//
// No comments for you. 
// It was hard to write,
// so it should be hard to read.
//
// @author Mathias af Jochnick
// @created on 2025-10-29

import UIKit

class ViewController: UIViewController {
    
    var view1: UIView!
    var view2: UIView!
    var currentView: UIView!
    var button1: UIButton!
    var button2: UIButton!
    var tableView: UITableView!
    var gradientLayer: CAGradientLayer!
    var label1: UILabel!
    var label2: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
        
        setupViews()
        setupView1()
        setupView2()
        
        currentView = view1
        view.addSubview(view1)
    }
    
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        view1.frame = view.bounds
        view2.frame = view.bounds
        gradientLayer.frame = view2.bounds
    }
    
    func setupViews() {
        view1 = UIView()
        view2 = UIView()
        
        view1.backgroundColor = .systemBackground
        view2.backgroundColor = .systemBackground
        
        view1.frame = view.bounds
        view2.frame = view.bounds
    }
    
    func setupView1() {
        tableView = UITableView()
        tableView.delegate = self
        tableView.dataSource = self
        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "Cell")
        tableView.translatesAutoresizingMaskIntoConstraints = false
        view1.addSubview(tableView)
        
        button1 = UIButton(type: .system)
        button1.setTitle("Flip to View 2", for: .normal)
        button1.titleLabel?.font = .systemFont(ofSize: 20)
        button1.backgroundColor = .systemBlue
        button1.setTitleColor(.white, for: .normal)
        button1.layer.cornerRadius = 8
        button1.addTarget(self, action: #selector(flipToView2), for: .touchUpInside)
        button1.translatesAutoresizingMaskIntoConstraints = false
        view1.addSubview(button1)
        
        NSLayoutConstraint.activate([
            tableView.topAnchor.constraint(equalTo: view1.safeAreaLayoutGuide.topAnchor),
            tableView.leadingAnchor.constraint(equalTo: view1.leadingAnchor),
            tableView.trailingAnchor.constraint(equalTo: view1.trailingAnchor),
            tableView.bottomAnchor.constraint(equalTo: button1.topAnchor, constant: -20),
            
            button1.leadingAnchor.constraint(equalTo: view1.leadingAnchor, constant: 20),
            button1.trailingAnchor.constraint(equalTo: view1.trailingAnchor, constant: -20),
            button1.bottomAnchor.constraint(equalTo: view1.safeAreaLayoutGuide.bottomAnchor, constant: -20),
            button1.heightAnchor.constraint(equalToConstant: 50)
        ])
    }
    
    func setupView2() {
        gradientLayer = CAGradientLayer()
        gradientLayer.colors = [
            UIColor.systemPurple.cgColor,
            UIColor.systemPink.cgColor,
            UIColor.systemOrange.cgColor
        ]
        gradientLayer.locations = [0.0, 0.5, 1.0]
        gradientLayer.startPoint = CGPoint(x: 0, y: 0)
        gradientLayer.endPoint = CGPoint(x: 1, y: 1)
        view2.layer.insertSublayer(gradientLayer, at: 0)
        
        label1 = UILabel()
        label1.text = "Gradient View"
        label1.font = .boldSystemFont(ofSize: 32)
        label1.textColor = .white
        label1.textAlignment = .center
        label1.translatesAutoresizingMaskIntoConstraints = false
        view2.addSubview(label1)
        
        label2 = UILabel()
        label2.text = "This is some sample text to see if the flip animation is centered properly"
        label2.font = .systemFont(ofSize: 18)
        label2.textColor = .white
        label2.textAlignment = .center
        label2.numberOfLines = 0
        label2.translatesAutoresizingMaskIntoConstraints = false
        view2.addSubview(label2)
        
        button2 = UIButton(type: .system)
        button2.setTitle("Flip to View 1", for: .normal)
        button2.titleLabel?.font = .systemFont(ofSize: 20)
        button2.backgroundColor = .systemGreen
        button2.setTitleColor(.white, for: .normal)
        button2.layer.cornerRadius = 8
        button2.addTarget(self, action: #selector(flipToView1), for: .touchUpInside)
        button2.translatesAutoresizingMaskIntoConstraints = false
        view2.addSubview(button2)
        
        NSLayoutConstraint.activate([
            label1.centerXAnchor.constraint(equalTo: view2.centerXAnchor),
            label1.centerYAnchor.constraint(equalTo: view2.centerYAnchor, constant: -60),
            
            label2.centerXAnchor.constraint(equalTo: view2.centerXAnchor),
            label2.topAnchor.constraint(equalTo: label1.bottomAnchor, constant: 30),
            label2.leadingAnchor.constraint(equalTo: view2.leadingAnchor, constant: 40),
            label2.trailingAnchor.constraint(equalTo: view2.trailingAnchor, constant: -40),
            
            button2.leadingAnchor.constraint(equalTo: view2.leadingAnchor, constant: 20),
            button2.trailingAnchor.constraint(equalTo: view2.trailingAnchor, constant: -20),
            button2.bottomAnchor.constraint(equalTo: view2.safeAreaLayoutGuide.bottomAnchor, constant: -20),
            button2.heightAnchor.constraint(equalToConstant: 50)
        ])
    }
    
    @objc func flipToView2() {
        view.addSubview(view2)
        UIView.transition(from: currentView,
                         to: view2,
                         duration: 0.5,
                         options: .transitionFlipFromRight,
                         completion: nil)
        currentView = view2
    }
    
    @objc func flipToView1() {
        view.addSubview(view1)
        UIView.transition(from: currentView,
                         to: view1,
                         duration: 0.5,
                         options: .transitionFlipFromRight,
                         completion: nil)
        currentView = view1
    }
}

extension ViewController: UITableViewDelegate, UITableViewDataSource {
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 50
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
        cell.textLabel?.text = "Row \(indexPath.row + 1): Lorem ipsum dolor sit amet, consectetur adipiscing elit"
        cell.textLabel?.numberOfLines = 0
        return cell
    }
}