package main

type shuffleDirection int

const (
	left shuffleDirection = iota
	right
)

// shuffle creates a new list where an element in one position is repositioned
// to the index of another element. All affected elements then shuffle one place to the left
// or right depending on the direction of the move.
func shuffle(list []any, oldPos, newPos int) []any {
	var direction shuffleDirection

	if newPos < oldPos {
		direction = right
	} else {
		direction = left
	}

	newList := make([]any, len(list))

	for i := range list {
		switch {
		case (direction == right) && (i < newPos || i > oldPos):
			newList[i] = list[i]
		case (direction == right) && (i == oldPos):
			newList[newPos] = list[i]
		case (direction == right):
			newList[i+1] = list[i]
		case (direction == left) && (i < oldPos || i > newPos):
			newList[i] = list[i]
		case (direction == left) && (i == oldPos):
			newList[newPos] = list[i]
		case (direction == left):
			newList[i-1] = list[i]
		}
	}

	return newList
}