Email Available directive for AngularJS

email-available.coffee

angular.directive "emailAvailable", ($http, $timeout) ->
  require: 'ngModel'
  link: (scope, elem, attrs, ctrl) ->
    console.log ctrl
    # push the validator on so it runs last.
    ctrl.$parsers.push (viewValue) ->
      # set it to true here, otherwise it will not
      # clear out when previous validators fail.
      ctrl.$setValidity "emailAvailable", true
      if ctrl.$valid
        # set it to false here, because if we need to check
        # the validity of the email, it's invalid until the
        # AJAX responds.
        ctrl.$setValidity "checkingEmail", false
        # now do your thing, chicken wing.
        if viewValue isnt "" and typeof viewValue isnt "undefined"
          $http.get("/email/" + viewValue + "/available").success((data, status, headers, config) ->
            ctrl.$setValidity "emailAvailable", true
            ctrl.$setValidity "checkingEmail", true
          ).error (data, status, headers, config) ->
            ctrl.$setValidity "emailAvailable", false
            ctrl.$setValidity "checkingEmail", true
        else
          ctrl.$setValidity "emailAvailable", false
          ctrl.$setValidity "checkingEmail", true
      viewValue

input.html

<div class="help-block" ng-show="signup.email.$dirty && signup.email.$invalid">Invalid:
  <span ng-show="signup.email.$error.email">This is not a valid email.</span>
  <span ng-show="signup.email.$error.checkingEmail">Checking email...</span>
  <span ng-show="signup.email.$error.emailAvailable">Email not available</span>
</div>