VIPER.Presenter.swift

import Foundation

protocol LoginPresenterInput {

    func emailDidChange(_ email: String)

    func passwordDidChange(_ password: String)

    func submit()
}

protocol LoginPresenterOutput: AnyObject {

    func submit(isEnabled: Bool)

    func loading(_ isLoading: Bool)
}

class LoginPresenter: BasePresenter<LoginInteractorInput, LoginCoordinating> {

    // MARK: - Properties

    var email: String = ""
    var password: String = ""

    var isEmailValid: Bool = false
    var isPasswordValid: Bool = false

    var isLoading: Bool = false

    private(set) weak var view: LoginPresenterOutput?

    var isValid: Bool {
        isEmailValid && isPasswordValid
    }

    func attach(_ view: LoginPresenterOutput) {
        self.view = view
    }
}

extension LoginPresenter: LoginPresenterInput {

    func emailDidChange(_ email: String) {
        interactor.validate(email: email)
    }

    func passwordDidChange(_ password: String) {
        interactor.validate(password: password)
    }

    func submit() {
        guard isValid && !isLoading else {
            return
        }

        isLoading = true
        view?.loading(isLoading)
        interactor.login(email, password)
    }
}

extension LoginPresenter: LoginInteractorOutput {

    func email(isValid: Bool) {
        isEmailValid = isValid
        view?.submit(isEnabled: isValid)
    }

    func password(isValid: Bool) {
        isPasswordValid = isValid
        view?.submit(isEnabled: isValid)
    }

    func login(_ result: Result<Void, Error>) {
        isLoading = false
        view?.loading(isLoading)

        switch result {
        case .success:
            coordinator.openHomeScene()
        case .failure(let error):
            coordinator.openErrorScene(error)
        }
    }
}