Toolkit2/Toolkit.Avalonia/FrameHandler.cs

using Avalonia.Controls;
using Avalonia.Controls.Primitives;
using FluentAvalonia.UI.Media.Animation;
using FluentAvalonia.UI.Navigation;
using System.Reflection;
using Toolkit.Foundation;
using Toolkit.UI.Controls.Avalonia;

namespace Toolkit.Avalonia;

public class FrameHandler :
    INavigateHandler<Frame>,
    INavigateBackHandler<Frame>
{
    public Task Handle(NavigateEventArgs<Frame> args,
        CancellationToken cancellationToken)
    {
        if (args.Context is Frame frame)
        {
            frame.NavigationPageFactory ??= new NavigationPageFactory();
            if (args.Template is Control control)
            {
                void NavigatingFrom(object? sender,
                    Control control)
                {
                    async void HandleNavigatingFrom(object? _,
                        NavigatingCancelEventArgs args)
                    {
                        Dictionary<string, object> results = [];

                        control.RemoveHandler(Frame.NavigatingFromEvent, HandleNavigatingFrom);
                        NavigatedFrom(sender, control, () => results);

                        if (control.DataContext is object content)
                        {
                            if (content is IConfirmation confirmation &&
                                !await confirmation.Confirm())
                            {
                                args.Cancel = true;
                            }

                            if (!args.Cancel)
                            {
                                if (content is IDeactivating deactivating)
                                {
                                    await deactivating.OnDeactivating();
                                }
                            }
                        }
                    }

                    control.AddHandler(Frame.NavigatingFromEvent, HandleNavigatingFrom);
                }

                void NavigatedFrom(object? sender,
                    Control control,
                    Func<Dictionary<string, object>> resultCallBack)
                {
                    async void HandleNavigatedFrom(object? _,
                        NavigationEventArgs args)
                    {
                        control.RemoveHandler(Frame.NavigatedFromEvent, HandleNavigatedFrom);
                        if (args.NavigationMode == NavigationMode.New)
                        {
                            NavigatedTo(sender, control);
                        }

                        Dictionary<string, object> results = resultCallBack.Invoke();
                        async Task DoNavigatedFromAsync(object? content)
                        {
                            if (content is not null)
                            {
                                if (content is IDeactivated deactivated)
                                {
                                    await deactivated.OnDeactivated();
                                }
                            }
                        }

                        if (args.Source is TemplatedControl sourceTemplate)
                        {
                            if (sourceTemplate.DataContext is object content)
                            {
                                await DoNavigatedFromAsync(content);
                            }
                        }

                        if (sender is TemplatedControl senderTemplate)
                        {
                            if (senderTemplate.DataContext is object content)
                            {
                                await DoNavigatedFromAsync(content);
                            }
                        }
                        else
                        {
                            await DoNavigatedFromAsync(sender);
                        }
                    }

                    control.AddHandler(Frame.NavigatedFromEvent, HandleNavigatedFrom);
                }

                void NavigatedTo(object? sender,
                    Control control)
                {
                    async void HandleNavigatedTo(object? _,
                        NavigationEventArgs __)
                    {
                        control.RemoveHandler(Frame.NavigatedToEvent, HandleNavigatedTo);
                        NavigatingFrom(sender, control);

                        if (control.DataContext is object content)
                        {
                            if (content is IInitializer initializer)
                            {
                                await initializer.Initialize();
                            }

                            if (content is IActivated activated)
                            {
                                await activated.OnActivated();
                            }
                        }
                    }

                    control.AddHandler(Frame.NavigatedToEvent, HandleNavigatedTo);
                }

                control.DataContext = args.Content;
                NavigatedTo(args.Sender, control);
                frame.NavigateFromObject(control, new FrameNavigationOptions { TransitionInfoOverride = new SuppressNavigationTransitionInfo() });
            }
        }

        return Task.CompletedTask;
    }

    public Task Handle(NavigateBackEventArgs<Frame> args,
        CancellationToken cancellationToken = default)
    {
        if (args.Context is Frame frame)
        {
            frame.GoBack();
        }

        return Task.CompletedTask;
    }
}