Implemented the NavigationRouter router.

Apps/Locations/Libraries/Sources/Core/Routers/NavigationRouter.swift

@@ -0,0 +1,105 @@
+//
+//  NavigationRouter.swift
+//  Core
+//
+//  Created by Javier Cicchelli on 11/04/2023.
+//  Copyright © 2023 Röck+Cöde. All rights reserved.
+//
+
+import UIKit
+
+/// This class is responsible for presenting view controllers, as it is a concrete implementation of the `Router` protocol, but it won't know what view controller or which view controller is next.
+public class NavigationRouter: NSObject {
+    
+    // MARK: Properties
+    
+    /// A navigation controller to use within this concrete router.
+    private let navigationController: UINavigationController
+
+    /// A root view controller coming in from the navigation controller, if any.
+    private let rootViewController: UIViewController?
+    
+    /// Dictionary that persist `onDismiss` closure for its respective view controllers until one of the later is dismissed.
+    private var onDismissForViewController: [UIViewController: Router.OnDismissedClosure] = [:]
+
+    // MARK: Initialisers
+    
+    /// Initialise this router.
+    /// - Parameter navigationController: A `UINavigationController` navigation controller instance to use in this router.
+    public init(navigationController: UINavigationController) {
+        self.navigationController = navigationController
+        self.rootViewController = navigationController.viewControllers.first
+        
+        super.init()
+        
+        self.navigationController.delegate = self
+    }
+
+}
+
+// MARK: - Router
+
+extension NavigationRouter: Router {
+    
+    // MARK: Functions
+    
+    public func present(
+        _ viewController: UIViewController,
+        animated: Bool,
+        onDismiss: OnDismissedClosure?
+    ) {
+        onDismissForViewController[viewController] = onDismiss
+        
+        navigationController.pushViewController(viewController, animated: animated)
+    }
+    
+    public func dismiss(animated: Bool) {
+        guard let rootViewController else {
+            navigationController.popViewController(animated: animated)
+            return
+        }
+        
+        performOnDismissed(for: rootViewController)
+        
+        navigationController.popToViewController(rootViewController, animated: animated)
+    }
+    
+}
+
+// MARK: - UINavigationControllerDelegate
+
+extension NavigationRouter: UINavigationControllerDelegate {
+    
+    // MARK: Functions
+    
+    public func navigationController(
+        _ navigationController: UINavigationController,
+        didShow viewController: UIViewController,
+        animated: Bool
+    ) {
+        guard let dismissedViewController = navigationController.transitionCoordinator?.viewController(forKey: .from) else {
+            return
+        }
+        
+        performOnDismissed(for: dismissedViewController)
+    }
+
+}
+
+// MARK: - Helpers
+
+private extension NavigationRouter {
+    
+    // MARK: Functions
+    
+    func performOnDismissed(for viewController: UIViewController) {
+        guard let onDismiss = onDismissForViewController[viewController] else {
+            return
+        }
+        
+        onDismiss()
+        
+        onDismissForViewController[viewController] = nil
+    }
+
+}