# All files / lib/tree create.js

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     import Pool from '../util/pool';
    import {
      VTree,
      VTreeLike,
      ValidInput,
      EMPTY,
      NODE_TYPE,
      NodeCache,
      CreateTreeHookCache,
    } from '../util/types';

    const { isArray } = Array;
    const { memory } = Pool;
    const fragmentName = '#document-fragment';
    const textName = '#text';

    /**
     * Will flatten fragments that should remain invisible. If a fragment was
     * intentionally created to be diffed, such as a component, the rawNodeName
     * will not match and will be preserved.
     *
     * @param {VTree[]} vTrees
     * @param {VTree[]} retVal
     *
     * @return {VTree[]}
     */
    function flatten(vTrees, retVal = []) {
      for (let i = 0; i < vTrees.length; i++) {
        const vTree = vTrees[i];

        if (vTree && vTree.rawNodeName === fragmentName) {
          flatten(vTree.childNodes, retVal);
        }
        else if (vTree) {
          retVal.push(vTree);
        }
      }

      return retVal;
    }

    /**
     * Typically passed either a single or list of DOM Nodes or a VTreeLike object.
     *
     * @param {ValidInput=} input
     * @param {any=} attributes
     * @param {any=} childNodes
     * @param  {...any} rest
     *
     * @return {VTree}
     */
    export default function createTree(input, attributes, childNodes, ...rest) {
      /** @type {VTree | null} */
      let entry = null;

      // Reuse a VTree if it has already been created and in the pool. This is an
      // optimization and reliability check to ensure repeated calls to this
      // function with the same reference produces consistent results.
      if (memory.protected.has(input) || memory.allocated.has(input)) {
        entry = /** @type {VTree } */ (input);
      }

      // A fragment is used whenever an array is passed directly into createTree.
      // This is also what is returned when no input is passed.
      else if (!input || isArray(input)) {
        const length = input ? input.length : 0;

        childNodes = [];

        // When using an Array copy the Nodes in and ensure a valid top-level tree.
        for (let i = 0; i < length; i++) {
          const hasInput = input && !input[i];
          if (hasInput) continue;
          input && childNodes.push(input[i]);
        }

        entry = createTree(fragmentName, null, childNodes);
      }

      // If a return value was found, end this function early.
      if (entry) {
        return entry;
      }

      const isObject = typeof input === 'object';
      const inputAsHTMLEl = /** @type {HTMLElement} */ (input);

      // If the input passed has an 'ownerDocument' property, then assume it is a
      // DOM-like Node object. This means we need to synchronize the DOM and this is
      // an expensive operation.
      if (input && isObject && 'ownerDocument' in inputAsHTMLEl) {
        const { nodeType } = inputAsHTMLEl;

        // When passed a text node, simply migrate the value over into the new VTree
        // associate in the NodeCache.
        if (nodeType === NODE_TYPE.TEXT) {
          const vTree = createTree(textName, inputAsHTMLEl.nodeValue);
          NodeCache.set(vTree, inputAsHTMLEl);
          return vTree;
        }

        attributes = {};
        childNodes = [];

        const inputAttrs = inputAsHTMLEl.attributes;

        // We only scrape attributes from element nodes if they are available.
        if (inputAsHTMLEl.nodeType === NODE_TYPE.ELEMENT && inputAttrs && inputAttrs.length) {
          for (let i = 0; i < inputAttrs.length; i++) {
            const { name, value } = inputAttrs[i];

            // If the attribute's value is empty, seek out the property instead.
            if (value === EMPTY.STR && name in inputAsHTMLEl) {
              attributes[name] = /** @type {any} */ (input)[name];
              continue;
            }

            attributes[name] = value;
          }
        }

        // Get the child nodes from an Element or Fragment/Shadow Root.
        if (inputAsHTMLEl.nodeType === NODE_TYPE.ELEMENT || inputAsHTMLEl.nodeType === NODE_TYPE.FRAGMENT) {
          childNodes = [];

          for (let i = 0; i < inputAsHTMLEl.childNodes.length; i++) {
            /** @type {ValidInput} */
            const childNodeElement = (inputAsHTMLEl.childNodes[i]);
            childNodes.push(createTree(childNodeElement));
          }
        }

        // FIXME This is going to hurt performance. Is there a better way to find a
        // VTree from a DOM Node?
        NodeCache.forEach((domNode, vTree) => {
          if (domNode === input) {
            entry = vTree;
          }
        });

        /**
         * If no VTree was previously bound this to DOM Node, create a brand new
         * tree.
         *
         * @type {VTree} */
        entry = entry || createTree(
          inputAsHTMLEl.nodeName,
          attributes,
          childNodes,
        );

        entry.attributes = { ...entry.attributes, ...attributes };

        // Use childNodes that are passed in, otherwise keep the existing nodes.
        entry.childNodes = childNodes;

        NodeCache.set(entry, inputAsHTMLEl);
        return entry;
      }

      // Assume any remaining objects are VTree-like.
      if (isObject) {
        /** @type {VTreeLike} */
        const {
          rawNodeName,
          nodeName,
          nodeValue,
          attributes,
          childNodes,
          children,
        } = (/** @type {any} */(input));

        const treeName = rawNodeName || nodeName;

        // The priority of a VTreeLike input is nodeValue above all else. If this
        // value is present, we assume a text-based element and that the intentions
        // are setting the children to this value.
        const vTree = createTree(
          treeName,
          attributes || null,
          children || childNodes,
        );

        // Ensure nodeValue is properly copied over.
        if (nodeValue) {
          vTree.nodeValue = nodeValue;
        }

        return vTree;
      }

      // Support JSX-style children being passed.
      if (rest.length) {
        childNodes = [childNodes, ...rest];
      }

      // Allocate a new VTree from the pool.
      entry = Pool.get();

      const isTextNode = input === textName;
      const isString = typeof input === 'string';

      // This is a standard HTML element.
      if (isString) {
        entry.rawNodeName = input;
        entry.nodeName = entry.rawNodeName.toLowerCase();
      }
      // Otherwise treat this as a fragment, since we have no idea what type of
      // element it is.
      else {
        entry.rawNodeName = input;
        entry.nodeName = fragmentName;
      }

      // Clear out and reset the remaining VTree attributes.
      entry.nodeValue = EMPTY.STR;
      entry.key = EMPTY.STR;
      entry.childNodes.length = 0;
      entry.attributes = {};

      const useAttributes = isArray(attributes) || typeof attributes !== 'object';
      const useNodes = useAttributes ? attributes : childNodes;
      const allNodes = flatten(isArray(useNodes) ? useNodes : [useNodes]);

      // Ensure nodeType is set correctly, and if this is a text node, return early.
      if (isTextNode) {
        const nodeValue = allNodes.join(EMPTY.STR);

        entry.nodeType = NODE_TYPE.TEXT;
        entry.nodeValue = String(nodeValue);

        return entry;
      }
      else if (entry.nodeName === fragmentName) {
        entry.nodeType = NODE_TYPE.FRAGMENT;
      }
      else if (input === '#comment') {
        entry.nodeType = NODE_TYPE.COMMENT;
      }
      else {
        entry.nodeType = NODE_TYPE.ELEMENT;
      }

      // Parse out the child nodes if they exist and are not overwritten by an
      // attribute.
      if (useNodes && allNodes.length && (!attributes || !attributes.childNodes)) {
        for (let i = 0; i < allNodes.length; i++) {
          const newNode = allNodes[i];

          // Merge in arrays.
          if (isArray(newNode)) {
            entry.childNodes.push(...newNode);
          }
          // Skip over `null` nodes.
          else if (!newNode) {
            continue;
          }
          // Merge in true fragments, but not components or unknowns.
          else if (newNode.nodeType === NODE_TYPE.FRAGMENT && typeof newNode.rawNodeName === 'string') {
            entry.childNodes.push(...newNode.childNodes);
          }
          // Assume objects are vTrees.
          else if (newNode && typeof newNode === 'object') {
            entry.childNodes.push(createTree(newNode));
          }
          // Last resort treat as text.
          else {
            entry.childNodes.push(createTree(textName, null, newNode));
          }
        }
      }

      if (attributes && typeof attributes === 'object' && !isArray(attributes)) {
        entry.attributes = { ...attributes };

        // Use childNodes directly from the attributes.
        if (attributes.childNodes) {
          const isObject = typeof attributes.childNodes === 'object';
          entry.childNodes.push(isObject ? createTree(attributes.childNodes) : createTree('#text', attributes.childNodes));
        }
      }

      // If is a script tag and has a src attribute, key off that. We have a special
      // handling of scripts to avoid accidentally re-executing a script when
      // shifting position.
      if (entry.nodeName === 'script' && entry.attributes.src) {
        entry.key = String(entry.attributes.src);
      }

      // Set the `key` prop if passed as an attr, overrides `script[src]`.
      if (entry.attributes && 'key' in entry.attributes) {
        entry.key = String(entry.attributes.key);
      }

      // Only run the `forEach` if there are hooks to run.
      if (CreateTreeHookCache.size) {
        CreateTreeHookCache.forEach((fn, retVal) => {
          // If the hook returns a value, replace the active entry.
          if (retVal = fn(entry)) {
            entry = createTree(retVal);
          }
        });
      }

      return entry;
    }