import UIKit

class TourViewController: UIViewController, UIPageViewControllerDataSource {
    private var pageViewController: UIPageViewController?

    @IBOutlet var pageViewer: UIView!
    // Initialize it right away here
    private let contentImages = ["real-pixels.png",
        "real-pixels.png",
        "real-pixels.png"]

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        createPageViewController()
        setupPageControl()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    private func createPageViewController() {

        let pageController = self.storyboard!.instantiateViewControllerWithIdentifier("PageController") as! UIPageViewController
        pageController.dataSource = self

        if contentImages.count > 0 {
            let firstController = getItemController(0)!
            let startingViewControllers: NSArray = [firstController]
            pageController.setViewControllers(startingViewControllers as! [UIViewController], direction: UIPageViewControllerNavigationDirection.Forward, animated: false, completion: nil)
        }

        pageViewController = pageController
        addChildViewController(pageViewController!)
        self.view.addSubview(pageViewController!.view)
        pageViewController!.didMoveToParentViewController(self)
    }

    private func setupPageControl() {
        let appearance = UIPageControl.appearance()
        appearance.pageIndicatorTintColor = UIColor.grayColor()
        appearance.currentPageIndicatorTintColor = UIColor.whiteColor()
        appearance.backgroundColor = UIColor.darkGrayColor()
    }

    // MARK: - UIPageViewControllerDataSource

    func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? {

        let itemController = viewController as! ContentViewController

        if itemController.itemIndex > 0 {
            return getItemController(itemController.itemIndex-1)
        }

        return nil
    }

    func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {

        let itemController = viewController as! ContentViewController

        if itemController.itemIndex+1 < contentImages.count {
            return getItemController(itemController.itemIndex+1)
        }

        return nil
    }

    private func getItemController(itemIndex: Int) -> ContentViewController? {

        if itemIndex < contentImages.count {
            let pageItemController = self.storyboard!.instantiateViewControllerWithIdentifier("ContentController") as! ContentViewController
            pageItemController.itemIndex = itemIndex
            pageItemController.imageName = contentImages[itemIndex]
            return pageItemController
        }

        return nil
    }

    // MARK: - Page Indicator

    func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int {
        return contentImages.count
    }

    func presentationIndexForPageViewController(pageViewController: UIPageViewController) -> Int {
        return 0
    }

}