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html/lib/src/query_selector.dart

-/// Query selector implementation for our DOM.
-library html.src.query;
-
-import 'package:csslib/parser.dart' as css;
-import 'package:csslib/parser.dart' show TokenKind;
-import 'package:csslib/visitor.dart'; // the CSSOM
-import 'package:html/dom.dart';
-import 'package:html/src/constants.dart' show isWhitespaceCC;
-
-bool matches(Node node, String selector) =>
-    new SelectorEvaluator().matches(node, _parseSelectorList(selector));
-
-Element querySelector(Node node, String selector) =>
-    new SelectorEvaluator().querySelector(node, _parseSelectorList(selector));
-
-List<Element> querySelectorAll(Node node, String selector) {
-  var results = [];
-  new SelectorEvaluator().querySelectorAll(
-      node, _parseSelectorList(selector), results);
-  return results;
-}
-
-// http://dev.w3.org/csswg/selectors-4/#grouping
-SelectorGroup _parseSelectorList(String selector) {
-  var errors = [];
-  var group = css.parseSelectorGroup(selector, errors: errors);
-  if (group == null || errors.isNotEmpty) {
-    throw new FormatException("'$selector' is not a valid selector: $errors");
-  }
-  return group;
-}
-
-class SelectorEvaluator extends Visitor {
-  /// The current HTML element to match against.
-  Element _element;
-
-  bool matches(Element element, SelectorGroup selector) {
-    _element = element;
-    return visitSelectorGroup(selector);
-  }
-
-  Element querySelector(Node root, SelectorGroup selector) {
-    for (var node in root.nodes) {
-      if (node is! Element) continue;
-      if (matches(node, selector)) return node;
-      var result = querySelector(node, selector);
-      if (result != null) return result;
-    }
-    return null;
-  }
-
-  void querySelectorAll(
-      Node root, SelectorGroup selector, List<Element> results) {
-    for (var node in root.nodes) {
-      if (node is! Element) continue;
-      if (matches(node, selector)) results.add(node);
-      querySelectorAll(node, selector, results);
-    }
-  }
-
-  bool visitSelectorGroup(SelectorGroup group) =>
-      group.selectors.any(visitSelector);
-
-  bool visitSelector(Selector selector) {
-    var old = _element;
-    var result = true;
-
-    // Note: evaluate selectors right-to-left as it's more efficient.
-    int combinator = null;
-    for (var s in selector.simpleSelectorSequences.reversed) {
-      if (combinator == null) {
-        result = s.simpleSelector.visit(this);
-      } else if (combinator == TokenKind.COMBINATOR_DESCENDANT) {
-        // descendant combinator
-        // http://dev.w3.org/csswg/selectors-4/#descendant-combinators
-        do {
-          _element = _element.parent;
-        } while (_element != null && !s.simpleSelector.visit(this));
-
-        if (_element == null) result = false;
-      } else if (combinator == TokenKind.COMBINATOR_TILDE) {
-        // Following-sibling combinator
-        // http://dev.w3.org/csswg/selectors-4/#general-sibling-combinators
-        do {
-          _element = _element.previousElementSibling;
-        } while (_element != null && !s.simpleSelector.visit(this));
-
-        if (_element == null) result = false;
-      }
-
-      if (!result) break;
-
-      switch (s.combinator) {
-        case TokenKind.COMBINATOR_PLUS:
-          // Next-sibling combinator
-          // http://dev.w3.org/csswg/selectors-4/#adjacent-sibling-combinators
-          _element = _element.previousElementSibling;
-          break;
-        case TokenKind.COMBINATOR_GREATER:
-          // Child combinator
-          // http://dev.w3.org/csswg/selectors-4/#child-combinators
-          _element = _element.parent;
-          break;
-        case TokenKind.COMBINATOR_DESCENDANT:
-        case TokenKind.COMBINATOR_TILDE:
-          // We need to iterate through all siblings or parents.
-          // For now, just remember what the combinator was.
-          combinator = s.combinator;
-          break;
-        case TokenKind.COMBINATOR_NONE:
-          break;
-        default:
-          throw _unsupported(selector);
-      }
-
-      if (_element == null) {
-        result = false;
-        break;
-      }
-    }
-
-    _element = old;
-    return result;
-  }
-
-  _unimplemented(SimpleSelector selector) => new UnimplementedError(
-      "'$selector' selector of type "
-      "${selector.runtimeType} is not implemented");
-
-  _unsupported(selector) =>
-      new FormatException("'$selector' is not a valid selector");
-
-  bool visitPseudoClassSelector(PseudoClassSelector selector) {
-    switch (selector.name) {
-      // http://dev.w3.org/csswg/selectors-4/#structural-pseudos
-
-      // http://dev.w3.org/csswg/selectors-4/#the-root-pseudo
-      case 'root':
-        // TODO(jmesserly): fix when we have a .ownerDocument pointer
-        // return _element == _element.ownerDocument.rootElement;
-        return _element.localName == 'html' && _element.parentNode == null;
-
-      // http://dev.w3.org/csswg/selectors-4/#the-empty-pseudo
-      case 'empty':
-        return _element.nodes
-            .any((n) => !(n is Element || n is Text && n.text.isNotEmpty));
-
-      // http://dev.w3.org/csswg/selectors-4/#the-blank-pseudo
-      case 'blank':
-        return _element.nodes.any((n) => !(n is Element ||
-            n is Text && n.text.runes.any((r) => !isWhitespaceCC(r))));
-
-      // http://dev.w3.org/csswg/selectors-4/#the-first-child-pseudo
-      case 'first-child':
-        return _element.previousElementSibling == null;
-
-      // http://dev.w3.org/csswg/selectors-4/#the-last-child-pseudo
-      case 'last-child':
-        return _element.nextElementSibling == null;
-
-      // http://dev.w3.org/csswg/selectors-4/#the-only-child-pseudo
-      case 'only-child':
-        return _element.previousElementSibling == null &&
-            _element.nextElementSibling == null;
-
-      // http://dev.w3.org/csswg/selectors-4/#link
-      case 'link':
-        return _element.attributes['href'] != null;
-
-      case 'visited':
-        // Always return false since we aren't a browser. This is allowed per:
-        // http://dev.w3.org/csswg/selectors-4/#visited-pseudo
-        return false;
-    }
-
-    // :before, :after, :first-letter/line can't match DOM elements.
-    if (_isLegacyPsuedoClass(selector.name)) return false;
-
-    throw _unimplemented(selector);
-  }
-
-  bool visitPseudoElementSelector(PseudoElementSelector selector) {
-    // :before, :after, :first-letter/line can't match DOM elements.
-    if (_isLegacyPsuedoClass(selector.name)) return false;
-
-    throw _unimplemented(selector);
-  }
-
-  static bool _isLegacyPsuedoClass(String name) {
-    switch (name) {
-      case 'before':
-      case 'after':
-      case 'first-line':
-      case 'first-letter':
-        return true;
-      default:
-        return false;
-    }
-  }
-
-  bool visitPseudoElementFunctionSelector(PseudoElementFunctionSelector s) =>
-      throw _unimplemented(s);
-
-  bool visitPseudoClassFunctionSelector(PseudoClassFunctionSelector selector) {
-    switch (selector.name) {
-      // http://dev.w3.org/csswg/selectors-4/#child-index
-
-      // http://dev.w3.org/csswg/selectors-4/#the-nth-child-pseudo
-      case 'nth-child':
-        // TODO(jmesserly): support An+B syntax too.
-        var exprs = selector.expression.expressions;
-        if (exprs.length == 1 && exprs[0] is LiteralTerm) {
-          LiteralTerm literal = exprs[0];
-          var parent = _element.parentNode;
-          return parent != null &&
-              literal.value > 0 &&
-              parent.nodes.indexOf(_element) == literal.value;
-        }
-        break;
-
-      // http://dev.w3.org/csswg/selectors-4/#the-lang-pseudo
-      case 'lang':
-        // TODO(jmesserly): shouldn't need to get the raw text here, but csslib
-        // gets confused by the "-" in the expression, such as in "es-AR".
-        var toMatch = selector.expression.span.text;
-        var lang = _getInheritedLanguage(_element);
-        // TODO(jmesserly): implement wildcards in level 4
-        return lang != null && lang.startsWith(toMatch);
-    }
-    throw _unimplemented(selector);
-  }
-
-  static String _getInheritedLanguage(Node node) {
-    while (node != null) {
-      var lang = node.attributes['lang'];
-      if (lang != null) return lang;
-      node = node.parent;
-    }
-    return null;
-  }
-
-  bool visitNamespaceSelector(NamespaceSelector selector) {
-    // Match element tag name
-    if (!selector.nameAsSimpleSelector.visit(this)) return false;
-
-    if (selector.isNamespaceWildcard) return true;
-
-    if (selector.namespace == '') return _element.namespaceUri == null;
-
-    throw _unimplemented(selector);
-  }
-
-  bool visitElementSelector(ElementSelector selector) =>
-      selector.isWildcard || _element.localName == selector.name.toLowerCase();
-
-  bool visitIdSelector(IdSelector selector) => _element.id == selector.name;
-
-  bool visitClassSelector(ClassSelector selector) =>
-      _element.classes.contains(selector.name);
-
-  // TODO(jmesserly): negation should support any selectors in level 4,
-  // not just simple selectors.
-  // http://dev.w3.org/csswg/selectors-4/#negation
-  bool visitNegationSelector(NegationSelector selector) =>
-      !selector.negationArg.visit(this);
-
-  bool visitAttributeSelector(AttributeSelector selector) {
-    // Match name first
-    var value = _element.attributes[selector.name.toLowerCase()];
-    if (value == null) return false;
-
-    if (selector.operatorKind == TokenKind.NO_MATCH) return true;
-
-    var select = '${selector.value}';
-    switch (selector.operatorKind) {
-      case TokenKind.EQUALS:
-        return value == select;
-      case TokenKind.INCLUDES:
-        return value.split(' ').any((v) => v.isNotEmpty && v == select);
-      case TokenKind.DASH_MATCH:
-        return value.startsWith(select) &&
-            (value.length == select.length || value[select.length] == '-');
-      case TokenKind.PREFIX_MATCH:
-        return value.startsWith(select);
-      case TokenKind.SUFFIX_MATCH:
-        return value.endsWith(select);
-      case TokenKind.SUBSTRING_MATCH:
-        return value.contains(select);
-      default:
-        throw _unsupported(selector);
-    }
-  }
-}