using Annulus;
using Azimuth;
using Blacklight.Core;
using Blacklight.Core.Drawables;
using Prism;

namespace Glass.Blacklight
{
    /// <summary>
    /// Draws a flat rectangle the way a SolidColorMaterial does.
    /// </summary>
    public static class SolidRect
    {
        /// <summary>
        /// Draws <paramref name="rect"/> in <paramref name="color"/>, cut down to what <paramref name="drawState"/>
        /// lets show.
        /// </summary>
        public static void Draw(Cel context, Color color, Rect rect, in DrawState drawState)
        {
            if (rect.Width == 0 || rect.Height == 0)
            {
                return;
            }

            if (!(drawState.VisibleWithin(rect) is OrientedBox visible))
            {
                return;
            }

            var rectangle = new Rectangle { InsideColor = color };

            // A tilted visible part is drawn as a tilted rectangle.  A rectangle's model space is stretched, so a clip
            // window tilted inside it would not stay a box.
            if (!visible.TryGetRect(out Rect upright))
            {
                Vector halfSide = visible.SideOffset * 0.5;
                Vector halfCross = visible.CrossOffset * 0.5;
                context.AddEntity(rectangle, drawState.ModelToWorld
                    * new AffineMatrix(halfSide, halfCross, visible.Origin + halfSide + halfCross));
                return;
            }

            context.AddEntity(rectangle, drawState.ModelToWorld
                * Rectangle.ModelToWorld(
                    new Vector(upright.Width, upright.Height), position: upright.TopLeft,
                    anchor: Rectangle.TopLeft));
        }
    }
}