[Auth] Convert *Response classes to structs

FirebaseAuth/Sources/Swift/Backend/AuthBackend.swift

@@ -22,82 +22,61 @@ import Foundation
 #endif
 
 @available(iOS 13, tvOS 13, macOS 10.15, macCatalyst 13, watchOS 7, *)
-protocol AuthBackendRPCIssuer {
-  /// Asynchronously send a HTTP request.
-  /// - Parameter request: The request to be made.
-  /// - Parameter body: Request body.
-  /// - Parameter contentType: Content type of the body.
-  /// - Parameter completionHandler: Handles HTTP response. Invoked asynchronously
-  ///  on the auth global  work queue in the future.
-  func asyncCallToURL<T: AuthRPCRequest>(with request: T,
-                                         body: Data?,
-                                         contentType: String) async -> (Data?, Error?)
-}
-
-@available(iOS 13, tvOS 13, macOS 10.15, macCatalyst 13, watchOS 7, *)
-class AuthBackendRPCIssuerImplementation: AuthBackendRPCIssuer {
-  let fetcherService: GTMSessionFetcherService
-
-  init() {
-    fetcherService = GTMSessionFetcherService()
-    fetcherService.userAgent = AuthBackend.authUserAgent()
-    fetcherService.callbackQueue = kAuthGlobalWorkQueue
-
-    // Avoid reusing the session to prevent
-    // https://github.com/firebase/firebase-ios-sdk/issues/1261
-    fetcherService.reuseSession = false
-  }
-
-  func asyncCallToURL<T: AuthRPCRequest>(with request: T,
-                                         body: Data?,
-                                         contentType: String) async -> (Data?, Error?) {
-    let requestConfiguration = request.requestConfiguration()
-    let request = await AuthBackend.request(withURL: request.requestURL(),
-                                            contentType: contentType,
-                                            requestConfiguration: requestConfiguration)
-    let fetcher = fetcherService.fetcher(with: request)
-    if let _ = requestConfiguration.emulatorHostAndPort {
-      fetcher.allowLocalhostRequest = true
-      fetcher.allowedInsecureSchemes = ["http"]
-    }
-    fetcher.bodyData = body
-
-    return await withUnsafeContinuation { continuation in
-      fetcher.beginFetch { data, error in
-        continuation.resume(returning: (data, error))
-      }
-    }
-  }
+protocol AuthBackendProtocol {
+  func call<T: AuthRPCRequest>(with request: T) async throws -> T.Response
 }
 
 @available(iOS 13, tvOS 13, macOS 10.15, macCatalyst 13, watchOS 7, *)
-class AuthBackend {
+class AuthBackend: AuthBackendProtocol {
   static func authUserAgent() -> String {
     return "FirebaseAuth.iOS/\(FirebaseVersion()) \(GTMFetcherStandardUserAgentString(nil))"
   }
 
-  private static var realRPCBackend = AuthBackendRPCImplementation()
-  private static var gBackendImplementation = realRPCBackend
+  static func call<T: AuthRPCRequest>(with request: T) async throws -> T.Response {
+    return try await shared.call(with: request)
+  }
 
-  class func setTestRPCIssuer(issuer: AuthBackendRPCIssuer) {
-    gBackendImplementation.rpcIssuer = issuer
+  static func setTestRPCIssuer(issuer: AuthBackendRPCIssuer) {
+    shared.rpcIssuer = issuer
   }
 
-  class func resetRPCIssuer() {
-    gBackendImplementation.rpcIssuer = realRPCBackend.rpcIssuer
+  static func resetRPCIssuer() {
+    shared.rpcIssuer = AuthBackendRPCIssuer()
   }
 
-  class func implementation() -> AuthBackendImplementation {
-    return gBackendImplementation
+  private static let shared: AuthBackend = .init(rpcIssuer: AuthBackendRPCIssuer())
+
+  private var rpcIssuer: any AuthBackendRPCIssuerProtocol
+
+  init(rpcIssuer: any AuthBackendRPCIssuerProtocol) {
+    self.rpcIssuer = rpcIssuer
   }
 
-  class func call<T: AuthRPCRequest>(with request: T) async throws -> T.Response {
-    return try await implementation().call(with: request)
+  /// Calls the RPC using HTTP request.
+  /// Possible error responses:
+  /// * See FIRAuthInternalErrorCodeRPCRequestEncodingError
+  /// * See FIRAuthInternalErrorCodeJSONSerializationError
+  /// * See FIRAuthInternalErrorCodeNetworkError
+  /// * See FIRAuthInternalErrorCodeUnexpectedErrorResponse
+  /// * See FIRAuthInternalErrorCodeUnexpectedResponse
+  /// * See FIRAuthInternalErrorCodeRPCResponseDecodingError
+  /// - Parameter request: The request.
+  /// - Returns: The response.
+  func call<T: AuthRPCRequest>(with request: T) async throws -> T.Response {
+    let response = try await callInternal(with: request)
+    if let auth = request.requestConfiguration().auth,
+       let mfaError = Self.generateMFAError(response: response, auth: auth) {
+      throw mfaError
+    } else if let error = Self.phoneCredentialInUse(response: response) {
+      throw error
+    } else {
+      return response
+    }
   }
 
-  class func request(withURL url: URL,
-                     contentType: String,
-                     requestConfiguration: AuthRequestConfiguration) async -> URLRequest {
+  static func request(withURL url: URL,
+                      contentType: String,
+                      requestConfiguration: AuthRequestConfiguration) async -> URLRequest {
     // Kick off tasks for the async header values.
     async let heartbeatsHeaderValue = requestConfiguration.heartbeatLogger?.asyncHeaderValue()
     async let appCheckTokenHeaderValue = requestConfiguration.appCheck?
@@ -132,41 +111,11 @@ class AuthBackend {
     }
     return request
   }
-}
 
-@available(iOS 13, tvOS 13, macOS 10.15, macCatalyst 13, watchOS 7, *)
-protocol AuthBackendImplementation {
-  func call<T: AuthRPCRequest>(with request: T) async throws -> T.Response
-}
-
-@available(iOS 13, tvOS 13, macOS 10.15, macCatalyst 13, watchOS 7, *)
-private class AuthBackendRPCImplementation: AuthBackendImplementation {
-  var rpcIssuer: AuthBackendRPCIssuer = AuthBackendRPCIssuerImplementation()
-
-  /// Calls the RPC using HTTP request.
-  /// Possible error responses:
-  /// * See FIRAuthInternalErrorCodeRPCRequestEncodingError
-  /// * See FIRAuthInternalErrorCodeJSONSerializationError
-  /// * See FIRAuthInternalErrorCodeNetworkError
-  /// * See FIRAuthInternalErrorCodeUnexpectedErrorResponse
-  /// * See FIRAuthInternalErrorCodeUnexpectedResponse
-  /// * See FIRAuthInternalErrorCodeRPCResponseDecodingError
-  /// - Parameter request: The request.
-  /// - Returns: The response.
-  fileprivate func call<T: AuthRPCRequest>(with request: T) async throws -> T.Response {
-    let response = try await callInternal(with: request)
-    if let auth = request.requestConfiguration().auth,
-       let mfaError = Self.generateMFAError(response: response, auth: auth) {
-      throw mfaError
-    } else if let error = Self.phoneCredentialInUse(response: response) {
-      throw error
-    } else {
-      return response
-    }
-  }
-
-  #if os(iOS)
-    private class func generateMFAError(response: AuthRPCResponse, auth: Auth) -> Error? {
+  private static func generateMFAError(response: AuthRPCResponse, auth: Auth) -> Error? {
+    #if !os(iOS)
+      return nil
+    #else
       if let mfaResponse = response as? AuthMFAResponse,
          mfaResponse.idToken == nil,
          let enrollments = mfaResponse.mfaInfo {
@@ -189,17 +138,15 @@ private class AuthBackendRPCImplementation: AuthBackendImplementation {
       } else {
         return nil
       }
-    }
-  #else
-    private class func generateMFAError(response: AuthRPCResponse, auth: Auth?) -> Error? {
-      return nil
-    }
-  #endif
+    #endif // !os(iOS)
+  }
 
-  #if os(iOS)
-    // Check whether or not the successful response is actually the special case phone
-    // auth flow that returns a temporary proof and phone number.
-    private class func phoneCredentialInUse(response: AuthRPCResponse) -> Error? {
+  // Check whether or not the successful response is actually the special case phone
+  // auth flow that returns a temporary proof and phone number.
+  private static func phoneCredentialInUse(response: AuthRPCResponse) -> Error? {
+    #if !os(iOS)
+      return nil
+    #else
       if let phoneAuthResponse = response as? VerifyPhoneNumberResponse,
          let phoneNumber = phoneAuthResponse.phoneNumber,
          phoneNumber.count > 0,
@@ -214,12 +161,8 @@ private class AuthBackendRPCImplementation: AuthBackendImplementation {
       } else {
         return nil
       }
-    }
-  #else
-    private class func phoneCredentialInUse(response: AuthRPCResponse) -> Error? {
-      return nil
-    }
-  #endif
+    #endif // !os(iOS)
+  }
 
   /// Calls the RPC using HTTP request.
   ///
@@ -308,7 +251,7 @@ private class AuthBackendRPCImplementation: AuthBackendImplementation {
     }
     dictionary = decodedDictionary
 
-    let response = T.Response()
+    var response = T.Response()
 
     // At this point we either have an error with successfully decoded
     // details in the body, or we have a response which must pass further
@@ -318,7 +261,7 @@ private class AuthBackendRPCImplementation: AuthBackendImplementation {
     if error != nil {
       if let errorDictionary = dictionary["error"] as? [String: AnyHashable] {
         if let errorMessage = errorDictionary["message"] as? String {
-          if let clientError = AuthBackendRPCImplementation.clientError(
+          if let clientError = Self.clientError(
             withServerErrorMessage: errorMessage,
             errorDictionary: errorDictionary,
             response: response,
@@ -351,7 +294,7 @@ private class AuthBackendRPCImplementation: AuthBackendImplementation {
     if let verifyAssertionRequest = request as? VerifyAssertionRequest {
       if verifyAssertionRequest.returnIDPCredential {
         if let errorMessage = dictionary["errorMessage"] as? String {
-          if let clientError = AuthBackendRPCImplementation.clientError(
+          if let clientError = Self.clientError(
             withServerErrorMessage: errorMessage,
             errorDictionary: dictionary,
             response: response,
@@ -365,10 +308,10 @@ private class AuthBackendRPCImplementation: AuthBackendImplementation {
     return response
   }
 
-  private class func clientError(withServerErrorMessage serverErrorMessage: String,
-                                 errorDictionary: [String: Any],
-                                 response: AuthRPCResponse,
-                                 error: Error?) -> Error? {
+  private static func clientError(withServerErrorMessage serverErrorMessage: String,
+                                  errorDictionary: [String: Any],
+                                  response: AuthRPCResponse,
+                                  error: Error?) -> Error? {
     let split = serverErrorMessage.split(separator: ":")
     let shortErrorMessage = split.first?.trimmingCharacters(in: .whitespacesAndNewlines)
     let serverDetailErrorMessage = String(split.count > 1 ? split[1] : "")

FirebaseAuth/Sources/Swift/Backend/AuthBackendRPCIssuer.swift

@@ -0,0 +1,71 @@
+// Copyright 2024 Google LLC
+//
+// 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 FirebaseCore
+import FirebaseCoreExtension
+import Foundation
+#if COCOAPODS
+  import GTMSessionFetcher
+#else
+  import GTMSessionFetcherCore
+#endif
+
+@available(iOS 13, tvOS 13, macOS 10.15, macCatalyst 13, watchOS 7, *)
+protocol AuthBackendRPCIssuerProtocol {
+  /// Asynchronously send a HTTP request.
+  /// - Parameter request: The request to be made.
+  /// - Parameter body: Request body.
+  /// - Parameter contentType: Content type of the body.
+  /// - Parameter completionHandler: Handles HTTP response. Invoked asynchronously
+  ///  on the auth global  work queue in the future.
+  func asyncCallToURL<T: AuthRPCRequest>(with request: T,
+                                         body: Data?,
+                                         contentType: String) async -> (Data?, Error?)
+}
+
+@available(iOS 13, tvOS 13, macOS 10.15, macCatalyst 13, watchOS 7, *)
+class AuthBackendRPCIssuer: AuthBackendRPCIssuerProtocol {
+  let fetcherService: GTMSessionFetcherService
+
+  init() {
+    fetcherService = GTMSessionFetcherService()
+    fetcherService.userAgent = AuthBackend.authUserAgent()
+    fetcherService.callbackQueue = kAuthGlobalWorkQueue
+
+    // Avoid reusing the session to prevent
+    // https://github.com/firebase/firebase-ios-sdk/issues/1261
+    fetcherService.reuseSession = false
+  }
+
+  func asyncCallToURL<T: AuthRPCRequest>(with request: T,
+                                         body: Data?,
+                                         contentType: String) async -> (Data?, Error?) {
+    let requestConfiguration = request.requestConfiguration()
+    let request = await AuthBackend.request(withURL: request.requestURL(),
+                                            contentType: contentType,
+                                            requestConfiguration: requestConfiguration)
+    let fetcher = fetcherService.fetcher(with: request)
+    if let _ = requestConfiguration.emulatorHostAndPort {
+      fetcher.allowLocalhostRequest = true
+      fetcher.allowedInsecureSchemes = ["http"]
+    }
+    fetcher.bodyData = body
+
+    return await withUnsafeContinuation { continuation in
+      fetcher.beginFetch { data, error in
+        continuation.resume(returning: (data, error))
+      }
+    }
+  }
+}

FirebaseAuth/Sources/Swift/Backend/AuthRPCResponse.swift

@@ -14,15 +14,15 @@
 
 import Foundation
 
-protocol AuthRPCResponse {
+protocol AuthRPCResponse: Sendable {
   /// Bare initializer for a response.
   init()
 
   /// Sets the response instance from the decoded JSON response.
   /// - Parameter dictionary: The dictionary decoded from HTTP JSON response.
   /// - Parameter error: An out field for an error which occurred constructing the request.
   /// - Returns: Whether the operation was successful or not.
-  func setFields(dictionary: [String: AnyHashable]) throws
+  mutating func setFields(dictionary: [String: AnyHashable]) throws
 
   /// This optional method allows response classes to create client errors given a short error
   /// message and a detail error message from the server.

FirebaseAuth/Sources/Swift/Backend/RPC/CreateAuthURIResponse.swift

@@ -16,8 +16,7 @@ import Foundation
 
 /// Represents the parameters for the createAuthUri endpoint.
 /// See https: // developers.google.com/identity/toolkit/web/reference/relyingparty/createAuthUri
-
-class CreateAuthURIResponse: AuthRPCResponse {
+struct CreateAuthURIResponse: AuthRPCResponse {
   /// The URI used by the IDP to authenticate the user.
   var authURI: String?
 
@@ -36,10 +35,7 @@ class CreateAuthURIResponse: AuthRPCResponse {
   /// A list of sign-in methods available for the passed identifier.
   var signinMethods: [String] = []
 
-  /// Bare initializer.
-  required init() {}
-
-  func setFields(dictionary: [String: AnyHashable]) throws {
+  mutating func setFields(dictionary: [String: AnyHashable]) throws {
     providerID = dictionary["providerId"] as? String
     authURI = dictionary["authUri"] as? String
     registered = dictionary["registered"] as? Bool ?? false

FirebaseAuth/Sources/Swift/Backend/RPC/DeleteAccountResponse.swift

@@ -17,8 +17,6 @@ import Foundation
 /// Represents the response from the deleteAccount endpoint.
 ///
 /// See https://developers.google.com/identity/toolkit/web/reference/relyingparty/deleteAccount
-class DeleteAccountResponse: AuthRPCResponse {
-  required init() {}
-
-  func setFields(dictionary: [String: AnyHashable]) throws {}
+struct DeleteAccountResponse: AuthRPCResponse {
+  mutating func setFields(dictionary: [String: AnyHashable]) throws {}
 }

FirebaseAuth/Sources/Swift/Backend/RPC/EmailLinkSignInResponse.swift

@@ -15,9 +15,7 @@
 import Foundation
 
 /// Represents the response from the emailLinkSignin endpoint.
-class EmailLinkSignInResponse: AuthRPCResponse, AuthMFAResponse {
-  required init() {}
-
+struct EmailLinkSignInResponse: AuthRPCResponse, AuthMFAResponse {
   /// The ID token in the email link sign-in response.
   private(set) var idToken: String?
 
@@ -42,7 +40,7 @@ class EmailLinkSignInResponse: AuthRPCResponse, AuthMFAResponse {
   /// Info on which multi-factor authentication providers are enabled.
   private(set) var mfaInfo: [AuthProtoMFAEnrollment]?
 
-  func setFields(dictionary: [String: AnyHashable]) throws {
+  mutating func setFields(dictionary: [String: AnyHashable]) throws {
     email = dictionary["email"] as? String
     idToken = dictionary["idToken"] as? String
     isNewUser = dictionary["isNewUser"] as? Bool ?? false