Prevent users from signing up with or changing to an email-like username

app/locale/en.coffee

@@ -287,6 +287,7 @@
     email_good: "Email looks good!"
     name_taken: "Username already taken! Try {{suggestedName}}?"
     name_available: "Username available!"
+    name_is_email: "Username may not be an email"
     choose_type: "Choose your account type:"
     teacher_type_1: "Teach programming using CodeCombat!"
     teacher_type_2: "Set up your class"

app/views/account/AccountSettingsView.coffee

@@ -231,7 +231,7 @@ module.exports = class AccountSettingsView extends CocoView
         $('.nano').nanoScroller({scrollTo: @$el.find('.has-error')})
       else
         noty
-          text: res.responseText
+          text: res.responseJSON?.message or res.responseText
           type: 'error'
           layout: 'topCenter'
           timeout: 5000

app/views/core/CreateAccountModal/BasicInfoView.coffee

@@ -146,6 +146,11 @@ module.exports = class BasicInfoView extends CocoView
     })
     
     forms.clearFormAlerts(@$el)
+    
+    if data.name and forms.validateEmail(data.name)
+      forms.setErrorToProperty(@$el, 'name', $.i18n.t('signup.name_is_email'))
+      return false
+    
     res = tv4.validateMultiple data, @formSchema()
     forms.applyErrorsToForm(@$('form'), res.errors) unless res.valid
     return res.valid

server/models/User.coffee

@@ -361,6 +361,10 @@ UserSchema.pre('save', (next) ->
     @set('email', undefined)
     @set('emailLower', undefined)
   if name = @get('name')
+    filter = /^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,63}$/i  # https://news.ycombinator.com/item?id=5763990
+    if filter.test(name)
+      return next(new errors.UnprocessableEntity('Name may not be an email'))
+  
     @set('nameLower', name.toLowerCase())
   else
     @set('name', undefined)