@jupyterlab/filebrowser/src/listing.ts

JupyterLab - FileBrowser Widget

// Copyright (c) Jupyter Development Team.
// Distributed under the terms of the Modified BSD License.

import {
  Dialog,
  DOMUtils,
  showDialog,
  showErrorMessage
} from '@jupyterlab/apputils';
import { PageConfig, PathExt, Time } from '@jupyterlab/coreutils';
import {
  IDocumentManager,
  isValidFileName,
  renameFile
} from '@jupyterlab/docmanager';
import { DocumentRegistry } from '@jupyterlab/docregistry';
import { Contents } from '@jupyterlab/services';
import { IStateDB } from '@jupyterlab/statedb';
import {
  ITranslator,
  nullTranslator,
  TranslationBundle
} from '@jupyterlab/translation';
import {
  caretDownIcon,
  caretUpIcon,
  classes,
  LabIcon
} from '@jupyterlab/ui-components';
import { ArrayExt, filter, StringExt } from '@lumino/algorithm';
import {
  MimeData,
  PromiseDelegate,
  ReadonlyJSONObject
} from '@lumino/coreutils';
import { ElementExt } from '@lumino/domutils';
import { DisposableDelegate, IDisposable } from '@lumino/disposable';
import { Drag } from '@lumino/dragdrop';
import { Message, MessageLoop } from '@lumino/messaging';
import { ISignal, Signal } from '@lumino/signaling';
import { h, VirtualDOM } from '@lumino/virtualdom';
import { Widget } from '@lumino/widgets';
import { FilterFileBrowserModel } from './model';

/**
 * The class name added to DirListing widget.
 */
const DIR_LISTING_CLASS = 'jp-DirListing';

/**
 * The class name added to a dir listing header node.
 */
const HEADER_CLASS = 'jp-DirListing-header';

/**
 * The class name added to a dir listing list header cell.
 */
const HEADER_ITEM_CLASS = 'jp-DirListing-headerItem';

/**
 * The class name added to a header cell text node.
 */
const HEADER_ITEM_TEXT_CLASS = 'jp-DirListing-headerItemText';

/**
 * The class name added to a header cell icon node.
 */
const HEADER_ITEM_ICON_CLASS = 'jp-DirListing-headerItemIcon';

/**
 * The class name added to the dir listing content node.
 */
const CONTENT_CLASS = 'jp-DirListing-content';

/**
 * The class name added to dir listing content item.
 */
const ITEM_CLASS = 'jp-DirListing-item';

/**
 * The class name added to the listing item text cell.
 */
const ITEM_TEXT_CLASS = 'jp-DirListing-itemText';

/**
 * The class name added to the listing item text cell.
 */
const ITEM_NAME_COLUMN_CLASS = 'jp-DirListing-itemName';

/**
 * The class name added to the listing item icon cell.
 */
const ITEM_ICON_CLASS = 'jp-DirListing-itemIcon';

/**
 * The class name added to the listing item modified cell.
 */
const ITEM_MODIFIED_CLASS = 'jp-DirListing-itemModified';

/**
 * The class name added to the listing item file size cell.
 */
const ITEM_FILE_SIZE_CLASS = 'jp-DirListing-itemFileSize';

/**
 * The class name added to the label element that wraps each item's checkbox and
 * the header's check-all checkbox.
 */
const CHECKBOX_WRAPPER_CLASS = 'jp-DirListing-checkboxWrapper';

/**
 * The class name added to the dir listing editor node.
 */
const EDITOR_CLASS = 'jp-DirListing-editor';

/**
 * The class name added to the name column header cell.
 */
const NAME_ID_CLASS = 'jp-id-name';

/**
 * The class name added to the modified column header cell.
 */
const MODIFIED_ID_CLASS = 'jp-id-modified';

/**
 * The class name added to the file size column header cell.
 */
const FILE_SIZE_ID_CLASS = 'jp-id-filesize';

/**
 * The mime type for a contents drag object.
 */
const CONTENTS_MIME = 'application/x-jupyter-icontents';

/**
 * The mime type for a rich contents drag object.
 */
const CONTENTS_MIME_RICH = 'application/x-jupyter-icontentsrich';

/**
 * The class name added to drop targets.
 */
const DROP_TARGET_CLASS = 'jp-mod-dropTarget';

/**
 * The class name added to selected rows.
 */
const SELECTED_CLASS = 'jp-mod-selected';

/**
 * The class name added to drag state icons to add space between the icon and the file name
 */
const DRAG_ICON_CLASS = 'jp-DragIcon';

/**
 * The class name added to column resize handle.
 */
const RESIZE_HANDLE_CLASS = 'jp-DirListing-resizeHandle';

/**
 * The class name added to the widget when there are items on the clipboard.
 */
const CLIPBOARD_CLASS = 'jp-mod-clipboard';

/**
 * The class name added to cut rows.
 */
const CUT_CLASS = 'jp-mod-cut';

/**
 * The class name added when there are more than one selected rows.
 */
const MULTI_SELECTED_CLASS = 'jp-mod-multiSelected';

/**
 * The class name added to indicate running notebook.
 */
const RUNNING_CLASS = 'jp-mod-running';

/**
 * The class name added to indicate the active element.
 */
const ACTIVE_CLASS = 'jp-mod-active';

/**
 * The class name added for a descending sort.
 */
const DESCENDING_CLASS = 'jp-mod-descending';

/**
 * The maximum duration between two key presses when selecting files by prefix.
 */
const PREFIX_APPEND_DURATION = 1000;

/**
 * The default width of the resize handle.
 */
const DEFAULT_HANDLE_WIDTH = 5;

/**
 * The threshold in pixels to start a drag event.
 */
const DRAG_THRESHOLD = 5;

/**
 * A boolean indicating whether the platform is Mac.
 */
const IS_MAC = !!navigator.platform.match(/Mac/i);

/**
 * The factory MIME type supported by lumino dock panels.
 */
const FACTORY_MIME = 'application/vnd.lumino.widget-factory';

/**
 * A widget which hosts a file list area.
 */
export class DirListing extends Widget {
  /**
   * Construct a new file browser directory listing widget.
   *
   * @param options The constructor options
   */
  constructor(options: DirListing.IOptions) {
    super({
      node: (options.renderer || DirListing.defaultRenderer).createNode()
    });
    this.addClass(DIR_LISTING_CLASS);
    this.translator = options.translator || nullTranslator;
    this._trans = this.translator.load('jupyterlab');
    this._model = options.model;
    this._model.fileChanged.connect(this._onFileChanged, this);
    this._model.refreshed.connect(this._onModelRefreshed, this);
    this._model.pathChanged.connect(this._onPathChanged, this);
    this._editNode = document.createElement('input');
    this._editNode.className = EDITOR_CLASS;
    this._manager = this._model.manager;
    this._renderer = options.renderer || DirListing.defaultRenderer;
    this._state = options.state || null;

    // Get the width of the "modified" column
    this._updateModifiedSize(this.node);

    const headerNode = DOMUtils.findElement(this.node, HEADER_CLASS);
    // hide the file size column by default
    this._hiddenColumns.add('file_size');
    this._renderer.populateHeaderNode(
      headerNode,
      this.translator,
      this._hiddenColumns,
      this._columnSizes
    );
    this._manager.activateRequested.connect(this._onActivateRequested, this);
  }

  /**
   * Dispose of the resources held by the directory listing.
   */
  dispose(): void {
    this._items.length = 0;
    this._sortedItems.length = 0;
    this._clipboard.length = 0;
    super.dispose();
  }

  /**
   * Get the model used by the listing.
   */
  get model(): FilterFileBrowserModel {
    return this._model;
  }

  /**
   * Get the dir listing header node.
   *
   * #### Notes
   * This is the node which holds the header cells.
   *
   * Modifying this node directly can lead to undefined behavior.
   */
  get headerNode(): HTMLElement {
    return DOMUtils.findElement(this.node, HEADER_CLASS);
  }

  /**
   * Get the dir listing content node.
   *
   * #### Notes
   * This is the node which holds the item nodes.
   *
   * Modifying this node directly can lead to undefined behavior.
   */
  get contentNode(): HTMLElement {
    return DOMUtils.findElement(this.node, CONTENT_CLASS);
  }

  /**
   * The renderer instance used by the directory listing.
   */
  get renderer(): DirListing.IRenderer {
    return this._renderer;
  }

  /**
   * The current sort state.
   */
  get sortState(): DirListing.ISortState {
    return this._sortState;
  }

  /**
   * A signal fired when an item is opened.
   */
  get onItemOpened(): ISignal<DirListing, Contents.IModel> {
    return this._onItemOpened;
  }

  /**
   * Create an iterator over the listing's selected items.
   *
   * @returns A new iterator over the listing's selected items.
   */
  selectedItems(): IterableIterator<Contents.IModel> {
    const items = this._sortedItems;
    return filter(items, item => this.selection[item.path]);
  }

  /**
   * Create an iterator over the listing's sorted items.
   *
   * @returns A new iterator over the listing's sorted items.
   */
  sortedItems(): IterableIterator<Contents.IModel> {
    return this._sortedItems[Symbol.iterator]();
  }

  /**
   * Sort the items using a sort condition.
   */
  sort(state: DirListing.ISortState): void {
    this._sortedItems = Private.sort(
      this.model.items(),
      state,
      this._sortNotebooksFirst,
      this.translator
    );
    this._sortState = state;
    this.update();
  }

  /**
   * Rename the first currently selected item.
   *
   * @returns A promise that resolves with the new name of the item.
   */
  rename(): Promise<string> {
    return this._doRename();
  }

  /**
   * Cut the selected items.
   */
  cut(): void {
    this._isCut = true;
    this._copy();
    this.update();
  }

  /**
   * Copy the selected items.
   */
  copy(): void {
    this._copy();
  }

  /**
   * Paste the items from the clipboard.
   *
   * @returns A promise that resolves when the operation is complete.
   */
  paste(): Promise<void> {
    if (!this._clipboard.length) {
      this._isCut = false;
      return Promise.resolve(undefined);
    }

    const basePath = this._model.path;
    const promises: Promise<Contents.IModel>[] = [];

    for (const path of this._clipboard) {
      if (this._isCut) {
        const localPath = this._manager.services.contents.localPath(path);
        const parts = localPath.split('/');
        const name = parts[parts.length - 1];
        const newPath = PathExt.join(basePath, name);
        promises.push(this._model.manager.rename(path, newPath));
      } else {
        promises.push(this._model.manager.copy(path, basePath));
      }
    }

    // Remove any cut modifiers.
    for (const item of this._items) {
      item.classList.remove(CUT_CLASS);
    }

    this._clipboard.length = 0;
    this._isCut = false;
    this.removeClass(CLIPBOARD_CLASS);
    return Promise.all(promises)
      .then(() => {
        return undefined;
      })
      .catch(error => {
        void showErrorMessage(
          this._trans._p('showErrorMessage', 'Paste Error'),
          error
        );
      });
  }

  /**
   * Delete the currently selected item(s).
   *
   * @returns A promise that resolves when the operation is complete.
   */
  async delete(): Promise<void> {
    const deleteToTrash = PageConfig.getOption('delete_to_trash') === 'true';
    const items = this._sortedItems.filter(item => this.selection[item.path]);

    if (!items.length) {
      return;
    }
    const moveToTrashActionMessage = this._trans.__(
      'Are you sure you want to move to trash: %1?',
      items[0].name
    );
    const deleteActionMessage = this._trans.__(
      'Are you sure you want to permanently delete: %1?',
      items[0].name
    );
    const moveToTrashItemsActionMessage = this._trans._n(
      'Are you sure you want to move to trash the %1 selected item?',
      'Are you sure you want to move to trash the %1 selected items?',
      items.length
    );
    const deleteActionItemsMessage = this._trans._n(
      'Are you sure you want to permanently delete the %1 selected item?',
      'Are you sure you want to permanently delete the %1 selected items?',
      items.length
    );

    const actionMessage = deleteToTrash
      ? moveToTrashActionMessage
      : deleteActionMessage;
    const itemsActionMessage = deleteToTrash
      ? moveToTrashItemsActionMessage
      : deleteActionItemsMessage;
    const actionName = deleteToTrash
      ? this._trans.__('Move to Trash')
      : this._trans.__('Delete');
    const message = items.length === 1 ? actionMessage : itemsActionMessage;
    const result = await showDialog({
      title: actionName,
      body: message,
      buttons: [
        Dialog.cancelButton({ label: this._trans.__('Cancel') }),
        Dialog.warnButton({ label: actionName })
      ],
      // By default focus on "Cancel" to protect from accidental deletion
      // ("delete" and "Enter" are next to each other on many keyboards).
      defaultButton: 0
    });

    if (!this.isDisposed && result.button.accept) {
      await this._delete(items.map(item => item.path));
    }

    // Re-focus
    let focusIndex = this._focusIndex;
    const lastIndexAfterDelete = this._sortedItems.length - items.length - 1;
    if (focusIndex > lastIndexAfterDelete) {
      // If the focus index after deleting items is out of bounds, set it to the
      // last item.
      focusIndex = Math.max(0, lastIndexAfterDelete);
    }
    this._focusItem(focusIndex);
  }

  /**
   * Duplicate the currently selected item(s).
   *
   * @returns A promise that resolves when the operation is complete.
   */
  duplicate(): Promise<void> {
    const basePath = this._model.path;
    const promises: Promise<Contents.IModel>[] = [];

    for (const item of this.selectedItems()) {
      if (item.type !== 'directory') {
        promises.push(this._model.manager.copy(item.path, basePath));
      }
    }
    return Promise.all(promises)
      .then(() => {
        return undefined;
      })
      .catch(error => {
        void showErrorMessage(
          this._trans._p('showErrorMessage', 'Duplicate file'),
          error
        );
      });
  }

  /**
   * Download the currently selected item(s).
   */
  async download(): Promise<void> {
    await Promise.all(
      Array.from(this.selectedItems())
        .filter(item => item.type !== 'directory')
        .map(item => this._model.download(item.path))
    );
  }

  /**
   * Restore the state of the file browser listing.
   *
   * @param id - The unique ID that is used to construct a state database key.
   *
   */
  async restore(id: string): Promise<void> {
    const key = `file-browser-${id}:columns`;
    const state = this._state;
    this._stateColumnsKey = key;

    if (!state) {
      return;
    }

    try {
      const columns = await state.fetch(key);

      if (!columns) {
        return;
      }

      const sizes = (columns as ReadonlyJSONObject)['sizes'] as
        | Record<DirListing.IColumn['id'], number | null>
        | undefined;

      if (!sizes) {
        return;
      }
      for (const [key, size] of Object.entries(sizes)) {
        this._columnSizes[key as DirListing.IColumn['id']] = size;
      }
      this._updateColumnSizes();
    } catch (error) {
      await state.remove(key);
    }
  }
  private _stateColumnsKey: string;

  /**
   * Shut down kernels on the applicable currently selected items.
   *
   * @returns A promise that resolves when the operation is complete.
   */
  shutdownKernels(): Promise<void> {
    const model = this._model;
    const items = this._sortedItems;
    const paths = items.map(item => item.path);

    const promises = Array.from(this._model.sessions())
      .filter(session => {
        const index = ArrayExt.firstIndexOf(paths, session.path);
        return this.selection[items[index].path];
      })
      .map(session => model.manager.services.sessions.shutdown(session.id));

    return Promise.all(promises)
      .then(() => {
        return undefined;
      })
      .catch(error => {
        void showErrorMessage(
          this._trans._p('showErrorMessage', 'Shut down kernel'),
          error
        );
      });
  }

  /**
   * Select next item.
   *
   * @param keepExisting - Whether to keep the current selection and add to it.
   */
  selectNext(keepExisting = false): void {
    let index = -1;
    const selected = Object.keys(this.selection);
    const items = this._sortedItems;
    if (selected.length === 1 || keepExisting) {
      // Select the next item.
      const path = selected[selected.length - 1];
      index = ArrayExt.findFirstIndex(items, value => value.path === path);
      index += 1;
      if (index === this._items.length) {
        index = 0;
      }
    } else if (selected.length === 0) {
      // Select the first item.
      index = 0;
    } else {
      // Select the last selected item.
      const path = selected[selected.length - 1];
      index = ArrayExt.findFirstIndex(items, value => value.path === path);
    }
    if (index !== -1) {
      this._selectItem(index, keepExisting);
      ElementExt.scrollIntoViewIfNeeded(this.contentNode, this._items[index]);
    }
  }

  /**
   * Select previous item.
   *
   * @param keepExisting - Whether to keep the current selection and add to it.
   */
  selectPrevious(keepExisting = false): void {
    let index = -1;
    const selected = Object.keys(this.selection);
    const items = this._sortedItems;
    if (selected.length === 1 || keepExisting) {
      // Select the previous item.
      const path = selected[0];
      index = ArrayExt.findFirstIndex(items, value => value.path === path);
      index -= 1;
      if (index === -1) {
        index = this._items.length - 1;
      }
    } else if (selected.length === 0) {
      // Select the last item.
      index = this._items.length - 1;
    } else {
      // Select the first selected item.
      const path = selected[0];
      index = ArrayExt.findFirstIndex(items, value => value.path === path);
    }
    if (index !== -1) {
      this._selectItem(index, keepExisting);
      ElementExt.scrollIntoViewIfNeeded(this.contentNode, this._items[index]);
    }
  }

  /**
   * Select the first item that starts with prefix being typed.
   */
  selectByPrefix(): void {
    const prefix = this._searchPrefix.toLowerCase();
    const items = this._sortedItems;

    const index = ArrayExt.findFirstIndex(items, value => {
      return value.name.toLowerCase().substr(0, prefix.length) === prefix;
    });

    if (index !== -1) {
      this._selectItem(index, false);
      ElementExt.scrollIntoViewIfNeeded(this.contentNode, this._items[index]);
    }
  }

  /**
   * Get whether an item is selected by name.
   *
   * @param name - The name of of the item.
   *
   * @returns Whether the item is selected.
   */
  isSelected(name: string): boolean {
    const items = this._sortedItems;

    return (
      Array.from(
        filter(items, item => item.name === name && this.selection[item.path])
      ).length !== 0
    );
  }

  /**
   * Find a model given a click.
   *
   * @param event - The mouse event.
   *
   * @returns The model for the selected file.
   */
  modelForClick(event: MouseEvent): Contents.IModel | undefined {
    const items = this._sortedItems;
    const index = Private.hitTestNodes(this._items, event);
    if (index !== -1) {
      return items[index];
    }
    return undefined;
  }

  /**
   * Clear the selected items.
   */
  clearSelectedItems(): void {
    this.selection = Object.create(null);
  }

  /**
   * Select an item by name.
   *
   * @param name - The name of the item to select.
   * @param focus - Whether to move focus to the selected item.
   *
   * @returns A promise that resolves when the name is selected.
   */
  async selectItemByName(name: string, focus: boolean = false): Promise<void> {
    return this._selectItemByName(name, focus);
  }

  /**
   * Select an item by name.
   *
   * @param name - The name of the item to select.
   * @param focus - Whether to move focus to the selected item.
   * @param force - Whether to proceed with selection even if the file was already selected.
   *
   * @returns A promise that resolves when the name is selected.
   */
  private async _selectItemByName(
    name: string,
    focus: boolean = false,
    force: boolean = false
  ): Promise<void> {
    if (!force && this.isSelected(name)) {
      // Avoid API polling and DOM updates if already selected
      return;
    }

    // Make sure the file is available.
    await this.model.refresh();

    if (this.isDisposed) {
      throw new Error('File browser is disposed.');
    }
    const items = this._sortedItems;
    const index = ArrayExt.findFirstIndex(items, value => value.name === name);
    if (index === -1) {
      throw new Error('Item does not exist.');
    }
    this._selectItem(index, false, focus);
    MessageLoop.sendMessage(this, Widget.Msg.UpdateRequest);
    ElementExt.scrollIntoViewIfNeeded(this.contentNode, this._items[index]);
  }
  /**
   * Handle the DOM events for the directory listing.
   *
   * @param event - The DOM event sent to the widget.
   *
   * #### Notes
   * This method implements the DOM `EventListener` interface and is
   * called in response to events on the panel's DOM node. It should
   * not be called directly by user code.
   */
  handleEvent(event: Event): void {
    switch (event.type) {
      case 'mousedown':
        this._evtMousedown(event as MouseEvent);
        break;
      case 'mouseup':
        this._evtMouseup(event as MouseEvent);
        break;
      case 'mousemove':
        this._evtMousemove(event as MouseEvent);
        break;
      case 'keydown':
        this.evtKeydown(event as KeyboardEvent);
        break;
      case 'click':
        this._evtClick(event as MouseEvent);
        break;
      case 'dblclick':
        this.evtDblClick(event as MouseEvent);
        break;
      case 'dragenter':
      case 'dragover':
        this.addClass('jp-mod-native-drop');
        event.preventDefault();
        break;
      case 'dragleave':
      case 'dragend':
        this.removeClass('jp-mod-native-drop');
        break;
      case 'drop':
        this.removeClass('jp-mod-native-drop');
        this.evtNativeDrop(event as DragEvent);
        break;
      case 'scroll':
        this._evtScroll(event as MouseEvent);
        break;
      case 'lm-dragenter':
        this.evtDragEnter(event as Drag.Event);
        break;
      case 'lm-dragleave':
        this.evtDragLeave(event as Drag.Event);
        break;
      case 'lm-dragover':
        this.evtDragOver(event as Drag.Event);
        break;
      case 'lm-drop':
        this.evtDrop(event as Drag.Event);
        break;
      default:
        break;
    }
  }

  /**
   * A message handler invoked on an `'after-attach'` message.
   */
  protected onAfterAttach(msg: Message): void {
    super.onAfterAttach(msg);
    const node = this.node;
    this._width = this._computeContentWidth();
    const content = DOMUtils.findElement(node, CONTENT_CLASS);
    node.addEventListener('mousedown', this);
    node.addEventListener('keydown', this);
    node.addEventListener('click', this);
    node.addEventListener('dblclick', this);
    this._contentSizeObserver.observe(content);
    content.addEventListener('dragenter', this);
    content.addEventListener('dragover', this);
    content.addEventListener('dragleave', this);
    content.addEventListener('dragend', this);
    content.addEventListener('drop', this);
    content.addEventListener('scroll', this);
    content.addEventListener('lm-dragenter', this);
    content.addEventListener('lm-dragleave', this);
    content.addEventListener('lm-dragover', this);
    content.addEventListener('lm-drop', this);
    this._updateColumnSizes();
  }

  /**
   * A message handler invoked on a `'before-detach'` message.
   */
  protected onBeforeDetach(msg: Message): void {
    super.onBeforeDetach(msg);
    const node = this.node;
    const content = DOMUtils.findElement(node, CONTENT_CLASS);
    node.removeEventListener('mousedown', this);
    node.removeEventListener('keydown', this);
    node.removeEventListener('click', this);
    node.removeEventListener('dblclick', this);
    this._contentSizeObserver.disconnect();
    content.removeEventListener('scroll', this);
    content.removeEventListener('dragover', this);
    content.removeEventListener('dragover', this);
    content.removeEventListener('dragleave', this);
    content.removeEventListener('dragend', this);
    content.removeEventListener('drop', this);
    content.removeEventListener('lm-dragenter', this);
    content.removeEventListener('lm-dragleave', this);
    content.removeEventListener('lm-dragover', this);
    content.removeEventListener('lm-drop', this);
    document.removeEventListener('mousemove', this, true);
    document.removeEventListener('mouseup', this, true);
  }

  /**
   * A message handler invoked on an `'after-show'` message.
   */
  protected onAfterShow(msg: Message): void {
    if (this._isDirty) {
      // Update the sorted items.
      this.sort(this.sortState);
      this.update();
    }
  }

  private _onContentResize(): void {
    const content = DOMUtils.findElement(this.node, CONTENT_CLASS);
    const scrollbarWidth = content.offsetWidth - content.clientWidth;
    if (scrollbarWidth != this._contentScrollbarWidth) {
      this._contentScrollbarWidth = scrollbarWidth;
      this._width = this._computeContentWidth();
      this._updateColumnSizes();
    }
  }

  private _computeContentWidth(width: number | null = null) {
    if (!width) {
      width = this.node.getBoundingClientRect().width;
    }

    this._paddingWidth = parseFloat(
      window
        .getComputedStyle(this.node)
        .getPropertyValue('--jp-dirlisting-padding-width')
    );

    const handle = this.node.querySelector(`.${RESIZE_HANDLE_CLASS}`);

    this._handleWidth = handle
      ? handle.getBoundingClientRect().width
      : DEFAULT_HANDLE_WIDTH;
    return width - this._paddingWidth * 2 - this._contentScrollbarWidth;
  }

  /**
   * Update the modified column's size
   */
  private _updateModifiedSize(node: HTMLElement) {
    // Look for the modified column's header
    const modified = DOMUtils.findElement(node, MODIFIED_ID_CLASS);
    this._modifiedWidth =
      this._columnSizes['last_modified'] ??
      modified?.getBoundingClientRect().width ??
      83;
    this._modifiedStyle =
      this._modifiedWidth < 100
        ? 'narrow'
        : this._modifiedWidth > 120
        ? 'long'
        : 'short';
  }

  /**
   * Rerender item nodes' modified dates, if the modified style has changed.
   */
  private _updateModifiedStyleAndSize() {
    const oldModifiedStyle = this._modifiedStyle;
    // Update both size and style
    this._updateModifiedSize(this.node);
    if (oldModifiedStyle !== this._modifiedStyle) {
      this.updateModified(this._sortedItems, this._items);
    }
  }

  /**
   * Update only the modified dates.
   */
  protected updateModified(items: Contents.IModel[], nodes: HTMLElement[]) {
    items.forEach((item, i) => {
      const node = nodes[i];
      if (node && item.last_modified) {
        const modified = DOMUtils.findElement(node, ITEM_MODIFIED_CLASS);
        if (this.renderer.updateItemModified !== undefined) {
          this.renderer.updateItemModified(
            modified,
            item.last_modified,
            this._modifiedStyle
          );
        } else {
          DirListing.defaultRenderer.updateItemModified(
            modified,
            item.last_modified,
            this._modifiedStyle
          );
        }
      }
    });
  }

  // Update item nodes based on widget state.
  protected updateNodes(
    items: Contents.IModel[],
    nodes: HTMLElement[],
    sizeOnly = false
  ) {
    items.forEach((item, i) => {
      const node = nodes[i];
      if (sizeOnly && this.renderer.updateItemSize) {
        if (!node) {
          // short-circuit in case if node is not yet ready
          return;
        }
        return this.renderer.updateItemSize(
          node,
          item,
          this._modifiedStyle,
          this._columnSizes
        );
      }
      const ft = this._manager.registry.getFileTypeForModel(item);
      this.renderer.updateItemNode(
        node,
        item,
        ft,
        this.translator,
        this._hiddenColumns,
        this.selection[item.path],
        this._modifiedStyle,
        this._columnSizes
      );
      if (
        this.selection[item.path] &&
        this._isCut &&
        this._model.path === this._prevPath
      ) {
        node.classList.add(CUT_CLASS);
      }

      // add metadata to the node
      node.setAttribute(
        'data-isdir',
        item.type === 'directory' ? 'true' : 'false'
      );
    });

    // Handle the selectors on the widget node.
    const selected = Object.keys(this.selection).length;
    if (selected) {
      this.addClass(SELECTED_CLASS);
      if (selected > 1) {
        this.addClass(MULTI_SELECTED_CLASS);
      }
    }

    // Handle file session statuses.
    const paths = items.map(item => item.path);
    for (const session of this._model.sessions()) {
      const index = ArrayExt.firstIndexOf(paths, session.path);
      const node = nodes[index];
      // Node may have been filtered out.
      if (node) {
        let name = session.kernel?.name;
        const specs = this._model.specs;

        node.classList.add(RUNNING_CLASS);
        if (specs && name) {
          const spec = specs.kernelspecs[name];
          name = spec ? spec.display_name : this._trans.__('unknown');
        }

        // Update node title only if it has changed.
        const prevState = this._lastRenderedState.get(node);
        if (prevState !== node.title) {
          node.title = this._trans.__('%1\nKernel: %2', node.title, name);
          this._lastRenderedState.set(node, node.title);
        }
      }
    }
  }

  /**
   * A handler invoked on an `'update-request'` message.
   */
  protected onUpdateRequest(msg: Message): void {
    this._isDirty = false;

    // Fetch common variables.
    const items = this._sortedItems;
    const nodes = this._items;
    // If we didn't get any item yet, we'll need to resize once items are added
    const needsResize = nodes.length === 0;
    const content = DOMUtils.findElement(this.node, CONTENT_CLASS);
    const renderer = this._renderer;

    this.removeClass(MULTI_SELECTED_CLASS);
    this.removeClass(SELECTED_CLASS);

    // Remove any excess item nodes.
    while (nodes.length > items.length) {
      content.removeChild(nodes.pop()!);
    }

    // Add any missing item nodes.
    while (nodes.length < items.length) {
      const node = renderer.createItemNode(
        this._hiddenColumns,
        this._columnSizes
      );
      node.classList.add(ITEM_CLASS);
      nodes.push(node);
      content.appendChild(node);
    }

    nodes.forEach((node, i) => {
      // Remove extra classes from the nodes.
      node.classList.remove(SELECTED_CLASS);
      node.classList.remove(RUNNING_CLASS);
      node.classList.remove(CUT_CLASS);

      // Uncheck each file checkbox
      const checkbox = renderer.getCheckboxNode(node);
      if (checkbox) {
        checkbox.checked = false;
      }

      // Handle `tabIndex` & `role`
      const nameNode = renderer.getNameNode(node);
      if (nameNode) {
        // Must check if the name node is there because it gets replaced by the
        // edit node when editing the name of the file or directory.
        if (i === this._focusIndex) {
          nameNode.setAttribute('tabIndex', '0');
          nameNode.setAttribute('role', 'button');
        } else {
          nameNode.setAttribute('tabIndex', '-1');
          nameNode.removeAttribute('role');
        }
      }
    });

    // Put the check-all checkbox in the header into the correct state
    const checkAllCheckbox = renderer.getCheckboxNode(this.headerNode);
    if (checkAllCheckbox) {
      const totalSelected = Object.keys(this.selection).length;
      const allSelected = items.length > 0 && totalSelected === items.length;
      const someSelected = !allSelected && totalSelected > 0;
      checkAllCheckbox.checked = allSelected;
      checkAllCheckbox.indeterminate = someSelected;
      // Stash the state in data attributes so we can access them in the click
      // handler (because in the click handler, checkbox.checked and
      // checkbox.indeterminate do not hold the previous value; they hold the
      // next value).
      checkAllCheckbox.dataset.checked = String(allSelected);
      checkAllCheckbox.dataset.indeterminate = String(someSelected);

      const trans = this.translator.load('jupyterlab');
      checkAllCheckbox?.setAttribute(
        'aria-label',
        allSelected || someSelected
          ? trans.__('Deselect all files and directories')
          : trans.__('Select all files and directories')
      );
    }

    this.updateNodes(items, nodes);

    if (needsResize) {
      this._width = this._computeContentWidth();
      this._updateColumnSizes();
    }

    this._prevPath = this._model.path;
  }

  onResize(msg: Widget.ResizeMessage): void {
    const { width } =
      msg.width === -1 ? this.node.getBoundingClientRect() : msg;
    this._width = this._computeContentWidth(width);
    this._updateColumnSizes();
  }

  setColumnVisibility(
    name: DirListing.ToggleableColumn,
    visible: boolean
  ): void {
    if (visible) {
      this._hiddenColumns.delete(name);
    } else {
      this._hiddenColumns.add(name);
    }

    this.headerNode.innerHTML = '';
    this._renderer.populateHeaderNode(
      this.headerNode,
      this.translator,
      this._hiddenColumns,
      this._columnSizes
    );

    this._updateColumnSizes();
  }

  private _updateColumnSizes(
    doNotGrowBeforeInclusive: DirListing.IColumn['id'] | null = null
  ) {
    // Adjust column sizes so that they add up to the total width available, preserving ratios
    const visibleColumns = this._visibleColumns
      .map(column => ({
        ...column,
        element: DOMUtils.findElement(this.node, column.className)
      }))
      .filter(column => {
        // While all visible column will have an element, some extensions like jupyter-unfold
        // do not render columns even if user requests them to be visible; this filter exists
        // to ensure backward compatibility with such extensions and may be removed in the future.
        return column.element;
      });

    // read from DOM
    let total = 0;
    for (const column of visibleColumns) {
      let size = this._columnSizes[column.id];
      if (size === null) {
        size = column.element.getBoundingClientRect().width;
      }
      // restrict the minimum and maximum width
      size = Math.max(size, column.minWidth);
      if (this._width) {
        let reservedForOtherColumns = 0;
        for (const other of visibleColumns) {
          if (other.id === column.id) {
            continue;
          }
          reservedForOtherColumns += other.minWidth;
        }
        size = Math.min(size, this._width - reservedForOtherColumns);
      }
      this._columnSizes[column.id] = size;
      total += size;
    }

    // Ensure that total fits
    if (this._width) {
      // Distribute the excess/shortfall over the columns which should stretch.
      const excess = this._width - total;
      let growAllowed = doNotGrowBeforeInclusive === null;
      const growColumns = visibleColumns.filter(c => {
        if (growAllowed) {
          return true;
        }
        if (c.id === doNotGrowBeforeInclusive) {
          growAllowed = true;
        }
        return false;
      });
      const totalWeight = growColumns
        .map(c => c.grow)
        .reduce((a, b) => a + b, 0);
      for (const column of growColumns) {
        // The value of `growBy` will be negative when the down-sizing
        const growBy = (excess * column.grow) / totalWeight;
        this._columnSizes[column.id] = this._columnSizes[column.id]! + growBy;
      }
    }

    const resizeHandles = this.node.getElementsByClassName(RESIZE_HANDLE_CLASS);
    const resizableColumns = visibleColumns.map(column =>
      Private.isResizable(column)
    );

    // Write to DOM
    let i = 0;
    for (const column of visibleColumns) {
      let size = this._columnSizes[column.id];

      if (Private.isResizable(column) && size) {
        size -=
          (this._handleWidth * resizeHandles.length) / resizableColumns.length;
        // if this is first resizable or last resizable column
        if (i === 0 || i === resizableColumns.length - 1) {
          size += this._paddingWidth;
        }
        i += 1;
      }
      column.element.style.width = size === null ? '' : size + 'px';
    }
    this._updateModifiedStyleAndSize();

    // Refresh sizes on the per item widths
    if (this.isVisible) {
      const items = this._items;
      if (items.length !== 0) {
        this.updateNodes(this._sortedItems, this._items, true);
      }
    }

    if (this._state && this._stateColumnsKey) {
      void this._state.save(this._stateColumnsKey, {
        sizes: this._columnSizes
      });
    }
  }

  private get _visibleColumns() {
    return DirListing.columns.filter(
      column => column.id === 'name' || !this._hiddenColumns?.has(column.id)
    );
  }

  private _setColumnSize(
    name: DirListing.ResizableColumn,
    size: number | null
  ): void {
    const previousSize = this._columnSizes[name];
    if (previousSize && size && size > previousSize) {
      // check if we can resize up
      let total = 0;
      let before = true;
      for (const column of this._visibleColumns) {
        if (column.id === name) {
          // add proposed size for the current columns
          total += size;
          before = false;
          continue;
        }
        if (before) {
          // add size as-is for columns before
          const element = DOMUtils.findElement(this.node, column.className);
          total +=
            this._columnSizes[column.id] ??
            element.getBoundingClientRect().width;
        } else {
          // add minimum acceptable size for columns after
          total += column.minWidth;
        }
      }
      if (this._width && total > this._width) {
        // up sizing is no longer possible
        return;
      }
    }
    this._columnSizes[name] = size;
    this._updateColumnSizes(name);
  }

  /**
   * Update the setting to sort notebooks above files.
   * This sorts the items again if the internal value is modified.
   */
  setNotebooksFirstSorting(isEnabled: boolean) {
    let previousValue = this._sortNotebooksFirst;
    this._sortNotebooksFirst = isEnabled;
    if (this._sortNotebooksFirst !== previousValue) {
      this.sort(this._sortState);
    }
  }

  /**
   * Update the setting to allow single click navigation.
   * This enables opening files/directories with a single click.
   */
  setAllowSingleClickNavigation(isEnabled: boolean) {
    this._allowSingleClick = isEnabled;
  }

  /**
   * Would this click (or other event type) hit the checkbox by default?
   */
  protected isWithinCheckboxHitArea(event: Event): boolean {
    let element: HTMLElement | null = event.target as HTMLElement;
    while (element) {
      if (element.classList.contains(CHECKBOX_WRAPPER_CLASS)) {
        return true;
      }
      element = element.parentElement;
    }
    return false;
  }

  /**
   * Handle the `'click'` event for the widget.
   */
  private _evtClick(event: MouseEvent) {
    const target = event.target as HTMLElement;

    const header = this.headerNode;
    const renderer = this._renderer;
    if (header.contains(target)) {
      const checkbox = renderer.getCheckboxNode(header);
      if (checkbox && this.isWithinCheckboxHitArea(event)) {
        const previouslyUnchecked =
          checkbox.dataset.indeterminate === 'false' &&
          checkbox.dataset.checked === 'false';
        // The only time a click on the check-all checkbox should check all is
        // when it was previously unchecked; otherwise, if the checkbox was
        // either checked (all selected) or indeterminate (some selected), the
        // click should clear all.
        if (previouslyUnchecked) {
          // Select all items
          this._sortedItems.forEach(
            (item: Contents.IModel) => (this.selection[item.path] = true)
          );
        } else {
          // Unselect all items
          this.clearSelectedItems();
        }
        this.update();
      } else {
        const state = this.renderer.handleHeaderClick(header, event);
        if (state) {
          this.sort(state);
        }
      }
      return;
    } else {
      // Focus the selected file on click to ensure a couple of things:
      // 1. If a user clicks on the item node, its name node will receive focus.
      // 2. If a user clicks on blank space in the directory listing, the
      //    previously focussed item will be focussed.
      this._focusItem(this._focusIndex);
    }

    if (this._allowSingleClick) {
      this.evtDblClick(event as MouseEvent);
    }
  }

  /**
   * Handle the `'scroll'` event for the widget.
   */
  private _evtScroll(event: MouseEvent): void {
    this.headerNode.scrollLeft = this.contentNode.scrollLeft;
  }

  /**
   * Handle the `'mousedown'` event for the widget.
   */
  private _evtMousedown(event: MouseEvent): void {
    // Bail if clicking within the edit node
    if (event.target === this._editNode) {
      return;
    }

    // Blur the edit node if necessary.
    if (this._editNode.parentNode) {
      if (this._editNode !== (event.target as HTMLElement)) {
        this._editNode.focus();
        this._editNode.blur();
        clearTimeout(this._selectTimer);
      } else {
        return;
      }
    }

    let index = Private.hitTestNodes(this._items, event);

    if (index === -1) {
      // Left mouse press for drag or resize start.
      if (event.button === 0) {
        const resizeHandle = event.target;
        if (
          resizeHandle instanceof HTMLElement &&
          resizeHandle.classList.contains(RESIZE_HANDLE_CLASS)
        ) {
          const columnId = resizeHandle.dataset.column as
            | DirListing.ResizableColumn
            | undefined;
          if (!columnId) {
            throw Error(
              'Column resize handle is missing data-column attribute'
            );
          }
          const column = DirListing.columns.find(c => c.id === columnId);
          if (!column) {
            throw Error(`Column with identifier ${columnId} not found`);
          }
          const element = DOMUtils.findElement(this.node, column.className);
          resizeHandle.classList.add(ACTIVE_CLASS);
          const cursorOverride = Drag.overrideCursor('col-resize');

          this._resizeData = {
            pressX: event.clientX,
            column: columnId,
            initialSize: element.getBoundingClientRect().width,
            overrides: new DisposableDelegate(() => {
              cursorOverride.dispose();
              resizeHandle.classList.remove(ACTIVE_CLASS);
            })
          };
          document.addEventListener('mouseup', this, true);
          document.addEventListener('mousemove', this, true);
          return;
        }
      }
      return;
    }

    this.handleFileSelect(event);

    if (event.button !== 0) {
      clearTimeout(this._selectTimer);
    }

    // Check for clearing a context menu.
    const newContext = (IS_MAC && event.ctrlKey) || event.button === 2;
    if (newContext) {
      return;
    }

    // Left mouse press for drag or resize start.
    if (event.button === 0) {
      this._dragData = {
        pressX: event.clientX,
        pressY: event.clientY,
        index: index
      };
      document.addEventListener('mouseup', this, true);
      document.addEventListener('mousemove', this, true);
    }
  }

  /**
   * Handle the `'mouseup'` event for the widget.
   */
  private _evtMouseup(event: MouseEvent): void {
    // Handle any soft selection from the previous mouse down.
    if (this._softSelection) {
      const altered = event.metaKey || event.shiftKey || event.ctrlKey;
      // See if we need to clear the other selection.
      if (!altered && event.button === 0) {
        this.clearSelectedItems();
        this.selection[this._softSelection] = true;
        this.update();
      }
      this._softSelection = '';
    }
    // Re-focus. This is needed because nodes corresponding to files selected in
    // mousedown handler will not retain the focus as mousedown event is always
    // followed by a blur/focus event.
    if (event.button === 0) {
      this._focusItem(this._focusIndex);
    }

    // Remove the resize listeners if necessary.
    if (this._resizeData) {
      this._resizeData.overrides.dispose();
      this._resizeData = null;
      document.removeEventListener('mousemove', this, true);
      document.removeEventListener('mouseup', this, true);
      return;
    }

    // Remove the drag listeners if necessary.
    if (event.button !== 0 || !this._drag) {
      document.removeEventListener('mousemove', this, true);
      document.removeEventListener('mouseup', this, true);
      return;
    }

    event.preventDefault();
    event.stopPropagation();
  }

  /**
   * Handle the `'mousemove'` event for the widget.
   */
  private _evtMousemove(event: MouseEvent): void {
    event.preventDefault();
    event.stopPropagation();

    if (this._resizeData) {
      const { initialSize, column, pressX } = this._resizeData;
      this._setColumnSize(column, initialSize + event.clientX - pressX);
      return;
    }

    // Bail if we are the one dragging.
    if (this._drag || !this._dragData) {
      return;
    }

    // Check for a drag initialization.
    const data = this._dragData;
    const dx = Math.abs(event.clientX - data.pressX);
    const dy = Math.abs(event.clientY - data.pressY);
    if (dx < DRAG_THRESHOLD && dy < DRAG_THRESHOLD) {
      return;
    }

    this._startDrag(data.index, event.clientX, event.clientY);
  }

  /**
   * Handle the opening of an item.
   */
  protected handleOpen(item: Contents.IModel): void {
    this._onItemOpened.emit(item);
    if (item.type === 'directory') {
      const localPath = this._manager.services.contents.localPath(item.path);
      this._model
        .cd(`/${localPath}`)
        .catch(error =>
          showErrorMessage(
            this._trans._p('showErrorMessage', 'Open directory'),
            error
          )
        );
    } else {
      const path = item.path;
      this._manager.openOrReveal(path);
    }
  }

  /**
   * Calculate the next focus index, given the current focus index and a
   * direction, keeping within the bounds of the directory listing.
   *
   * @param index Current focus index
   * @param direction -1 (up) or 1 (down)
   * @returns The next focus index, which could be the same as the current focus
   * index if at the boundary.
   */
  private _getNextFocusIndex(index: number, direction: number): number {
    const nextIndex = index + direction;
    if (nextIndex === -1 || nextIndex === this._items.length) {
      // keep focus index within bounds
      return index;
    } else {
      return nextIndex;
    }
  }

  /**
   * Handle the up or down arrow key.
   *
   * @param event The keyboard event
   * @param direction -1 (up) or 1 (down)
   */
  private _handleArrowY(event: KeyboardEvent, direction: number) {
    // We only handle the `ctrl` and `shift` modifiers. If other modifiers are
    // present, then do nothing.
    if (event.altKey || event.metaKey) {
      return;
    }

    // If folder is empty, there's nothing to do with the up/down key.
    if (!this._items.length) {
      return;
    }

    // Don't handle the arrow key press if it's not on directory item. This
    // avoids a confusing user experience that can result from when the user
    // moves the selection and focus index apart (via ctrl + up/down). The last
    // selected item remains highlighted but the last focussed item loses its
    // focus ring if it's not actively focussed.  This forces the user to
    // visibly reveal the last focussed item before moving the focus.
    if (!(event.target as HTMLElement).classList.contains(ITEM_TEXT_CLASS)) {
      return;
    }

    event.stopPropagation();
    event.preventDefault();

    const focusIndex = this._focusIndex;
    let nextFocusIndex = this._getNextFocusIndex(focusIndex, direction);

    // The following if-block allows the first press of the down arrow to select
    // the first (rather than the second) file/directory in the list. This is
    // the situation when the page first loads or when a user changes directory.
    if (
      direction > 0 &&
      focusIndex === 0 &&
      !event.ctrlKey &&
      Object.keys(this.selection).length === 0
    ) {
      nextFocusIndex = 0;
    }

    // Shift key indicates multi-selection. Either the user is trying to grow
    // the selection, or shrink it.
    if (event.shiftKey) {
      this._handleMultiSelect(nextFocusIndex);
    } else if (!event.ctrlKey) {
      // If neither the shift nor ctrl keys were used with the up/down arrow,
      // then we treat it as a normal, unmodified key press and select the
      // next item.
      this._selectItem(
        nextFocusIndex,
        event.shiftKey,
        false /* focus = false because we call focus method directly following this */
      );
    }

    this._focusItem(nextFocusIndex);
    this.update();
  }

  /**
   * cd ..
   *
   * Go up one level in the directory tree.
   */
  async goUp() {
    const model = this.model;
    if (model.path === model.rootPath) {
      return;
    }
    try {
      await model.cd('..');
    } catch (reason) {
      console.warn(`Failed to go to parent directory of ${model.path}`, reason);
    }
  }

  /**
   * Handle the `'keydown'` event for the widget.
   */
  protected evtKeydown(event: KeyboardEvent): void {
    // Do not handle any keydown events here if in the middle of a file rename.
    if (this._inRename) {
      return;
    }

    switch (event.keyCode) {
      case 13: {
        // Enter
        // Do nothing if any modifier keys are pressed.
        if (event.ctrlKey || event.shiftKey || event.altKey || event.metaKey) {
          return;
        }
        event.preventDefault();
        event.stopPropagation();
        for (const item of this.selectedItems()) {
          this.handleOpen(item);
        }
        return;
      }
      case 38: