@NotNull
  private VirtualFilePointerImpl getOrCreate(
      @NotNull Disposable parentDisposable,
      @Nullable VirtualFilePointerListener listener,
      @NotNull String path,
      @NotNull Pair<VirtualFile, String> fileAndUrl) {
    FilePointerPartNode root = myPointers.get(listener);
    FilePointerPartNode node;
    if (root == null) {
      root = new FilePointerPartNode(path, null, fileAndUrl);
      myPointers.put(listener, root);
      node = root;
    } else {
      node = root.findPointerOrCreate(path, 0, fileAndUrl);
    }

    VirtualFilePointerImpl pointer;
    if (node.leaf == null) {
      pointer = new VirtualFilePointerImpl(listener, parentDisposable, fileAndUrl);
      node.associate(pointer, fileAndUrl);
    } else {
      pointer = node.leaf;
    }
    pointer.myNode.incrementUsageCount(1);

    root.checkConsistency();
    return pointer;
  }
  @Override
  public void after(@NotNull final List<? extends VFileEvent> events) {
    incModificationCount();

    for (FilePointerPartNode node : myPointersToUpdateUrl) {
      synchronized (this) {
        VirtualFilePointerImpl pointer = node.leaf;
        String urlBefore = pointer.getUrlNoUpdate();
        Pair<VirtualFile, String> after = node.update();
        String urlAfter = after.second;
        if (URL_COMPARATOR.compare(urlBefore, urlAfter) != 0) {
          // url has changed, reinsert
          FilePointerPartNode root = myPointers.get(pointer.getListener());
          int useCount = node.useCount;
          node.remove();
          FilePointerPartNode newNode =
              root.findPointerOrCreate(VfsUtilCore.urlToPath(urlAfter), 0, after);
          VirtualFilePointerImpl existingPointer = newNode.leaf;
          if (existingPointer != null) {
            // can happen when e.g. file renamed to the existing file
            // merge two pointers
            pointer.myNode = newNode;
          } else {
            newNode.associate(pointer, after);
          }
          newNode.incrementUsageCount(useCount);
        }
      }
    }

    VirtualFilePointer[] pointersToFireArray = toPointers(myPointersToFire);
    for (VirtualFilePointer pointer : pointersToFireArray) {
      ((VirtualFilePointerImpl) pointer).myNode.update();
    }

    for (EventDescriptor event : myEvents) {
      event.fireAfter();
    }

    if (pointersToFireArray.length != 0) {
      myBus.syncPublisher(VirtualFilePointerListener.TOPIC).validityChanged(pointersToFireArray);
    }

    myPointersToUpdateUrl = Collections.emptyList();
    myEvents = Collections.emptyList();
    myPointersToFire = Collections.emptyList();
    for (FilePointerPartNode root : myPointers.values()) {
      root.checkConsistency();
    }
  }