Toolkit2/Toolkit.Foundation.Avalonia/Markups/NavigationRouteExtension.cs

using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.Primitives;
using Avalonia.Data;
using Avalonia.Interactivity;
using Avalonia.Markup.Xaml;

namespace Toolkit.Foundation.Avalonia
{
    public class NavigationRouteExtension : MarkupExtension
    {
        private static readonly AttachedProperty<object> RouteProperty =
            AvaloniaProperty.RegisterAttached<NavigationRouteExtension, Control, object>("Route");

        private readonly string name;
        private readonly Binding? routeBinding;

        public NavigationRouteExtension(object route, string name)
        {
            routeBinding = route is Binding toBinding ? toBinding : route.ToBinding();
            this.name = name;
        }

        private bool TryGetBinding(AvaloniaObject sender, out object? binding)
        {
            binding = sender.GetValue(StyledElement.DataContextProperty);
            return binding is not null;
        }

        public override object? ProvideValue(IServiceProvider serviceProvider)
        {
            if (serviceProvider.GetService(typeof(IProvideValueTarget)) is IProvideValueTarget target)
            {
                if (target.TargetObject is TemplatedControl control)
                {
                    if (routeBinding is not null)
                    {
                        if (!TryGetBinding(control, out object? binding))
                        {
                            void HandleDataContextChanged(object? sender, EventArgs args)
                            {
                                if (TryGetBinding(control, out binding))
                                {
                                    control.Loaded -= HandleLoaded;
                                    control.Bind(RouteProperty, routeBinding);

                                    if (control?.GetValue(RouteProperty) is INavigationRouter router)
                                    {
                                        router.Register(name, control);
                                        control.ClearValue(RouteProperty);
                                    }
                                }
                            }

                            control.DataContextChanged += HandleDataContextChanged;

                            void HandleLoaded(object? sender, RoutedEventArgs args)
                            {
                                control.Loaded -= HandleLoaded;
                                if (TryGetBinding(control, out binding))
                                {
                                    control.Bind(RouteProperty, routeBinding);
                                    if (control?.GetValue(RouteProperty) is INavigationRouter router)
                                    {
                                        router.Register(name, control);
                                        control.ClearValue(RouteProperty);
                                    }
                                }
                            }

                            control.Loaded += HandleLoaded;
                        }
                        else
                        {
                            control.Bind(RouteProperty, routeBinding);
                            if (control?.GetValue(RouteProperty) is INavigationRouter router)
                            {
                                router.Register(name, control);
                                control.ClearValue(RouteProperty);
                            }
                        }
                    }
                }
            }

            return null;
        }
    }
}