISSING_RECAPTCHA_VERSION";

/** @var kMissingRecaptchaToken
    @brief This is the error message the server will respond with if the recaptcha token is missing
   in the request.
 */
static NSString *const kMissingInvalidReqType = @"INVALID_REQ_TYPE";

/** @var kMissingRecaptchaToken
    @brief This is the error message the server will respond with if the recaptcha token is missing
   in the request.
 */
static NSString *const kInvalidRecaptchaVersion = @"INVALID_RECAPTCHA_VERSION";

/** @var kInvalidLoginCredentials
    @brief This is the error message the server will respond with if the login credentials is
   invalid. in the request.
 */
static NSString *const kInvalidLoginCredentials = @"INVALID_LOGIN_CREDENTIALS";

/** @var gBackendImplementation
    @brief The singleton FIRAuthBackendImplementation instance to use.
 */
static id<FIRAuthBackendImplementation> gBackendImplementation;

/** @class FIRAuthBackendRPCImplementation
    @brief The default RPC-based backend implementation.
 */
@interface FIRAuthBackendRPCImplementation : NSObject <FIRAuthBackendImplementation>

/** @property RPCIssuer
    @brief An instance of FIRAuthBackendRPCIssuer for making RPC requests. Allows the RPC
        requests/responses to be easily faked.
 */
@property(nonatomic, strong) id<FIRAuthBackendRPCIssuer> RPCIssuer;

@end

@implementation FIRAuthBackend

+ (id<FIRAuthBackendImplementation>)implementation {
  if (!gBackendImplementation) {
    gBackendImplementation = [[FIRAuthBackendRPCImplementation alloc] init];
  }
  return gBackendImplementation;
}

+ (void)setBackendImplementation:(id<FIRAuthBackendImplementation>)backendImplementation {
  gBackendImplementation = backendImplementation;
}

+ (void)setDefaultBackendImplementationWithRPCIssuer:
    (nullable id<FIRAuthBackendRPCIssuer>)RPCIssuer {
  FIRAuthBackendRPCImplementation *defaultImplementation =
      [[FIRAuthBackendRPCImplementation alloc] init];
  if (RPCIssuer) {
    defaultImplementation.RPCIssuer = RPCIssuer;
  }
  gBackendImplementation = defaultImplementation;
}

+ (void)createAuthURI:(FIRCreateAuthURIRequest *)request
             callback:(FIRCreateAuthURIResponseCallback)callback {
  [[self implementation] createAuthURI:request callback:callback];
}

+ (void)getAccountInfo:(FIRGetAccountInfoRequest *)request
              callback:(FIRGetAccountInfoResponseCallback)callback {
  [[self implementation] getAccountInfo:request callback:callback];
}

+ (void)getProjectConfig:(FIRGetProjectConfigRequest *)request
                callback:(FIRGetProjectConfigResponseCallback)callback {
  [[self implementation] getProjectConfig:request callback:callback];
}

+ (void)setAccountInfo:(FIRSetAccountInfoRequest *)request
              callback:(FIRSetAccountInfoResponseCallback)callback {
  [[self implementation] setAccountInfo:request callback:callback];
}

+ (void)verifyAssertion:(FIRVerifyAssertionRequest *)request
               callback:(FIRVerifyAssertionResponseCallback)callback {
  [[self implementation] verifyAssertion:request callback:callback];
}

+ (void)verifyCustomToken:(FIRVerifyCustomTokenRequest *)request
                 callback:(FIRVerifyCustomTokenResponseCallback)callback {
  [[self implementation] verifyCustomToken:request callback:callback];
}

+ (void)verifyPassword:(FIRVerifyPasswordRequest *)request
              callback:(FIRVerifyPasswordResponseCallback)callback {
  [[self implementation] verifyPassword:request callback:callback];
}

+ (void)emailLinkSignin:(FIREmailLinkSignInRequest *)request
               callback:(FIREmailLinkSigninResponseCallback)callback {
  [[self implementation] emailLinkSignin:request callback:callback];
}

+ (void)secureToken:(FIRSecureTokenRequest *)request
           callback:(FIRSecureTokenResponseCallback)callback {
  [[self implementation] secureToken:request callback:callback];
}

+ (void)getOOBConfirmationCode:(FIRGetOOBConfirmationCodeRequest *)request
                      callback:(FIRGetOOBConfirmationCodeResponseCallback)callback {
  [[self implementation] getOOBConfirmationCode:request callback:callback];
}

+ (void)signUpNewUser:(FIRSignUpNewUserRequest *)request
             callback:(FIRSignupNewUserCallback)callback {
  [[self implementation] signUpNewUser:request callback:callback];
}

+ (void)deleteAccount:(FIRDeleteAccountRequest *)request callback:(FIRDeleteCallBack)callback {
  [[self implementation] deleteAccount:request callback:callback];
}

+ (void)signInWithGameCenter:(FIRSignInWithGameCenterRequest *)request
                    callback:(FIRSignInWithGameCenterResponseCallback)callback {
  [[self implementation] signInWithGameCenter:request callback:callback];
}

#if TARGET_OS_IOS
+ (void)sendVerificationCode:(FIRSendVerificationCodeRequest *)request
                    callback:(FIRSendVerificationCodeResponseCallback)callback {
  [[self implementation] sendVerificationCode:request callback:callback];
}

+ (void)verifyPhoneNumber:(FIRVerifyPhoneNumberRequest *)request
                 callback:(FIRVerifyPhoneNumberResponseCallback)callback {
  [[self implementation] verifyPhoneNumber:request callback:callback];
}

+ (void)verifyClient:(id)request callback:(FIRVerifyClientResponseCallback)callback {
  [[self implementation] verifyClient:request callback:callback];
}

#endif

+ (void)revokeToken:(FIRRevokeTokenRequest *)request
           callback:(FIRRevokeTokenResponseCallback)callback {
  [[self implementation] revokeToken:request callback:callback];
}

+ (void)resetPassword:(FIRResetPasswordRequest *)request
             callback:(FIRResetPasswordCallback)callback {
  [[self implementation] resetPassword:request callback:callback];
}

+ (void)getRecaptchaConfig:(FIRGetRecaptchaConfigRequest *)request
                  callback:(FIRGetRecaptchaConfigResponseCallback)callback {
  [[self implementation] getRecaptchaConfig:request callback:callback];
}

+ (NSString *)authUserAgent {
  return [NSString stringWithFormat:@"FirebaseAuth.iOS/%@ %@", FIRFirebaseVersion(),
                                    GTMFetcherStandardUserAgentString(nil)];
}

+ (void)requestWithURL:(NSURL *)URL
             contentType:(NSString *)contentType
    requestConfiguration:(FIRAuthRequestConfiguration *)requestConfiguration
       completionHandler:(void (^)(NSMutableURLRequest *_Nullable))completionHandler {
  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:URL];
  [request setValue:contentType forHTTPHeaderField:@"Content-Type"];
  NSString *additionalFrameworkMarker =
      requestConfiguration.additionalFrameworkMarker ?: kFirebaseAuthCoreFrameworkMarker;
  NSString *clientVersion = [NSString
      stringWithFormat:@"iOS/FirebaseSDK/%@/%@", FIRFirebaseVersion(), additionalFrameworkMarker];
  [request setValue:clientVersion forHTTPHeaderField:kClientVersionHeader];
  NSString *bundleID = [[NSBundle mainBundle] bundleIdentifier];
  [request setValue:bundleID forHTTPHeaderField:kIosBundleIdentifierHeader];
  NSString *appID = requestConfiguration.appID;
  [request setValue:appID forHTTPHeaderField:kFirebaseAppIDHeader];
  [request setValue:FIRHeaderValueFromHeartbeatsPayload(
                        [requestConfiguration.heartbeatLogger flushHeartbeatsIntoPayload])
      forHTTPHeaderField:kFirebaseHeartbeatHeader];
  NSString *HTTPMethod = requestConfiguration.HTTPMethod;
  [request setValue:HTTPMethod forKey:@"HTTPMethod"];
  NSArray<NSString *> *preferredLocalizations = [NSBundle mainBundle].preferredLocalizations;
  if (preferredLocalizations.count) {
    NSString *acceptLanguage = preferredLocalizations.firstObject;
    [request setValue:acceptLanguage forHTTPHeaderField:@"Accept-Language"];
  }
  NSString *languageCode = requestConfiguration.languageCode;
  if (languageCode.length) {
    [request setValue:languageCode forHTTPHeaderField:kFirebaseLocalHeader];
  }
  if (requestConfiguration.appCheck) {
    [requestConfiguration.appCheck
        getTokenForcingRefresh:false
                    completion:^(id<FIRAppCheckTokenResultInterop> _Nonnull tokenResult) {
                      if (tokenResult.error) {
                        FIRLogWarning(kFIRLoggerAuth, @"I-AUT000018",
                                      @"Error getting App Check token; using placeholder token "
                                      @"instead. Error: %@",
                                      tokenResult.error);
                      }
                      [request setValue:tokenResult.token
                          forHTTPHeaderField:@"X-Firebase-AppCheck"];
                      completionHandler(request);
                    }];
  } else {
    completionHandler(request);
  }
}

@end

@interface FIRAuthBackendRPCIssuerImplementation : NSObject <FIRAuthBackendRPCIssuer>
@end

@implementation FIRAuthBackendRPCIssuerImplementation {
  /** @var The session fetcher service.
   */
  GTMSessionFetcherService *_fetcherService;
}

- (instancetype)init {
  self = [super init];
  if (self) {
    _fetcherService = [[GTMSessionFetcherService alloc] init];
    _fetcherService.userAgent = [FIRAuthBackend authUserAgent];
    _fetcherService.callbackQueue = FIRAuthGlobalWorkQueue();

    // Avoid reusing the session to prevent
    // https://github.com/firebase/firebase-ios-sdk/issues/1261
    _fetcherService.reuseSession = NO;
  }
  return self;
}

- (void)asyncCallToURLWithRequestConfiguration:(FIRAuthRequestConfiguration *)requestConfiguration
                                           URL:(NSURL *)URL
                                          body:(nullable NSData *)body
                                   contentType:(NSString *)contentType
                             completionHandler:
                                 (void (^)(NSData *_Nullable, NSError *_Nullable))handler {
  [FIRAuthBackend requestWithURL:URL
                     contentType:contentType
            requestConfiguration:requestConfiguration
               completionHandler:^(NSMutableURLRequest *request) {
                 GTMSessionFetcher *fetcher = [self->_fetcherService fetcherWithRequest:request];
                 NSString *emulatorHostAndPort = requestConfiguration.emulatorHostAndPort;
                 if (emulatorHostAndPort) {
                   fetcher.allowLocalhostRequest = YES;
                   fetcher.allowedInsecureSchemes = @[ @"http" ];
                 }
                 fetcher.bodyData = body;
                 [fetcher beginFetchWithCompletionHandler:handler];
               }];
}

@end

@implementation FIRAuthBackendRPCImplementation

- (instancetype)init {
  self = [super init];
  if (self) {
    _RPCIssuer = [[FIRAuthBackendRPCIssuerImplementation alloc] init];
  }
  return self;
}

- (void)createAuthURI:(FIRCreateAuthURIRequest *)request
             callback:(FIRCreateAuthURIResponseCallback)callback {
  FIRCreateAuthURIResponse *response = [[FIRCreateAuthURIResponse alloc] init];
  [self callWithRequest:request
               response:response
               callback:^(NSError *error) {
                 if (error) {
                   callback(nil, error);
                 } else {
                   callback(response, nil);
                 }
               }];
}

- (void)getAccountInfo:(FIRGetAccountInfoRequest *)request
              callback:(FIRGetAccountInfoResponseCallback)callback {
  FIRGetAccountInfoResponse *response = [[FIRGetAccountInfoResponse alloc] init];
  [self callWithRequest:request
               response:response
               callback:^(NSError *error) {
                 if (error) {
                   callback(nil, error);
                 } else {
                   callback(response, nil);
                 }
               }];
}

- (void)getProjectConfig:(FIRGetProjectConfigRequest *)request
                callback:(FIRGetProjectConfigResponseCallback)callback {
  FIRGetProjectConfigResponse *response = [[FIRGetProjectConfigResponse alloc] init];
  [self callWithRequest:request
               response:response
               callback:^(NSError *error) {
                 if (error) {
                   callback(nil, error);
                 } else {
                   callback(response, nil);
                 }
               }];
}

- (void)setAccountInfo:(FIRSetAccountInfoRequest *)request
              callback:(FIRSetAccountInfoResponseCallback)callback {
  FIRSetAccountInfoResponse *response = [[FIRSetAccountInfoResponse alloc] init];
  [self callWithRequest:request
               response:response
               callback:^(NSError *error) {
                 if (error) {
                   callback(nil, error);
                 } else {
                   callback(response, nil);
                 }
               }];
}

- (void)verifyAssertion:(FIRVerifyAssertionRequest *)request
               callback:(FIRVerifyAssertionResponseCallback)callback {
  FIRVerifyAssertionResponse *response = [[FIRVerifyAssertionResponse alloc] init];
  [self
      callWithRequest:request
             response:response
             callback:^(NSError *error) {
               if (error) {
                 callback(nil, error);
               } else {
                 if (!response.IDToken && response.MFAInfo) {
#if TARGET_OS_IOS
                   NSMutableArray<FIRMultiFactorInfo *> *multiFactorInfoArray =
                       [[NSMutableArray alloc] init];
                   for (FIRAuthProtoMFAEnrollment *MFAEnrollment in response.MFAInfo) {
                     if (MFAEnrollment.phoneInfo) {
                       FIRMultiFactorInfo *multiFactorInfo =
                           [[FIRPhoneMultiFactorInfo alloc] initWithProto:MFAEnrollment];
                       [multiFactorInfoArray addObject:multiFactorInfo];
                     } else if (MFAEnrollment.TOTPInfo) {
                       FIRMultiFactorInfo *multiFactorInfo =
                           [[FIRTOTPMultiFactorInfo alloc] initWithProto:MFAEnrollment];
                       [multiFactorInfoArray addObject:multiFactorInfo];
                     } else {
                       FIRLogError(kFIRLoggerAuth, @"I-AUT000020",
                                   @"Multifactor type is not supported");
                     }
                   }
                   NSError *multiFactorRequiredError = [FIRAuthErrorUtils
                       secondFactorRequiredErrorWithPendingCredential:response.MFAPendingCredential
                                                                hints:multiFactorInfoArray
                                                                 auth:request.requestConfiguration
                                                                          .auth];
                   callback(nil, multiFactorRequiredError);
#endif
                 } else {
                   callback(response, nil);
                 }
               }
             }];
}

- (void)verifyCustomToken:(FIRVerifyCustomTokenRequest *)request
                 callback:(FIRVerifyCustomTokenResponseCallback)callback {
  FIRVerifyCustomTokenResponse *response = [[FIRVerifyCustomTokenResponse alloc] init];
  [self callWithRequest:request
               response:response
               callback:^(NSError *error) {
                 if (error) {
                   callback(nil, error);
                 } else {
                   callback(response, nil);
                 }
               }];
}

- (void)verifyPassword:(FIRVerifyPasswordRequest *)request
              callback:(FIRVerifyPasswordResponseCallback)callback {
  FIRVerifyPasswordResponse *response = [[FIRVerifyPasswordResponse alloc] init];
  [self
      callWithRequest:request
             response:response
             callback:^(NSError *error) {
               if (error) {
                 callback(nil, error);
               } else {
                 if (!response.IDToken && response.MFAInfo) {
#if TARGET_OS_IOS
                   NSMutableArray<FIRMultiFactorInfo *> *multiFactorInfo = [NSMutableArray array];
                   for (FIRAuthProtoMFAEnrollment *MFAEnrollment in response.MFAInfo) {
                     // check which MFA factors are enabled.
                     if (MFAEnrollment.phoneInfo != nil) {
                       FIRPhoneMultiFactorInfo *info =
                           [[FIRPhoneMultiFactorInfo alloc] initWithProto:MFAEnrollment];
                       [multiFactorInfo addObject:info];
                     } else if (MFAEnrollment.TOTPInfo != nil) {
                       FIRTOTPMultiFactorInfo *info =
                           [[FIRTOTPMultiFactorInfo alloc] initWithProto:MFAEnrollment];
                       [multiFactorInfo addObject:info];
                     } else {
                       FIRLogError(kFIRLoggerAuth, @"I-AUT000021",
                                   @"Multifactor type is not supported");
                     }
                   }
                   NSError *multiFactorRequiredError = [FIRAuthErrorUtils
                       secondFactorRequiredErrorWithPendingCredential:response.MFAPendingCredential
                                                                hints:multiFactorInfo
                                                                 auth:request.requestConfiguration
                                                                          .auth];
                   callback(nil, multiFactorRequiredError);
#endif
                 } else {
                   callback(response, nil);
                 }
               }
             }];
}

- (void)emailLinkSignin:(FIREmailLinkSignInRequest *)request
               callback:(FIREmailLinkSigninResponseCallback)callback {
  FIREmailLinkSignInResponse *response = [[FIREmailLinkSignInResponse alloc] init];
  [self
      callWithRequest:request
             response:response
             callback:^(NSError *error) {
               if (error) {
                 callback(nil, error);
               } else {
                 if (!response.IDToken && response.MFAInfo) {
#if TARGET_OS_IOS
                   NSMutableArray<FIRMultiFactorInfo *> *multiFactorInfoArray =
                       [[NSMutableArray alloc] init];
                   for (FIRAuthProtoMFAEnrollment *MFAEnrollment in response.MFAInfo) {
                     if (MFAEnrollment.phoneInfo) {
                       FIRMultiFactorInfo *multiFactorInfo =
                           [[FIRPhoneMultiFactorInfo alloc] initWithProto:MFAEnrollment];
                       [multiFactorInfoArray addObject:multiFactorInfo];
                     } else if (MFAEnrollment.TOTPInfo) {
                       FIRMultiFactorInfo *multiFactorInfo =
                           [[FIRTOTPMultiFactorInfo alloc] initWithProto:MFAEnrollment];
                       [multiFactorInfoArray addObject:multiFactorInfo];
                     } else {
                       FIRLogError(kFIRLoggerAuth, @"I-AUT000022",
                                   @"Multifactor type is not supported");
                     }
                   }
                   NSError *multiFactorRequiredError = [FIRAuthErrorUtils
                       secondFactorRequiredErrorWithPendingCredential:response.MFAPendingCredential
                                                                hints:multiFactorInfoArray
                                                                 auth:request.requestConfiguration
                                                                          .auth];
                   callback(nil, multiFactorRequiredError);
#endif
                 } else {
                   callback(response, nil);
                 }
               }
             }];
}

- (void)secureToken:(FIRSecureTokenRequest *)request
           callback:(FIRSecureTokenResponseCallback)callback {
  FIRSecureTokenResponse *response = [[FIRSecureTokenResponse alloc] init];
  [self callWithRequest:request
               response:response
               callback:^(NSError *error) {
                 if (error) {
                   callback(nil, error);
                 } else {
                   callback(response, nil);
                 }
               }];
}

- (void)getOOBConfirmationCode:(FIRGetOOBConfirmationCodeRequest *)request
                      callback:(FIRGetOOBConfirmationCodeResponseCallback)callback {
  FIRGetOOBConfirmationCodeResponse *response = [[FIRGetOOBConfirmationCodeResponse alloc] init];
  [self callWithRequest:request
               response:response
               callback:^(NSError *error) {
                 if (error) {
                   callback(nil, error);
                 } else {
                   callback(response, nil);
                 }
               }];
}

- (void)signUpNewUser:(FIRSignUpNewUserRequest *)request
             callback:(FIRSignupNewUserCallback)callback {
  FIRSignUpNewUserResponse *response = [[FIRSignUpNewUserResponse alloc] init];
  [self callWithRequest:request
               response:response
               callback:^(NSError *error) {
                 if (error) {
                   callback(nil, error);
                 } else {
                   callback(response, nil);
                 }
               }];
}

- (void)deleteAccount:(FIRDeleteAccountRequest *)request callback:(FIRDeleteCallBack)callback {
  FIRDeleteAccountResponse *response = [[FIRDeleteAccountResponse alloc] init];
  [self callWithRequest:request response:response callback:callback];
}

#if TARGET_OS_IOS
- (void)sendVerificationCode:(FIRSendVerificationCodeRequest *)request
                    callback:(FIRSendVerificationCodeResponseCallback)callback {
  FIRSendVerificationCodeResponse *response = [[FIRSendVerificationCodeResponse alloc] init];
  [self callWithRequest:request
               response:response
               callback:^(NSError *error) {
                 if (error) {
                   callback(nil, error);
                 } else {
                   callback(response, error);
                 }
               }];
}

- (void)verifyPhoneNumber:(FIRVerifyPhoneNumberRequest *)request
                 callback:(FIRVerifyPhoneNumberResponseCallback)callback {
  FIRVerifyPhoneNumberResponse *response = [[FIRVerifyPhoneNumberResponse alloc] init];
  [self
      callWithRequest:request
             response:response
             callback:^(NSError *error) {
               if (error) {
                 callback(nil, error);
                 return;
               }
               // Check whether or not the successful response is actually the special case phone
               // auth flow that returns a temporary proof and phone number.
               if (response.phoneNumber.length && response.temporaryProof.length) {
                 FIRPhoneAuthCredential *credential =
                     [[FIRPhoneAuthCredential alloc] initWithTemporaryProof:response.temporaryProof
                                                                phoneNumber:response.phoneNumber
                                                                 providerID:FIRPhoneAuthProviderID];
                 callback(nil, [FIRAuthErrorUtils credentialAlreadyInUseErrorWithMessage:nil
                                                                              credential:credential
                                                                                   email:nil]);
                 return;
               }
               callback(response, nil);
             }];
}

- (void)verifyClient:(id)request callback:(FIRVerifyClientResponseCallback)callback {
  FIRVerifyClientResponse *response = [[FIRVerifyClientResponse alloc] init];
  [self callWithRequest:request
               response:response
               callback:^(NSError *error) {
                 if (error) {
                   callback(nil, error);
                   return;
                 }
                 callback(response, nil);
               }];
}

#endif

- (void)revokeToken:(FIRRevokeTokenRequest *)request
           callback:(FIRRevokeTokenResponseCallback)callback {
  FIRRevokeTokenResponse *response = [[FIRRevokeTokenResponse alloc] init];
  [self
      callWithRequest:request
             response:response
             callback:^(NSError *error) {
               if (error) {
                 callback(nil, [FIRAuthErrorUtils
                                   invalidCredentialErrorWithMessage:[error localizedDescription]]);
                 return;
               }
               callback(response, nil);
             }];
}

- (void)resetPassword:(FIRResetPasswordRequest *)request
             callback:(FIRResetPasswordCallback)callback {
  FIRResetPasswordResponse *response = [[FIRResetPasswordResponse alloc] init];
  [self callWithRequest:request
               response:response
               callback:^(NSError *error) {
                 if (error) {
                   callback(nil, error);
                   return;
                 }
                 callback(response, nil);
               }];
}

- (void)signInWithGameCenter:(FIRSignInWithGameCenterRequest *)request
                    callback:(FIRSignInWithGameCenterResponseCallback)callback {
  FIRSignInWithGameCenterResponse *response = [[FIRSignInWithGameCenterResponse alloc] init];
  [self callWithRequest:request
               response:response
               callback:^(NSError *error) {
                 if (error) {
                   if (callback) {
                     callback(nil, error);
                   }
                 } else {
                   if (callback) {
                     callback(response, nil);
                   }
                 }
               }];
}

- (void)getRecaptchaConfig:(FIRGetRecaptchaConfigRequest *)request
                  callback:(FIRGetRecaptchaConfigResponseCallback)callback {
  FIRGetRecaptchaConfigResponse *response = [[FIRGetRecaptchaConfigResponse alloc] init];
  [self callWithRequest:request
               response:response
               callback:^(NSError *error) {
                 if (error) {
                   if (callback) {
                     callback(nil, error);
                   }
                 } else {
                   if (callback) {
                     callback(response, nil);
                   }
                 }
               }];
}

#pragma mark - Generic RPC handling methods

/** @fn callWithRequest:response:callback:
    @brief Calls the RPC using HTTP request.
    @remarks Possible error responses:
        @see FIRAuthInternalErrorCodeRPCRequestEncodingError
        @see FIRAuthInternalErrorCodeJSONSerializationError
        @see FIRAuthInternalErrorCodeNetworkError
        @see FIRAuthInternalErrorCodeUnexpectedErrorResponse
        @see FIRAuthInternalErrorCodeUnexpectedResponse
        @see FIRAuthInternalErrorCodeRPCResponseDecodingError
    @param request The request.
    @param response The empty response to be filled.
    @param callback The callback for both success and failure.
 */
- (void)callWithRequest:(id<FIRAuthRPCRequest>)request
               response:(id<FIRAuthRPCResponse>)response
               callback:(void (^)(NSError *_Nullable error))callback {
  NSError *error;
  NSData *bodyData;
  if ([request containsPostBody]) {
    id postBody = [request unencodedHTTPRequestBodyWithError:&error];
    if (!postBody) {
      callback([FIRAuthErrorUtils RPCRequestEncodingErrorWithUnderlyingError:error]);
      return;
    }

    NSJSONWritingOptions JSONWritingOptions = 0;
#if DEBUG
    JSONWritingOptions |= NSJSONWritingPrettyPrinted;
#endif

    if ([NSJSONSerialization isValidJSONObject:postBody]) {
      bodyData = [NSJSONSerialization dataWithJSONObject:postBody
                                                 options:JSONWritingOptions
                                                   error:&error];
      if (!bodyData) {
        // This is an untested case. This happens exclusively when there is an error in the
        // framework implementation of dataWithJSONObject:options:error:. This shouldn't normally
        // occur as isValidJSONObject: should return NO in any case we should encounter an error.
        error = [FIRAuthErrorUtils JSONSerializationErrorWithUnderlyingError:error];
      }
    } else {
      error = [FIRAuthErrorUtils JSONSerializationErrorForUnencodableType];
    }
    if (!bodyData) {
      callback(error);
      return;
    }
  }

  [_RPCIssuer
      asyncCallToURLWithRequestConfiguration:[request requestConfiguration]
                                         URL:[request requestURL]
                                        body:bodyData
                                 contentType:kJSONContentType
                           completionHandler:^(NSData *data, NSError *error) {
                             // If there is an error with no body data at all, then this must be a
                             // network error.
                             if (error && !data) {
                               callback([FIRAuthErrorUtils networkErrorWithUnderlyingError:error]);
                               return;
                             }

                             // Try to decode the HTTP response data which may contain either a
                             // successful response or error message.
                             NSError *jsonError;
                             NSDictionary *dictionary =
                                 [NSJSONSerialization JSONObjectWithData:data
                                                                 options:NSJSONReadingMutableLeaves
                                                                   error:&jsonError];
                             if (!dictionary) {
                               if (error) {
                                 // We have an error, but we couldn't decode the body, so we have no
                                 // additional information other than the raw response and the
                                 // original NSError (the jsonError is infered by the error code
                                 // (FIRAuthErrorCodeUnexpectedHTTPResponse, and is irrelevant.)
                                 callback([FIRAuthErrorUtils
                                     unexpectedErrorResponseWithData:data
                                                     underlyingError:error]);
                               } else {
                                 // This is supposed to be a "successful" response, but we couldn't
                                 // deserialize the body.
                                 callback([FIRAuthErrorUtils unexpectedResponseWithData:data
                                                                        underlyingError:jsonError]);
                               }
                               return;
                             }
                             if (![dictionary isKindOfClass:[NSDictionary class]]) {
                               if (error) {
                                 callback([FIRAuthErrorUtils
                                     unexpectedErrorResponseWithDeserializedResponse:dictionary
                                                                     underlyingError:error]);
                               } else {
                                 callback([FIRAuthErrorUtils
                                     unexpectedResponseWithDeserializedResponse:dictionary]);
                               }
                               return;
                             }

                             // At this point we either have an error with successfully decoded
                             // details in the body, or we have a response which must pass further
                             // validation before we know it's truly successful. We deal with the
                             // case where we have an error with successfully decoded error details
                             // first:
                             if (error) {
                               NSDictionary *errorDictionary = dictionary[kErrorKey];
                               if ([errorDictionary isKindOfClass:[NSDictionary class]]) {
                                 id<NSObject> errorMessage = errorDictionary[kErrorMessageKey];
                                 if ([errorMessage isKindOfClass:[NSString class]]) {
                                   NSString *errorMessageString = (NSString *)errorMessage;

                                   // Contruct client error.
                                   NSError *clientError = [[self class]
                                       clientErrorWithServerErrorMessage:errorMessageString
                                                         errorDictionary:errorDictionary
                                                                response:response];
                                   if (clientError) {
                                     callback(clientError);
                                     return;
                                   }
                                 }
                                 // Not a message we know, return the message directly.
                                 if (errorMessage) {
                                   NSError *unexpecterErrorResponse = [FIRAuthErrorUtils
                                       unexpectedErrorResponseWithDeserializedResponse:
                                           errorDictionary
                                                                       underlyingError:error];
                                   callback(unexpecterErrorResponse);
                                   return;
                                 }
                               }
                               // No error message at all, return the decoded response.
                               callback([FIRAuthErrorUtils
                                   unexpectedErrorResponseWithDeserializedResponse:dictionary
                                                                   underlyingError:error]);
                               return;
                             }

                             // Finally, we try to populate the response object with the JSON
                             // values.
                             if (![response setWithDictionary:dictionary error:&error]) {
                               callback([FIRAuthErrorUtils
                                   RPCResponseDecodingErrorWithDeserializedResponse:dictionary
                                                                    underlyingError:error]);
                               return;
                             }
                             // In case returnIDPCredential of a verifyAssertion request is set to
                             // @YES, the server may return a 200 with a response that may contain a
                             // server error.
                             if ([request isKindOfClass:[FIRVerifyAssertionRequest class]]) {
                               FIRVerifyAssertionRequest *verifyAssertionRequest =
                                   (FIRVerifyAssertionRequest *)request;
                               if (verifyAssertionRequest.returnIDPCredential) {
                                 NSString *errorMessage =
                                     dictionary[kReturnIDPCredentialErrorMessageKey];
                                 if ([errorMessage isKindOfClass:[NSString class]]) {
                                   NSString *errorString = (NSString *)errorMessage;
                                   NSError *clientError =
                                       [[self class] clientErrorWithServerErrorMessage:errorString
                                                                       errorDictionary:@{}
                                                                              response:response];
                                   if (clientError) {
                                     callback(clientError);
                                     return;
                                   }
                                 }
                               }
                             }
                             // Success! The response object originally passed in can be used by the
                             // caller.
                             callback(nil);
                           }];
}

/** @fn clientErrorWithServerErrorMessage:errorDictionary:
    @brief Translates known server errors to client errors.
    @param serverErrorMessage The error message from the server.
    @param errorDictionary The error part of the response from the server.
    @param response The response from the server RPC.
    @return A client error, if any.
 */
+ (nullable NSError *)clientErrorWithServerErrorMessage:(NSString *)serverErrorMessage
                                        errorDictionary:(NSDictionary *)errorDictionary
                                               response:(id<FIRAuthRPCResponse>)response {
  NSString *shortErrorMessage = serverErrorMessage;
  NSString *serverDetailErrorMessage;
  NSRange colonRange = [serverErrorMessage rangeOfString:@":"];
  if (colonRange.location != NSNotFound) {
    shortErrorMessage = [serverErrorMessage substringToIndex:colonRange.location];
    shortErrorMessage =
        [shortErrorMessage stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
    serverDetailErrorMessage = [serverErrorMessage substringFromIndex:colonRange.location + 1];
    serverDetailErrorMessage = [serverDetailErrorMessage
        stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
  }

  // Delegate the responsibility for constructing the client error to the response object,
  // if possible.
  SEL clientErrorWithServerErrorMessageSelector = @selector(clientErrorWithShortErrorMessage:
                                                                          detailErrorMessage:);
  if ([response respondsToSelector:clientErrorWithServerErrorMessageSelector]) {
    NSError *error = [response clientErrorWithShortErrorMessage:shortErrorMessage
                                             detailErrorMessage:serverDetailErrorMessage];
    if (error) {
      return error;
    }
  }

  if ([shortErrorMessage isEqualToString:kUserNotFoundErrorMessage]) {
    return [FIRAuthErrorUtils userNotFoundErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kUserDeletedErrorMessage]) {
    return [FIRAuthErrorUtils userNotFoundErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidLocalIDErrorMessage]) {
    // This case shouldn't be necessary but it is for now: b/27908364 .
    return [FIRAuthErrorUtils userNotFoundErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kUserTokenExpiredErrorMessage]) {
    return [FIRAuthErrorUtils userTokenExpiredErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kTooManyRequestsErrorMessage]) {
    return [FIRAuthErrorUtils tooManyRequestsErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidCustomTokenErrorMessage]) {
    return [FIRAuthErrorUtils invalidCustomTokenErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kCustomTokenMismatch]) {
    return [FIRAuthErrorUtils customTokenMistmatchErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidCredentialErrorMessage] ||
      [shortErrorMessage isEqualToString:kInvalidPendingToken] ||
      [shortErrorMessage isEqualToString:kInvalidLoginCredentials]) {
    return [FIRAuthErrorUtils invalidCredentialErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kUserDisabledErrorMessage]) {
    return [FIRAuthErrorUtils userDisabledErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kOperationNotAllowedErrorMessage]) {
    return [FIRAuthErrorUtils operationNotAllowedErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kPasswordLoginDisabledErrorMessage]) {
    return [FIRAuthErrorUtils operationNotAllowedErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kEmailAlreadyInUseErrorMessage]) {
    return [FIRAuthErrorUtils emailAlreadyInUseErrorWithEmail:nil];
  }

  if ([shortErrorMessage isEqualToString:kInvalidEmailErrorMessage]) {
    return [FIRAuthErrorUtils invalidEmailErrorWithMessage:serverDetailErrorMessage];
  }

  // "INVALID_IDENTIFIER" can be returned by createAuthURI RPC. Considering email addresses are
  //  currently the only identifiers, we surface the FIRAuthErrorCodeInvalidEmail error code in this
  //  case.
  if ([shortErrorMessage isEqualToString:kInvalidIdentifierErrorMessage]) {
    return [FIRAuthErrorUtils invalidEmailErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kWrongPasswordErrorMessage]) {
    return [FIRAuthErrorUtils wrongPasswordErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kCredentialTooOldErrorMessage]) {
    return [FIRAuthErrorUtils requiresRecentLoginErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidUserTokenErrorMessage]) {
    return [FIRAuthErrorUtils invalidUserTokenErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kFederatedUserIDAlreadyLinkedMessage]) {
    FIROAuthCredential *credential;
    NSString *email;
    if ([response isKindOfClass:[FIRVerifyAssertionResponse class]]) {
      FIRVerifyAssertionResponse *verifyAssertion = (FIRVerifyAssertionResponse *)response;
      credential = [[FIROAuthCredential alloc] initWithVerifyAssertionResponse:verifyAssertion];
      email = verifyAssertion.email;
    }
    return [FIRAuthErrorUtils credentialAlreadyInUseErrorWithMessage:serverDetailErrorMessage
                                                          credential:credential
                                                               email:email];
  }

  if ([shortErrorMessage isEqualToString:kWeakPasswordErrorMessagePrefix]) {
    return [FIRAuthErrorUtils weakPasswordErrorWithServerResponseReason:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kExpiredActionCodeErrorMessage]) {
    return [FIRAuthErrorUtils expiredActionCodeErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidActionCodeErrorMessage]) {
    return [FIRAuthErrorUtils invalidActionCodeErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kMissingEmailErrorMessage]) {
    return [FIRAuthErrorUtils missingEmailErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidSenderEmailErrorMessage]) {
    return [FIRAuthErrorUtils invalidSenderErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidMessagePayloadErrorMessage]) {
    return [FIRAuthErrorUtils invalidMessagePayloadErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidRecipientEmailErrorMessage]) {
    return [FIRAuthErrorUtils invalidRecipientEmailErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kMissingIosBundleIDErrorMessage]) {
    return [FIRAuthErrorUtils missingIosBundleIDErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kMissingAndroidPackageNameErrorMessage]) {
    return [FIRAuthErrorUtils missingAndroidPackageNameErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kUnauthorizedDomainErrorMessage]) {
    return [FIRAuthErrorUtils unauthorizedDomainErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidContinueURIErrorMessage]) {
    return [FIRAuthErrorUtils invalidContinueURIErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidProviderIDErrorMessage]) {
    return [FIRAuthErrorUtils invalidProviderIDErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidDynamicLinkDomainErrorMessage]) {
    return [FIRAuthErrorUtils invalidDynamicLinkDomainErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kMissingContinueURIErrorMessage]) {
    return [FIRAuthErrorUtils missingContinueURIErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidPhoneNumberErrorMessage]) {
    return [FIRAuthErrorUtils invalidPhoneNumberErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidSessionInfoErrorMessage]) {
    return [FIRAuthErrorUtils invalidVerificationIDErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidVerificationCodeErrorMessage]) {
    return [FIRAuthErrorUtils invalidVerificationCodeErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kSessionExpiredErrorMessage]) {
    return [FIRAuthErrorUtils sessionExpiredErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kMissingAppTokenErrorMessage]) {
    return [FIRAuthErrorUtils missingAppTokenErrorWithUnderlyingError:nil];
  }

  if ([shortErrorMessage isEqualToString:kMissingAppCredentialErrorMessage]) {
    return [FIRAuthErrorUtils missingAppCredentialWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidAppCredentialErrorMessage]) {
    return [FIRAuthErrorUtils invalidAppCredentialWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kQuoutaExceededErrorMessage]) {
    return [FIRAuthErrorUtils quotaExceededErrorWithMessage:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kAppNotVerifiedErrorMessage]) {
    return [FIRAuthErrorUtils appNotVerifiedErrorWithMessage:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kMissingClientIdentifier]) {
    return [FIRAuthErrorUtils missingClientIdentifierErrorWithMessage:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kMissingClientType]) {
    return [FIRAuthErrorUtils missingClientTypeErrorWithMessage:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kCaptchaCheckFailedErrorMessage]) {
    return [FIRAuthErrorUtils captchaCheckFailedErrorWithMessage:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kMissingOrInvalidNonceErrorMessage]) {
    return [FIRAuthErrorUtils missingOrInvalidNonceErrorWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kMissingMFAPendingCredentialErrorMessage]) {
    return [FIRAuthErrorUtils errorWithCode:FIRAuthInternalErrorCodeMissingMultiFactorSession
                                    message:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kMissingMFAEnrollmentIDErrorMessage]) {
    return [FIRAuthErrorUtils errorWithCode:FIRAuthInternalErrorCodeMissingMultiFactorInfo
                                    message:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidMFAPendingCredentialErrorMessage]) {
    return [FIRAuthErrorUtils errorWithCode:FIRAuthInternalErrorCodeInvalidMultiFactorSession
                                    message:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kMFAEnrollmentNotFoundErrorMessage]) {
    return [FIRAuthErrorUtils errorWithCode:FIRAuthInternalErrorCodeMultiFactorInfoNotFound
                                    message:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kAdminOnlyOperationErrorMessage]) {
    return [FIRAuthErrorUtils errorWithCode:FIRAuthInternalErrorCodeAdminRestrictedOperation
                                    message:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kUnverifiedEmailErrorMessage]) {
    return [FIRAuthErrorUtils errorWithCode:FIRAuthInternalErrorCodeUnverifiedEmail
                                    message:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kSecondFactorExistsErrorMessage]) {
    return [FIRAuthErrorUtils errorWithCode:FIRAuthInternalErrorCodeSecondFactorAlreadyEnrolled
                                    message:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kSecondFactorLimitExceededErrorMessage]) {
    return [FIRAuthErrorUtils errorWithCode:FIRAuthInternalErrorCodeMaximumSecondFactorCountExceeded
                                    message:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kUnsupportedFirstFactorErrorMessage]) {
    return [FIRAuthErrorUtils errorWithCode:FIRAuthInternalErrorCodeUnsupportedFirstFactor
                                    message:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kEmailChangeNeedsVerificationErrorMessage]) {
    return [FIRAuthErrorUtils errorWithCode:FIRAuthInternalErrorCodeEmailChangeNeedsVerification
                                    message:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kTenantIDMismatch]) {
    return [FIRAuthErrorUtils tenantIDMismatchError];
  }

  if ([shortErrorMessage isEqualToString:kUnsupportedTenantOperation]) {
    return [FIRAuthErrorUtils unsupportedTenantOperationError];
  }

  if ([shortErrorMessage isEqualToString:kBlockingCloudFunctionErrorResponse]) {
    return
        [FIRAuthErrorUtils blockingCloudFunctionServerResponseWithMessage:serverDetailErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kInvalidRecaptchaScore]) {
    return [FIRAuthErrorUtils errorWithCode:FIRAuthInternalErrorCodeCaptchaCheckFailed
                                    message:serverErrorMessage];
  }

  if ([shortErrorMessage isEqualToString:kRecaptchaNotEnabled]) {
    return [FIRAuthErrorUtils errorWithCode:FIRAuthInternalErrorCodeRecaptchaNotEnabled
                                    message:serverErrorMessage];
  }

  // In this case we handle an error that might be specified in the underlying errors dictionary,
  // the error message in determined based on the @c reason key in the dictionary.
  if (errorDictionary[kErrorsKey]) {
    // Check for underlying error with reason = keyInvalid;
    id underlyingErrors = errorDictionary[kErrorsKey];
    if ([underlyingErrors isKindOfClass:[NSArray class]]) {
      NSArray *underlyingErrorsArray = (NSArray *)underlyingErrors;
      for (id underlyingError in underlyingErrorsArray) {
        if ([underlyingError isKindOfClass:[NSDictionary class]]) {
          NSDictionary *underlyingErrorDictionary = (NSDictionary *)underlyingError;
          NSString *reason = underlyingErrorDictionary[kReasonKey];
          if ([reason hasPrefix:kInvalidKeyReasonValue]) {
            return [FIRAuthErrorUtils invalidAPIKeyError];
          }
          if ([reason isEqualToString:kAppNotAuthorizedReasonValue]) {
            return [FIRAuthErrorUtils appNotAuthorizedError];
          }
        }
      }
    }
  }
  return nil;
}

@end

NS_ASSUME_NONNULL_END