using System.Numerics;

namespace AcDream.App.UI;

/// <summary>Leaf widget for dat Type 0xD (UIElement_Viewport). Blits the texture produced by its
/// IUiViewportRenderer (run in the pre-UI hook) as a single sprite at its own rect. The 3-D render
/// does NOT happen here (OnDraw only has a 2-D context).</summary>
public sealed class UiViewport : UiElement
{
    public override bool ConsumesDatChildren => true;

    /// <summary>Optional click action (e.g. the paperdoll doll = "target self"
    /// during item target-use). Non-null makes the viewport handle the press
    /// itself instead of it being captured as a window move.</summary>
    public System.Action? Clicked { get; set; }

    public override bool HandlesClick => Clicked is not null;

    public override bool OnEvent(in UiEvent e)
    {
        if (Clicked is null) return base.OnEvent(e);
        switch (e.Type)
        {
            case UiEventType.MouseDown: return true;   // consume the press; act on Click
            case UiEventType.Click: Clicked.Invoke(); return true;
        }
        return base.OnEvent(e);
    }

    /// <summary>Renderer that produces the off-screen texture. Set by GameWindow wiring (later task).</summary>
    public IUiViewportRenderer? Renderer { get; set; }

    /// <summary>Last GL color-texture handle produced by the pre-UI hook. 0 = nothing to blit.</summary>
    public uint TextureHandle { get; set; }

    protected override void OnDraw(UiRenderContext ctx)
    {
        if (!Visible || TextureHandle == 0) return;
        // Local origin is already at this widget's Left/Top (PushTransform applied by DrawSelfAndChildren).
        // V is FLIPPED (v0=1, v1=0): TextureHandle is an off-screen FBO color texture, whose origin is
        // bottom-left (GL), while the UI sprite convention is top-left. Without the flip the doll renders
        // upside-down. (If the doll appears upside-down at the visual gate, this is the line to revisit.)
        ctx.DrawSprite(TextureHandle, 0f, 0f, Width, Height, 0f, 1f, 1f, 0f, Vector4.One);
    }
}