Router.swift

//
//  Router.swift
//
//  Created by Guilherme Silva Lisboa on 2016-08-10.
//  Copyright © 2016 GLDev. All rights reserved.
//

import UIKit

enum NavigationPath: Int {
    case home, none
}

class Router {

	// MARK: - Properties

	var childRouter: Router? // Has to be optional since the router might not have children.
	weak var parent: Router? // Has to be optional since the base router wont have a parent.
	var controller: UIViewController = UIViewController()

	var possiblePaths: [NavigationPath] {
		return []
	}
	var routerPath: NavigationPath {
		return .none
	}

	init(parent: Router) {
		self.parent = parent
        parent.childRouter = self
	}

	// MARK: - Lifecycle

	/**
	 Root router initializer. Should only be used for the root router.
	 */
	init() {
	}

	// MARK: - Router Methods

	/**
	 Navigate to new destination from current controller
	 - parameter destination: Navigation destination
	 - parameter data:        optional data to be transmitted between routers.
	 - returns: if the path is possible or not.
	 */
	@discardableResult final func navigateTo(destination: NavigationPath, data: Any? = nil) -> Bool {

		guard routerPath != destination else {
			guard let childRouter = self.childRouter else { return false }
			childRouter.dismissController(router: self, data: data)
			return true
		}
		// check if it's to be intercepted, otherwise take the default destination router
		let destinationRouter: Router? = destinationRouterForPath(path: destination, data: data)
		guard let router = destinationRouter else {
			guard let parent = self.parent else { return false }
			return parent.navigateTo(destination: destination, data: data)
		}
		displayRouter(router: router, path: destination)
		childRouter = router
		return true
	}

	// TODO: Check this too. probably dismissController isn't needed. Check to remove.
	/**
	 Dismiss this router from the navigation
	 - parameter destination: new destination to be handled by the parent if necessary
	 */
	private func dismissController(router: Router, data: Any? = nil) {
		parent?.childWillReturnNavigation(data: data)
		guard let navigationController = router.controller.navigationController else {
			self.controller.dismiss(animated: true, completion: nil)
			return
		}
		if let navController = router.controller as? UINavigationController {
			navController.popToRootViewController(animated: true)
		} else {
			navigationController.popToViewController(router.controller, animated: true)
		}
	}

	// MARK: Abstract Methods

	/**
	 Called when the router navigate back the flow to its parent.
	 - parameter data: any data that might be passed to the previous router in the flow.
	 */
	func childWillReturnNavigation(data: Any? = nil) {
		// To be overrited.
	}

	/**
	 router to be displayed for this path
	 - parameter path: navigation path
	 - parameter data: optional data to be transmitted between routers.
	 - returns: router to be displayed.
	 */
	func destinationRouterForPath(path: NavigationPath, data: Any?) -> Router? {
		return nil
	}

	/**
	 Display a router in a specific way based on the navigation
	 - parameter router: router to be displayed
	 - parameter path:   navigation path.
	 */
	func displayRouter(router: Router, path: NavigationPath) {
		if let navigationController = controller.navigationController {
			navigationController.pushViewController(router.controller, animated: true)
		} else {
			controller.present(router.controller, animated: true, completion: nil)
		}
	}
}