package snakesimulator

func (p Point) Copy() (pCopy *Point) {
	pCopy = &Point{
		X: p.X,
		Y: p.Y,
	}
	return
}

func (s *Snake) NewHead(direction Direction) (newHead *Point) {
	newHead = s.Points[0].Copy()
	switch direction {
	case Direction_Up:
		newHead.Y -= 1
	case Direction_Down:
		newHead.Y += 1
	case Direction_Right:
		newHead.X += 1
	case Direction_Left:
		newHead.X -= 1
	}
	return
}

func (s *Snake) Move(newHead *Point) {
	s.Points = s.Points[:len(s.Points)-1]
	s.Points = append([]*Point{newHead}, s.Points...)
}

func (s *Snake) Feed(food *Point) {
	s.Points = append([]*Point{food}, s.Points...)
}

func (s *Snake) SelfCollision(head *Point) int {
	for index, point := range s.Points[:len(s.Points)-1] {
		if point.X == head.X && point.Y == head.Y {
			return index
		}
	}

	return 0
}