move fancy_syntax into Dart SVN

pkg/polymer_expressions/lib/polymer_expressions.dart

+// Copyright (c) 2013, 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.
+
+library polymer_expressions;
+
+import 'dart:async';
+import 'dart:html';
+
+import 'package:observe/observe.dart';
+
+import 'eval.dart';
+import 'expression.dart';
+import 'parser.dart';
+
+// TODO(justin): Investigate XSS protection
+Object _classAttributeConverter(v) =>
+    (v is Map) ? v.keys.where((k) => v[k] == true).join(' ') :
+    (v is Iterable) ? v.join(' ') :
+    v;
+
+Object _styleAttributeConverter(v) =>
+    (v is Map) ? v.keys.map((k) => '$k: ${v[k]}').join(';') :
+    (v is Iterable) ? v.join(';') :
+    v;
+
+class PolymerExpressions extends BindingDelegate {
+
+  final Map<String, Object> globals;
+
+  PolymerExpressions({Map<String, Object> globals})
+      : globals = (globals == null) ? new Map<String, Object>() : globals;
+
+  _Binding getBinding(model, String path, name, node) {
+    if (path == null) return null;
+    var expr = new Parser(path).parse();
+    if (model is! Scope) {
+      model = new Scope(model: model, variables: globals);
+    }
+    if (node is Element && name == "class") {
+      return new _Binding(expr, model, _classAttributeConverter);
+    }
+    if (node is Element && name == "style") {
+      return new _Binding(expr, model, _styleAttributeConverter);
+    }
+    return new _Binding(expr, model);
+  }
+
+  getInstanceModel(Element template, model) {
+    if (model is! Scope) {
+      var _scope = new Scope(model: model, variables: globals);
+      return _scope;
+    }
+    return model;
+  }
+}
+
+class _Binding extends Object with ChangeNotifierMixin {
+  static const _VALUE = const Symbol('value');
+
+  final Scope _scope;
+  final ExpressionObserver _expr;
+  final _converter;
+  var _value;
+
+
+  _Binding(Expression expr, Scope scope, [this._converter])
+      : _expr = observe(expr, scope),
+        _scope = scope {
+    _expr.onUpdate.listen(_setValue);
+    _setValue(_expr.currentValue);
+  }
+
+  _setValue(v) {
+    if (v is Comprehension) {
+      // convert the Comprehension into a list of scopes with the loop
+      // variable added to the scope
+      _value = v.iterable.map((i) {
+        var vars = new Map();
+        vars[v.identifier] = i;
+        Scope childScope = new Scope(parent: _scope, variables: vars);
+        return childScope;
+      }).toList(growable: false);
+    } else {
+      _value = (_converter == null) ? v : _converter(v);
+    }
+    notifyChange(new PropertyChangeRecord(_VALUE));
+  }
+
+  get value => _value;
+
+  set value(v) {
+    try {
+      assign(_expr, v, _scope);
+      notifyChange(new PropertyChangeRecord(_VALUE));
+    } on EvalException catch (e) {
+      // silently swallow binding errors
+    }
+  }
+
+  getValueWorkaround(key) {
+    if (key == _VALUE) return value;
+  }
+
+  setValueWorkaround(key, v) {
+    if (key == _VALUE) value = v;
+  }
+
+}