using System;
using System.Numerics;

namespace AcDream.App.UI;

/// <summary>
/// #381 (Campaign OP gate 4, 2026-08-11): a minimal, purely-synthesized
/// leaf that tiles ONE opaque sprite across its own rect — nothing more.
/// Used for the Apply/Reset/Defaults footer's opaque backing field: a
/// live-DAT probe found the Character/Chat/Config page roots author
/// EXACTLY five children each (the row ListBox, its scrollbar, and the
/// three physical buttons) with zero direct-state media on the root itself
/// — retail authors NO backdrop element behind the footer strip at all, so
/// scrolled row content bled through between/behind the three buttons.
///
/// <para>
/// This is a genuine synthesis, not a retail port — register row AP-205
/// records it. The fill sprite is <see cref="RetailChromeSprites.CenterFill"/>,
/// the SAME authored panel-background media the whole Options window's own
/// <see cref="UiNineSlicePanel"/> chrome already tiles behind everything —
/// not an invented color, the panel's own background family reused for
/// visual consistency with the rest of the window.
/// </para>
///
/// <para>
/// <see cref="UiNineSlicePanel"/> itself was not reused here — its
/// constructor forces <c>Draggable</c>/<c>Resizable</c>/<c>Anchors.None</c>
/// (top-level-window machinery this footer strip must never have) and
/// draws a full 8-piece bevel + resize grip this borderless field
/// explicitly does not want (the issue calls for "no border").
/// </para>
/// </summary>
public sealed class UiSolidSpriteFill : UiElement
{
    public uint SpriteId { get; init; }
    public Func<uint, (uint tex, int w, int h)>? SpriteResolve { get; set; }

    public UiSolidSpriteFill()
    {
        // A backing field must never intercept pointer events meant for
        // whatever's stacked in front of/behind it (the buttons draw ON
        // TOP via their own later ReadOrder; nothing should route to this
        // leaf at all).
        ClickThrough = true;
    }

    protected override void OnDraw(UiRenderContext ctx)
    {
        var resolve = SpriteResolve;
        if (resolve is null || SpriteId == 0u) return;
        var (tex, tw, th) = resolve(SpriteId);
        if (tex == 0 || tw == 0 || th == 0) return;
        // Force OPAQUE — an occluding backing field must read solid even
        // when it sits inside a window whose own chrome/content is
        // translucent (same "force opaque" pattern UiMenu's popup uses).
        ctx.PushAlphaAbsolute(1f);
        try
        {
            ctx.DrawSprite(tex, 0f, 0f, Width, Height, 0f, 0f, Width / tw, Height / th, Vector4.One);
        }
        finally { ctx.PopAlpha(); }
    }
}