/*

 Copyright (C) 2018 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 A custom container view controller that is functionally similar to a 

  UINavigationController.

 */

#import "QuizContainerViewController.h"

#import "QuizContainerFadeViewControllerSegue.h"

@import QuartzCore;

@interface QuizContainerViewController () <UINavigationBarDelegate> {

    UINavigationBar *_navigationBar;

    NSArray *_viewControllers;

}

@end

@implementation QuizContainerViewController

//| ----------------------------------------------------------------------------

//  We provide our own view.

//

- (void)loadView

{

    self.view = [[UIView alloc] init];

    _navigationBar = [[UINavigationBar alloc] init];

    _navigationBar.delegate = self;

    [self.view addSubview:_navigationBar];

}

//| ----------------------------------------------------------------------------

- (void)viewDidLoad

{

    [super viewDidLoad];

    // The transition animation involves fading out the outgoing view

    // controller's view while fading in the incoming view controller's view.

    // This creates a short 'flash' animation where the color of the flash is 

    // our view's backgroundColor.

    self.view.backgroundColor = [UIColor whiteColor];

    // This segue creates our initial root view controller.  Users of this

    // class are expected to define a segue named 'RootViewController' with

    // segue type QuizContainerRootViewControllerSegue.  The destination

    // of this segue should be the scene of the desired initial root view

    // controller.

    [self performSegueWithIdentifier:@"RootViewController" sender:self];

}

//| ----------------------------------------------------------------------------

//! Returns the appropriate frame for displaying a child view controller.

//

- (CGRect)frameForTopViewController

{

    return CGRectMake(0,

                      _navigationBar.frame.size.height + _navigationBar.frame.origin.y,

                      self.view.bounds.size.width,

                      self.view.bounds.size.height - _navigationBar.frame.size.height - _navigationBar.frame.origin.y);

}

//| ----------------------------------------------------------------------------

- (void)viewDidLayoutSubviews

{

    [_navigationBar sizeToFit];

    // Offset the navigation bar to account for the status bar.

    CGFloat topLayoutGuide = 0.0f;

    if ([self respondsToSelector:@selector(topLayoutGuide)])

        topLayoutGuide = (self.topLayoutGuide).length;

    _navigationBar.frame = CGRectMake(_navigationBar.frame.origin.x, topLayoutGuide,

                                      _navigationBar.frame.size.width, _navigationBar.frame.size.height);

    self.topViewController.view.frame = [self frameForTopViewController];

}

#pragma mark -

#pragma mark Unwind Segue

//| ----------------------------------------------------------------------------

//! Returns the view controller managed by the receiver that wants to handle

//! the specified unwind action.

//

//  This method is called when either unwind segue is triggered in

//  ResultsViewController.  It is the responsibility of the parent of the

//  view controller that triggered the unwind segue to locate a

//  view controller that responds to the unwind action for the triggered segue.

//  

- (UIViewController *)viewControllerForUnwindSegueAction:(SEL)action fromViewController:(UIViewController *)fromViewController withSender:(id)sender

{

    // Like UINavigationController, search the array of view controllers

    // managed by this container in reverse order.

    for (UIViewController *vc in [_viewControllers reverseObjectEnumerator])

        // Always use -canPerformUnwindSegueAction:fromViewController:withSender:

        // to determine if a view controller wants to handle an unwind action.

        if ([vc canPerformUnwindSegueAction:action fromViewController:fromViewController withSender:sender])

            return vc;

    // Always invoke the super's implementation if no view controller managed

    // by this container wanted to handle the unwind action.

    return [super viewControllerForUnwindSegueAction:action fromViewController:fromViewController withSender:sender];

}

//| ----------------------------------------------------------------------------

//! Returns a segue object for transitioning to toViewController.

//

//  This method is called if the destination of an unwind segue is a child

//  view controller of this container.  This method returns an instance

//  of QuizContainerFadeViewControllerSegue that transitions to the destination

//  view controller of the unwind segue (toViewController).

//

- (UIStoryboardSegue*)segueForUnwindingToViewController:(UIViewController *)toViewController fromViewController:(UIViewController *)fromViewController identifier:(NSString *)identifier

{

    // QuizContainerFadeViewControllerSegue is a UIStoryboardSegue subclass

    // for transitioning between view controllers managed by this container.

    QuizContainerFadeViewControllerSegue *unwindStoryboardSegue = [[QuizContainerFadeViewControllerSegue alloc] initWithIdentifier:identifier source:fromViewController destination:toViewController];

    // Set the unwind property to YES so an unwind animation is performed.

    // Note that this property is custom to QuizContainerFadeViewControllerSegue.

    unwindStoryboardSegue.unwind = YES;

    return unwindStoryboardSegue;

}

#pragma mark -

#pragma mark Actions

//| ----------------------------------------------------------------------------

//! Manual implementation of the topViewController property.

//! Returns the view controller at the top of the navigation stack.

//

- (UIViewController*)topViewController

{

    if (self.viewControllers.count == 0)

        return nil;

    return (self.viewControllers).lastObject;

}

//| ----------------------------------------------------------------------------

//! Equivalent to calling -setViewControllers:animated: and passing NO for the

//! animated argument.

//

- (void)setViewControllers:(NSArray *)viewControllers

{

    [self setViewControllers:viewControllers animated:NO];

}

//| ----------------------------------------------------------------------------

//! Replaces the view controllers currently managed by the receiver with the

//! specified items.

//

//! @param  viewControllers

//!         The view controllers to place in the navigation stack.  The

//!         last item added to the array becomes the top item of the

//!         navigation stack.

//! @param  animated

//!         If YES, animate the pushing or popping of the top view controller.

//!         If NO, replace the view controllers without any animations.

//

//  This is where all of the transition magic happens. 

//

- (void)setViewControllers:(NSArray *)viewControllers animated:(BOOL)animated

{

    // Compare the incoming viewControllers array to the existing navigation

    // stack, seperating the differences into two groups.

    NSArray *viewControllersToRemove = [_viewControllers filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"NOT (SELF IN %@)", viewControllers]];

    NSArray *viewControllersToAdd = [viewControllers filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"NOT (SELF IN %@)", _viewControllers]];

    for (UIViewController *vc in viewControllersToRemove)

        [vc willMoveToParentViewController:nil];

    for (UIViewController *vc in viewControllersToAdd)

        [self addChildViewController:vc];

    void (^finishRemovingViewControllers)(void) = ^() {

        for (UIViewController *vc in viewControllersToRemove)

            [vc removeFromParentViewController];

    };

    void (^finishAddingViewControllers)(void) = ^() {

        for (UIViewController *vc in viewControllersToAdd)

            [vc didMoveToParentViewController:self];

    };

    // The view controller presently at the top of the navigation stack.

    UIViewController *oldTopViewController = (_viewControllers.count) ? _viewControllers.lastObject : nil;

    // The view controller that will be at the stop of the navgation stack.

    UIViewController *newTopViewController = (viewControllers.count) ? viewControllers.lastObject : nil;

    // If the last object in the incoming viewControllers is the

    // already at the top of the current navigation stack then don't 

    // perform any animation as it would be redundant.

    if (oldTopViewController != newTopViewController)

    {

        if (oldTopViewController)

        {

            // Fade animations look wrong unless the root layer of the

            // animation rasterizes itself but be sure to remember the

            // old setting.

            BOOL oldTopViewControllerViewShouldRasterize = oldTopViewController.view.layer.shouldRasterize;

            oldTopViewController.view.layer.shouldRasterize = YES;

            // Fade out the old top view controller of the navigation stack.

            [UIView animateWithDuration:((animated) ? 0.25 : 0) delay:0 options:0 animations:^{

                oldTopViewController.view.alpha = 0.0f;

            } completion:^(BOOL finished) {

                // Restore the old shouldRasterize setting.

                oldTopViewController.view.layer.shouldRasterize = oldTopViewControllerViewShouldRasterize;

                [oldTopViewController.view removeFromSuperview];

                finishRemovingViewControllers();

            }];

        }

        else

            finishRemovingViewControllers();

        if (newTopViewController)

        {

            // Fade animations look wrong unless the root layer of the

            // animation rasterizes itself but be sure to remember the

            // old setting.

            BOOL newTopViewControllerViewShouldRasterize = newTopViewController.view.layer.shouldRasterize;

            newTopViewController.view.layer.shouldRasterize = YES;

            newTopViewController.view.frame = [self frameForTopViewController];

            [self.view addSubview:newTopViewController.view];

            newTopViewController.view.alpha = 0.0f;

            // Fade in the new top view controller of the navigation stack.

            [UIView animateWithDuration:((animated) ? 0.25 : 0) delay:((animated) ? 0.3 : 0) options:0 animations:^{

                newTopViewController.view.alpha = 1.0f;

            } completion:^(BOOL finished) {

                // Restore the old shouldRasterize setting.

                newTopViewController.view.layer.shouldRasterize = newTopViewControllerViewShouldRasterize;

                finishAddingViewControllers();

            }];

        }

        else

            finishAddingViewControllers();

    }

    else

    // No animation required.

    {

        finishRemovingViewControllers();

        finishAddingViewControllers();

    }

    _viewControllers = viewControllers;

    // Update the stack of navigation items for the _navigationBar to

    // reflect the new navigation stack.

    NSMutableArray *newNavigationItemsArray = [NSMutableArray arrayWithCapacity:viewControllers.count];

    for (UIViewController *vc in viewControllers)

        [newNavigationItemsArray addObject:vc.navigationItem];

    [_navigationBar setItems:newNavigationItemsArray animated:animated];

}

//| ----------------------------------------------------------------------------

//! Pushes a view controller onto the receiver’s stack and updates the display.

//

- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated

{

    // Replace the navigation stack with a new array that has viewController

    // apeneded to it.

    [self setViewControllers:[self.viewControllers arrayByAddingObject:viewController] animated:animated];

}

//| ----------------------------------------------------------------------------

//! Pops view controllers until the specified view controller is at the top of the navigation stack.

//

- (NSArray *)popToViewController:(UIViewController *)viewController animated:(BOOL)animated

{

    // Check that viewController is in the navigation stack.

    NSUInteger indexOfViewController = [_viewControllers indexOfObject:viewController];

    if (indexOfViewController == NSNotFound)

        return nil;

    NSArray *viewControllersThatWerePopped = [_viewControllers subarrayWithRange:NSMakeRange(indexOfViewController+1, _viewControllers.count - (indexOfViewController+1))];

    NSArray *newViewControllersArray = [_viewControllers subarrayWithRange:NSMakeRange(0, indexOfViewController+1)];

    // Replace the navigation stack with a new array containg only the view

    // controllers up to the specified viewController.

    [self setViewControllers:newViewControllersArray animated:YES];

    return viewControllersThatWerePopped;

}

@end