MoonTools.Bonk/Bonk/Shapes/2D/Rectangle.cs

using System;
using System.Numerics;
using MoonTools.Structs;

namespace MoonTools.Bonk
{
    /// <summary>
    /// A rectangle is a shape defined by a width and height. The origin is the center of the rectangle.
    /// </summary>
    public struct Rectangle : IShape2D, IEquatable<Rectangle>
    {
        public AABB2D AABB { get; }
        public int Width { get; }
        public int Height { get; }

        public float Right { get; }
        public float Left { get; }
        public float Top { get; }
        public float Bottom { get; }
        public Vector2 BottomLeft { get; }
        public Vector2 TopRight { get; }

        public Vector2 Min { get; }
        public Vector2 Max { get; }

        public Rectangle(int left, int top, int width, int height)
        {
            Width = width;
            Height = height;
            Left = left;
            Right = left + width;
            Top = top;
            Bottom = top + height;
            AABB = new AABB2D(left, top, Right, Bottom);
            BottomLeft = new Vector2(Left, Bottom);
            TopRight = new Vector2(Top, Right);
            Min = AABB.Min;
            Max = AABB.Max;
        }

        private Vector2 Support(Vector2 direction)
        {
            if (direction.X >= 0 && direction.Y >= 0)
            {
                return Max;
            }
            else if (direction.X >= 0 && direction.Y < 0)
            {
                return new Vector2(Max.X, Min.Y);
            }
            else if (direction.X < 0 && direction.Y >= 0)
            {
                return new Vector2(Min.X, Max.Y);
            }
            else if (direction.X < 0 && direction.Y < 0)
            {
                return new Vector2(Min.X, Min.Y);
            }
            else
            {
                throw new ArgumentException("Support vector direction cannot be zero.");
            }
        }

        public Vector2 Support(Vector2 direction, Transform2D transform)
        {
            Matrix3x2 inverseTransform;
            Matrix3x2.Invert(transform.TransformMatrix, out inverseTransform);
            var inverseDirection = Vector2.TransformNormal(direction, inverseTransform);
            return Vector2.Transform(Support(inverseDirection), transform.TransformMatrix);
        }

        public AABB2D TransformedAABB(Transform2D transform)
        {
            return AABB2D.Transformed(AABB, transform);
        }

        public override bool Equals(object obj)
        {
            return obj is IShape2D other && Equals(other);
        }

        public bool Equals(IShape2D other)
        {
            return (other is Rectangle rectangle && Equals(rectangle));
        }

        public bool Equals(Rectangle other)
        {
            return Min == other.Min && Max == other.Max;
        }

        public override int GetHashCode()
        {
            return HashCode.Combine(Min, Max);
        }

        public static bool operator ==(Rectangle a, Rectangle b)
        {
            return a.Equals(b);
        }

        public static bool operator !=(Rectangle a, Rectangle b)
        {
            return !(a == b);
        }

        public static bool operator ==(Rectangle a, Polygon2D b)
        {
            return a.Equals(b);
        }

        public static bool operator !=(Rectangle a, Polygon2D b)
        {
            return !(a == b);
        }
    }
}