//MODEL-VIEW-PRESENTER

protocol EventHandler {
    func didTapButton()
}

protocol ViewProtocol: AnyObject {
    var state: String {get set}
}

class Presenter: EventHandler {

    weak var view: ViewProtocol?

    func didTapButton() {
        view?.state = "Hello"
    }
}

class View: ViewProtocol {

    let eventHandler: EventHandler

    init(eventHandler: EventHandler) {
        self.eventHandler = eventHandler
    }

    private func handleButtonTap() {
        eventHandler.didTapButton()
    }

    var state: String = "" {
        didSet {
            updateViews()
        }
    }

    private func updateViews() {
        print(state)
    }
}

//MODEL-VIEW-VIEWMODEL

protocol ViewModelProtocol: AnyObject {
    func didTapButton()

    var state: String {get set}

    var stateWasChanged: (()->Void)? {get set}
}

class ViewModel: ViewModelProtocol {
    func didTapButton() {
        state = "Hello"
    }

    var state: String  = "" {
        didSet {
            stateWasChanged?()
        }
    }

    var stateWasChanged: (() -> Void)?
}

class View {

    let viewModel: ViewModelProtocol

    init(viewModel: ViewModelProtocol) {
        self.viewModel = viewModel

        viewModel.stateWasChanged = { [weak self] in
            self?.updateViews()
        }
    }

    private func handleButtonTap() {
        viewModel.didTapButton()
    }

    private func updateViews() {
        print(viewModel.state)
    }
}