import UIKit
import XCTest

/// Loads a ViewController to be tested
final class ViewControllerTestingLoader<T: UIViewController> {

    // MARK: - Private Properties

    private var rootWindow: UIWindow!

    // MARK: - Public Functions

    /// Sets up a viewController to be loader
    ///
    /// - Parameter viewController: the controller to be loaded
    func setup(withViewController viewController: T) {
        rootWindow = UIWindow(frame: UIScreen.main.bounds)
        rootWindow.isHidden = false
        rootWindow.rootViewController = viewController
        _ = viewController.view
        viewController.viewWillAppear(false)
        viewController.viewDidAppear(false)
    }

    /// Removes the controller from the window hierachy
    func tearDown() {
        guard let rootWindow = rootWindow,
            let rootViewController = rootWindow.rootViewController as? T else {
                XCTFail("tearDown() was called without setup() being called first")
                return
        }
        rootViewController.viewWillDisappear(false)
        rootViewController.viewDidDisappear(false)
        rootWindow.rootViewController = nil
        rootWindow.isHidden = true
        self.rootWindow = nil
    }

    /*********************/
    /****** EXAMPLE ******/
    /*********************/
    /*

     final class MyTest: XCTestCase {

         private var sut: MyController!
         private var viewControllerTestingLoader: ViewControllerTestingLoader<MyController>!

         override func setUp() {
             super.setUp()
             let controller = MyController()
             sut = controller
             viewControllerTestingLoader = ViewControllerTestingLoader<MyController>()
             viewControllerTestingLoader.setup(withViewController: sut)
         }

         override func tearDown() {
             sut = nil
             viewControllerTestingLoader.tearDown()
             viewControllerTestingLoader = nil
             super.tearDown()
         }

     }

     */

}