Add Community Toolkit example

CommunityToolkitExample/LoginViewModel.cs

@@ -0,0 +1,118 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using CommunityToolkit.Mvvm.Messaging;
+using Terminal.Gui;
+
+namespace CommunityToolkitExample;
+
+internal partial class LoginViewModel : ObservableObject
+{
+    private const string DEFAULT_LOGIN_PROGRESS_MESSAGE = "Press 'Login' to log in.";
+    private const string LOGGING_IN_PROGRESS_MESSAGE = "Logging in...";
+    private const string VALID_LOGIN_MESSAGE = "The input is valid!";
+    private const string INVALID_LOGIN_MESSAGE = "Please enter a valid user name and password.";
+
+    [ObservableProperty]
+    private bool _canLogin;
+
+    private string _password;
+
+    [ObservableProperty]
+    private string _passwordLengthMessage;
+
+    private string _username;
+
+    [ObservableProperty]
+    private string _usernameLengthMessage;
+
+    [ObservableProperty]
+    private string _loginProgressMessage;
+
+    [ObservableProperty]
+    private string _validationMessage;
+
+    [ObservableProperty]
+    private ColorScheme? _validationColorScheme;
+
+    public LoginViewModel ()
+    {
+        Username = string.Empty;
+        Password = string.Empty;
+
+        ClearCommand = new (Clear);
+        LoginCommand = new (Execute);
+
+        Clear ();
+
+        return;
+
+        async void Execute () { await Login (); }
+    }
+
+    public RelayCommand ClearCommand { get; }
+
+    public RelayCommand LoginCommand { get; }
+
+    public string Password
+    {
+        get => _password;
+        set
+        {
+            SetProperty (ref _password, value);
+            PasswordLengthMessage = $"_Password ({_password.Length} characters):";
+            ValidateLogin ();
+        }
+    }
+
+    private void ValidateLogin ()
+    {
+        CanLogin = !string.IsNullOrEmpty (Username) && !string.IsNullOrEmpty (Password);
+        SendMessage (LoginAction.Validation);
+    }
+
+    public string Username
+    {
+        get => _username;
+        set
+        {
+            SetProperty (ref _username, value);
+            UsernameLengthMessage = $"_Username ({_username.Length} characters):";
+            ValidateLogin ();
+        }
+    }
+
+    private void Clear ()
+    {
+        Username = string.Empty;
+        Password = string.Empty;
+        SendMessage (LoginAction.Validation);
+        SendMessage (LoginAction.LoginProgress, DEFAULT_LOGIN_PROGRESS_MESSAGE);
+    }
+
+    private async Task Login ()
+    {
+        SendMessage (LoginAction.LoginProgress, LOGGING_IN_PROGRESS_MESSAGE);
+        await Task.Delay (TimeSpan.FromSeconds (1));
+        Clear ();
+    }
+
+    private void SendMessage (LoginAction loginAction, string message = "")
+    {
+        switch (loginAction)
+        {
+            case LoginAction.LoginProgress:
+                LoginProgressMessage = message;
+                break;
+            case LoginAction.Validation:
+                ValidationMessage = CanLogin ? VALID_LOGIN_MESSAGE : INVALID_LOGIN_MESSAGE;
+                ValidationColorScheme = CanLogin ? Colors.ColorSchemes ["Base"] : Colors.ColorSchemes ["Error"];
+                break;
+        }
+        WeakReferenceMessenger.Default.Send (new Message<LoginAction> { Value = loginAction });
+    }
+
+    public void Initialized ()
+    {
+        Clear ();
+    }
+}