app.js

var App = Em.Application.create();

App.ApplicationController = Em.Controller.extend();
App.ApplicationView = Em.View.extend({ templateName: 'application' });

App.HomeController = Em.Controller.extend();
App.HomeView = Em.View.extend({ templateName: 'home' });

App.AuthController = Em.Controller.extend({

  authenticated: false,
  failedAttempts: 0,

  authenticate: function() {
    if (this.credentialsValid()) {
      this.set('authenticated', true);
    } else {
      this.incrementProperty('failedAttempts');
    }
  },

  credentialsValid: function() {
    return this.get('email') === 'jamie@jgwhite.co.uk'
        && this.get('password') === 'ilovejam';
  },

  authenticatedDidChange: function() {
    if (this.get('authenticated')) {
      this.get('target').send('becomeAuthenticated');
    }
  }.observes('authenticated')

});
App.AuthView = Em.View.extend({
  tagName: 'form',
  templateName: 'auth'
});

App.TextField = Em.TextField.extend({ 
  attributeBindings: ['type', 'value', 'size', 'autofocus']
})

App.Router = Em.Router.extend({
  root: Em.Route.extend({

    // The unknown default state; neither authenticated nor unauthenticated.
    // The router knows to enter this state by default, then the unknown
    // state can decide whether to enter authenticated or unauthenticated mode.
    default: Em.Route.extend({
      route: '/',

      enter: function(router) {
        var authenticated = router.get('authController').get('authenticated');
        // It's not at all obvious why this works :(
        Em.run.next(function() {
          if (authenticated) {
            router.transitionTo('authenticated');
          } else {
            router.transitionTo('unauthenticated');
          }
        })
      }
    }),

    authenticated: Em.Route.extend({
      initialState: 'home',

      home: Em.Route.extend({
        route: '/home',
        connectOutlets: function(router) {
          router.get('applicationController').connectOutlet('home');
        }
      })

    }),

    unauthenticated: Em.Route.extend({
      initialState: 'auth',

      auth: Em.Route.extend({
        route: '/auth',
        connectOutlets: function(router) {
          router.get('applicationController').connectOutlet('auth');
        }
      }),

      authenticate: function(router) {
        router.get('authController').authenticate();
      },

      becomeAuthenticated: function(router) {
        router.transitionTo('authenticated');
      }

    })

  })
});

App.initialize();