/*

Copyright (C) 2016 Apple Inc. All Rights Reserved.

See LICENSE.txt for this sample’s licensing information

Abstract:

The application delegate and split view controller delegate.

*/

import UIKit

@UIApplicationMain

class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

        // Load the conversations from disk and create our root model object.

        let user: User

        if let url = Bundle.main.url(forResource: "User", withExtension: "plist"),

            let userDictionary = NSDictionary(contentsOf: url) as? [String: AnyObject],

            let loadedUser = User(dictionary: userDictionary) {

                user = loadedUser

        }

        else {

            user = User()

        }

        let window = UIWindow()

        self.window = window

        let splitViewController = UISplitViewController()

        splitViewController.delegate = self

        splitViewController.preferredDisplayMode = .allVisible

        let userListTableViewController = ListTableViewController(user: user)

        let primaryViewController = UINavigationController(rootViewController: userListTableViewController)

        let secondaryViewController = EmptyViewController()

        splitViewController.viewControllers = [primaryViewController, secondaryViewController]

        window.rootViewController = splitViewController

        window.makeKeyAndVisible()

        return true

    }

}

extension AppDelegate: UISplitViewControllerDelegate {

    // Collapse the secondary view controller onto the primary view controller.

    func splitViewController(_ splitViewController: UISplitViewController, collapseSecondary secondaryViewController: UIViewController, onto primaryViewController: UIViewController) -> Bool {

        /*

            The secondary view is not showing a photo. Return true to tell the

            splitViewController to use its default behavior: just hide the

            secondaryViewController and show the primaryViewController.

        */

        guard let photo = secondaryViewController.containedPhoto() else { return true }

        /*

            The secondary view is showing a photo. Set the primary navigation

            controller to contain a path of view controllers that lead to that photo.

        */

        if let primaryNavController = primaryViewController as? UINavigationController {

            let viewControllersLeadingToPhoto = primaryNavController.viewControllers.filter { $0.containsPhoto(photo) }

            primaryNavController.viewControllers = viewControllersLeadingToPhoto

        }

        /*

            We handled the collapse. Return false to tell the splitViewController

            not to do anything else.

        */

        return false

    }

    // Separate the secondary view controller from the primary view controller.

    func splitViewController(_ splitViewController: UISplitViewController, separateSecondaryFrom primaryViewController: UIViewController) -> UIViewController? {

        if let primaryNavController = primaryViewController as? UINavigationController {

            /*

                One of the view controllers in the navigation stack is showing a

                photo. Return nil to tell the splitViewController to use its

                default behavior: show the secondary view controller that was

                present when it collapsed.

            */

            let anyViewControllerContainsPhoto = primaryNavController.viewControllers.contains { controller in

                return controller.containedPhoto() != nil

            }

            if anyViewControllerContainsPhoto {

                return nil

            }

        }

        /*

            None of the view controllers in the navigation stack contained a photo,

            so show a new empty view controller as the secondary.

        */

        return EmptyViewController()

    }

}