Support compiling templates in the browser.

lib/src/template/file_system_browser.dart

+// Copyright (c) 2012, 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 file_system_browser;
+
+import 'dart:html';
+import 'file_system.dart';
+import 'package:js/js.dart' as js;
+
+
+/**
+ * File system implementation indirectly using the Chrome Extension Api's to
+ * proxy arbitrary urls. See extension/background.js for the code that does
+ * the actual proxying.
+ */
+class BrowserFileSystem implements FileSystem {
+
+  /**
+   * Chrome extension port used to communicate back to the source page that
+   * will consume these proxied urls.
+   */
+  js.Proxy sourcePagePort;
+
+  final _filesToProxy = <String>{};
+
+  BrowserFileSystem(this.sourcePagePort);
+
+  Future flush() {
+    // TODO(jacobr): this should really only return the future when the
+    // urls are fully proxied.
+    js.scoped(() {
+      var requests = [];
+      _filesToProxy.forEach((k,v) {
+        requests.add( js.map({'url': k, 'content': v}));
+      });
+      _filesToProxy.clear();
+      js.context.proxyUrls(sourcePagePort, js.array(requests));
+    });
+
+    return new Future.immediate(null);
+  }
+
+  void writeString(String path, String text) {
+    _filesToProxy[path] = text;
+  }
+
+  Future<String> readAll(String filename) {
+    var completer = new Completer<String>();
+    new HttpRequest.get(filename, onSuccess(HttpRequest request) {
+      completer.complete(request.responseText);
+    });
+    return completer.future;
+  }
+
+  void createDirectory(String path, [bool recursive = false]) {
+    // No need to actually create directories on the web.
+  }
+
+  void removeDirectory(String path, [bool recursive = false]) {
+    throw 'removeDirectory() is not implemented by BrowserFileSystem yet.';
+  }
+}