// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

part of $LIBRARYNAME;

class _ChildrenElementList extends ListBase<Element> {
  // Raw Element.
  final Element _element;
  final HtmlCollection _childElements;

  _ChildrenElementList._wrap(Element element)
    : _childElements = element.$dom_children,
      _element = element;

  bool contains(Element element) => _childElements.contains(element);


  bool get isEmpty {
    return _element.$dom_firstElementChild == null;
  }

  int get length {
    return _childElements.length;
  }

  Element operator [](int index) {
    return _childElements[index];
  }

  void operator []=(int index, Element value) {
    _element.$dom_replaceChild(value, _childElements[index]);
  }

  void set length(int newLength) {
    // TODO(jacobr): remove children when length is reduced.
    throw new UnsupportedError('Cannot resize element lists');
  }

  Element add(Element value) {
    _element.append(value);
    return value;
  }

  Iterator<Element> get iterator => toList().iterator;

  void addAll(Iterable<Element> iterable) {
    if (iterable is _ChildNodeListLazy) {
      iterable = new List.from(iterable);
    }

    for (Element element in iterable) {
      _element.append(element);
    }
  }

  void sort([int compare(Element a, Element b)]) {
    throw new UnsupportedError('Cannot sort element lists');
  }

  void removeWhere(bool test(Element element)) {
    _filter(test, false);
  }

  void retainWhere(bool test(Element element)) {
    _filter(test, true);
  }

  void _filter(bool test(var element), bool retainMatching) {
    var removed;
    if (retainMatching) {
      removed = _element.children.where((e) => !test(e));
    } else {
      removed = _element.children.where(test);
    }
    for (var e in removed) e.remove();
  }

  void setRange(int start, int end, Iterable<Element> iterable,
                [int skipCount = 0]) {
    throw new UnimplementedError();
  }

  void replaceRange(int start, int end, Iterable<Element> iterable) {
    throw new UnimplementedError();
  }

  void fillRange(int start, int end, [Element fillValue]) {
    throw new UnimplementedError();
  }

  bool remove(Object object) {
    if (object is Element) {
      Element element = object;
      if (identical(element.parentNode, _element)) {
        _element.$dom_removeChild(element);
        return true;
      }
    }
    return false;
  }

  void insert(int index, Element element) {
    if (index < 0 || index > length) {
      throw new RangeError.range(index, 0, length);
    }
    if (index == length) {
      _element.append(element);
    } else {
      _element.insertBefore(element, this[index]);
    }
  }

  void setAll(int index, Iterable<Element> iterable) {
    throw new UnimplementedError();
  }

  void clear() {
    // It is unclear if we want to keep non element nodes?
    _element.text = '';
  }

  Element removeAt(int index) {
    final result = this[index];
    if (result != null) {
      _element.$dom_removeChild(result);
    }
    return result;
  }

  Element removeLast() {
    final result = this.last;
    if (result != null) {
      _element.$dom_removeChild(result);
    }
    return result;
  }

  Element get first {
    Element result = _element.$dom_firstElementChild;
    if (result == null) throw new StateError("No elements");
    return result;
  }


  Element get last {
    Element result = _element.$dom_lastElementChild;
    if (result == null) throw new StateError("No elements");
    return result;
  }

  Element get single {
    if (length > 1) throw new StateError("More than one element");
    return first;
  }
}

/**
 * An immutable list containing HTML elements. This list contains some
 * additional methods for ease of CSS manipulation on a group of elements.
 */
abstract class ElementList<T extends Element> extends ListBase<T> {
  /**
   * The union of all CSS classes applied to the elements in this list.
   *
   * This set makes it easy to add, remove or toggle (add if not present, remove
   * if present) the classes applied to a collection of elements.
   *
   *     htmlList.classes.add('selected');
   *     htmlList.classes.toggle('isOnline');
   *     htmlList.classes.remove('selected');
   */
  CssClassSet get classes;

  /** Replace the classes with `value` for every element in this list. */
  set classes(Iterable<String> value);
}

// TODO(jacobr): this is an inefficient implementation but it is hard to see
// a better option given that we cannot quite force NodeList to be an
// ElementList as there are valid cases where a NodeList JavaScript object
// contains Node objects that are not Elements.
class _FrozenElementList<T extends Element> extends ListBase<T> implements ElementList {
  final List<Node> _nodeList;

  _FrozenElementList._wrap(this._nodeList);

  int get length => _nodeList.length;

  Element operator [](int index) => _nodeList[index];

  void operator []=(int index, Element value) {
    throw new UnsupportedError('Cannot modify list');
  }

  void set length(int newLength) {
    throw new UnsupportedError('Cannot modify list');
  }

  void sort([Comparator<Element> compare]) {
    throw new UnsupportedError('Cannot sort list');
  }

  Element get first => _nodeList.first;

  Element get last => _nodeList.last;

  Element get single => _nodeList.single;

  CssClassSet get classes => new _MultiElementCssClassSet(
      _nodeList.where((e) => e is Element));

  void set classes(Iterable<String> value) {
    _nodeList.where((e) => e is Element).forEach((e) => e.classes = value);
  }
}

/**
 * An abstract class, which all HTML elements extend.
 */
$(ANNOTATIONS)abstract class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {

  /**
   * Creates an HTML element from a valid fragment of HTML.
   *
   * The [html] fragment must represent valid HTML with a single element root,
   * which will be parsed and returned.
   *
   * Important: the contents of [html] should not contain any user-supplied
   * data. Without strict data validation it is impossible to prevent script
   * injection exploits.
   *
   * It is instead recommended that elements be constructed via [Element.tag]
   * and text be added via [text].
   *
   *     var element = new Element.html('<div class="foo">content</div>');
   */
  factory $CLASSNAME.html(String html) =>
      _$(CLASSNAME)FactoryProvider.createElement_html(html);

  /**
   * Creates the HTML element specified by the tag name.
   *
   * This is similar to [Document.createElement].
   * [tag] should be a valid HTML tag name. If [tag] is an unknown tag then
   * this will create an [UnknownElement].
   *
   *     var divElement = new Element.tag('div');
   *     print(divElement is DivElement); // 'true'
   *     var myElement = new Element.tag('unknownTag');
   *     print(myElement is UnknownElement); // 'true'
   *
   * For standard elements it is more preferable to use the type constructors:
   *     var element = new DivElement();
   *
   * See also:
   *
   * * [isTagSupported]
   */
  factory $CLASSNAME.tag(String tag) =>
      _$(CLASSNAME)FactoryProvider.createElement_tag(tag);

  /**
   * All attributes on this element.
   *
   * Any modifications to the attribute map will automatically be applied to
   * this element.
   *
   * This only includes attributes which are not in a namespace
   * (such as 'xlink:href'), additional attributes can be accessed via
   * [getNamespacedAttributes].
   */
  Map<String, String> get attributes => new _ElementAttributeMap(this);

  void set attributes(Map<String, String> value) {
    Map<String, String> attributes = this.attributes;
    attributes.clear();
    for (String key in value.keys) {
      attributes[key] = value[key];
    }
  }

  /**
   * List of the direct children of this element.
   *
   * This collection can be used to add and remove elements from the document.
   *
   *     var item = new DivElement();
   *     item.text = 'Something';
   *     document.body.children.add(item) // Item is now displayed on the page.
   *     for (var element in document.body.children) {
   *       element.style.background = 'red'; // Turns every child of body red.
   *     }
   */
  List<Element> get children => new _ChildrenElementList._wrap(this);

  void set children(List<Element> value) {
    // Copy list first since we don't want liveness during iteration.
    List copy = new List.from(value);
    var children = this.children;
    children.clear();
    children.addAll(copy);
  }

  /**
   * Finds all descendent elements of this element that match the specified
   * group of selectors.
   *
   * [selectors] should be a string using CSS selector syntax.
   *
   *     var items = element.query('.itemClassName');
   */
  ElementList queryAll(String selectors) =>
    new _FrozenElementList._wrap($dom_querySelectorAll(selectors));

  /**
   * The set of CSS classes applied to this element.
   *
   * This set makes it easy to add, remove or toggle the classes applied to
   * this element.
   *
   *     element.classes.add('selected');
   *     element.classes.toggle('isOnline');
   *     element.classes.remove('selected');
   */
  CssClassSet get classes => new _ElementCssClassSet(this);

  void set classes(Iterable<String> value) {
    CssClassSet classSet = classes;
    classSet.clear();
    classSet.addAll(value);
  }

  /**
   * Allows access to all custom data attributes (data-*) set on this element.
   *
   * The keys for the map must follow these rules:
   *
   * * The name must not begin with 'xml'.
   * * The name cannot contain a semi-colon (';').
   * * The name cannot contain any capital letters.
   *
   * Any keys from markup will be converted to camel-cased keys in the map.
   *
   * For example, HTML specified as:
   *
   *     <div data-my-random-value='value'></div>
   *
   * Would be accessed in Dart as:
   *
   *     var value = element.dataset['myRandomValue'];
   *
   * See also:
   *
   * * [Custom data attributes](http://www.w3.org/TR/html5/global-attributes.html#custom-data-attribute)
   */
  Map<String, String> get dataset =>
    new _DataAttributeMap(attributes);

  void set dataset(Map<String, String> value) {
    final data = this.dataset;
    data.clear();
    for (String key in value.keys) {
      data[key] = value[key];
    }
  }

  /**
   * Gets a map for manipulating the attributes of a particular namespace.
   *
   * This is primarily useful for SVG attributes such as xref:link.
   */
  Map<String, String> getNamespacedAttributes(String namespace) {
    return new _NamespacedAttributeMap(this, namespace);
  }

  /**
   * The set of all CSS values applied to this element, including inherited
   * and default values.
   *
   * The computedStyle contains values that are inherited from other
   * sources, such as parent elements or stylesheets. This differs from the
   * [style] property, which contains only the values specified directly on this
   * element.
   *
   * PseudoElement can be values such as `::after`, `::before`, `::marker`,
   * `::line-marker`.
   *
   * See also:
   *
   * * [CSS Inheritance and Cascade](http://docs.webplatform.org/wiki/tutorials/inheritance_and_cascade)
   * * [Pseudo-elements](http://docs.webplatform.org/wiki/css/selectors/pseudo-elements)
   */
  CssStyleDeclaration getComputedStyle([String pseudoElement]) {
    if (pseudoElement == null) {
      pseudoElement = '';
    }
    // TODO(jacobr): last param should be null, see b/5045788
    return window.$dom_getComputedStyle(this, pseudoElement);
  }

  /**
   * Gets the position of this element relative to the client area of the page.
   */
  Rect get client => new Rect(clientLeft, clientTop, clientWidth, clientHeight);

  /**
   * Gets the offset of this element relative to its offsetParent.
   */
  Rect get offset => new Rect(offsetLeft, offsetTop, offsetWidth, offsetHeight);

  /**
   * Adds the specified text as a text node after the last child of this
   * element.
   */
  void appendText(String text) {
    this.insertAdjacentText('beforeend', text);
  }

  /**
   * Parses the specified text as HTML and adds the resulting node after the
   * last child of this element.
   */
  void appendHtml(String text) {
    this.insertAdjacentHtml('beforeend', text);
  }

  /**
   * Checks to see if the tag name is supported by the current platform.
   *
   * The tag should be a valid HTML tag name.
   */
  static bool isTagSupported(String tag) {
    var e = _ElementFactoryProvider.createElement_tag(tag);
    return e is Element && !(e is UnknownElement);
  }

  /**
   * Called by the DOM when this element has been instantiated.
   */
  @Experimental
  void onCreated() {}

  // Hooks to support custom WebComponents.

$if DART2JS
  @Creates('Null')  // Set from Dart code; does not instantiate a native type.
$endif
  Element _xtag;

  /**
   * Experimental support for [web components][wc]. This field stores a
   * reference to the component implementation. It was inspired by Mozilla's
   * [x-tags][] project. Please note: in the future it may be possible to
   * `extend Element` from your class, in which case this field will be
   * deprecated.
   *
   * If xtag has not been set, it will simply return `this` [Element].
   *
   * [wc]: http://dvcs.w3.org/hg/webcomponents/raw-file/tip/explainer/index.html
   * [x-tags]: http://x-tags.org/
   */
  // Note: return type is `dynamic` for convenience to suppress warnings when
  // members of the component are used. The actual type is a subtype of Element.
  get xtag => _xtag != null ? _xtag : this;

  void set xtag(Element value) {
    _xtag = value;
  }

  @DomName('Element.localName')
  @DocsEditable
  String get localName => $dom_localName;

  @DomName('Element.namespaceUri')
  @DocsEditable
  String get namespaceUri => $dom_namespaceUri;

  String toString() => localName;

  /**
   * Scrolls this element into view.
   *
   * Only one of of the alignment options may be specified at a time.
   *
   * If no options are specified then this will attempt to scroll the minimum
   * amount needed to bring the element into view.
   *
   * Note that alignCenter is currently only supported on WebKit platforms. If
   * alignCenter is specified but not supported then this will fall back to
   * alignTop.
   *
   * See also:
   *
   * * [scrollIntoView](http://docs.webplatform.org/wiki/dom/methods/scrollIntoView)
   * * [scrollIntoViewIfNeeded](http://docs.webplatform.org/wiki/dom/methods/scrollIntoViewIfNeeded)
   */
  void scrollIntoView([ScrollAlignment alignment]) {
    var hasScrollIntoViewIfNeeded = false;
$if DART2JS
    hasScrollIntoViewIfNeeded =
        JS('bool', '!!(#.scrollIntoViewIfNeeded)', this);
$endif
    if (alignment == ScrollAlignment.TOP) {
      this.$dom_scrollIntoView(true);
    } else if (alignment == ScrollAlignment.BOTTOM) {
      this.$dom_scrollIntoView(false);
    } else if (hasScrollIntoViewIfNeeded) {
      if (alignment == ScrollAlignment.CENTER) {
        this.$dom_scrollIntoViewIfNeeded(true);
      } else {
        this.$dom_scrollIntoViewIfNeeded();
      }
    } else {
      this.$dom_scrollIntoView();
    }
  }

$if DART2JS
  @DomName('Element.mouseWheelEvent')
  static const EventStreamProvider<WheelEvent> mouseWheelEvent =
      const _CustomEventStreamProvider<WheelEvent>(
        Element._determineMouseWheelEventType);

  static String _determineMouseWheelEventType(EventTarget e) {
    if (JS('bool', '#.onwheel !== undefined', e)) {
      // W3C spec, and should be IE9+, but IE has a bug exposing onwheel.
      return 'wheel';
    } else if (JS('bool', '#.onmousewheel !== undefined', e)) {
      // Chrome & IE
      return 'mousewheel';
    } else {
      // Firefox
      return 'DOMMouseScroll';
    }
  }

  @DomName('Element.transitionEndEvent')
  static const EventStreamProvider<TransitionEvent> transitionEndEvent =
      const _CustomEventStreamProvider<TransitionEvent>(
        Element._determineTransitionEventType);

  static String _determineTransitionEventType(EventTarget e) {
    // Unfortunately the normal 'ontransitionend' style checks don't work here.
    if (Device.isWebKit) {
      return 'webkitTransitionEnd';
    } else if (Device.isOpera) {
      return 'oTransitionEnd';
    }
    return 'transitionend';
  }
  /**
   * Creates a text node and inserts it into the DOM at the specified location.
   *
   * To see the possible values for [where], read the doc for
   * [insertAdjacentHtml].
   *
   * See also:
   *
   * * [insertAdjacentHtml]
   */
  void insertAdjacentText(String where, String text) {
    if (JS('bool', '!!#.insertAdjacentText', this)) {
      _insertAdjacentText(where, text);
    } else {
      _insertAdjacentNode(where, new Text(text));
    }
  }

  @JSName('insertAdjacentText')
  void _insertAdjacentText(String where, String text) native;

  /**
   * Parses text as an HTML fragment and inserts it into the DOM at the
   * specified location.
   *
   * The [where] parameter indicates where to insert the HTML fragment:
   *
   * * 'beforeBegin': Immediately before this element.
   * * 'afterBegin': As the first child of this element.
   * * 'beforeEnd': As the last child of this element.
   * * 'afterEnd': Immediately after this element.
   *
   *     var html = '<div class="something">content</div>';
   *     // Inserts as the first child
   *     document.body.insertAdjacentHtml('afterBegin', html);
   *     var createdElement = document.body.children[0];
   *     print(createdElement.classes[0]); // Prints 'something'
   *
   * See also:
   *
   * * [insertAdjacentText]
   * * [insertAdjacentElement]
   */
  void insertAdjacentHtml(String where, String html) {
    if (JS('bool', '!!#.insertAdjacentHtml', this)) {
      _insertAdjacentHtml(where, html);
    } else {
      _insertAdjacentNode(where, new DocumentFragment.html(html));
    }
  }

  @JSName('insertAdjacentHTML')
  void _insertAdjacentHTML(String where, String text) native;

  /**
   * Inserts [element] into the DOM at the specified location.
   *
   * To see the possible values for [where], read the doc for
   * [insertAdjacentHtml].
   *
   * See also:
   *
   * * [insertAdjacentHtml]
   */
  Element insertAdjacentElement(String where, Element element) {
    if (JS('bool', '!!#.insertAdjacentElement', this)) {
      _insertAdjacentElement(where, element);
    } else {
      _insertAdjacentNode(where, element);
    }
    return element;
  }

  @JSName('insertAdjacentElement')
  void _insertAdjacentElement(String where, Element element) native;

  void _insertAdjacentNode(String where, Node node) {
    switch (where.toLowerCase()) {
      case 'beforebegin':
        this.parentNode.insertBefore(node, this);
        break;
      case 'afterbegin':
        var first = this.nodes.length > 0 ? this.nodes[0] : null;
        this.insertBefore(node, first);
        break;
      case 'beforeend':
        this.append(node);
        break;
      case 'afterend':
        this.parentNode.insertBefore(node, this.nextNode);
        break;
      default:
        throw new ArgumentError("Invalid position ${where}");
    }
  }

  /**
   * Checks if this element matches the CSS selectors.
   */
  @Experimental
  bool matches(String selectors) {
    if (JS('bool', '!!#.matches', this)) {
      return JS('bool', '#.matches(#)', this, selectors);
    } else if (JS('bool', '!!#.webkitMatchesSelector', this)) {
      return JS('bool', '#.webkitMatchesSelector(#)', this, selectors);
    } else if (JS('bool', '!!#.mozMatchesSelector', this)) {
      return JS('bool', '#.mozMatchesSelector(#)', this, selectors);
    } else if (JS('bool', '!!#.msMatchesSelector', this)) {
      return JS('bool', '#.msMatchesSelector(#)', this, selectors);
    }
    throw new UnsupportedError("Not supported on this platform");
  }
$else
$endif

$if DART2JS
  @Creates('Null') // Set from Dart code; does not instantiate a native type.
$endif
  Map<String, StreamSubscription> _attributeBindings;

  // TODO(jmesserly): I'm concerned about adding these to every element.
  // Conceptually all of these belong on TemplateElement. They are here to
  // support browsers that don't have <template> yet.
  // However even in the polyfill they're restricted to certain tags
  // (see [isTemplate]). So we can probably convert it to a (public) mixin, and
  // only mix it in to the elements that need it.
$if DART2JS
  @Creates('Null')  // Set from Dart code; does not instantiate a native type.
$endif
  var _model;

$if DART2JS
  @Creates('Null')  // Set from Dart code; does not instantiate a native type.
$endif
  _TemplateIterator _templateIterator;

$if DART2JS
  @Creates('Null')  // Set from Dart code; does not instantiate a native type.
$endif
  Element _templateInstanceRef;

  // Note: only used if `this is! TemplateElement`
$if DART2JS
  @Creates('Null')  // Set from Dart code; does not instantiate a native type.
$endif
  DocumentFragment _templateContent;

  bool _templateIsDecorated;

  // TODO(jmesserly): should path be optional, and default to empty path?
  // It is used that way in at least one path in JS TemplateElement tests
  // (see "BindImperative" test in original JS code).
  @Experimental
  void bind(String name, model, String path) {
    _bindElement(this, name, model, path);
  }

  // TODO(jmesserly): this is static to work around http://dartbug.com/10166
  // Similar issue for unbind/unbindAll below.
  static void _bindElement(Element self, String name, model, String path) {
    if (self._bindTemplate(name, model, path)) return;

    if (self._attributeBindings == null) {
      self._attributeBindings = new Map<String, StreamSubscription>();
    }

    self.xtag.attributes.remove(name);

    var changed;
    if (name.endsWith('?')) {
      name = name.substring(0, name.length - 1);

      changed = (value) {
        if (_Bindings._toBoolean(value)) {
          self.xtag.attributes[name] = '';
        } else {
          self.xtag.attributes.remove(name);
        }
      };
    } else {
      changed = (value) {
        // TODO(jmesserly): escape value if needed to protect against XSS.
        // See https://github.com/polymer-project/mdv/issues/58
        self.xtag.attributes[name] = value == null ? '' : '$value';
      };
    }

    self.unbind(name);

    self._attributeBindings[name] =
        new PathObserver(model, path).bindSync(changed);
  }

  @Experimental
  void unbind(String name) {
    _unbindElement(this, name);
  }

  static _unbindElement(Element self, String name) {
    if (self._unbindTemplate(name)) return;
    if (self._attributeBindings != null) {
      var binding = self._attributeBindings.remove(name);
      if (binding != null) binding.cancel();
    }
  }

  @Experimental
  void unbindAll() {
    _unbindAllElement(this);
  }

  static void _unbindAllElement(Element self) {
    self._unbindAllTemplate();

    if (self._attributeBindings != null) {
      for (var binding in self._attributeBindings.values) {
        binding.cancel();
      }
      self._attributeBindings = null;
    }
  }

  // TODO(jmesserly): unlike the JS polyfill, we can't mixin
  // HTMLTemplateElement at runtime into things that are semantically template
  // elements. So instead we implement it here with a runtime check.
  // If the bind succeeds, we return true, otherwise we return false and let
  // the normal Element.bind logic kick in.
  bool _bindTemplate(String name, model, String path) {
    if (isTemplate) {
      switch (name) {
        case 'bind':
        case 'repeat':
        case 'if':
          _ensureTemplate();
          if (_templateIterator == null) {
            _templateIterator = new _TemplateIterator(this);
          }
          _templateIterator.inputs.bind(name, model, path);
          return true;
      }
    }
    return false;
  }

  bool _unbindTemplate(String name) {
    if (isTemplate) {
      switch (name) {
        case 'bind':
        case 'repeat':
        case 'if':
          _ensureTemplate();
          if (_templateIterator != null) {
            _templateIterator.inputs.unbind(name);
          }
          return true;
      }
    }
    return false;
  }

  void _unbindAllTemplate() {
    if (isTemplate) {
      unbind('bind');
      unbind('repeat');
      unbind('if');
    }
  }

  /**
   * Gets the template this node refers to.
   * This is only supported if [isTemplate] is true.
   */
  @Experimental
  Element get ref {
    _ensureTemplate();

    Element ref = null;
    var refId = attributes['ref'];
    if (refId != null) {
      ref = document.getElementById(refId);
    }

    return ref != null ? ref : _templateInstanceRef;
  }

  /**
   * Gets the content of this template.
   * This is only supported if [isTemplate] is true.
   */
  @Experimental
  DocumentFragment get content {
    _ensureTemplate();
    return _templateContent;
  }

  /**
   * Creates an instance of the template.
   * This is only supported if [isTemplate] is true.
   */
  @Experimental
  DocumentFragment createInstance() {
    _ensureTemplate();

    var template = ref;
    if (template == null) template = this;

    var instance = _Bindings._createDeepCloneAndDecorateTemplates(
        template.content, attributes['syntax']);

    if (TemplateElement._instanceCreated != null) {
      TemplateElement._instanceCreated.add(instance);
    }
    return instance;
  }

  /**
   * The data model which is inherited through the tree.
   * This is only supported if [isTemplate] is true.
   *
   * Setting this will destructive propagate the value to all descendant nodes,
   * and reinstantiate all of the nodes expanded by this template.
   *
   * Currently this does not support propagation through Shadow DOMs.
   */
  @Experimental
  get model => _model;

  @Experimental
  void set model(value) {
    _ensureTemplate();

    var syntax = TemplateElement.syntax[attributes['syntax']];
    _model = value;
    _Bindings._addBindings(this, model, syntax);
  }

  // TODO(jmesserly): const set would be better
  static const _TABLE_TAGS = const {
    'caption': null,
    'col': null,
    'colgroup': null,
    'tbody': null,
    'td': null,
    'tfoot': null,
    'th': null,
    'thead': null,
    'tr': null,
  };

  bool get _isAttributeTemplate => attributes.containsKey('template') &&
      (localName == 'option' || _TABLE_TAGS.containsKey(localName));

  /**
   * Returns true if this node is a template.
   *
   * A node is a template if [tagName] is TEMPLATE, or the node has the
   * 'template' attribute and this tag supports attribute form for backwards
   * compatibility with existing HTML parsers. The nodes that can use attribute
   * form are table elments (THEAD, TBODY, TFOOT, TH, TR, TD, CAPTION, COLGROUP
   * and COL) and OPTION.
   */
  // TODO(jmesserly): this is not a public MDV API, but it seems like a useful
  // place to document which tags our polyfill considers to be templates.
  // Otherwise I'd be repeating it in several other places.
  // See if we can replace this with a TemplateMixin.
  @Experimental
  bool get isTemplate => tagName == 'TEMPLATE' || _isAttributeTemplate;

  void _ensureTemplate() {
    if (!isTemplate) {
      throw new UnsupportedError('$this is not a template.');
    }
    TemplateElement.decorate(this);
  }

$!MEMBERS
}


final _START_TAG_REGEXP = new RegExp('<(\\w+)');
class _ElementFactoryProvider {
  static const _CUSTOM_PARENT_TAG_MAP = const {
    'body' : 'html',
    'head' : 'html',
    'caption' : 'table',
    'td': 'tr',
    'th': 'tr',
    'colgroup': 'table',
    'col' : 'colgroup',
    'tr' : 'tbody',
    'tbody' : 'table',
    'tfoot' : 'table',
    'thead' : 'table',
    'track' : 'audio',
  };

  @DomName('Document.createElement')
  static Element createElement_html(String html) {
    // TODO(jacobr): this method can be made more robust and performant.
    // 1) Cache the dummy parent elements required to use innerHTML rather than
    //    creating them every call.
    // 2) Verify that the html does not contain leading or trailing text nodes.
    // 3) Verify that the html does not contain both <head> and <body> tags.
    // 4) Detatch the created element from its dummy parent.
    String parentTag = 'div';
    String tag;
    final match = _START_TAG_REGEXP.firstMatch(html);
    if (match != null) {
      tag = match.group(1).toLowerCase();
      if (Device.isIE && Element._TABLE_TAGS.containsKey(tag)) {
        return _createTableForIE(html, tag);
      }
      parentTag = _CUSTOM_PARENT_TAG_MAP[tag];
      if (parentTag == null) parentTag = 'div';
    }

    final temp = new Element.tag(parentTag);
    temp.innerHtml = html;

    Element element;
    if (temp.children.length == 1) {
      element = temp.children[0];
    } else if (parentTag == 'html' && temp.children.length == 2) {
      // In html5 the root <html> tag will always have a <body> and a <head>,
      // even though the inner html only contains one of them.
      element = temp.children[tag == 'head' ? 0 : 1];
    } else {
      _singleNode(temp.children);
    }
    element.remove();
    return element;
  }

  /**
   * IE table elements don't support innerHTML (even in standards mode).
   * Instead we use a div and inject the table element in the innerHtml string.
   * This technique works on other browsers too, but it's probably slower,
   * so we only use it when running on IE.
   *
   * See also innerHTML:
   * <http://msdn.microsoft.com/en-us/library/ie/ms533897(v=vs.85).aspx>
   * and Building Tables Dynamically:
   * <http://msdn.microsoft.com/en-us/library/ie/ms532998(v=vs.85).aspx>.
   */
  static Element _createTableForIE(String html, String tag) {
    var div = new Element.tag('div');
    div.innerHtml = '<table>$html</table>';
    var table = _singleNode(div.children);
    Element element;
    switch (tag) {
      case 'td':
      case 'th':
        TableRowElement row = _singleNode(table.rows);
        element = _singleNode(row.cells);
        break;
      case 'tr':
        element = _singleNode(table.rows);
        break;
      case 'tbody':
        element = _singleNode(table.tBodies);
        break;
      case 'thead':
        element = table.tHead;
        break;
      case 'tfoot':
        element = table.tFoot;
        break;
      case 'caption':
        element = table.caption;
        break;
      case 'colgroup':
        element = _getColgroup(table);
        break;
      case 'col':
        element = _singleNode(_getColgroup(table).children);
        break;
    }
    element.remove();
    return element;
  }

  static TableColElement _getColgroup(TableElement table) {
    // TODO(jmesserly): is there a better way to do this?
    return _singleNode(table.children.where((n) => n.tagName == 'COLGROUP')
        .toList());
  }

  static Node _singleNode(List<Node> list) {
    if (list.length == 1) return list[0];
    throw new ArgumentError('HTML had ${list.length} '
        'top level elements but 1 expected');
  }

  @DomName('Document.createElement')
$if DART2JS
  // Optimization to improve performance until the dart2js compiler inlines this
  // method.
  static dynamic createElement_tag(String tag) =>
      // Firefox may return a JS function for some types (Embed, Object).
      JS('Element|=Object', 'document.createElement(#)', tag);
$else
  static Element createElement_tag(String tag) =>
      document.$dom_createElement(tag);
$endif
}


/**
 * Options for Element.scrollIntoView.
 */
class ScrollAlignment {
  final _value;
  const ScrollAlignment._internal(this._value);
  toString() => 'ScrollAlignment.$_value';

  /// Attempt to align the element to the top of the scrollable area.
  static const TOP = const ScrollAlignment._internal('TOP');
  /// Attempt to center the element in the scrollable area.
  static const CENTER = const ScrollAlignment._internal('CENTER');
  /// Attempt to align the element to the bottom of the scrollable area.
  static const BOTTOM = const ScrollAlignment._internal('BOTTOM');
}