acdream/tests/AcDream.App.Tests/UI/Layout/VendorUiControllerTests.cs

using System.Collections.Generic;
using System.Linq;
using AcDream.App.UI;
using AcDream.App.UI.Layout;
using AcDream.Core.Items;
using AcDream.Core.Properties;
using AcDream.Core.Selection;
using AcDream.Runtime.Gameplay;

namespace AcDream.App.Tests.UI.Layout;

/// <summary>
/// Slice 5.4 — mirrors <see cref="ExternalContainerControllerTests"/>'s
/// harness shape (hand-built <see cref="ImportedLayout"/> over
/// <see cref="RetailWindowFrame.Mount"/>) for the behavioral suite, plus one
/// real-dat-fixture smoke test (mirroring
/// <c>AppraisalUiControllerTests</c>'s use of <see cref="FixtureLoader"/>)
/// that catches drift between the hardcoded ids in
/// <see cref="VendorUiController"/> and the actual LayoutDesc 0x21000012.
/// </summary>
public sealed class VendorUiControllerTests
{
    private const uint VendorGuid = 0x70000010u;
    private const uint ArmorItemGuid = 0x60000101u;
    private const uint FoodItemGuid = 0x60000102u;
    private const uint StackedItemGuid = 0x60000103u;

    private sealed class TestElement : UiElement { }

    [Fact]
    public void Bind_FromRealDatFixture_ResolvesAllRequiredControls()
    {
        ImportedLayout layout = FixtureLoader.LoadVendor();
        var screen = new UiRoot { Width = 1280f, Height = 800f };
        RetailWindowHandle window = RetailWindowFrame.Mount(
            screen,
            layout.Root,
            static _ => (0u, 0, 0),
            new RetailWindowFrame.Options
            {
                WindowName = "vendor-fixture-smoke",
                Chrome = RetailWindowChrome.Imported,
                Visible = false,
            });

        var objects = new ClientObjectTable();
        using var itemInteraction = new ItemInteractionController(
            objects,
            new RuntimeInteractionTransactionState(new InventoryTransactionState(objects)),
            new InteractionState(),
            playerGuid: static () => 0u,
            sendUse: null,
            sendUseWithTarget: null,
            sendWield: null,
            sendDrop: null);
        VendorUiController? controller = VendorUiController.Bind(
            layout,
            new VendorState(),
            window,
            static (_, _, _, _, _) => 0u,
            objects,
            static () => 0u,
            itemInteraction,
            new SelectionState(),
            new StackSplitQuantityState(),
            datFont: null,
            debugFont: null,
            static _ => (0u, 0, 0));

        Assert.NotNull(controller);
    }

    [Fact]
    public void Bind_FromRealDatFixture_BuyingAndSellingLists_ConfiguredForEmptySlotFill()
    {
        // G2 (vendor gate finding): the Buying/Selling pages' item strips
        // never got the empty-slot fill the Items list has, so they showed
        // the bare authored blue background instead. This proves the real
        // LayoutDesc 0x21000012 fixture's 0x100000C5 (Buying list)/0x100000CE
        // (Selling list) resolve to real UiItemList widgets and come out of
        // Bind configured identically to the Items strip (F7b) — same
        // single-row/horizontal-scroll/cell-size shape, fill enabled, a
        // non-drag-source empty-slot factory wired, and the sibling
        // scrollbar bound to the SAME list's scroll model. The lists stay
        // UNPOPULATED (no AddItem call anywhere in this path) — staging is
        // still deferred.
        ImportedLayout layout = FixtureLoader.LoadVendor();
        var screen = new UiRoot { Width = 1280f, Height = 800f };
        RetailWindowHandle window = RetailWindowFrame.Mount(
            screen,
            layout.Root,
            static _ => (0u, 0, 0),
            new RetailWindowFrame.Options
            {
                WindowName = "vendor-fixture-smoke-2",
                Chrome = RetailWindowChrome.Imported,
                Visible = false,
            });

        var objects = new ClientObjectTable();
        using var itemInteraction = new ItemInteractionController(
            objects,
            new RuntimeInteractionTransactionState(new InventoryTransactionState(objects)),
            new InteractionState(),
            playerGuid: static () => 0u,
            sendUse: null,
            sendUseWithTarget: null,
            sendWield: null,
            sendDrop: null);
        VendorUiController? controller = VendorUiController.Bind(
            layout,
            new VendorState(),
            window,
            static (_, _, _, _, _) => 0u,
            objects,
            static () => 0u,
            itemInteraction,
            new SelectionState(),
            new StackSplitQuantityState(),
            datFont: null,
            debugFont: null,
            static _ => (0u, 0, 0));
        Assert.NotNull(controller);

        var buyingList = Assert.IsType<UiItemList>(layout.FindElement(VendorUiController.BuyingListId));
        var sellingList = Assert.IsType<UiItemList>(layout.FindElement(VendorUiController.SellingListId));
        var buyingScrollbar = Assert.IsType<UiScrollbar>(
            layout.FindElement(VendorUiController.BuyingScrollbarId));
        var sellingScrollbar = Assert.IsType<UiScrollbar>(
            layout.FindElement(VendorUiController.SellingScrollbarId));

        foreach (UiItemList list in new[] { buyingList, sellingList })
        {
            Assert.True(list.SingleRow);
            Assert.True(list.HorizontalScroll);
            Assert.Equal(32f, list.CellWidth);
            Assert.Equal(32f, list.CellHeight);
            Assert.True(list.FillVisibleEmptySlots);
            Assert.NotNull(list.EmptySlotFactory);
            Assert.Equal(0, list.GetNumUIItems()); // never populated
        }

        Assert.Same(buyingList.Scroll, buyingScrollbar.Model);
        Assert.True(buyingScrollbar.Horizontal);
        Assert.Same(sellingList.Scroll, sellingScrollbar.Model);
        Assert.True(sellingScrollbar.Horizontal);
    }

    private sealed class Harness
    {
        // F2/F3: a deterministic non-zero player coin total so the cost-text
        // "(you have ...)" tail is assertable.
        public const int DefaultPlayerCoinValue = 1500;
        public const uint PlayerGuid = 0x50000001u;

        public readonly VendorState State = new();
        public readonly SelectionState Selection = new();
        public readonly StackSplitQuantityState SplitQuantity = new();
        public readonly UiRoot Screen = new() { Width = 800f, Height = 600f };
        public readonly ClientObjectTable Objects = new();
        public readonly UiItemList ItemList = new();
        public readonly UiScrollbar ItemScrollbar = new();
        public readonly UiMenu TypeMenu = new();
        public readonly UiText ItemNameText = new();
        public readonly UiText ItemCostText = new();
        public readonly UiText ItemsTab = new();
        public readonly UiText BuyingTab = new();
        public readonly UiText SellingTab = new();
        public readonly UiElement ItemsPage = new TestElement();
        public readonly UiElement BuyingPage = new TestElement();
        public readonly UiElement SellingPage = new TestElement();
        public readonly UiButton CloseButton;
        public readonly UiButton BuyButton;
        public readonly UiButton AddButton;
        public readonly RetailWindowHandle Window;
        public readonly VendorUiController Controller;
        public readonly List<uint> Examines = new();
        public readonly List<(uint VendorGuid, uint ItemGuid, int Amount, uint AlternateCurrencyId)> Buys = new();
        public readonly ItemInteractionController ItemInteraction;

        public Harness()
        {
            var bundle = new PropertyBundle();
            bundle.Ints[(uint)PropertyInt.CoinValue] = DefaultPlayerCoinValue;
            Objects.UpsertProperties(PlayerGuid, bundle);

            var root = new TestElement { Width = 800f, Height = 110f };
            CloseButton = new UiButton(
                new ElementInfo { Id = VendorUiController.CloseId, Type = 1 },
                static _ => (0u, 0, 0));
            BuyButton = new UiButton(
                new ElementInfo { Id = VendorUiController.BuyButtonId, Type = 1 },
                static _ => (0u, 0, 0));
            AddButton = new UiButton(
                new ElementInfo { Id = VendorUiController.AddButtonId, Type = 1 },
                static _ => (0u, 0, 0));

            root.AddChild(CloseButton);
            root.AddChild(ItemsTab);
            root.AddChild(BuyingTab);
            root.AddChild(SellingTab);
            root.AddChild(ItemsPage);
            root.AddChild(BuyingPage);
            root.AddChild(SellingPage);
            ItemsPage.AddChild(ItemList);
            ItemsPage.AddChild(ItemScrollbar);
            ItemsPage.AddChild(TypeMenu);
            ItemsPage.AddChild(ItemNameText);
            ItemsPage.AddChild(ItemCostText);
            ItemsPage.AddChild(BuyButton);
            ItemsPage.AddChild(AddButton);

            var layout = new ImportedLayout(root, new Dictionary<uint, UiElement>
            {
                [VendorUiController.CloseId] = CloseButton,
                [VendorUiController.ItemsTabId] = ItemsTab,
                [VendorUiController.BuyingTabId] = BuyingTab,
                [VendorUiController.SellingTabId] = SellingTab,
                [VendorUiController.ItemsPageId] = ItemsPage,
                [VendorUiController.BuyingPageId] = BuyingPage,
                [VendorUiController.SellingPageId] = SellingPage,
                [VendorUiController.ItemListId] = ItemList,
                [VendorUiController.ItemScrollbarId] = ItemScrollbar,
                [VendorUiController.TypeFilterMenuId] = TypeMenu,
                [VendorUiController.ItemNameTextId] = ItemNameText,
                [VendorUiController.ItemCostTextId] = ItemCostText,
                [VendorUiController.BuyButtonId] = BuyButton,
                [VendorUiController.AddButtonId] = AddButton,
            });

            Window = RetailWindowFrame.Mount(
                Screen,
                root,
                static _ => (0u, 0, 0),
                new RetailWindowFrame.Options
                {
                    WindowName = WindowNames.Vendor,
                    Chrome = RetailWindowChrome.Imported,
                    Visible = false,
                    Draggable = false,
                    Resizable = false,
                });

            ItemInteraction = new ItemInteractionController(
                Objects,
                new RuntimeInteractionTransactionState(new InventoryTransactionState(Objects)),
                new InteractionState(),
                playerGuid: static () => PlayerGuid,
                sendUse: null,
                sendUseWithTarget: null,
                sendWield: null,
                sendDrop: null,
                sendExamine: Examines.Add,
                sendBuy: (vendorGuid, itemGuid, amount, alternateCurrencyId) =>
                {
                    Buys.Add((vendorGuid, itemGuid, amount, alternateCurrencyId));
                    return true;
                });

            Controller = VendorUiController.Bind(
                layout,
                State,
                Window,
                // F5: sum every argument so a test can prove underlay/overlay/
                // effects were actually forwarded (iconId-only would silently
                // regress to dropping the last three).
                static (_, iconId, underlay, overlay, effects) => iconId + underlay + overlay + effects,
                Objects,
                static () => PlayerGuid,
                ItemInteraction,
                Selection,
                SplitQuantity,
                datFont: null,
                debugFont: null,
                static _ => (0u, 0, 0))!;
            Screen.WindowManager.AttachController(WindowNames.Vendor, Controller);
        }
    }

    private static VendorShopProfile Profile(
        float sellRate = 1.5f, uint altCurrency = 0u, string altName = "", uint altAmount = 0u) =>
        new(0u, 0u, 0u, false, 1.0f, sellRate, altCurrency, altAmount, altName);

    private static string GetText(UiText text)
        => string.Concat(text.LinesProvider().Select(line => line.Text));

    [Fact]
    public void Bind_WiresTheScrollbarToTheItemListsScrollModel()
    {
        var h = new Harness();

        Assert.True(h.ItemScrollbar.Horizontal);
        Assert.Same(h.ItemList.Scroll, h.ItemScrollbar.Model);
    }

    [Fact]
    public void Opened_ShowsWindowAndPopulatesFirstPresentCategoryInTableOrder()
    {
        var h = new Harness();
        var items = new[]
        {
            // Food is table entry #5, Armor is #1 — retail's fixed table
            // order, not insertion order, decides the default selection.
            new VendorShopItem(FoodItemGuid, -1, 1u, "Bread", (uint)ItemType.Food, 100u, 5),
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
        };

        h.State.Apply(VendorGuid, Profile(), items);

        Assert.True(h.Window.IsVisible);
        Assert.True(h.ItemsPage.Visible);
        Assert.False(h.BuyingPage.Visible);
        Assert.False(h.SellingPage.Visible);
        Assert.Equal(1, h.ItemList.GetNumUIItems());
        Assert.Equal(ArmorItemGuid, h.ItemList.GetItem(0)!.ItemId);
        Assert.Equal("Armor", h.TypeMenu.Items.Single(i => Equals(i.Payload, h.TypeMenu.Selected)).Label);
    }

    [Fact]
    public void Closed_HidesWindowAndClearsListAndText()
    {
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
        });
        h.ItemList.GetItem(0)!.Clicked?.Invoke();
        Assert.True(h.Window.IsVisible);
        Assert.NotEqual(string.Empty, GetText(h.ItemNameText));

        h.State.Close();

        Assert.False(h.Window.IsVisible);
        Assert.Equal(0, h.ItemList.GetNumUIItems());
        Assert.Equal(string.Empty, GetText(h.ItemNameText));
        Assert.Equal(string.Empty, GetText(h.ItemCostText));
        Assert.Empty(h.TypeMenu.Items);
    }

    [Fact]
    public void Reset_HidesWindowAndClearsContent()
    {
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
        });

        h.State.Reset();

        Assert.False(h.Window.IsVisible);
        Assert.Equal(0, h.ItemList.GetNumUIItems());
    }

    [Fact]
    public void SelectingItem_NotInSplitExemptMask_ShowsWholeStackPriceAndFallbackPluralName()
    {
        // F2/F3 (Slice 5.4 review): MissileWeapon (0x100) does NOT intersect
        // the 0xDC41CB0 split-exempt mask, so retail prices/names the WHOLE
        // stack, not one unit — the review flagged the OLD test (asserting a
        // per-unit price + bare "Arrows") as wrong.
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(sellRate: 2.0f), new[]
        {
            // Value=1000 is the STACK-TOTAL wire value for a 100-unit stack;
            // per-unit = 1000/100 = 10. quantity = DescStackSize = 100 (not
            // exempt). SellPrice = ceil(2.0*10*100 - 0.1) = 2000
            // (VendorPricing.SellPrice, ShopSystem::SellPrice pc:702107).
            new VendorShopItem(
                StackedItemGuid, -1, 3u, "Arrows", (uint)ItemType.MissileWeapon, 300u, 1000,
                DescStackSize: 100),
        });

        h.ItemList.GetItem(0)!.Clicked?.Invoke();
        // F2 (Slice 6 review): the display now reads the LIVE split state
        // instead of recomputing a static seed. Production seeds this via
        // SelectedObjectController (mounted on the toolbar, subscribed to
        // SelectionState.Changed BEFORE VendorUiController — RetailUiRuntime
        // MountToolbar() runs before MountVendor()); this harness doesn't
        // mount that controller, so the test seeds SplitQuantity directly to
        // stand in for it, matching the SAME not-exempt full-stack seed
        // SelectedObjectController.ApplySelection would have computed.
        h.SplitQuantity.Reset(100u, initialValue: 100u);

        // No authored PluralName -> ACCWeenieObject::GetObjectName falls back
        // to the singular name UNCHANGED (not an invented "Arrows" + "s").
        Assert.Equal("100 Arrows", GetText(h.ItemNameText));
        Assert.Equal(
            $"cost {2000:N0}p (you have {Harness.DefaultPlayerCoinValue:N0}p)",
            GetText(h.ItemCostText));
    }

    [Fact]
    public void SelectingItem_InSplitExemptMask_ShowsPerUnitPriceAndSingularName()
    {
        // F2/F3: Food (0x20) DOES intersect the split-exempt mask, so
        // quantity is forced to 1 even though the item has a larger
        // authored stack — the mask-member case the review asked for.
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(sellRate: 2.0f), new[]
        {
            // perUnit = 500/50 = 10. quantity forced to 1 (Food is masked).
            // SellPrice = ceil(2.0*10*1 - 0.1) = 20.
            new VendorShopItem(
                FoodItemGuid, -1, 1u, "Bread", (uint)ItemType.Food, 100u, 500,
                DescStackSize: 50),
        });

        h.ItemList.GetItem(0)!.Clicked?.Invoke();
        // F2: exempt seed is 1 regardless of the 50-unit authored stack —
        // see the split-exempt comment on the sibling test above for why
        // this harness seeds SplitQuantity explicitly.
        h.SplitQuantity.Reset(50u, initialValue: 1u);

        Assert.Equal("Bread", GetText(h.ItemNameText));
        Assert.Equal(
            $"costs {20:N0}p (you have {Harness.DefaultPlayerCoinValue:N0}p)",
            GetText(h.ItemCostText));
    }

    [Fact]
    public void SelectingItem_WithAuthoredPluralName_UsesItInsteadOfSingular()
    {
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(
                StackedItemGuid, -1, 3u, "Iron Key", (uint)ItemType.Key, 50u, 100,
                DescStackSize: 10, PluralName: "Iron Keys"),
        });

        h.ItemList.GetItem(0)!.Clicked?.Invoke();
        // F2: Key is not split-exempt -> full authored stack (10).
        h.SplitQuantity.Reset(10u, initialValue: 10u);

        Assert.Equal("10 Iron Keys", GetText(h.ItemNameText));
    }

    [Fact]
    public void SliderChange_AfterSelection_UpdatesNameAndPriceToLiveQuantity_MatchingWhatBuyWouldCharge()
    {
        // F2 (Slice 6 review): retail re-runs UpdateItemsUI on every slider
        // change (gmVendorUI::RecvNotice_StackSliderChanged,
        // pc:203262-203278) -- the OLD implementation froze the display's
        // quantity at a static per-selection seed while BuySelectedItem
        // separately read the LIVE split, so a slider drag after selecting
        // never updated the sentence/price and could show a DIFFERENT price
        // than what Buy would actually charge. Both now go through the SAME
        // ResolveBuyQuantity, proven here by asserting the displayed price
        // equals the amount the subsequent Buy press actually sends.
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(sellRate: 2.0f), new[]
        {
            // perUnit = 1000/100 = 10 (MissileWeapon, not split-exempt).
            new VendorShopItem(
                StackedItemGuid, -1, 3u, "Arrows", (uint)ItemType.MissileWeapon, 300u, 1000,
                DescStackSize: 100),
        });
        // F6 auto-selects the sole item; the harness's un-mounted-toolbar
        // split state starts at its class default (Value=1/Maximum=1) —
        // singular display, matching a fresh, not-yet-slider-touched
        // selection.
        Assert.Equal("Arrows", GetText(h.ItemNameText));
        Assert.Equal(
            $"costs {20:N0}p (you have {Harness.DefaultPlayerCoinValue:N0}p)",
            GetText(h.ItemCostText));

        // Player drags the slider to 40 AFTER selecting -- no re-click, no
        // re-selection, purely a StackSplitQuantityState.Changed event.
        h.SplitQuantity.Reset(100u, initialValue: 40u);

        // SellPrice = ceil(2.0*10*40 - 0.1) = 800.
        Assert.Equal("40 Arrows", GetText(h.ItemNameText));
        Assert.Equal(
            $"cost {800:N0}p (you have {Harness.DefaultPlayerCoinValue:N0}p)",
            GetText(h.ItemCostText));

        h.BuyButton.OnClick!.Invoke();

        Assert.Equal(40, h.Buys.Single().Amount);
    }

    [Fact]
    public void SelectingItem_WithAlternateCurrency_ShowsFullRetailCostSentence()
    {
        // F2/F3: the OLD implementation just appended the currency name after
        // a bare number ("50 Trade Notes"). Retail's actual alt-currency
        // sentence is a full two-clause sentence with a "you have" tail
        // (acclient_2013_pseudo_c.txt:991314), using RAW (non-comma-grouped)
        // integers — unlike the primary-currency branch.
        var h = new Harness();
        h.State.Apply(
            VendorGuid,
            Profile(sellRate: 1.0f, altCurrency: 0x12345678u, altName: "Trade Notes", altAmount: 12345u),
            new[]
            {
                new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 50),
            });

        h.ItemList.GetItem(0)!.Clicked?.Invoke();

        // Armor (not in the split-exempt mask) with DescStackSize null ->
        // PerUnitValue returns Value unchanged (50); quantity = 1 (no
        // authored stack) -> SellPrice(50, Armor, 1.0, 1) = ceil(50-0.1) = 50.
        Assert.Equal(
            "This item costs 50 Trade Notes. You have 12345 Trade Notes.",
            GetText(h.ItemCostText));
    }

    [Fact]
    public void NoSelection_DisablesBuyButton_SelectionEnablesIt()
    {
        var h = new Harness();
        Assert.False(h.BuyButton.Enabled);

        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
        });

        // F4 auto-selects the sole item on open, so Buy is already enabled
        // — SetState(1), pc:202784-202789.
        Assert.True(h.BuyButton.Enabled);

        // Closing clears the selection -> SetState(0xd), pc:202572-202577.
        h.State.Close();
        Assert.False(h.BuyButton.Enabled);
    }

    [Fact]
    public void AddButton_IsPermanentlyDisabled_RegardlessOfSelection()
    {
        // F8 (Slice 6 review): "Add to List" has no wired OnClick at all
        // (staging into the "Buying" tab is deferred, contract decision 6)
        // — an enabled button that silently does nothing on click is a
        // dead-affordance bug, worse than a disabled one. It must never
        // enable, with or without a selection.
        var h = new Harness();
        Assert.False(h.AddButton.Enabled);

        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
        });

        // F4/F6 auto-selects the sole item on open -- Add stays disabled.
        Assert.False(h.AddButton.Enabled);

        h.State.Close();
        Assert.False(h.AddButton.Enabled);
    }

    [Fact]
    public void ShopItem_WithIconUnderlayOverlayEffects_ForwardsThemToResolveIcon()
    {
        // F5: PublicWeenieDescBody already carries these three; the review
        // flagged VendorUiController hardcoding 0u/0u/0u instead of
        // forwarding item.IconUnderlayId/IconOverlayId/Effects.
        var h = new Harness();
        var item = new VendorShopItem(
            ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, IconId: 200u, Value: 500,
            IconUnderlayId: 10u, IconOverlayId: 100u, Effects: 1000u);
        h.State.Apply(VendorGuid, Profile(), new[] { item });

        // Harness's resolveIcon sums every argument (see its comment) — this
        // regresses to 200u alone if the three are dropped again.
        Assert.Equal(200u + 10u + 100u + 1000u, h.ItemList.GetItem(0)!.IconTexture);
    }

    [Fact]
    public void SelectingDifferentCategory_FiltersItemListToThatCategoryOnly()
    {
        var h = new Harness();
        var armor = new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500);
        var food = new VendorShopItem(FoodItemGuid, -1, 1u, "Bread", (uint)ItemType.Food, 100u, 5);
        h.State.Apply(VendorGuid, Profile(), new[] { armor, food });
        Assert.Equal(ArmorItemGuid, h.ItemList.GetItem(0)!.ItemId); // default: Armor (table order)

        object? foodPayload = h.TypeMenu.Items.First(i => i.Label == "Food").Payload;
        h.TypeMenu.OnSelect!.Invoke(foodPayload);

        Assert.Equal(1, h.ItemList.GetNumUIItems());
        Assert.Equal(FoodItemGuid, h.ItemList.GetItem(0)!.ItemId);
    }

    [Fact]
    public void SelectingDifferentCategory_AutoSelectsFirstFilteredItem()
    {
        // F4: VendorItemsUI::UpdateItemsList's tail (pc:201180-201190) —
        // after a category switch the first item that passed the filter
        // becomes the display selection, not a cleared blank.
        var h = new Harness();
        var armor = new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500);
        var food = new VendorShopItem(FoodItemGuid, -1, 1u, "Bread", (uint)ItemType.Food, 100u, 5);
        h.State.Apply(VendorGuid, Profile(), new[] { armor, food });

        object? foodPayload = h.TypeMenu.Items.First(i => i.Label == "Food").Payload;
        h.TypeMenu.OnSelect!.Invoke(foodPayload);

        Assert.Equal(FoodItemGuid, h.ItemList.GetItem(0)!.ItemId);
        Assert.True(h.ItemList.GetItem(0)!.Selected);
        Assert.NotEqual(string.Empty, GetText(h.ItemNameText));
        Assert.NotEqual(string.Empty, GetText(h.ItemCostText));
        Assert.True(h.BuyButton.Enabled);
    }

    [Fact]
    public void SelectingDifferentCategory_ResetsListScrollToStart()
    {
        // F7a: VendorItemsUI::UpdateItemsList's tail (pc:201186-201190) —
        // ScrollToShow(m_shopList, 0) fires unconditionally on every rebuild.
        var h = new Harness();
        var armor = new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500);
        var food = new VendorShopItem(FoodItemGuid, -1, 1u, "Bread", (uint)ItemType.Food, 100u, 5);
        h.State.Apply(VendorGuid, Profile(), new[] { armor, food });

        object? foodPayload = h.TypeMenu.Items.First(i => i.Label == "Food").Payload;
        h.TypeMenu.OnSelect!.Invoke(foodPayload);

        Assert.Equal(0, h.ItemList.Scroll.ScrollY);
    }

    [Fact]
    public void ItemList_FillsVisibleEmptySlots()
    {
        // F7b: mirrors ExternalContainerController.ConfigureList's empty-slot
        // fill so the authored 22-slot strip doesn't show blank space.
        var h = new Harness();

        Assert.True(h.ItemList.FillVisibleEmptySlots);
        Assert.NotNull(h.ItemList.EmptySlotFactory);
    }

    [Fact]
    public void ShopRow_NeverMintsADragPayload()
    {
        // F3 (Slice 6 review): with shop items materialized into
        // ClientObjectTable (Slice 6.1), a draggable vendor cell would pass
        // every destination handler's existence guard -- a pack drop would
        // send a real PutItemInContainer for vendor stock, the shortcut bar
        // would persist a dangling guid, and PlaceIn3D would fire. Retail
        // excludes vendor/salvage lists from ItemList_BeginDrag entirely; a
        // populated shop row must never become a drag source at all.
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
        });

        UiItemSlot cell = h.ItemList.GetItem(0)!;

        Assert.NotEqual(0u, cell.ItemId); // occupied -- would otherwise be a drag source by default
        Assert.False(cell.IsDragSource);
        Assert.Null(cell.GetDragPayload());
        // G3 (vendor gate finding): a row must still CAPTURE its own press
        // even though it never mints a drag payload -- see
        // UiItemSlot.HandlesClick and the real-event-path test below.
        Assert.True(cell.HandlesClick);
    }

    [Fact]
    public void ShopRow_ClickEvent_SelectsItem_DespiteNotBeingADragSource()
    {
        // G3 (vendor gate finding): the F3 drag-suppression fix
        // (AllowDragSource=false) left occupied vendor rows with
        // IsDragSource==false -- before the G3 fix that meant UiRoot's
        // mousedown dispatch found no reason to claim the press at all, so
        // it fell through to the window-move fallback (hover showed the
        // move-window cursor; a press dragged the whole panel instead of
        // selecting a row). This drives the REAL UiItemSlot.OnEvent state
        // machine (MouseDown then Click), the same sequence UiRoot's
        // dispatch produces, rather than invoking the wired Clicked
        // delegate directly -- proving the row still completes a press then
        // click and drives selection.
        const uint SecondArmorGuid = 0x60000110u;
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
            new VendorShopItem(SecondArmorGuid, -1, 4u, "Buckler", (uint)ItemType.Armor, 900u, 40),
        });
        Assert.Equal(ArmorItemGuid, h.Selection.SelectedObjectId); // auto-selected first

        UiItemSlot secondCell = h.ItemList.GetItem(1)!;
        Assert.Equal(SecondArmorGuid, secondCell.ItemId);
        Assert.False(secondCell.IsDragSource);   // never a drag source (F3)
        Assert.True(secondCell.HandlesClick);    // but still claims its own press (G3)

        secondCell.OnEvent(new UiEvent(0u, secondCell, UiEventType.MouseDown));
        secondCell.OnEvent(new UiEvent(0u, secondCell, UiEventType.Click));

        Assert.Equal(SecondArmorGuid, h.Selection.SelectedObjectId);
        Assert.True(secondCell.Selected);
    }

    [Fact]
    public void Opened_WithDifferentVendor_ResetsToFirstPresentCategory_NotThePreviousVendors()
    {
        // F6: gmVendorUI::OpenVendor flushes sub-UIs when sameVendor==0
        // (pc:203664-203667) — a different vendor must not inherit whatever
        // category index the LAST vendor happened to have selected.
        const uint OtherVendorGuid = 0x70000020u;
        const uint OtherArmorGuid = 0x60000201u;
        const uint OtherFoodGuid = 0x60000202u;

        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
            new VendorShopItem(FoodItemGuid, -1, 1u, "Bread", (uint)ItemType.Food, 100u, 5),
        });
        object? foodPayload = h.TypeMenu.Items.First(i => i.Label == "Food").Payload;
        h.TypeMenu.OnSelect!.Invoke(foodPayload);
        Assert.Equal("Food", h.TypeMenu.Items.Single(i => Equals(i.Payload, h.TypeMenu.Selected)).Label);

        // A DIFFERENT vendor, which ALSO has >=2 categories (Armor then
        // Food, table order) so a stale numeric index (1) would silently
        // "validate" without the fix and land on Food again by coincidence
        // rather than by the vendor's own contents.
        h.State.Apply(OtherVendorGuid, Profile(), new[]
        {
            new VendorShopItem(OtherArmorGuid, -1, 4u, "Buckler", (uint)ItemType.Armor, 900u, 40),
            new VendorShopItem(OtherFoodGuid, -1, 5u, "Ale", (uint)ItemType.Food, 100u, 3),
        });

        Assert.Equal("Armor", h.TypeMenu.Items.Single(i => Equals(i.Payload, h.TypeMenu.Selected)).Label);
        Assert.Equal(OtherArmorGuid, h.ItemList.GetItem(0)!.ItemId);
    }

    [Fact]
    public void Refreshed_SameVendor_PreservesCategorySelection()
    {
        // F6 counterpart: gmVendorUI::OpenVendor's sameVendor==1 path does
        // NOT flush sub-UIs, so a same-vendor refresh (Slice 6 post-buy/sell)
        // must keep the player's chosen category.
        var h = new Harness();
        var items = new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
            new VendorShopItem(FoodItemGuid, -1, 1u, "Bread", (uint)ItemType.Food, 100u, 5),
        };
        h.State.Apply(VendorGuid, Profile(), items);
        object? foodPayload = h.TypeMenu.Items.First(i => i.Label == "Food").Payload;
        h.TypeMenu.OnSelect!.Invoke(foodPayload);

        // SAME vendor id re-approaches -> VendorStateTransitionKind.Refreshed.
        h.State.Apply(VendorGuid, Profile(), items);

        Assert.Equal("Food", h.TypeMenu.Items.Single(i => Equals(i.Payload, h.TypeMenu.Selected)).Label);
    }

    [Fact]
    public void Refreshed_SameVendor_ReselectsFirstItemUnconditionally_NotThePreviouslySelectedSurvivor()
    {
        // F6 (Slice 6 review): retail's VendorItemsUI::UpdateItemsList
        // selects UNCONDITIONALLY on every rebuild call site this
        // controller reaches (pc:201180-201184, confirmed via
        // VendorItemsUI::OpenVendor's unconditional clamp +
        // SetSelectedItem(...,1) at pc:201022, which every vendor
        // open/refresh runs regardless of the sameVendor flag) -- there is
        // NO survival test. A same-vendor refresh that re-lists the SAME
        // two items in the SAME order must reset to the FIRST one even
        // though the player's prior selection (the second item) is still
        // present in the new snapshot -- this is the case that would have
        // diverged under the OLD "preserve if it survives" logic.
        const uint SecondArmorGuid = 0x60000110u;
        var h = new Harness();
        var items = new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
            new VendorShopItem(SecondArmorGuid, -1, 4u, "Buckler", (uint)ItemType.Armor, 900u, 40),
        };
        h.State.Apply(VendorGuid, Profile(), items);
        Assert.Equal(ArmorItemGuid, h.ItemList.GetItem(0)!.ItemId); // auto-selected first

        // Player explicitly picks the SECOND item.
        h.ItemList.GetItem(1)!.Clicked?.Invoke();
        Assert.True(h.ItemList.GetItem(1)!.Selected);

        // SAME vendor, SAME two items, SAME order -> Refreshed transition.
        h.State.Apply(VendorGuid, Profile(), items);

        // Retail resets to the FIRST item, not the still-present second one.
        Assert.True(h.ItemList.GetItem(0)!.Selected);
        Assert.False(h.ItemList.GetItem(1)!.Selected);
        Assert.Equal("Chainmail", GetText(h.ItemNameText));
    }

    [Fact]
    public void CategoryMenu_OpensAndSelectsThroughRealHitPath_UsingAuthoredPopupGeometry()
    {
        // F1: the popup never rendered because SpriteResolve/fonts/sprites
        // were never wired, and the geometry was chat's own authored values
        // instead of the vendor dropdown's. This drives the SAME UiEvent
        // hit-test path UiMenuTests uses (not a direct OnSelect call), and
        // reads the geometry back off the live widget instead of hardcoding
        // pixel offsets tied to a specific constant set.
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
            new VendorShopItem(FoodItemGuid, -1, 1u, "Bread", (uint)ItemType.Food, 100u, 5),
        });

        // Wiring: without these UiMenu.OnDrawOverlay early-returns (nothing
        // renders) and the button face never draws either.
        Assert.NotNull(h.TypeMenu.SpriteResolve);
        Assert.NotEqual(0u, h.TypeMenu.NormalSprite);
        Assert.NotEqual(0u, h.TypeMenu.ItemNormalSprite);
        Assert.NotEqual(0u, h.TypeMenu.ItemHighlightSprite);

        // Geometry from the authored template (LayoutDesc 0x21000043's row
        // element 0x10000352 and ListBox 0x10000350), NOT chat's 7/17/191.
        Assert.Equal(6, h.TypeMenu.RowsPerColumn);
        Assert.Equal(18f, h.TypeMenu.RowHeight);
        Assert.Equal(100f, h.TypeMenu.ColumnWidth);

        // Open via the real widget event path.
        Assert.True(h.TypeMenu.OnEvent(new UiEvent(0, h.TypeMenu, UiEventType.MouseDown, 0, 10, 5)));

        // "Food" is the 2nd present category in table order (Armor, then
        // Food) -> row index 1, column 0. Derive the click point from the
        // widget's own live geometry (mirrors UiMenu.OnEvent's own math)
        // rather than a hardcoded pixel constant.
        const int border = 5; // RetailChromeSprites.Border (UiMenu's private bevel thickness)
        float outerH = h.TypeMenu.RowsPerColumn * h.TypeMenu.RowHeight + 2 * border;
        const int targetRow = 1;
        float iy = targetRow * h.TypeMenu.RowHeight + h.TypeMenu.RowHeight / 2f;
        float ly = iy - outerH + border;

        Assert.True(h.TypeMenu.OnEvent(new UiEvent(0, h.TypeMenu, UiEventType.MouseDown, 0, 10, (int)ly)));

        Assert.Equal("Food", h.TypeMenu.Items.Single(i => Equals(i.Payload, h.TypeMenu.Selected)).Label);
        Assert.Equal(FoodItemGuid, h.ItemList.GetItem(0)!.ItemId);
    }

    [Fact]
    public void CloseButton_HidesTheWindowOnly_LeavesTheSessionOpenForARefreshInPlaceReopen()
    {
        // G4 (vendor gate finding): retail's close/pushpin button —
        // gmVendorUI::HandleButtonClicks's 0x100000d6 case (pc:204147-204182)
        // — with nothing staged in the Buying/Selling lists (this port never
        // stages anything; Slice 6 territory) calls ONLY SetVisible(0),
        // never gmVendorUI::CloseVendor (pc:202080, the range-watcher-
        // unregister/session-teardown function VendorState.Close ports).
        // The OLD port called VendorState.Close() directly from this button
        // — an over-eager full teardown retail does not perform on an
        // ordinary close. RuntimeVendorRangeQuery.EnforceRange (evaluated
        // every frame regardless of window visibility) remains the sole
        // path to a full close once the player actually leaves UseRadius —
        // see Closed_HidesWindowAndClearsListAndText for that path,
        // unaffected by this change since it calls VendorState.Close()
        // directly rather than through this button.
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
        });

        h.CloseButton.OnClick!.Invoke();

        Assert.False(h.Window.IsVisible);
        // Unlike the OLD port, the session itself is NOT torn down — the
        // owner still reports the same open vendor in the background,
        // matching retail's hidden-but-still-registered range watcher.
        Assert.Equal(VendorGuid, h.State.VendorId);

        // Re-approaching the SAME vendor (e.g. pressing Use again while
        // still in range) now reaches retail's sameVendor==1 refresh-in-
        // place path (VendorStateTransitionKind.Refreshed) instead of a
        // from-scratch Opened, and reopens the window.
        var kinds = new List<VendorStateTransitionKind>();
        h.State.Changed += t => kinds.Add(t.Kind);
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
        });

        Assert.True(h.Window.IsVisible);
        Assert.Equal([VendorStateTransitionKind.Refreshed], kinds);
    }

    [Fact]
    public void SellingTab_SwitchesPageButPopulatesNoSellContent()
    {
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
        });

        h.SellingTab.OnClick!.Invoke();

        Assert.True(h.SellingPage.Visible);
        Assert.False(h.ItemsPage.Visible);
        Assert.False(h.BuyingPage.Visible);
        // Slice 6 fence: no sell-list/price/button wiring exists at all —
        // the page is exactly the authored-empty container it started as.
        Assert.Empty(h.SellingPage.Children);
    }

    [Fact]
    public void BuyingTab_SwitchesPageButPopulatesNoBuyContent()
    {
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
        });

        h.BuyingTab.OnClick!.Invoke();

        Assert.True(h.BuyingPage.Visible);
        Assert.False(h.ItemsPage.Visible);
        Assert.Empty(h.BuyingPage.Children);
    }

    [Fact]
    public void ItemsTab_ReselectedAfterVisitingOtherTabs_ShowsBrowseListAgain()
    {
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
        });
        h.SellingTab.OnClick!.Invoke();

        h.ItemsTab.OnClick!.Invoke();

        Assert.True(h.ItemsPage.Visible);
        Assert.False(h.SellingPage.Visible);
        Assert.Equal(1, h.ItemList.GetNumUIItems());
    }

    [Fact]
    public void RightClickShopRow_SelectsAndRoutesThroughItemInteractionExamine()
    {
        // Slice 6.1: mirrors ExternalContainerControllerTests'
        // RightClickLoot_selectsAndExaminesWithoutPickingUp — the shop list
        // wires ExamineItemRequested the same way the container lists do,
        // now that shop items are materialized into ClientObjectTable
        // (AP-161 finding #2's examine gap closes here).
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
            new VendorShopItem(FoodItemGuid, -1, 1u, "Bread", (uint)ItemType.Food, 100u, 5),
        });
        // Food, not the auto-selected Armor default, so the assertion below
        // proves the right click itself drove the selection.
        UiItemSlot? foodCell = null;
        object? foodPayload = h.TypeMenu.Items.First(i => i.Label == "Food").Payload;
        h.TypeMenu.OnSelect!.Invoke(foodPayload);
        foodCell = h.ItemList.GetItem(0);
        Assert.Equal(FoodItemGuid, foodCell!.ItemId);

        foodCell.OnEvent(new UiEvent(0u, foodCell, UiEventType.RightClick));

        Assert.Equal(new[] { FoodItemGuid }, h.Examines);
        Assert.Equal("Bread", GetText(h.ItemNameText));
        Assert.True(foodCell.Selected);
    }

    // ── Slice 6.3: Buy button ────────────────────────────────────────────

    [Fact]
    public void BuyButton_Press_NonStackedItem_BuysQuantityOne()
    {
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
        });
        // F4 auto-selected the sole item; its own stack size (default/absent)
        // is <=1, so StackSplitQuantityState was never seeded above 1 either
        // (this harness doesn't mount SelectedObjectController, so the split
        // state starts at its class default Value=1/Maximum=1 — exactly what
        // production would also show for a non-stacked item).

        h.BuyButton.OnClick!.Invoke();

        Assert.Equal(
            new[] { (VendorGuid, ArmorItemGuid, 1, 0u) },
            h.Buys);
    }

    [Fact]
    public void BuyButton_Press_StackedItem_UsesTheLiveSplitSliderQuantity()
    {
        // Slice 6.3: BuySingleItem (pc:201674-201681) reads the CURRENT
        // slider value, not the full stack. This harness doesn't mount
        // SelectedObjectController (the toolbar owns that seeding in
        // production), so the test seeds SplitQuantity directly to stand in
        // for "the player selected this item, then dragged the slider to
        // 25" before pressing Buy.
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(
                StackedItemGuid, -1, 3u, "Arrows", (uint)ItemType.MissileWeapon, 300u, 1000,
                DescStackSize: 100),
        });
        h.SplitQuantity.Reset(100u, initialValue: 25u);

        h.BuyButton.OnClick!.Invoke();

        Assert.Equal(25, h.Buys.Single().Amount);
    }

    [Fact]
    public void BuyButton_Press_NonStackedItem_IgnoresAStaleSliderFromAPreviouslySelectedStackableItem()
    {
        // F7 (Slice 6 review): retail's BuySingleItem (pc:201674-201681)
        // gates on the SELECTED item's OWN stack size FIRST -- quantity 1
        // whenever it is <=1, regardless of whatever
        // GenItemHolder::splitSize still holds from a PREVIOUSLY selected,
        // DIFFERENT, stackable item. Without this guard,
        // ResolveBuyQuantity's GetObjectSplitSize(item.ItemGuid, selected,
        // stackSize) call trivially returns the live Value for ANY selected
        // item (item.ItemGuid always equals the selection guid at this call
        // site) -- leaking a stale quantity into a non-stack purchase.
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
        });
        // Simulate a stale slider left over from a PREVIOUSLY selected,
        // different, stackable item -- this harness doesn't mount
        // SelectedObjectController, which in production would already have
        // reset the slider on selecting the (non-stack) armor; seeding it
        // directly here proves the clamp doesn't depend on that reset
        // having run.
        h.SplitQuantity.Reset(50u, initialValue: 30u);

        h.BuyButton.OnClick!.Invoke();

        Assert.Equal(1, h.Buys.Single().Amount);
    }

    [Fact]
    public void BuyButton_Press_AlternateCurrencyVendor_ForwardsTheVendorsTradeWcid()
    {
        var h = new Harness();
        h.State.Apply(
            VendorGuid,
            Profile(altCurrency: 0x12345678u, altName: "Trade Notes", altAmount: 500u),
            new[]
            {
                new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
            });

        h.BuyButton.OnClick!.Invoke();

        Assert.Equal(0x12345678u, h.Buys.Single().AlternateCurrencyId);
    }

    [Fact]
    public void BuyButton_DisablesTheInstantAPurchaseIsInFlight_AndReenablesOnCompletion()
    {
        var h = new Harness();
        h.State.Apply(VendorGuid, Profile(), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
        });
        Assert.True(h.BuyButton.Enabled);

        h.BuyButton.OnClick!.Invoke();

        // TryBuy's reservation increments BusyCount synchronously, before
        // any wire response — the button must reflect that immediately,
        // with no per-frame polling (ItemInteractionController.StateChanged
        // drives RecomputeBuyButtonEnabled).
        Assert.False(h.BuyButton.Enabled);

        h.ItemInteraction.CompleteUse(0);

        Assert.True(h.BuyButton.Enabled);
    }

    [Fact]
    public void BuyButton_NoSelection_PressDoesNothing()
    {
        var h = new Harness();

        h.BuyButton.OnClick!.Invoke();

        Assert.Empty(h.Buys);
    }

    [Fact]
    public void ReconciliationRoundTrip_MoneyCreateObjectAndApproachVendorRefresh_FlowThroughExistingMachinery()
    {
        // Slice 6.3: verifies the loop end-to-end with synthetic inbound
        // messages, adding no new owner (research doc §C.4/§A.2 point 4):
        // (1) a money property update applies to the SAME ClientObjectTable
        //     the vendor panel reads live for its cost text,
        // (2) the purchase lands in the player's inventory via the ordinary
        //     CreateObject merge-upsert (ClientObjectTable.Ingest),
        // (3) the vendor's post-buy ApproachVendor refresh
        //     (VendorStateTransitionKind.Refreshed) rebuilds the panel —
        //     here the bought-out item leaves the vendor's stock entirely
        //     (the common single-item-purchase case), so the rebuild is
        //     externally observable: the item leaves the list and the
        //     selection/buttons clear.
        var h = new Harness();
        const uint PurchasedItemGuid = 0x60000900u;
        h.State.Apply(VendorGuid, Profile(sellRate: 1.0f), new[]
        {
            new VendorShopItem(ArmorItemGuid, -1, 2u, "Chainmail", (uint)ItemType.Armor, 200u, 500),
        });
        Assert.Equal(1, h.ItemList.GetNumUIItems());
        Assert.True(h.BuyButton.Enabled);

        h.BuyButton.OnClick!.Invoke();
        Assert.Single(h.Buys);
        Assert.False(h.BuyButton.Enabled);

        // (1) Money: PrivateUpdatePropertyInt(CoinValue) — the exact path
        // ObjectTableWiring's PlayerIntPropertyUpdated handler calls.
        int newCoinValue = Harness.DefaultPlayerCoinValue - 500;
        h.Objects.UpdateIntProperty(Harness.PlayerGuid, (uint)PropertyInt.CoinValue, newCoinValue);

        // (2) CreateObject: the purchased item lands in the player's own
        // inventory — the ordinary Ingest merge-upsert every CreateObject
        // uses (ObjectTableWiring.ApplyEntitySpawn), landing here with the
        // player as its container.
        h.Objects.Ingest(new WeenieData(
            Guid: PurchasedItemGuid,
            Name: "Chainmail",
            Type: ItemType.Armor,
            WeenieClassId: 2u,
            IconId: 200u,
            IconOverlayId: 0u,
            IconUnderlayId: 0u,
            Effects: 0u,
            Value: 500,
            StackSize: null,
            StackSizeMax: null,
            Burden: null,
            ContainerId: Harness.PlayerGuid,
            WielderId: 0u,
            ValidLocations: null,
            CurrentWieldedLocation: null,
            Priority: null,
            ItemsCapacity: null,
            ContainersCapacity: null,
            Structure: null,
            MaxStructure: null,
            Workmanship: null));

        // (3) ApproachVendor refresh: sold out of the ONLY armor stack, so
        // the SAME vendor's next snapshot no longer lists it.
        h.State.Apply(VendorGuid, Profile(sellRate: 1.0f), System.Array.Empty<VendorShopItem>());

        // (4) UseDone completes the reservation.
        h.ItemInteraction.CompleteUse(0);

        Assert.Equal(newCoinValue, h.Objects.Get(Harness.PlayerGuid)?.Properties.GetInt((uint)PropertyInt.CoinValue));
        Assert.Equal(Harness.PlayerGuid, h.Objects.Get(PurchasedItemGuid)?.ContainerId);
        Assert.Equal(0, h.ItemList.GetNumUIItems());
        Assert.Equal(string.Empty, GetText(h.ItemNameText));
        Assert.False(h.BuyButton.Enabled);
    }
}