From f7467a62ee56e7ad4d4f268cba0c0e133bb1ea9c Mon Sep 17 00:00:00 2001
From: Syntriax <syntriax@gmail.com>
Date: Thu, 25 Jan 2024 18:21:52 +0300
Subject: [PATCH] feat: Collision Detector Circles

---
 Engine.Physics2D/CollisionDetector.cs  | 58 ++++++++++++++++++++++++++
 Engine.Physics2D/ICollisionDetector.cs |  8 ++++
 2 files changed, 66 insertions(+)
 create mode 100644 Engine.Physics2D/CollisionDetector.cs
 create mode 100644 Engine.Physics2D/ICollisionDetector.cs

diff --git a/Engine.Physics2D/CollisionDetector.cs b/Engine.Physics2D/CollisionDetector.cs
new file mode 100644
index 0000000..78cae49
--- /dev/null
+++ b/Engine.Physics2D/CollisionDetector.cs
@@ -0,0 +1,58 @@
+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, 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 DetectShapeCircle(shapeColliderRight, circleColliderLeft, out collisionInformation);
+            else if (right is ICircleCollider2D circleColliderRight)
+                return DetectCircleCircle(circleColliderLeft, circleColliderRight, out collisionInformation);
+        }
+
+        return false;
+    }
+
+    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;
+    }
+}
diff --git a/Engine.Physics2D/ICollisionDetector.cs b/Engine.Physics2D/ICollisionDetector.cs
new file mode 100644
index 0000000..3180126
--- /dev/null
+++ b/Engine.Physics2D/ICollisionDetector.cs
@@ -0,0 +1,8 @@
+using Syntriax.Engine.Physics2D.Abstract;
+
+namespace Syntriax.Engine.Physics2D;
+
+public interface ICollisionDetector
+{
+    bool TryDetect<T1, T2>(T1 left, T2 right, out CollisionDetectionInformation? collisionInformation) where T1 : ICollider2D where T2 : ICollider2D;
+}