Class ElementNode

packages/react-aria/src/collections/Document.ts:262–422

 * Collection Node which is copied on write.
 */
export class ElementNode<T> extends BaseNode<T> {
  nodeType = 8; // COMMENT_NODE (we'd use ELEMENT_NODE but React DevTools will fail to get its dimensions)
  node: CollectionNode<T> | null;
  isMutated = true;
  private _index: number = 0;
  isHidden = false;

  constructor(type: string, ownerDocument: Document<T, any>) {
    super(ownerDocument);
    this.node = null;
  }

  get index(): number {
    return this._index;
  }

  set index(index: number) {
    this._index = index;
    this.ownerDocument.markDirty(this);
  }

  get level(): number {
    if (this.parentNode instanceof ElementNode) {
      return this.parentNode.level + (this.parentNode.node?.type === 'item' ? 1 : 0);
    }

    return 0;
  }

  /**
   * Lazily gets a mutable instance of a Node. If the node has already
   * been cloned during this update cycle, it just returns the existing one.
   */
  private getMutableNode(): Mutable<CollectionNode<T>> | null {
    if (this.node == null) {
      return null;
    }

    if (!this.isMutated) {
      this.node = this.node.clone();
      this.isMutated = true;
    }

    this.ownerDocument.markDirty(this);
    return this.node;
  }

  updateNode(): void {
    let nextSibling = this.nextVisibleSibling;
    let node = this.getMutableNode();
    if (node == null) {
      return;
    }

    node.index = this.index;
    node.level = this.level;
    node.parentKey =
      this.parentNode instanceof ElementNode ? (this.parentNode.node?.key ?? null) : null;