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 leftToRightCenterProjectionVector = left.CircleWorld.Center.FromTo(right.CircleWorld.Center).Normalized;

        Projection leftProjection = left.CircleWorld.ToProjection(leftToRightCenterProjectionVector);
        Projection rightProjection = right.CircleWorld.ToProjection(leftToRightCenterProjectionVector);

        bool collision = leftProjection.Overlaps(rightProjection, out float depth);

        if (collision)
            collisionInformation = new(left, right, leftToRightCenterProjectionVector, depth);

        return collision;
    }

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

    //     Vector2D leftToRightCenter = left.CircleWorld.Center.FromTo(right.CircleWorld.Center);
    //     float distanceCircleCenter = leftToRightCenter.Magnitude;
    //     float radiusSum = left.CircleWorld.Radius + right.CircleWorld.Radius;

    //     float circleSurfaceDistance = distanceCircleCenter - radiusSum;

    //     bool collision = circleSurfaceDistance <= 0f;

    //     if (collision)
    //         collisionInformation = new(left, right, leftToRightCenter.Normalized, -circleSurfaceDistance);

    //     return collision;
    // }
}