Redo LocationManager to use HTML5 History API

runtime/bin/vmservice/client/lib/src/app/application.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.
 
 part of app;
 
-/// A request response interceptor is called for each response.
-typedef void RequestResponseInterceptor();
+/// A [Pane] controls the user interface of Observatory. At any given time
+/// one pane will be the current pane. Panes are registered at startup.
+/// When the user navigates within the application, each pane is asked if it
+/// can handle the current location, the first pane to say yes, wins.
+abstract class Pane extends Observable {
+  final ObservatoryApplication app;
+
+  @observable ObservatoryElement element;
+
+  Pane(this.app);
+
+  /// Called when the pane is installed, this callback must initialize
+  /// [element].
+  void onInstall();
+
+  /// Called when the pane is uninstalled, this callback must clear
+  /// [element].
+  void onUninstall() {
+    element = null;
+  }
+
+  /// Called when the pane should update its state based on [url].
+  /// NOTE: Only called when the pane is installed.
+  void visit(String url);
+
+  /// Called to test whether this pane can visit [url].
+  bool canVisit(String url);
+}
+
+/// A general service object viewer.
+class ServiceObjectPane extends Pane {
+  ServiceObjectPane(app) : super(app);
+
+  void onInstall() {
+    if (element == null) {
+      /// Lazily create pane.
+      element = new Element.tag('service-view');
+    }
+  }
+
+  void visit(String url) {
+    assert(element != null);
+    assert(canVisit(url));
+    /// Request url from VM and display it.
+    app.vm.get(url).then((obj) {
+      ServiceObjectViewElement pane = element;
+      pane.object = obj;
+    });
+  }
+
+  /// Catch all.
+  bool canVisit(String url) => true;
+}
+
+/// Class tree pane.
+class ClassTreePane extends Pane {
+  static const _urlPrefix = 'class-tree/';
+
+  ClassTreePane(app) : super(app);
+
+  void onInstall() {
+    if (element == null) {
+      element = new Element.tag('class-tree');
+    }
+  }
+
+  void visit(String url) {
+    assert(element != null);
+    assert(canVisit(url));
+    // ClassTree urls are 'class-tree/isolate-id', chop off prefix, leaving
+    // isolate url.
+    url = url.substring(_urlPrefix.length);
+    /// Request the isolate url.
+    app.vm.get(url).then((i) {
+      if (element != null) {
+        /// Update the pane.
+        ClassTreeElement pane = element;
+        pane.isolate = i;
+      }
+    });
+  }
+
+  /// Catch all.
+  bool canVisit(String url) => url.startsWith(_urlPrefix);
+}
+
+class ErrorViewPane extends Pane {
+  ErrorViewPane(app) : super(app);
+
+  void onInstall() {
+    if (element == null) {
+      /// Lazily create pane.
+      element = new Element.tag('service-view');
+    }
+  }
+
+  void visit(String url) {
+    assert(element != null);
+    assert(canVisit(url));
+    (element as ServiceObjectViewElement).object = app.lastErrorOrException;
+  }
+
+  bool canVisit(String url) => url.startsWith('error/');
+}
 
 /// The observatory application. Instances of this are created and owned
 /// by the observatory_application custom element.
 class ObservatoryApplication extends Observable {
+  final _paneRegistry = new List<Pane>();
+  ServiceObjectPane _serviceObjectPane;
+  Pane _currentPane;
   @observable final LocationManager locationManager;
   @observable final VM vm;
   @observable Isolate isolate;
-
-  /// The current [ServiceObject] being viewed by the application.
-  @observable ServiceObject response;
+  @reflectable final ObservatoryApplicationElement rootElement;
+
+  @reflectable ServiceObject lastErrorOrException;
 
   /// Any client-level arguments for viewing the current response.
   @observable String args;
   // TODO(turnidge): Make args a Map.
 
   void _initOnce() {
-    // Only called once.
-    assert(locationManager._app == null);
-    locationManager._app = this;
-    locationManager.init();
+    _registerPanes();
     vm.errors.stream.listen(_onError);
     vm.exceptions.stream.listen(_onException);
+    location = locationManager;
+    locationManager._init(this);
+  }
+
+  void _registerPanes() {
+    if (_serviceObjectPane != null) {
+      // Already done.
+      return;
+    }
+    // Register ClassTreePane.
+    _paneRegistry.add(new ClassTreePane(this));
+    _paneRegistry.add(new ErrorViewPane(this));
+    // Note that ServiceObjectPane must be the last entry in the list as it is
+    // the catch all.
+    _serviceObjectPane = new ServiceObjectPane(this);
+    _paneRegistry.add(_serviceObjectPane);
   }
 
   void _onError(ServiceError error) {
-    response = error;
-    // No id, clear the hash.
-    locationManager.clearCurrentHash();
+    lastErrorOrException = error;
+    _visit('error/');
   }
 
   void _onException(ServiceException exception) {
-    response = exception;
-    // No id, clear the hash.
-    locationManager.clearCurrentHash();
-  }
-
-  ObservatoryApplication.devtools() :
-      locationManager = new LocationManager(),
+    lastErrorOrException = exception;
+    _visit('error/');
+  }
+
+  void _visit(String url) {
+    for (var i = 0; i < _paneRegistry.length; i++) {
+      var pane = _paneRegistry[i];
+      if (pane.canVisit(url)) {
+        _installPane(pane);
+        pane.visit(url);
+        return;
+      }
+    }
+    throw new FallThroughError();
+  }
+
+  /// Set the Observatory application pane.
+  void _installPane(Pane pane) {
+    assert(pane != null);
+    print('Installing $pane');
+    if (_currentPane == pane) {
+      // Already isntalled.
+      return;
+    }
+    if (_currentPane != null) {
+      _currentPane.onUninstall();
+    }
+    pane.onInstall();
+    // Clear children.
+    rootElement.children.clear();
+    // Add new pane.
+    rootElement.children.add(pane.element);
+    // Remember pane.
+    _currentPane = pane;
+  }
+
+  ObservatoryApplication.devtools(this.rootElement) :
+      locationManager = new HashLocationManager(),
       vm = new DartiumVM() {
     _initOnce();
   }
 
-  ObservatoryApplication() :
-      locationManager = new LocationManager(),
-          vm = new WebSocketVM() {
+  ObservatoryApplication(this.rootElement) :
+      locationManager = new HashLocationManager(),
+      vm = new HttpVM() {
     _initOnce();
   }
 }
+
+LocationManager location;