Anjing Webshells

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Filename : inert.js
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/**
 * This work is licensed under the W3C Software and Document License
 * (http://www.w3.org/Consortium/Legal/2015/copyright-software-and-document).
 */

// Convenience function for converting NodeLists.
/** @type {typeof Array.prototype.slice} */
const slice = Array.prototype.slice;

/**
 * IE has a non-standard name for "matches".
 * @type {typeof Element.prototype.matches}
 */
const matches =
    Element.prototype.matches || Element.prototype.msMatchesSelector;

/** @type {string} */
const _focusableElementsString = ['a[href]',
                                  'area[href]',
                                  'input:not([disabled])',
                                  'select:not([disabled])',
                                  'textarea:not([disabled])',
                                  'button:not([disabled])',
                                  'iframe',
                                  'object',
                                  'embed',
                                  '[contenteditable]'].join(',');

/**
 * `InertRoot` manages a single inert subtree, i.e. a DOM subtree whose root element has an `inert`
 * attribute.
 *
 * Its main functions are:
 *
 * - to create and maintain a set of managed `InertNode`s, including when mutations occur in the
 *   subtree. The `makeSubtreeUnfocusable()` method handles collecting `InertNode`s via registering
 *   each focusable node in the subtree with the singleton `InertManager` which manages all known
 *   focusable nodes within inert subtrees. `InertManager` ensures that a single `InertNode`
 *   instance exists for each focusable node which has at least one inert root as an ancestor.
 *
 * - to notify all managed `InertNode`s when this subtree stops being inert (i.e. when the `inert`
 *   attribute is removed from the root node). This is handled in the destructor, which calls the
 *   `deregister` method on `InertManager` for each managed inert node.
 */
class InertRoot {
  /**
   * @param {!Element} rootElement The Element at the root of the inert subtree.
   * @param {!InertManager} inertManager The global singleton InertManager object.
   */
  constructor(rootElement, inertManager) {
    /** @type {!InertManager} */
    this._inertManager = inertManager;

    /** @type {!Element} */
    this._rootElement = rootElement;

    /**
     * @type {!Set<!InertNode>}
     * All managed focusable nodes in this InertRoot's subtree.
     */
    this._managedNodes = new Set();

    // Make the subtree hidden from assistive technology
    if (this._rootElement.hasAttribute('aria-hidden')) {
      /** @type {?string} */
      this._savedAriaHidden = this._rootElement.getAttribute('aria-hidden');
    } else {
      this._savedAriaHidden = null;
    }
    this._rootElement.setAttribute('aria-hidden', 'true');

    // Make all focusable elements in the subtree unfocusable and add them to _managedNodes
    this._makeSubtreeUnfocusable(this._rootElement);

    // Watch for:
    // - any additions in the subtree: make them unfocusable too
    // - any removals from the subtree: remove them from this inert root's managed nodes
    // - attribute changes: if `tabindex` is added, or removed from an intrinsically focusable
    //   element, make that node a managed node.
    this._observer = new MutationObserver(this._onMutation.bind(this));
    this._observer.observe(this._rootElement, {attributes: true, childList: true, subtree: true});
  }

  /**
   * Call this whenever this object is about to become obsolete.  This unwinds all of the state
   * stored in this object and updates the state of all of the managed nodes.
   */
  destructor() {
    this._observer.disconnect();

    if (this._rootElement) {
      if (this._savedAriaHidden !== null) {
        this._rootElement.setAttribute('aria-hidden', this._savedAriaHidden);
      } else {
        this._rootElement.removeAttribute('aria-hidden');
      }
    }

    this._managedNodes.forEach(function(inertNode) {
      this._unmanageNode(inertNode.node);
    }, this);

    // Note we cast the nulls to the ANY type here because:
    // 1) We want the class properties to be declared as non-null, or else we
    //    need even more casts throughout this code. All bets are off if an
    //    instance has been destroyed and a method is called.
    // 2) We don't want to cast "this", because we want type-aware optimizations
    //    to know which properties we're setting.
    this._observer = /** @type {?} */ (null);
    this._rootElement = /** @type {?} */ (null);
    this._managedNodes = /** @type {?} */ (null);
    this._inertManager = /** @type {?} */ (null);
  }

  /**
   * @return {!Set<!InertNode>} A copy of this InertRoot's managed nodes set.
   */
  get managedNodes() {
    return new Set(this._managedNodes);
  }

  /** @return {boolean} */
  get hasSavedAriaHidden() {
    return this._savedAriaHidden !== null;
  }

  /** @param {?string} ariaHidden */
  set savedAriaHidden(ariaHidden) {
    this._savedAriaHidden = ariaHidden;
  }

  /** @return {?string} */
  get savedAriaHidden() {
    return this._savedAriaHidden;
  }

  /**
   * @param {!Node} startNode
   */
  _makeSubtreeUnfocusable(startNode) {
    composedTreeWalk(startNode, (node) => this._visitNode(node));

    let activeElement = document.activeElement;

    if (!document.body.contains(startNode)) {
      // startNode may be in shadow DOM, so find its nearest shadowRoot to get the activeElement.
      let node = startNode;
      /** @type {!ShadowRoot|undefined} */
      let root = undefined;
      while (node) {
        if (node.nodeType === Node.DOCUMENT_FRAGMENT_NODE) {
          root = /** @type {!ShadowRoot} */ (node);
          break;
        }
        node = node.parentNode;
      }
      if (root) {
        activeElement = root.activeElement;
      }
    }
    if (startNode.contains(activeElement)) {
      activeElement.blur();
      // In IE11, if an element is already focused, and then set to tabindex=-1
      // calling blur() will not actually move the focus.
      // To work around this we call focus() on the body instead.
      if (activeElement === document.activeElement) {
        document.body.focus();
      }
    }
  }

  /**
   * @param {!Node} node
   */
  _visitNode(node) {
    if (node.nodeType !== Node.ELEMENT_NODE) {
      return;
    }
    const element = /** @type {!Element} */ (node);

    // If a descendant inert root becomes un-inert, its descendants will still be inert because of
    // this inert root, so all of its managed nodes need to be adopted by this InertRoot.
    if (element !== this._rootElement && element.hasAttribute('inert')) {
      this._adoptInertRoot(element);
    }

    if (matches.call(element, _focusableElementsString) || element.hasAttribute('tabindex')) {
      this._manageNode(element);
    }
  }

  /**
   * Register the given node with this InertRoot and with InertManager.
   * @param {!Node} node
   */
  _manageNode(node) {
    const inertNode = this._inertManager.register(node, this);
    this._managedNodes.add(inertNode);
  }

  /**
   * Unregister the given node with this InertRoot and with InertManager.
   * @param {!Node} node
   */
  _unmanageNode(node) {
    const inertNode = this._inertManager.deregister(node, this);
    if (inertNode) {
      this._managedNodes.delete(inertNode);
    }
  }

  /**
   * Unregister the entire subtree starting at `startNode`.
   * @param {!Node} startNode
   */
  _unmanageSubtree(startNode) {
    composedTreeWalk(startNode, (node) => this._unmanageNode(node));
  }

  /**
   * If a descendant node is found with an `inert` attribute, adopt its managed nodes.
   * @param {!Element} node
   */
  _adoptInertRoot(node) {
    let inertSubroot = this._inertManager.getInertRoot(node);

    // During initialisation this inert root may not have been registered yet,
    // so register it now if need be.
    if (!inertSubroot) {
      this._inertManager.setInert(node, true);
      inertSubroot = this._inertManager.getInertRoot(node);
    }

    inertSubroot.managedNodes.forEach(function(savedInertNode) {
      this._manageNode(savedInertNode.node);
    }, this);
  }

  /**
   * Callback used when mutation observer detects subtree additions, removals, or attribute changes.
   * @param {!Array<!MutationRecord>} records
   * @param {!MutationObserver} self
   */
  _onMutation(records, self) {
    records.forEach(function(record) {
      const target = /** @type {!Element} */ (record.target);
      if (record.type === 'childList') {
        // Manage added nodes
        slice.call(record.addedNodes).forEach(function(node) {
          this._makeSubtreeUnfocusable(node);
        }, this);

        // Un-manage removed nodes
        slice.call(record.removedNodes).forEach(function(node) {
          this._unmanageSubtree(node);
        }, this);
      } else if (record.type === 'attributes') {
        if (record.attributeName === 'tabindex') {
          // Re-initialise inert node if tabindex changes
          this._manageNode(target);
        } else if (target !== this._rootElement &&
                   record.attributeName === 'inert' &&
                   target.hasAttribute('inert')) {
          // If a new inert root is added, adopt its managed nodes and make sure it knows about the
          // already managed nodes from this inert subroot.
          this._adoptInertRoot(target);
          const inertSubroot = this._inertManager.getInertRoot(target);
          this._managedNodes.forEach(function(managedNode) {
            if (target.contains(managedNode.node)) {
              inertSubroot._manageNode(managedNode.node);
            }
          });
        }
      }
    }, this);
  }
}

/**
 * `InertNode` initialises and manages a single inert node.
 * A node is inert if it is a descendant of one or more inert root elements.
 *
 * On construction, `InertNode` saves the existing `tabindex` value for the node, if any, and
 * either removes the `tabindex` attribute or sets it to `-1`, depending on whether the element
 * is intrinsically focusable or not.
 *
 * `InertNode` maintains a set of `InertRoot`s which are descendants of this `InertNode`. When an
 * `InertRoot` is destroyed, and calls `InertManager.deregister()`, the `InertManager` notifies the
 * `InertNode` via `removeInertRoot()`, which in turn destroys the `InertNode` if no `InertRoot`s
 * remain in the set. On destruction, `InertNode` reinstates the stored `tabindex` if one exists,
 * or removes the `tabindex` attribute if the element is intrinsically focusable.
 */
class InertNode {
  /**
   * @param {!Node} node A focusable element to be made inert.
   * @param {!InertRoot} inertRoot The inert root element associated with this inert node.
   */
  constructor(node, inertRoot) {
    /** @type {!Node} */
    this._node = node;

    /** @type {boolean} */
    this._overrodeFocusMethod = false;

    /**
     * @type {!Set<!InertRoot>} The set of descendant inert roots.
     *    If and only if this set becomes empty, this node is no longer inert.
     */
    this._inertRoots = new Set([inertRoot]);

    /** @type {?number} */
    this._savedTabIndex = null;

    /** @type {boolean} */
    this._destroyed = false;

    // Save any prior tabindex info and make this node untabbable
    this.ensureUntabbable();
  }

  /**
   * Call this whenever this object is about to become obsolete.
   * This makes the managed node focusable again and deletes all of the previously stored state.
   */
  destructor() {
    this._throwIfDestroyed();

    if (this._node && this._node.nodeType === Node.ELEMENT_NODE) {
      const element = /** @type {!Element} */ (this._node);
      if (this._savedTabIndex !== null) {
        element.setAttribute('tabindex', this._savedTabIndex);
      } else {
        element.removeAttribute('tabindex');
      }

      // Use `delete` to restore native focus method.
      if (this._overrodeFocusMethod) {
        delete element.focus;
      }
    }

    // See note in InertRoot.destructor for why we cast these nulls to ANY.
    this._node = /** @type {?} */ (null);
    this._inertRoots = /** @type {?} */ (null);
    this._destroyed = true;
  }

  /**
   * @type {boolean} Whether this object is obsolete because the managed node is no longer inert.
   * If the object has been destroyed, any attempt to access it will cause an exception.
   */
  get destroyed() {
    return /** @type {!InertNode} */ (this)._destroyed;
  }

  /**
   * Throw if user tries to access destroyed InertNode.
   */
  _throwIfDestroyed() {
    if (this.destroyed) {
      throw new Error('Trying to access destroyed InertNode');
    }
  }

  /** @return {boolean} */
  get hasSavedTabIndex() {
    return this._savedTabIndex !== null;
  }

  /** @return {!Node} */
  get node() {
    this._throwIfDestroyed();
    return this._node;
  }

  /** @param {?number} tabIndex */
  set savedTabIndex(tabIndex) {
    this._throwIfDestroyed();
    this._savedTabIndex = tabIndex;
  }

  /** @return {?number} */
  get savedTabIndex() {
    this._throwIfDestroyed();
    return this._savedTabIndex;
  }

  /** Save the existing tabindex value and make the node untabbable and unfocusable */
  ensureUntabbable() {
    if (this.node.nodeType !== Node.ELEMENT_NODE) {
      return;
    }
    const element = /** @type {!Element} */ (this.node);
    if (matches.call(element, _focusableElementsString)) {
      if (/** @type {!HTMLElement} */ (element).tabIndex === -1 &&
          this.hasSavedTabIndex) {
        return;
      }

      if (element.hasAttribute('tabindex')) {
        this._savedTabIndex = /** @type {!HTMLElement} */ (element).tabIndex;
      }
      element.setAttribute('tabindex', '-1');
      if (element.nodeType === Node.ELEMENT_NODE) {
        element.focus = function() {};
        this._overrodeFocusMethod = true;
      }
    } else if (element.hasAttribute('tabindex')) {
      this._savedTabIndex = /** @type {!HTMLElement} */ (element).tabIndex;
      element.removeAttribute('tabindex');
    }
  }

  /**
   * Add another inert root to this inert node's set of managing inert roots.
   * @param {!InertRoot} inertRoot
   */
  addInertRoot(inertRoot) {
    this._throwIfDestroyed();
    this._inertRoots.add(inertRoot);
  }

  /**
   * Remove the given inert root from this inert node's set of managing inert roots.
   * If the set of managing inert roots becomes empty, this node is no longer inert,
   * so the object should be destroyed.
   * @param {!InertRoot} inertRoot
   */
  removeInertRoot(inertRoot) {
    this._throwIfDestroyed();
    this._inertRoots.delete(inertRoot);
    if (this._inertRoots.size === 0) {
      this.destructor();
    }
  }
}

/**
 * InertManager is a per-document singleton object which manages all inert roots and nodes.
 *
 * When an element becomes an inert root by having an `inert` attribute set and/or its `inert`
 * property set to `true`, the `setInert` method creates an `InertRoot` object for the element.
 * The `InertRoot` in turn registers itself as managing all of the element's focusable descendant
 * nodes via the `register()` method. The `InertManager` ensures that a single `InertNode` instance
 * is created for each such node, via the `_managedNodes` map.
 */
class InertManager {
  /**
   * @param {!Document} document
   */
  constructor(document) {
    if (!document) {
      throw new Error('Missing required argument; InertManager needs to wrap a document.');
    }

    /** @type {!Document} */
    this._document = document;

    /**
     * All managed nodes known to this InertManager. In a map to allow looking up by Node.
     * @type {!Map<!Node, !InertNode>}
     */
    this._managedNodes = new Map();

    /**
     * All inert roots known to this InertManager. In a map to allow looking up by Node.
     * @type {!Map<!Node, !InertRoot>}
     */
    this._inertRoots = new Map();

    /**
     * Observer for mutations on `document.body`.
     * @type {!MutationObserver}
     */
    this._observer = new MutationObserver(this._watchForInert.bind(this));

    // Add inert style.
    addInertStyle(document.head || document.body || document.documentElement);

    // Wait for document to be loaded.
    if (document.readyState === 'loading') {
      document.addEventListener('DOMContentLoaded', this._onDocumentLoaded.bind(this));
    } else {
      this._onDocumentLoaded();
    }
  }

  /**
   * Set whether the given element should be an inert root or not.
   * @param {!Element} root
   * @param {boolean} inert
   */
  setInert(root, inert) {
    if (inert) {
      if (this._inertRoots.has(root)) { // element is already inert
        return;
      }

      const inertRoot = new InertRoot(root, this);
      root.setAttribute('inert', '');
      this._inertRoots.set(root, inertRoot);
      // If not contained in the document, it must be in a shadowRoot.
      // Ensure inert styles are added there.
      if (!this._document.body.contains(root)) {
        let parent = root.parentNode;
        while (parent) {
          if (parent.nodeType === 11) {
            addInertStyle(parent);
          }
          parent = parent.parentNode;
        }
      }
    } else {
      if (!this._inertRoots.has(root)) { // element is already non-inert
        return;
      }

      const inertRoot = this._inertRoots.get(root);
      inertRoot.destructor();
      this._inertRoots.delete(root);
      root.removeAttribute('inert');
    }
  }

  /**
   * Get the InertRoot object corresponding to the given inert root element, if any.
   * @param {!Node} element
   * @return {!InertRoot|undefined}
   */
  getInertRoot(element) {
    return this._inertRoots.get(element);
  }

  /**
   * Register the given InertRoot as managing the given node.
   * In the case where the node has a previously existing inert root, this inert root will
   * be added to its set of inert roots.
   * @param {!Node} node
   * @param {!InertRoot} inertRoot
   * @return {!InertNode} inertNode
   */
  register(node, inertRoot) {
    let inertNode = this._managedNodes.get(node);
    if (inertNode !== undefined) { // node was already in an inert subtree
      inertNode.addInertRoot(inertRoot);
    } else {
      inertNode = new InertNode(node, inertRoot);
    }

    this._managedNodes.set(node, inertNode);

    return inertNode;
  }

  /**
   * De-register the given InertRoot as managing the given inert node.
   * Removes the inert root from the InertNode's set of managing inert roots, and remove the inert
   * node from the InertManager's set of managed nodes if it is destroyed.
   * If the node is not currently managed, this is essentially a no-op.
   * @param {!Node} node
   * @param {!InertRoot} inertRoot
   * @return {?InertNode} The potentially destroyed InertNode associated with this node, if any.
   */
  deregister(node, inertRoot) {
    const inertNode = this._managedNodes.get(node);
    if (!inertNode) {
      return null;
    }

    inertNode.removeInertRoot(inertRoot);
    if (inertNode.destroyed) {
      this._managedNodes.delete(node);
    }

    return inertNode;
  }

  /**
   * Callback used when document has finished loading.
   */
  _onDocumentLoaded() {
    // Find all inert roots in document and make them actually inert.
    const inertElements = slice.call(this._document.querySelectorAll('[inert]'));
    inertElements.forEach(function(inertElement) {
      this.setInert(inertElement, true);
    }, this);

    // Comment this out to use programmatic API only.
    this._observer.observe(this._document.body, {attributes: true, subtree: true, childList: true});
  }

  /**
   * Callback used when mutation observer detects attribute changes.
   * @param {!Array<!MutationRecord>} records
   * @param {!MutationObserver} self
   */
  _watchForInert(records, self) {
    const _this = this;
    records.forEach(function(record) {
      switch (record.type) {
      case 'childList':
        slice.call(record.addedNodes).forEach(function(node) {
          if (node.nodeType !== Node.ELEMENT_NODE) {
            return;
          }
          const inertElements = slice.call(node.querySelectorAll('[inert]'));
          if (matches.call(node, '[inert]')) {
            inertElements.unshift(node);
          }
          inertElements.forEach(function(inertElement) {
            this.setInert(inertElement, true);
          }, _this);
        }, _this);
        break;
      case 'attributes':
        if (record.attributeName !== 'inert') {
          return;
        }
        const target = /** @type {!Element} */ (record.target);
        const inert = target.hasAttribute('inert');
        _this.setInert(target, inert);
        break;
      }
    }, this);
  }
}

/**
 * Recursively walk the composed tree from |node|.
 * @param {!Node} node
 * @param {(function (!Element))=} callback Callback to be called for each element traversed,
 *     before descending into child nodes.
 * @param {?ShadowRoot=} shadowRootAncestor The nearest ShadowRoot ancestor, if any.
 */
function composedTreeWalk(node, callback, shadowRootAncestor) {
  if (node.nodeType == Node.ELEMENT_NODE) {
    const element = /** @type {!Element} */ (node);
    if (callback) {
      callback(element);
    }

    // Descend into node:
    // If it has a ShadowRoot, ignore all child elements - these will be picked
    // up by the <content> or <shadow> elements. Descend straight into the
    // ShadowRoot.
    const shadowRoot = /** @type {!HTMLElement} */ (element).shadowRoot;
    if (shadowRoot) {
      composedTreeWalk(shadowRoot, callback, shadowRoot);
      return;
    }

    // If it is a <content> element, descend into distributed elements - these
    // are elements from outside the shadow root which are rendered inside the
    // shadow DOM.
    if (element.localName == 'content') {
      const content = /** @type {!HTMLContentElement} */ (element);
      // Verifies if ShadowDom v0 is supported.
      const distributedNodes = content.getDistributedNodes ?
        content.getDistributedNodes() : [];
      for (let i = 0; i < distributedNodes.length; i++) {
        composedTreeWalk(distributedNodes[i], callback, shadowRootAncestor);
      }
      return;
    }

    // If it is a <slot> element, descend into assigned nodes - these
    // are elements from outside the shadow root which are rendered inside the
    // shadow DOM.
    if (element.localName == 'slot') {
      const slot = /** @type {!HTMLSlotElement} */ (element);
      // Verify if ShadowDom v1 is supported.
      const distributedNodes = slot.assignedNodes ?
        slot.assignedNodes({flatten: true}) : [];
      for (let i = 0; i < distributedNodes.length; i++) {
        composedTreeWalk(distributedNodes[i], callback, shadowRootAncestor);
      }
      return;
    }
  }

  // If it is neither the parent of a ShadowRoot, a <content> element, a <slot>
  // element, nor a <shadow> element recurse normally.
  let child = node.firstChild;
  while (child != null) {
    composedTreeWalk(child, callback, shadowRootAncestor);
    child = child.nextSibling;
  }
}

/**
 * Adds a style element to the node containing the inert specific styles
 * @param {!Node} node
 */
function addInertStyle(node) {
  if (node.querySelector('style#inert-style')) {
    return;
  }
  const style = document.createElement('style');
  style.setAttribute('id', 'inert-style');
  style.textContent = '\n'+
                      '[inert] {\n' +
                      '  pointer-events: none;\n' +
                      '  cursor: default;\n' +
                      '}\n' +
                      '\n' +
                      '[inert], [inert] * {\n' +
                      '  user-select: none;\n' +
                      '  -webkit-user-select: none;\n' +
                      '  -moz-user-select: none;\n' +
                      '  -ms-user-select: none;\n' +
                      '}\n';
  node.appendChild(style);
}

/** @type {!InertManager} */
const inertManager = new InertManager(document);

if (!Element.prototype.hasOwnProperty('inert')) {
  Object.defineProperty(Element.prototype, 'inert', {
    enumerable: true,
    /** @this {!Element} */
    get: function() {
      return this.hasAttribute('inert');
    },
    /** @this {!Element} */
    set: function(inert) {
      inertManager.setInert(this, inert);
    },
  });
}