feat(components): add support for multiple insertion points

lib/core_dom/content_tag.dart

@@ -0,0 +1,139 @@
+part of angular.core.dom_internal;
+
+abstract class _ContentStrategy {
+  void attach();
+  void detach();
+  void insert(Iterable<dom.Node> nodes);
+}
+
+/**
+ * A null implementation of the content tag that is used by Shadow DOM components.
+ * The distribution is handled by the browser, so Angular does nothing.
+ */
+class _ShadowDomContent implements _ContentStrategy {
+  void attach(){}
+  void detach(){}
+  void insert(Iterable<dom.Node> nodes){}
+}
+
+/**
+ * An implementation of the content tag that is used by transcluding components.
+ * It is used when the content tag is not a direct child of another component,
+ * and thus does not affect redistribution.
+ */
+class _RenderedTranscludingContent implements _ContentStrategy {
+  final SourceLightDom _sourceLightDom;
+  final Content _content;
+
+  static final dom.ScriptElement _beginScriptTemplate =
+      new dom.ScriptElement()..type = "ng/content";
+
+  static final dom.ScriptElement _endScriptTemplate =
+      new dom.ScriptElement()..type = "ng/content";
+
+  dom.ScriptElement _beginScript;
+  dom.ScriptElement _endScript;
+
+  _RenderedTranscludingContent(this._content, this._sourceLightDom);
+
+  void attach(){
+    _replaceContentElementWithScriptTags();
+    _sourceLightDom.redistribute();
+  }
+
+  void detach(){
+    _removeScriptTags();
+    _sourceLightDom.redistribute();
+  }
+
+  void insert(Iterable<dom.Node> nodes){
+    final p = _endScript.parent;
+    if (p != null) p.insertAllBefore(nodes, _endScript);
+  }
+
+  void _replaceContentElementWithScriptTags() {
+    _beginScript = _beginScriptTemplate.clone(true);
+    _endScript = _endScriptTemplate.clone(true);
+
+    final el = _content.element;
+    el.parent.insertBefore(_beginScript, el);
+    el.parent.insertBefore(_endScript, el);
+    el.remove();
+  }
+
+  void _removeScriptTags() {
+    _removeNodesBetweenScriptTags();
+    _beginScript.remove();
+    _endScript.remove();
+  }
+
+  void _removeNodesBetweenScriptTags() {
+    final p = _beginScript.parent;
+    for (var next = _beginScript.nextNode;
+        next.nodeType != dom.Node.ELEMENT_NODE || next.attributes["ng/content"] != null;
+        next = _beginScript.nextNode) {
+      p.nodes.remove(next);
+    }
+  }
+}
+
+/**
+ * An implementation of the content tag that is used by transcluding components.
+ * It is used when the content tag is a direct child of another component,
+ * and thus does not get rendered but only affect the distribution of its parent component.
+ */
+class _IntermediateTranscludingContent implements _ContentStrategy {
+  final SourceLightDom _sourceLightDom;
+  final DestinationLightDom _destinationLightDom;
+  final Content _content;
+
+  _IntermediateTranscludingContent(this._content, this._sourceLightDom, this._destinationLightDom);
+
+  void attach(){
+    _sourceLightDom.redistribute();
+  }
+
+  void detach(){
+    _sourceLightDom.redistribute();
+  }
+
+  void insert(Iterable<dom.Node> nodes){
+    _content.element.nodes = nodes;
+    _destinationLightDom.redistribute();
+  }
+}
+
+@Decorator(selector: 'content')
+class Content implements AttachAware, DetachAware {
+  dom.Element element;
+
+  @NgAttr('select')
+  String select;
+
+  final SourceLightDom _sourceLightDom;
+  final DestinationLightDom _destinationLightDom;
+  var _strategy;
+
+  Content(this.element, this._sourceLightDom, this._destinationLightDom, View view) {
+    view.addContent(this);
+  }
+
+  void attach() => strategy.attach();
+  void detach() => strategy.detach();
+  void insert(Iterable<dom.Node> nodes) => strategy.insert(nodes);
+
+  _ContentStrategy get strategy {
+    if (_strategy == null) _strategy = _createContentStrategy();
+    return _strategy;
+  }
+
+  _ContentStrategy _createContentStrategy() {
+    if (_sourceLightDom == null) {
+      return new _ShadowDomContent();
+    } else if (_destinationLightDom != null && _destinationLightDom.hasRoot(element)) {
+      return new _IntermediateTranscludingContent(this, _sourceLightDom, _destinationLightDom);
+    } else {
+      return new _RenderedTranscludingContent(this, _sourceLightDom);
+    }
+  }
+}