Collision detection system

collision/types.go

@@ -0,0 +1,87 @@
+package collision
+
+type Point struct {
+	X float64
+	Y float64
+}
+
+type Polygon struct {
+	Points []Point
+}
+
+type ObjectType int
+
+const (
+	Hero ObjectType = 1 << iota
+	Zombie
+)
+
+type Collidable interface {
+	CollisionShape() Polygon
+	HandleCollisionEvent(other Collidable)
+	CollisionObjectType() ObjectType
+}
+
+// Helper function to calculate the dot product of two points
+func dot(p1, p2 Point) float64 {
+	return p1.X*p2.X + p1.Y*p2.Y
+}
+
+// Helper function to get the normal of the edge between two points
+func edgeNormal(p1, p2 Point) Point {
+	return Point{X: p2.Y - p1.Y, Y: p1.X - p2.X}
+}
+
+// Project a polygon onto an axis and return the min and max projections
+func projectPolygon(axis Point, polygon Polygon) (float64, float64) {
+	min := dot(axis, polygon.Points[0])
+	max := min
+	for _, p := range polygon.Points[1:] {
+		projection := dot(axis, p)
+		if projection < min {
+			min = projection
+		}
+		if projection > max {
+			max = projection
+		}
+	}
+	return min, max
+}
+
+// Check if two projections on an axis overlap
+func overlap(minA, maxA, minB, maxB float64) bool {
+	if minA > maxB || minB > maxA {
+		return false
+	}
+	return true
+}
+
+// Overlaps checks if two polygons overlap using the Separating Axis Theorem
+func (p Polygon) Overlaps(p2 Polygon) bool {
+	if len(p.Points) == 0 || len(p2.Points) == 0 {
+		return false
+	}
+	for i := 0; i < len(p.Points); i++ {
+		next := (i + 1) % len(p.Points)
+		axis := edgeNormal(p.Points[i], p.Points[next])
+		minA, maxA := projectPolygon(axis, p)
+		minB, maxB := projectPolygon(axis, p2)
+
+		if !overlap(minA, maxA, minB, maxB) {
+			return false
+		}
+	}
+
+	for i := 0; i < len(p2.Points); i++ {
+		next := (i + 1) % len(p2.Points)
+		axis := edgeNormal(p2.Points[i], p2.Points[next])
+		minA, maxA := projectPolygon(axis, p)
+		minB, maxB := projectPolygon(axis, p2)
+
+		if !overlap(minA, maxA, minB, maxB) {
+			return false
+		}
+	}
+
+	return true
+}