Merge pull request #66 from ankitjavalkar/concurrent-login

Allow single user session active at any given time

6 files changed, 71 insertions, 3 deletions

diff --git a/online_test/settings.py b/online_test/settings.py
index e46b055..f96632b 100644
--- a/online_test/settings.py
+++ b/online_test/settings.py
@@ -46,6 +46,7 @@ MIDDLEWARE_CLASSES = (
     'django.middleware.common.CommonMiddleware',
     'django.middleware.csrf.CsrfViewMiddleware',
     'django.contrib.auth.middleware.AuthenticationMiddleware',
+    'yaksh.middleware.one_session_per_user.OneSessionPerUserMiddleware',
     'django.contrib.messages.middleware.MessageMiddleware',
     'django.middleware.clickjacking.XFrameOptionsMiddleware',
 )
@@ -85,3 +86,5 @@ USE_TZ = False
 # https://docs.djangoproject.com/en/1.6/howto/static-files/
 
 STATIC_URL = '/static/'
+
+LOGIN_URL = '/exam/login'
diff --git a/yaksh/middleware/__init__.py b/yaksh/middleware/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/yaksh/middleware/__init__.py
diff --git a/yaksh/middleware/one_session_per_user.py b/yaksh/middleware/one_session_per_user.py
new file mode 100644
index 0000000..92e888d
--- /dev/null
+++ b/yaksh/middleware/one_session_per_user.py
@@ -0,0 +1,35 @@
+from django.contrib.auth.models import User
+from django.contrib.sessions.models import Session
+
+from yaksh.models import ConcurrentUser
+
+
+class OneSessionPerUserMiddleware(object):
+    """
+    Middleware to handle multiple logins with same credentials
+        - Creates a Database entry to record the current user and active session key
+        - Checks if the current user has already been logged in. If True, the new session
+          key is stored with respect to the user and the old session key is deleted,
+          effectively terminating the older session for the same user.
+        - The concurrentuser attribute of the User model refers to the ConcurrentUser
+          model object and not the concurrent_user field due to behaviour described 
+          in the Documentation
+          Link: https://docs.djangoproject.com/en/1.5/topics/auth/customizing/#extending-the-existing-user-model)
+    """
+    def process_request(self, request):
+        if isinstance(request.user, User):
+            current_key = request.session.session_key
+            # 
+            # Documentation: 
+            # https://docs.djangoproject.com/en/1.5/topics/auth/customizing/#extending-the-existing-user-model
+            if hasattr(request.user, 'concurrentuser'):
+                active_key = request.user.concurrentuser.session_key
+                if active_key != current_key:
+                    Session.objects.filter(session_key=active_key).delete()
+                    request.user.concurrentuser.session_key = current_key
+                    request.user.concurrentuser.save()
+            else:
+                ConcurrentUser.objects.create(
+                    concurrent_user=request.user,
+                    session_key=current_key,
+                )
\ No newline at end of file
diff --git a/yaksh/models.py b/yaksh/models.py
index 62ac9bc..e7852d5 100644
--- a/yaksh/models.py
+++ b/yaksh/models.py
@@ -8,6 +8,12 @@ from taggit.managers import TaggableManager
 
 
 ###############################################################################
+class ConcurrentUser(models.Model):
+    concurrent_user = models.OneToOneField(User, null=False)
+    session_key = models.CharField(null=False, max_length=40)
+
+
+###############################################################################
 class Profile(models.Model):
     """Profile for a user to store roll number and other details."""
     user = models.OneToOneField(User)
diff --git a/yaksh/urls.py b/yaksh/urls.py
index a9f7a98..66159f0 100644
--- a/yaksh/urls.py
+++ b/yaksh/urls.py
@@ -47,6 +47,6 @@ urlpatterns = patterns('yaksh.views',
     url(r'^manage/designquestionpaper/manual/(?P<questionpaper_id>\d+)/$',\
                                                         'manual_questionpaper'),
     url(r'^ajax/questionpaper/(?P<query>.+)/$', 'ajax_questionpaper'),
-    url(r'^ajax/questions/filter/$', 'ajax_questions_filter'), ##@@
+    url(r'^ajax/questions/filter/$', 'ajax_questions_filter'),
 
 )
diff --git a/yaksh/views.py b/yaksh/views.py
index 41ce1bb..99e9f3b 100644
--- a/yaksh/views.py
+++ b/yaksh/views.py
@@ -12,6 +12,7 @@ from django.template import RequestContext
 from django.http import Http404
 from django.db.models import Sum
 from django.views.decorators.csrf import csrf_exempt
+from django.contrib.auth.decorators import login_required
 from taggit.models import Tag
 from itertools import chain
 import json
@@ -136,6 +137,7 @@ def user_register(request):
                                       context_instance=ci)
 
 
+@login_required
 def quizlist_user(request):
     """Show All Quizzes that is available to logged-in user."""
     user = request.user
@@ -164,7 +166,7 @@ def quizlist_user(request):
 
     return my_render_to_response("yaksh/quizzes_user.html", context)
 
-
+@login_required
 def intro(request, questionpaper_id):
     """Show introduction page before quiz starts"""
     user = request.user
@@ -253,7 +255,7 @@ def _check_previous_attempt(attempted_papers, already_attempted, attempt_number)
         else:
             return False, previous_attempt, next_attempt
 
-
+@login_required
 def results_user(request):
     """Show list of Results of Quizzes that is taken by logged-in user."""
     user = request.user
@@ -270,6 +272,7 @@ def results_user(request):
     return my_render_to_response("yaksh/results_user.html", context)
 
 
+@login_required
 def edit_quiz(request):
     """Edit the list of quizzes seleted by the user for editing."""
 
@@ -304,6 +307,7 @@ def edit_quiz(request):
     return my_redirect("/exam/manage/showquiz/")
 
 
+@login_required
 def edit_question(request):
     """Edit the list of questions selected by the user for editing."""
     user = request.user
@@ -341,6 +345,7 @@ def edit_question(request):
     return my_redirect("/exam/manage/questions")
 
 
+@login_required
 def add_question(request, question_id=None):
     """To add a new question in the database.
     Create a new question and store it."""
@@ -475,6 +480,7 @@ def add_question(request, question_id=None):
                                          context_instance=ci)
 
 
+@login_required
 def add_quiz(request, quiz_id=None):
     """To add a new quiz in the database.
     Create a new quiz and store it."""
@@ -540,6 +546,7 @@ def add_quiz(request, quiz_id=None):
                                          context_instance=ci)
 
 
+@login_required
 def show_all_questionpapers(request, questionpaper_id=None):
     user = request.user
     ci = RequestContext(request)
@@ -573,6 +580,7 @@ def show_all_questionpapers(request, questionpaper_id=None):
                                      context_instance=ci)
 
 
+@login_required
 def automatic_questionpaper(request, questionpaper_id=None):
     """Generate automatic question paper for a particular quiz"""
 
@@ -664,6 +672,7 @@ def automatic_questionpaper(request, questionpaper_id=None):
                                          context, context_instance=ci)
 
 
+@login_required
 def manual_questionpaper(request, questionpaper_id=None):
     user = request.user
     ci = RequestContext(request)
@@ -739,6 +748,7 @@ def manual_questionpaper(request, questionpaper_id=None):
                                          context, context_instance=ci)
 
 
+@login_required
 def prof_manage(request):
     """Take credentials of the user with professor/moderator
 rights/permissions and log in."""
@@ -788,6 +798,7 @@ def user_login(request):
                                      context_instance=ci)
 
 
+@login_required
 def start(request, attempt_num=None, questionpaper_id=None):
     """Check the user cedentials and if any quiz is available,
     start the exam."""
@@ -822,6 +833,7 @@ def start(request, attempt_num=None, questionpaper_id=None):
         user_dir = get_user_dir(user)
         return start(request, attempt_num, questionpaper_id)
 
+@login_required
 def get_questions(paper):
     '''
         Takes answerpaper as an argument. Returns the total questions as
@@ -848,6 +860,7 @@ def get_questions(paper):
     return questions, to_attempt, submitted
 
 
+@login_required
 def question(request, q_id, attempt_num, questionpaper_id, success_msg=None):
     """Check the credentials of the user and start the exam."""
 
@@ -890,6 +903,7 @@ def question(request, q_id, attempt_num, questionpaper_id, success_msg=None):
                                  context_instance=ci)
 
 
+@login_required
 def show_question(request, q_id, attempt_num, questionpaper_id, success_msg=None):
     """Show a question if possible."""
     user = request.user
@@ -927,6 +941,7 @@ def _save_skipped_answer(old_skipped, user_answer, paper, question):
         skipped_answer.save()
         paper.answers.add(skipped_answer)
 
+
 def check(request, q_id, attempt_num=None, questionpaper_id=None):
     """Checks the answers of the user for particular question"""
 
@@ -1109,6 +1124,7 @@ def quit(request, attempt_num=None, questionpaper_id=None):
                                  context_instance=RequestContext(request))
 
 
+@login_required
 def complete(request, reason=None, attempt_num=None, questionpaper_id=None):
     """Show a page to inform user that the quiz has been compeleted."""
 
@@ -1162,6 +1178,7 @@ def complete(request, reason=None, attempt_num=None, questionpaper_id=None):
         return my_redirect('/exam/')
 
 
+@login_required
 def monitor(request, questionpaper_id=None):
     """Monitor the progress of the papers taken so far."""
 
@@ -1192,6 +1209,7 @@ def monitor(request, questionpaper_id=None):
                                  context_instance=ci)
 
 
+@login_required
 def get_user_data(username):
     """For a given username, this returns a dictionary of important data
     related to the user including all the user's answers submitted.
@@ -1211,6 +1229,7 @@ def get_user_data(username):
     return data
 
 
+@login_required
 def show_all_users(request):
     """Shows all the users who have taken various exams/quiz."""
 
@@ -1224,6 +1243,7 @@ def show_all_users(request):
                                  context_instance=RequestContext(request))
 
 
+@login_required
 def show_all_quiz(request):
     """Generates a list of all the quizzes
     that are currently in the database."""
@@ -1306,6 +1326,7 @@ def ajax_questions_filter(request):
                                   {'questions': questions})
 
 
+@login_required
 def show_all_questions(request):
     """Show a list of all the questions currently in the databse."""
 
@@ -1385,6 +1406,7 @@ def show_all_questions(request):
                                      context_instance=ci)
 
 
+@login_required
 def user_data(request, username):
     """Render user data."""
 
@@ -1399,6 +1421,7 @@ def user_data(request, username):
                                  context_instance=RequestContext(request))
 
 
+@login_required
 def grade_user(request, username):
     """Present an interface with which we can easily grade a user's papers
     and update all their marks and also give comments for each paper.
@@ -1456,6 +1479,7 @@ def ajax_questionpaper(request, query):
                               {'questions': questions})
 
 
+@login_required
 def design_questionpaper(request):
     user = request.user
     ci = RequestContext(request)