feat(math): add negate operation to Vec2

Author: RuggeroVisintin

src/core/math/Vec2.ts

@@ -1,7 +1,17 @@
 export class Vec2 {
-    constructor(
-        public readonly x: number = 0,
-        public readonly y: number = 0
+    public constructor(
+        public x: number = 0,
+        public y: number = 0
     ) {
     }
+
+    public negate(): void {
+        this.x = -this.x;
+        this.y = -this.y;
+    }
+
+    public getNegated(): Vec2 {
+        // avoid reusing negate for better performance
+        return new Vec2(-this.x, -this.y);
+    }
 }

test/unit/core/math/Vec2.test.ts

@@ -10,4 +10,38 @@ describe('core/math/Vec2', () => {
             });
         })
     })
+
+    describe('.negate()', () => {
+        it('Should negate the vector in place', () => {
+            const vec = new Vec2(1, 2);
+            vec.negate()
+            expect(vec).toEqual({
+                x: -1,
+                y: -2
+            });
+        }) 
+    })
+
+    describe('.getNegated()', () => {
+        it('Should return a new vector with the negated values', () => { 
+            const vec = new Vec2(1, 2);
+            const negated = vec.getNegated();
+            
+            expect(negated).toEqual({
+                x: -1,
+                y: -2
+            });
+        })
+
+        it('Should not modify the original vector', () => {
+            const vec = new Vec2(1, 2);
+            const negated = vec.getNegated();
+
+            expect(negated).not.toBe(vec);
+            expect(vec).toEqual({
+                x: 1,
+                y: 2
+            });
+        })
+    })
 })