using System;
using System.Globalization;
using System.Numerics;
using System.Reflection;
using System.Xml.Linq;
using AcDream.Plugin.Abstractions;

namespace AcDream.App.UI;

/// <summary>
/// Parses our KSML-style panel markup (mirrors retail's ElementDesc fields)
/// into a live <see cref="UiElement"/> subtree. <c>{Binding}</c> attribute
/// values resolve against a supplied object by property name (reflection).
/// This is the format the future LayoutDesc importer will emit. See D.2b spec §7.
/// </summary>
public static class MarkupDocument
{
    // Retail's generic runtime-text tooltip skin. Plugin controls have no
    // LayoutDesc of their own, so a tooltip= attribute explicitly opts them
    // into the same popup that game-code SetTooltip call sites use.
    private const uint RuntimeTooltipRootElementId = 0x10000397u;
    private const uint RuntimeTooltipLayoutDid = 0x21000041u;

    /// <param name="xml">Raw XML markup for a single panel.</param>
    /// <param name="binding">Object whose public properties are bound to <c>{PropName}</c> attributes.</param>
    /// <param name="resolve">Surface id → (GL handle, width, height) for chrome sprites.</param>
    /// <param name="style">Optional controls.ini stylesheet for the title color.</param>
    /// <param name="datFont">
    /// Retail interface font. Supplied by the host so plugin panels render
    /// their text through the same glyph path as authored panels; without it
    /// they fall back to the development bitmap font and look foreign.
    /// </param>
    /// <param name="icons">
    /// Slice B (<c>docs/plans/2026-09-06-plugin-shelf-and-dat-icons.md</c>):
    /// resolves <c>&lt;icon&gt;</c>, <c>&lt;button icon&gt;</c>, and
    /// <c>&lt;list icons&gt;</c> ids to drawable DAT icons. Null (the
    /// default, and what every pre-Slice-B caller still passes) makes those
    /// three surfaces resolve to nothing rather than throwing — a panel
    /// authored against Slice B markup still loads under a host/test that
    /// has not wired icon resolution.
    /// </param>
    public static UiNineSlicePanel Build(
        string xml, object binding, Func<uint, (uint, int, int)> resolve,
        ControlsIni? style = null, UiDatFont? datFont = null,
        IMarkupIconResolver? icons = null)
    {
        var root = XDocument.Parse(xml).Root ?? throw new FormatException("empty markup");
        if (root.Name.LocalName != "panel")
            throw new FormatException($"root must be <panel>, got <{root.Name.LocalName}>");

        var panel = new UiNineSlicePanel(resolve)
        {
            Left   = F(root, "x"),
            Top    = F(root, "y"),
            Width  = F(root, "w"),
            Height = F(root, "h"),
        };

        // Optional per-window resize-axis lock: resize="x" | "y" | "both" | "none".
        string? resize = (string?)root.Attribute("resize");
        if (resize is not null)
        {
            panel.ResizeX = resize is "x" or "both";
            panel.ResizeY = resize is "y" or "both";
        }

        // Panel-level visibility binding: lets a plugin keep its window out of
        // the way until it has something to act on (e.g. hidden at character
        // select, shown in world).
        string? visible = (string?)root.Attribute("visible");
        if (visible is not null && IsBinding(visible))
        {
            PropertyInfo? flag = binding.GetType().GetProperty(visible[1..^1]);
            if (flag is null || flag.PropertyType != typeof(bool))
            {
                throw new FormatException(
                    $"<panel visible=\"{visible}\"> did not resolve to a bool property "
                    + $"on {binding.GetType().Name}");
            }
            panel.VisibleSource = () => flag.GetValue(binding) is true;
        }

        string? title = (string?)root.Attribute("title");
        if (!string.IsNullOrEmpty(title))
        {
            Vector4 tc = style is not null && style.TryColor("title", "color", out var c) ? c : Vector4.One;
            panel.AddChild(new UiLabel
            {
                Text = title, Left = 8, Top = 4, TextColor = tc, DatFont = datFont,
            });
        }

        foreach (var el in root.Elements())
            AddElement(panel, el, binding, resolve, datFont, icons);
        return panel;
    }

    private static void AddElement(
        UiElement parent,
        XElement el,
        object binding,
        Func<uint, (uint, int, int)> resolve,
        UiDatFont? datFont,
        IMarkupIconResolver? icons)
    {
        switch (el.Name.LocalName)
        {
            case "group":
                var group = new UiPanel
                {
                    Left = F(el, "x"),
                    Top = F(el, "y"),
                    Width = F(el, "w"),
                    Height = F(el, "h"),
                    BackgroundColor = el.Attribute("background") is null
                        ? Vector4.Zero
                        : Color((string?)el.Attribute("background")),
                    BorderColor = el.Attribute("border") is null
                        ? Vector4.Zero
                        : Color((string?)el.Attribute("border")),
                    BorderThickness = el.Attribute("border") is null ? 0f : 1f,
                    // Transparent layout groups do not claim empty space, while
                    // their interactive descendants remain hittable.
                    ClickThrough = true,
                };
                ApplyCommon(group, el, binding);
                parent.AddChild(group);
                foreach (XElement child in el.Elements())
                    AddElement(group, child, binding, resolve, datFont, icons);
                break;

            case "meter":
                    var cur = BindUint((string?)el.Attribute("cur"), binding);
                    var max = BindUint((string?)el.Attribute("max"), binding);
                    var meter = new UiMeter
                    {
                        Left          = F(el, "x"),
                        Top           = F(el, "y"),
                        Width         = F(el, "w"),
                        Height        = F(el, "h"),
                        BarColor      = Color((string?)el.Attribute("color")),
                        Fill          = BindFloat((string?)el.Attribute("fill"), binding),
                        Label         = () => (cur(), max()) is (uint c, uint m) ? $"{c}/{m}" : null,
                        Anchors       = Anchor((string?)el.Attribute("anchor")),
                        SpriteResolve = resolve,
                        BackLeft      = Hex((string?)el.Attribute("backleft")),
                        BackTile      = Hex((string?)el.Attribute("backtile")),
                        BackRight     = Hex((string?)el.Attribute("backright")),
                        FrontLeft     = Hex((string?)el.Attribute("frontleft")),
                        FrontTile     = Hex((string?)el.Attribute("fronttile")),
                        FrontRight    = Hex((string?)el.Attribute("frontright")),
                    };
                    ApplyCommon(meter, el, binding);
                    parent.AddChild(meter);
                    break;

            case "label":
                    // Text may be a literal or a {Binding}. Bound labels re-read
                    // their property every frame through the Func, so a plugin
                    // updates its status line by assigning a property rather
                    // than by touching UI objects from its own thread.
                    var label = new UiLabel
                    {
                        Left = F(el, "x"),
                        Top = F(el, "y"),
                        TextSource = BindString((string?)el.Attribute("text"), binding),
                        DatFont = datFont,
                    };
                    if (el.Attribute("color") is not null)
                        label.TextColor = Color((string?)el.Attribute("color"));
                    ApplyCommon(label, el, binding);
                    parent.AddChild(label);
                    break;

            case "button":
                    // onclick binds to an Action property on the binding
                    // object. Resolved once at build time: a button whose
                    // handler silently failed to bind is a bug worth failing
                    // loudly for, and MarkupDocument.Build is already inside
                    // the host's try/catch that reports panel load failures.
                    string? clickName = (string?)el.Attribute("onclick");
                    Action? onClick = BindAction(clickName, binding);
                    if (clickName is not null && onClick is null)
                    {
                        throw new FormatException(
                            $"<button onclick=\"{clickName}\"> did not resolve to an "
                            + $"Action property on {binding.GetType().Name}");
                    }
                    // UiSimpleButton, not the dat-sprite UiButton: a plugin
                    // panel has no LayoutDesc behind it and no StateDesc
                    // sprites to name, so the plain rect-and-text button is the
                    // one that can actually render from markup alone.
                    var button = new UiSimpleButton
                    {
                        Left = F(el, "x"),
                        Top = F(el, "y"),
                        Width = F(el, "w"),
                        Height = F(el, "h"),
                        Text = (string?)el.Attribute("text") ?? string.Empty,
                        DatFont = datFont,
                    };
                    // A bound caption lets the button re-label itself (Buff /
                    // Stop) from the same binding object.
                    string? caption = (string?)el.Attribute("text");
                    if (caption is not null && IsBinding(caption))
                        button.TextSource = BindString(caption, binding);
                    if (el.Attribute("color") is not null)
                        button.TextColor = Color((string?)el.Attribute("color"));
                    if (el.Attribute("background") is not null)
                        button.BackgroundColor = Color(
                            (string?)el.Attribute("background"));
                    if (el.Attribute("border") is not null)
                        button.BorderColor = Color(
                            (string?)el.Attribute("border"));
                    // Slice B: <button icon="..." iconkind="did|spell|item">.
                    // Review fix round finding 4: the iconkind literal is
                    // validated here regardless of whether a resolver is
                    // wired — a typo like iconkind="spel" must throw at
                    // Build on every host, not only ones with icon support
                    // turned on. Finding 7: IconSource is only ASSIGNED when
                    // a resolver exists — UiSimpleButton now reserves its
                    // icon column whenever IconSource is non-null (see
                    // UiPanel.cs), so setting it to an always-empty func on
                    // an icons:null host would permanently reserve a column
                    // that never draws anything.
                    string? buttonIcon = (string?)el.Attribute("icon");
                    if (buttonIcon is not null)
                    {
                        string? buttonIconKind = (string?)el.Attribute("iconkind");
                        ValidateIconKind(buttonIconKind);
                        // Residual round finding N2: BindUintLiteralOrBinding
                        // must run UNCONDITIONALLY — same rule as
                        // ValidateIconKind just above — so a malformed
                        // icon="{Typo}" throws FormatException at Build on
                        // every host, not only ones with icons wired. Only
                        // the ASSIGNMENT onto button.IconSource stays gated
                        // on icons is not null (finding 7: an always-empty
                        // IconSource would permanently reserve the icon
                        // column on a resolver-less host).
                        Func<uint> buttonIconReader =
                            BindUintLiteralOrBinding(buttonIcon, binding, "button icon");
                        if (icons is not null)
                        {
                            button.IconSource = BuildIconSource(
                                buttonIconKind,
                                buttonIconReader,
                                icons);
                        }
                    }
                    ApplyCommon(button, el, binding);
                    if (onClick is not null)
                        button.Click += onClick;
                    parent.AddChild(button);
                    break;

            case "icon":
                {
                    // Residual round finding N7: unlike <button>/<list>,
                    // <icon> derives its kind from WHICH of did/spell/item is
                    // set (below) — iconkind is meaningless here and was
                    // previously silently ignored (a plugin author's
                    // iconkind="spell" typo on an <icon did="..."> would
                    // never do what it looked like it did). Reject it
                    // loudly instead, same "malformed markup throws at
                    // Build" rule every other attribute in this grammar
                    // follows.
                    if (el.Attribute("iconkind") is not null)
                    {
                        throw new FormatException(
                            "iconkind applies to button and list; icon derives its kind from did/spell/item");
                    }

                    string? didAttr = (string?)el.Attribute("did");
                    string? spellAttr = (string?)el.Attribute("spell");
                    string? itemAttr = (string?)el.Attribute("item");
                    int sourceCount = (didAttr is not null ? 1 : 0)
                        + (spellAttr is not null ? 1 : 0)
                        + (itemAttr is not null ? 1 : 0);
                    if (sourceCount != 1)
                    {
                        throw new FormatException(
                            "<icon> requires exactly one of did/spell/item");
                    }

                    string iconKind = didAttr is not null ? "did"
                        : spellAttr is not null ? "spell"
                        : "item";
                    string iconExpression = didAttr ?? spellAttr ?? itemAttr!;
                    Func<uint> iconReader = BindUintLiteralOrBinding(
                        iconExpression, binding, $"icon {iconKind}");
                    var icon = new UiMarkupIcon
                    {
                        Left = F(el, "x"),
                        Top = F(el, "y"),
                        Width = FOr(el, "w", 32f),
                        Height = FOr(el, "h", 32f),
                        IconSource = BuildIconSource(iconKind, iconReader, icons),
                    };
                    ApplyCommon(icon, el, binding);
                    // A tooltip needs this element to be a real hit-test
                    // target — see UiMarkupIcon's own doc comment. Review fix
                    // round finding 9: an EMPTY tooltip="" must not swallow
                    // clicks either — match ApplyCommon's own
                    // !IsNullOrWhiteSpace predicate rather than a bare
                    // attribute-presence check.
                    string? iconTooltip = (string?)el.Attribute("tooltip");
                    if (!string.IsNullOrWhiteSpace(iconTooltip))
                        icon.ClickThrough = false;
                    parent.AddChild(icon);
                    break;
                }

            case "tab":
                string? tabClickName = (string?)el.Attribute("onclick");
                Action? tabClick = BindAction(tabClickName, binding);
                if (tabClickName is not null && tabClick is null)
                {
                    throw new FormatException(
                        $"<tab onclick=\"{tabClickName}\"> did not resolve to an "
                        + $"Action property on {binding.GetType().Name}");
                }

                var tab = new UiMarkupTabButton
                {
                    Left = F(el, "x"),
                    Top = F(el, "y"),
                    Width = F(el, "w"),
                    Height = F(el, "h"),
                    Text = (string?)el.Attribute("text") ?? string.Empty,
                    DatFont = datFont,
                    SelectedSource = BindRequiredBoolReader(
                        (string?)el.Attribute("selected"),
                        binding,
                        "tab selected"),
                };
                ApplyCommon(tab, el, binding);
                if (tabClick is not null)
                    tab.Click += tabClick;
                parent.AddChild(tab);
                break;

            case "toggle":
                string? toggleClickName = (string?)el.Attribute("onclick");
                Action? toggleClick = BindAction(toggleClickName, binding);
                if (toggleClickName is not null && toggleClick is null)
                {
                    throw new FormatException(
                        $"<toggle onclick=\"{toggleClickName}\"> did not resolve to an "
                        + $"Action property on {binding.GetType().Name}");
                }

                string? toggleCaption = (string?)el.Attribute("text");
                var toggle = new UiMarkupToggle
                {
                    Left = F(el, "x"),
                    Top = F(el, "y"),
                    Width = F(el, "w"),
                    Height = F(el, "h"),
                    Text = toggleCaption ?? string.Empty,
                    TextSource = BindString(toggleCaption, binding),
                    CheckedSource = BindRequiredBoolReader(
                        (string?)el.Attribute("checked"),
                        binding,
                        "toggle checked"),
                    DatFont = datFont,
                    Toggle = toggleClick,
                };
                if (el.Attribute("color") is not null)
                    toggle.TextColor = Color((string?)el.Attribute("color"));
                ApplyCommon(toggle, el, binding);
                parent.AddChild(toggle);
                break;

            case "slider":
                string? changeName = (string?)el.Attribute("onchange");
                Action<float>? changed = BindFloatAction(changeName, binding);
                if (changeName is not null && changed is null)
                {
                    throw new FormatException(
                        $"<slider onchange=\"{changeName}\"> did not resolve to an "
                        + $"Action<float> property on {binding.GetType().Name}");
                }

                var slider = new UiScrollbar
                {
                    Left = F(el, "x"),
                    Top = F(el, "y"),
                    Width = F(el, "w"),
                    Height = F(el, "h"),
                    Horizontal = true,
                    SpriteResolve = resolve,
                    ScalarPositionSource = BindFloat(
                        (string?)el.Attribute("value"),
                        binding),
                    ScalarChanged = changed,
                };
                RetailScrollbarChrome.ApplyHorizontal(slider);
                ApplyCommon(slider, el, binding);
                parent.AddChild(slider);
                break;

            case "field":
                string? fieldChangeName = (string?)el.Attribute("onchange");
                Action<string>? fieldChanged = BindStringAction(
                    fieldChangeName,
                    binding);
                if (fieldChangeName is not null && fieldChanged is null)
                {
                    throw new FormatException(
                        $"<field onchange=\"{fieldChangeName}\"> did not resolve to an "
                        + $"Action<string> property on {binding.GetType().Name}");
                }
                string? submitName = (string?)el.Attribute("onsubmit");
                Action<string>? submitted = BindStringAction(submitName, binding);
                if (submitName is not null && submitted is null)
                {
                    throw new FormatException(
                        $"<field onsubmit=\"{submitName}\"> did not resolve to an "
                        + $"Action<string> property on {binding.GetType().Name}");
                }

                var field = new UiField
                {
                    Left = F(el, "x"),
                    Top = F(el, "y"),
                    Width = F(el, "w"),
                    Height = F(el, "h"),
                    DatFont = datFont,
                    BackgroundColor = el.Attribute("background") is null
                        ? new Vector4(0f, 0f, 0f, 0.9f)
                        : Color((string?)el.Attribute("background")),
                    TextColor = el.Attribute("color") is null
                        ? new Vector4(0.91f, 0.87f, 0.76f, 1f)
                        : Color((string?)el.Attribute("color")),
                    MaxCharacters = Math.Max(1, I(el, "maxlength", 128)),
                    ClearOnSubmit = B(el, "clearonsubmit", false),
                    RecordHistory = false,
                    OnTextChanged = fieldChanged,
                    OnSubmit = submitted,
                };
                field.SetText(BindString((string?)el.Attribute("text"), binding)());
                ApplyCommon(field, el, binding);
                parent.AddChild(field);
                break;

            case "menu":
                string? menuChangeName = (string?)el.Attribute("onchange");
                Action<string>? menuChanged = BindStringAction(
                    menuChangeName,
                    binding);
                if (menuChangeName is not null && menuChanged is null)
                {
                    throw new FormatException(
                        $"<menu onchange=\"{menuChangeName}\"> did not resolve to an "
                        + $"Action<string> property on {binding.GetType().Name}");
                }
                Func<IReadOnlyList<string>> menuItems = BindStringList(
                    (string?)el.Attribute("items"),
                    binding,
                    "menu items");
                Func<string?> menuSelected = BindString(
                    (string?)el.Attribute("selected"),
                    binding);
                bool menuRetailButtonArt = ValidateMenuStyle((string?)el.Attribute("style"));
                var menu = new UiMenu
                {
                    Left = F(el, "x"),
                    Top = F(el, "y"),
                    Width = F(el, "w"),
                    Height = F(el, "h"),
                    DatFont = datFont,
                    SpriteResolve = resolve,
                    RowsPerColumn = Math.Max(1, I(el, "rows", 7)),
                    RowHeight = Math.Max(12f, FOr(el, "rowheight", 18f)),
                    ColumnWidth = Math.Max(20f, F(el, "w")),
                    OpenUpward = B(el, "openupward", false),
                    TextIndent = 6f,
                    ButtonTextIndent = 6f,
                    NormalSprite = 0x06004D65u,
                    PressedSprite = 0x06004D66u,
                    PopupBgSprite = 0x0600124Cu,
                    ItemNormalSprite = 0x0600124Eu,
                    ItemHighlightSprite = 0x0600124Du,
                    RetailButtonArt = menuRetailButtonArt,
                    // Owner live-client report 2026-09-07: a plugin dropdown
                    // scrolls a single column (VTank's own HudCombo shape)
                    // rather than wrapping into more grid columns once it
                    // overflows its "rows" window; the scrollbar itself is
                    // hidden entirely (0x79 semantics) while everything
                    // fits, matching retail's vendor category popup.
                    Scrollable = true,
                    PopupScrollbarHideWhenDisabled = true,
                    ButtonLabelProvider = () => menuSelected() ?? string.Empty,
                    OnSelect = payload =>
                    {
                        if (payload is string value)
                            menuChanged?.Invoke(value);
                    },
                };
                // The popup's own scrollbar always draws retail's chrome —
                // "we use the same assets as we do in for example chat or
                // inventory window" — regardless of RetailButtonArt (the
                // owner's earlier plain-row directive only ever covered the
                // ROWS, never this bar).
                RetailScrollbarChrome.ApplyToMenuPopup(menu);
                void RefreshMenu()
                {
                    menu.Items = menuItems()
                        .Select(static value => new UiMenu.MenuItem(value, value))
                        .ToArray();
                    menu.Selected = menuSelected();
                }
                RefreshMenu();
                menu.BeforeOpen = RefreshMenu;
                ApplyCommon(menu, el, binding);
                parent.AddChild(menu);
                break;

            case "list":
                string? listChangeName = (string?)el.Attribute("onchange");
                Action<int>? listChanged = BindIntAction(listChangeName, binding);
                if (listChangeName is not null && listChanged is null)
                {
                    throw new FormatException(
                        $"<list onchange=\"{listChangeName}\"> did not resolve to an "
                        + $"Action<int> property on {binding.GetType().Name}");
                }

                // Campaign VT slice 1 Part B: <list><column .../></list>
                // (docs/research/vtank-kb/08-ui-views.md §3). A non-<column>
                // child is always malformed — the element previously had no
                // children at all, so this is purely additive.
                var listChildren = el.Elements().ToList();
                foreach (var child in listChildren)
                {
                    if (child.Name.LocalName != "column")
                    {
                        throw new FormatException(
                            $"<list> children must all be <column>, got <{child.Name.LocalName}>");
                    }
                }
                bool listUsesColumns = listChildren.Count > 0;
                if (listUsesColumns
                    && (el.Attribute("items") is not null
                        || el.Attribute("icons") is not null
                        || el.Attribute("colors") is not null))
                {
                    throw new FormatException(
                        "<list> with <column> children cannot also use the "
                        + "items/icons/colors attributes (Slice B's own single-column "
                        + "form) — express every row source as a <column> instead");
                }

                var list = new UiMarkupList
                {
                    Left = F(el, "x"),
                    Top = F(el, "y"),
                    Width = F(el, "w"),
                    Height = F(el, "h"),
                    RowHeight = Math.Max(12f, FOr(el, "rowheight", 18f)),
                    DatFont = datFont,
                    // Owner live-client report 2026-09-07: an overflowing
                    // <list> draws the same retail scrollbar chrome the chat
                    // window and inventory use — resolved through the same
                    // sprite resolver every other markup sink already uses.
                    SpriteResolve = resolve,
                    SelectedIndexSource = BindRequiredIntReader(
                        (string?)el.Attribute("selected"),
                        binding,
                        "list selected"),
                    SelectionChanged = listChanged,
                };

                if (listUsesColumns)
                {
                    int lastColumnIndex = listChildren.Count - 1;
                    list.Columns = listChildren
                        .Select((columnEl, index) => BuildListColumn(
                            columnEl, binding, icons, index, index == lastColumnIndex))
                        .ToList();
                }
                else
                {
                    list.ItemsSource = BindStringList(
                        (string?)el.Attribute("items"),
                        binding,
                        "list items");
                    list.ItemColorsSource = BindUintList(
                        (string?)el.Attribute("colors"),
                        binding,
                        "list colors");
                    // Slice B: <list icons="{IconIds}" iconkind="did|spell|item">.
                    // Same two rules as <button icon> above: iconkind validates
                    // regardless of resolver wiring (finding 4), and
                    // IconIdsSource/IconResolve are only set when a resolver
                    // exists (finding 7) — UiMarkupList already reserves its
                    // icon column whenever IconIdsSource is non-null.
                    string? listIcons = (string?)el.Attribute("icons");
                    if (!string.IsNullOrWhiteSpace(listIcons))
                    {
                        string? listIconKind = (string?)el.Attribute("iconkind");
                        ValidateIconKind(listIconKind);
                        // Residual round finding N2: same rule as the button's
                        // icon reader above — BindUintList must run
                        // UNCONDITIONALLY so icons="notabinding" (a malformed,
                        // non-{Binding} literal — list icons has no literal
                        // grammar) throws FormatException at Build even with no
                        // resolver wired. Only the assignment stays gated.
                        Func<IReadOnlyList<uint>> listIconIdsReader =
                            BindUintList(listIcons, binding, "list icons");
                        if (icons is not null)
                        {
                            list.IconIdsSource = listIconIdsReader;
                            list.IconResolve = BuildRowIconResolve(listIconKind, icons);
                        }
                    }
                }
                ApplyCommon(list, el, binding);
                parent.AddChild(list);
                break;

            default:
                // Review fix round finding 11: an unknown or miscased
                // element name previously vanished silently (the switch had
                // no default arm) — the same "malformed markup throws at
                // Build" rule every other element already follows.
                throw new FormatException($"unknown element <{el.Name.LocalName}>");
        }
    }

    /// <summary>
    /// Review fix round finding 4: validates an <c>iconkind</c> attribute
    /// (default <c>"did"</c>) UNCONDITIONALLY — before either
    /// <see cref="BuildIconSource"/> or <see cref="BuildRowIconResolve"/>'s
    /// null-resolver early return, so <c>iconkind="spel"</c> throws
    /// <see cref="FormatException"/> at <c>Build</c> on every host, even one
    /// with no <see cref="IMarkupIconResolver"/> wired at all. A malformed
    /// attribute is a Build-time author error regardless of what the host
    /// happens to support.
    ///
    /// <para>
    /// Fix round item 5: <paramref name="context"/> (default <c>"iconkind"</c>
    /// for the non-column call sites — <c>&lt;icon&gt;</c>, <c>&lt;button
    /// icon&gt;</c>, <c>&lt;list icons&gt;</c>) prefixes the throw message so
    /// <c>&lt;column type="icon"&gt;</c>'s own call site can identify which
    /// column failed (<c>column[2] type="icon" iconkind</c>).
    /// </para>
    /// </summary>
    private static string ValidateIconKind(string? iconKind, string context = "iconkind") =>
        (iconKind ?? "did") switch
        {
            "did" or "spell" or "item" => iconKind ?? "did",
            var other => throw new FormatException(
                $"{context} must be did, spell, or item (got \"{other}\")"),
        };

    /// <summary>
    /// Owner live-client report 2026-09-07 ("Those BIG gold/yellow buttons HAS
    /// to go. That is not how vtank looks."): validates <c>&lt;menu
    /// style="..."&gt;</c> and returns the <see cref="UiMenu.RetailButtonArt"/>
    /// value it selects. Default (attribute absent, or explicit
    /// <c>style="plain"</c>) is the flat VTank/Decal <c>HudCombo</c> box
    /// (<c>false</c>) — retail's gold pushbutton art is now an explicit
    /// <c>style="retail"</c> opt-in for a plugin panel that genuinely wants
    /// it. Any other value is a Build-time author error, same rule as
    /// <see cref="ValidateIconKind"/>.
    /// </summary>
    private static bool ValidateMenuStyle(string? style) => style switch
    {
        null or "plain" => false,
        "retail" => true,
        var other => throw new FormatException(
            $"<menu style=\"{other}\"> must be plain or retail"),
    };

    /// <summary>
    /// Builds the zero-argument icon resolver the <c>&lt;icon&gt;</c> element
    /// uses: dispatch by <c>iconkind</c> (default <c>"did"</c>) to the
    /// matching <see cref="IMarkupIconResolver"/> method, normalizing
    /// <c>did</c> through <see cref="PluginIcons.Normalize"/> (spell/item ids
    /// are never DAT RenderSurface DIDs, so they never pass through it).
    /// Null <paramref name="icons"/> (no resolver wired) always resolves to
    /// nothing rather than throwing — a standalone <c>&lt;icon&gt;</c> draws
    /// nothing either way, so there is no column-reservation concern here
    /// the way there is for <c>&lt;button icon&gt;</c>/<c>&lt;list icons&gt;</c>
    /// (see their own call sites in <see cref="AddElement"/>).
    /// </summary>
    private static Func<(uint tex, int w, int h)> BuildIconSource(
        string? iconKind, Func<uint> idReader, IMarkupIconResolver? icons)
    {
        string kind = ValidateIconKind(iconKind);
        if (icons is null)
            return static () => (0u, 0, 0);
        return kind switch
        {
            "did" => () => icons.ResolveDid(
                PluginIcons.Normalize(idReader())),
            "spell" => () => icons.ResolveSpell(idReader()),
            "item" => () => icons.ResolveItem(idReader()),
            _ => throw new InvalidOperationException(
                "unreachable — ValidateIconKind already rejected anything else"),
        };
    }

    /// <summary>
    /// Same dispatch as <see cref="BuildIconSource"/>, shaped for
    /// <c>&lt;list icons&gt;</c>'s per-row resolve (the row's own icon id is
    /// the argument rather than a captured reader). Callers only invoke this
    /// after confirming <paramref name="icons"/> is non-null (see the
    /// <c>&lt;list&gt;</c> case in <see cref="AddElement"/>) so
    /// <see cref="UiMarkupList.IconResolve"/> is never set to an
    /// always-empty delegate.
    /// </summary>
    private static Func<uint, (uint tex, int w, int h)> BuildRowIconResolve(
        string? iconKind, IMarkupIconResolver icons)
    {
        string kind = ValidateIconKind(iconKind);
        return kind switch
        {
            "did" => id => icons.ResolveDid(
                PluginIcons.Normalize(id)),
            "spell" => icons.ResolveSpell,
            "item" => icons.ResolveItem,
            _ => throw new InvalidOperationException(
                "unreachable — ValidateIconKind already rejected anything else"),
        };
    }

    /// <summary>
    /// Resolves a <c>did</c>/<c>spell</c>/<c>item</c> attribute to a live
    /// <see cref="uint"/> reader: a <c>{Prop}</c> binding re-reads a property
    /// every frame; a literal accepts hex (<c>0x...</c>) or decimal, matching
    /// every other markup id attribute's "malformed literal throws at Build"
    /// rule.
    /// </summary>
    /// <remarks>
    /// Review fix round finding 5: accepts ANY integral property type
    /// (<see cref="int"/>, <see cref="long"/>, <see cref="uint"/>,
    /// <see cref="ushort"/>, a nullable of any of those, …), not only an
    /// exact <see cref="uint"/> match — matching <see cref="BindUint"/>'s own
    /// leniency below. Decal-facing bindings are commonly <c>int</c> end to
    /// end (e.g. MosswartMassacre's <c>HudPictureBox.Image</c>), so requiring
    /// a literal <c>uint</c> property rejected every one of them at Build. A
    /// property whose runtime value cannot convert (a non-numeric type) still
    /// throws — just from <see cref="Convert.ToUInt32(object, IFormatProvider)"/>
    /// at read time rather than a type check at Build, the same tradeoff
    /// <see cref="BindUint"/> already makes.
    /// </remarks>
    /// <remarks>
    /// Residual round finding N3: a NEGATIVE bound value (Decal's own
    /// convention for "no icon" — e.g. <c>HudPictureBox.Image = -1</c>) used
    /// to throw <see cref="OverflowException"/> straight out of
    /// <see cref="Convert.ToUInt32(object, IFormatProvider)"/> — every frame,
    /// from inside <c>UiSimpleButton.OnDraw</c>. DECIDED: any value that does
    /// not fit in a <see cref="uint"/> — negative, or above
    /// <see cref="uint.MaxValue"/> — maps to <c>0u</c> (draws nothing) rather
    /// than throwing at draw time. <see cref="Convert.ToUInt32(object, IFormatProvider)"/>
    /// already throws exactly <see cref="OverflowException"/> for both of
    /// those cases (never for a non-numeric type, which still throws
    /// <see cref="InvalidCastException"/>/<see cref="FormatException"/> as
    /// before), so catching only that one exception type is sufficient.
    /// </remarks>
    private static Func<uint> BindUintLiteralOrBinding(
        string expression, object binding, string context)
    {
        if (!IsBinding(expression))
        {
            uint literal = ParseUintLiteral(expression, context);
            return () => literal;
        }
        PropertyInfo? property = binding.GetType().GetProperty(expression[1..^1]);
        if (property is null)
        {
            throw new FormatException(
                $"{expression} did not resolve to a property on "
                + binding.GetType().Name + $" ({context})");
        }
        return () => property.GetValue(binding) switch
        {
            uint u => u,
            null => 0u,
            var v => ToUintOrZero(v),
        };
    }

    /// <summary>
    /// <see cref="Convert.ToUInt32(object, IFormatProvider)"/>, mapping an
    /// out-of-range value (negative, or above <see cref="uint.MaxValue"/>) to
    /// <c>0u</c> instead of propagating <see cref="OverflowException"/>. See
    /// <see cref="BindUintLiteralOrBinding"/>'s finding N3 remark.
    /// </summary>
    private static uint ToUintOrZero(object value)
    {
        try
        {
            return Convert.ToUInt32(value, CultureInfo.InvariantCulture);
        }
        catch (OverflowException)
        {
            return 0u;
        }
    }

    private static uint ParseUintLiteral(string text, string context)
    {
        string trimmed = text.Trim();
        if (trimmed.StartsWith("0x", StringComparison.OrdinalIgnoreCase))
        {
            if (uint.TryParse(trimmed.AsSpan(2), NumberStyles.HexNumber,
                    CultureInfo.InvariantCulture, out uint hex))
                return hex;
        }
        else if (uint.TryParse(trimmed, NumberStyles.Integer,
                     CultureInfo.InvariantCulture, out uint dec))
        {
            return dec;
        }
        throw new FormatException($"{context}=\"{text}\" is not a valid uint literal");
    }

    /// <summary>
    /// Resolves <c>{PropName}</c> to a live string reader, or returns the
    /// literal text unchanged. The indirection matters: binding to a
    /// <see cref="Func{T}"/> rather than copying the value once is what makes a
    /// plugin's status text update as its state changes.
    /// </summary>
    private static Func<string?> BindString(string? attribute, object binding)
    {
        if (attribute is null)
            return static () => null;
        if (!IsBinding(attribute))
            return () => attribute;

        string name = attribute[1..^1];
        PropertyInfo? property = binding.GetType().GetProperty(name);
        if (property is null)
            return () => attribute;
        return () => property.GetValue(binding)?.ToString();
    }

    /// <summary>Resolves <c>{PropName}</c> to an <see cref="Action"/> property.</summary>
    private static Action? BindAction(string? attribute, object binding)
    {
        if (attribute is null || !IsBinding(attribute))
            return null;

        string name = attribute[1..^1];
        PropertyInfo? property = binding.GetType().GetProperty(name);
        if (property is null || !typeof(Action).IsAssignableFrom(property.PropertyType))
            return null;

        // Read through on each click rather than capturing the delegate now, so
        // a binding object may swap its handler (or null it out while busy)
        // without rebuilding the panel.
        return () => (property.GetValue(binding) as Action)?.Invoke();
    }

    private static Action<float>? BindFloatAction(
        string? attribute,
        object binding)
    {
        if (attribute is null || !IsBinding(attribute))
            return null;

        string name = attribute[1..^1];
        PropertyInfo? property = binding.GetType().GetProperty(name);
        if (property is null
            || !typeof(Action<float>).IsAssignableFrom(property.PropertyType))
            return null;
        return value => (property.GetValue(binding) as Action<float>)?.Invoke(value);
    }

    private static Action<string>? BindStringAction(
        string? attribute,
        object binding)
    {
        if (attribute is null || !IsBinding(attribute))
            return null;

        string name = attribute[1..^1];
        PropertyInfo? property = binding.GetType().GetProperty(name);
        if (property is null
            || !typeof(Action<string>).IsAssignableFrom(property.PropertyType))
        {
            return null;
        }
        return value => (property.GetValue(binding) as Action<string>)?.Invoke(value);
    }

    private static Action<int>? BindIntAction(string? attribute, object binding)
    {
        if (attribute is null || !IsBinding(attribute))
            return null;
        PropertyInfo? property = binding.GetType().GetProperty(attribute[1..^1]);
        if (property is null
            || !typeof(Action<int>).IsAssignableFrom(property.PropertyType))
        {
            return null;
        }
        return value => (property.GetValue(binding) as Action<int>)?.Invoke(value);
    }

    private static Func<IReadOnlyList<string>> BindStringList(
        string? expression,
        object binding,
        string context)
    {
        if (string.IsNullOrWhiteSpace(expression) || !IsBinding(expression))
            throw new FormatException($"{context} must be a string-list binding");
        PropertyInfo? property = binding.GetType().GetProperty(expression[1..^1]);
        if (property is null
            || !typeof(IEnumerable<string>).IsAssignableFrom(property.PropertyType))
        {
            throw new FormatException(
                $"{expression} did not resolve to an IEnumerable<string> property on "
                + binding.GetType().Name);
        }
        return () => property.GetValue(binding) is IEnumerable<string> values
            ? values.ToArray()
            : Array.Empty<string>();
    }

    /// <remarks>
    /// Review fix round finding 5: also accepts <see cref="IEnumerable{T}"/>
    /// of <see cref="int"/> — Decal is <c>int</c> end to end
    /// (MosswartMassacre's <c>FlagTrackerView.cs</c> feeds
    /// <c>HudPictureBox.Image</c> from <c>int</c> ids), so a plugin porting
    /// that convention hands the host <c>IEnumerable&lt;int&gt;</c>, not
    /// <c>IEnumerable&lt;uint&gt;</c>.
    /// </remarks>
    /// <remarks>
    /// Residual round finding N3: the per-element conversion used to be an
    /// UNCHECKED reinterpret (<c>-1</c> silently wrapped to <c>0xFFFFFFFF</c>
    /// — a bogus, almost-certainly-unresolvable id drawn as if it were a real
    /// one, rather than the "no icon" <c>0u</c> the same negative value maps
    /// to on the scalar path — see <see cref="ToUintOrZero"/>). DECIDED: a
    /// negative element now maps to <c>0u</c> here too, matching the scalar
    /// path's contract exactly (both "no icon" conventions agree).
    /// </remarks>
    private static Func<IReadOnlyList<uint>> BindUintList(
        string? expression,
        object binding,
        string context)
    {
        if (string.IsNullOrWhiteSpace(expression))
            return static () => Array.Empty<uint>();
        if (!IsBinding(expression))
            throw new FormatException($"{context} must be a uint-list binding");
        PropertyInfo? property = binding.GetType().GetProperty(expression[1..^1]);
        if (property is null)
        {
            throw new FormatException(
                $"{expression} did not resolve to an IEnumerable<uint> or "
                + "IEnumerable<int> property on " + binding.GetType().Name);
        }
        if (typeof(IEnumerable<uint>).IsAssignableFrom(property.PropertyType))
        {
            return () => property.GetValue(binding) is IEnumerable<uint> values
                ? values.ToArray()
                : Array.Empty<uint>();
        }
        if (typeof(IEnumerable<int>).IsAssignableFrom(property.PropertyType))
        {
            return () => property.GetValue(binding) is IEnumerable<int> values
                ? values.Select(static v => v < 0 ? 0u : (uint)v).ToArray()
                : Array.Empty<uint>();
        }
        throw new FormatException(
            $"{expression} did not resolve to an IEnumerable<uint> or "
            + "IEnumerable<int> property on " + binding.GetType().Name);
    }

    /// <summary>
    /// <c>&lt;column type="check" values="{IReadOnlyList&lt;bool&gt;}"&gt;</c>
    /// (Campaign VT slice 1 Part B). Required — unlike <see cref="BindUintList"/>'s
    /// "silent if omitted" carve-out for the optional <c>list colors</c>
    /// attribute, a check column with no <c>values</c> binding is a Build-time
    /// author error (there is nothing sensible to draw).
    /// </summary>
    private static Func<IReadOnlyList<bool>> BindBoolList(
        string? expression, object binding, string context)
    {
        if (string.IsNullOrWhiteSpace(expression) || !IsBinding(expression))
            throw new FormatException($"{context} must be a bool-list binding");
        PropertyInfo? property = binding.GetType().GetProperty(expression[1..^1]);
        if (property is null
            || !typeof(IEnumerable<bool>).IsAssignableFrom(property.PropertyType))
        {
            throw new FormatException(
                $"{expression} did not resolve to an IEnumerable<bool> property on "
                + binding.GetType().Name + $" ({context})");
        }
        return () => property.GetValue(binding) is IEnumerable<bool> values
            ? values.ToArray()
            : Array.Empty<bool>();
    }

    /// <summary>
    /// Same grammar as <see cref="BindUintList"/> but REQUIRED — used by
    /// <c>&lt;column type="icon" values="..."&gt;</c>, where (unlike the
    /// single-column list's optional <c>icons</c> attribute) there is no
    /// "no icon column at all" fallback: an icon column with no
    /// <c>values</c> binding is a Build-time author error.
    /// </summary>
    private static Func<IReadOnlyList<uint>> BindRequiredUintList(
        string? expression, object binding, string context)
    {
        if (string.IsNullOrWhiteSpace(expression))
            throw new FormatException($"{context} must be a uint-list binding");
        return BindUintList(expression, binding, context);
    }

    /// <summary>
    /// <c>&lt;column&gt;</c>'s <c>onchange</c> (check)/<c>onclick</c> (icon) —
    /// unlike every other <c>Action&lt;int&gt;</c> sink in this file (the
    /// list's own <c>onchange</c>, which is optional), a column callback is
    /// REQUIRED: a check/icon column that never fires anything is a
    /// Build-time author error, not a silently-inert control.
    /// </summary>
    private static Action<int> BindRequiredIntAction(
        string? attribute, object binding, string context)
    {
        if (attribute is null || !IsBinding(attribute))
            throw new FormatException($"{context} must be an Action<int> binding");
        PropertyInfo? property = binding.GetType().GetProperty(attribute[1..^1]);
        if (property is null || !typeof(Action<int>).IsAssignableFrom(property.PropertyType))
        {
            throw new FormatException(
                $"{attribute} did not resolve to an Action<int> property on "
                + binding.GetType().Name + $" ({context})");
        }
        return value => (property.GetValue(binding) as Action<int>)?.Invoke(value);
    }

    /// <summary>
    /// Builds one <see cref="UiMarkupListColumn"/> from a <c>&lt;column&gt;</c>
    /// child of <c>&lt;list&gt;</c> (Campaign VT slice 1 Part B —
    /// <c>docs/research/vtank-kb/08-ui-views.md</c> §3's proposed extension).
    /// <paramref name="icons"/> follows the same "validate iconkind
    /// unconditionally, wire the resolver only when one exists" rule as the
    /// legacy <c>&lt;list icons&gt;</c> path (<see cref="BuildRowIconResolve"/>'s
    /// own call site above): a malformed <c>iconkind</c> throws at Build even
    /// on a resolver-less host, but <see cref="UiMarkupListColumn.IconResolve"/>
    /// stays null (draws nothing) rather than ever pointing at a null resolver.
    /// </summary>
    private static UiMarkupListColumn BuildListColumn(
        XElement columnEl, object binding, IMarkupIconResolver? icons, int index, bool isLast)
    {
        string? type = (string?)columnEl.Attribute("type");
        (float width, bool isAutoWidth) = ParseColumnWidth(columnEl, index, type, isLast);
        switch (type)
        {
            case "text":
            {
                var textSource = BindStringList(
                    (string?)columnEl.Attribute("items"), binding, ColumnContext(index, "text", "items"));
                string? colorsAttr = (string?)columnEl.Attribute("colors");
                Func<IReadOnlyList<uint>>? colorsSource = colorsAttr is null
                    ? null
                    : BindUintList(colorsAttr, binding, ColumnContext(index, "text", "colors"));
                // Fix round finding 1: optional onclick — a text cell that
                // declares one fires it with the row index instead of
                // selecting; one that doesn't keeps the original
                // select-on-click behavior. Same "resolve if binding-shaped,
                // throw only if malformed" rule as the list's own onchange
                // above — omitting the attribute entirely is fine.
                string? textOnClickAttr = (string?)columnEl.Attribute("onclick");
                Action<int>? textOnClick = BindIntAction(textOnClickAttr, binding);
                if (textOnClickAttr is not null && textOnClick is null)
                {
                    throw new FormatException(
                        $"{ColumnContext(index, "text", "onclick")} did not resolve to an "
                        + $"Action<int> property on {binding.GetType().Name}");
                }
                return UiMarkupListColumn.Text(width, textSource, colorsSource, textOnClick, isAutoWidth);
            }
            case "check":
            {
                var checkSource = BindBoolList(
                    (string?)columnEl.Attribute("values"), binding, ColumnContext(index, "check", "values"));
                var onChange = BindRequiredIntAction(
                    (string?)columnEl.Attribute("onchange"), binding, ColumnContext(index, "check", "onchange"));
                return UiMarkupListColumn.Check(width, checkSource, onChange, isAutoWidth);
            }
            case "icon":
            {
                var valuesSource = BindRequiredUintList(
                    (string?)columnEl.Attribute("values"), binding, ColumnContext(index, "icon", "values"));
                string? iconKind = (string?)columnEl.Attribute("iconkind");
                ValidateIconKind(iconKind, ColumnContext(index, "icon", "iconkind"));
                var onClick = BindRequiredIntAction(
                    (string?)columnEl.Attribute("onclick"), binding, ColumnContext(index, "icon", "onclick"));
                Func<uint, (uint, int, int)>? resolve = icons is not null
                    ? BuildRowIconResolve(iconKind, icons)
                    : null;
                return UiMarkupListColumn.Icon(width, valuesSource, resolve, onClick, isAutoWidth);
            }
            default:
                throw new FormatException(
                    $"column[{index}] has unknown type=\"{type}\" (expected text, check, or icon)");
        }
    }

    /// <summary>
    /// Fix round finding 5: every column-attribute throw message identifies
    /// the offending column by position and declared type
    /// (<c>column[2] type="check" values</c>) rather than the generic
    /// <c>"column values"</c> the initial slice used — a plugin author with
    /// several columns of the same <c>type</c> needs the index to find which
    /// one is wrong.
    /// </summary>
    private static string ColumnContext(int index, string type, string attribute) =>
        $"column[{index}] type=\"{type}\" {attribute}";

    /// <summary>
    /// Fix round item 2: <c>&lt;column width&gt;</c> semantics. <c>"*"</c>
    /// (any column, including the last) means auto — this column shares the
    /// list's remaining width equally with every other auto column at
    /// layout time (see <see cref="UiMarkupList"/>'s column-layout helper).
    /// A NON-last column with a missing, unparseable, or non-positive width
    /// is a Build-time author error (there is nothing sensible to lay out).
    /// The LAST column is exempt from this validation entirely — it always
    /// absorbs whatever room remains regardless of its own declared width,
    /// so an invalid value there is harmless and never thrown; only an
    /// explicit <c>"*"</c> there is actually meaningful (it makes the last
    /// column share evenly with any OTHER auto columns instead of taking
    /// 100% of the remainder alone — see <see cref="UiMarkupListColumn"/>'s
    /// own doc for exactly how the last column's implicit auto-ness
    /// combines with an explicit one).
    /// </summary>
    private static (float width, bool isAutoWidth) ParseColumnWidth(
        XElement columnEl, int index, string? type, bool isLast)
    {
        string? raw = (string?)columnEl.Attribute("width");
        if (raw == "*")
            return (0f, true);
        if (isLast)
            return (F(columnEl, "width"), false);
        if (!float.TryParse(raw, NumberStyles.Float, CultureInfo.InvariantCulture, out float width)
            || width <= 0f)
        {
            throw new FormatException(
                $"{ColumnContext(index, type ?? "(missing)", "width")} must be a positive "
                + "number or \"*\", got " + (raw is null ? "(missing)" : $"\"{raw}\""));
        }
        return (width, false);
    }

    private static bool IsBinding(string value) =>
        value.Length > 2 && value[0] == '{' && value[^1] == '}';

    private static void ApplyCommon(
        UiElement element,
        XElement source,
        object binding)
    {
        element.Name = (string?)source.Attribute("name")
            ?? (string?)source.Attribute("id");
        BindBool((string?)source.Attribute("visible"), binding,
            value => element.Visible = value,
            sourceReader => element.VisibleSource = sourceReader);
        BindBool((string?)source.Attribute("enabled"), binding,
            value => element.Enabled = value,
            sourceReader => element.EnabledSource = sourceReader);

        string? tooltip = (string?)source.Attribute("tooltip");
        if (!string.IsNullOrWhiteSpace(tooltip))
        {
            element.RuntimeTooltipTextSource = BindString(tooltip, binding);
            element.AuthoredTooltipRootElementId = RuntimeTooltipRootElementId;
            element.AuthoredTooltipLayoutDid = RuntimeTooltipLayoutDid;
            element.AuthoredTooltipEnabled = true;
        }
    }

    private static void BindBool(
        string? expression,
        object binding,
        Action<bool> setLiteral,
        Action<Func<bool>> setSource)
    {
        if (string.IsNullOrWhiteSpace(expression))
            return;
        if (!IsBinding(expression))
        {
            if (bool.TryParse(expression, out bool literal))
                setLiteral(literal);
            return;
        }

        PropertyInfo? property = binding.GetType().GetProperty(expression[1..^1]);
        if (property is null || property.PropertyType != typeof(bool))
        {
            throw new FormatException(
                $"{expression} did not resolve to a bool property on "
                + binding.GetType().Name);
        }
        setSource(() => property.GetValue(binding) is true);
    }

    private static Func<bool> BindRequiredBoolReader(
        string? expression,
        object binding,
        string context)
    {
        if (string.IsNullOrWhiteSpace(expression) || !IsBinding(expression))
            throw new FormatException($"{context} must be a bool binding");

        PropertyInfo? property = binding.GetType().GetProperty(expression[1..^1]);
        if (property is null || property.PropertyType != typeof(bool))
        {
            throw new FormatException(
                $"{expression} did not resolve to a bool property on "
                + binding.GetType().Name);
        }
        return () => property.GetValue(binding) is true;
    }

    private static Func<int> BindRequiredIntReader(
        string? expression,
        object binding,
        string context)
    {
        if (string.IsNullOrWhiteSpace(expression) || !IsBinding(expression))
            throw new FormatException($"{context} must be an int binding");
        PropertyInfo? property = binding.GetType().GetProperty(expression[1..^1]);
        if (property is null || property.PropertyType != typeof(int))
        {
            throw new FormatException(
                $"{expression} did not resolve to an int property on "
                + binding.GetType().Name);
        }
        return () => property.GetValue(binding) is int value ? value : -1;
    }

    private static float F(XElement e, string attr)
        => float.TryParse((string?)e.Attribute(attr), NumberStyles.Float,
            CultureInfo.InvariantCulture, out var v) ? v : 0f;

    private static float FOr(XElement e, string attr, float fallback)
        => float.TryParse((string?)e.Attribute(attr), NumberStyles.Float,
            CultureInfo.InvariantCulture, out float value) ? value : fallback;

    private static int I(XElement e, string attr, int fallback)
        => int.TryParse((string?)e.Attribute(attr), NumberStyles.Integer,
            CultureInfo.InvariantCulture, out int value) ? value : fallback;

    private static bool B(XElement e, string attr, bool fallback)
        => bool.TryParse((string?)e.Attribute(attr), out bool value)
            ? value
            : fallback;

    /// <summary>
    /// Parses <c>#AARRGGBB</c> → RGBA <see cref="Vector4"/> (alpha first, matching
    /// controls.ini convention). Falls back to opaque white on bad input.
    /// </summary>
    private static Vector4 Color(string? hex)
    {
        if (hex is { Length: 9 } && hex[0] == '#'
            && uint.TryParse(hex.AsSpan(1), NumberStyles.HexNumber,
                             CultureInfo.InvariantCulture, out uint argb))
            return new Vector4(
                ((argb >> 16) & 0xFF) / 255f,
                ((argb >> 8)  & 0xFF) / 255f,
                (argb         & 0xFF) / 255f,
                ((argb >> 24) & 0xFF) / 255f);
        return Vector4.One;
    }

    private static Func<float?> BindFloat(string? expr, object binding)
    {
        var pi = Prop(expr, binding);
        if (pi is null) return () => 0f;
        return () => pi.GetValue(binding) switch
        {
            float f  => f,
            null     => (float?)null,
            var v    => Convert.ToSingle(v, CultureInfo.InvariantCulture),
        };
    }

    private static Func<uint?> BindUint(string? expr, object binding)
    {
        var pi = Prop(expr, binding);
        if (pi is null) return () => null;
        return () => pi.GetValue(binding) switch
        {
            uint u => u,
            null   => (uint?)null,
            var v  => Convert.ToUInt32(v, CultureInfo.InvariantCulture),
        };
    }

    private static PropertyInfo? Prop(string? expr, object binding)
    {
        if (expr is null || expr.Length < 3 || expr[0] != '{' || expr[^1] != '}') return null;
        return binding.GetType().GetProperty(expr[1..^1]);
    }

    private static uint Hex(string? s)
    {
        if (string.IsNullOrWhiteSpace(s)) return 0;
        var t = s.Trim();
        if (t.StartsWith("0x", System.StringComparison.OrdinalIgnoreCase)) t = t[2..];
        return uint.TryParse(t, System.Globalization.NumberStyles.HexNumber,
            System.Globalization.CultureInfo.InvariantCulture, out var v) ? v : 0u;
    }

    private static AnchorEdges Anchor(string? csv)
    {
        if (string.IsNullOrWhiteSpace(csv)) return AnchorEdges.Left | AnchorEdges.Top;
        var a = AnchorEdges.None;
        foreach (var part in csv.Split(',', System.StringSplitOptions.TrimEntries | System.StringSplitOptions.RemoveEmptyEntries))
            a |= part.ToLowerInvariant() switch
            {
                "left"   => AnchorEdges.Left,
                "top"    => AnchorEdges.Top,
                "right"  => AnchorEdges.Right,
                "bottom" => AnchorEdges.Bottom,
                _        => AnchorEdges.None,
            };
        return a == AnchorEdges.None ? AnchorEdges.Left | AnchorEdges.Top : a;
    }
}