Checkout: When error, open offending accordion section

app/assets/javascripts/darkswarm/controllers/checkout/accordion_controller.js.coffee

@@ -6,6 +6,15 @@ Darkswarm.controller "AccordionCtrl", ($scope, storage, $timeout, CurrentHub) ->
     billing: false
   storage.bind $scope, "accordion", {storeName: "accordion_#{$scope.order.id}#{CurrentHub.hub.id}#{$scope.order.user_id}"}
 
-  $scope.show = (name)->
-    $scope.accordion[name] = true
+  $scope.show = (section)->
+    $scope.accordion[section] = true
 
+  $scope.$on 'purchaseFormInvalid', (event, form) ->
+    # Scroll to first invalid section
+    # TODO: hide all first
+    # TODO: Use Object.keys($scope.accordion)
+    sections = ["details", "billing", "shipping", "payment"]
+    for section in sections
+      if not form[section].$valid
+        $scope.show section
+        break

app/assets/javascripts/darkswarm/controllers/checkout/checkout_controller.js.coffee

@@ -21,4 +21,7 @@ Darkswarm.controller "CheckoutCtrl", ($scope, storage, Checkout, CurrentUser, Cu
   $scope.purchase = (event, form) ->
     event.preventDefault()
     $scope.submitted = true
-    $scope.Checkout.submit() if form.$valid
+    if form.$valid
+      $scope.Checkout.submit()
+    else
+      $scope.$broadcast 'purchaseFormInvalid', form