firebase-ios-sdk/FirebaseAuth/Tests/SampleSwift/AuthenticationExample/ViewControllers/LoginController.swift

// Copyright 2020 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 FirebaseAuth
import UIKit

class LoginController: UIViewController {
  weak var delegate: (any LoginDelegate)?

  private var loginView: LoginView { view as! LoginView }

  private var email: String { loginView.emailTextField.text! }
  private var password: String { loginView.passwordTextField.text! }

  // Hides tab bar when view controller is presented
  override var hidesBottomBarWhenPushed: Bool { get { true } set {} }

  // MARK: - View Controller Lifecycle Methods

  override func loadView() {
    view = LoginView()
  }

  override func viewDidLoad() {
    super.viewDidLoad()
    configureNavigationBar()
    configureDelegatesAndHandlers()
  }

  override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    navigationController?.setTitleColor(.label)
  }

  override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    view.endEditing(true)
    navigationController?.setTitleColor(.systemOrange)
  }

  override func viewDidDisappear(_ animated: Bool) {
    super.viewDidDisappear(animated)
    navigationController?.popViewController(animated: false)
  }

  // Dismisses keyboard when view is tapped
  override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesBegan(touches, with: event)
    view.endEditing(true)
  }

  // MARK: - Firebase 🔥

  private func login(with email: String, password: String) {
    AppManager.shared.auth().signIn(withEmail: email, password: password) { result, error in
      if let error {
        let authError = error as NSError
        if authError.code == AuthErrorCode.secondFactorRequired.rawValue {
          let resolver = authError
            .userInfo[AuthErrorUserInfoMultiFactorResolverKey] as! MultiFactorResolver
          self.delegate?.loginDidOccur(resolver: resolver)
        } else {
          self.displayError(error)
        }
      } else {
        self.delegate?.loginDidOccur(resolver: nil)
      }
    }
  }

  private func createUser(email: String, password: String) {
    AppManager.shared.auth().createUser(withEmail: email, password: password) { authResult, error in
      guard error == nil else { return self.displayError(error) }
      self.delegate?.loginDidOccur(resolver: nil)
    }
  }

  // MARK: - Action Handlers

  @objc
  private func handleLogin() {
    login(with: email, password: password)
  }

  @objc
  private func handleCreateAccount() {
    createUser(email: email, password: password)
  }

  // MARK: - UI Configuration

  private func configureNavigationBar() {
    navigationItem.title = "Welcome"
    navigationItem.backBarButtonItem?.tintColor = .systemYellow
    navigationController?.navigationBar.prefersLargeTitles = true
  }

  private func configureDelegatesAndHandlers() {
    loginView.emailTextField.delegate = self
    loginView.passwordTextField.delegate = self
    loginView.loginButton.addTarget(self, action: #selector(handleLogin), for: .touchUpInside)
    loginView.createAccountButton.addTarget(
      self,
      action: #selector(handleCreateAccount),
      for: .touchUpInside
    )
  }

  override func viewWillTransition(to size: CGSize,
                                   with coordinator: any UIViewControllerTransitionCoordinator) {
    super.viewWillTransition(to: size, with: coordinator)
    loginView.emailTopConstraint.constant = UIDevice.current.orientation.isLandscape ? 15 : 50
    loginView.passwordTopConstraint.constant = UIDevice.current.orientation.isLandscape ? 5 : 20
  }
}

// MARK: - UITextFieldDelegate

extension LoginController: UITextFieldDelegate {
  func textFieldShouldReturn(_ textField: UITextField) -> Bool {
    if loginView.emailTextField.isFirstResponder, loginView.passwordTextField.text!.isEmpty {
      loginView.passwordTextField.becomeFirstResponder()
    } else {
      textField.resignFirstResponder()
    }
    return true
  }
}