template-stamp.html

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<link rel="import" href="../utils/boot.html">
<link rel="import" href="../utils/mixin.html">

<script>
(function() {

  'use strict';

  // 1.x backwards-compatible auto-wrapper for template type extensions
  // This is a clear layering violation and gives favored-nation status to
  // dom-if and dom-repeat templates.  This is a conceit we're choosing to keep
  // a.) to ease 1.x backwards-compatibility due to loss of `is`, and
  // b.) to maintain if/repeat capability in parser-constrained elements
  //     (e.g. table, select) in lieu of native CE type extensions without
  //     massive new invention in this space (e.g. directive system)
  const templateExtensions = {
    'dom-if': true,
    'dom-repeat': true
  };
  function wrapTemplateExtension(node) {
    let is = node.getAttribute('is');
    if (is && templateExtensions[is]) {
      let t = node;
      t.removeAttribute('is');
      node = t.ownerDocument.createElement(is);
      t.parentNode.replaceChild(node, t);
      node.appendChild(t);
      while(t.attributes.length) {
        node.setAttribute(t.attributes[0].name, t.attributes[0].value);
        t.removeAttribute(t.attributes[0].name);
      }
    }
    return node;
  }

  function findTemplateNode(root, nodeInfo) {
    // recursively ascend tree until we hit root
    let parent = nodeInfo.parentInfo && findTemplateNode(root, nodeInfo.parentInfo);
    // unwind the stack, returning the indexed node at each level
    if (parent) {
      // note: marginally faster than indexing via childNodes
      // (http://jsperf.com/childnodes-lookup)
      for (let n=parent.firstChild, i=0; n; n=n.nextSibling) {
        if (nodeInfo.parentIndex === i++) {
          return n;
        }
      }
    } else {
      return root;
    }
  }

  // construct `$` map (from id annotations)
  function applyIdToMap(inst, map, node, nodeInfo) {
    if (nodeInfo.id) {
      map[nodeInfo.id] = node;
    }
  }

  // install event listeners (from event annotations)
  function applyEventListener(inst, node, nodeInfo) {
    if (nodeInfo.events && nodeInfo.events.length) {
      for (let j=0, e$=nodeInfo.events, e; (j<e$.length) && (e=e$[j]); j++) {
        inst._addMethodEventListenerToNode(node, e.name, e.value, inst);
      }
    }
  }

  // push configuration references at configure time
  function applyTemplateContent(inst, node, nodeInfo) {
    if (nodeInfo.templateInfo) {
      node._templateInfo = nodeInfo.templateInfo;
    }
  }

  function createNodeEventHandler(context, eventName, methodName) {
    // Instances can optionally have a _methodHost which allows redirecting where
    // to find methods. Currently used by `templatize`.
    context = context._methodHost || context;
    let handler = function(e) {
      if (context[methodName]) {
        context[methodName](e, e.detail);
      } else {
        console.warn('listener method `' + methodName + '` not defined');
      }
    };
    return handler;
  }

  /**
   * Element mixin that provides basic template parsing and stamping, including
   * the following template-related features for stamped templates:
   *
   * - Declarative event listeners (`on-eventname="listener"`)
   * - Map of node id's to stamped node instances (`this.$.id`)
   * - Nested template content caching/removal and re-installation (performance
   *   optimization)
   *
   * @mixinFunction
   * @polymer
   * @memberof Polymer
   * @summary Element class mixin that provides basic template parsing and stamping
   */
  Polymer.TemplateStamp = Polymer.dedupingMixin(superClass => {

    /**
     * @polymer
     * @mixinClass
     * @implements {Polymer_TemplateStamp}
     */
    class TemplateStamp extends superClass {

      /**
       * Scans a template to produce template metadata.
       *
       * Template-specific metadata are stored in the object returned, and node-
       * specific metadata are stored in objects in its flattened `nodeInfoList`
       * array.  Only nodes in the template that were parsed as nodes of
       * interest contain an object in `nodeInfoList`.  Each `nodeInfo` object
       * contains an `index` (`childNodes` index in parent) and optionally
       * `parent`, which points to node info of its parent (including its index).
       *
       * The template metadata object returned from this method has the following
       * structure (many fields optional):
       *
       * ```js
       *   {
       *     // Flattened list of node metadata (for nodes that generated metadata)
       *     nodeInfoList: [
       *       {
       *         // `id` attribute for any nodes with id's for generating `$` map
       *         id: {string},
       *         // `on-event="handler"` metadata
       *         events: [
       *           {
       *             name: {string},   // event name
       *             value: {string},  // handler method name
       *           }, ...
       *         ],
       *         // Notes when the template contained a `<slot>` for shady DOM
       *         // optimization purposes
       *         hasInsertionPoint: {boolean},
       *         // For nested `<template>`` nodes, nested template metadata
       *         templateInfo: {object}, // nested template metadata
       *         // Metadata to allow efficient retrieval of instanced node
       *         // corresponding to this metadata
       *         parentInfo: {number},   // reference to parent nodeInfo>
       *         parentIndex: {number},  // index in parent's `childNodes` collection
       *         infoIndex: {number},    // index of this `nodeInfo` in `templateInfo.nodeInfoList`
       *       },
       *       ...
       *     ],
       *     // When true, the template had the `strip-whitespace` attribute
       *     // or was nested in a template with that setting
       *     stripWhitespace: {boolean},
       *     // For nested templates, nested template content is moved into
       *     // a document fragment stored here; this is an optimization to
       *     // avoid the cost of nested template cloning
       *     content: {DocumentFragment}
       *   }
       * ```
       *
       * This method kicks off a recursive treewalk as follows:
       *
       * ```
       *    _parseTemplate <---------------------+
       *      _parseTemplateContent              |
       *        _parseTemplateNode  <------------|--+
       *          _parseTemplateNestedTemplate --+  |
       *          _parseTemplateChildNodes ---------+
       *          _parseTemplateNodeAttributes
       *            _parseTemplateNodeAttribute
       *
       * ```
       *
       * These methods may be overridden to add custom metadata about templates
       * to either `templateInfo` or `nodeInfo`.
       *
       * Note that this method may be destructive to the template, in that
       * e.g. event annotations may be removed after being noted in the
       * template metadata.
       *
       * @param {!HTMLTemplateElement} template Template to parse
       * @param {TemplateInfo=} outerTemplateInfo Template metadata from the outer
       *   template, for parsing nested templates
       * @return {!TemplateInfo} Parsed template metadata
       */
      static _parseTemplate(template, outerTemplateInfo) {
        // since a template may be re-used, memo-ize metadata
        if (!template._templateInfo) {
          let templateInfo = template._templateInfo = {};
          templateInfo.nodeInfoList = [];
          templateInfo.stripWhiteSpace =
            (outerTemplateInfo && outerTemplateInfo.stripWhiteSpace) ||
            template.hasAttribute('strip-whitespace');
          this._parseTemplateContent(template, templateInfo, {parent: null});
        }
        return template._templateInfo;
      }

      static _parseTemplateContent(template, templateInfo, nodeInfo) {
        return this._parseTemplateNode(template.content, templateInfo, nodeInfo);
      }

      /**
       * Parses template node and adds template and node metadata based on
       * the current node, and its `childNodes` and `attributes`.
       *
       * This method may be overridden to add custom node or template specific
       * metadata based on this node.
       *
       * @param {Node} node Node to parse
       * @param {!TemplateInfo} templateInfo Template metadata for current template
       * @param {!NodeInfo} nodeInfo Node metadata for current template.
       * @return {boolean} `true` if the visited node added node-specific
       *   metadata to `nodeInfo`
       */
      static _parseTemplateNode(node, templateInfo, nodeInfo) {
        let noted;
        let element = /** @type Element */(node);
        if (element.localName == 'template' && !element.hasAttribute('preserve-content')) {
          noted = this._parseTemplateNestedTemplate(element, templateInfo, nodeInfo) || noted;
        } else if (element.localName === 'slot') {
          // For ShadyDom optimization, indicating there is an insertion point
          templateInfo.hasInsertionPoint = true;
        }
        if (element.firstChild) {
          noted = this._parseTemplateChildNodes(element, templateInfo, nodeInfo) || noted;
        }
        if (element.hasAttributes && element.hasAttributes()) {
          noted = this._parseTemplateNodeAttributes(element, templateInfo, nodeInfo) || noted;
        }
        return noted;
      }

      /**
       * Parses template child nodes for the given root node.
       *
       * This method also wraps whitelisted legacy template extensions
       * (`is="dom-if"` and `is="dom-repeat"`) with their equivalent element
       * wrappers, collapses text nodes, and strips whitespace from the template
       * if the `templateInfo.stripWhitespace` setting was provided.
       *
       * @param {Node} root Root node whose `childNodes` will be parsed
       * @param {!TemplateInfo} templateInfo Template metadata for current template
       * @param {!NodeInfo} nodeInfo Node metadata for current template.
       */
      static _parseTemplateChildNodes(root, templateInfo, nodeInfo) {
        for (let node=root.firstChild, parentIndex=0, next; node; node=next) {
          // Wrap templates
          if (node.localName == 'template') {
            node = wrapTemplateExtension(node);
          }
          // collapse adjacent textNodes: fixes an IE issue that can cause
          // text nodes to be inexplicably split =(
          // note that root.normalize() should work but does not so we do this
          // manually.
          next = node.nextSibling;
          if (node.nodeType === Node.TEXT_NODE) {
            let /** Node */ n = next;
            while (n && (n.nodeType === Node.TEXT_NODE)) {
              node.textContent += n.textContent;
              next = n.nextSibling;
              root.removeChild(n);
              n = next;
            }
            // optionally strip whitespace
            if (templateInfo.stripWhiteSpace && !node.textContent.trim()) {
              root.removeChild(node);
              continue;
            }
          }
          let childInfo = { parentIndex, parentInfo: nodeInfo };
          if (this._parseTemplateNode(node, templateInfo, childInfo)) {
            childInfo.infoIndex = templateInfo.nodeInfoList.push(/** @type {!NodeInfo} */(childInfo)) - 1;
          }
          // Increment if not removed
          if (node.parentNode) {
            parentIndex++;
          }
        }
      }

      /**
       * Parses template content for the given nested `<template>`.
       *
       * Nested template info is stored as `templateInfo` in the current node's
       * `nodeInfo`. `template.content` is removed and stored in `templateInfo`.
       * It will then be the responsibility of the host to set it back to the
       * template and for users stamping nested templates to use the
       * `_contentForTemplate` method to retrieve the content for this template
       * (an optimization to avoid the cost of cloning nested template content).
       *
       * @param {HTMLTemplateElement} node Node to parse (a <template>)
       * @param {TemplateInfo} outerTemplateInfo Template metadata for current template
       *   that includes the template `node`
       * @param {!NodeInfo} nodeInfo Node metadata for current template.
       * @return {boolean} `true` if the visited node added node-specific
       *   metadata to `nodeInfo`
       */
      static _parseTemplateNestedTemplate(node, outerTemplateInfo, nodeInfo) {
        let templateInfo = this._parseTemplate(node, outerTemplateInfo);
        let content = templateInfo.content =
          node.content.ownerDocument.createDocumentFragment();
        content.appendChild(node.content);
        nodeInfo.templateInfo = templateInfo;
        return true;
      }

      /**
       * Parses template node attributes and adds node metadata to `nodeInfo`
       * for nodes of interest.
       *
       * @param {Element} node Node to parse
       * @param {TemplateInfo} templateInfo Template metadata for current template
       * @param {NodeInfo} nodeInfo Node metadata for current template.
       * @return {boolean} `true` if the visited node added node-specific
       *   metadata to `nodeInfo`
       */
      static _parseTemplateNodeAttributes(node, templateInfo, nodeInfo) {
        // Make copy of original attribute list, since the order may change
        // as attributes are added and removed
        let noted = false;
        let attrs = Array.from(node.attributes);
        for (let i=attrs.length-1, a; (a=attrs[i]); i--) {
          noted = this._parseTemplateNodeAttribute(node, templateInfo, nodeInfo, a.name, a.value) || noted;
        }
        return noted;
      }

      /**
       * Parses a single template node attribute and adds node metadata to
       * `nodeInfo` for attributes of interest.
       *
       * This implementation adds metadata for `on-event="handler"` attributes
       * and `id` attributes.
       *
       * @param {Element} node Node to parse
       * @param {!TemplateInfo} templateInfo Template metadata for current template
       * @param {!NodeInfo} nodeInfo Node metadata for current template.
       * @param {string} name Attribute name
       * @param {string} value Attribute value
       * @return {boolean} `true` if the visited node added node-specific
       *   metadata to `nodeInfo`
       */
      static _parseTemplateNodeAttribute(node, templateInfo, nodeInfo, name, value) {
        // events (on-*)
        if (name.slice(0, 3) === 'on-') {
          node.removeAttribute(name);
          nodeInfo.events = nodeInfo.events || [];
          nodeInfo.events.push({
            name: name.slice(3),
            value
          });
          return true;
        }
        // static id
        else if (name === 'id') {
          nodeInfo.id = value;
          return true;
        }
        return false;
      }

      /**
       * Returns the `content` document fragment for a given template.
       *
       * For nested templates, Polymer performs an optimization to cache nested
       * template content to avoid the cost of cloning deeply nested templates.
       * This method retrieves the cached content for a given template.
       *
       * @param {HTMLTemplateElement} template Template to retrieve `content` for
       * @return {DocumentFragment} Content fragment
       */
      static _contentForTemplate(template) {
        let templateInfo = /** @type {HTMLTemplateElementWithInfo} */ (template)._templateInfo;
        return (templateInfo && templateInfo.content) || template.content;
      }

      /**
       * Clones the provided template content and returns a document fragment
       * containing the cloned dom.
       *
       * The template is parsed (once and memoized) using this library's
       * template parsing features, and provides the following value-added
       * features:
       * * Adds declarative event listeners for `on-event="handler"` attributes
       * * Generates an "id map" for all nodes with id's under `$` on returned
       *   document fragment
       * * Passes template info including `content` back to templates as
       *   `_templateInfo` (a performance optimization to avoid deep template
       *   cloning)
       *
       * Note that the memoized template parsing process is destructive to the
       * template: attributes for bindings and declarative event listeners are
       * removed after being noted in notes, and any nested `<template>.content`
       * is removed and stored in notes as well.
       *
       * @param {!HTMLTemplateElement} template Template to stamp
       * @return {!StampedTemplate} Cloned template content
       */
      _stampTemplate(template) {
        // Polyfill support: bootstrap the template if it has not already been
        if (template && !template.content &&
            window.HTMLTemplateElement && HTMLTemplateElement.decorate) {
          HTMLTemplateElement.decorate(template);
        }
        let templateInfo = this.constructor._parseTemplate(template);
        let nodeInfo = templateInfo.nodeInfoList;
        let content = templateInfo.content || template.content;
        let dom = /** @type DocumentFragment */ (document.importNode(content, true));
        // NOTE: ShadyDom optimization indicating there is an insertion point
        dom.__noInsertionPoint = !templateInfo.hasInsertionPoint;
        let nodes = dom.nodeList = new Array(nodeInfo.length);
        dom.$ = {};
        for (let i=0, l=nodeInfo.length, info; (i<l) && (info=nodeInfo[i]); i++) {
          let node = nodes[i] = findTemplateNode(dom, info);
          applyIdToMap(this, dom.$, node, info);
          applyTemplateContent(this, node, info);
          applyEventListener(this, node, info);
        }
        return /** @type {!StampedTemplate} */(dom);
      }

      /**
       * Adds an event listener by method name for the event provided.
       *
       * This method generates a handler function that looks up the method
       * name at handling time.
       *
       * @param {Node} node Node to add listener on
       * @param {string} eventName Name of event
       * @param {string} methodName Name of method
       * @param {*=} context Context the method will be called on (defaults
       *   to `node`)
       * @return {Function} Generated handler function
       */
      _addMethodEventListenerToNode(node, eventName, methodName, context) {
        context = context || node;
        let handler = createNodeEventHandler(context, eventName, methodName);
        this._addEventListenerToNode(node, eventName, handler);
        return handler;
      }

      /**
       * Override point for adding custom or simulated event handling.
       *
       * @param {Node} node Node to add event listener to
       * @param {string} eventName Name of event
       * @param {Function} handler Listener function to add
       */
      _addEventListenerToNode(node, eventName, handler) {
        node.addEventListener(eventName, handler);
      }

      /**
       * Override point for adding custom or simulated event handling.
       *
       * @param {Node} node Node to remove event listener from
       * @param {string} eventName Name of event
       * @param {Function} handler Listener function to remove
       */
      _removeEventListenerFromNode(node, eventName, handler) {
        node.removeEventListener(eventName, handler);
      }

    }

    return TemplateStamp;

  });

})();
</script>