/*

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

See LICENSE.txt for this sample’s licensing information

Abstract:

An extension that returns information about photos contained in view controllers.

*/

import UIKit

/*

    This extension is specific to this application. Some of the specific view

    controllers in the app override these to return the values that make sense for

    them.

*/

extension UIViewController {

    /*

        Returns the photo currently being displayed by the receiver, or `nil` if the

        receiver is not displaying a photo.

    */

    func containedPhoto() -> Photo? {

        // By default, view controllers don't contain photos.

        return nil

    }

    func containsPhoto(_ photo: Photo) -> Bool {

        // By default, view controllers don't contain photos.

        return false

    }

    func currentVisibleDetailPhotoWithSender(_ sender: AnyObject?) -> Photo? {

        // Look for a view controller that has a visible photo.

        if let target = targetViewController(forAction: #selector(UIViewController.currentVisibleDetailPhotoWithSender(_:)), sender: sender) {

            return target.currentVisibleDetailPhotoWithSender(sender)

        }

        else {

            return nil

        }

    }

}

extension UISplitViewController {

    override func currentVisibleDetailPhotoWithSender(_ sender: AnyObject?) -> Photo? {

        if isCollapsed {

            // If we're collapsed, we don't have a detail.

            return nil

        }

        else {

            // Otherwise, return our detail controller's contained photo (if any).

            let controller = viewControllers.last

            return controller?.containedPhoto()

        }

    }

}