using Avalonia;
using Avalonia.Controls.ApplicationLifetimes;
using Avalonia.Markup.Xaml;
using Avalonia.Threading;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using PLib.Desktop.Controls;
using PLib.Desktop.Imaging;
using PLib.Desktop.ViewModels;
using PLib.Desktop.Views;

namespace PLib.Desktop;

// Fully qualified: the PLib.Application namespace shadows the Application type in this assembly.
public sealed class App : Avalonia.Application
{
    private IHost? _host;

    public override void Initialize() => AvaloniaXamlLoader.Load(this);

    public override void OnFrameworkInitializationCompleted()
    {
        if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
        {
            _host = AppHost.Create(desktop.Args ?? []);
            _host.Start();

            AsyncImage.Loader = _host.Services.GetRequiredService<ThumbnailCache>();

            var viewModel = _host.Services.GetRequiredService<MainWindowViewModel>();
            desktop.MainWindow = new MainWindow { DataContext = viewModel };
            desktop.Exit += OnExit;

            // Kick the first load off once the dispatcher is running, so a failure surfaces
            // through the view model instead of disappearing into an unobserved task.
            Dispatcher.UIThread.Post(
                () => viewModel.InitializeCommand.Execute().Subscribe(),
                DispatcherPriority.Background);
        }

        base.OnFrameworkInitializationCompleted();
    }

    private void OnExit(object? sender, ControlledApplicationLifetimeExitEventArgs e)
    {
        if (_host is null)
        {
            return;
        }

        _host.StopAsync(TimeSpan.FromSeconds(3)).GetAwaiter().GetResult();
        _host.Dispose();
        _host = null;
    }
}