Swap operator + for - in refactored method

Question

The Code below has the goal of making a move on an object on the Y axis of an object following the mouse (the code works), see that the code within the if and of else if are equal except by the operator + and - what would be the ways to refactor this duplicate code by changing only the line operators (only what is in bold):

mousePosition3D.y = Transform.position. y + (initialMousePosition. y - mousePosition3D.y);

private void SwipeContainer(Directions direction){
    if(direction == Directions.Top && transform.localPosition.y < maxTopPosition){
        Vector3 position = Input.mousePosition;

        Vector3 mousePosition3D = Camera.main.ScreenToWorldPoint(position);
        mousePosition3D.z = -1f;
        mousePosition3D.x = transform.position.x;
        mousePosition3D.y = transform.position.y + (initialMousePosition.y - mousePosition3D.y);

        transform.position = Vector3.MoveTowards(
            transform.position, mousePosition3D, speedMoviment * Time.deltaTime
        );
    }else if(direction == Directions.Bottom && transform.localPosition.y > maxBottomPosition){
        Vector3 position = Input.mousePosition;

        Vector3 mousePosition3D = Camera.main.ScreenToWorldPoint(position);
        mousePosition3D.z = -1f;
        mousePosition3D.x = transform.position.x;
        mousePosition3D.y = transform.position.y - (initialMousePosition.y - mousePosition3D.y);

        transform.position = Vector3.MoveTowards(
            transform.position, mousePosition3D, speedMoviment * Time.deltaTime
        );
    }

This refactoring problem does not apply only to this language (C#) and specific situation, what would be the appropriate forms of refactoring (which is applicable to most languages such as: C#, Java, PHP, Javascript, C)

Answer 1

Apply your algebra knowledge:

x + y = x + (1)*y
x - y = x + (-1)*y

Create a new method and put this repeated code on it, use the one that has the signal + and multiply the section (initialMousePosition.y - mousePosition3D.y) at the value passed to the method.

Call this method by passing 1 or - 1 depending on whether you want to add or subtract.

private void SwipeContainer(Directions direction){
    if(direction == Directions.Top && transform.localPosition.y < maxTopPosition){
        movimenta(1);
    }else if(direction == Directions.Bottom && transform.localPosition.y > maxBottomPosition){
        movimenta(-1);
    }
}

private void movimenta(int direcao){
    Vector3 position = Input.mousePosition;

    Vector3 mousePosition3D = Camera.main.ScreenToWorldPoint(position);
    mousePosition3D.z = -1f;
    mousePosition3D.x = transform.position.x;
    mousePosition3D.y = transform.position.y + direcao * (initialMousePosition.y - mousePosition3D.y);

    transform.position = Vector3.MoveTowards(
        transform.position, mousePosition3D, speedMoviment * Time.deltaTime
    );
}