packages/polymer/lib/src/loader.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 polymer;

/// Initializes a polymer application as follows:
///   * if running in development mode, set up a dirty-checking zone that polls
///     for observable changes
///   * initialize template binding and polymer-element
///   * for each library included transitively from HTML and HTML imports,
///   register custom elements declared there (labeled with [CustomTag]) and
///   invoke the initialization method on it (top-level functions annotated with
///   [initMethod]).
Future<Zone> initPolymer() {
  _initializeLogging();
  if (_deployMode) {
    return startPolymer().then((_) => Zone.current);
  }
  return dirtyCheckZone()
      .run(() => startPolymer().then((_) => dirtyCheckZone()));
}

bool _startPolymerCalled = false;

/// Starts polymer by hooking the polymer.js code. **Note**: this function is
/// not meant to be invoked directly by application developers. It is invoked
/// by [initPolymer].
Future startPolymer() {
  // First wait for all html imports to finish, then run the rest of the
  // initializers.
  return initWebComponents(initAll: false).then((_) {
    // Polymer js is now loaded, hook it before running @CustomTag annotations.
    if (_startPolymerCalled) throw 'Initialization was already done.';
    _startPolymerCalled = true;
    _hookJsPolymer();
  }).then((_) => initWebComponents()).then((_) {
    Polymer.registerSync('auto-binding-dart', AutoBindingElement,
        extendsTag: 'template');

    _watchWaitingFor();
    Polymer._onInitDone.complete();
  });
}

/// Configures [initPolymer] making it optimized for deployment to the internet.
/// Additionally, after this method is called [initPolymer] omits the [Zone]
/// that automatically invokes [Observable.dirtyCheck].
void configureForDeployment() {
  _deployMode = true;
}

/// To ensure Dart can interoperate with polymer-element registered by
/// polymer.js, we need to be able to execute Dart code if we are registering
/// a Dart class for that element. We trigger Dart logic by patching
/// polymer-element's register function and:
///
/// * if it has a Dart class, run PolymerDeclaration's register.
/// * otherwise it is a JS prototype, run polymer-element's normal register.
void _hookJsPolymer() {
  if (!PolymerJs.checkExists()) {
    throw new StateError('An error occurred initializing polymer, (could not'
        'find polymer js). Please file a bug at '
        'https://github.com/dart-lang/polymer-dart/issues/new.');
  }

  // TODO(jmesserly): dart:js appears to not callback in the correct zone:
  // https://code.google.com/p/dart/issues/detail?id=17301
  var zone = Zone.current;

  PolymerJs.whenPolymerReady(() => Polymer._onReady.complete());

  JsFunction originalRegister = _polymerElementProto['register'];
  if (originalRegister == null) {
    throw new StateError('polymer.js must expose "register" function on '
        'polymer-element to enable polymer.dart to interoperate.');
  }

  registerDart(jsElem, String name, String extendee) {
    // By the time we get here, we'll know for sure if it is a Dart object
    // or not, because polymer-element will wait for us to notify that
    // the @CustomTag was found.
    final type = _getRegisteredType(name);
    if (type != null) {
      final extendsDecl = _getDeclaration(extendee);
      return zone.run(() =>
          new PolymerDeclaration(jsElem, name, type, extendsDecl).register());
    }
    // It's a JavaScript polymer element, fall back to the original register.
    return originalRegister.apply([name, extendee], thisArg: jsElem);
  }

  _polymerElementProto['register'] = new JsFunction.withThis(registerDart);
}

// Note: we cache this so we can use it later to look up 'init'.
// See registerSync.
JsObject _polymerElementProto = () {
  var polyElem = document.createElement('polymer-element');
  var proto = new JsObject.fromBrowserObject(polyElem)['__proto__'];
  if (proto is Node) proto = new JsObject.fromBrowserObject(proto);
  return proto;
}();

// Add support for the polymer js style of enabling logging. The global logging
// level is respected for specified loggers (see http://goo.gl/btfDe1). All
// other loggers will be set to [Level.OFF]. Logs will also be printed to the
// console automatically if any are supplied.
void _initializeLogging() {
  hierarchicalLoggingEnabled = true;
  var webComponents = js.context['WebComponents'];
  var logFlags = (webComponents == null || webComponents['flags'] == null)
      ? {}
      : webComponents['flags']['log'];
  if (logFlags == null) logFlags = {};
  var loggers = [
    _observeLog,
    _eventsLog,
    _unbindLog,
    _bindLog,
    _watchLog,
    _readyLog
  ];
  var polymerLogger = new Logger('polymer');

  // If no loggers specified then disable globally and return.
  if (!loggers.any((logger) => logFlags[logger.name] == true)) {
    polymerLogger.level = Level.OFF;
    return;
  }

  // Disable the loggers that were not specified.
  loggers.where((logger) => logFlags[logger.name] != true).forEach((logger) {
    logger.level = Level.OFF;
  });

  // Listen to the polymer logs and print them to the console.
  polymerLogger.onRecord.listen((rec) {
    print(rec);
  });
}

/// Watches the waitingFor queue and if it fails to make progress then prints
/// a message to the console.
void _watchWaitingFor() {
  int lastWaiting = Polymer.waitingFor.length;
  int lastAlert;
  new Timer.periodic(new Duration(seconds: 1), (Timer timer) {
    var waiting = Polymer.waitingFor;
    // Done, cancel timer.
    if (waiting.isEmpty) {
      timer.cancel();
      return;
    }
    // Made progress, don't alert.
    if (waiting.length != lastWaiting) {
      lastWaiting = waiting.length;
      return;
    }
    // Only alert once per waiting state.
    if (lastAlert == lastWaiting) return;
    lastAlert = lastWaiting;

    print('No elements registered in a while, but still waiting on '
        '${waiting.length} elements to be registered. Check that you have a '
        'class with an @CustomTag annotation for each of the following tags: '
        '${waiting.map((e) => "'${e.attributes['name']}'").join(', ')}');
  });
}