feat: add new Toast.

src/Ursa/Controls/Toast/Toast.cs

@@ -0,0 +1,80 @@
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+using Avalonia.Controls.Notifications;
+
+namespace Ursa.Controls;
+
+/// <summary>
+/// A toast that can be shown in a window or by the host operating system.
+/// </summary>
+/// <remarks>
+/// This class represents a toast that can be displayed either in a window using
+/// <see cref="WindowToastManager"/> or by the host operating system (to be implemented).
+/// </remarks>
+public class Toast : IToast, INotifyPropertyChanged
+{
+    private string? _content;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Toast"/> class.
+    /// </summary>
+    /// <param name="content">The content to be displayed in the toast.</param>
+    /// <param name="type">The <see cref="NotificationType"/> of the toast.</param>
+    /// <param name="expiration">The expiry time at which the toast will close. 
+    /// Use <see cref="TimeSpan.Zero"/> for toasts that will remain open.</param>
+    /// <param name="onClick">An Action to call when the toast is clicked.</param>
+    /// <param name="onClose">An Action to call when the toast is closed.</param>
+    public Toast(
+        string? content,
+        NotificationType type = NotificationType.Information,
+        TimeSpan? expiration = null,
+        Action? onClick = null,
+        Action? onClose = null)
+    {
+        Content = content;
+        Type = type;
+        Expiration = expiration ?? TimeSpan.FromSeconds(5);
+        OnClick = onClick;
+        OnClose = onClose;
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Toast"/> class.
+    /// </summary>
+    public Toast() : this(null)
+    {
+    }
+
+    /// <inheritdoc/>
+    public string? Content
+    {
+        get => _content;
+        set
+        {
+            if (_content != value)
+            {
+                _content = value;
+                OnPropertyChanged();
+            }
+        }
+    }
+
+    /// <inheritdoc/>
+    public NotificationType Type { get; set; }
+
+    /// <inheritdoc/>
+    public TimeSpan Expiration { get; set; }
+
+    /// <inheritdoc/>
+    public Action? OnClick { get; set; }
+
+    /// <inheritdoc/>
+    public Action? OnClose { get; set; }
+
+    public event PropertyChangedEventHandler? PropertyChanged;
+
+    protected virtual void OnPropertyChanged([CallerMemberName] string? propertyName = null)
+    {
+        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+    }
+}