Refine select-all helper and add coverage

ErsatzTV.Core.Tests/ErsatzTV.Core.Tests.csproj

@@ -30,6 +30,7 @@
         <ProjectReference Include="..\ErsatzTV.Core\ErsatzTV.Core.csproj" />
         <ProjectReference Include="..\ErsatzTV.Infrastructure.Sqlite\ErsatzTV.Infrastructure.Sqlite.csproj" />
         <ProjectReference Include="..\ErsatzTV.Infrastructure\ErsatzTV.Infrastructure.csproj" />
+        <ProjectReference Include="..\ErsatzTV\ErsatzTV.csproj" />
     </ItemGroup>
 
 </Project>

ErsatzTV.Core.Tests/Pages/MediaCardSelectionHelperTests.cs

@@ -0,0 +1,38 @@
+using ErsatzTV.Application.MediaCards;
+using ErsatzTV.Pages;
+using NUnit.Framework;
+using Shouldly;
+using System.Collections.Generic;
+
+namespace ErsatzTV.Core.Tests.Pages;
+
+[TestFixture]
+public class MediaCardSelectionHelperTests
+{
+    [Test]
+    public void Should_replace_existing_selection_and_return_last_card()
+    {
+        var existingCard = new MediaCardViewModel(1, "Existing", "Sub", "Existing", "", Core.Domain.MediaItemState.Normal, false);
+        var selected = new HashSet<MediaCardViewModel> { existingCard };
+
+        var first = new MediaCardViewModel(2, "First", "Sub", "First", "", Core.Domain.MediaItemState.Normal, false);
+        var second = new MediaCardViewModel(3, "Second", "Sub", "Second", "", Core.Domain.MediaItemState.Normal, false);
+
+        MediaCardViewModel last = MediaCardSelectionHelper.SelectAllPageItems(selected, new[] { first, second });
+
+        selected.ShouldBe(new[] { first, second }, ignoreOrder: true);
+        last.ShouldBe(second);
+    }
+
+    [Test]
+    public void Should_clear_selection_when_no_cards()
+    {
+        var existingCard = new MediaCardViewModel(1, "Existing", "Sub", "Existing", "", Core.Domain.MediaItemState.Normal, false);
+        var selected = new HashSet<MediaCardViewModel> { existingCard };
+
+        MediaCardViewModel last = MediaCardSelectionHelper.SelectAllPageItems(selected, []);
+
+        selected.ShouldBeEmpty();
+        last.ShouldBeNull();
+    }
+}

ErsatzTV/Pages/MediaCardSelectionHelper.cs

@@ -0,0 +1,20 @@
+using ErsatzTV.Application.MediaCards;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace ErsatzTV.Pages;
+
+public static class MediaCardSelectionHelper
+{
+    public static MediaCardViewModel SelectAllPageItems(
+        ISet<MediaCardViewModel> selectedItems,
+        IEnumerable<MediaCardViewModel> cards)
+    {
+        List<MediaCardViewModel> cardList = (cards ?? Enumerable.Empty<MediaCardViewModel>()).ToList();
+
+        selectedItems.Clear();
+        selectedItems.UnionWith(cardList);
+
+        return cardList.LastOrDefault();
+    }
+}

ErsatzTV/Pages/MultiSelectBase.cs

@@ -8,6 +8,8 @@ using MediatR;
 using Microsoft.AspNetCore.Components;
 using Microsoft.AspNetCore.Components.Web;
 using MudBlazor;
+using System.Linq;
+using static LanguageExt.Prelude;
 
 namespace ErsatzTV.Pages;
 
@@ -40,12 +42,8 @@ public class MultiSelectBase<T> : FragmentNavigationBase
 
     protected void SelectAllPageItems(IEnumerable<MediaCardViewModel> cards)
     {
-        SelectedItems.Clear();
-        foreach (MediaCardViewModel card in cards)
-        {
-            _recentlySelected = card;
-            SelectedItems.Add(card);
-        }
+        MediaCardViewModel lastSelected = MediaCardSelectionHelper.SelectAllPageItems(SelectedItems, cards);
+        _recentlySelected = Optional(lastSelected);
 
         StateHasChanged();
     }