/**
   * @param fld Folder with files to match.
   * @param ptrn Pattern to match against file name.
   * @return Collection of matched files.
   */
  public static List<VisorLogFile> matchedFiles(File fld, final String ptrn) {
    List<VisorLogFile> files =
        fileTree(
            fld,
            MAX_FOLDER_DEPTH,
            new FileFilter() {
              @Override
              public boolean accept(File f) {
                return !f.isHidden()
                    && (f.isDirectory() || f.isFile() && f.getName().matches(ptrn));
              }
            });

    Collections.sort(files, LAST_MODIFIED);

    return files;
  }
  /**
   * Finds all files in folder and in it's sub-tree of specified depth.
   *
   * @param file Starting folder
   * @param maxDepth Depth of the tree. If 1 - just look in the folder, no sub-folders.
   * @param filter file filter.
   * @return List of found files.
   */
  public static List<VisorLogFile> fileTree(File file, int maxDepth, @Nullable FileFilter filter) {
    if (file.isDirectory()) {
      File[] files = (filter == null) ? file.listFiles() : file.listFiles(filter);

      if (files == null) return Collections.emptyList();

      List<VisorLogFile> res = new ArrayList<>(files.length);

      for (File f : files) {
        if (f.isFile() && f.length() > 0) res.add(new VisorLogFile(f));
        else if (maxDepth > 1) res.addAll(fileTree(f, maxDepth - 1, filter));
      }

      return res;
    }

    return F.asList(new VisorLogFile(file));
  }
  /**
   * Grabs local events and detects if events was lost since last poll.
   *
   * @param ignite Target grid.
   * @param evtOrderKey Unique key to take last order key from node local map.
   * @param evtThrottleCntrKey Unique key to take throttle count from node local map.
   * @param evtTypes Event types to collect.
   * @param evtMapper Closure to map grid events to Visor data transfer objects.
   * @return Collections of node events
   */
  public static Collection<VisorGridEvent> collectEvents(
      Ignite ignite,
      String evtOrderKey,
      String evtThrottleCntrKey,
      final int[] evtTypes,
      IgniteClosure<Event, VisorGridEvent> evtMapper) {
    assert ignite != null;
    assert evtTypes != null && evtTypes.length > 0;

    ConcurrentMap<String, Long> nl = ignite.cluster().nodeLocalMap();

    final long lastOrder = getOrElse(nl, evtOrderKey, -1L);
    final long throttle = getOrElse(nl, evtThrottleCntrKey, 0L);

    // When we first time arrive onto a node to get its local events,
    // we'll grab only last those events that not older than given period to make sure we are
    // not grabbing GBs of data accidentally.
    final long notOlderThan = System.currentTimeMillis() - EVENTS_COLLECT_TIME_WINDOW;

    // Flag for detecting gaps between events.
    final AtomicBoolean lastFound = new AtomicBoolean(lastOrder < 0);

    IgnitePredicate<Event> p =
        new IgnitePredicate<Event>() {
          /** */
          private static final long serialVersionUID = 0L;

          @Override
          public boolean apply(Event e) {
            // Detects that events were lost.
            if (!lastFound.get() && (lastOrder == e.localOrder())) lastFound.set(true);

            // Retains events by lastOrder, period and type.
            return e.localOrder() > lastOrder
                && e.timestamp() > notOlderThan
                && F.contains(evtTypes, e.type());
          }
        };

    Collection<Event> evts = ignite.events().localQuery(p);

    // Update latest order in node local, if not empty.
    if (!evts.isEmpty()) {
      Event maxEvt = Collections.max(evts, EVTS_ORDER_COMPARATOR);

      nl.put(evtOrderKey, maxEvt.localOrder());
    }

    // Update throttle counter.
    if (!lastFound.get())
      nl.put(evtThrottleCntrKey, throttle == 0 ? EVENTS_LOST_THROTTLE : throttle - 1);

    boolean lost = !lastFound.get() && throttle == 0;

    Collection<VisorGridEvent> res = new ArrayList<>(evts.size() + (lost ? 1 : 0));

    if (lost) res.add(new VisorGridEventsLost(ignite.cluster().localNode().id()));

    for (Event e : evts) {
      VisorGridEvent visorEvt = evtMapper.apply(e);

      if (visorEvt != null) res.add(visorEvt);
    }

    return res;
  }