using System.Numerics;
using AcDream.App.Rendering;

namespace AcDream.App.UI;

/// <summary>
/// Per-frame drawing context passed through the <see cref="UiElement"/>
/// tree. Wraps a <see cref="TextRenderer"/> (our 2D sprite batcher) and a
/// transform stack so elements can draw in local coordinates.
///
/// Retail equivalent: the implicit context <c>FUN_005da8f0</c> walks with
/// when iterating the UI tree. Our version is explicit so it plugs
/// cleanly into Silk.NET.
/// </summary>
public sealed class UiRenderContext
{
    public TextRenderer TextRenderer { get; }
    public BitmapFont? DefaultFont { get; set; }
    public Vector2 ScreenSize { get; }

    // Transform stack — simple 2D translate (no rotation/scale for UI).
    private readonly System.Collections.Generic.List<Vector2> _stack = new();
    private Vector2 _current;

    public UiRenderContext(TextRenderer tr, Vector2 screenSize, BitmapFont? defaultFont = null)
    {
        TextRenderer = tr;
        ScreenSize = screenSize;
        DefaultFont = defaultFont;
    }

    /// <summary>Push a relative translate. Must be paired with <see cref="PopTransform"/>.</summary>
    public void PushTransform(float dx, float dy)
    {
        _stack.Add(_current);
        _current += new Vector2(dx, dy);
    }

    public void PopTransform()
    {
        if (_stack.Count == 0) return;
        _current = _stack[^1];
        _stack.RemoveAt(_stack.Count - 1);
    }

    public Vector2 CurrentOrigin => _current;

    // ── Pass-through draw helpers (add current translate) ──────────────

    public void DrawRect(float x, float y, float w, float h, Vector4 color)
        => TextRenderer.DrawRect(_current.X + x, _current.Y + y, w, h, color);

    public void DrawRectOutline(float x, float y, float w, float h, Vector4 color, float thickness = 1f)
        => TextRenderer.DrawRectOutline(_current.X + x, _current.Y + y, w, h, color, thickness);

    public void DrawString(string text, float x, float y, Vector4 color, BitmapFont? font = null)
    {
        var f = font ?? DefaultFont;
        if (f is null) return;
        TextRenderer.DrawString(f, text, _current.X + x, _current.Y + y, color);
    }
}