No double votes

evap/evaluation/models.py

@@ -509,9 +509,6 @@ def is_archived(self):
     def is_archiveable(self):
         return not self.is_archived and self.state in ["new", "published"]
 
-    def was_evaluated(self, request):
-        self.course_evaluated.send(sender=self.__class__, request=request, semester=self.semester)
-
     @property
     def final_grade_documents(self):
         from evap.grades.models import GradeDocument

evap/student/templates/student_vote.html

@@ -108,6 +108,12 @@ <h2>{{ course.name }} ({{ course.semester.name }})</h2>
         var form = $('#student-vote-form');
         form.submit(function (event) {
             event.preventDefault(); // don't use the default submission
+            var submitButton = $('#vote-submit-btn');
+            var originalText = submitButton.val();
+
+            submitButton.val("Submitting...");
+            submitButton.prop('disabled', true);
+
             $.ajax({
                 type: form.attr('method'),
                 url: form.attr('action'),
@@ -122,8 +128,10 @@ <h2>{{ course.name }} ({{ course.semester.name }})</h2>
                 },
                 error: function(data) {
                     // show a warning if the post isn't successful
-                    $('#vote-submit-btn').effect("highlight", {color:"#eb595a"}, 2000);
                     document.getElementById('submit-error-warning').style.display = 'block';
+                    submitButton.effect("highlight", {color:"#eb595a"}, 2000);
+                    submitButton.val(originalText);
+                    submitButton.prop('disabled', false);
                 }
             });
             return false;

evap/student/views.py

@@ -1,7 +1,7 @@
 from collections import OrderedDict
 
 from django.contrib import messages
-from django.core.exceptions import PermissionDenied
+from django.core.exceptions import PermissionDenied, SuspiciousOperation
 from django.db import transaction
 from django.shortcuts import get_object_or_404, redirect, render
 from django.utils.translation import ugettext as _
@@ -83,6 +83,13 @@ def vote(request, course_id):
 
     # all forms are valid, begin vote operation
     with transaction.atomic():
+        # add user to course.voters
+        # not using course.voters.add(request.user) since it fails silently when done twice.
+        # manually inserting like this gives us the 'created' return value and ensures at the database level that nobody votes twice.
+        __, created = course.voters.through.objects.get_or_create(userprofile_id=request.user.pk, course_id=course.pk)
+        if not created:  # vote already got recorded, bail out
+            raise SuspiciousOperation("A second vote has been received shortly after the first one.")
+
         for contribution, form_group in form_groups.items():
             for questionnaire_form in form_group:
                 questionnaire = questionnaire_form.questionnaire
@@ -102,10 +109,7 @@ def vote(request, course_id):
                             answer_counter.add_vote()
                             answer_counter.save()
 
-        # remember that the user voted already
-        course.voters.add(request.user)
-
-        course.was_evaluated(request)
+        course.course_evaluated.send(sender=Course, request=request, semester=course.semester)
 
     messages.success(request, _("Your vote was recorded."))
     return redirect('student:index')