private func handlePan(_ recognizer: UIPanGestureRecognizer) {
  ...
  switch recognizer.state {
    case .began:
      ...
    case .changed:
            if internalScrollViewController.scrollView.contentOffset.y > 0 {
                return
            } else {
                let maxY = max(SnapPosition.top.computedValue, lastY + deltaY)
                let minY = min(SnapPosition.bottom.computedValue, maxY)

                containerView.frame = initialFrame.offsetBy(dx: 0, dy: minY)
            }
    case .failed, .ended, .cancelled:
            ...
    default:
        break
    }
}