feat(ui): centralize retail selection state

tests/AcDream.Core.Tests/Selection/SelectionStateTests.cs

@@ -0,0 +1,100 @@
+using AcDream.Core.Selection;
+using AcDream.Plugin.Abstractions;
+
+namespace AcDream.Core.Tests.Selection;
+
+public sealed class SelectionStateTests
+{
+    [Fact]
+    public void Select_CommitsOneTransitionAndTracksPreviousLikeRetail()
+    {
+        var state = new SelectionState();
+        var transitions = new List<SelectionTransition>();
+        state.Changed += transitions.Add;
+
+        Assert.True(state.Select(0x50000001u, SelectionChangeSource.World));
+        Assert.True(state.Select(0x50000002u, SelectionChangeSource.Radar));
+
+        Assert.Equal(0x50000002u, state.SelectedObjectId);
+        Assert.Equal(0x50000001u, state.PreviousObjectId);
+        Assert.Equal(0x50000001u, state.PreviousValidObjectId);
+        Assert.Equal(2, transitions.Count);
+        Assert.Equal(SelectionChangeSource.Radar, transitions[1].Source);
+        Assert.Equal(SelectionChangeReason.Selected, transitions[1].Reason);
+    }
+
+    [Fact]
+    public void Select_SameObject_IsDeduplicated()
+    {
+        var state = new SelectionState();
+        int changed = 0;
+        state.Changed += _ => changed++;
+
+        Assert.True(state.Select(0x50000001u, SelectionChangeSource.World));
+        Assert.False(state.Select(0x50000001u, SelectionChangeSource.Inventory));
+
+        Assert.Equal(1, changed);
+        Assert.Null(state.PreviousObjectId);
+    }
+
+    [Fact]
+    public void SelectPrevious_SwapsCurrentAndPrevious()
+    {
+        var state = new SelectionState();
+        state.Select(0x50000001u, SelectionChangeSource.World);
+        state.Select(0x50000002u, SelectionChangeSource.World);
+
+        Assert.True(state.SelectPrevious());
+
+        Assert.Equal(0x50000001u, state.SelectedObjectId);
+        Assert.Equal(0x50000002u, state.PreviousObjectId);
+    }
+
+    [Fact]
+    public void ClearRemoved_PreservesRemovedObjectAsPreviousValid()
+    {
+        var state = new SelectionState();
+        SelectionTransition transition = default;
+        state.Changed += value => transition = value;
+        state.Select(0x50000001u, SelectionChangeSource.World);
+
+        Assert.True(state.Clear(
+            SelectionChangeSource.System,
+            SelectionChangeReason.SelectedObjectRemoved));
+
+        Assert.Null(state.SelectedObjectId);
+        Assert.Equal(0x50000001u, state.PreviousObjectId);
+        Assert.Equal(0x50000001u, state.PreviousValidObjectId);
+        Assert.Equal(SelectionChangeReason.SelectedObjectRemoved, transition.Reason);
+    }
+
+    [Fact]
+    public void PluginService_UsesSameStateAndEventStream()
+    {
+        var state = new SelectionState();
+        ISelectionService plugin = state;
+        SelectionChangedEvent change = default;
+        plugin.Changed += value => change = value;
+
+        Assert.True(plugin.Select(0x50000001u));
+
+        Assert.Equal(0x50000001u, state.SelectedObjectId);
+        Assert.Equal(0x50000001u, plugin.SelectedObjectId);
+        Assert.Null(change.PreviousObjectId);
+        Assert.Equal(0x50000001u, change.SelectedObjectId);
+    }
+
+    [Fact]
+    public void PluginListenerFailure_DoesNotEscapeOrBlockOtherPlugins()
+    {
+        var state = new SelectionState();
+        ISelectionService plugin = state;
+        int delivered = 0;
+        plugin.Changed += _ => throw new InvalidOperationException("plugin failure");
+        plugin.Changed += _ => delivered++;
+
+        Assert.Null(Record.Exception(() => plugin.Select(0x50000001u)));
+        Assert.Equal(1, delivered);
+        Assert.Equal(0x50000001u, state.SelectedObjectId);
+    }
+}