Updated interest buttons to use ajax instead of a round-trip post

app/assets/javascripts/main.js

@@ -91,4 +91,28 @@
 			htmlNode.setAttribute('data-input', 'mouse');
 		}
 	});
+	Array.prototype.forEach.call(document.querySelectorAll('form.js-xhr'), function(form) {
+		if (form.addEventListener) {
+			form.addEventListener('submit', function(event) {
+				event.preventDefault();
+				form.classList.add('requesting');
+				var data = new FormData(form);
+				var request = new XMLHttpRequest();
+				request.onreadystatechange = function() {
+					if (request.readyState == 4) {
+						form.classList.remove('requesting');
+						if (request.status == 200) {
+							var response = JSON.parse(request.responseText);
+							for (var i = 0; i < response.length; i++) {
+								form.querySelector(response[i].selector).outerHTML = response[i].html;
+							}
+						}
+					}
+				}
+				request.open('POST', form.getAttribute('action'), true);
+				request.setRequestHeader('X-Requested-With', 'XMLHttpRequest');
+				request.send(data);
+			}, false);
+		}
+	});
 })();

app/assets/stylesheets/_application.scss

@@ -591,6 +591,13 @@ input {
 }
 
 form {
+	@include _(transition, 'opacity 250ms ease-in-out, filter 250ms ease-in-out, -webkit-filter 250ms ease-in-out');
+
+	&.requesting {
+		opacity: 0.5;
+		-webkit-filter: blur(5px);
+	}
+	
 	&.composition {
 		textarea {
 			height: 16em;

app/controllers/conferences_controller.rb

@@ -1084,6 +1084,12 @@ class ConferencesController < ApplicationController
 		WorkshopInterest.create(:workshop_id => workshop.id, :user_id => current_user.id) unless interested
 
 		if request.xhr?
+			interest = workshop.interested?(current_user) ? :remove_interest : :show_interest
+			css_class = workshop.interested?(current_user) ? :delete : :add
+			render json: [ {
+					selector: 'button[value="toggle_interest"]',
+					html: view_context.button_tag(interest, :value => :toggle_interest, :class => css_class)
+				} ]
 		else
 			# go back to the workshop
 			redirect_to view_workshop_url(@this_conference.slug, workshop.id)

app/models/workshop.rb

@@ -94,6 +94,7 @@ class Workshop < ActiveRecord::Base
     end
 
     def can_translate?(user, lang)
+        return false unless user.present?
         user.can_translate?(lang, locale) || (can_edit?(user) && lang.to_s != locale.to_s)
     end
 

app/views/workshops/_show.html.haml

@@ -8,7 +8,7 @@
 			- else
 				=_'articles.workshops.info.interested_count', "#{workshop.interested_count} people are interested in this workshop", :vars => {:count => workshop.interested_count}
 			- if preview.blank? && workshop.can_show_interest?(current_user)
-				= form_tag toggle_workshop_interest_path(workshop.conference.slug, workshop.id) do
+				= form_tag toggle_workshop_interest_path(workshop.conference.slug, workshop.id), class: 'js-xhr' do
 					= button_tag (workshop.interested?(current_user) ? :remove_interest : :show_interest), :value => :toggle_interest, :class => (workshop.interested?(current_user) ? :delete : :add)
 		= richtext workshop.info
 		- if preview.blank? && translations_available_for_editing