@discardableResult
    func navigate(to stepper: Step) -> StepAction {
        return .none
    }

    private func navigate(flowAction: StepAction) {
        switch flowAction {
        case .dismiss:
            if let presentedViewController = navigationController?.presentedViewController {
                presentedViewController.dismiss(animated: true, completion: nil)
            } else {
                navigationController?.topViewController?.dismiss(animated: true, completion: nil)
            }

        case .push(let controller):
            navigationController?.pushViewController(controller, animated: true)

        case .pop:
            navigationController?.popViewController(animated: true)

        case .present(let controller, let style):
            controller.modalPresentationStyle = style

            if let presentedViewController = navigationController?.presentedViewController {
                presentedViewController.present(controller, animated: true, completion: nil)
            } else {
                navigationController?.topViewController?.present(
                    controller,
                    animated: true,
                    completion: nil
                )
            }

        case .none:
            break
        }
    }

    @discardableResult
    public func start() -> UIViewController? {
        $step
            .compactMap { $0 }
            .sink { [weak self] in
                guard let self = self else { return }

                self.navigate(flowAction: self.navigate(to: $0))
            }
        .store(in: &cancellables)

        return navigationController
    }