Add NavigationRouterStore that enables to get a NavigationRouter from a UINavigationController controller instance.

Podfile

@@ -48,6 +48,7 @@ abstract_target 'RiotPods' do
   pod 'GBDeviceInfo', '~> 6.6.0'
   pod 'Reusable', '~> 4.1'
   pod 'KeychainAccess', '~> 4.2.2'
+  pod 'WeakDictionary', '~> 2.0'
 
   # Piwik for analytics
   pod 'MatomoTracker', '~> 7.4.1'

Riot/Modules/Application/AppCoordinator.swift

@@ -80,6 +80,9 @@ final class AppCoordinator: NSObject, AppCoordinatorType {
         self.setupLogger()
         self.setupTheme()
         
+        // Setup navigation router store
+        _ = NavigationRouterStore.shared
+        
         if BuildSettings.enableSideMenu {
             self.addSideMenu()
         }

Riot/Routers/NavigationRouterStore.swift

@@ -0,0 +1,97 @@
+// 
+// Copyright 2021 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import Foundation
+import WeakDictionary
+
+/// `NavigationRouterStore` enables to get a NavigationRouter from a UINavigationController instance.
+class NavigationRouterStore: NavigationRouterStoreProtocol {
+    
+    // MARK: - Constants
+    
+    static let shared = NavigationRouterStore()
+    
+    // MARK: - Properties
+
+    // FIXME: WeakDictionary does not work with protocol
+    // Find a way to use NavigationRouterType as value
+    private var navigationRouters = WeakDictionary<UINavigationController, NavigationRouter>()
+    
+    // MARK: - Setup
+    
+    /// As we are ensuring that there is only one navigation controller per NavigationRouter, the class here should be used as a singleton.
+    private init() {
+        self.registerNavigationRouterNotifications()
+    }
+    
+    // MARK: - Public
+    
+    func getOrCreateNavigationRouter(for navigationController: UINavigationController) -> NavigationRouterType {
+        
+        if let existingNavigationRouter = self.getNavigationRouter(for: navigationController) {
+            return existingNavigationRouter
+        }
+        
+        let navigationRouter = NavigationRouter(navigationController: RiotNavigationController())
+        return navigationRouter
+    }
+    
+    func getNavigationRouter(for navigationController: UINavigationController) -> NavigationRouterType? {
+        return self.navigationRouters[navigationController]
+    }
+    
+    // MARK: - Private
+    
+    private func removeNavigationRouter(for navigationController: UINavigationController) {
+        self.navigationRouters[navigationController] = nil
+    }
+    
+    private func registerNavigationRouterNotifications() {
+        NotificationCenter.default.addObserver(self, selector: #selector(navigationRouterDidCreate(_:)), name: NavigationRouter.didCreate, object: nil)
+        NotificationCenter.default.addObserver(self, selector: #selector(navigationRouterWillDestroy(_:)), name: NavigationRouter.willDestroy, object: nil)
+    }
+    
+    @objc private func navigationRouterDidCreate(_ notification: Notification) {
+                
+        guard let userInfo = notification.userInfo,
+              let navigationRouter = userInfo[NavigationRouter.NotificationUserInfoKey.navigationRouter] as? NavigationRouterType,
+              let navigationController = userInfo[NavigationRouter.NotificationUserInfoKey.navigationController] as? UINavigationController else {
+            return
+        }
+        
+        if let existingNavigationRouter = self.getNavigationRouter(for: navigationController) {
+            fatalError("\(existingNavigationRouter) is already tied to the same navigation controller as \(navigationRouter). We should have only one NavigationRouter per navigation controller")
+        } else {
+            // FIXME: WeakDictionary does not work with protocol
+            // Find a way to avoid this cast
+            self.navigationRouters[navigationController] = navigationRouter as? NavigationRouter
+        }
+    }
+    
+    @objc private func navigationRouterWillDestroy(_ notification: Notification) {
+        guard let userInfo = notification.userInfo,
+              let navigationRouter = userInfo[NavigationRouter.NotificationUserInfoKey.navigationRouter] as? NavigationRouterType,
+              let navigationController = userInfo[NavigationRouter.NotificationUserInfoKey.navigationController] as? UINavigationController else {
+            return
+        }
+        
+        if let existingNavigationRouter = self.getNavigationRouter(for: navigationController), existingNavigationRouter !== navigationRouter {
+            fatalError("\(existingNavigationRouter) is already tied to the same navigation controller as \(navigationRouter). We should have only one NavigationRouter per navigation controller")
+        }
+        
+        self.removeNavigationRouter(for: navigationController)
+    }
+}

Riot/Routers/NavigationRouterStoreProtocol.swift

@@ -0,0 +1,23 @@
+// 
+// Copyright 2021 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import Foundation
+
+/// `NavigationRouterStoreProtocol` describes a structure that enables to get a NavigationRouter from a UINavigationController instance.
+protocol NavigationRouterStoreProtocol {
+    func getOrCreateNavigationRouter(for navigationController: UINavigationController) -> NavigationRouterType
+    func getNavigationRouter(for navigationController: UINavigationController) -> NavigationRouterType?
+}