import UIKit

final class CustomTabBarController: AnimatedTabBarController {

 // MARK: - Override

 override func configure() {
 
 		// set selected index
   selectedIndex = 2 
   tabBar.replaceView.selectedIndex = selectedIndex
   
   	// configure items
   let items = HightLightableTabBarModel.prepareItems()
   configureFor(items)

   	// modify appearence
   tabBar.replaceView.contentContainerShadowColor = UIColor.lightGray
   tabBar.replaceView.contentContainerShadowOpacity = 0.2
   tabBar.replaceView.contentContainerCornerRadius = 18

   tabBar.replaceView.gradientColors = [
     UIColor.white,
     UIColor.white,
     UIColor.gray
   ]
 }
}

/*
Represent model for tabBar item

- Tag: 1000
- Version: 0.1
*/
public protocol AnimatedTabBarItemModel {

 /// unique identifier of model
 var identifier: String { get }

 /// return view for model, descibed as AnimatedTabBarItemRepresentable, should be inherited from UIView
 var viewRepresentation: AnimatedTabBarItemRepresentable { get }

 /// describe size of item when selected
 var selectedComponentWidth: CGFloat { get }

 /// action which will be triggered when item selected
 var action: ((AnimatedTabBarItemModel) -> ())? { get set }
}

/*
View that represent object for tabBar button

- Tag: 1001
- Version: 0.1
*/
public protocol AnimatedTabBarItemRepresentable where Self: UIView {

 /// This function called when view is ready to be displayed but not configured yet
 ///  - Parameter item: item that contains current settings for button replacement see [AnimatedTabBarItemModel](x-source-tag://1000)
 func configure(item: AnimatedTabBarItemModel)

 /// This function triggered when user select/deselect tabBar item
 ///  - Parameter selected: indicate current selection state
 ///  - Parameter item: item that contains current settings for button replacement see [AnimatedTabBarItemModel](x-source-tag://1000)
 func switchToSelectedState(_ selected: Bool, item: AnimatedTabBarItemModel)
}

// if you don't create subclass of tabBarController - in very first controller that used in tabBar do next

class ViewController: UIViewController {

 override func viewDidLoad() {
   super.viewDidLoad()

    // find `AnimatedTabBarController `
   if let tabBarController = self.tabBarController as? AnimatedTabBarController {
   // create items for controller
     let items = ExpandableTabItemModel.prepareItems()
   // set items to controller
     tabBarController.configureFor(items)
   }
   
   // some other setup
 }
}

// if you create subclass of `AnimatedTabBarController`, that perform this configuration in subclass
final class CustomTabBarController: AnimatedTabBarController {

 // MARK: - Override

 override func configure() {
   let items = HightLightableTabBarModel.prepareItems()
   configureFor(items)

   // any other config - check samples for more
 }
}