using System.Linq;
using System.Numerics;
using AcDream.App.Rendering;
using AcDream.App.Rendering.Gpu;
using AcDream.App.Tests.Rendering.Gpu;
using AcDream.App.UI;
using AcDream.App.UI.Layout;

namespace AcDream.App.Tests.UI;

/// <summary>
/// Campaign CT slice CT-GF1: mechanism-level tests for the client-wide retained-UI
/// ancestor clip (<see cref="UiElement.ClipsChildren"/>'s new default-true, porting
/// retail's <c>UIRegion::DrawHere @0x0069FA30</c> clip-rect-chain intersection) and its
/// one deliberate opt-out (<see cref="UiElement.ExpandsClipForPopup"/>, used by
/// <see cref="UiMenu"/>'s inline-drawn popup). The Titles-page divider gate repro lives
/// in <c>CharacterTitlesControllerTests</c> (the real owner-reported symptom); the chat
/// input-row regression pin lives in <c>ChatLayoutConformanceTests</c>. This file covers
/// the underlying mechanism directly with small synthetic trees.
/// </summary>
public sealed class UiAncestorClipTests
{
    private sealed class TestElement : UiElement { }

    private sealed class NullGpuFrameSource : ICurrentGpuFrameSource
    {
        public IGpuFrame? CurrentFrame => null;
    }

    private static (RecordingGpuDevice device, TextRenderer renderer, UiRenderContext ctx) MakeContext(
        float w, float h)
    {
        var device = new RecordingGpuDevice();
        var renderer = new TextRenderer(device, new NullGpuFrameSource(), "unused");
        renderer.Begin(new Vector2(w, h));
        var ctx = new UiRenderContext(renderer, new Vector2(w, h));
        return (device, renderer, ctx);
    }

    private static bool AnyQuadAt(TextRenderer renderer, System.Func<float, float, bool> predicate)
    {
        foreach (var seg in renderer.DebugSpriteSegmentVerts)
        {
            for (int i = 0; i < seg.Verts.Count / 8; i++)
            {
                if (predicate(seg.Verts[i * 8], seg.Verts[i * 8 + 1]))
                    return true;
            }
        }
        return false;
    }

    /// <summary>
    /// Core mechanism, plain elements (no dat import involved): a child positioned
    /// entirely outside its parent's [0,Width]x[0,Height] rect renders NOTHING — the
    /// retail <c>UIRegion::DrawHere</c> "intersection empty -> skip the subtree" gate
    /// (@0x0069FB8E). A sibling positioned INSIDE the parent still renders normally.
    /// </summary>
    [Fact]
    public void ChildOutsideParentBounds_RendersNothing_SiblingInsideStillRenders()
    {
        var parent = new TestElement { Width = 50f, Height = 50f };
        var outside = new UiSolidSpriteFill
        {
            Left = -100f, Top = -100f, Width = 20f, Height = 20f,
            SpriteId = 7u,
            SpriteResolve = id => (id, 8, 8),
        };
        var inside = new UiSolidSpriteFill
        {
            Left = 5f, Top = 5f, Width = 10f, Height = 10f,
            SpriteId = 9u,
            SpriteResolve = id => (id, 8, 8),
        };
        parent.AddChild(outside);
        parent.AddChild(inside);

        var (_, renderer, ctx) = MakeContext(200f, 200f);
        parent.DrawSelfAndChildren(ctx);

        Assert.DoesNotContain(renderer.DebugSpriteSegmentVerts, s => s.Texture == 7u);
        Assert.Contains(renderer.DebugSpriteSegmentVerts, s => s.Texture == 9u);
    }

    /// <summary>
    /// A child straddling the parent's edge is clipped to the visible sliver, not
    /// culled outright and not drawn full-size — the intersected rect
    /// <c>UIRegion::DrawHere</c> passes to <c>DrawSelf</c>.
    /// </summary>
    [Fact]
    public void ChildStraddlingParentEdge_ClipsToTheVisibleSliver()
    {
        var parent = new TestElement { Width = 50f, Height = 50f };
        var straddling = new UiSolidSpriteFill
        {
            Left = 40f, Top = 10f, Width = 30f, Height = 10f,   // spans x=[40,70), parent ends at 50
            SpriteId = 3u,
            SpriteResolve = id => (id, 8, 8),
        };
        parent.AddChild(straddling);

        var (_, renderer, ctx) = MakeContext(200f, 200f);
        parent.DrawSelfAndChildren(ctx);

        var seg = Assert.Single(renderer.DebugSpriteSegmentVerts, s => s.Texture == 3u);
        float maxX = 0f;
        for (int i = 0; i < seg.Verts.Count / 8; i++)
            maxX = System.MathF.Max(maxX, seg.Verts[i * 8]);
        Assert.True(maxX <= 50.01f, $"clipped quad's rightmost X ({maxX}) must not exceed the parent's edge (50)");
    }

    /// <summary>
    /// Hit-testing gets the SAME default: a point outside the parent's bounds never
    /// reaches a child positioned there, even though the child's own local hit-test
    /// would otherwise accept it (aligning HitTest with the new draw-clip default per
    /// the CT-GF1 plan's point 4).
    /// </summary>
    [Fact]
    public void ChildOutsideParentBounds_IsNeverHit()
    {
        var parent = new TestElement { Width = 50f, Height = 50f };
        var outside = new TestElement { Left = -30f, Top = -30f, Width = 20f, Height = 20f };
        parent.AddChild(outside);

        UiElement? hit = parent.HitTest(-20f, -20f);   // lands inside `outside`'s own local rect

        Assert.Null(hit);
    }

    /// <summary>
    /// CT-GF1's one opt-out: <see cref="UiMenu"/>'s popup (drawn inline via
    /// <c>OnDrawOverlay</c>) must keep escaping its owning window's ancestor clip —
    /// retail's separate top-level popup region, see <see cref="UiElement.ExpandsClipForPopup"/>'s
    /// doc comment and the AD-113 divergence register row. A small window (80x18, the
    /// menu button's own size) sits well below the canvas top; the popup opens UPWARD
    /// (the class default) and must still render there, well outside the window's own
    /// [0,80]x[0,18] rect.
    /// </summary>
    [Fact]
    public void UiMenuPopup_StillRendersOutsideItsOwningWindow_AncestorClipDoesNotCutItOff()
    {
        var root = new TestElement { Width = 200f, Height = 200f };
        var window = new TestElement { Left = 10f, Top = 150f, Width = 80f, Height = 18f };
        var menu = new UiMenu
        {
            Width = 80f,
            Height = 18f,
            Items = new[] { new UiMenu.MenuItem("Row", (object?)null) },
            SpriteResolve = id => (id, 8, 8),
        };
        root.AddChild(window);
        window.AddChild(menu);

        Assert.True(menu.OnEvent(new UiEvent(0, menu, UiEventType.MouseDown, 0, 10, 5)));
        Assert.True(menu.IsOpen);

        // Not wrapped in BeginOverlayLayer/EndOverlayLayer (which UiRoot.DrawCore does
        // in production, routing overlay draws to a SEPARATE buffer with no debug
        // accessor) — the clip mechanism under test is layer-agnostic, so drawing to
        // the normal buffer keeps DebugSpriteSegmentVerts usable here.
        var (_, renderer, ctx) = MakeContext(200f, 200f);
        root.DrawOverlays(ctx);

        // The popup opens upward (bottom touches the button's top, y=0), so its
        // absolute screen top is window.Top(150) minus its own outer height — well
        // above window.Top. Assert at least one popup quad renders strictly above the
        // owning window's own top edge, i.e. outside window's [0,18] local rect.
        bool escapedAboveWindow = AnyQuadAt(renderer, (_, y) => y < 150f - 0.5f);
        Assert.True(
            escapedAboveWindow,
            "expected the open UiMenu popup to render above its owning window's top edge");
    }

    /// <summary>
    /// Companion negative check: with the SAME geometry but the popup left CLOSED, no
    /// quad renders above the window at all — proving the escape above is specifically
    /// about the OPEN popup's content, not a blanket unclipped draw for the whole menu.
    /// </summary>
    [Fact]
    public void UiMenuClosed_NothingRendersAboveItsOwningWindow()
    {
        var root = new TestElement { Width = 200f, Height = 200f };
        var window = new TestElement { Left = 10f, Top = 150f, Width = 80f, Height = 18f };
        var menu = new UiMenu
        {
            Width = 80f,
            Height = 18f,
            Items = new[] { new UiMenu.MenuItem("Row", (object?)null) },
            SpriteResolve = id => (id, 8, 8),
        };
        root.AddChild(window);
        window.AddChild(menu);
        Assert.False(menu.IsOpen);

        // Not wrapped in BeginOverlayLayer/EndOverlayLayer (which UiRoot.DrawCore does
        // in production, routing overlay draws to a SEPARATE buffer with no debug
        // accessor) — the clip mechanism under test is layer-agnostic, so drawing to
        // the normal buffer keeps DebugSpriteSegmentVerts usable here.
        var (_, renderer, ctx) = MakeContext(200f, 200f);
        root.DrawOverlays(ctx);

        Assert.False(AnyQuadAt(renderer, (_, y) => y < 150f - 0.5f));
    }

    /// <summary>
    /// Retail's hover tooltip is the OTHER content this codebase draws "regardless of
    /// tree position" (see <see cref="RetailTooltipPresenter"/>'s class doc): it mounts
    /// its popup as an ordinary <see cref="UiRoot"/> CHILD (a sibling of every window),
    /// not nested inside whatever widget triggered it — so unlike <see cref="UiMenu"/>'s
    /// popup, it needs no <see cref="UiElement.ExpandsClipForPopup"/> opt-out; it was
    /// never inside the triggering window's ancestor-clip subtree to begin with. This
    /// pins that structural invariant survives CT-GF1: hovering a target buried inside
    /// a tiny (20x20) window still mounts and DRAWS the tooltip popup, unclipped by that
    /// window's own bounds.
    /// </summary>
    [Fact]
    public void RetailTooltip_StillRendersOutsideATinyAncestorWindow_BecauseItMountsAtRootLevel()
    {
        const uint popupRootId = 0x900u;
        const uint textChildId = 0x901u;
        const uint popupLayoutDid = 0x21000041u;
        const uint popupBgSprite = 42u;

        ImportedLayout BuildPopup()
        {
            var rootInfo = new ElementInfo
            {
                Id = popupRootId, Type = 3, X = 0, Y = 0, Width = 30, Height = 30,
                TooltipTextChildElementId = textChildId,
            };
            rootInfo.StateMedia[""] = (popupBgSprite, 1);
            var textInfo = new ElementInfo
            {
                Id = textChildId, Type = 12, X = 2, Y = 2, Width = 26, Height = 26,
            };
            return LayoutImporter.BuildFromInfos(
                rootInfo, new[] { textInfo }, id => (id, 8, 8), null);
        }

        var root = new UiRoot { Width = 800f, Height = 600f };
        var presenter = new RetailTooltipPresenter(root, (_, _) => BuildPopup());

        // A tiny "window" ancestor (20x20) hosting the hover target as a nested child.
        // If the tooltip were drawn from INSIDE this subtree, CT-GF1's new default
        // ancestor clip would cut it off — the popup's mouse-anchored position (32px
        // offset per PositionAtMouse) lands well outside a 20x20 rect.
        var window = new TestElement { Left = 5f, Top = 5f, Width = 20f, Height = 20f };
        var target = new TestElement
        {
            Left = 2f, Top = 2f, Width = 10f, Height = 10f,
            AuthoredTooltipEnabled = true,
            AuthoredTooltipText = "Rotate left.",
            AuthoredTooltipRootElementId = popupRootId,
            AuthoredTooltipLayoutDid = popupLayoutDid,
        };
        window.AddChild(target);
        root.AddChild(window);

        root.OnMouseMove(10, 10);   // inside `target`, well inside the 20x20 window
        root.Tick(0.016, 0);
        root.Tick(0.016, root.TooltipDelayMs);

        // Mounted as a UiRoot SIBLING of `window`, not nested inside it.
        UiElement popup = Assert.Single(root.Children, c => c != window);
        Assert.Same(root, popup.Parent);

        var (_, renderer, ctx) = MakeContext(800f, 600f);
        root.DrawSelfAndChildren(ctx);

        Assert.Contains(renderer.DebugSpriteSegmentVerts, s => s.Texture == popupBgSprite);

        presenter.Dispose();
    }

    /// <summary>
    /// CT-GF1 fix round (S4): pins the input half of the popup-escape mechanism the
    /// draw-only tests above only cover visually. A menu mounted inside a SHORT owning
    /// window on a REAL <see cref="UiRoot"/>, opened, has its popup's first row land
    /// well ABOVE the window's own [0,Height) local rect — the escaped region. An
    /// ordinary top-down <see cref="UiRoot.OnMouseDown"/> walk would reject a point
    /// there before ever reaching the menu: the owning `window`'s own
    /// <see cref="UiElement.ClipsChildren"/> default (true, CT-GF1) rejects any
    /// out-of-bounds local coordinate in <see cref="UiElement.HitTest"/> BEFORE
    /// recursing into its children, so the menu's own out-of-bounds
    /// <c>OnHitTest</c> union is never consulted. <c>UiRoot</c>'s <c>PopupHit</c>
    /// routing (#374) is what rescues this: while a popup is registered active, a
    /// press/scroll/<see cref="UiRoot.WantsMouse"/> query is tested directly against
    /// the popup element itself, bypassing the ancestor walk entirely.
    /// </summary>
    [Fact]
    public void EscapedPopupClick_ReachesTheMenu_ThroughAShortOwningWindow()
    {
        var root = new UiRoot { Width = 200f, Height = 200f };
        var window = new TestElement { Left = 10f, Top = 150f, Width = 80f, Height = 18f };
        string? picked = null;
        var menu = new UiMenu
        {
            Width = 80f,
            Height = 18f,
            OpenUpward = true,
            RowsPerColumn = 1,   // one row -> a small, exactly-known popup rect
            Items = new[] { new UiMenu.MenuItem("Row", (object?)"row") },
            SpriteResolve = id => (id, 8, 8),
        };
        menu.OnSelect = p => picked = p as string;
        window.AddChild(menu);
        root.AddChild(window);

        // Open the popup via a REAL click on the button face (screen space).
        root.OnMouseDown(UiMouseButton.Left, 20, 155);
        root.OnMouseUp(UiMouseButton.Left, 20, 155);
        Assert.True(menu.IsOpen);

        // OuterW = ColumnWidth(191) + 2*Border(5) = 201; OuterH = 1*RowHeight(17) +
        // 2*Border(5) = 27. Opens upward from the button's own screen top (150), so
        // the popup spans screen Y = 150-27=123 .. 150 -- strictly above the owning
        // window's own [150,168) rect, i.e. the escaped region.
        const int rowScreenY = 135;   // inside [123,150)
        const int rowScreenX = 60;    // inside [10,211)
        Assert.True(rowScreenY < 150, "sanity: the row must sit above the window's own top edge");

        // Without PopupHit, a plain top-down walk at this point would be rejected by
        // `window`'s own ancestor-clip bounds check before ever reaching the menu --
        // proven directly against the SAME tree/geometry, no popup registered.
        Assert.Null(root.Pick(rowScreenX, rowScreenY));

        // WantsMouse must recognize the escaped popup region too (S4), so a game
        // action does not fire underneath an open dropdown.
        root.OnMouseMove(rowScreenX, rowScreenY);
        Assert.True(root.WantsMouse, "WantsMouse must see the escaped popup through PopupHit");

        root.OnMouseDown(UiMouseButton.Left, rowScreenX, rowScreenY);
        root.OnMouseUp(UiMouseButton.Left, rowScreenX, rowScreenY);

        Assert.Equal("row", picked);
        Assert.False(menu.IsOpen);
    }

    /// <summary>
    /// CT-GF1 fix round (N2): the empty-clip subtree cull added to
    /// <see cref="UiElement.DrawSelfAndChildren"/> (retail's <c>var_24</c> gate,
    /// <c>UIRegion::DrawHere @0x0069FB8E</c>) early-outs once the intersected clip
    /// goes empty -- e.g. a window whose own Width has collapsed to zero.
    /// <see cref="UiElement.DrawOverlays"/> is a wholly SEPARATE traversal (the
    /// second pass <see cref="UiRoot.Draw"/> runs after the main one) that shares no
    /// clip-stack state with the cull above, so an open <see cref="UiMenu"/> popup
    /// nested inside such a window must keep drawing there regardless.
    /// </summary>
    [Fact]
    public void UiMenuPopup_StillDraws_EvenWhenItsOwningWindowIsFullyClippedAway()
    {
        var root = new TestElement { Width = 200f, Height = 200f };
        var window = new TestElement { Left = 10f, Top = 150f, Width = 0f, Height = 18f };
        var menu = new UiMenu
        {
            Width = 80f,
            Height = 18f,
            Items = new[] { new UiMenu.MenuItem("Row", (object?)null) },
            SpriteResolve = id => (id, 8, 8),
        };
        root.AddChild(window);
        window.AddChild(menu);

        Assert.True(menu.OnEvent(new UiEvent(0, menu, UiEventType.MouseDown, 0, 10, 5)));
        Assert.True(menu.IsOpen);

        var (_, renderer, ctx) = MakeContext(200f, 200f);

        // Main pass: `window`'s own zero-width clip is empty -- the cull skips its
        // whole subtree (including the menu's own button face), so nothing draws.
        root.DrawSelfAndChildren(ctx);
        Assert.Empty(renderer.DebugSpriteSegmentVerts);

        // Overlay pass: the SAME open popup still renders -- proves the cull above is
        // scoped to DrawSelfAndChildren and never reaches DrawOverlays.
        root.DrawOverlays(ctx);
        Assert.NotEmpty(renderer.DebugSpriteSegmentVerts);
    }

    /// <summary>
    /// CT7 gate regression (2026-08-25): the MossTank plugin's markup
    /// labels lost ALL text under the completed self-clip — a markup
    /// &lt;label&gt; authors position only, so UiLabel's box was 0x0 and the
    /// element's own clip cropped every glyph. UiLabel now opts out of the
    /// self-clip (its ancestors clip — the retail containment for a text
    /// region whose box hugs its glyphs) and keeps a truthful measured box.
    /// Button captions never regressed because markup buttons author w/h.
    /// </summary>
    [Fact]
    public void UnsizedMarkupLabel_InsideASizedPanel_DoesNotSelfClipItsSubtree()
    {
        var (device, renderer, ctx) = MakeContext(800f, 600f);
        var panel = new UiPanel
        {
            Left = 50f, Top = 50f, Width = 200f, Height = 100f,
            BackgroundColor = default, BorderColor = default,
        };
        // Exactly what MarkupDocument builds for <label x=".." y=".."> —
        // position only, no Width/Height (the box is degenerate at draw
        // time). Pre-fix, UiLabel inherited the ambient self-clip and its
        // 0x0 push cropped everything it painted to nothing — the MossTank
        // vanished-text regression. The mechanism pin below hangs a
        // sprite-drawing probe child under the label: with the self-clip
        // the probe cannot render; with UiLabel's opt-out it must.
        var label = new UiLabel { Left = 10f, Top = 10f, Text = "MossTank status line" };
        var probe = new UiPanel
        {
            Left = 0f, Top = 0f, Width = 100f, Height = 10f,
            BackgroundSprite = 42u,
            SpriteResolve = id => id == 42u ? (42u, 8, 8) : (0u, 0, 0),
            BackgroundColor = default, BorderColor = default,
        };
        label.AddChild(probe);
        panel.AddChild(label);

        panel.DrawSelfAndChildren(ctx);

        Assert.True(
            AnyQuadAt(renderer, (x, y) => x >= 60f && x <= 160f && y >= 60f && y <= 70f),
            "the unsized label self-clipped its subtree away (MossTank regression)");
        // The box became truthful (fallback-measured without a font), not degenerate.
        Assert.True(label.Width > 0f && label.Height > 0f,
            $"label box stayed degenerate: {label.Width}x{label.Height}");
    }
}