package board

// moveAndShuffle creates a new list where the element specified at the index of the current
// position is moved to the index of the target position. Elements within the range of the
// old and new positions will then shuffle forwards or backwards in the list depending on the
// direction of the move.
// This is currently used to move specified columns forwards or backwards on the Kanban board.
// When a column changes position the other columns shuffle forward or backwards as required.
func moveAndShuffle(input []Status, oldIndex, newIndex int) []Status {
	if newIndex == oldIndex {
		return input
	}

	output := make([]Status, len(input))

	// copy the original slice and assign the target element to the
	// new index.
	copy(output, input)

	output[newIndex] = input[oldIndex]

	// shuffle the elements in range down the slice if the target element moves
	// up the list.
	if newIndex < oldIndex {
		for index := newIndex; index <= oldIndex; index++ {
			if index == oldIndex {
				continue
			}

			output[index+1] = input[index]
		}

		return output
	}

	// shuffle the elements in range up the slice if the target element moves
	// down the list.
	for index := oldIndex; index <= newIndex; index++ {
		if index == oldIndex {
			continue
		}

		output[index-1] = input[index]
	}

	return output
}