(tLN) Fetch used supervision instances

[danyill]

It is often useful to be able to retrieve all used supervision instances.

We currently have:

/**
 * Returns the used supervision LN instances for a given service type.
 *
 * @param doc - SCL document.
 * @param serviceType - either GOOSE or SMV.
 * @returns - array of Elements of supervision LN instances.
 */
export function getUsedSupervisionInstances(
  doc: Document,
  serviceType: string
): Element[] {
  if (!doc) return [];
  const supervisionType = serviceType === 'GOOSE' ? 'LGOS' : 'LSVS';
  const refSelector =
    supervisionType === 'LGOS' ? 'DOI[name="GoCBRef"]' : 'DOI[name="SvCBRef"]';

  const supervisionInstances = Array.from(
    doc!.querySelectorAll(
      `:root > IED > AccessPoint > Server > LDevice > LN[lnClass="${supervisionType}"]>${refSelector}>DAI[name="setSrcRef"]>Val`
    )
  )
    .filter(val => val.textContent !== '')
    .map(val => val.closest('LN')!);

  return supervisionInstances;
}