New CSS parser written in Dart to replace pyparser

utils/css/tree.dart

 // Copyright (c) 2011, 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.
 // Generated by scripts/tree_gen.py.
 
 /////////////////////////////////////////////////////////////////////////
 // CSS specific types:
 /////////////////////////////////////////////////////////////////////////
 
 
 class Identifier extends lang.Node {
   String name;
 
-  Identifier(this.name, lang.SourceSpan span): super(span) {}
+  Identifier(this.name, lang.SourceSpan span): super(span);
 
   visit(TreeVisitor visitor) => visitor.visitIdentifier(this);
 
   String toString() => name;
 }
 
 class Wildcard extends lang.Node {
   Wildcard(lang.SourceSpan span): super(span);
 
   visit(TreeVisitor visitor) => visitor.visitWildcard(this);
 
   String toString() => '*';
 }
 
+// /*  ....   */
+class Comment extends lang.Node {
+  String comment;
+
+  Comment(this.comment, lang.SourceSpan span): super(span);
+
+  visit(TreeVisitor visitor) => visitor.visitComment(this);
+
+  String toString() => '/* ${comment} */';
+}
+
+// CDO/CDC (Comment Definition Open <!-- and Comment Definition Close -->).
+class CommentDefinition extends Comment {
+  CommentDefinition(String comment, lang.SourceSpan span): super(comment, span);
+
+  visit(TreeVisitor visitor) => visitor.visitCommentDefinition(this);
+
+  String toString() => '<!-- ${comment} -->';
+}
+
 class SelectorGroup extends lang.Node {
-  // List of SimpleSelector(s) list contain any mix SimpleSelector or
-  // SimpleSlectorName (or class derived from SimpleSelectorName e.g.,
-  // IdSelector, ClassSelector, ElementSelector, PseudoClassSelector,
-  // PseudoElementSelector, NotSelector, or Attribute
-  List<SimpleSelector> selectors;
+  List<Selector> _selectors;
 
-  SelectorGroup(this.selectors, lang.SourceSpan span): super(span);
+  SelectorGroup(this._selectors, lang.SourceSpan span): super(span);
+
+  List<Selector> get selectors() => _selectors;
 
   visit(TreeVisitor visitor) => visitor.visitSelectorGroup(this);
 
   String toString() {
     StringBuffer buff = new StringBuffer();
-    for (selector in selectors) {
-      if (selector.isCombinatorDescendant()) {
-        buff.add(' ');        
-      } else if (selector.isCombinatorPlus()) {
-        buff.add(' + ');
-      } else if (selector.isCombinatorGreater()) {
-        buff.add(' > ');
-      } else if (selector.isCombinatorTilde()) {
-        buff.add(' ~ ');
+    int idx = 0;
+    for (var selector in _selectors) {
+      if (idx++ > 0) {
+        buff.add(', ');
       }
       buff.add(selector.toString());
     }
     return buff.toString();
   }
 
   /** A multiline string showing the node and its children. */
   String toDebugString() {
     var to = new lang.TreeOutput();
     var tp = new TreePrinter(to);
     this.visit(tp);
     return to.buf.toString();
   }
 }
 
+class Selector extends lang.Node {
+  List<SimpleSelectorSequence> _simpleSelectorSequences;
+
+  Selector(this._simpleSelectorSequences, lang.SourceSpan span) : super(span);
+
+  List<SimpleSelectorSequence> get simpleSelectorSequences() =>
+      _simpleSelectorSequences;
+
+  add(SimpleSelectorSequence seq) => _simpleSelectorSequences.add(seq);
+
+  List<SimpleSelectorSequence> get simpleSelectorSquences() =>
+      _simpleSelectorSequences;
+
+  int get length() => _simpleSelectorSequences.length;
+
+  String toString() {
+    StringBuffer buff = new StringBuffer();
+    for (_simpleSelectorSequence in _simpleSelectorSequences) {
+      buff.add(_simpleSelectorSequence.toString());
+    }
+    return buff.toString();
+  }
+
+  visit(TreeVisitor visitor) => visitor.visitSelector(this);
+}
+
+class SimpleSelectorSequence extends lang.Node {
+  int _combinator;              // +, >, ~, NONE
+  SimpleSelector _selector;
+
+  SimpleSelectorSequence(this._selector, lang.SourceSpan span,
+      [this._combinator = TokenKind.COMBINATOR_NONE]) : super(span);
+
+  get simpleSelector() => _selector;
+
+  bool isCombinatorNone() => _combinator == TokenKind.COMBINATOR_NONE;
+  bool isCombinatorPlus() => _combinator == TokenKind.COMBINATOR_PLUS;
+  bool isCombinatorGreater() => _combinator == TokenKind.COMBINATOR_GREATER;
+  bool isCombinatorTilde() => _combinator == TokenKind.COMBINATOR_TILDE;
+  bool isCombinatorDescendant() =>
+      _combinator == TokenKind.COMBINATOR_DESCENDANT;
+
+  String _combinatorToString() =>
+      isCombinatorDescendant() ? ' ' :
+      isCombinatorPlus() ? '+' :
+      isCombinatorGreater() ? '>' :
+      isCombinatorTilde() ? '~' : '';
+
+  visit(TreeVisitor visitor) => visitor.visitSimpleSelectorSequence(this);
+
+  String toString() => _combinatorToString() + _selector.toString();
+}
+
 /* All other selectors (element, #id, .class, attribute, pseudo, negation,
  * namespace, *) are derived from this selector.
  */
 class SimpleSelector extends lang.Node {
-  int _combinator;      // +, >, ~ or descendant (space), and NONE
   var _name;
 
-  SimpleSelector(this._name, lang.SourceSpan span,
-      [this._combinator = TokenKind.COMBINATOR_NONE]) : super(span);
+  SimpleSelector(this._name, lang.SourceSpan span) : super(span);
 
   // Name can be an Identifier or WildCard we'll return either the name or '*'.
   String get name() => isWildcard() ? '*' : _name.name;
 
   bool isWildcard() => _name is Wildcard;
 
-  // TODO(terry): Kind of hacky to reset combinator to NONE
-  void resetCombinatorNone() {
-    assert(isCombinatorDescendant());
-    _combinator = TokenKind.COMBINATOR_NONE;
-  }
-
-  bool isCombinatorNone() => _combinator == TokenKind.COMBINATOR_NONE;
-  bool isCombinatorDescendant() =>
-      _combinator == TokenKind.COMBINATOR_DESCENDANT;
-  bool isCombinatorPlus() => _combinator == TokenKind.COMBINATOR_PLUS;
-  bool isCombinatorGreater() => _combinator == TokenKind.COMBINATOR_GREATER;
-  bool isCombinatorTilde() => _combinator == TokenKind.COMBINATOR_TILDE;
-
   visit(TreeVisitor visitor) => visitor.visitSimpleSelector(this);
 
   String toString() => name;
 }
 
 // element name
 class ElementSelector extends SimpleSelector {
-  ElementSelector(var name, lang.SourceSpan span,
-      [int combinator = TokenKind.COMBINATOR_NONE]) :
-      super(name, span, combinator);
+  ElementSelector(var name, lang.SourceSpan span) : super(name, span);
 
   visit(TreeVisitor visitor) => visitor.visitElementSelector(this);
 
   String toString() => "$name";
 
   /** A multiline string showing the node and its children. */
   String toDebugString() {
     var to = new lang.TreeOutput();
     var tp = new TreePrinter(to);
     this.visit(tp);
     return to.buf.toString();
   }
 }
 
 // namespace|element
 class NamespaceSelector extends SimpleSelector {
   var _namespace;           // null, Wildcard or Identifier
 
-  NamespaceSelector(this._namespace, var name, lang.SourceSpan span,
-      [int combinator = TokenKind.COMBINATOR_NONE]) :
-      super(name, span, combinator);
+  NamespaceSelector(this._namespace, var name, lang.SourceSpan span) :
+      super(name, span);
 
   String get namespace() => _namespace is Wildcard ? '*' : _namespace.name;
 
   bool isNamespaceWildcard() => _namespace is Wildcard;
 
   SimpleSelector get nameAsSimpleSelector() => _name;
 
   visit(TreeVisitor visitor) => visitor.visitNamespaceSelector(this);
 
   String toString() => "$namespace|$nameAsSimpleSelector";
 }
 
+// [attr op value]
+class AttributeSelector extends SimpleSelector {
+  int _op;
+  var _value;
+
+  AttributeSelector(Identifier name, this._op, this._value,
+      lang.SourceSpan span) : super(name, span);
+
+  String matchOperator() {
+    switch (_op) {
+    case TokenKind.EQUALS:
+      return '=';
+    case TokenKind.INCLUDES:
+      return '~=';
+    case TokenKind.DASH_MATCH:
+      return '|=';
+    case TokenKind.PREFIX_MATCH:
+      return '^=';
+    case TokenKind.SUFFIX_MATCH:
+      return '\$=';
+    case TokenKind.SUBSTRING_MATCH:
+      return '*=';
+    }
+  }
+
+  // Return the TokenKind for operator used by visitAttributeSelector.
+  String matchOperatorAsTokenString() {
+    switch (_op) {
+    case TokenKind.EQUALS:
+      return 'EQUALS';
+    case TokenKind.INCLUDES:
+      return 'INCLUDES';
+    case TokenKind.DASH_MATCH:
+      return 'DASH_MATCH';
+    case TokenKind.PREFIX_MATCH:
+      return 'PREFIX_MATCH';
+    case TokenKind.SUFFIX_MATCH:
+      return 'SUFFIX_MATCH';
+    case TokenKind.SUBSTRING_MATCH:
+      return 'SUBSTRING_MATCH';
+    }
+  }
+ 
+  String valueToString() {
+    if (_value is Identifier) {
+      return _value.name;
+    } else {
+      return '"${_value}"';
+    }
+  }
+
+  visit(TreeVisitor visitor) => visitor.visitAttributeSelector(this);
+
+  String toString() => "[${name} ${matchOperator()} ${valueToString()}]";
+}
+
 // #id
 class IdSelector extends SimpleSelector {
-  IdSelector(Identifier name, lang.SourceSpan span,
-    [int combinator = TokenKind.COMBINATOR_NONE]) :
-    super(name, span, combinator);
+  IdSelector(Identifier name, lang.SourceSpan span) : super(name, span);
 
   visit(TreeVisitor visitor) => visitor.visitIdSelector(this);
 
   String toString() => "#$name";
 }
 
 // .class
 class ClassSelector extends SimpleSelector {
-  ClassSelector(Identifier name, lang.SourceSpan span,
-    [int combinator = TokenKind.COMBINATOR_NONE]) :
-    super(name, span, combinator);
+  ClassSelector(Identifier name, lang.SourceSpan span) : super(name, span);
 
   visit(TreeVisitor visitor) => visitor.visitClassSelector(this);
 
   String toString() => ".$name";
 }
 
 // :pseudoClass
 class PseudoClassSelector extends SimpleSelector {
-  PseudoClassSelector(Identifier name, lang.SourceSpan span,
-      [int combinator = TokenKind.COMBINATOR_NONE]) :
-      super(name, span, combinator);
+  PseudoClassSelector(Identifier name, lang.SourceSpan span) :
+      super(name, span);
 
   visit(TreeVisitor visitor) => visitor.visitPseudoClassSelector(this);
 
   String toString() => ":$name";
 }
 
 // ::pseudoElement
 class PseudoElementSelector extends SimpleSelector {
-  PseudoElementSelector(Identifier name, lang.SourceSpan span,
-      [int combinator = TokenKind.COMBINATOR_NONE]) :
-      super(name, span, combinator);
+  PseudoElementSelector(Identifier name, lang.SourceSpan span) :
+      super(name, span);
 
   visit(TreeVisitor visitor) => visitor.visitPseudoElementSelector(this);
 
   String toString() => "::$name";
 }
 
 // TODO(terry): Implement
 // NOT
 class NotSelector extends SimpleSelector {
-  NotSelector(String name, lang.SourceSpan span,
-    [lang.Token combinator = TokenKind.COMBINATOR_NONE]) :
-    super(name, span, combinator);
+  NotSelector(String name, lang.SourceSpan span) : super(name, span);
 
   visit(TreeVisitor visitor) => visitor.visitNotSelector(this);
 }
 
-// TODO(terry): Implement
-// [attribute]
-class Attribute extends lang.Node {
-  var name;         // NamespaceSelector or SimpleSelector
-  int matchType;    // ~=, |=, ^=, $=, *=, =
-  String value;
+class Stylesheet extends lang.Node {
+  // Contains charset, ruleset, directives (media, page, etc.)
+  List<lang.Node> _topLevels;
+
+  Stylesheet(this._topLevels, lang.SourceSpan span) : super(span) {
+    for (var node in _topLevels) {
+      assert(node is TopLevelProduction || node is Directive);
+    }
+  }
+
+  visit(TreeVisitor visitor) => visitor.visitStylesheet(this);
+
+  List<lang.Node> get topLevels() => _topLevels;
+  
+  String toString() {
+    StringBuffer buff = new StringBuffer();
+    for (var topLevel in _topLevels) {
+      buff.add(topLevel.toString());
+    }
+    return buff.toString();
+  }
+
+  /** A multiline string showing the node and its children. */
+  String toDebugString() {
+    var to = new lang.TreeOutput();
+    var tp = new TreePrinter(to);
+    this.visit(tp);
+    return to.buf.toString();
+  }
+}
+
+class TopLevelProduction extends lang.Node {
+  TopLevelProduction(lang.SourceSpan span) : super(span);
+
+  visit(TreeVisitor visitor) => visitor.visitTopLevelProduction(this);
+
+  String toString() => "TopLevelProduction";
+}
+
+class RuleSet extends TopLevelProduction {
+  SelectorGroup _selectorGroup;
+  DeclarationGroup _declarationGroup;
+
+  RuleSet(this._selectorGroup, this._declarationGroup, lang.SourceSpan span) :
+      super(span);
+
+  SelectorGroup get selectorGroup() => _selectorGroup;
+  DeclarationGroup get declarationGroup() => _declarationGroup;
+
+  visit(TreeVisitor visitor) => visitor.visitRuleSet(this);
+
+  String toString() =>
+      "\n${_selectorGroup.toString()} {\n" +
+        "${_declarationGroup.toString()}}\n";
+}
+
+class Directive extends lang.Node {
+  Directive(lang.SourceSpan span) : super(span);
+
+  String toString() => "Directive";
+
+  bool get isBuiltIn() => true;       // Known CSS directive?
+  bool get isExtension() => false;    // SCSS extension?
+
+  visit(TreeVisitor visitor) => visitor.visitDirective(this);
+}
+
+class ImportDirective extends Directive {
+  String _import;
+  List<String> _media;
+
+  ImportDirective(this._import, this._media, lang.SourceSpan span) :
+      super(span);
+
+  visit(TreeVisitor visitor) => visitor.visitImportDirective(this);
+
+  String toString() {
+    StringBuffer buff = new StringBuffer();
+
+    buff.add('@import url(${_import})');
+
+    int idx = 0;
+    for (var medium in _media) {
+      buff.add(idx++ == 0 ? ' $medium' : ',$medium');
+    }
+    buff.add('\n');
+
+    return buff.toString();
+  }
+}
+
+class MediaDirective extends Directive {
+  List<String> _media;
+  RuleSet _ruleset;

[nweiz, 2012/01/04 19:05:41]

Shouldn't this be a list of RuleSets? 

+
+  MediaDirective(this._media, this._ruleset, lang.SourceSpan span) :
+      super(span);
+
+  visit(TreeVisitor visitor) => visitor.visitMediaDirective(this);
+
+  String toString() {
+    StringBuffer buff = new StringBuffer();
+
+    buff.add('@media');
+    int idx = 0;
+    for (var medium in _media) {
+      buff.add(idx++ == 0 ? ' $medium' : ',$medium');
+    }
+    buff.add(' {\n');
+    buff.add(_ruleset.toString());
+    buff.add('\n\}\n');
+
+    return buff.toString();
+  }
+}
+
+class PageDirective extends Directive {
+  String _pseudoPage;
+  DeclarationGroup _decls;
+
+  PageDirective(this._pseudoPage, this._decls, lang.SourceSpan span) :
+    super(span);
+
+  visit(TreeVisitor visitor) => visitor.visitPageDirective(this);
+
+  // @page : pseudoPage {
+  //    decls
+  // }
+  String toString() {
+    StringBuffer buff = new StringBuffer();
+
+    buff.add('@page ');
+    if (_pseudoPage != null) {
+      buff.add(': ${_pseudoPage} ');
+    }
+    buff.add('{\n${_decls.toString()}\n}\n');
+
+    return buff.toString();
+  }
+}
+
+class KeyFrameDirective extends Directive {
+  var _name;
+  List<KeyFrameBlock> _blocks;
+
+  KeyFrameDirective(this._name, lang.SourceSpan span) :
+      _blocks = [], super(span);
+
+  add(KeyFrameBlock block) {
+    _blocks.add(block);
+  }
+
+  String get name() => _name;
+
+  visit(TreeVisitor visitor) => visitor.visitKeyFrameDirective(this);
+
+  String toString() {
+    StringBuffer buff = new StringBuffer();
+    buff.add('@-webkit-keyframes ${_name} {\n');
+    for (var block in _blocks) {
+      buff.add(block.toString());
+    }
+    buff.add('}\n');
+    return buff.toString();
+  }
+}
+
+class KeyFrameBlock extends lang.Expression {
+  Expressions _blockSelectors;
+  DeclarationGroup _declarations;
+
+  KeyFrameBlock(this._blockSelectors, this._declarations, lang.SourceSpan span):
+      super(span);
+
+  visit(TreeVisitor visitor) => visitor.visitKeyFrameBlock(this);
+
+  String toString() {
+    StringBuffer buff = new StringBuffer();
+    buff.add('  ${_blockSelectors.toString()} {\n');
+    buff.add(_declarations.toString());
+    buff.add('  }\n');
+    return buff.toString();
+  }
+}
+
+// TODO(terry): TBD
+class FontFaceDirective extends Directive {
+  List<Declaration> _declarations;

[nweiz, 2012/01/04 19:05:41]

Shouldn't this be a DeclarationGroup?

+
+  FontFaceDirective(this._declarations, lang.SourceSpan span) : super(span);
+
+  visit(TreeVisitor visitor) => visitor.visitFontFaceDirective(this);
+
+  String toString() {
+    return "TO BE DONE";
+  }
+}
+
+class IncludeDirective extends Directive {
+  String _include;
+  Stylesheet _stylesheet;
+
+  IncludeDirective(this._include, this._stylesheet, lang.SourceSpan span) :
+      super(span);
+
+  visit(TreeVisitor visitor) => visitor.visitIncludeDirective(this);
+
+  bool get isBuiltIn() => false;
+  bool get isExtension() => true;
+
+  Stylesheet get styleSheet() => _stylesheet;
+
+  String toString() {
+    StringBuffer buff = new StringBuffer();
+    buff.add('/****** @include ${_include} ******/\n');
+    buff.add(_stylesheet != null ? _stylesheet.toString() : '// <EMPTY>');
+    buff.add('/****** End of ${_include} ******/\n\n');
+    return buff.toString();
+  }
+}
+
+class StyletDirective extends Directive {
+  String _dartClassName;
+  List<RuleSet> _rulesets;
+
+  StyletDirective(this._dartClassName, this._rulesets, lang.SourceSpan span) :
+      super(span);
+
+  bool get isBuiltIn() => false;
+  bool get isExtension() => true;
+
+  String get dartClassName() => _dartClassName;
+  List<RuleSet> get rulesets() => _rulesets;
+
+  visit(TreeVisitor visitor) => visitor.visitStyletDirective(this);
+
+  // TODO(terry): Output Dart class
+  String toString() => '/* @stylet export as ${_dartClassName} */\n';
+}
+
+class Declaration extends lang.Node {
+  Identifier _property;
+  lang.Expression _expression;
+  bool _important;
+
+  Declaration(this._property, this._expression, lang.SourceSpan span) :
+      _important = false, super(span);
+
+  String get property() => _property.name;
+  lang.Expression get expression() => _expression;
+
+  bool get important() => _important;
+  set important(bool value) => _important = value;
+  String importantAsString() => _important ? ' !important' : '';
+
+  visit(TreeVisitor visitor) => visitor.visitDeclaration(this);
+
+  String toString() =>
+      "${_property.name}: ${_expression.toString()}${importantAsString()}";
+}
+
+class DeclarationGroup extends lang.Node {
+  List<Declaration> _declarations;
+
+  DeclarationGroup(this._declarations, lang.SourceSpan span) : super(span);
+
+  List<Declaration> get declarations() => _declarations;
+
+  visit(TreeVisitor visitor) => visitor.visitDeclarationGroup(this);
+
+  String toString() {
+    StringBuffer buff = new StringBuffer();
+    int idx = 0;
+    for (var declaration in _declarations) {
+      buff.add("  ${declaration.toString()};\n");
+    }
+    return buff.toString();
+  }
+}
+
+class OperatorSlash extends lang.Expression {
+  OperatorSlash(lang.SourceSpan span) : super(span);
+
+  visit(TreeVisitor visitor) => visitor.visitOperatorSlash(this);
+
+  String toString() => ' /';
+}
+
+class OperatorComma extends lang.Expression {
+  OperatorComma(lang.SourceSpan span) : super(span);
+
+  visit(TreeVisitor visitor) => visitor.visitOperatorComma(this);
+
+  String toString() => ',';
+}
+
+class LiteralTerm extends lang.Expression {
+  var _value;
+  String _text;
+
+  LiteralTerm(this._value, this._text, lang.SourceSpan span) : super(span);
+
+  get value() => _value;
+  String get text() => _text;
+
+  visit(TreeVisitor visitor) => visitor.visitLiteralTerm(this);
+
+  String toString() => _text;
+}
+
+class NumberTerm extends LiteralTerm {
+  NumberTerm(var value, String t, lang.SourceSpan span) : super(value, t, span);
+
+  visit(TreeVisitor visitor) => visitor.visitNumberTerm(this);
+}
+
+class UnitTerm extends LiteralTerm {
+  int _unit;
+
+  UnitTerm(var value, String t, lang.SourceSpan span, this._unit) :
+      super(value, t, span);
+
+  int get unit() => _unit;
+
+  visit(TreeVisitor visitor) => visitor.visitUnitTerm(this);
+
+  String toString() => '${text}${unitToString()}';
+  String unitToString() => TokenKind.unitToString(_unit);
+}
+
+class LengthTerm extends UnitTerm {
+  LengthTerm(var value, String t, lang.SourceSpan span,
+      [int unit = TokenKind.UNIT_LENGTH_PX]) : super(value, t, span, unit) {
+    assert(this._unit == TokenKind.UNIT_LENGTH_PX ||
+        this._unit == TokenKind.UNIT_LENGTH_CM ||
+        this._unit == TokenKind.UNIT_LENGTH_MM ||
+        this._unit == TokenKind.UNIT_LENGTH_IN ||
+        this._unit == TokenKind.UNIT_LENGTH_PT ||
+        this._unit == TokenKind.UNIT_LENGTH_PC);
+  }
+
+  visit(TreeVisitor visitor) => visitor.visitLengthTerm(this);
+}
+
+class PercentageTerm extends LiteralTerm {
+  PercentageTerm(var value, String t, lang.SourceSpan span) :
+      super(value, t, span);
+
+  visit(TreeVisitor visitor) => visitor.visitPercentageTerm(this);
+
+  String toString() => '${text}%';
+
+}
+
+class EmTerm extends LiteralTerm {
+  EmTerm(var value, String t, lang.SourceSpan span) :
+      super(value, t, span);
+
+  visit(TreeVisitor visitor) => visitor.visitEmTerm(this);
+
+  String toString() => '${text}em';
+}
+
+class ExTerm extends LiteralTerm {
+  ExTerm(var value, String t, lang.SourceSpan span) :
+      super(value, t, span);
+
+  visit(TreeVisitor visitor) => visitor.visitExTerm(this);
+
+  String toString() => '${text}ex';
+}
+
+class AngleTerm extends UnitTerm {
+  AngleTerm(var value, String t, lang.SourceSpan span,
+    [int unit = TokenKind.UNIT_LENGTH_PX]) : super(value, t, span, unit) {
+    assert(this._unit == TokenKind.UNIT_ANGLE_DEG ||
+        this._unit == TokenKind.UNIT_ANGLE_RAD ||
+        this._unit == TokenKind.UNIT_ANGLE_GRAD);
+  }
+
+  visit(TreeVisitor visitor) => visitor.visitAngleTerm(this);
+}
+
+class TimeTerm extends UnitTerm {
+  TimeTerm(var value, String t, lang.SourceSpan span,
+    [int unit = TokenKind.UNIT_LENGTH_PX]) : super(value, t, span, unit) {
+    assert(this._unit == TokenKind.UNIT_ANGLE_DEG ||
+        this._unit == TokenKind.UNIT_TIME_MS ||
+        this._unit == TokenKind.UNIT_TIME_S);
+  }
+
+  visit(TreeVisitor visitor) => visitor.visitTimeTerm(this);
+}
+
+class FreqTerm extends UnitTerm {
+  FreqTerm(var value, String t, lang.SourceSpan span,
+    [int unit = TokenKind.UNIT_LENGTH_PX]) : super(value, t, span, unit) {
+    assert(_unit == TokenKind.UNIT_FREQ_HZ || _unit == TokenKind.UNIT_FREQ_KHZ);
+  }
+
+  visit(TreeVisitor visitor) => visitor.visitFreqTerm(this);
+}
+
+class FractionTerm extends LiteralTerm {
+  FractionTerm(var value, String t, lang.SourceSpan span) :
+    super(value, t, span);
+
+  visit(TreeVisitor visitor) => visitor.visitFractionTerm(this);
+
+  String toString() => '${text}fr';
+}
+
+class UriTerm extends LiteralTerm {
+  UriTerm(String value, lang.SourceSpan span) : super(value, value, span);
+
+  visit(TreeVisitor visitor) => visitor.visitUriTerm(this);
+  
+  String toString() => 'url(${text})';
+}
+
+class HexColorTerm extends LiteralTerm {
+  HexColorTerm(var value, String t, lang.SourceSpan span) :
+      super(value, t, span);
+
+  visit(TreeVisitor visitor) => visitor.visitHexColorTerm(this);
+  
+  String toString() => '#${text}';
+}
+
+class FunctionTerm extends LiteralTerm {
+  Expressions _params;
+
+  FunctionTerm(var value, String t, this._params, lang.SourceSpan span)
+      : super(value, t, span);
+
+  visit(TreeVisitor visitor) => visitor.visitFunctionTerm(this);
+
+  String toString() {
+    // TODO(terry): Optimize rgb to a hexcolor.
+    StringBuffer buff = new StringBuffer();
+
+    buff.add('${text}(');
+    buff.add(_params.toString());
+    buff.add(')');
+
+    return buff.toString();
+  }
+}
+
+class GroupTerm extends lang.Expression {
+  List<LiteralTerm> _terms;
+
+  GroupTerm(lang.SourceSpan span) : _terms =  [], super(span);
+
+  add(LiteralTerm term) {
+    _terms.add(term);
+  }
+
+  visit(TreeVisitor visitor) => visitor.visitGroupTerm(this);
+
+  String toString() {
+    StringBuffer buff = new StringBuffer();
+    buff.add('(');
+    int idx = 0;
+    for (var term in _terms) {
+      if (idx++ > 0) {
+        buff.add(' ');
+      }
+      buff.add(term.toString());
+    }
+    buff.add(')');
+    return buff.toString();
+  }
+}
+
+class ItemTerm extends NumberTerm {
+  ItemTerm(var value, String t, lang.SourceSpan span) : super(value, t, span);
+
+  visit(TreeVisitor visitor) => visitor.visitItemTerm(this);
+
+  String toString() => '[${text}]';
+}
+
+class Expressions extends lang.Expression {
+  List<lang.Expression> _expressions;
+
+  Expressions(lang.SourceSpan span): super(span), _expressions = [];
+
+  add(lang.Expression expression) {
+    _expressions.add(expression);
+  }
+
+  List<lang.Expression> get expressions() => _expressions;
+
+  visit(TreeVisitor visitor) => visitor.visitExpressions(this);
+
+  String toString() {
+    StringBuffer buff = new StringBuffer();
+    int idx = 0;
+    for (var expression in _expressions) {
+      // Add space seperator between terms without an operator.
+      // TODO(terry): Should have a BinaryExpression to solve this problem.
+      if (idx > 0 &&
+          !(expression is OperatorComma || expression is OperatorSlash)) {
+        buff.add(' ');
+      }
+      buff.add(expression.toString());
+      idx++;
+    }
+    return buff.toString();
+  }
+}
+
+class BinaryExpression extends lang.Expression {
+  lang.Token op;
+  lang.Expression x;
+  lang.Expression y;
+
+  BinaryExpression(this.op, this.x, this.y, lang.SourceSpan span): super(span);
+
+  visit(TreeVisitor visitor) => visitor.visitBinaryExpression(this);
+}
+
+class UnaryExpression extends lang.Expression {
+  lang.Token op;
+  lang.Expression self;
+
+  UnaryExpression(this.op, this.self, lang.SourceSpan span): super(span);
+
+  visit(TreeVisitor visitor) => visitor.visitUnaryExpression(this);
 }
 
 interface TreeVisitor {
+  void visitComment(Comment node);
+  void visitCommentDefinition(CommentDefinition node);
+  void visitStylesheet(Stylesheet node);
+  void visitTopLevelProduction(TopLevelProduction node);
+  void visitDirective(Directive node);
+  void visitMediaDirective(MediaDirective node);
+  void visitPageDirective(PageDirective node);
+  void visitImportDirective(ImportDirective node);
+  void visitKeyFrameDirective(KeyFrameDirective node);
+  void visitKeyFrameBlock(KeyFrameBlock node);
+  void visitFontFaceDirective(FontFaceDirective node);
+  void visitIncludeDirective(IncludeDirective node);
+  void visitStyletDirective(StyletDirective node);
+  
+  void visitRuleSet(RuleSet node);
+  void visitDeclarationGroup(DeclarationGroup node);
+  void visitDeclaration(Declaration node);
   void visitSelectorGroup(SelectorGroup node);
+  void visitSelector(Selector node);
+  void visitSimpleSelectorSequence(SimpleSelectorSequence node);
   void visitSimpleSelector(SimpleSelector node);
   void visitElementSelector(ElementSelector node);
   void visitNamespaceSelector(NamespaceSelector node);
+  void visitAttributeSelector(AttributeSelector node);
   void visitIdSelector(IdSelector node);
   void visitClassSelector(ClassSelector node);
   void visitPseudoClassSelector(PseudoClassSelector node);
   void visitPseudoElementSelector(PseudoElementSelector node);
   void visitNotSelector(NotSelector node);
   
+  void visitLiteralTerm(LiteralTerm node);
+  void visitHexColorTerm(HexColorTerm node);
+  void visitNumberTerm(NumberTerm node);
+  void visitUnitTerm(UnitTerm node);
+  void visitLengthTerm(LengthTerm node);
+  void visitPercentageTerm(PercentageTerm node);
+  void visitEmTerm(EmTerm node);
+  void visitExTerm(ExTerm node);
+  void visitAngleTerm(AngleTerm node);
+  void visitTimeTerm(TimeTerm node);
+  void visitFreqTerm(FreqTerm node);
+  void visitFractionTerm(FractionTerm node);
+  void visitUriTerm(UriTerm node);
+  void visitFunctionTerm(FunctionTerm node);
+  void visitGroupTerm(GroupTerm node);
+  void visitItemTerm(ItemTerm node);
+  void visitOperatorSlash(OperatorSlash node);
+  void visitOperatorComma(OperatorComma node);
+
+  void visitExpressions(Expressions node);
+  void visitBinaryExpression(BinaryExpression node);
+  void visitUnaryExpression(UnaryExpression node);
+
   void visitIdentifier(Identifier node);
   void visitWildcard(Wildcard node);
 
   // TODO(terry): Defined for ../tree.dart.
   void visitTypeReference(lang.TypeReference node);
 }
 
 class TreePrinter implements TreeVisitor {
   var output;
   TreePrinter(this.output) { output.printer = this; }
 
+  void visitStylesheet(Stylesheet node) {
+    output.heading('Stylesheet', node.span);
+    output.depth++;
+    output.writeNodeList('productions', node._topLevels);
+    output.depth--;
+  }
+
+  void visitTopLevelProduction(TopLevelProduction node) {
+    output.heading('TopLevelProduction', node.span);
+  }
+
+  void visitDirective(Directive node) {
+    output.heading('Directive', node.span);
+  }
+
+  void visitComment(Comment node) {
+    output.heading('Comment', node.span);
+    output.depth++;
+    output.writeValue('comment value', node.comment);
+    output.depth--;
+  }
+
+  void visitCommentDefinition(CommentDefinition node) {
+    output.heading('CommentDefinition (CDO/CDC)', node.span);
+    output.depth++;
+    output.writeValue('comment value', node.comment);
+    output.depth--;
+  }
+
+  void visitMediaDirective(MediaDirective node) {
+    output.heading('MediaDirective', node.span);
+    output.depth++;
+    output.writeNodeList('media', node._media);
+    visitRuleSet(node._ruleset);
+    output.depth--;
+  }
+
+  void visitPageDirective(PageDirective node) {
+    output.heading('PageDirective', node.span);
+    output.depth++;
+    output.writeValue('pseudo page', node._pseudoPage);
+    visitDeclarationGroup(node._decls);
+    output.depth;
+}
+
+  void visitImportDirective(ImportDirective node) {
+    output.heading('ImportDirective', node.span);
+    output.depth++;
+    output.writeValue('import', node._import);
+    output.writeNodeList('media', node._media);
+    output.depth--;
+  }
+
+  void visitKeyFrameDirective(KeyFrameDirective node) {
+    output.heading('KeyFrameDirective', node.span);
+    output.depth++;
+    output.writeValue('name', node._name);
+    output.writeNodeList('blocks', node._blocks);
+    output.depth--;
+  }
+
+  void visitKeyFrameBlock(KeyFrameBlock node) {
+    output.heading('KeyFrameBlock', node.span);
+    output.depth++;
+    visitExpressions(node._blockSelectors);
+    visitDeclarationGroup(node._declarations);    
+    output.depth--;
+  }
+
+  void visitFontFaceDirective(FontFaceDirective node) {
+    // TODO(terry): To Be Implemented
+  }
+
+  void visitIncludeDirective(IncludeDirective node) {
+    output.heading('IncludeDirective', node.span);
+    output.writeValue('include', node._include);
+    output.depth++;
+    if (node._stylesheet != null) {
+      visitStylesheet(node._stylesheet);
+    } else {
+      output.writeValue('StyleSheet', '<EMPTY>');
+    }
+    output.depth--;
+  }
+
+  void visitStyletDirective(StyletDirective node) {
+    output.heading('StyletDirective', node.span);
+    output.writeValue('dartClassName', node._dartClassName);
+    output.depth++;
+    output.writeNodeList('rulesets', node._rulesets);
+    output.depth--;
+}
+
+  void visitRuleSet(RuleSet node) {
+    output.heading('Ruleset', node.span);
+    output.depth++;
+    visitSelectorGroup(node._selectorGroup);
+    visitDeclarationGroup(node._declarationGroup);
+    output.depth--;
+  }
+
+  void visitDeclarationGroup(DeclarationGroup node) {
+    output.heading('DeclarationGroup', node.span);
+    output.depth++;
+    output.writeNodeList('declarations', node._declarations);
+    output.depth--;
+  }
+
+  void visitDeclaration(Declaration node) {
+    output.heading('Declaration', node.span);
+    output.depth++;
+    output.write('property');
+    visitIdentifier(node._property);
+    output.writeNode('expression', node._expression);
+    if (node.important) {
+      output.writeValue('!important', 'true');
+    }
+    output.depth--;
+  }
+
   void visitSelectorGroup(SelectorGroup node) {
     output.heading('Selector Group', node.span);
+    output.depth++;
     output.writeNodeList('selectors', node.selectors);
-    output.writeln('');
+    output.depth--;
   }
 
-  void visitSimpleSelector(SimpleSelector node) {
+  void visitSelector(Selector node) {
+    output.heading('Selector', node.span);
+    output.depth++;
+    output.writeNodeList('simpleSelectorsSequences',
+        node._simpleSelectorSequences);
+    output.depth--;
+  }
+
+  void visitSimpleSelectorSequence(SimpleSelectorSequence node) {
+    output.heading('SimpleSelectorSequence', node.span);
+    output.depth++;
     if (node.isCombinatorNone()) {
       output.writeValue('combinator', "NONE");
     } else if (node.isCombinatorDescendant()) {
       output.writeValue('combinator', "descendant");
     } else if (node.isCombinatorPlus()) {
       output.writeValue('combinator', "+");
     } else if (node.isCombinatorGreater()) {
       output.writeValue('combinator', ">");
     } else if (node.isCombinatorTilde()) {
       output.writeValue('combinator', "~");
     } else {
       output.writeValue('combinator', "ERROR UNKNOWN");
     }
+
+    var selector = node._selector;
+    if (selector is NamespaceSelector) {
+      visitNamespaceSelector(selector);
+    } else if (selector is ElementSelector) {
+      visitElementSelector(selector);
+    } else if (selector is IdSelector) {
+      visitIdSelector(selector);
+    } else if (selector is ClassSelector) {
+      visitClassSelector(selector);
+    } else if (selector is PseudoClassSelector) {
+      visitPseudoClassSelector(selector);
+    } else if (selector is PseudoElementSelector) {
+      visitPseudoElementSelector(selector);
+    } else if (selector is NotSelector) {
+      visitNotSelector(selector);
+    } else if (selector is AttributeSelector) {
+      visitAttributeSelector(selector);
+    } else {
+      output.heading('SimpleSelector', selector.span);
+      output.depth++;
+      visitSimpleSelector(selector);
+      output.depth--;
+    }
+
+    output.depth--;
+  }
+
+  void visitSimpleSelector(SimpleSelector node) {
+    visitIdentifier(node._name);
   }
 
   void visitNamespaceSelector(NamespaceSelector node) {
     output.heading('Namespace Selector', node.span);
-    visitSimpleSelector(node);
-    output.writeNode('namespace', node._namespace);
-    output.writeNode('name', node._name);
+    output.depth++;
+
+    var namespace = node._namespace;
+    if (namespace is Identifier) {
+      visitIdentifier(namespace);
+    } else if (namespace is Wildcard) {
+      visitWildcard(namespace);
+    } else {
+      output.writeln("NULL");
+    }
+
+    visitSimpleSelector(node);
+    output.depth--;
   }
 
   void visitElementSelector(ElementSelector node) {
     output.heading('Element Selector', node.span);
-    visitSimpleSelector(node);
-    output.writeNode('name', node._name);
+    output.depth++;
+    visitSimpleSelector(node);
+    output.depth--;
+  }
+
+  void visitAttributeSelector(AttributeSelector node) {
+    output.heading('AttributeSelector', node.span);
+    output.depth++;
+    visitSimpleSelector(node);
+    String tokenStr = node.matchOperatorAsTokenString();
+    output.writeValue('operator', '${node.matchOperator()} (${tokenStr})');
+    output.writeValue('value', node.valueToString());
+    output.depth--;
   }
 
   void visitIdSelector(IdSelector node) {
     output.heading('Id Selector', node.span);
-    visitSimpleSelector(node);
-    output.writeNode('name', node._name);
+    output.depth++;
+    visitSimpleSelector(node);
+    output.depth--;
   }
 
   void visitClassSelector(ClassSelector node) {
     output.heading('Class Selector', node.span);
-    visitSimpleSelector(node);
-    output.writeNode('name', node._name);
+    output.depth++;
+    visitSimpleSelector(node);
+    output.depth--;
   }
 
   void visitPseudoClassSelector(PseudoClassSelector node) {
     output.heading('Pseudo Class Selector', node.span);
-    visitSimpleSelector(node);
-    output.writeNode('name', node._name);
+    output.depth++;
+    visitSimpleSelector(node);
+    output.depth--;
   }
 
   void visitPseudoElementSelector(PseudoElementSelector node) {
     output.heading('Pseudo Element Selector', node.span);
-    visitSimpleSelector(node);
-    output.writeNode('name', node._name);
+    output.depth++;
+    visitSimpleSelector(node);
+    output.depth--;
   }
 
   void visitNotSelector(NotSelector node) {
     visitSimpleSelector(node);
+    output.depth++;
     output.heading('Not Selector', node.span);
+    output.depth--;
+  }
+
+  void visitLiteralTerm(LiteralTerm node) {
+    output.heading('LiteralTerm', node.span);
+    output.depth++;
+    output.writeValue('value', node.text);
+    output.depth--;
+ }
+
+  void visitHexColorTerm(HexColorTerm node) {
+    output.heading('HexColorTerm', node.span);
+    output.depth++;
+    output.writeValue('hex value', node.text);
+    output.writeValue('decimal value', node.value);
+    output.depth--;
+  }
+
+  void visitNumberTerm(NumberTerm node) {
+    output.heading('NumberTerm', node.span);
+    output.depth++;
+    output.writeValue('value', node.text);
+    output.depth--;
+  }
+
+  void visitUnitTerm(UnitTerm node) {
+    String unitValue;
+
+    output.depth++;
+    output.writeValue('value', node.text);
+    output.writeValue('unit', node.unitToString());
+    output.depth--;
+  }
+
+  void visitLengthTerm(LengthTerm node) {
+    output.heading('LengthTerm', node.span);
+    visitUnitTerm(node);
+  }
+
+  void visitPercentageTerm(PercentageTerm node) {
+    output.heading('PercentageTerm', node.span);
+    output.depth++;
+    visitLiteralTerm(node);
+    output.depth--;
+  }
+  
+  void visitEmTerm(EmTerm node) {
+    output.heading('EmTerm', node.span);
+    output.depth++;
+    visitLiteralTerm(node);
+    output.depth--;
+  }
+
+  void visitExTerm(ExTerm node) {
+    output.heading('ExTerm', node.span);
+    output.depth++;
+    visitLiteralTerm(node);
+    output.depth--;
+  }
+
+  void visitAngleTerm(AngleTerm node) {
+    output.heading('AngleTerm', node.span);
+    visitUnitTerm(node);
+  }
+
+  void visitTimeTerm(TimeTerm node) {
+    output.heading('TimeTerm', node.span);
+    visitUnitTerm(node);
+  }
+
+  void visitFreqTerm(FreqTerm node) {
+    output.heading('FreqTerm', node.span);
+    visitUnitTerm(node);
+  }
+
+  void visitFractionTerm(FractionTerm node) {
+    output.heading('FractionTerm', node.span);
+    output.depth++;
+    visitLiteralTerm(node);
+    output.depth--;
+  }
+
+  void visitUriTerm(UriTerm node) {
+    output.heading('UriTerm', node.span);
+    output.depth++;
+    visitLiteralTerm(node);
+    output.depth--;
+  }
+
+  void visitFunctionTerm(FunctionTerm node) {
+    output.heading('FunctionTerm', node.span);
+    output.depth++;
+    visitLiteralTerm(node);
+    visitExpressions(node._params);
+    output.depth--;
+  }
+
+  void visitGroupTerm(GroupTerm node) {
+    output.heading('GroupTerm', node.span);
+    output.depth++;
+    output.writeNodeList('grouped terms', node._terms);
+    output.depth--;
+  }
+
+  void visitItemTerm(ItemTerm node) {
+    output.heading('ItemTerm', node.span);
+    visitNumberTerm(node);
+  }
+
+  void visitOperatorSlash(OperatorSlash node) {
+    output.heading('OperatorSlash', node.span);
+  }
+
+  void visitOperatorComma(OperatorComma node) {
+    output.heading('OperatorComma', node.span);
+  }
+
+  void visitExpressions(Expressions node) {
+    output.heading('Expressions', node.span);
+    output.depth++;
+    output.writeNodeList('expressions', node._expressions);
+    output.depth--;
+  }
+
+  void visitBinaryExpression(BinaryExpression node) {
+    output.heading('BinaryExpression', node.span);
+    // TODO(terry): TBD
+  }
+
+  void visitUnaryExpression(UnaryExpression node) {
+    output.heading('UnaryExpression', node.span);
+    // TODO(terry): TBD
   }
 
   void visitIdentifier(Identifier node) {
     output.heading('Identifier(' + output.toValue(node.name) + ")", node.span);
   }
 
   void visitWildcard(Wildcard node) {
     output.heading('Wildcard(*)', node.span);
   }
 
   // TODO(terry): Defined for frog/tree.dart.
   void visitTypeReference(lang.TypeReference node) {
     output.heading('Unimplemented');
   }
 }