Syntriax.Engine/Engine.Physics2D/CollisionDetector.cs

using System.Diagnostics.CodeAnalysis;

using Syntriax.Engine.Core;
using Syntriax.Engine.Physics2D.Abstract;

namespace Syntriax.Engine.Physics2D;

public class CollisionDetector : ICollisionDetector
{
    public bool TryDetect<T1, T2>(T1 left, T2 right, [NotNullWhen(true)] out CollisionDetectionInformation? collisionInformation)
        where T1 : ICollider2D
        where T2 : ICollider2D
    {
        collisionInformation = default;
        if (left is IShapeCollider2D shapeColliderLeft)
        {
            if (right is IShapeCollider2D shapeColliderRight)
                return DetectShapeShape(shapeColliderLeft, shapeColliderRight, out collisionInformation);
            else if (right is ICircleCollider2D circleColliderRight)
                return DetectShapeCircle(shapeColliderLeft, circleColliderRight, out collisionInformation);
        }
        else if (left is ICircleCollider2D circleColliderLeft)
        {
            if (right is IShapeCollider2D shapeColliderRight)
                return DetectCircleShape(circleColliderLeft, shapeColliderRight, out collisionInformation);
            else if (right is ICircleCollider2D circleColliderRight)
                return DetectCircleCircle(circleColliderLeft, circleColliderRight, out collisionInformation);
        }

        return false;
    }

    private bool DetectCircleShape(ICircleCollider2D circleCollider, IShapeCollider2D shapeCollider, out CollisionDetectionInformation? collisionInformation)
    {
        throw new System.NotImplementedException();
    }

    private static bool DetectShapeShape(IShapeCollider2D left, IShapeCollider2D right, out CollisionDetectionInformation? collisionInformation)
    {
        throw new System.NotImplementedException();
    }

    private static bool DetectShapeCircle(IShapeCollider2D shapeCollider, ICircleCollider2D circleCollider, out CollisionDetectionInformation? collisionInformation)
    {
        throw new System.NotImplementedException();
    }

    private static bool DetectCircleCircle(ICircleCollider2D left, ICircleCollider2D right, out CollisionDetectionInformation? collisionInformation)
    {
        collisionInformation = default;

        Vector2D leftToRightCenter = left.CircleWorld.Center.FromTo(right.CircleWorld.Center);
        float distanceCircleCenterSquared = leftToRightCenter.MagnitudeSquared;
        float radiusSumSquared = left.CircleWorld.RadiusSquared + right.CircleWorld.RadiusSquared;

        float circleSurfaceDistanceSquared = distanceCircleCenterSquared - radiusSumSquared;

        bool collision = circleSurfaceDistanceSquared <= 0f;

        if (collision)
            collisionInformation = new(left, right, leftToRightCenter.Normalized, Math.Sqrt(circleSurfaceDistanceSquared));

        return collision;
    }
}