Tutorial 9: Handling User Input with Text Fields and Alerts

import UIKit

class ViewController: UIViewController {

    // Outlets for UI elements
    @IBOutlet weak var codeTextField: UITextField!
    @IBOutlet weak var submitButton: UIButton!
    @IBOutlet weak var levelLabel: UILabel!
    @IBOutlet weak var timerLabel: UILabel!

    // Define the secret codes for each level
    let codes = ["1234", "5678", "91011", "121314"]

    // Define the current level and the timer
    var currentLevel = 0
    var timer: Timer?
    var remainingTime = 10
    var totalAttempts = 0

    override func viewDidLoad() {
        super.viewDidLoad()
        startNewLevel()
    }

    // Action for the submit button
    @IBAction func submitCodeButtonTapped(_ sender: UIButton) {
        // Get the user input from the text field
        if let enteredCode = codeTextField.text, !enteredCode.isEmpty {
            totalAttempts += 1
            checkCode(enteredCode)
        } else {
            showErrorAlert(message: "Please enter a code to proceed.")
        }
    }

    // Function to start a new level
    func startNewLevel() {
        // Reset the timer and update the UI for the new level
        levelLabel.text = "Level: \(currentLevel + 1)"
        remainingTime = 10
        timerLabel.text = "Timer: \(remainingTime) sec"

        // Start a countdown timer
        startTimer()
    }

    // Timer functionality
    func startTimer() {
        // Invalidating any existing timer
        timer?.invalidate()

        // Create a new timer that updates every second
        timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(updateTimer), userInfo: nil, repeats: true)
    }

    @objc func updateTimer() {
        // Decrease remaining time by 1 second
        remainingTime -= 1

        // Update the timer label
        timerLabel.text = "Timer: \(remainingTime) sec"

        // If time runs out, end the level with failure
        if remainingTime <= 0 {
            timer?.invalidate()
            showFailureAlert(message: "Time's up! Mission failed.")
        }
    }

    // Function to check the entered code
    func checkCode(_ enteredCode: String) {
        // Check if the entered code is correct
        if enteredCode == codes[currentLevel] {
            showSuccessAlert(message: "Correct! Proceed to the next level.")
        } else {
            showFailureAlert(message: "Incorrect code. Try again!")
        }
    }

    // Show success alert
    func showSuccessAlert(message: String) {
        let alertController = UIAlertController(title: "Success!", message: message, preferredStyle: .alert)
        alertController.addAction(UIAlertAction(title: "Next Level", style: .default, handler: { _ in
            self.currentLevel += 1
            if self.currentLevel < self.codes.count {
                self.startNewLevel()
            } else {
                self.showMissionCompleteAlert()
            }
        }))
        self.present(alertController, animated: true, completion: nil)
    }

    // Show failure alert
    func showFailureAlert(message: String) {
        let alertController = UIAlertController(title: "Failure", message: message, preferredStyle: .alert)
        alertController.addAction(UIAlertAction(title: "Retry", style: .default, handler: nil))
        self.present(alertController, animated: true, completion: nil)
    }

    // Show error alert (e.g., empty text field)
    func showErrorAlert(message: String) {
        let alertController = UIAlertController(title: "Error", message: message, preferredStyle: .alert)
        alertController.addAction(UIAlertAction(title: "Okay", style: .default, handler: nil))
        self.present(alertController, animated: true, completion: nil)
    }

    // Show mission complete alert
    func showMissionCompleteAlert() {
        let alertController = UIAlertController(title: "Mission Complete!", message: "You've successfully completed all levels.", preferredStyle: .alert)
        alertController.addAction(UIAlertAction(title: "Play Again", style: .default, handler: { _ in
            self.resetGame()
        }))
        self.present(alertController, animated: true, completion: nil)
    }

    // Reset game after completing all levels
    func resetGame() {
        currentLevel = 0
        totalAttempts = 0
        startNewLevel()
    }
}