Terminal.Gui/ReactiveExample/LoginView.cs

using System.Reactive.Disposables;
using System.Reactive.Linq;
using ReactiveMarbles.ObservableEvents;
using ReactiveUI;
using Terminal.Gui;

namespace ReactiveExample;

public class LoginView : Window, IViewFor<LoginViewModel>
{
    private readonly CompositeDisposable _disposable = new ();

    public LoginView (LoginViewModel viewModel)
    {
        Title = $"Reactive Extensions Example - {Application.QuitKey} to Exit";
        ViewModel = viewModel;
        Label usernameLengthLabel = UsernameLengthLabel (TitleLabel ());
        TextField usernameInput = UsernameInput (usernameLengthLabel);
        Label passwordLengthLabel = PasswordLengthLabel (usernameLengthLabel);
        TextField passwordInput = PasswordInput (passwordLengthLabel);
        Label validationLabel = ValidationLabel (passwordInput);
        Button loginButton = LoginButton (validationLabel);
        Button clearButton = ClearButton (loginButton);
        LoginProgressLabel (clearButton);
    }

    public LoginViewModel ViewModel { get; set; }

    object IViewFor.ViewModel
    {
        get => ViewModel;
        set => ViewModel = (LoginViewModel)value;
    }

    protected override void Dispose (bool disposing)
    {
        _disposable.Dispose ();
        base.Dispose (disposing);
    }

    private Button ClearButton (View previous)
    {
        var clearButton = new Button
        {
            X = Pos.Left (previous), Y = Pos.Top (previous) + 1, Text = "_Clear"
        };

        clearButton
            .Events ()
            .Accept
            .InvokeCommand (ViewModel, x => x.Clear)
            .DisposeWith (_disposable);
        Add (clearButton);

        return clearButton;
    }

    private Button LoginButton (View previous)
    {
        var loginButton = new Button
        {
            X = Pos.Left (previous), Y = Pos.Top (previous) + 1, Text = "_Login"
        };

        loginButton
            .Events ()
            .Accept
            .InvokeCommand (ViewModel, x => x.Login)
            .DisposeWith (_disposable);
        Add (loginButton);

        return loginButton;
    }

    private Label LoginProgressLabel (View previous)
    {
        var progress = "Logging in...";
        var idle = "Press 'Login' to log in.";

        var loginProgressLabel = new Label
        {
            AutoSize = false,  X = Pos.Left (previous), Y = Pos.Top (previous) + 1, Width = 40, Height = 1, Text = idle
        };

        ViewModel
            .WhenAnyObservable (x => x.Login.IsExecuting)
            .Select (executing => executing ? progress : idle)
            .ObserveOn (RxApp.MainThreadScheduler)
            .BindTo (loginProgressLabel, x => x.Text)
            .DisposeWith (_disposable);
        Add (loginProgressLabel);

        return loginProgressLabel;
    }

    private TextField PasswordInput (View previous)
    {
        var passwordInput = new TextField
        {
            X = Pos.Right (previous) + 1, Y = Pos.Top (previous), Width = 40, Text = ViewModel.Password
        };

        ViewModel
            .WhenAnyValue (x => x.Password)
            .BindTo (passwordInput, x => x.Text)
            .DisposeWith (_disposable);

        passwordInput
            .Events ()
            .TextChanged
            .Select (old => passwordInput.Text)
            .DistinctUntilChanged ()
            .BindTo (ViewModel, x => x.Password)
            .DisposeWith (_disposable);
        Add (passwordInput);

        return passwordInput;
    }

    private Label PasswordLengthLabel (View previous)
    {
        var passwordLengthLabel = new Label { X = Pos.Left (previous), Y = Pos.Top (previous) + 1, };

        ViewModel
            .WhenAnyValue (x => x.PasswordLength)
            .Select (length => $"_Password ({length} characters):")
            .BindTo (passwordLengthLabel, x => x.Text)
            .DisposeWith (_disposable);
        Add (passwordLengthLabel);

        return passwordLengthLabel;
    }

    private Label TitleLabel ()
    {
        var label = new Label { Text = "Login Form" };
        Add (label);

        return label;
    }

    private TextField UsernameInput (View previous)
    {
        var usernameInput = new TextField
        {
            X = Pos.Right (previous) + 1, Y = Pos.Top (previous), Width = 40, Text = ViewModel.Username
        };

        ViewModel
            .WhenAnyValue (x => x.Username)
            .BindTo (usernameInput, x => x.Text)
            .DisposeWith (_disposable);

        usernameInput
            .Events ()
            .TextChanged
            .Select (old => usernameInput.Text)
            .DistinctUntilChanged ()
            .BindTo (ViewModel, x => x.Username)
            .DisposeWith (_disposable);
        Add (usernameInput);

        return usernameInput;
    }

    private Label UsernameLengthLabel (View previous)
    {
        var usernameLengthLabel = new Label { X = Pos.Left (previous), Y = Pos.Top (previous) + 1 };

        ViewModel
            .WhenAnyValue (x => x.UsernameLength)
            .Select (length => $"_Username ({length} characters):")
            .BindTo (usernameLengthLabel, x => x.Text)
            .DisposeWith (_disposable);
        Add (usernameLengthLabel);

        return usernameLengthLabel;
    }

    private Label ValidationLabel (View previous)
    {
        var error = "Please enter a valid user name and password.";
        var success = "The input is valid!";

        var validationLabel = new Label
        {
           X = Pos.Left (previous), Y = Pos.Top (previous) + 1, Text = error
        };

        ViewModel
            .WhenAnyValue (x => x.IsValid)
            .Select (valid => valid ? success : error)
            .BindTo (validationLabel, x => x.Text)
            .DisposeWith (_disposable);

        ViewModel
            .WhenAnyValue (x => x.IsValid)
            .Select (valid => valid ? Colors.ColorSchemes ["Base"] : Colors.ColorSchemes ["Error"])
            .BindTo (validationLabel, x => x.ColorScheme)
            .DisposeWith (_disposable);
        Add (validationLabel);

        return validationLabel;
    }
}