using AcDream.App.UI;
using AcDream.App.UI.Layout;

namespace AcDream.App.Tests.UI;

/// <summary>
/// #372 regression: the Options panel's Character/Chat/Config tabs rendered
/// BLANK at the first connected gate while Gameplay (which has no ListBox)
/// worked. Root cause: <see cref="UiTemplateListBox"/> creates its row
/// viewport at 0×0 with Left|Top|Right|Bottom fill-anchors; the anchor
/// baseline captured from that 0-size rect makes
/// <c>ComputeAnchoredRect</c> keep it 0×0 forever (mR=parentW, so
/// w=parentW-mR-mL=0), and <see cref="UiScrollablePanel.LayoutScrollableChildren"/>
/// then culls every row (top+height ≤ 0 is false). These tests pin that the
/// viewport fills its ListBox and the rows stay visible after a layout pass.
/// </summary>
public sealed class UiTemplateListBoxViewportTests
{
    private static UiTemplateListBox MakeListBox(float width, float height)
    {
        // A ListBox element authoring one template entry, sized like the
        // Options-panel Character ListBox (0x100001FA, 276×560 authored).
        var info = new ElementInfo { Id = 0x100001FAu, Type = 5u };
        var box = new UiTemplateListBox(
            info,
            _ => (0u, 0, 0),
            new[] { new UiTemplateListEntry(0x2100002Bu, 0x10000218u) },
            scrollbarElementId: 0x100001FBu)
        {
            Width = width,
            Height = height,
        };
        return box;
    }

    [Fact]
    public void Viewport_FillsTheListBox_NotCollapsedToZero()
    {
        var box = MakeListBox(276f, 560f);
        // Add a couple of rows via the prebuilt path (no DAT needed).
        box.AddPrebuiltRow(new UiText { Width = 260f, Height = 20f });
        box.AddPrebuiltRow(new UiText { Width = 260f, Height = 20f });

        UiScrollablePanel? viewport = box.ViewportForTest;
        Assert.NotNull(viewport);

        // Drive the per-frame layout the draw traversal runs: the parent
        // ListBox re-anchors its children (UiElement.DrawSelfAndChildren
        // line ~500), sizing the fill-anchored viewport.
        viewport!.ApplyAnchor(box.Width, box.Height);

        // The whole point of #372: the viewport must FILL the ListBox, not
        // collapse. Pre-fix this was 0×0.
        Assert.Equal(276f, viewport.Width, 3);
        Assert.Equal(560f, viewport.Height, 3);
    }

    [Fact]
    public void Rows_StayVisible_AfterLayout_WhenTheyFitTheViewport()
    {
        var box = MakeListBox(276f, 560f);
        var row0 = new UiText { Width = 260f, Height = 20f };
        var row1 = new UiText { Width = 260f, Height = 20f };
        var row2 = new UiText { Width = 260f, Height = 20f };
        box.AddPrebuiltRow(row0);
        box.AddPrebuiltRow(row1);
        box.AddPrebuiltRow(row2);

        UiScrollablePanel viewport = box.ViewportForTest!;
        viewport.ApplyAnchor(box.Width, box.Height); // size the viewport
        viewport.LayoutScrollableChildren();          // the cull pass (runs each OnDraw)

        // All three rows sit at y 0/20/40 inside a 560px viewport → visible.
        // Pre-fix the viewport was 0px tall and every row was culled → blank tab.
        Assert.True(row0.Visible, "row 0 culled — the #372 blank-tab bug");
        Assert.True(row1.Visible, "row 1 culled — the #372 blank-tab bug");
        Assert.True(row2.Visible, "row 2 culled — the #372 blank-tab bug");
    }
}