[Library] Coordination library (#15)

This PR contains the work done to implement the necessary protocols and router to implement the Coordinators pattern in the app.

Reviewed-on: #15
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Libraries/Coordination/Kit/Sources/Protocols/Coordinator.swift

@@ -0,0 +1,57 @@
+//
+//  Coordinator.swift
+//  ReviewsCoordinationKit
+//
+//  Created by Javier Cicchelli on 21/03/2024.
+//  Copyright © 2024 Röck+Cöde. All rights reserved.
+//
+
+public protocol Coordinator: AnyObject {
+    
+    // MARK: Properties
+    var children: [Coordinator] { get set }
+    var router: Router { get }
+    
+    // MARK: Functions
+    func present(animated: Bool, onDismiss: Router.OnDismissClosure?)
+    
+}
+
+// MARK: - Implementations
+public extension Coordinator {
+
+    // MARK: Functions
+    func present(
+        child: Coordinator,
+        animated: Bool,
+        onDismiss: Router.OnDismissClosure? = nil
+    ) {
+        store(child)
+
+        child.present(animated: animated) { [weak self, weak child] in
+            guard let self, let child else { return }
+            
+            self.free(child)
+            onDismiss?()
+        }
+    }
+
+    func dismiss(animated: Bool) {
+        router.dismiss(animated: animated)
+    }
+    
+}
+
+// MARK: - Helpers
+private extension Coordinator {
+    
+    // MARK: Functions
+    func store(_ coordinator: Coordinator) {
+        children.append(coordinator)
+    }
+    
+    func free(_ coordinator: Coordinator) {
+        children = children.filter { $0 !== coordinator }
+    }
+    
+}

Libraries/Coordination/Kit/Sources/Protocols/Router.swift

@@ -0,0 +1,42 @@
+//
+//  Router.swift
+//  ReviewsCoordinationKet
+//
+//  Created by Javier Cicchelli on 21/03/2024.
+//  Copyright © 2024 Röck+Cöde. All rights reserved.
+//
+
+import UIKit
+
+public protocol Router: AnyObject {
+    
+    // MARK: Type aliases
+    typealias OnDismissClosure = () -> Void
+    
+    // MARK: Functions
+    func present(
+        _ viewController: UIViewController,
+        animated: Bool,
+        onDismiss: OnDismissClosure?
+    )
+
+    func dismiss(animated: Bool)
+    
+}
+
+// MARK: - Implementations
+public extension Router {
+    
+    // MARK: Functions
+    func present(
+        _ viewController: UIViewController,
+        animated: Bool
+    ) {
+        present(
+            viewController,
+            animated: animated,
+            onDismiss: nil
+        )
+    }
+    
+}

Libraries/Coordination/Kit/Sources/Routers/NavigationRouter.swift

@@ -0,0 +1,55 @@
+//
+//  NavigationRouter.swift
+//  ReviewsCoordinationKit
+//
+//  Created by Javier Cicchelli on 21/03/2024.
+//  Copyright © 2024 Röck+Cöde. All rights reserved.
+//
+
+import UIKit
+
+public class NavigationRouter: NSObject {
+    
+    // MARK: Properties
+    var navigationController: UINavigationController
+    var onDismissForViewController: [UIViewController: Router.OnDismissClosure] = [:]
+    
+    // MARK: Initialisers
+    init(navigationController: UINavigationController) {
+        self.navigationController = navigationController
+        
+        super.init()
+        
+        self.navigationController.delegate = self
+    }
+    
+    // MARK: Functions
+    func performOnDismiss(for viewController: UIViewController) {
+        guard let onDismiss = onDismissForViewController[viewController] else {
+            return
+        }
+        
+        onDismiss()
+        
+        onDismissForViewController[viewController] = nil
+    }
+    
+}
+
+// MARK: - UINavigationControllerDelegate
+extension NavigationRouter: UINavigationControllerDelegate {
+    
+    // MARK: Functions
+    public func navigationController(
+        _ navigationController: UINavigationController,
+        didShow viewController: UIViewController,
+        animated: Bool
+    ) {
+        guard let viewControllerToDismiss = navigationController.transitionCoordinator?.viewController(forKey: .from) else {
+            return
+        }
+        
+        performOnDismiss(for: viewControllerToDismiss)
+    }
+    
+}

Libraries/Coordination/Kit/Sources/Routers/PushRouter.swift

@@ -0,0 +1,56 @@
+//
+//  File.swift
+//  ReviewsCoordinationKit
+//
+//  Created by Javier Cicchelli on 21/03/2024.
+//  Copyright © 2024 Röck+Cöde. All rights reserved.
+//
+
+import UIKit
+
+public class PushRouter: NavigationRouter {
+    
+    // MARK: Constants
+    private let rootViewController: UIViewController?
+    
+    // MARK: Initialisers
+    public init(
+        navigationController: UINavigationController,
+        rootViewController: UIViewController? = nil
+    ) {
+        self.rootViewController = navigationController.viewControllers.first ?? rootViewController
+        
+        super.init(navigationController: navigationController)
+    }
+    
+}
+
+// MARK: - Router
+extension PushRouter: Router {
+    
+    // MARK: Functions
+    public func present(
+        _ viewController: UIViewController,
+        animated: Bool,
+        onDismiss: OnDismissClosure?
+    ) {
+        onDismissForViewController[viewController] = onDismiss
+        
+        navigationController.pushViewController(viewController, animated: animated)
+    }
+    
+    public func dismiss(animated: Bool) {
+        guard let rootViewController else {
+            navigationController.popViewController(animated: animated)
+            return
+        }
+        
+        performOnDismiss(for: rootViewController)
+        
+        navigationController.popToViewController(
+            rootViewController,
+            animated: animated
+        )
+    }
+    
+}

Libraries/Coordination/Kit/Sources/Routers/WindowRouter.swift

@@ -0,0 +1,35 @@
+//
+//  WindowRouter.swift
+//  ReviewsCoordinationKit
+//
+//  Created by Javier Cicchelli on 21/03/2024.
+//  Copyright © 2024 Röck+Cöde. All rights reserved.
+//
+
+import UIKit
+
+public class WindowRouter: Router {
+    
+    // MARK: Constants
+    private let window: UIWindow?
+    
+    // MARK: Initialisers
+    public init(window: UIWindow?) {
+        self.window = window
+    }
+    
+    // MARK: Functions
+    public func present(
+        _ viewController: UIViewController,
+        animated: Bool,
+        onDismiss: OnDismissClosure?
+    ) {
+        window?.rootViewController = viewController
+        window?.makeKeyAndVisible()
+    }
+    
+    public func dismiss(animated: Bool) {
+        // Nothing to do here...
+    }
+    
+}

Libraries/Coordination/Test/Helpers/Coordinators/OtherCoordinator.swift

@@ -0,0 +1,36 @@
+//
+//  OtherCoordinator.swift
+//  ReviewsCoordinationTest
+//
+//  Created by Javier Cicchelli on 21/03/2024.
+//  Copyright © 2024 Röck+Cöde. All rights reserved.
+//
+
+import ReviewsCoordinationKit
+
+final class OtherCoordinator: Coordinator {
+    
+    // MARK: Constants
+    let router: Router
+    
+    // MARK: Properties
+    var children: [Coordinator] = []
+
+    // MARK: Initialisers
+    init(router: Router) {
+        self.router = router
+    }
+    
+    // MARK: Functions
+    func present(
+        animated: Bool,
+        onDismiss: (() -> Void)?
+    ) {
+        router.present(
+            OtherViewController(),
+            animated: animated,
+            onDismiss: onDismiss
+        )
+    }
+    
+}

Libraries/Coordination/Test/Helpers/Coordinators/SomeCoordinator.swift

@@ -0,0 +1,36 @@
+//
+//  SomeCoordinator.swift
+//  ReviewsCoordinationTest
+//
+//  Created by Javier Cicchelli on 21/03/2024.
+//  Copyright © 2024 Röck+Cöde. All rights reserved.
+//
+
+import ReviewsCoordinationKit
+
+final class SomeCoordinator: Coordinator {
+    
+    // MARK: Constants
+    let router: Router
+
+    // MARK: Properties
+    var children: [Coordinator] = []
+
+    // MARK: Initialisers
+    init(router: Router) {
+        self.router = router
+    }
+    
+    // MARK: Functions
+    func present(
+        animated: Bool,
+        onDismiss: (() -> Void)?
+    ) {
+        router.present(
+            SomeViewController(),
+            animated: animated,
+            onDismiss: onDismiss
+        )
+    }
+    
+}

Libraries/Coordination/Test/Helpers/Routers/SpyRouter.swift

@@ -0,0 +1,46 @@
+//
+//  SpyRouter.swift
+//  ReviewsCoordinationTest
+//
+//  Created by Javier Cicchelli on 21/03/2024.
+//  Copyright © 2024 Röck+Cöde. All rights reserved.
+//
+
+import ReviewsCoordinationKit
+import UIKit
+
+final class SpyRouter: Router {
+    
+    // MARK: Properties
+    var animated: Bool?
+    var onDismiss: OnDismissClosure?
+    var state: State = .initialised
+    var viewController: UIViewController?
+
+    // MARK: Functions
+    func present(
+        _ viewController: UIViewController,
+        animated: Bool,
+        onDismiss: OnDismissClosure?
+    ) {
+        self.viewController = viewController
+        self.animated = animated
+        self.onDismiss = onDismiss
+        self.state = .presented
+    }
+    
+    func dismiss(animated: Bool) {
+        self.animated = animated
+        self.state = .dismissed
+    }
+    
+}
+
+// MARK: - Enumerations
+extension SpyRouter {
+    enum State {
+        case initialised
+        case presented
+        case dismissed
+    }
+}

Libraries/Coordination/Test/Helpers/TestViewControllers.swift

@@ -0,0 +1,12 @@
+//
+//  TestViewControllers.swift
+//  ReviewsCoordinationTests
+//
+//  Created by Javier Cicchelli on 21/03/2024.
+//  Copyright © 2024 Röck+Cöde. All rights reserved.
+//
+
+import UIKit
+
+final class SomeViewController: UIViewController {}
+final class OtherViewController: UIViewController {}

Libraries/Coordination/Test/Tests/Protocols/CoordinatorTests.swift

@@ -0,0 +1,143 @@
+//
+//  CoordinatorTests.swift
+//  ReviewsCoordinationTest
+//
+//  Created by Javier Cicchelli on 21/03/2024.
+//  Copyright © 2024 Röck+Cöde. All rights reserved.
+//
+
+import ReviewsCoordinationKit
+import UIKit
+import XCTest
+
+final class CoordinatorTests: XCTestCase {
+    
+    // MARK: Properties
+    private var router: SpyRouter!
+    private var coordinator: Coordinator!
+    
+    // MARK: Tests
+    func testPresent_withoutOnDismissClosure() {
+        // Executing this test on the main thread is required as a `UIViewController` instance in being initialised here.
+        DispatchQueue.main.async {
+            // GIVEN
+            self.router = SpyRouter()
+            self.coordinator = SomeCoordinator(router: self.router)
+
+            // WHEN
+            self.coordinator.present(
+                animated: false,
+                onDismiss: nil
+            )
+            
+            // THEN
+            XCTAssertTrue(self.coordinator.children.isEmpty)
+            XCTAssertEqual(self.router.state, .presented)
+            XCTAssertTrue(self.router.viewController is SomeViewController)
+            XCTAssertFalse(self.router.animated ?? true)
+            XCTAssertNil(self.router.onDismiss)
+        }
+    }
+    
+    func testPresent_withOnDismissClosure() {
+        // Executing this test on the main thread is required as a `UIViewController` instance in being initialised here.
+        DispatchQueue.main.async {
+            // GIVEN
+            self.router = SpyRouter()
+            self.coordinator = OtherCoordinator(router: self.router)
+            
+            // WHEN
+            self.coordinator.present(animated: true) {}
+            
+            // THEN
+            XCTAssertTrue(self.coordinator.children.isEmpty)
+            XCTAssertEqual(self.router.state, .presented)
+            XCTAssertTrue(self.router.viewController is OtherViewController)
+            XCTAssertTrue(self.router.animated ?? false)
+            XCTAssertNotNil(self.router.onDismiss)
+        }
+    }
+    
+    func testPresentChild_withoutOnDismissClosure() {
+        // Executing this test on the main thread is required as a `UIViewController` instance in being initialised here.
+        DispatchQueue.main.async {
+            // GIVEN
+            self.router = SpyRouter()
+            self.coordinator = SomeCoordinator(router: self.router)
+            
+            let child = OtherCoordinator(router: self.router)
+            
+            // WHEN
+            self.coordinator.present(
+                child: child,
+                animated: false
+            )
+            
+            // THEN
+            XCTAssertFalse(self.coordinator.children.isEmpty)
+            XCTAssertEqual(self.coordinator.children.count, 1)
+            XCTAssertEqual(self.router.state, .presented)
+            XCTAssertTrue(self.router.viewController is OtherViewController)
+            XCTAssertFalse(self.router.animated ?? true)
+            XCTAssertNil(self.router.onDismiss)
+        }
+    }
+    
+    func testPresentChild_withOnDismissClosure() {
+        // Executing this test on the main thread is required as a `UIViewController` instance in being initialised here.
+        DispatchQueue.main.async {
+            // GIVEN
+            self.router = SpyRouter()
+            self.coordinator = OtherCoordinator(router: self.router)
+            
+            let child = SomeCoordinator(router: self.router)
+            
+            // WHEN
+            self.coordinator.present(
+                child: child,
+                animated: true
+            ) {}
+            
+            // THEN
+            XCTAssertFalse(self.coordinator.children.isEmpty)
+            XCTAssertEqual(self.coordinator.children.count, 1)
+            XCTAssertEqual(self.router.state, .presented)
+            XCTAssertTrue(self.router.viewController is SomeViewController)
+            XCTAssertTrue(self.router.animated ?? false)
+            XCTAssertNotNil(self.router.onDismiss)
+        }
+    }
+    
+    func testDismiss_notAnimated() {
+        // GIVEN
+        router = SpyRouter()
+        coordinator = OtherCoordinator(router: router)
+        
+        // WHEN
+        coordinator.dismiss(animated: false)
+        
+        // THEN
+        XCTAssertTrue(coordinator.children.isEmpty)
+        XCTAssertEqual(router.state, .dismissed)
+        XCTAssertNil(router.viewController)
+        XCTAssertFalse(router.animated ?? true)
+        XCTAssertNil(router.onDismiss)
+    }
+    
+    func testDismiss_animated() {
+        // GIVEN
+        router = SpyRouter()
+        coordinator = OtherCoordinator(router: router)
+        
+        // WHEN
+        coordinator.dismiss(animated: true)
+        
+        // THEN
+        XCTAssertTrue(coordinator.children.isEmpty)
+        XCTAssertEqual(router.state, .dismissed)
+        XCTAssertNil(router.viewController)
+        XCTAssertTrue(router.animated ?? false)
+        XCTAssertNil(router.onDismiss)
+    }
+    
+}

Libraries/Package.swift

@@ -11,6 +11,7 @@ let package = Package(
         .library(
             name: .Product.name.kit,
             targets: [
+                .Target.coordination.kit,
                 .Target.feed.kit,
                 .Target.filter.kit,
                 .Target.foundation.kit,
@@ -20,6 +21,13 @@ let package = Package(
         ),
     ],
     targets: [
+        .target(
+            name: .Target.coordination.kit,
+            dependencies: [
+                .byName(name: .Target.foundation.kit),
+            ],
+            path: "Coordination/Kit"
+        ),
         .target(
             name: .Target.feed.kit,
             dependencies: [
@@ -53,6 +61,13 @@ let package = Package(
             ],
             path: "UI/Kit"
         ),
+        .testTarget(
+            name: .Target.coordination.test,
+            dependencies: [
+                .byName(name: .Target.coordination.kit),
+            ],
+            path: "Coordination/Test"
+        ),
         .testTarget(
             name: .Target.feed.test,
             dependencies: [
@@ -102,6 +117,7 @@ private extension String {
     }
     
     enum Target {
+        static let coordination = "\(String.Product.name)Coordination"
         static let feed = "\(String.Product.name)Feed"
         static let filter = "\(String.Product.name)Filter"
         static let foundation = "\(String.Product.name)Foundation"