/*
 Copyright 2019 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 UIKit

/// `NavigationRouter` is a concrete implementation of NavigationRouterType.
final class NavigationRouter: NSObject, NavigationRouterType {
    
    // MARK: - Properties
    
    // MARK: Private
    
    private var completions: [UIViewController : () -> Void]
    
    // MARK: Public
    
    private let navigationController: UINavigationController    
    
    // MARK: - Setup
    
    init(navigationController: UINavigationController = UINavigationController()) {
        self.navigationController = navigationController
        self.completions = [:]
        super.init()
        self.navigationController.delegate = self
    }
    
    // MARK: - Public
    
    func present(_ module: Presentable, animated: Bool = true) {
        navigationController.present(module.toPresentable(), animated: animated, completion: nil)
    }
    
    func dismissModule(animated: Bool = true, completion: (() -> Void)? = nil) {
        navigationController.dismiss(animated: animated, completion: completion)
    }
    
    func setRootModule(_ module: Presentable, hideNavigationBar: Bool = false) {
        // Call all completions so all coordinators can be deallocated
        completions.forEach { $0.value() }
        navigationController.setViewControllers([module.toPresentable()], animated: false)
        navigationController.isNavigationBarHidden = hideNavigationBar
    }
    
    func popToRootModule(animated: Bool) {
        if let controllers = navigationController.popToRootViewController(animated: animated) {
            controllers.forEach { runCompletion(for: $0) }
        }
    }
    
    func popToModule(_ module: Presentable, animated: Bool) {
        if let controllers = navigationController.popToViewController(module.toPresentable(), animated: animated) {
            controllers.forEach { runCompletion(for: $0) }
        }
    }
    
    func push(_ module: Presentable, animated: Bool = true, popCompletion: (() -> Void)? = nil) {
        
        let controller = module.toPresentable()
        
        // Avoid pushing UINavigationController onto stack
        guard controller is UINavigationController == false else {
            return
        }
        
        if let completion = popCompletion {
            completions[controller] = completion
        }
        
        navigationController.pushViewController(controller, animated: animated)        
    }
    
    func popModule(animated: Bool = true) {
        if let controller = navigationController.popViewController(animated: animated) {
            runCompletion(for: controller)
        }
    }
        
    // MARK: Presentable
    
    func toPresentable() -> UIViewController {
        return navigationController
    }
    
    // MARK: - Private
    
    private func runCompletion(for controller: UIViewController) {
        guard let completion = completions[controller] else { return }
        completion()
        completions.removeValue(forKey: controller)
    }
}

// MARK: - UINavigationControllerDelegate
extension NavigationRouter: UINavigationControllerDelegate {
    
    func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool) {
        
        // Ensure the view controller is popping
        guard let poppedViewController = navigationController.transitionCoordinator?.viewController(forKey: .from),
            !navigationController.viewControllers.contains(poppedViewController) else {
                return
        }
        
        runCompletion(for: poppedViewController)
    }
}