text: "use strict";
  
  const idlUtils = require("../generated/utils");
  const NodeList = require("../generated/NodeList");
  const HTMLCollection = require("../generated/HTMLCollection");
  const { addNwsapi } = require("../helpers/selectors");
  const { domSymbolTree } = require("../helpers/internal-constants");
  const NODE_TYPE = require("../node-type");
  const { convertNodesIntoNode } = require("../node");
  
  class ParentNodeImpl {
    get children() {
      if (!this._childrenList) {
        this._childrenList = HTMLCollection.createImpl([], {
          element: this,
          query: () => domSymbolTree.childrenToArray(this, {
            filter: node => node.nodeType === NODE_TYPE.ELEMENT_NODE
          })
        });
      } else {
        this._childrenList._update();
      }
      return this._childrenList;
    }
  
    get firstElementChild() {
      for (const child of domSymbolTree.childrenIterator(this)) {
        if (child.nodeType === NODE_TYPE.ELEMENT_NODE) {
          return child;
        }
      }
  
      return null;
    }
  
    get lastElementChild() {
      for (const child of domSymbolTree.childrenIterator(this, { reverse: true })) {
        if (child.nodeType === NODE_TYPE.ELEMENT_NODE) {
          return child;
        }
      }
  
      return null;
    }
  
    get childElementCount() {
      return this.children.length;
    }
  
    append(...nodes) {
      this.appendChild(convertNodesIntoNode(this._ownerDocument, nodes));
    }
  
    prepend(...nodes) {
      this.insertBefore(convertNodesIntoNode(this._ownerDocument, nodes), this.firstChild);
    }
  }
  
  ParentNodeImpl.prototype.querySelector = function (selectors) {
    if (shouldAlwaysSelectNothing(this)) {
      return null;
    }
    const matcher = addNwsapi(this);
    return idlUtils.implForWrapper(matcher.first(selectors, idlUtils.wrapperForImpl(this)));
  };
  
  // WARNING: this returns a NodeList containing IDL wrappers instead of impls
  ParentNodeImpl.prototype.querySelectorAll = function (selectors) {
    if (shouldAlwaysSelectNothing(this)) {
      return NodeList.create([], { nodes: [] });
    }
    const matcher = addNwsapi(this);
    const list = matcher.select(selectors, idlUtils.wrapperForImpl(this));
  
    return NodeList.create([], { nodes: list.map(n => idlUtils.tryImplForWrapper(n)) });
  };
  
  function shouldAlwaysSelectNothing(elImpl) {
    // This is true during initialization.
    return elImpl === elImpl._ownerDocument && !elImpl.documentElement;
  }
  
  module.exports = {
    implementation: ParentNodeImpl
  };
  