/*

 Copyright (C) 2017 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 Demonstrates applying a custom background to a navigation bar.

 */

import UIKit

class CustomAppearanceViewController: UITableViewController {

    @IBOutlet var backgroundSwitcher: UISegmentedControl!

    /// Our data source is an array of city names, populated from Cities.json.

    let dataSource = CitiesDataSource()

    override func viewDidLoad() {

        super.viewDidLoad()

        tableView.dataSource = dataSource

        // Place the background switcher in the toolbar.

        let backgroundSwitcherItem = UIBarButtonItem(customView: backgroundSwitcher)

        toolbarItems = [

            UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil),

            backgroundSwitcherItem,

            UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)

        ]

        applyImageBackgroundToTheNavigationBar()

    }

    /**

     *  Configures the navigation bar to use an image as its background.

     */

    func applyImageBackgroundToTheNavigationBar() {

        // These background images contain a small pattern which is displayed

        // in the lower right corner of the navigation bar.

        var backgroundImageForDefaultBarMetrics = #imageLiteral(resourceName: "NavigationBarDefault")

        var backgroundImageForLandscapePhoneBarMetrics = #imageLiteral(resourceName: "NavigationBarLandscapePhone")

        // Both of the above images are smaller than the navigation bar's

        // size.  To enable the images to resize gracefully while keeping their

        // content pinned to the bottom right corner of the bar, the images are

        // converted into resizable images width edge insets extending from the

        // bottom up to the second row of pixels from the top, and from the

        // right over to the second column of pixels from the left.  This results

        // in the topmost and leftmost pixels being stretched when the images

        // are resized.  Not coincidentally, the pixels in these rows/columns

        // are empty.

        backgroundImageForDefaultBarMetrics =

            backgroundImageForDefaultBarMetrics.resizableImage(withCapInsets: UIEdgeInsets(top: 0,

                                                                                           left: 0,

                                                                                           bottom: backgroundImageForDefaultBarMetrics.size.height - 1,

                                                                                           right: backgroundImageForDefaultBarMetrics.size.width - 1))

        backgroundImageForLandscapePhoneBarMetrics =

            backgroundImageForLandscapePhoneBarMetrics.resizableImage(withCapInsets: UIEdgeInsets(top: 0,

                                                                                                  left: 0,

                                                                                                  bottom: backgroundImageForLandscapePhoneBarMetrics.size.height - 1,

                                                                                                  right: backgroundImageForLandscapePhoneBarMetrics.size.width - 1))

        // You should use the appearance proxy to customize the appearance of

        // UIKit elements.  However changes made to an element's appearance

        // proxy do not effect any existing instances of that element currently

        // in the view hierarchy.  Normally this is not an issue because you

        // will likely be performing your appearance customizations in

        // -application:didFinishLaunchingWithOptions:.  However, this example

        // allows you to toggle between appearances at runtime which necessitates

        // applying appearance customizations directly to the navigation bar.

        /* let navigationBarAppearance = UINavigationBar.appearance(whenContainedInInstancesOf: [UINavigationController.self]) */

        let navigationBarAppearance = self.navigationController!.navigationBar

        // The bar metrics associated with a background image determine when it

        // is used.  The background image associated with the Default bar metrics

        // is used when a more suitable background image can not be found.

        navigationBarAppearance.setBackgroundImage(backgroundImageForDefaultBarMetrics, for: .default)

        // The background image associated with the LandscapePhone bar metrics

        // is used by the shorter variant of the navigation bar that is used on

        // iPhone when in landscape.

        navigationBarAppearance.setBackgroundImage(backgroundImageForLandscapePhoneBarMetrics, for: .compact)

    }

    /**

     *  Configures the navigation bar to use a transparent background (see-through

     *  but without any blur).

     */

    func applyTransparentBackgroundToTheNavigationBar(_ opacity: CGFloat) {

        var transparentBackground: UIImage

        // The background of a navigation bar switches from being translucent

        // to transparent when a background image is applied.  The intensity of

        // the background image's alpha channel is inversely related to the

        // transparency of the bar.  That is, a smaller alpha channel intensity

        // results in a more transparent bar and vis-versa.

        //

        // Below, a background image is dynamically generated with the desired

        // opacity.

        UIGraphicsBeginImageContextWithOptions(CGSize(width: 1, height: 1),

                                               false,

                                               navigationController!.navigationBar.layer.contentsScale)

        let context = UIGraphicsGetCurrentContext()!

        context.setFillColor(red: 1, green: 1, blue: 1, alpha: opacity)

        UIRectFill(CGRect(x: 0, y: 0, width: 1, height: 1))

        transparentBackground = UIGraphicsGetImageFromCurrentImageContext()!

        UIGraphicsEndImageContext()

        // You should use the appearance proxy to customize the appearance of

        // UIKit elements.  However changes made to an element's appearance

        // proxy do not effect any existing instances of that element currently

        // in the view hierarchy.  Normally this is not an issue because you

        // will likely be performing your appearance customizations in

        // -application:didFinishLaunchingWithOptions:.  However, this example

        // allows you to toggle between appearances at runtime which necessitates

        // applying appearance customizations directly to the navigation bar.

        /* let navigationBarAppearance = UINavigationBar.appearance(whenContainedInInstancesOf: [UINavigationController.self]) */

        let navigationBarAppearance = self.navigationController!.navigationBar

        navigationBarAppearance.setBackgroundImage(transparentBackground, for: .default)

    }

    /**

     *  Configures the navigation bar to use a custom color as its background.

     *  The navigation bar remains translucent.

     */

    func applyBarTintColorToTheNavigationBar() {

        // Be aware when selecting a barTintColor for a translucent bar that

        // the tint color will be blended with the content passing under

        // the translucent bar.  See QA1808 for more information.

        // <https://developer.apple.com/library/ios/qa/qa1808/_index.html>

        let barTintColor =

            UIColor(red: 176.0/255.0, green: 226.0/255.0, blue: 172.0/255.0, alpha: 1)

        let darkendBarTintColor =

            UIColor(red: 176.0/255.0 - 0.05, green: 226.0/255.0 - 0.02, blue: 172.0/255.0 - 0.05, alpha: 1)

        // You should use the appearance proxy to customize the appearance of

        // UIKit elements.  However changes made to an element's appearance

        // proxy do not effect any existing instances of that element currently

        // in the view hierarchy.  Normally this is not an issue because you

        // will likely be performing your appearance customizations in

        // -application:didFinishLaunchingWithOptions:.  However, this example

        // allows you to toggle between appearances at runtime which necessitates

        // applying appearance customizations directly to the navigation bar.

        /* let navigationBarAppearance = UINavigationBar.appearance(whenContainedInInstancesOf: [UINavigationController.self]) */

        let navigationBarAppearance = self.navigationController!.navigationBar

        navigationBarAppearance.barTintColor = darkendBarTintColor

        // For comparison, apply the same barTintColor to the toolbar, which

        // has been configured to be opaque.

        navigationController!.toolbar.barTintColor = barTintColor

        navigationController!.toolbar.isTranslucent = false

    }

    // MARK: - UIContentContainer

    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {

        super.viewWillTransition(to: size, with: coordinator)

        // This works around a bug in iOS 8.0 - 8.2 in which the navigation bar

        // will not display the correct background image after rotating the device.

        // This bug affects bars in navigation controllers that are presented

        // modally. A bar in the window's rootViewController would not be affected.

        coordinator.animate(alongsideTransition: { context in

            // The workaround is to toggle some appearance related setting on the

            // navigation bar when we detect that the view controller has changed

            // interface orientations.  In our example, we call the

            // -configureNewNavBarBackground: which reapplies our appearance

            // based on the current selection.  In a real app, changing just the

            // barTintColor or barStyle would have the same effect.

            self.configureNewNavBarBackground(self.backgroundSwitcher)

        }, completion: nil)

    }

    // MARK: - Background Switcher

    @IBAction func configureNewNavBarBackground(_ sender: UISegmentedControl) {

        // Reset everything.

        self.navigationController!.navigationBar.setBackgroundImage(nil, for: .default)

        self.navigationController!.navigationBar.setBackgroundImage(nil, for: .compact)

        self.navigationController!.navigationBar.barTintColor = nil

        self.navigationController!.toolbar.barTintColor = nil

        self.navigationController!.toolbar.isTranslucent = true

        switch sender.selectedSegmentIndex {

        case 0: // Transparent Background

            applyImageBackgroundToTheNavigationBar()

        case 1: // Transparent

            applyTransparentBackgroundToTheNavigationBar(0.87)

        case 2: // Colored

            applyBarTintColorToTheNavigationBar()

        default:

            break

        }

    }

    // MARK: - UITableViewDelegate

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

        if navigationItem.prompt == dataSource.city(index: indexPath.row) {

            navigationItem.prompt = nil

            tableView.deselectRow(at: indexPath, animated: true)

        }

        else {

            navigationItem.prompt = dataSource.city(index: indexPath.row)

        }

    }

}