Element preview

src/AppCommon/FileTime.App.Core/Services/ItemPreviewService.cs

@@ -0,0 +1,40 @@
+using System.Reactive.Linq;
+using FileTime.App.Core.ViewModels;
+using FileTime.App.Core.ViewModels.ItemPreview;
+using FileTime.Core.Models;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace FileTime.App.Core.Services;
+
+public class ItemPreviewService : IItemPreviewService
+{
+    private readonly IServiceProvider _serviceProvider;
+    public IObservable<IItemPreviewViewModel?> ItemPreview { get; }
+
+    public ItemPreviewService(IAppState appState, IServiceProvider serviceProvider)
+    {
+        _serviceProvider = serviceProvider;
+        ItemPreview = appState
+            .SelectedTab
+            .Select(t => t?.CurrentSelectedItem.Throttle(TimeSpan.FromMilliseconds(250)) ?? Observable.Return<IItemViewModel?>(null))
+            .Switch()
+            .Select(item =>
+                item == null
+                    ? Observable.Return<IItemPreviewViewModel?>(null)
+                    : Observable.FromAsync(async () => await Map(item))
+            )
+            .Switch()
+            .Publish(null)
+            .RefCount();
+    }
+
+    private async Task<IItemPreviewViewModel?> Map(IItemViewModel itemViewModel)
+    {
+        return itemViewModel.BaseItem switch
+        {
+            IElement element => await _serviceProvider.GetAsyncInitableResolver(element)
+                .GetRequiredServiceAsync<ElementPreviewViewModel>(),
+            _ => null
+        };
+    }
+}