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");
    }

    /// <summary>
    /// #412-class regression (2026-08-16, overnight hover/UI round, Batch A bug
    /// 2): the Options panel's Config tab escaped past the window frame — the
    /// footer sitting mid-panel with further rows drawing below the window's
    /// bottom edge. #372's own fixture above never exercises this because
    /// <see cref="MakeListBox"/> gives the ListBox no parent — its own size
    /// never changes after the viewport is seeded. The real Options mount is
    /// different: this ListBox is itself a DAT-imported <see cref="UiElement"/>
    /// carrying a real <see cref="UiLayoutPolicy"/> from its authored parent
    /// (the Config page slot), and a page controller's Bind — which lazily
    /// creates this viewport — runs BEFORE the tree's first draw frame, i.e.
    /// before the ListBox has ever shrunk to fit its actual (smaller than
    /// authored) container. This reproduces that ordering with a real
    /// LayoutPolicy-driven parent standing in for the page slot.
    /// </summary>
    [Fact]
    public void Viewport_TracksTheListBox_WhenTheListBoxItselfShrinksOnFirstLayout()
    {
        // A stand-in for the Config page slot: authored 298×575 against an
        // authored 300×600 design canvas (live-DAT-measured values), but its
        // real mounted container is only 300×362 — exactly retail's
        // UIElement::UpdateForParentSizeChange four-edge policy (L=T=R=B=1,
        // "preserve original margin on every edge").
        var slotPolicy = new UiLayoutPolicy(
            leftMode: 1, topMode: 1, rightMode: 1, bottomMode: 1,
            originalChild: UiPixelRect.FromPositionAndSize(2, 25, 298, 575),
            originalParent: UiPixelRect.FromPositionAndSize(0, 0, 300, 600));
        var slot = new UiPanel
        {
            Left = 2, Top = 25, Width = 298, Height = 575,
            LayoutPolicy = slotPolicy,
        };
        var root = new UiPanel { Width = 300, Height = 362 };
        root.AddChild(slot);

        // The ListBox itself ALSO carries a real LayoutPolicy (live-DAT
        // measured: authored 276×560 against the slot's own 298×575 design
        // extent) — this is what shrinks it out from under the viewport.
        var box = MakeListBox(276f, 560f);
        var listBoxPolicy = new UiLayoutPolicy(
            leftMode: 1, topMode: 1, rightMode: 1, bottomMode: 1,
            originalChild: UiPixelRect.FromPositionAndSize(0, 0, 276, 560),
            originalParent: UiPixelRect.FromPositionAndSize(0, 0, 298, 575));
        box.LayoutPolicy = listBoxPolicy;
        slot.AddChild(box);

        // Seed the viewport with rows BEFORE any layout pass has ever run —
        // exactly ConfigOptionsPageController.Bind's own ordering (it runs
        // before RetailWindowFrame.Mount's first draw frame).
        box.AddPrebuiltRow(new UiText { Width = 260f, Height = 20f });
        UiScrollablePanel viewport = box.ViewportForTest!;

        // Drive ONE simulated draw-frame's top-down ApplyAnchor walk — the
        // SAME order DrawSelfAndChildren runs every frame: parent before
        // children, all the way down.
        slot.ApplyAnchor(root.Width, root.Height);   // slot shrinks: 575 -> ~337
        box.ApplyAnchor(slot.Width, slot.Height);    // listbox shrinks: 560 -> ~297 (still ahead of the viewport)
        viewport.ApplyAnchor(box.Width, box.Height); // the viewport's FIRST EVER ApplyAnchor call

        // Pre-fix: the viewport's legacy anchor baseline captured a NEGATIVE
        // bottom margin against the ALREADY-SHRUNK ListBox (parentH(~297) -
        // (0+560) < 0), which ComputeAnchoredRect's stretch math preserves
        // forever — the viewport stayed locked at its original 560px height,
        // clipping rows to a bound retail never actually gave it on screen.
        Assert.Equal(box.Height, viewport.Height, 3);
        Assert.True(
            viewport.Height < 400f,
            $"viewport height {viewport.Height} did not shrink with its ListBox "
                + "(560 == the pre-fix stale-capture bug)");
    }
}