gistfile1.txt

export type TelemetryDefinitionsParams = [
  string,
  NodeId[],
  Opt<Moment>,
  number
];

type Output = RequestStatus<Error, TelemetryStreamDefinition[]>;

export const useTelemetryStreamDefinitions = (): Output => {
  const query = useSelector(selectQueryToExecute);
  const selection = useSelector(selectTelemetryComponentSelection);
  const timeoutInSeconds = useSelector(selectDefaultAjaxRequestTimeout);
  const timestamp = useSelector(selectedTimestamp);

  const definitions$ = useObservable<Output, TelemetryDefinitionsParams>(getTelemetryDefinitions, [
    query,
    selection,
    timestamp,
    timeoutInSeconds
  ]);
  return useObservableState(definitions$, loadingStatus());
};

export function getTelemetryDefinitions(props: Observable<TelemetryDefinitionsParams>): Observable<Output> {
  const ONE_MINUTE = 60000; // 1 minute

  const requestProps = props.pipe(
    map(([query, selection, queryTime, timeoutInSeconds]) => ({
      query,
      selection,
      queryTime,
      timeoutInSeconds
    })),
    distinctUntilChanged(isEqual)
  );

  const requestPast = requestProps.pipe(
    filter(request => request.queryTime.isPresent()),
    flatMap(({ query, selection, queryTime, timeoutInSeconds }) =>
      requestTelemetryDefinitionsObservable({
        query,
        selection,
        queryTime,
        timeoutInSeconds
      })
    )
  );

  const pollLive = pollRequest({
    startPoll: requestProps.pipe(filter(request => request.queryTime.isAbsent())),
    stopPoll: requestProps.pipe(
      filter(request => request.queryTime.isPresent()),
      mapTo(undefined)
    ),
    request: requestTelemetryDefinitionsObservable,
    interval: ONE_MINUTE
  });

  return merge(requestPast, pollLive);
}