// Copyright (c) 2012 The Polymer Authors. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//    * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//    * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//    * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
if (typeof WeakMap === 'undefined') {
  (function() {
    var defineProperty = Object.defineProperty;
    var counter = Date.now() % 1e9;

    var WeakMap = function() {
      this.name = '__st' + (Math.random() * 1e9 >>> 0) + (counter++ + '__');
    };

    WeakMap.prototype = {
      set: function(key, value) {
        var entry = key[this.name];
        if (entry && entry[0] === key)
          entry[1] = value;
        else
          defineProperty(key, this.name, {value: [key, value], writable: true});
      },
      get: function(key) {
        var entry;
        return (entry = key[this.name]) && entry[0] === key ?
            entry[1] : undefined;
      },
      delete: function(key) {
        this.set(key, undefined);
      }
    };

    window.WeakMap = WeakMap;
  })();
}

window.CustomElements = window.CustomElements || {flags:{}};
(function(scope){

var logFlags = window.logFlags || {};
var IMPORT_LINK_TYPE = window.HTMLImports ? HTMLImports.IMPORT_LINK_TYPE : 'none';

// walk the subtree rooted at node, applying 'find(element, data)' function
// to each element
// if 'find' returns true for 'element', do not search element's subtree
function findAll(node, find, data) {
  var e = node.firstElementChild;
  if (!e) {
    e = node.firstChild;
    while (e && e.nodeType !== Node.ELEMENT_NODE) {
      e = e.nextSibling;
    }
  }
  while (e) {
    if (find(e, data) !== true) {
      findAll(e, find, data);
    }
    e = e.nextElementSibling;
  }
  return null;
}

// walk all shadowRoots on a given node.
function forRoots(node, cb) {
  var root = node.shadowRoot;
  while(root) {
    forSubtree(root, cb);
    root = root.olderShadowRoot;
  }
}

// walk the subtree rooted at node, including descent into shadow-roots,
// applying 'cb' to each element
function forSubtree(node, cb) {
  //logFlags.dom && node.childNodes && node.childNodes.length && console.group('subTree: ', node);
  findAll(node, function(e) {
    if (cb(e)) {
      return true;
    }
    forRoots(e, cb);
  });
  forRoots(node, cb);
  //logFlags.dom && node.childNodes && node.childNodes.length && console.groupEnd();
}

// manage lifecycle on added node
function added(node) {
  if (upgrade(node)) {
    insertedNode(node);
    return true;
  }
  inserted(node);
}

// manage lifecycle on added node's subtree only
function addedSubtree(node) {
  forSubtree(node, function(e) {
    if (added(e)) {
      return true;
    }
  });
}

// manage lifecycle on added node and it's subtree
function addedNode(node) {
  return added(node) || addedSubtree(node);
}

// upgrade custom elements at node, if applicable
function upgrade(node) {
  if (!node.__upgraded__ && node.nodeType === Node.ELEMENT_NODE) {
    var type = node.getAttribute('is') || node.localName;
    var definition = scope.registry[type];
    if (definition) {
      logFlags.dom && console.group('upgrade:', node.localName);
      scope.upgrade(node);
      logFlags.dom && console.groupEnd();
      return true;
    }
  }
}

function insertedNode(node) {
  inserted(node);
  if (inDocument(node)) {
    forSubtree(node, function(e) {
      inserted(e);
    });
  }
}


// TODO(sorvell): on platforms without MutationObserver, mutations may not be 
// reliable and therefore attached/detached are not reliable.
// To make these callbacks less likely to fail, we defer all inserts and removes
// to give a chance for elements to be inserted into dom. 
// This ensures attachedCallback fires for elements that are created and 
// immediately added to dom.
var hasPolyfillMutations = (!window.MutationObserver ||
    (window.MutationObserver === window.JsMutationObserver));
scope.hasPolyfillMutations = hasPolyfillMutations;

var isPendingMutations = false;
var pendingMutations = [];
function deferMutation(fn) {
  pendingMutations.push(fn);
  if (!isPendingMutations) {
    isPendingMutations = true;
    var async = (window.Platform && window.Platform.endOfMicrotask) ||
        setTimeout;
    async(takeMutations);
  }
}

function takeMutations() {
  isPendingMutations = false;
  var $p = pendingMutations;
  for (var i=0, l=$p.length, p; (i<l) && (p=$p[i]); i++) {
    p();
  }
  pendingMutations = [];
}

function inserted(element) {
  if (hasPolyfillMutations) {
    deferMutation(function() {
      _inserted(element);
    });
  } else {
    _inserted(element);
  }
}

// TODO(sjmiles): if there are descents into trees that can never have inDocument(*) true, fix this
function _inserted(element) {
  // TODO(sjmiles): it's possible we were inserted and removed in the space
  // of one microtask, in which case we won't be 'inDocument' here
  // But there are other cases where we are testing for inserted without
  // specific knowledge of mutations, and must test 'inDocument' to determine
  // whether to call inserted
  // If we can factor these cases into separate code paths we can have
  // better diagnostics.
  // TODO(sjmiles): when logging, do work on all custom elements so we can
  // track behavior even when callbacks not defined
  //console.log('inserted: ', element.localName);
  if (element.attachedCallback || element.detachedCallback || (element.__upgraded__ && logFlags.dom)) {
    logFlags.dom && console.group('inserted:', element.localName);
    if (inDocument(element)) {
      element.__inserted = (element.__inserted || 0) + 1;
      // if we are in a 'removed' state, bluntly adjust to an 'inserted' state
      if (element.__inserted < 1) {
        element.__inserted = 1;
      }
      // if we are 'over inserted', squelch the callback
      if (element.__inserted > 1) {
        logFlags.dom && console.warn('inserted:', element.localName,
          'insert/remove count:', element.__inserted)
      } else if (element.attachedCallback) {
        logFlags.dom && console.log('inserted:', element.localName);
        element.attachedCallback();
      }
    }
    logFlags.dom && console.groupEnd();
  }
}

function removedNode(node) {
  removed(node);
  forSubtree(node, function(e) {
    removed(e);
  });
}

function removed(element) {
  if (hasPolyfillMutations) {
    deferMutation(function() {
      _removed(element);
    });
  } else {
    _removed(element);
  }
}

function _removed(element) {
  // TODO(sjmiles): temporary: do work on all custom elements so we can track
  // behavior even when callbacks not defined
  if (element.attachedCallback || element.detachedCallback || (element.__upgraded__ && logFlags.dom)) {
    logFlags.dom && console.group('removed:', element.localName);
    if (!inDocument(element)) {
      element.__inserted = (element.__inserted || 0) - 1;
      // if we are in a 'inserted' state, bluntly adjust to an 'removed' state
      if (element.__inserted > 0) {
        element.__inserted = 0;
      }
      // if we are 'over removed', squelch the callback
      if (element.__inserted < 0) {
        logFlags.dom && console.warn('removed:', element.localName,
            'insert/remove count:', element.__inserted)
      } else if (element.detachedCallback) {
        element.detachedCallback();
      }
    }
    logFlags.dom && console.groupEnd();
  }
}

// SD polyfill intrustion due mainly to the fact that 'document'
// is not entirely wrapped
function wrapIfNeeded(node) {
  return window.ShadowDOMPolyfill ? ShadowDOMPolyfill.wrapIfNeeded(node)
      : node;
}

function inDocument(element) {
  var p = element;
  var doc = wrapIfNeeded(document);
  while (p) {
    if (p == doc) {
      return true;
    }
    p = p.parentNode || p.host;
  }
}

function watchShadow(node) {
  if (node.shadowRoot && !node.shadowRoot.__watched) {
    logFlags.dom && console.log('watching shadow-root for: ', node.localName);
    // watch all unwatched roots...
    var root = node.shadowRoot;
    while (root) {
      watchRoot(root);
      root = root.olderShadowRoot;
    }
  }
}

function watchRoot(root) {
  if (!root.__watched) {
    observe(root);
    root.__watched = true;
  }
}

function handler(mutations) {
  //
  if (logFlags.dom) {
    var mx = mutations[0];
    if (mx && mx.type === 'childList' && mx.addedNodes) {
        if (mx.addedNodes) {
          var d = mx.addedNodes[0];
          while (d && d !== document && !d.host) {
            d = d.parentNode;
          }
          var u = d && (d.URL || d._URL || (d.host && d.host.localName)) || '';
          u = u.split('/?').shift().split('/').pop();
        }
    }
    console.group('mutations (%d) [%s]', mutations.length, u || '');
  }
  //
  mutations.forEach(function(mx) {
    //logFlags.dom && console.group('mutation');
    if (mx.type === 'childList') {
      forEach(mx.addedNodes, function(n) {
        //logFlags.dom && console.log(n.localName);
        if (!n.localName) {
          return;
        }
        // nodes added may need lifecycle management
        addedNode(n);
      });
      // removed nodes may need lifecycle management
      forEach(mx.removedNodes, function(n) {
        //logFlags.dom && console.log(n.localName);
        if (!n.localName) {
          return;
        }
        removedNode(n);
      });
    }
    //logFlags.dom && console.groupEnd();
  });
  logFlags.dom && console.groupEnd();
};

var observer = new MutationObserver(handler);

function takeRecords() {
  // TODO(sjmiles): ask Raf why we have to call handler ourselves
  handler(observer.takeRecords());
  takeMutations();
}

var forEach = Array.prototype.forEach.call.bind(Array.prototype.forEach);

function observe(inRoot) {
  observer.observe(inRoot, {childList: true, subtree: true});
}

function observeDocument(doc) {
  observe(doc);
}

function upgradeDocument(doc) {
  logFlags.dom && console.group('upgradeDocument: ', (doc.baseURI).split('/').pop());
  addedNode(doc);
  logFlags.dom && console.groupEnd();
}

function upgradeDocumentTree(doc) {
  doc = wrapIfNeeded(doc);
  upgradeDocument(doc);
  //console.log('upgradeDocumentTree: ', (doc.baseURI).split('/').pop());
  // upgrade contained imported documents
  var imports = doc.querySelectorAll('link[rel=' + IMPORT_LINK_TYPE + ']');
  for (var i=0, l=imports.length, n; (i<l) && (n=imports[i]); i++) {
    if (n.import && n.import.__parsed) {
      upgradeDocumentTree(n.import);
    }
  }
}

// exports
scope.IMPORT_LINK_TYPE = IMPORT_LINK_TYPE;
scope.watchShadow = watchShadow;
scope.upgradeDocumentTree = upgradeDocumentTree;
scope.upgradeAll = addedNode;
scope.upgradeSubtree = addedSubtree;

scope.observeDocument = observeDocument;
scope.upgradeDocument = upgradeDocument;

scope.takeRecords = takeRecords;

})(window.CustomElements);

/**
 * Implements `document.register`
 * @module CustomElements
*/

/**
 * Polyfilled extensions to the `document` object.
 * @class Document
*/

(function(scope) {

// imports

if (!scope) {
  scope = window.CustomElements = {flags:{}};
}
var flags = scope.flags;

// native document.registerElement?

var hasNative = Boolean(document.registerElement);
// TODO(sorvell): See https://github.com/Polymer/polymer/issues/399
// we'll address this by defaulting to CE polyfill in the presence of the SD
// polyfill. This will avoid spamming excess attached/detached callbacks.
// If there is a compelling need to run CE native with SD polyfill, 
// we'll need to fix this issue.
var useNative = !flags.register && hasNative && !window.ShadowDOMPolyfill;

if (useNative) {

  // stub
  var nop = function() {};

  // exports
  scope.registry = {};
  scope.upgradeElement = nop;

  scope.watchShadow = nop;
  scope.upgrade = nop;
  scope.upgradeAll = nop;
  scope.upgradeSubtree = nop;
  scope.observeDocument = nop;
  scope.upgradeDocument = nop;
  scope.takeRecords = nop;

} else {

  /**
   * Registers a custom tag name with the document.
   *
   * When a registered element is created, a `readyCallback` method is called
   * in the scope of the element. The `readyCallback` method can be specified on
   * either `options.prototype` or `options.lifecycle` with the latter taking
   * precedence.
   *
   * @method register
   * @param {String} name The tag name to register. Must include a dash ('-'),
   *    for example 'x-component'.
   * @param {Object} options
   *    @param {String} [options.extends]
   *      (_off spec_) Tag name of an element to extend (or blank for a new
   *      element). This parameter is not part of the specification, but instead
   *      is a hint for the polyfill because the extendee is difficult to infer.
   *      Remember that the input prototype must chain to the extended element's
   *      prototype (or HTMLElement.prototype) regardless of the value of
   *      `extends`.
   *    @param {Object} options.prototype The prototype to use for the new
   *      element. The prototype must inherit from HTMLElement.
   *    @param {Object} [options.lifecycle]
   *      Callbacks that fire at important phases in the life of the custom
   *      element.
   *
   * @example
   *      FancyButton = document.registerElement("fancy-button", {
   *        extends: 'button',
   *        prototype: Object.create(HTMLButtonElement.prototype, {
   *          readyCallback: {
   *            value: function() {
   *              console.log("a fancy-button was created",
   *            }
   *          }
   *        })
   *      });
   * @return {Function} Constructor for the newly registered type.
   */
  function register(name, options) {
    //console.warn('document.registerElement("' + name + '", ', options, ')');
    // construct a defintion out of options
    // TODO(sjmiles): probably should clone options instead of mutating it
    var definition = options || {};
    if (!name) {
      // TODO(sjmiles): replace with more appropriate error (EricB can probably
      // offer guidance)
      throw new Error('document.registerElement: first argument `name` must not be empty');
    }
    if (name.indexOf('-') < 0) {
      // TODO(sjmiles): replace with more appropriate error (EricB can probably
      // offer guidance)
      throw new Error('document.registerElement: first argument (\'name\') must contain a dash (\'-\'). Argument provided was \'' + String(name) + '\'.');
    }
    // elements may only be registered once
    if (getRegisteredDefinition(name)) {
      throw new Error('DuplicateDefinitionError: a type with name \'' + String(name) + '\' is already registered');
    }
    // must have a prototype, default to an extension of HTMLElement
    // TODO(sjmiles): probably should throw if no prototype, check spec
    if (!definition.prototype) {
      // TODO(sjmiles): replace with more appropriate error (EricB can probably
      // offer guidance)
      throw new Error('Options missing required prototype property');
    }
    // record name
    definition.__name = name.toLowerCase();
    // ensure a lifecycle object so we don't have to null test it
    definition.lifecycle = definition.lifecycle || {};
    // build a list of ancestral custom elements (for native base detection)
    // TODO(sjmiles): we used to need to store this, but current code only
    // uses it in 'resolveTagName': it should probably be inlined
    definition.ancestry = ancestry(definition.extends);
    // extensions of native specializations of HTMLElement require localName
    // to remain native, and use secondary 'is' specifier for extension type
    resolveTagName(definition);
    // some platforms require modifications to the user-supplied prototype
    // chain
    resolvePrototypeChain(definition);
    // overrides to implement attributeChanged callback
    overrideAttributeApi(definition.prototype);
    // 7.1.5: Register the DEFINITION with DOCUMENT
    registerDefinition(definition.__name, definition);
    // 7.1.7. Run custom element constructor generation algorithm with PROTOTYPE
    // 7.1.8. Return the output of the previous step.
    definition.ctor = generateConstructor(definition);
    definition.ctor.prototype = definition.prototype;
    // force our .constructor to be our actual constructor
    definition.prototype.constructor = definition.ctor;
    // if initial parsing is complete
    if (scope.ready || scope.performedInitialDocumentUpgrade) {
      // upgrade any pre-existing nodes of this type
      scope.upgradeDocumentTree(document);
    }
    return definition.ctor;
  }

  function ancestry(extnds) {
    var extendee = getRegisteredDefinition(extnds);
    if (extendee) {
      return ancestry(extendee.extends).concat([extendee]);
    }
    return [];
  }

  function resolveTagName(definition) {
    // if we are explicitly extending something, that thing is our
    // baseTag, unless it represents a custom component
    var baseTag = definition.extends;
    // if our ancestry includes custom components, we only have a
    // baseTag if one of them does
    for (var i=0, a; (a=definition.ancestry[i]); i++) {
      baseTag = a.is && a.tag;
    }
    // our tag is our baseTag, if it exists, and otherwise just our name
    definition.tag = baseTag || definition.__name;
    if (baseTag) {
      // if there is a base tag, use secondary 'is' specifier
      definition.is = definition.__name;
    }
  }

  function resolvePrototypeChain(definition) {
    // if we don't support __proto__ we need to locate the native level
    // prototype for precise mixing in
    if (!Object.__proto__) {
      // default prototype
      var nativePrototype = HTMLElement.prototype;
      // work out prototype when using type-extension
      if (definition.is) {
        var inst = document.createElement(definition.tag);
        nativePrototype = Object.getPrototypeOf(inst);
      }
      // ensure __proto__ reference is installed at each point on the prototype
      // chain.
      // NOTE: On platforms without __proto__, a mixin strategy is used instead
      // of prototype swizzling. In this case, this generated __proto__ provides
      // limited support for prototype traversal.
      var proto = definition.prototype, ancestor;
      while (proto && (proto !== nativePrototype)) {
        var ancestor = Object.getPrototypeOf(proto);
        proto.__proto__ = ancestor;
        proto = ancestor;
      }
    }
    // cache this in case of mixin
    definition.native = nativePrototype;
  }

  // SECTION 4

  function instantiate(definition) {
    // 4.a.1. Create a new object that implements PROTOTYPE
    // 4.a.2. Let ELEMENT by this new object
    //
    // the custom element instantiation algorithm must also ensure that the
    // output is a valid DOM element with the proper wrapper in place.
    //
    return upgrade(domCreateElement(definition.tag), definition);
  }

  function upgrade(element, definition) {
    // some definitions specify an 'is' attribute
    if (definition.is) {
      element.setAttribute('is', definition.is);
    }
    // remove 'unresolved' attr, which is a standin for :unresolved.
    element.removeAttribute('unresolved');
    // make 'element' implement definition.prototype
    implement(element, definition);
    // flag as upgraded
    element.__upgraded__ = true;
    // there should never be a shadow root on element at this point
    // we require child nodes be upgraded before `created`
    scope.upgradeSubtree(element);
    // lifecycle management
    created(element);
    // OUTPUT
    return element;
  }

  function implement(element, definition) {
    // prototype swizzling is best
    if (Object.__proto__) {
      element.__proto__ = definition.prototype;
    } else {
      // where above we can re-acquire inPrototype via
      // getPrototypeOf(Element), we cannot do so when
      // we use mixin, so we install a magic reference
      customMixin(element, definition.prototype, definition.native);

      // Dart note: make sure we pick up the right constructor.
      // dart2js depends on this for dart:mirrors caching to work.
      // See tests/html/custom/mirrors_test.dart
      element.constructor = definition.prototype.constructor;
      element.__proto__ = definition.prototype;
    }
  }

  function customMixin(inTarget, inSrc, inNative) {
    // TODO(sjmiles): 'used' allows us to only copy the 'youngest' version of
    // any property. This set should be precalculated. We also need to
    // consider this for supporting 'super'.
    var used = {};
    // start with inSrc
    var p = inSrc;
    // sometimes the default is HTMLUnknownElement.prototype instead of
    // HTMLElement.prototype, so we add a test
    // the idea is to avoid mixing in native prototypes, so adding
    // the second test is WLOG
    while (p !== inNative && p !== HTMLUnknownElement.prototype) {
      var keys = Object.getOwnPropertyNames(p);
      for (var i=0, k; k=keys[i]; i++) {
        if (!used[k]) {
          Object.defineProperty(inTarget, k,
              Object.getOwnPropertyDescriptor(p, k));
          used[k] = 1;
        }
      }
      p = Object.getPrototypeOf(p);
    }
  }

  function created(element) {
    // invoke createdCallback
    if (element.createdCallback) {
      element.createdCallback();
    }
  }

  // attribute watching

  function overrideAttributeApi(prototype) {
    // overrides to implement callbacks
    // TODO(sjmiles): should support access via .attributes NamedNodeMap
    // TODO(sjmiles): preserves user defined overrides, if any
    if (prototype.setAttribute._polyfilled) {
      return;
    }
    var setAttribute = prototype.setAttribute;
    prototype.setAttribute = function(name, value) {
      changeAttribute.call(this, name, value, setAttribute);
    }
    var removeAttribute = prototype.removeAttribute;
    prototype.removeAttribute = function(name) {
      changeAttribute.call(this, name, null, removeAttribute);
    }
    prototype.setAttribute._polyfilled = true;
  }

  // https://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/custom/
  // index.html#dfn-attribute-changed-callback
  function changeAttribute(name, value, operation) {
    var oldValue = this.getAttribute(name);
    operation.apply(this, arguments);
    var newValue = this.getAttribute(name);
    if (this.attributeChangedCallback
        && (newValue !== oldValue)) {
      this.attributeChangedCallback(name, oldValue, newValue);
    }
  }

  // element registry (maps tag names to definitions)

  var registry = {};

  function getRegisteredDefinition(name) {
    if (name) {
      return registry[name.toLowerCase()];
    }
  }

  function registerDefinition(name, definition) {
    if (registry[name]) {
      throw new Error('a type with that name is already registered.');
    }
    registry[name] = definition;
  }

  function generateConstructor(definition) {
    return function() {
      return instantiate(definition);
    };
  }

  function createElement(tag, typeExtension) {
    // TODO(sjmiles): ignore 'tag' when using 'typeExtension', we could
    // error check it, or perhaps there should only ever be one argument
    var definition = getRegisteredDefinition(typeExtension || tag);
    if (definition) {
      if (tag == definition.tag && typeExtension == definition.is) {
        return new definition.ctor();
      }
      // Handle empty string for type extension.
      if (!typeExtension && !definition.is) {
        return new definition.ctor();
      }
    }

    if (typeExtension) {
      var element = createElement(tag);
      element.setAttribute('is', typeExtension);
      return element;
    }
    var element = domCreateElement(tag);
    // Custom tags should be HTMLElements even if not upgraded.
    if (tag.indexOf('-') >= 0) {
      implement(element, HTMLElement);
    }
    return element;
  }

  function upgradeElement(element) {
    if (!element.__upgraded__ && (element.nodeType === Node.ELEMENT_NODE)) {
      var is = element.getAttribute('is');
      var definition = registry[is || element.localName];
      if (definition) {
        if (is && definition.tag == element.localName) {
          return upgrade(element, definition);
        } else if (!is && !definition.extends) {
          return upgrade(element, definition);
        }
      }
    }
  }

  function cloneNode(deep) {
    // call original clone
    var n = domCloneNode.call(this, deep);
    // upgrade the element and subtree
    scope.upgradeAll(n);
    // return the clone
    return n;
  }
  // capture native createElement before we override it

  var domCreateElement = document.createElement.bind(document);

  // capture native cloneNode before we override it

  var domCloneNode = Node.prototype.cloneNode;

  // exports

  document.registerElement = register;
  document.createElement = createElement; // override
  Node.prototype.cloneNode = cloneNode; // override

  scope.registry = registry;

  /**
   * Upgrade an element to a custom element. Upgrading an element
   * causes the custom prototype to be applied, an `is` attribute
   * to be attached (as needed), and invocation of the `readyCallback`.
   * `upgrade` does nothing if the element is already upgraded, or
   * if it matches no registered custom tag name.
   *
   * @method ugprade
   * @param {Element} element The element to upgrade.
   * @return {Element} The upgraded element.
   */
  scope.upgrade = upgradeElement;
}

// bc
document.register = document.registerElement;

scope.hasNative = hasNative;
scope.useNative = useNative;

})(window.CustomElements);

(function(scope) {

// import

var IMPORT_LINK_TYPE = scope.IMPORT_LINK_TYPE;

// highlander object for parsing a document tree

var parser = {
  selectors: [
    'link[rel=' + IMPORT_LINK_TYPE + ']'
  ],
  map: {
    link: 'parseLink'
  },
  parse: function(inDocument) {
    if (!inDocument.__parsed) {
      // only parse once
      inDocument.__parsed = true;
      // all parsable elements in inDocument (depth-first pre-order traversal)
      var elts = inDocument.querySelectorAll(parser.selectors);
      // for each parsable node type, call the mapped parsing method
      forEach(elts, function(e) {
        parser[parser.map[e.localName]](e);
      });
      // upgrade all upgradeable static elements, anything dynamically
      // created should be caught by observer
      CustomElements.upgradeDocument(inDocument);
      // observe document for dom changes
      CustomElements.observeDocument(inDocument);
    }
  },
  parseLink: function(linkElt) {
    // imports
    if (isDocumentLink(linkElt)) {
      this.parseImport(linkElt);
    }
  },
  parseImport: function(linkElt) {
    if (linkElt.import) {
      parser.parse(linkElt.import);
    }
  }
};

function isDocumentLink(inElt) {
  return (inElt.localName === 'link'
      && inElt.getAttribute('rel') === IMPORT_LINK_TYPE);
}

var forEach = Array.prototype.forEach.call.bind(Array.prototype.forEach);

// exports

scope.parser = parser;
scope.IMPORT_LINK_TYPE = IMPORT_LINK_TYPE;

})(window.CustomElements);
(function(scope){

// bootstrap parsing
function bootstrap() {
  // parse document
  CustomElements.parser.parse(document);
  // one more pass before register is 'live'
  CustomElements.upgradeDocument(document);
  CustomElements.performedInitialDocumentUpgrade = true;
  // choose async
  var async = window.Platform && Platform.endOfMicrotask ?
    Platform.endOfMicrotask :
    setTimeout;
  async(function() {
    // set internal 'ready' flag, now document.registerElement will trigger 
    // synchronous upgrades
    CustomElements.ready = true;
    // capture blunt profiling data
    CustomElements.readyTime = Date.now();
    if (window.HTMLImports) {
      CustomElements.elapsed = CustomElements.readyTime - HTMLImports.readyTime;
    }
    // notify the system that we are bootstrapped
    document.dispatchEvent(
      new CustomEvent('WebComponentsReady', {bubbles: true})
    );
  });
}

// CustomEvent shim for IE
if (typeof window.CustomEvent !== 'function') {
  window.CustomEvent = function(inType) {
    var e = document.createEvent('HTMLEvents');
    e.initEvent(inType, true, true);
    return e;
  };
}

// When loading at readyState complete time (or via flag), boot custom elements
// immediately.
// If relevant, HTMLImports must already be loaded.
if (document.readyState === 'complete' || scope.flags.eager) {
  bootstrap();
// When loading at readyState interactive time, bootstrap only if HTMLImports
// are not pending. Also avoid IE as the semantics of this state are unreliable.
} else if (document.readyState === 'interactive' && !window.attachEvent &&
    (!window.HTMLImports || window.HTMLImports.ready)) {
  bootstrap();
// When loading at other readyStates, wait for the appropriate DOM event to
// bootstrap.
} else {
  var loadEvent = window.HTMLImports && !HTMLImports.ready
      ? 'HTMLImportsLoaded'
      : document.readyState == 'loading' ? 'DOMContentLoaded' : 'load';
  window.addEventListener(loadEvent, bootstrap);
}

})(window.CustomElements);

(function() {
// Patch to allow custom element and shadow dom to work together, from:
// https://github.com/Polymer/platform-dev/blob/60ece8c323c5d9325cbfdfd6e8cd180d4f38a3bc/src/patches-shadowdom-polyfill.js
// include .host reference
if (HTMLElement.prototype.createShadowRoot) {
  var originalCreateShadowRoot = HTMLElement.prototype.createShadowRoot;
  HTMLElement.prototype.createShadowRoot = function() {
    var root = originalCreateShadowRoot.call(this);
    root.host = this;
    CustomElements.watchShadow(this);
    return root;
  }
}


// Patch to allow custom elements and shadow dom to work together, from:
// https://github.com/Polymer/platform-dev/blob/2bb9c56d90f9ac19c2e65cdad368668aff514f14/src/patches-custom-elements.js
if (window.ShadowDOMPolyfill) {

  // ensure wrapped inputs for these functions
  var fns = ['upgradeAll', 'upgradeSubtree', 'observeDocument',
      'upgradeDocument'];

  // cache originals
  var original = {};
  fns.forEach(function(fn) {
    original[fn] = CustomElements[fn];
  });

  // override
  fns.forEach(function(fn) {
    CustomElements[fn] = function(inNode) {
      return original[fn](window.ShadowDOMPolyfill.wrapIfNeeded(inNode));
    };
  });

}

// Patch to make importNode work.
// https://github.com/Polymer/platform-dev/blob/64a92f273462f04a84abbe2f054294f2b62dbcd6/src/patches-mdv.js
if (window.CustomElements && !CustomElements.useNative) {
  var originalImportNode = Document.prototype.importNode;
  Document.prototype.importNode = function(node, deep) {
    var imported = originalImportNode.call(this, node, deep);
    CustomElements.upgradeAll(imported);
    return imported;
  }
}

})();