Add JsInitializerGenerator

lib/src/transformer/utils.dart

 // Copyright (c) 2014, 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 js.transformer.utils;
 
+import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/src/generated/element.dart';
-import 'package:analyzer/analyzer.dart';
+import 'package:barback/barback.dart';
 import 'package:js/src/metadata.dart';
+import 'package:path/path.dart' as path;
 import 'package:quiver/iterables.dart' show max;
 
-const String INITIALIZER_SUFFIX = "__init_js__.dart";
+const String DART_INITIALIZER_SUFFIX = "__init_js__.dart";
+const String JS_INITIALIZER_SUFFIX = "__init_js__.js";
 
 JsProxy getProxyAnnotation(ClassElement interface, ClassElement jsProxyClass) {
   var node = interface.node;
   for (Annotation a in node.metadata) {
     var e = a.element;
     if (e is ConstructorElement && e.type.returnType == jsProxyClass.type) {
       bool global;
       String constructor;
       for (Expression e in a.arguments.arguments) {
         if (e is NamedExpression) {
@@ skipping 23 matching lines @@
       insertImportOffset = libraryDirective.end;
     }
   } else {
     insertImportOffset = max(library.definingCompilationUnit.node.directives
         .where((d) => d is ImportDirective)
         .map((ImportDirective e) => e.end));
     if (insertImportOffset == null) insertImportOffset = 0;
   }
   return insertImportOffset;
 }
+
+
+final illegalIdRegex = new RegExp(r'[^a-zA-Z0-9_]');
+
+String assetIdToPrefix(AssetId id) =>
+    '_js__${id.package}__${id.path.replaceAll(illegalIdRegex, '_')}';
+
+String assetIdToJsExportCall(AssetId id) =>
+    '_export_${id.path.replaceAll(illegalIdRegex, '_')}(dart);';
+
+// TODO(justinfagnani): put this in code_transformers ?
+String getImportUri(AssetId importId, AssetId from) {
+  if (importId.path.startsWith('lib/')) {
+    // we support package imports
+    return "package:${importId.package}/${importId.path.substring(4)}";
+  } else if (importId.package == from.package) {
+    // we can support relative imports
+    return path.relative(importId.path, from: path.dirname(from.path));
+  }
+  // cannot import
+  return null;
+}