routing.js

Router.onBeforeAction(function() {
  if (! Meteor.userId()) {
    this.render('login');
  } else {
    this.next();
  }
});

  Router.configure({
    layoutTemplate: 'ApplicationLayout'
  });
  // specify the top level route, the page users see when they arrive at the site
  Router.route('/', function () {
    console.log("rendering root /");
    this.render("navbar", {to:"header"});
    this.render("lobby_page", {to:"main"});  
  });

  // specify a route that allows the current user to chat to another users

  Router.route('/chat/:_id',{
  layoutTemplate:"ApplicationLayout",
  waitOn:function(){
    return Meteor.subscribe("currentChat",this.params._id);//,
  },
  template:"navbar",
  template:"chat_page",
  yieldTemplates: {
    "navbar":{to:"header"},
    "chat_page":{to:"main"}
  },
  data: function () {
    // the user they want to chat to has id equal to 
    // the id sent in after /chat/... 
    var otherUserId = this.params._id; 
    // find a chat that has two users that match current user id
    // and the requested user id
    var filter = {$or:[
                {user1Id:Meteor.userId(), user2Id:otherUserId}, 
                {user2Id:Meteor.userId(), user1Id:otherUserId}
                ]};
    var chat = Chats.findOne(filter);
    if (!chat){// no chat matching the filter - need to insert a new one
      chatId=Meteor.call("insertChat",otherUserId)
      //chatId = Chats.insert({user1Id:Meteor.userId(), user2Id:otherUserId});
    }
    else {// there is a chat going already - use that. 
      chatId = chat._id;
    }
    if (chatId){// looking good, save the id to the UserSession
      UserSession.set("chatId",chatId);
    }
    return chat;
   }
  });