/*

     File: RootViewController.m

 Abstract: The primary root view controller for the iPhone.

  Version: 1.6

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 */

#import "RootViewController.h"

#import "MyViewController.h"

static NSString *kNameKey = @"nameKey";

static NSString *kImageKey = @"imageKey";

@interface RootViewController ()

@property (nonatomic, strong) IBOutlet UIScrollView *scrollView;

@property (nonatomic, strong) IBOutlet UIPageControl *pageControl;

@property (nonatomic, strong) NSMutableArray *viewControllers;

@end

#pragma mark -

@implementation RootViewController

- (void)viewDidLoad

{

    [super viewDidLoad];

    NSUInteger numberPages = self.contentList.count;

    // view controllers are created lazily

    // in the meantime, load the array with placeholders which will be replaced on demand

    NSMutableArray *controllers = [[NSMutableArray alloc] init];

    for (NSUInteger i = 0; i < numberPages; i++)

    {

        [controllers addObject:[NSNull null]];

    }

    self.viewControllers = controllers;

    // a page is the width of the scroll view

    self.scrollView.pagingEnabled = YES;

    self.scrollView.contentSize =

        CGSizeMake(CGRectGetWidth(self.scrollView.frame) * numberPages, CGRectGetHeight(self.scrollView.frame));

    self.scrollView.showsHorizontalScrollIndicator = NO;

    self.scrollView.showsVerticalScrollIndicator = NO;

    self.scrollView.scrollsToTop = NO;

    self.scrollView.delegate = self;

    self.pageControl.numberOfPages = numberPages;

    self.pageControl.currentPage = 0;

    // pages are created on demand

    // load the visible page

    // load the page on either side to avoid flashes when the user starts scrolling

    //

    [self loadScrollViewWithPage:0];

    [self loadScrollViewWithPage:1];

}

- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation

{

    // remove all the subviews from our scrollview

    for (UIView *view in self.scrollView.subviews)

    {

        [view removeFromSuperview];

    }

    NSUInteger numPages = self.contentList.count;

    // adjust the contentSize (larger or smaller) depending on the orientation

    self.scrollView.contentSize =

        CGSizeMake(CGRectGetWidth(self.scrollView.frame) * numPages, CGRectGetHeight(self.scrollView.frame));

    // clear out and reload our pages

    self.viewControllers = nil;

    NSMutableArray *controllers = [[NSMutableArray alloc] init];

    for (NSUInteger i = 0; i < numPages; i++)

    {

        [controllers addObject:[NSNull null]];

    }

    self.viewControllers = controllers;

    [self loadScrollViewWithPage:self.pageControl.currentPage - 1];

    [self loadScrollViewWithPage:self.pageControl.currentPage];

    [self loadScrollViewWithPage:self.pageControl.currentPage + 1];

    [self gotoPage:NO]; // remain at the same page (don't animate)

}

- (void)loadScrollViewWithPage:(NSUInteger)page

{

    if (page >= self.contentList.count)

        return;

    // replace the placeholder if necessary

    MyViewController *controller = [self.viewControllers objectAtIndex:page];

    if ((NSNull *)controller == [NSNull null])

    {

        controller = [[MyViewController alloc] initWithPageNumber:page];

        [self.viewControllers replaceObjectAtIndex:page withObject:controller];

    }

    // add the controller's view to the scroll view

    if (controller.view.superview == nil)

    {

        CGRect frame = self.scrollView.frame;

        frame.origin.x = CGRectGetWidth(frame) * page;

        frame.origin.y = 0;

        controller.view.frame = frame;

        [self addChildViewController:controller];

        [self.scrollView addSubview:controller.view];

        [controller didMoveToParentViewController:self];

        NSDictionary *numberItem = [self.contentList objectAtIndex:page];

        controller.numberImage.image = [UIImage imageNamed:[numberItem valueForKey:kImageKey]];

        controller.numberTitle.text = [numberItem valueForKey:kNameKey];

    }

}

// at the end of scroll animation, reset the boolean used when scrolls originate from the UIPageControl

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView

{

    // switch the indicator when more than 50% of the previous/next page is visible

    CGFloat pageWidth = CGRectGetWidth(self.scrollView.frame);

    NSUInteger page = floor((self.scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;

    self.pageControl.currentPage = page;

    // load the visible page and the page on either side of it (to avoid flashes when the user starts scrolling)

    [self loadScrollViewWithPage:page - 1];

    [self loadScrollViewWithPage:page];

    [self loadScrollViewWithPage:page + 1];

    // a possible optimization would be to unload the views+controllers which are no longer visible

}

- (void)gotoPage:(BOOL)animated

{

    NSInteger page = self.pageControl.currentPage;

    // load the visible page and the page on either side of it (to avoid flashes when the user starts scrolling)

    [self loadScrollViewWithPage:page - 1];

    [self loadScrollViewWithPage:page];

    [self loadScrollViewWithPage:page + 1];

    // update the scroll view to the appropriate page

    CGRect bounds = self.scrollView.bounds;

    bounds.origin.x = CGRectGetWidth(bounds) * page;

    bounds.origin.y = 0;

    [self.scrollView scrollRectToVisible:bounds animated:animated];

}

- (IBAction)changePage:(id)sender

{

    [self gotoPage:YES];    // YES = animate

}

@end