import UIKit
import PlaygroundSupport

class ViewController: UIViewController {

    private var scrollView: UIScrollView!
    private var textField: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()

        scrollView = UIScrollView()
        scrollView.backgroundColor = .gray
        scrollView.alwaysBounceVertical = true
        scrollView.keyboardDismissMode = .interactive
        view.addSubview(scrollView)
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        scrollView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
        scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true

        textField = UITextField()
        textField.backgroundColor = .white
        textField.delegate = self
        scrollView.addSubview(textField)
        textField.translatesAutoresizingMaskIntoConstraints = false
        textField.topAnchor.constraint(equalTo: scrollView.topAnchor, constant: view.bounds.height - 100).isActive = true
        textField.widthAnchor.constraint(equalTo: scrollView.widthAnchor).isActive = true

        NotificationCenter.default.addObserver(self,
                                               selector: #selector(keyboardWillShow),
                                               name: .UIKeyboardWillShow,
                                               object: nil)
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(keyboardWillHide),
                                               name: .UIKeyboardWillHide,
                                               object: nil)
    }

    @objc private func keyboardWillShow(notification: Notification) {
        guard let keyboardFrame = notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as? CGRect else { return }
        let offset = textField.frame.maxY - keyboardFrame.minY
        if offset > 0 {
            scrollView.contentOffset.y = offset
        }
    }

    @objc private func keyboardWillHide(notification: Notification) {
        scrollView.contentOffset.y = -scrollView.safeAreaInsets.top
    }
}

extension ViewController: UITextFieldDelegate {
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        textField.resignFirstResponder()
        return true
    }
}

let viewController = ViewController()
let window = UIWindow(frame: CGRect(x: 0, y: 0, width: 768, height: 1024))
window.rootViewController = viewController
window.makeKeyAndVisible()

PlaygroundPage.current.needsIndefiniteExecution = true
PlaygroundPage.current.liveView = window