<!DOCTYPE html>
<!--
Copyright (c) 2013 The Chromium Authors. All rights reserved.
Use of this source code is governed by a BSD-style license that can be
found in the LICENSE file.
-->
<link rel="import" href="/tracing/base/base.html">

<script>
'use strict';

/**
 * @fileoverview Helper code for working with Polymer.
 */
tr.exportTo('tr.ui.b', function() {

  Object.observe(Polymer.elements, clearPolymerElementCaches);

  var elementsByName = undefined;
  var elementsThatExtend = undefined;
  var elementSubclasses = undefined;
  function clearPolymerElementCaches() {
    elementsByName = {};
    elementsThatExtend = undefined;
    elementSubclasses = {};
  }

  function buildElementMapsIfNeeded() {
    if (elementsThatExtend !== undefined && elementsByName !== undefined)
      return;
    elementsByName = {};
    elementsThatExtend = {};
    Polymer.elements.forEach(function(element) {
      if (elementsByName[element.name])
        throw new Error('Something is strange: dupe polymer element names');

      elementsByName[element.name] = element;

      if (element.extends) {
        if (elementsThatExtend[element.extends] === undefined)
          elementsThatExtend[element.extends] = [];
        elementsThatExtend[element.extends].push(element.name);
      }
    });
  }

  function getPolymerElementNamed(tagName) {
    buildElementMapsIfNeeded();
    return elementsByName[tagName];
  }

  function getPolymerElementsThatSubclass(tagName) {
    if (Polymer.waitingFor().length) {
      throw new Error('There are unresolved polymer elements. ' +
        'Wait until Polymer.whenReady');
    }

    buildElementMapsIfNeeded();

    var element = getPolymerElementNamed(tagName);
    if (!element)
      throw new Error(tagName + ' is not a polymer element');

    if (elementSubclasses === undefined)
      elementSubclasses = {};

    if (elementSubclasses[tagName] === undefined) {
      var immediateSubElements = elementsThatExtend[element.name];
      var allSubElements = [];
      if (immediateSubElements !== undefined && immediateSubElements.length) {
        immediateSubElements.forEach(function(subElement) {
          allSubElements.push(subElement);
          allSubElements.push.apply(
            allSubElements, getPolymerElementsThatSubclass(subElement));
        });
      }
      elementSubclasses[tagName] = allSubElements;
    }
    return elementSubclasses[tagName];
  }

  return {
    getPolymerElementNamed: getPolymerElementNamed,
    getPolymerElementsThatSubclass: getPolymerElementsThatSubclass
  };
});
</script>