import random
import string
import os
from datetime import datetime, timedelta
import collections
import csv
from django.http import HttpResponse, JsonResponse
from django.core.urlresolvers import reverse
from django.contrib.auth import login, logout, authenticate
from django.shortcuts import render_to_response, get_object_or_404, redirect
from django.template import RequestContext, Context, Template
from django.http import Http404
from django.db.models import Sum, Max, Q, F
from django.views.decorators.csrf import csrf_exempt
from django.contrib.auth.decorators import login_required
from django.contrib.auth.models import Group
from django.forms.models import inlineformset_factory
from django.utils import timezone
from django.core.validators import URLValidator
from django.core.exceptions import (
    MultipleObjectsReturned, ObjectDoesNotExist, ValidationError
)
from django.conf import settings
import pytz
from taggit.models import Tag
from itertools import chain
import json
import six
from textwrap import dedent
import zipfile
from markdown import Markdown
try:
    from StringIO import StringIO as string_io
except ImportError:
    from io import BytesIO as string_io
import re
# Local imports.
from yaksh.code_server import get_result as get_result_from_code_server
from yaksh.models import (
    Answer, AnswerPaper, AssignmentUpload, Course, FileUpload, FloatTestCase,
    HookTestCase, IntegerTestCase, McqTestCase, Profile,
    QuestionPaper, QuestionSet, Quiz, Question, StandardTestCase,
    StdIOBasedTestCase, StringTestCase, TestCase, User,
    get_model_class, FIXTURES_DIR_PATH, Lesson, LessonFile,
    LearningUnit, LearningModule,
    CourseStatus
)
from yaksh.forms import (
    UserRegisterForm, UserLoginForm, QuizForm, QuestionForm,
    RandomQuestionForm, QuestionFilterForm, CourseForm, ProfileForm,
    UploadFileForm, get_object_form, FileForm, QuestionPaperForm, LessonForm,
    LessonFileForm, LearningModuleForm, ExerciseForm
)
from yaksh.settings import SERVER_POOL_PORT, SERVER_HOST_NAME 
from .settings import URL_ROOT
from .file_utils import extract_files, is_csv
from .send_emails import send_user_mail, generate_activation_key, send_bulk_mail
from .decorators import email_verified, has_profile


def my_redirect(url):
    """An overridden redirect to deal with URL_ROOT-ing. See settings.py
    for details."""
    return redirect(URL_ROOT + url)


def my_render_to_response(template, context=None, **kwargs):
    """Overridden render_to_response.
    """
    if context is None:
        context = {'URL_ROOT': URL_ROOT}
    else:
        context['URL_ROOT'] = URL_ROOT
    return render_to_response(template, context, **kwargs)


def is_moderator(user):
    """Check if the user is having moderator rights"""
    if user.groups.filter(name='moderator').exists():
        return True


def add_to_group(users):
    """ add users to moderator group """
    group = Group.objects.get(name="moderator")
    for user in users:
        if not is_moderator(user):
            user.groups.add(group)

CSV_FIELDS = ['name', 'username', 'roll_number', 'institute', 'department',
    'questions', 'marks_obtained', 'out_of', 'percentage', 'status']


def get_html_text(md_text):
    """Takes markdown text and converts it to html"""
    return Markdown().convert(md_text)


@email_verified
def index(request, next_url=None):
    """The start page.
    """
    user = request.user
    if user.is_authenticated():
        if is_moderator(user):
            return my_redirect('/exam/manage/' if not next_url else next_url)
        return my_redirect("/exam/quizzes/" if not next_url else next_url)

    return my_redirect("/exam/login/")


def user_register(request):
    """ Register a new user.
    Create a user and corresponding profile and store roll_number also."""

    user = request.user
    ci = RequestContext(request)
    if user.is_authenticated():
        return my_redirect("/exam/quizzes/")
    context = {}
    if request.method == "POST":
        form = UserRegisterForm(request.POST)
        if form.is_valid():
            data = form.cleaned_data
            u_name, pwd, user_email, key = form.save()
            new_user = authenticate(username=u_name, password=pwd)
            login(request, new_user)
            if user_email and key:
                success, msg = send_user_mail(user_email, key)
                context = {'activation_msg': msg}
                return my_render_to_response(
                    'yaksh/activation_status.html', context
                )
            return index(request)
        else:
            return my_render_to_response('yaksh/register.html', {'form': form},
                                         context_instance=ci)
    else:
        form = UserRegisterForm()
        return my_render_to_response(
            'yaksh/register.html', {'form': form}, context_instance=ci
        )


def user_logout(request):
    """Show a page to inform user that the quiz has been compeleted."""
    logout(request)
    context = {'message': "You have been logged out successfully"}
    return my_render_to_response('yaksh/complete.html', context)


@login_required
@has_profile
@email_verified
def quizlist_user(request, enrolled=None, msg=None):
    """Show All Quizzes that is available to logged-in user."""
    user = request.user
    ci = RequestContext(request)

    if request.method == "POST":
        course_code = request.POST.get('course_code')
        hidden_courses = Course.objects.get_hidden_courses(code=course_code)
        courses = hidden_courses if hidden_courses else None
        title = 'Search'

    elif enrolled is not None:
        courses = user.students.all()
        title = 'Enrolled Courses'
    else:
        courses = Course.objects.filter(
            active=True, is_trial=False
        ).exclude(
           ~Q(requests=user), ~Q(rejected=user), hidden=True
        )
        title = 'All Courses'

    context = {'user': user, 'courses': courses, 'title': title,
               'msg': msg}

    return my_render_to_response(
        "yaksh/quizzes_user.html", context, context_instance=ci
    )


@login_required
@email_verified
def results_user(request):
    """Show list of Results of Quizzes that is taken by logged-in user."""
    user = request.user
    papers = AnswerPaper.objects.get_user_answerpapers(user)
    context = {'papers': papers}
    return my_render_to_response("yaksh/results_user.html", context)


@login_required
@email_verified
def add_question(request, question_id=None):
    user = request.user
    ci = RequestContext(request)
    test_case_type = None

    if question_id is None:
        question = Question(user=user)
        question.save()
    else:
        question = Question.objects.get(id=question_id)

    if request.method == "POST" and 'delete_files' in request.POST:
        remove_files_id = request.POST.getlist('clear')
        if remove_files_id:
            files = FileUpload.objects.filter(id__in=remove_files_id)
            for file in files:
                file.remove()

    if request.method == 'POST':
        qform = QuestionForm(request.POST, instance=question)
        fileform = FileForm(request.POST, request.FILES)
        files = request.FILES.getlist('file_field')
        extract_files_id = request.POST.getlist('extract')
        hide_files_id = request.POST.getlist('hide')
        if files:
            for file in files:
                FileUpload.objects.get_or_create(question=question, file=file)
        if extract_files_id:
            files = FileUpload.objects.filter(id__in=extract_files_id)
            for file in files:
                file.set_extract_status()
        if hide_files_id:
            files = FileUpload.objects.filter(id__in=hide_files_id)
            for file in files:
                file.toggle_hide_status()
        formsets = []
        for testcase in TestCase.__subclasses__():
            formset = inlineformset_factory(Question, testcase, extra=0,
                                            fields='__all__')
            formsets.append(formset(
                request.POST, request.FILES, instance=question
                )
            )
        files = request.FILES.getlist('file_field')
        uploaded_files = FileUpload.objects.filter(question_id=question.id)
        if qform.is_valid():
            question = qform.save(commit=False)
            question.user = user
            question.save()
            # many-to-many field save function used to save the tags
            qform.save_m2m()
            for formset in formsets:
                if formset.is_valid():
                    formset.save()
            test_case_type = request.POST.get('case_type', None)
        else:
            context = {
                'qform': qform,
                'fileform': fileform,
                'question': question,
                'formsets': formsets,
                'uploaded_files': uploaded_files
            }
            return my_render_to_response(
                "yaksh/add_question.html", context, context_instance=ci
            )

    qform = QuestionForm(instance=question)
    fileform = FileForm()
    uploaded_files = FileUpload.objects.filter(question_id=question.id)
    formsets = []
    for testcase in TestCase.__subclasses__():
        if test_case_type == testcase.__name__.lower():
            formset = inlineformset_factory(
                Question, testcase, extra=1, fields='__all__'
            )
        else:
            formset = inlineformset_factory(
                Question, testcase, extra=0, fields='__all__'
            )
        formsets.append(
            formset(
                instance=question,
                initial=[{'type': test_case_type}]
            )
        )
    context = {'qform': qform, 'fileform': fileform, 'question': question,
               'formsets': formsets, 'uploaded_files': uploaded_files}
    return my_render_to_response(
        "yaksh/add_question.html", context, context_instance=ci
    )


@login_required
@email_verified
def add_quiz(request, quiz_id=None, course_id=None):
    """To add a new quiz in the database.
    Create a new quiz and store it."""
    user = request.user
    ci = RequestContext(request)
    if not is_moderator(user):
        raise Http404('You are not allowed to view this course !')
    if quiz_id:
        quiz = get_object_or_404(Quiz, pk=quiz_id)
        if quiz.creator != user and not course_id:
            raise Http404('This quiz does not belong to you')
    else:
        quiz = None
    if course_id:
        course = get_object_or_404(Course, pk=course_id)
        if not course.is_creator(user) and not course.is_teacher(user):
            raise Http404('This quiz does not belong to you')

    context = {}
    if request.method == "POST":
        form = QuizForm(request.POST, instance=quiz)
        if form.is_valid():
            if quiz is None:
                form.instance.creator = user
            form.save()
            if not course_id:
                return my_redirect("/exam/manage/courses/all_quizzes/")
            else:
                return my_redirect("/exam/manage/courses/")

    else:
        form = QuizForm(instance=quiz)
        context["course_id"] = course_id
        context["quiz"] = quiz
    context["form"] = form
    return my_render_to_response(
        'yaksh/add_quiz.html', context, context_instance=ci
    )


@login_required
@email_verified
def add_exercise(request, quiz_id=None, course_id=None):
    user = request.user
    ci = RequestContext(request)
    if not is_moderator(user):
        raise Http404('You are not allowed to view this course !')
    if quiz_id:
        quiz = get_object_or_404(Quiz, pk=quiz_id)
        if quiz.creator != user and not course_id:
            raise Http404('This quiz does not belong to you')
    else:
        quiz = None
    if course_id:
        course = get_object_or_404(Course, pk=course_id)
        if not course.is_creator(user) and not course.is_teacher(user):
            raise Http404('This Course does not belong to you')

    context = {}
    if request.method == "POST":
        form = ExerciseForm(request.POST, instance=quiz)
        if form.is_valid():
            if quiz is None:
                form.instance.creator = user
            quiz = form.save(commit=False)
            quiz.is_exercise = True
            quiz.time_between_attempts = 0
            quiz.weightage = 0
            quiz.allow_skip = False
            quiz.attempts_allowed = -1
            quiz.duration = 1000
            quiz.pass_criteria = 0
            quiz.save()

            if not course_id:
                return my_redirect("/exam/manage/courses/all_quizzes/")
            else:
                return my_redirect("/exam/manage/courses/")

    else:
        form = ExerciseForm(instance=quiz)
        context["exercise"] = quiz
        context["course_id"] = course_id
    context["form"] = form
    return my_render_to_response(
        'yaksh/add_exercise.html', context, context_instance=ci
    )


@login_required
@has_profile
@email_verified
def prof_manage(request, msg=None):
    """Take credentials of the user with professor/moderator
    rights/permissions and log in."""
    user = request.user
    ci = RequestContext(request)
    if not user.is_authenticated():
        return my_redirect('/exam/login')
    if not is_moderator(user):
        return my_redirect('/exam/')
    courses = Course.objects.filter(creator=user, is_trial=False)

    trial_paper = AnswerPaper.objects.filter(
        user=user, question_paper__quiz__is_trial=True,
        course__is_trial=True
    )
    if request.method == "POST":
        delete_paper = request.POST.getlist('delete_paper')
        for answerpaper_id in delete_paper:
            answerpaper = AnswerPaper.objects.get(id=answerpaper_id)
            qpaper = answerpaper.question_paper
            answerpaper.course.remove_trial_modules()
            answerpaper.course.delete()
            if qpaper.quiz.is_trial:
                qpaper.quiz.delete()
            else:
                if qpaper.answerpaper_set.count() == 1:
                    qpaper.quiz.delete()
                else:
                    answerpaper.delete()
    context = {'user': user, 'courses': courses,
               'trial_paper': trial_paper, 'msg': msg
               }
    return my_render_to_response(
        'yaksh/moderator_dashboard.html', context, context_instance=ci
    )


def user_login(request):
    """Take the credentials of the user and log the user in."""

    user = request.user
    ci = RequestContext(request)
    context = {}
    if user.is_authenticated():
        return index(request)

    next_url = request.GET.get('next')

    if request.method == "POST":
        form = UserLoginForm(request.POST)
        if form.is_valid():
            user = form.cleaned_data
            login(request, user)
            return index(request, next_url)
        else:
            context = {"form": form}

    else:
        form = UserLoginForm()
        context = {"form": form}

    return my_render_to_response('yaksh/login.html', context,
                                 context_instance=ci)


@login_required
@email_verified
def start(request, questionpaper_id=None, attempt_num=None, course_id=None,
          module_id=None):
    """Check the user cedentials and if any quiz is available,
    start the exam."""
    user = request.user
    ci = RequestContext(request)
    # check conditions
    try:
        quest_paper = QuestionPaper.objects.get(id=questionpaper_id)
    except QuestionPaper.DoesNotExist:
        msg = 'Quiz not found, please contact your '\
            'instructor/administrator.'
        if is_moderator(user):
            return prof_manage(request, msg=msg)
        return view_module(request, module_id=module_id, course_id=course_id,
                           msg=msg)
    if not quest_paper.has_questions():
        msg = 'Quiz does not have Questions, please contact your '\
            'instructor/administrator.'
        if is_moderator(user):
            return prof_manage(request, msg=msg)
        return view_module(request, module_id=module_id, course_id=course_id,
                           msg=msg)
    course = Course.objects.get(id=course_id)
    learning_module = course.learning_module.get(id=module_id)
    learning_unit = learning_module.learning_unit.get(quiz=quest_paper.quiz.id)

    # unit module prerequiste check
    if learning_module.has_prerequisite():
        if not learning_module.is_prerequisite_passed(user, course):
            msg = "You have not completed the module previous to {0}".format(
                learning_module.name)
            return course_modules(request, course_id, msg)

    # update course status with current unit
    _update_unit_status(course_id, user, learning_unit)

    # is user enrolled in the course
    if not course.is_enrolled(user):
        msg = 'You are not enrolled in {0} course'.format(course.name)
        if is_moderator(user):
            return prof_manage(request, msg=msg)
        return quizlist_user(request, msg=msg)

    # if course is active and is not expired
    if not course.active or not course.is_active_enrollment():
        msg = "{0} is either expired or not active".format(course.name)
        if is_moderator(user):
            return prof_manage(request, msg=msg)
        return quizlist_user(request, msg=msg)

    # is quiz is active and is not expired
    if quest_paper.quiz.is_expired() or not quest_paper.quiz.active:
        msg = "{0} is either expired or not active".format(
            quest_paper.quiz.description)
        if is_moderator(user):
            return prof_manage(request, msg=msg)
        return view_module(request, module_id=module_id, course_id=course_id,
                           msg=msg)

    # prerequisite check and passing criteria for quiz
    if learning_unit.has_prerequisite():
        if not learning_unit.is_prerequisite_passed(
                user, learning_module, course):
            msg = "You have not completed the previous Lesson/Quiz/Exercise"
            if is_moderator(user):
                return prof_manage(request, msg=msg)
            return view_module(request, module_id=module_id,
                               course_id=course_id, msg=msg)

    # if any previous attempt
    last_attempt = AnswerPaper.objects.get_user_last_attempt(
        quest_paper, user, course_id)
    if last_attempt and last_attempt.is_attempt_inprogress():
        return show_question(
            request, last_attempt.current_question(), last_attempt,
            course_id=course_id, module_id=module_id,
            previous_question=last_attempt.current_question()
        )
    # allowed to start
    if not quest_paper.can_attempt_now(user, course_id):
        msg = "You cannot attempt {0} quiz more than {1} time(s)".format(
            quest_paper.quiz.description, quest_paper.quiz.attempts_allowed)
        if is_moderator(user):
            return prof_manage(request, msg=msg)
        return view_module(request, module_id=module_id, course_id=course_id,
                           msg=msg)
    if not last_attempt:
        attempt_number = 1
    else:
        attempt_number = last_attempt.attempt_number + 1
    if attempt_num is None and not quest_paper.quiz.is_exercise:
        context = {
            'user': user,
            'questionpaper': quest_paper,
            'attempt_num': attempt_number,
            'course': course,
            'module': learning_module,
        }
        if is_moderator(user):
            context["status"] = "moderator"
        return my_render_to_response('yaksh/intro.html', context,
                                     context_instance=ci)
    else:
        ip = request.META['REMOTE_ADDR']
        if not hasattr(user, 'profile'):
            msg = 'You do not have a profile and cannot take the quiz!'
            raise Http404(msg)
        new_paper = quest_paper.make_answerpaper(user, ip, attempt_number,
                                                 course_id)
        if new_paper.status ==  'inprogress':
            return show_question(request, new_paper.current_question(),
                                 new_paper, course_id=course_id,
                                 module_id=module_id, previous_question=None
                                 )
        else:
            msg = 'You have already finished the quiz!'
            raise Http404(msg)

@login_required
@email_verified
def show_question(request, question, paper, error_message=None, notification=None,
                  course_id=None, module_id=None, previous_question=None):
    """Show a question if possible."""
    user = request.user
    quiz = paper.question_paper.quiz
    quiz_type = 'Exam'
    can_skip = False
    if previous_question:
        delay_time = paper.time_left_on_question(previous_question)
    else:
        delay_time = paper.time_left_on_question(question)

    if previous_question and quiz.is_exercise:
        if delay_time <= 0 or previous_question in paper.questions_answered.all():
            can_skip = True
        question = previous_question
    if not question:
        msg = 'Congratulations!  You have successfully completed the quiz.'
        return complete(
            request, msg, paper.attempt_number, paper.question_paper.id,
            course_id=course_id, module_id=module_id
        )
    if not quiz.active:
        reason = 'The quiz has been deactivated!'
        return complete(
            request, reason, paper.attempt_number, paper.question_paper.id,
            course_id=course_id, module_id=module_id
        )
    if not quiz.is_exercise:
        if paper.time_left() <= 0:
            reason = 'Your time is up!'
            return complete(
                request, reason, paper.attempt_number, paper.question_paper.id,
                course_id, module_id=module_id
            )
    else:
        quiz_type = 'Exercise'
    if question in paper.questions_answered.all():
        notification = (
            'You have already attempted this question successfully'
            if question.type == "code" else
            'You have already attempted this question'
        )
    test_cases = question.get_test_cases()
    files = FileUpload.objects.filter(question_id=question.id, hide=False)
    course = Course.objects.get(id=course_id)
    module = course.learning_module.get(id=module_id)
    all_modules = course.get_learning_modules()
    context = {
        'question': question,
        'paper': paper,
        'quiz': quiz,
        'error_message': error_message,
        'test_cases': test_cases,
        'files': files,
        'notification': notification,
        'last_attempt': question.snippet.encode('unicode-escape'),
        'course': course,
        'module': module,
        'can_skip': can_skip,
        'delay_time': delay_time,
        'quiz_type': quiz_type,
        'all_modules': all_modules
    }
    answers = paper.get_previous_answers(question)
    if answers:
        last_attempt = answers[0].answer
        if last_attempt:
            context['last_attempt'] = last_attempt.encode('unicode-escape')
    ci = RequestContext(request)
    return my_render_to_response('yaksh/question.html', context,
                                 context_instance=ci)


@login_required
@email_verified
def skip(request, q_id, next_q=None, attempt_num=None, questionpaper_id=None,
         course_id=None, module_id=None):
    user = request.user
    paper = get_object_or_404(
        AnswerPaper, user=request.user, attempt_number=attempt_num,
        question_paper=questionpaper_id, course_id=course_id
    )
    question = get_object_or_404(Question, pk=q_id)

    if paper.question_paper.quiz.is_exercise:
        paper.start_time = timezone.now()
        paper.save()

    if request.method == 'POST' and question.type == 'code':
        if not paper.answers.filter(question=question, correct=True).exists():
            user_code = request.POST.get('answer')
            new_answer = Answer(
                question=question, answer=user_code,
                correct=False, skipped=True,
                error=json.dumps([])
            )
            new_answer.save()
            paper.answers.add(new_answer)
    if next_q is not None:
        next_q = get_object_or_404(Question, pk=next_q)
    else:
        next_q = paper.next_question(q_id)
    return show_question(request, next_q, paper, course_id=course_id,
                         module_id=module_id)


@login_required
@email_verified
def check(request, q_id, attempt_num=None, questionpaper_id=None,
          course_id=None, module_id=None):
    """Checks the answers of the user for particular question"""
    user = request.user
    paper = get_object_or_404(
        AnswerPaper,
        user=request.user,
        attempt_number=attempt_num,
        question_paper=questionpaper_id,
        course_id=course_id
    )
    current_question = get_object_or_404(Question, pk=q_id)

    if request.method == 'POST':
        # Add the answer submitted, regardless of it being correct or not.
        if current_question.type == 'mcq':
            user_answer = request.POST.get('answer')
        elif current_question.type == 'integer':
            try:
                user_answer = int(request.POST.get('answer'))
            except ValueError:
                msg = "Please enter an Integer Value"
                return show_question(
                    request, current_question, paper, notification=msg,
                    course_id=course_id, module_id=module_id,
                    previous_question=current_question
                )
        elif current_question.type == 'float':
            try:
                user_answer = float(request.POST.get('answer'))
            except ValueError:
                msg = "Please enter a Float Value"
                return show_question(request, current_question,
                                     paper, notification=msg,
                                     course_id=course_id, module_id=module_id,
                                     previous_question=current_question)
        elif current_question.type == 'string':
            user_answer = str(request.POST.get('answer'))

        elif current_question.type == 'mcc':
            user_answer = request.POST.getlist('answer')
        elif current_question.type == 'upload':
            # if time-up at upload question then the form is submitted without
            # validation
            assignment_filename = request.FILES.getlist('assignment')
            if not assignment_filename:
                msg = "Please upload assignment file"
                return show_question(
                    request, current_question, paper, notification=msg,
                    course_id=course_id, module_id=module_id,
                    previous_question=current_question
                )
            for fname in assignment_filename:
                fname._name = fname._name.replace(" ","_")
                assignment_files = AssignmentUpload.objects.filter(
                            assignmentQuestion=current_question,
                            assignmentFile__icontains=fname, user=user,
                            question_paper=questionpaper_id)
                if assignment_files.exists():
                    assign_file = assignment_files.get(
                            assignmentQuestion=current_question,
                            assignmentFile__icontains=fname, user=user,
                            question_paper=questionpaper_id)
                    if os.path.exists(assign_file.assignmentFile.path):
                        os.remove(assign_file.assignmentFile.path)
                    assign_file.delete()
                AssignmentUpload.objects.create(
                    user=user, assignmentQuestion=current_question,
                    assignmentFile=fname, question_paper_id=questionpaper_id
                )
            user_answer = 'ASSIGNMENT UPLOADED'
            if not current_question.grade_assignment_upload:
                new_answer = Answer(
                    question=current_question, answer=user_answer,
                    correct=False, error=json.dumps([])
                )
                new_answer.save()
                paper.answers.add(new_answer)
                next_q = paper.add_completed_question(current_question.id)
                return show_question(request, next_q, paper,
                                     course_id=course_id, module_id=module_id,
                                     previous_question=current_question)
        else:
            user_answer = request.POST.get('answer')
        if not user_answer:
            msg = "Please submit a valid answer."
            return show_question(
                request, current_question, paper, notification=msg,
                course_id=course_id, module_id=module_id,
                previous_question=current_question
            )
        if current_question in paper.get_questions_answered()\
         and current_question.type not in ['code', 'upload']:
            new_answer = paper.get_latest_answer(current_question.id)
            new_answer.answer = user_answer
            new_answer.correct = False
        else:
            new_answer = Answer(
            question=current_question, answer=user_answer,
            correct=False, error=json.dumps([])
        )
        new_answer.save()
        uid = new_answer.id
        paper.answers.add(new_answer)
        # If we were not skipped, we were asked to check.  For any non-mcq
        # questions, we obtain the results via XML-RPC with the code executed
        # safely in a separate process (the code_server.py) running as nobody.
        json_data = current_question.consolidate_answer_data(user_answer, user) \
            if current_question.type == 'code' or \
            current_question.type == 'upload' else None
        result = paper.validate_answer(
            user_answer, current_question, json_data, uid
        )
        if current_question.type in ['code', 'upload']:
            if paper.time_left() <= 0 and not paper.question_paper.quiz.is_exercise:
                url = '{0}:{1}'.format(SERVER_HOST_NAME, SERVER_POOL_PORT)
                result_details = get_result_from_code_server(url, uid, block=True)
                result = json.loads(result_details.get('result'))
                next_question, error_message, paper = _update_paper(request, uid,
                        result)
                return show_question(request, next_question, paper,
                                     error_message, course_id=course_id,
                                     module_id=module_id,
                                     previous_question=current_question)
            else:
                return JsonResponse(result)
        else:
            next_question, error_message, paper = _update_paper(request, uid, result)
            return show_question(request, next_question, paper, error_message,
                                 course_id=course_id, module_id=module_id,
                                 previous_question=current_question)
    else:
        return show_question(request, current_question, paper,
                             course_id=course_id, module_id=module_id,
                             previous_question=current_question)


@csrf_exempt
def get_result(request, uid, course_id, module_id):
    result = {}
    url = '{0}:{1}'.format(SERVER_HOST_NAME, SERVER_POOL_PORT)
    result_state = get_result_from_code_server(url, uid)
    result['status'] = result_state.get('status')
    if result['status'] == 'done':
        result = json.loads(result_state.get('result'))
        template_path = os.path.join(*[os.path.dirname(__file__),
                                       'templates', 'yaksh',
                                       'error_template.html'
                                       ]
                                     )
        next_question, error_message, paper = _update_paper(request, uid,
                                                            result
                                                            )
        answer = Answer.objects.get(id=uid)
        current_question = answer.question
        if result.get('success'):
            return show_question(request, next_question, paper, error_message,
                                 course_id=course_id, module_id=module_id,
                                 previous_question=current_question)
        else:
            with open(template_path) as f:
                template_data = f.read()
                template = Template(template_data)
                context = Context({"error_message": result.get('error')})
                render_error = template.render(context)
                result["error"] = render_error
    return JsonResponse(result)


def _update_paper(request, uid, result):
    new_answer = Answer.objects.get(id=uid)
    current_question = new_answer.question
    paper = new_answer.answerpaper_set.first()

    if result.get('success'):
        new_answer.marks = (current_question.points * result['weight'] /
            current_question.get_maximum_test_case_weight()) \
            if current_question.partial_grading and \
            current_question.type == 'code' or current_question.type == 'upload' \
            else current_question.points
        new_answer.correct = result.get('success')
        error_message = None
        new_answer.error = json.dumps(result.get('error'))
        next_question = paper.add_completed_question(current_question.id)
    else:
        new_answer.marks = (current_question.points * result['weight'] /
            current_question.get_maximum_test_case_weight()) \
            if current_question.partial_grading and \
            current_question.type == 'code' or current_question.type == 'upload' \
            else 0
        error_message = result.get('error') if current_question.type == 'code' \
            or current_question.type == 'upload' else None
        new_answer.error = json.dumps(result.get('error'))
        next_question = current_question if current_question.type == 'code' \
            or current_question.type == 'upload' \
            else paper.add_completed_question(current_question.id)
    new_answer.save()
    paper.update_marks('inprogress')
    paper.set_end_time(timezone.now())
    return next_question, error_message, paper


@login_required
@email_verified
def quit(request, reason=None, attempt_num=None, questionpaper_id=None,
         course_id=None, module_id=None):
    """Show the quit page when the user logs out."""
    paper = AnswerPaper.objects.get(user=request.user,
                                    attempt_number=attempt_num,
                                    question_paper=questionpaper_id,
                                    course_id=course_id)
    context = {'paper': paper, 'message': reason, 'course_id': course_id,
               'module_id': module_id}
    return my_render_to_response('yaksh/quit.html', context,
                                 context_instance=RequestContext(request))


@login_required
@email_verified
def complete(request, reason=None, attempt_num=None, questionpaper_id=None,
             course_id=None, module_id=None):
    """Show a page to inform user that the quiz has been compeleted."""
    user = request.user
    if questionpaper_id is None:
        message = reason or "An Unexpected Error occurred. Please contact your '\
            'instructor/administrator.'"
        context = {'message': message}
        return my_render_to_response('yaksh/complete.html', context)
    else:
        q_paper = QuestionPaper.objects.get(id=questionpaper_id)
        paper = AnswerPaper.objects.get(
            user=user, question_paper=q_paper,
            attempt_number=attempt_num,
            course_id=course_id
        )
        course = Course.objects.get(id=course_id)
        learning_module = course.learning_module.get(id=module_id)
        learning_unit = learning_module.learning_unit.get(quiz=q_paper.quiz)

        paper.update_marks()
        paper.set_end_time(timezone.now())
        message = reason or "Quiz has been submitted"
        context = {'message': message, 'paper': paper,
                   'module_id': learning_module.id,
                   'course_id': course_id, 'learning_unit': learning_unit}
        if is_moderator(user):
            context['user'] = "moderator"
        return my_render_to_response('yaksh/complete.html', context)


@login_required
@email_verified
def add_course(request, course_id=None):
    user = request.user
    ci = RequestContext(request)
    if course_id:
        course = Course.objects.get(id=course_id)
        if not course.is_creator(user) and not course.is_teacher(user):
            raise Http404("You are not allowed to view this course")
    else:
        course = None
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page')
    if request.method == 'POST':
        form = CourseForm(request.POST, instance=course)
        if form.is_valid():
            new_course = form.save(commit=False)
            if course_id is None:
                new_course.creator = user
            new_course.save()
            return my_redirect('/exam/manage/courses')
        else:
            return my_render_to_response(
                'yaksh/add_course.html', {'form': form}, context_instance=ci
            )
    else:
        form = CourseForm(instance=course)
        return my_render_to_response(
            'yaksh/add_course.html', {'form': form}, context_instance=ci
        )


@login_required
@email_verified
def enroll_request(request, course_id):
    user = request.user
    ci = RequestContext(request)
    course = get_object_or_404(Course, pk=course_id)
    if not course.is_active_enrollment() and course.hidden:
        msg = (
            'Unable to add enrollments for this course, please contact your '
            'instructor/administrator.'
        )
        return complete(request, msg, attempt_num=None, questionpaper_id=None)

    course.request(user)
    if is_moderator(user):
        return my_redirect('/exam/manage/courses')
    else:
        return my_redirect('/exam/quizzes/')


@login_required
@email_verified
def self_enroll(request, course_id):
    user = request.user
    ci = RequestContext(request)
    course = get_object_or_404(Course, pk=course_id)
    if course.is_self_enroll():
        was_rejected = False
        course.enroll(was_rejected, user)
    if is_moderator(user):
        return my_redirect('/exam/manage/')
    else:
        return my_redirect('/exam/quizzes/')


@login_required
@email_verified
def courses(request):
    user = request.user
    ci = RequestContext(request)
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page')
    courses = Course.objects.filter(
        creator=user, is_trial=False).order_by('-active', '-id')
    allotted_courses = Course.objects.filter(
        teachers=user, is_trial=False).order_by('-active', '-id')
    context = {'courses': courses, "allotted_courses": allotted_courses,
               "type": "courses"}
    return my_render_to_response('yaksh/courses.html', context,
                                 context_instance=ci)


@login_required
@email_verified
def course_detail(request, course_id):
    user = request.user
    ci = RequestContext(request)

    if not is_moderator(user):
        raise Http404('You are not allowed to view this page')

    course = get_object_or_404(Course, pk=course_id)
    if not course.is_creator(user) and not course.is_teacher(user):
        raise Http404('This course does not belong to you')

    return my_render_to_response(
        'yaksh/course_detail.html', {'course': course}, context_instance=ci
    )


@login_required
@email_verified
def enroll(request, course_id, user_id=None, was_rejected=False):
    user = request.user
    ci = RequestContext(request)
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page')

    course = get_object_or_404(Course, pk=course_id)
    if not course.is_active_enrollment():
        msg = (
            'Enrollment for this course has been closed,'
            ' please contact your '
            'instructor/administrator.'
        )
        return complete(request, msg, attempt_num=None, questionpaper_id=None)

    if not course.is_creator(user) and not course.is_teacher(user):
        raise Http404('This course does not belong to you')

    if request.method == 'POST':
        enroll_ids = request.POST.getlist('check')
    else:
        enroll_ids = [user_id]
    if not enroll_ids:
        return my_render_to_response(
            'yaksh/course_detail.html', {'course': course}, context_instance=ci
        )
    users = User.objects.filter(id__in=enroll_ids)
    course.enroll(was_rejected, *users)
    return course_detail(request, course_id)


@login_required
@email_verified
def send_mail(request, course_id, user_id=None):
    user = request.user
    ci = RequestContext(request)
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page')

    course = get_object_or_404(Course, pk=course_id)
    if not course.is_creator(user) and not course.is_teacher(user):
        raise Http404('This course does not belong to you')

    message = None
    if request.method == 'POST':
        user_ids = request.POST.getlist('check')
        if request.POST.get('send_mail') == 'send_mail':
            users = User.objects.filter(id__in=user_ids)
            recipients = [student.email for student in users]
            email_body = request.POST.get('body')
            subject = request.POST.get('subject')
            attachments = request.FILES.getlist('email_attach')
            message = send_bulk_mail(
                subject, email_body, recipients, attachments
            )
    context = {
        'course': course, 'message': message,
        'state': 'mail'
    }
    return my_render_to_response(
        'yaksh/course_detail.html', context, context_instance=ci
    )


@login_required
@email_verified
def reject(request, course_id, user_id=None, was_enrolled=False):
    user = request.user
    ci = RequestContext(request)
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page')

    course = get_object_or_404(Course, pk=course_id)
    if not course.is_creator(user) and not course.is_teacher(user):
        raise Http404('This course does not belong to you')

    if request.method == 'POST':
        reject_ids = request.POST.getlist('check')
    else:
        reject_ids = [user_id]
    if not reject_ids:
        message = "Please select atleast one User"
        return my_render_to_response(
            'yaksh/course_detail.html', {'course': course, 'message': message},
            context_instance=ci
        )
    users = User.objects.filter(id__in=reject_ids)
    course.reject(was_enrolled, *users)
    return course_detail(request, course_id)


@login_required
@email_verified
def toggle_course_status(request, course_id):
    user = request.user
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page')

    course = get_object_or_404(Course, pk=course_id)
    if not course.is_creator(user) and not course.is_teacher(user):
        raise Http404('This course does not belong to you')

    if course.active:
        course.deactivate()
    else:
        course.activate()
    course.save()
    return my_redirect("/exam/manage/courses")


@login_required
@email_verified
def show_statistics(request, questionpaper_id, attempt_number=None,
                    course_id=None):
    user = request.user
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page')
    attempt_numbers = AnswerPaper.objects.get_attempt_numbers(
        questionpaper_id, course_id)
    quiz = get_object_or_404(QuestionPaper, pk=questionpaper_id).quiz
    if attempt_number is None:
        context = {'quiz': quiz, 'attempts': attempt_numbers,
                   'questionpaper_id': questionpaper_id,
                   'course_id': course_id}
        return my_render_to_response('yaksh/statistics_question.html', context,
                                     context_instance=RequestContext(request))
    total_attempt = AnswerPaper.objects.get_count(questionpaper_id,
                                                  attempt_number,
                                                  course_id)
    if not AnswerPaper.objects.has_attempt(questionpaper_id, attempt_number,
                                           course_id):
        return my_redirect('/exam/manage/')
    question_stats = AnswerPaper.objects.get_question_statistics(
        questionpaper_id, attempt_number, course_id
    )
    context = {'question_stats': question_stats, 'quiz': quiz,
               'questionpaper_id': questionpaper_id,
               'attempts': attempt_numbers, 'total': total_attempt,
               'course_id': course_id}
    return my_render_to_response('yaksh/statistics_question.html', context,
                                 context_instance=RequestContext(request))


@login_required
@email_verified
def monitor(request, quiz_id=None, course_id=None):
    """Monitor the progress of the papers taken so far."""

    user = request.user
    ci = RequestContext(request)
    if not user.is_authenticated() or not is_moderator(user):
        raise Http404('You are not allowed to view this page!')

    if quiz_id is None:
        course_details = Course.objects.filter(
            Q(creator=user) | Q(teachers=user),
            is_trial=False
        ).distinct()
        context = {
            "papers": [], "course_details": course_details,
            "msg": "Monitor"
        }
        return my_render_to_response(
            'yaksh/monitor.html', context, context_instance=ci
        )
    # quiz_id is not None.
    try:
        quiz = get_object_or_404(Quiz, id=quiz_id)
        course = get_object_or_404(Course, id=course_id)
        if not course.is_creator(user) and not course.is_teacher(user):
            raise Http404('This course does not belong to you')
        q_paper = QuestionPaper.objects.filter(quiz__is_trial=False,
                                               quiz_id=quiz_id).distinct()
    except (QuestionPaper.DoesNotExist, Course.DoesNotExist):
        papers = []
        q_paper = None
        latest_attempts = []
        attempt_numbers = []
    else:
        if q_paper:
            attempt_numbers = AnswerPaper.objects.get_attempt_numbers(
                q_paper.last().id, course.id)
        else:
            attempt_numbers = []
        latest_attempts = []
        papers = AnswerPaper.objects.filter(question_paper=q_paper,
                                            course_id=course_id).order_by(
            'user__profile__roll_number'
        )
        users = papers.values_list('user').distinct()
        for auser in users:
            last_attempt = papers.filter(user__in=auser).aggregate(
                last_attempt_num=Max('attempt_number')
            )
            latest_attempts.append(
                papers.get(
                    user__in=auser,
                    attempt_number=last_attempt['last_attempt_num']
                )
            )
    csv_fields = CSV_FIELDS
    context = {
        "papers": papers,
        "quiz": quiz,
        "msg": "Quiz Results",
        "latest_attempts": latest_attempts,
        "csv_fields": csv_fields,
        "attempt_numbers": attempt_numbers,
        "course": course
    }
    return my_render_to_response('yaksh/monitor.html', context,
                                 context_instance=ci)


@csrf_exempt
def ajax_questions_filter(request):
    """Ajax call made when filtering displayed questions."""

    user = request.user
    filter_dict = {"user_id": user.id, "active": True}
    question_type = request.POST.get('question_type')
    marks = request.POST.get('marks')
    language = request.POST.get('language')

    if question_type != "select":
        filter_dict['type'] = str(question_type)

    if marks != "select":
        filter_dict['points'] = marks

    if language != "select":
        filter_dict['language'] = str(language)
    questions = list(Question.objects.filter(**filter_dict))

    return my_render_to_response(
        'yaksh/ajax_question_filter.html', {'questions': questions}
    )


def _get_questions(user, question_type, marks):
    if question_type is None and marks is None:
        return None
    if question_type:
        questions = Question.objects.filter(
            type=question_type,
            user=user,
            active=True
        )
        if marks:
            questions = questions.filter(points=marks)
    return questions


def _remove_already_present(questionpaper_id, questions):
    if questionpaper_id is None:
        return questions
    questionpaper = QuestionPaper.objects.get(pk=questionpaper_id)
    questions = questions.exclude(
            id__in=questionpaper.fixed_questions.values_list('id', flat=True))
    for random_set in questionpaper.random_questions.all():
        questions = questions.exclude(
                id__in=random_set.questions.values_list('id', flat=True))
    return questions


@login_required
@email_verified
def design_questionpaper(request, quiz_id, questionpaper_id=None,
                         course_id=None):
    user = request.user

    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')
    if quiz_id:
        quiz = get_object_or_404(Quiz, pk=quiz_id)
        if quiz.creator != user and not course_id:
            raise Http404('This quiz does not belong to you')
    if course_id:
        course = get_object_or_404(Course, pk=course_id)
        if not course.is_creator(user) and not course.is_teacher(user):
            raise Http404('This Course does not belong to you')

    filter_form = QuestionFilterForm(user=user)
    questions = None
    marks = None
    state = None
    if questionpaper_id is None:
        question_paper = QuestionPaper.objects.get_or_create(quiz_id=quiz_id)[0]
    else:
        question_paper = get_object_or_404(QuestionPaper, id=questionpaper_id,
                                           quiz_id=quiz_id)
    qpaper_form = QuestionPaperForm(instance=question_paper)

    if request.method == 'POST':

        filter_form = QuestionFilterForm(request.POST, user=user)
        qpaper_form = QuestionPaperForm(request.POST, instance=question_paper)
        question_type = request.POST.get('question_type', None)
        marks = request.POST.get('marks', None)
        state = request.POST.get('is_active', None)

        if 'add-fixed' in request.POST:
            question_ids = request.POST.get('checked_ques', None)
            if question_paper.fixed_question_order:
                ques_order = question_paper.fixed_question_order.split(",") +\
                            question_ids.split(",")
                questions_order = ",".join(ques_order)
            else:
                questions_order = question_ids
            questions = Question.objects.filter(id__in=question_ids.split(','))
            question_paper.fixed_question_order = questions_order
            question_paper.save()
            question_paper.fixed_questions.add(*questions)

        if 'remove-fixed' in request.POST:
            question_ids = request.POST.getlist('added-questions', None)
            if question_paper.fixed_question_order:
                que_order = question_paper.fixed_question_order.split(",")
                for qid in question_ids:
                    que_order.remove(qid)
                if que_order:
                    question_paper.fixed_question_order = ",".join(que_order)
                else:
                    question_paper.fixed_question_order = ""
                question_paper.save()
            question_paper.fixed_questions.remove(*question_ids)

        if 'add-random' in request.POST:
            question_ids = request.POST.getlist('random_questions', None)
            num_of_questions = request.POST.get('num_of_questions', 1)
            if question_ids and marks:
                random_set = QuestionSet(marks=marks, num_questions=num_of_questions)
                random_set.save()
                for question in Question.objects.filter(id__in=question_ids):
                    random_set.questions.add(question)
                question_paper.random_questions.add(random_set)

        if 'remove-random' in request.POST:
            random_set_ids = request.POST.getlist('random_sets', None)
            question_paper.random_questions.remove(*random_set_ids)

        if 'save' in request.POST or 'back' in request.POST:
            qpaper_form.save()
            return my_redirect('/exam/manage/courses/all_quizzes/')

        if marks:
            questions = _get_questions(user, question_type, marks)
            questions = _remove_already_present(questionpaper_id, questions)

        question_paper.update_total_marks()
        question_paper.save()
    random_sets = question_paper.random_questions.all()
    fixed_questions = question_paper.get_ordered_questions()
    context = {
        'qpaper_form': qpaper_form,
        'filter_form': filter_form,
        'qpaper': question_paper,
        'questions': questions,
        'fixed_questions': fixed_questions,
        'state': state,
        'random_sets': random_sets
    }
    return my_render_to_response(
        'yaksh/design_questionpaper.html',
        context,
        context_instance=RequestContext(request)
    )


@login_required
@email_verified
def show_all_questions(request):
    """Show a list of all the questions currently in the database."""

    user = request.user
    ci = RequestContext(request)
    context = {}
    if not is_moderator(user):
        raise Http404("You are not allowed to view this page !")

    questions = Question.objects.filter(user_id=user.id, active=True)
    form = QuestionFilterForm(user=user)
    user_tags = questions.values_list('tags', flat=True).distinct()
    all_tags = Tag.objects.filter(id__in = user_tags)
    upload_form = UploadFileForm()
    context['questions'] = questions
    context['all_tags'] = all_tags
    context['papers'] = []
    context['question'] = None
    context['form'] = form
    context['upload_form'] = upload_form

    if request.method == 'POST':
        if request.POST.get('delete') == 'delete':
            data = request.POST.getlist('question')
            if data is not None:
                questions = Question.objects.filter(id__in=data, user_id=user.id,
                                                    active=True)
                for question in questions:
                    question.active = False
                    question.save()

        if request.POST.get('upload') == 'upload':
            form = UploadFileForm(request.POST, request.FILES)
            if form.is_valid():
                questions_file = request.FILES['file']
                file_name = questions_file.name.split('.')
                if file_name[-1] == "zip":
                    ques = Question()
                    files, extract_path = extract_files(questions_file)
                    context['message'] = ques.read_yaml(extract_path, user,
                                                        files)
                else:
                    message = "Please Upload a ZIP file"
                    context['message'] = message

        if request.POST.get('download') == 'download':
            question_ids = request.POST.getlist('question')
            if question_ids:
                question = Question()
                zip_file = question.dump_questions(question_ids, user)
                response = HttpResponse(content_type='application/zip')
                response['Content-Disposition'] = dedent(
                    '''attachment; filename={0}_questions.zip'''.format(user)
                )
                zip_file.seek(0)
                response.write(zip_file.read())
                return response
            else:
                context['msg'] = "Please select atleast one question to download"

        if request.POST.get('test') == 'test':
            question_ids = request.POST.getlist("question")
            if question_ids:
                trial_paper, trial_course, trial_module = test_mode(
                    user, False, question_ids, None)
                trial_paper.update_total_marks()
                trial_paper.save()
                return my_redirect("/exam/start/1/{0}/{1}/{2}".format(
                    trial_module.id, trial_paper.id, trial_course.id))
            else:
                context["msg"] = "Please select atleast one question to test"

        if request.POST.get('question_tags'):
            question_tags = request.POST.getlist("question_tags")
            search_tags = []
            for tags in question_tags:
                search_tags.extend(re.split('[; |, |\*|\n]',tags))
            search_result = Question.objects.filter(tags__name__in=search_tags,
                                                    user=user).distinct()
            context['questions'] = search_result

    return my_render_to_response('yaksh/showquestions.html', context,
                                 context_instance=ci)


@login_required
@email_verified
def user_data(request, user_id, questionpaper_id=None, course_id=None):
    """Render user data."""
    current_user = request.user
    if not current_user.is_authenticated() or not is_moderator(current_user):
        raise Http404('You are not allowed to view this page!')
    user = User.objects.get(id=user_id)
    data = AnswerPaper.objects.get_user_data(user, questionpaper_id, course_id)

    context = {'data': data, 'course_id': course_id}
    return my_render_to_response('yaksh/user_data.html', context,
                                 context_instance=RequestContext(request))


def _expand_questions(questions, field_list):
    i = field_list.index('questions')
    field_list.remove('questions')
    for question in questions:
        field_list.insert(i, '{0}-{1}'.format(question.summary, question.points))
    return field_list 


@login_required
@email_verified
def download_quiz_csv(request, course_id, quiz_id):
    current_user = request.user
    if not is_moderator(current_user):
        raise Http404('You are not allowed to view this page!')
    course = get_object_or_404(Course, id=course_id)
    quiz = get_object_or_404(Quiz, id=quiz_id)
    if not course.is_creator(current_user) and not course.is_teacher(current_user):
        raise Http404('The quiz does not belong to your course')
    users = course.get_enrolled().order_by('first_name')
    if not users:
        return monitor(request, quiz_id)
    csv_fields = []
    attempt_number = None
    question_paper = quiz.questionpaper_set.last()
    last_attempt_number = AnswerPaper.objects.get_attempt_numbers(
        question_paper.id, course.id).last()
    if request.method == 'POST':
        csv_fields = request.POST.getlist('csv_fields')
        attempt_number = request.POST.get('attempt_number', last_attempt_number)
    if not csv_fields:
        csv_fields = CSV_FIELDS
    if not attempt_number:
        attempt_number = last_attempt_number

    questions = question_paper.get_question_bank()
    answerpapers = AnswerPaper.objects.filter(question_paper=question_paper,
            attempt_number=attempt_number, course_id=course_id)
    if not answerpapers:
        return monitor(request, quiz_id, course_id)
    response = HttpResponse(content_type='text/csv')
    response['Content-Disposition'] = 'attachment; filename="{0}-{1}-attempt{2}.csv"'.format(
            course.name.replace('.', ''),  quiz.description.replace('.', ''),
            attempt_number)
    writer = csv.writer(response)
    if 'questions' in csv_fields:
        csv_fields = _expand_questions(questions, csv_fields)
    writer.writerow(csv_fields)

    csv_fields_values = {'name': 'user.get_full_name().title()',
            'roll_number': 'user.profile.roll_number',
            'institute': 'user.profile.institute',
            'department': 'user.profile.department',
            'username': 'user.username',
            'marks_obtained': 'answerpaper.marks_obtained',
            'out_of': 'question_paper.total_marks',
            'percentage': 'answerpaper.percent', 'status': 'answerpaper.status'}
    questions_scores = {}
    for question in questions:
        questions_scores['{0}-{1}'.format(question.summary, question.points)] \
                = 'answerpaper.get_per_question_score({0})'.format(question.id) 
    csv_fields_values.update(questions_scores)

    users = users.exclude(id=course.creator.id).exclude(id__in=course.teachers.all())
    for user in users:
        row = []
        answerpaper = None
        papers = answerpapers.filter(user=user)
        if papers:
            answerpaper = papers.first()
        for field in csv_fields:
            try:
                row.append(eval(csv_fields_values[field]))
            except AttributeError:
                row.append('-')
        writer.writerow(row)
    return response


@login_required
@email_verified
def grade_user(request, quiz_id=None, user_id=None, attempt_number=None,
               course_id=None):
    """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.
    """
    current_user = request.user
    ci = RequestContext(request)
    if not current_user.is_authenticated() or not is_moderator(current_user):
        raise Http404('You are not allowed to view this page!')
    course_details = Course.objects.filter(Q(creator=current_user) |
                                           Q(teachers=current_user),
                                           is_trial=False).distinct()
    context = {"course_details": course_details}
    if quiz_id is not None:
        questionpaper_id = QuestionPaper.objects.filter(
            quiz_id=quiz_id
        ).values("id")
        user_details = AnswerPaper.objects.get_users_for_questionpaper(
            questionpaper_id, course_id
        )
        quiz = get_object_or_404(Quiz, id=quiz_id)
        course = get_object_or_404(Course, id=course_id)
        if not course.is_creator(current_user) and not \
                course.is_teacher(current_user):
            raise Http404('This course does not belong to you')

        has_quiz_assignments = AssignmentUpload.objects.filter(
                                question_paper_id=questionpaper_id
                                ).exists()
        context = {
            "users": user_details,
            "quiz_id": quiz_id,
            "quiz": quiz,
            "has_quiz_assignments": has_quiz_assignments,
            "course_id": course_id
        }
        if user_id is not None:
            attempts = AnswerPaper.objects.get_user_all_attempts(
                questionpaper_id, user_id, course_id
            )
            try:
                if attempt_number is None:
                    attempt_number = attempts[0].attempt_number
            except IndexError:
                raise Http404('No attempts for paper')
            has_user_assignments = AssignmentUpload.objects.filter(
                                question_paper_id=questionpaper_id,
                                user_id=user_id
                                ).exists()
            user = User.objects.get(id=user_id)
            data = AnswerPaper.objects.get_user_data(
                user, questionpaper_id, course_id, attempt_number
            )
            context = {
                "data": data,
                "quiz_id": quiz_id,
                "users": user_details,
                "attempts": attempts,
                "user_id": user_id,
                "has_user_assignments": has_user_assignments,
                "has_quiz_assignments": has_quiz_assignments,
                "course_id": course_id
            }
    if request.method == "POST":
        papers = data['papers']
        for paper in papers:
            for question, answers in six.iteritems(paper.get_question_answers()):
                marks = float(request.POST.get('q%d_marks' % question.id, 0))
                answer = answers[-1]['answer']
                answer.set_marks(marks)
                answer.save()
            paper.update_marks()
            paper.comments = request.POST.get(
                'comments_%d' % paper.question_paper.id, 'No comments')
            paper.save()

    return my_render_to_response(
        'yaksh/grade_user.html', context, context_instance=ci
    )


@login_required
@has_profile
@email_verified
def view_profile(request):
    """ view moderators and users profile """
    user = request.user
    ci = RequestContext(request)
    if is_moderator(user):
        template = 'manage.html'
    else:
        template = 'user.html'
    context = {'template': template, 'user': user}
    return my_render_to_response('yaksh/view_profile.html', context)


@login_required
@email_verified
def edit_profile(request):
    """ edit profile details facility for moderator and students """

    user = request.user
    ci = RequestContext(request)
    if is_moderator(user):
        template = 'manage.html'
    else:
        template = 'user.html'
    context = {'template': template}
    try:
        profile = Profile.objects.get(user_id=user.id)
    except Profile.DoesNotExist:
        profile = None

    if request.method == 'POST':
        form = ProfileForm(request.POST, user=user, instance=profile)
        if form.is_valid():
            form_data = form.save(commit=False)
            form_data.user = user
            form_data.user.first_name = request.POST['first_name']
            form_data.user.last_name = request.POST['last_name']
            form_data.user.save()
            form_data.save()
            return my_render_to_response(
                'yaksh/profile_updated.html', context_instance=ci
            )
        else:
            context['form'] = form
            return my_render_to_response(
                'yaksh/editprofile.html', context, context_instance=ci
            )
    else:
        form = ProfileForm(user=user, instance=profile)
        context['form'] = form
        return my_render_to_response(
            'yaksh/editprofile.html', context, context_instance=ci
        )


@login_required
@email_verified
def search_teacher(request, course_id):
    """ search teachers for the course """
    user = request.user
    ci = RequestContext(request)

    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')

    context = {'success': False}
    course = get_object_or_404(Course, pk=course_id)
    context['course'] = course

    if user != course.creator and user not in course.teachers.all():
        raise Http404('You are not allowed to view this page!')

    if request.method == 'POST':
        u_name = request.POST.get('uname')
        if not len(u_name) == 0:
            teachers = User.objects.filter(
                Q(username__icontains=u_name) |
                Q(first_name__icontains=u_name) |
                Q(last_name__icontains=u_name) |
                Q(email__icontains=u_name)
            ).exclude(
                Q(id=user.id) |
                Q(is_superuser=1) |
                Q(id=course.creator.id)
            )
            context['success'] = True
            context['teachers'] = teachers
    return my_render_to_response(
        'yaksh/addteacher.html', context, context_instance=ci
    )


@login_required
@email_verified
def add_teacher(request, course_id):
    """ add teachers to the course """

    user = request.user
    ci = RequestContext(request)

    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')

    context = {}
    course = get_object_or_404(Course, pk=course_id)
    if user == course.creator or user in course.teachers.all():
        context['course'] = course
    else:
        raise Http404('You are not allowed to view this page!')

    if request.method == 'POST':
        teacher_ids = request.POST.getlist('check')
        teachers = User.objects.filter(id__in=teacher_ids)
        add_to_group(teachers)
        course.add_teachers(*teachers)
        context['status'] = True
        context['teachers_added'] = teachers
    return my_render_to_response(
        'yaksh/addteacher.html', context, context_instance=ci
    )


@login_required
@email_verified
def remove_teachers(request, course_id):
    """ remove user from a course """

    user = request.user
    course = get_object_or_404(Course, pk=course_id)
    if not is_moderator(user) and (user != course.creator and user
        not in course.teachers.all()):
        raise Http404('You are not allowed to view this page!')

    if request.method == "POST":
        teacher_ids = request.POST.getlist('remove')
        teachers = User.objects.filter(id__in=teacher_ids)
        course.remove_teachers(*teachers)
    return my_redirect('/exam/manage/courses')


def test_mode(user, godmode=False, questions_list=None, quiz_id=None,
              course_id=None):
    """creates a trial question paper for the moderators"""

    if questions_list is not None:
        trial_course = Course.objects.create_trial_course(user)
        trial_quiz = Quiz.objects.create_trial_quiz(user)
        trial_questionpaper = QuestionPaper.objects.create_trial_paper_to_test_questions(
            trial_quiz, questions_list
        )
        trial_unit, created = LearningUnit.objects.get_or_create(
            order=1, type="quiz", quiz=trial_quiz,
            check_prerequisite=False)
        module, created = LearningModule.objects.get_or_create(
            order=1, creator=user, check_prerequisite=False,
            name="Trial for {0}".format(trial_course.name))
        module.learning_unit.add(trial_unit)
        trial_course.learning_module.add(module.id)
    else:
        trial_quiz, trial_course, module = Quiz.objects.create_trial_from_quiz(
            quiz_id, user, godmode, course_id
        )
        trial_questionpaper = QuestionPaper.objects.create_trial_paper_to_test_quiz(
            trial_quiz, quiz_id
        )
    return trial_questionpaper, trial_course, module


@login_required
@email_verified
def test_quiz(request, mode, quiz_id, course_id=None):
    """creates a trial quiz for the moderators"""
    godmode = True if mode == "godmode" else False
    current_user = request.user
    quiz = Quiz.objects.get(id=quiz_id)
    if (quiz.is_expired() or not quiz.active) and not godmode:
        return my_redirect('/exam/manage')

    trial_questionpaper, trial_course, trial_module = test_mode(
        current_user, godmode, None, quiz_id, course_id)
    return my_redirect("/exam/start/{0}/{1}/{2}".format(
        trial_questionpaper.id, trial_module.id, trial_course.id))


@login_required
@email_verified
def view_answerpaper(request, questionpaper_id, course_id):
    user = request.user
    quiz = get_object_or_404(QuestionPaper, pk=questionpaper_id).quiz
    course = get_object_or_404(Course, pk=course_id)
    if quiz.view_answerpaper and user in course.students.all():
        data = AnswerPaper.objects.get_user_data(user, questionpaper_id,
                                                 course_id)
        has_user_assignment = AssignmentUpload.objects.filter(
            user=user,
            question_paper_id=questionpaper_id
        ).exists()
        context = {'data': data, 'quiz': quiz,
                   "has_user_assignment": has_user_assignment}
        return my_render_to_response('yaksh/view_answerpaper.html', context)
    else:
        return my_redirect('/exam/quizzes/')


@login_required
@email_verified
def create_demo_course(request):
    """ creates a demo course for user """
    user = request.user
    ci = RequestContext(request)
    if not is_moderator(user):
        raise("You are not allowed to view this page")
    demo_course = Course()
    success = demo_course.create_demo(user)
    if success:
        msg = "Created Demo course successfully"
    else:
        msg = "Demo course already created"
    return prof_manage(request, msg)


@login_required
@email_verified
def grader(request, extra_context=None):
    user = request.user
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')
    courses = Course.objects.filter(is_trial=False)
    user_courses = list(courses.filter(creator=user)) + list(courses.filter(teachers=user))
    context = {'courses': user_courses}
    if extra_context:
        context.update(extra_context)
    return my_render_to_response('yaksh/regrade.html', context)


@login_required
@email_verified
def regrade(request, course_id, question_id=None, answerpaper_id=None,
            questionpaper_id=None):
    user = request.user
    course = get_object_or_404(Course, pk=course_id)
    if not is_moderator(user) or (user != course.creator and user not in course.teachers.all()):
        raise Http404('You are not allowed to view this page!')
    details = []
    if answerpaper_id is not None and question_id is None:
        answerpaper = get_object_or_404(AnswerPaper, pk=answerpaper_id)
        for question in answerpaper.questions.all():
            details.append(answerpaper.regrade(question.id))
    if questionpaper_id is not None and question_id is not None:
        answerpapers = AnswerPaper.objects.filter(questions=question_id,
                question_paper_id=questionpaper_id, course_id=course_id)
        for answerpaper in answerpapers:
            details.append(answerpaper.regrade(question_id))
    if answerpaper_id is not None and question_id is not None:
        answerpaper = get_object_or_404(AnswerPaper, pk=answerpaper_id)
        details.append(answerpaper.regrade(question_id))
    return grader(request, extra_context={'details': details})


@login_required
@email_verified
def download_course_csv(request, course_id):
    user = request.user
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')
    course = Course.objects.prefetch_related("learning_module").get(
        id=course_id)
    if not course.is_creator(user) and not course.is_teacher(user):
        raise Http404('The question paper does not belong to your course')
    students = course.get_only_students().annotate(
        roll_number=F('profile__roll_number'),
        institute=F('profile__institute')
    ).values(
        "id", "first_name", "last_name",
        "email", "institute", "roll_number"
    )
    quizzes = course.get_quizzes()

    for student in students:
        total_course_marks = 0.0
        user_course_marks = 0.0
        for quiz in quizzes:
            quiz_best_marks = AnswerPaper.objects.get_user_best_of_attempts_marks\
                               (quiz, student["id"], course_id)
            user_course_marks += quiz_best_marks
            total_course_marks += quiz.questionpaper_set.values_list(
                "total_marks", flat=True)[0]
            student["{}".format(quiz.description)] = quiz_best_marks
        student["total_scored"] = user_course_marks
        student["out_of"] = total_course_marks
    response = HttpResponse(content_type='text/csv')
    response['Content-Disposition'] = 'attachment; filename="{0}.csv"'.format(
                                      (course.name).lower().replace('.', ''))
    header = ['first_name', 'last_name', "roll_number", "email", "institute"]\
            + [quiz.description for quiz in quizzes] + ['total_scored', 'out_of']
    writer = csv.DictWriter(response, fieldnames=header, extrasaction='ignore')
    writer.writeheader()
    for student in students:
        writer.writerow(student)
    return response


def activate_user(request, key):
    ci = RequestContext(request)
    profile = get_object_or_404(Profile, activation_key=key)
    context = {}
    context['success'] = False
    if profile.is_email_verified:
        context['activation_msg'] = "Your account is already verified"
        return my_render_to_response(
            'yaksh/activation_status.html', context, context_instance=ci
        )

    if timezone.now() > profile.key_expiry_time:
        context['msg'] = dedent("""
                    Your activation time expired.
                    Please try again.
                    """)
    else:
        context['success'] = True
        profile.is_email_verified = True
        profile.save()
        context['msg'] = "Your account is activated"
    return my_render_to_response(
        'yaksh/activation_status.html', context, context_instance=ci
    )


def new_activation(request, email=None):
    ci = RequestContext(request)
    context = {}
    if request.method == "POST":
        email = request.POST.get('email')

    try:
        user = User.objects.get(email=email)
    except MultipleObjectsReturned:
        context['email_err_msg'] = "Multiple entries found for this email"\
                                    "Please change your email"
        return my_render_to_response(
            'yaksh/activation_status.html', context, context_instance=ci
        )
    except ObjectDoesNotExist:
        context['success'] = False
        context['msg'] = "Your account is not verified. \
                            Please verify your account"
        return render_to_response(
            'yaksh/activation_status.html', context, context_instance=ci
        )

    if not user.profile.is_email_verified:
        user.profile.activation_key = generate_activation_key(user.username)
        user.profile.key_expiry_time = timezone.now() + \
            timezone.timedelta(minutes=20)
        user.profile.save()
        new_user_data = User.objects.get(email=email)
        success, msg = send_user_mail(new_user_data.email,
                                      new_user_data.profile.activation_key
                                      )
        if success:
            context['activation_msg'] = msg
        else:
            context['msg'] = msg
    else:
        context['activation_msg'] = "Your account is already verified"

    return my_render_to_response(
        'yaksh/activation_status.html', context, context_instance=ci
    )


def update_email(request):
    context = {}
    ci = RequestContext(request)
    if request.method == "POST":
        email = request.POST.get('email')
        username = request.POST.get('username')
        user = get_object_or_404(User, username=username)
        user.email = email
        user.save()
        return new_activation(request, email)
    else:
        context['email_err_msg'] = "Please Update your email"
        return my_render_to_response(
            'yaksh/activation_status.html', context, context_instance=ci
        )


@login_required
@email_verified
def download_assignment_file(request, quiz_id, question_id=None, user_id=None):
    user = request.user
    if not is_moderator(user):
        raise Http404("You are not allowed to view this page")
    qp = QuestionPaper.objects.get(quiz_id=quiz_id)
    assignment_files, file_name = AssignmentUpload.objects.get_assignments(
        qp, question_id, user_id
    )
    zipfile_name = string_io()
    zip_file = zipfile.ZipFile(zipfile_name, "w")
    for f_name in assignment_files:
        folder = f_name.user.get_full_name().replace(" ", "_")
        sub_folder = f_name.assignmentQuestion.summary.replace(" ", "_")
        folder_name = os.sep.join((folder, sub_folder, os.path.basename(
                        f_name.assignmentFile.name))
                        )
        zip_file.write(
            f_name.assignmentFile.path, folder_name
        )
    zip_file.close()
    zipfile_name.seek(0)
    response = HttpResponse(content_type='application/zip')
    response['Content-Disposition'] = 'attachment; filename={0}.zip'.format(
                                            file_name.replace(" ", "_")
                                            )
    response.write(zipfile_name.read())
    return response


@login_required
@email_verified
def upload_users(request, course_id):
    user = request.user
    ci = RequestContext(request)
    course = get_object_or_404(Course, pk=course_id)
    context = {'course': course}

    if not (course.is_teacher(user) or course.is_creator(user)):
        msg = 'You do not have permissions to this course.'
        return complete(request, reason=msg)
    if request.method == 'POST':
        if 'csv_file' not in request.FILES:
            context['message'] = "Please upload a CSV file."
            return my_render_to_response('yaksh/course_detail.html', context,
                                         context_instance=ci)
        csv_file = request.FILES['csv_file']
        is_csv_file, dialect = is_csv(csv_file)
        if not is_csv_file:
            context['message'] = "The file uploaded is not a CSV file."
            return my_render_to_response('yaksh/course_detail.html', context,
                                         context_instance=ci)
        required_fields = ['firstname', 'lastname', 'email']
        try:
            reader = csv.DictReader(csv_file.read().decode('utf-8').splitlines(),
                                    dialect=dialect)
        except TypeError:
            context['message'] = "Bad CSV file"
            return my_render_to_response('yaksh/course_detail.html', context,
                                         context_instance=ci)
        stripped_fieldnames = [field.strip().lower() for field in reader.fieldnames]
        for field in required_fields:
            if field not in stripped_fieldnames:
                context['message'] = "The CSV file does not contain the required headers"
                return my_render_to_response('yaksh/course_detail.html', context,
                                             context_instance=ci)
        reader.fieldnames = stripped_fieldnames
        context['upload_details'] = _read_user_csv(reader, course)
    return my_render_to_response('yaksh/course_detail.html', context,
                                 context_instance=ci)


def _read_user_csv(reader, course):
    fields = reader.fieldnames
    upload_details = ["Upload Summary:"]
    counter = 0
    for row in reader:
        counter += 1
        (username, email, first_name, last_name, password, roll_no, institute,
         department, remove) = _get_csv_values(row, fields)
        if not email or not first_name or not last_name:
            upload_details.append("{0} -- Missing Values".format(counter))
            continue
        users = User.objects.filter(username=username)
        if users.exists():
            user = users[0]
            if remove.strip().lower() == 'true':
                if _remove_from_course(user, course):
                    upload_details.append("{0} -- {1} -- User rejected".format(
                                          counter, user.username))
                    continue
            else:
                if _add_to_course(user, course):
                    upload_details.append("{0} -- {1} -- User rejected".format(
                                          counter, user.username))
            if user not in course.get_enrolled():
                upload_details.append("{0} -- {1} not added to course".format(
                    counter, user))
                continue
        user_defaults = {'email': email, 'first_name': first_name,
                         'last_name': last_name}
        user, created = _create_or_update_user(username, password, user_defaults)
        profile_defaults = {'institute': institute, 'roll_number': roll_no,
                            'department': department, 'is_email_verified': True}
        _create_or_update_profile(user, profile_defaults)
        if created:
            state = "Added"
            course.students.add(user)
        else:
            state = "Updated"
        upload_details.append("{0} -- {1} -- User {2} Successfully".format(
                              counter, user.username, state))
    if counter == 0:
        upload_details.append("No rows in the CSV file")
    return upload_details


def _get_csv_values(row, fields):
    roll_no, institute, department = "", "", ""
    remove = "false"
    email, first_name, last_name = map(str.strip, [row['email'],
                                       row['firstname'],
                                       row['lastname']])
    password = email
    username = email
    if 'password' in fields and row['password']:
        password = row['password'].strip()
    if 'roll_no' in fields:
        roll_no = row['roll_no'].strip()
    if 'institute' in fields:
        institute = row['institute'].strip()
    if 'department' in fields:
        department = row['department'].strip()
    if 'remove' in fields:
        remove = row['remove'].strip()
    if 'username' in fields and row['username']:
        username = row['username'].strip()
    if 'remove' in fields:
        remove = row['remove']
    return (username, email, first_name, last_name, password, roll_no, institute,
            department, remove)


def _remove_from_course(user, course):
    if user in course.get_enrolled():
        course.reject(True, user)
        return True


def _add_to_course(user, course):
    if user in course.get_rejected():
        course.enroll(True, user)
        return True


def _create_or_update_user(username, password, defaults):
    user, created = User.objects.update_or_create(username=username,
                                                  defaults=defaults)
    user.set_password(password)
    user.save()
    return user, created


def _create_or_update_profile(user, defaults):
    Profile.objects.update_or_create(user=user, defaults=defaults)


@login_required
@email_verified
def download_sample_csv(request):
    user = request.user
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')
    csv_file_path = os.path.join(FIXTURES_DIR_PATH,
                                 "sample_user_upload.csv")
    with open(csv_file_path, 'rb') as csv_file:
        response = HttpResponse(csv_file.read(), content_type='text/csv')
        response['Content-Disposition'] = (
            'attachment; filename="sample_user_upload"'
        )
        return response


@login_required
@email_verified
def duplicate_course(request, course_id):
    user = request.user
    course = Course.objects.get(id=course_id)
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')

    if course.is_teacher(user) or course.is_creator(user):
        course.create_duplicate_course(user)
    else:
        msg = 'You do not have permissions to clone this course, please contact your '\
            'instructor/administrator.'
        return complete(request, msg, attempt_num=None, questionpaper_id=None)
    return my_redirect('/exam/manage/courses/')


@login_required
@email_verified
def download_yaml_template(request):
    user = request.user
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')
    template_path = os.path.join(os.path.dirname(__file__), "fixtures",
                                 "demo_questions.zip"
                                 )
    yaml_file = zipfile.ZipFile(template_path, 'r')
    template_yaml = yaml_file.open('questions_dump.yaml', 'r')
    response = HttpResponse(template_yaml, content_type='text/yaml')
    response['Content-Disposition'] = (
        'attachment; filename="questions_dump.yaml"'
    )
    return response


@login_required
@email_verified
def edit_lesson(request, lesson_id=None, course_id=None):
    user = request.user
    ci = RequestContext(request)
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')
    if lesson_id:
        lesson = Lesson.objects.get(id=lesson_id)
        if not lesson.creator == user and not course_id:
            raise Http404('This Lesson does not belong to you')
    else:
        lesson = None
    if course_id:
        course = get_object_or_404(Course, id=course_id)
        if not course.is_creator(user) and not course.is_teacher(user):
            raise Http404('This Lesson does not belong to you')
        redirect_url = "/exam/manage/courses/"
    else:
        redirect_url = "/exam/manage/courses/all_lessons/"
    context = {}
    if request.method == "POST":
        if "Save" in request.POST:
            lesson_form = LessonForm(request.POST, instance=lesson)
            lesson_file_form = LessonFileForm(request.POST, request.FILES)
            lessonfiles = request.FILES.getlist('Lesson_files')
            if lesson_form.is_valid():
                if lesson is None:
                    lesson_form.instance.creator = user
                lesson = lesson_form.save()
                lesson.html_data = get_html_text(lesson.description)
                lesson.save()
                if lessonfiles:
                    for les_file in lessonfiles:
                        LessonFile.objects.get_or_create(
                            lesson=lesson, file=les_file
                        )
                return my_redirect(redirect_url)
            else:
                context['lesson_form'] = lesson_form
                context['lesson_file_form'] = lesson_file_form

        if 'Delete' in request.POST:
            remove_files_id = request.POST.getlist('delete_files')
            if remove_files_id:
                files = LessonFile.objects.filter(id__in=remove_files_id)
                for file in files:
                    file.remove()
            return my_redirect(redirect_url)

    lesson_files = LessonFile.objects.filter(lesson=lesson)
    lesson_files_form = LessonFileForm()
    lesson_form = LessonForm(instance=lesson)
    context['lesson_form'] = lesson_form
    context['lesson_file_form'] = lesson_files_form
    context['lesson_files'] = lesson_files
    context['course_id'] = course_id
    return my_render_to_response(
        'yaksh/add_lesson.html', context, context_instance=ci
    )


@login_required
@email_verified
def show_lesson(request, lesson_id, module_id, course_id):
    user = request.user
    course = Course.objects.get(id=course_id)
    if user not in course.students.all():
        raise Http404('This course does not belong to you')
    if not course.active or not course.is_active_enrollment():
        msg = "{0} is either expired or not active".format(course.name)
        return quizlist_user(request, msg=msg)
    learn_module = course.learning_module.get(id=module_id)
    learn_unit = learn_module.learning_unit.get(lesson_id=lesson_id)
    learning_units = learn_module.get_learning_units()
    if learn_module.has_prerequisite():
        if not learn_module.is_prerequisite_passed(user, course):
            msg = "You have not completed the module previous to {0}".format(
                learn_module.name)
            return view_module(request, module_id, course_id, msg)

    # update course status with current unit
    _update_unit_status(course_id, user, learn_unit)

    all_modules = course.get_learning_modules()
    if learn_unit.has_prerequisite():
        if not learn_unit.is_prerequisite_passed(user, learn_module, course):
            msg = "You have not completed previous Lesson/Quiz/Exercise"
            return view_module(request, learn_module.id, course_id, msg=msg)
    context = {'lesson': learn_unit.lesson, 'user': user,
               'course': course, 'state': "lesson", "all_modules": all_modules,
               'learning_units': learning_units, "current_unit": learn_unit,
               'learning_module': learn_module}
    return my_render_to_response('yaksh/show_video.html', context)


@login_required
@email_verified
def design_module(request, module_id, course_id=None):
    user = request.user
    ci = RequestContext(request)
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')
    context = {}
    if course_id:
        course = Course.objects.get(id=course_id)
        if not course.is_creator(user) and not course.is_teacher(user):
            raise Http404('This course does not belong to you')
    learning_module = LearningModule.objects.get(id=module_id)
    if request.method == "POST":
        if "Add" in request.POST:
            add_values = request.POST.get("choosen_list").split(',')
            to_add_list = []
            if add_values:
                ordered_units = learning_module.get_learning_units()
                if ordered_units.exists():
                    start_val = ordered_units.last().order + 1
                else:
                    start_val = 1
                for order, value in enumerate(add_values, start_val):
                    learning_id, type = value.split(":")
                    if type == "quiz":
                        learning_unit = LearningUnit.objects.create(
                            order=order, quiz_id=learning_id,
                            type=type)
                    else:
                        learning_unit = LearningUnit.objects.create(
                            order=order, lesson_id=learning_id,
                            type=type)
                    to_add_list.append(learning_unit)
                learning_module.learning_unit.add(*to_add_list)

        if "Change" in request.POST:
            order_list = request.POST.get("ordered_list").split(",")
            for order in order_list:
                learning_unit, learning_order = order.split(":")
                if learning_order:
                    learning_unit = learning_module.learning_unit.get(
                        id=learning_unit)
                    learning_unit.order = learning_order
                    learning_unit.save()

        if "Remove" in request.POST:
            remove_values = request.POST.getlist("delete_list")
            if remove_values:
                learning_module.learning_unit.remove(*remove_values)
                LearningUnit.objects.filter(id__in=remove_values).delete()

        if "Change_prerequisite" in request.POST:
            unit_list = request.POST.getlist("check_prereq")
            for unit in unit_list:
                learning_unit = learning_module.learning_unit.get(id=unit)
                learning_unit.toggle_check_prerequisite()
                learning_unit.save()

    added_quiz_lesson = learning_module.get_added_quiz_lesson()
    quizzes = [("quiz", quiz) for quiz in Quiz.objects.filter(
               creator=user, is_trial=False)]
    lessons = [("lesson", lesson)
               for lesson in Lesson.objects.filter(creator=user)]
    quiz_les_list = set(quizzes + lessons) - set(added_quiz_lesson)
    context['quiz_les_list'] = quiz_les_list
    context['learning_units'] = learning_module.get_learning_units()
    context['status'] = 'design'
    context['module_id'] = module_id
    context['course_id'] = course_id
    return my_render_to_response('yaksh/add_module.html', context,
                                 context_instance=ci)


@login_required
@email_verified
def add_module(request, module_id=None, course_id=None):
    user = request.user
    ci = RequestContext(request)
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')
    redirect_url = "/exam/manage/courses/all_learning_module/"
    if course_id:
        course = Course.objects.get(id=course_id)
        if not course.is_creator(user) and not course.is_teacher(user):
            raise Http404('This course does not belong to you')
        redirect_url = "/exam/manage/courses/"
    if module_id:
        module = LearningModule.objects.get(id=module_id)
        if not module.creator == user and not course_id:
            raise Http404('This Learning Module does not belong to you')
    else:
        module = None
    context = {}
    if request.method == "POST":
        if "Save" in request.POST:
            module_form = LearningModuleForm(request.POST, instance=module)
            if module_form.is_valid():
                if module is None:
                    module_form.instance.creator = user
                module = module_form.save()
                module.html_data = get_html_text(module.description)
                module.save()
                return my_redirect(redirect_url)
            else:
                context['module_form'] = module_form

    module_form = LearningModuleForm(instance=module)
    context['module_form'] = module_form
    context['course_id'] = course_id
    context['status'] = "add"
    return my_render_to_response("yaksh/add_module.html",
                                 context, context_instance=ci)


@login_required
@email_verified
def show_all_quizzes(request):
    user = request.user
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')
    quizzes = Quiz.objects.filter(creator=user, is_trial=False)
    context = {"quizzes": quizzes, "type": "quiz"}
    return my_render_to_response('yaksh/courses.html', context)


@login_required
@email_verified
def show_all_lessons(request):
    user = request.user
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')
    lessons = Lesson.objects.filter(creator=user)
    context = {"lessons": lessons, "type": "lesson"}
    return my_render_to_response('yaksh/courses.html', context)


@login_required
@email_verified
def show_all_modules(request):
    user = request.user
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')
    learning_modules = LearningModule.objects.filter(
        creator=user, is_trial=False)
    context = {"learning_modules": learning_modules, "type": "learning_module"}
    return my_render_to_response('yaksh/courses.html', context)


@login_required
@email_verified
def preview_html_text(request):
    user = request.user
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')
    response_kwargs = {}
    response_kwargs['content_type'] = 'application/json'
    request_data = json.loads(request.body.decode("utf-8"))
    html_text = get_html_text(request_data['description'])
    return HttpResponse(json.dumps({"data": html_text}), **response_kwargs)


@login_required
@email_verified
def get_next_unit(request, course_id, module_id, current_unit_id=None,
                  first_unit=None):
    user = request.user
    course = Course.objects.prefetch_related("learning_module").get(
        id=course_id)
    if user not in course.students.all():
        raise Http404('You are not enrolled for this course!')
    learning_module = course.learning_module.prefetch_related(
        "learning_unit").get(id=module_id)

    if current_unit_id:
        current_learning_unit = learning_module.learning_unit.get(
            id=current_unit_id)
    else:
        next_module = course.next_module(learning_module.id)
        return my_redirect("/exam/quizzes/view_module/{0}/{1}".format(
            next_module.id, course_id))

    if first_unit:
        next_unit = current_learning_unit
    else:
        next_unit = learning_module.get_next_unit(current_learning_unit.id)

    course_status = CourseStatus.objects.filter(
        user=user, course_id=course_id,
    )
    if not course_status.exists():
        course_status = CourseStatus.objects.create(
            user=user, course_id=course_id
        )
    else:
        course_status = course_status.first()

    # Add learning unit to completed units list
    if not first_unit:
        course_status.completed_units.add(current_learning_unit.id)

        # if last unit of current module go to next module
        is_last_unit = course.is_last_unit(learning_module,
                                           current_learning_unit.id)
        if is_last_unit:
            next_module = course.next_module(learning_module.id)
            return my_redirect("/exam/quizzes/view_module/{0}/{1}/".format(
                next_module.id, course.id))

    if next_unit.type == "quiz":
        return my_redirect("/exam/start/{0}/{1}/{2}".format(
            next_unit.quiz.questionpaper_set.get().id, module_id, course_id))
    else:
        return my_redirect("/exam/show_lesson/{0}/{1}/{2}".format(
            next_unit.lesson.id, module_id, course_id))


@login_required
@email_verified
def design_course(request, course_id):
    user = request.user
    ci = RequestContext(request)
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')
    course = Course.objects.get(id=course_id)
    if not course.is_creator(user) and not course.is_teacher(user):
        raise Http404('This course does not belong to you')
    context = {}
    if request.method == "POST":
        if "Add" in request.POST:
            add_values = request.POST.getlist("module_list")
            to_add_list = []
            if add_values:
                ordered_modules = course.get_learning_modules()
                if ordered_modules.exists():
                    start_val = ordered_modules.last().order + 1
                else:
                    start_val = 1
                for order, value in enumerate(add_values, start_val):
                    learning_module = LearningModule.objects.get(id=int(value))
                    learning_module.order = order
                    learning_module.save()
                    to_add_list.append(learning_module)
                course.learning_module.add(*to_add_list)

        if "Change" in request.POST:
            order_list = request.POST.get("ordered_list").split(",")
            for order in order_list:
                learning_unit, learning_order = order.split(":")
                if learning_order:
                    learning_module = course.learning_module.get(
                        id=learning_unit)
                    learning_module.order = learning_order
                    learning_module.save()

        if "Remove" in request.POST:
            remove_values = request.POST.getlist("delete_list")
            if remove_values:
                course.learning_module.remove(*remove_values)

        if "Change_prerequisite" in request.POST:
            unit_list = request.POST.getlist("check_prereq")
            for unit in unit_list:
                learning_module = course.learning_module.get(id=unit)
                learning_module.toggle_check_prerequisite()
                learning_module.save()

    added_learning_modules = course.get_learning_modules()
    all_learning_modules = LearningModule.objects.filter(
        creator=user, is_trial=False)

    learning_modules = set(all_learning_modules) - set(added_learning_modules)
    context['added_learning_modules'] = added_learning_modules
    context['learning_modules'] = learning_modules
    context['course_id'] = course_id
    return my_render_to_response('yaksh/design_course_session.html', context,
                                 context_instance=ci)


@login_required
@email_verified
def view_module(request, module_id, course_id, msg=None):
    user = request.user
    course = Course.objects.get(id=course_id)
    if user not in course.students.all():
        raise Http404('You are not enrolled for this course!')
    context = {}
    if not course.active or not course.is_active_enrollment():
        msg = "{0} is either expired or not active".format(course.name)
        return course_modules(request, course_id, msg)
    learning_module = course.learning_module.get(id=module_id)
    all_modules = course.get_learning_modules()
    if learning_module.has_prerequisite():
        if not learning_module.is_prerequisite_passed(user, course):
            msg = "You have not completed the module previous to {0}".format(
                learning_module.name)
            return course_modules(request, course_id, msg)

    learning_units = learning_module.get_learning_units()
    context['learning_units'] = learning_units
    context['learning_module'] = learning_module
    context['first_unit'] = learning_units.first()
    context['all_modules'] = all_modules
    context['user'] = user
    context['course'] = course
    context['state'] = "module"
    context['msg'] = msg
    return my_render_to_response('yaksh/show_video.html', context)


@login_required
@email_verified
def course_modules(request, course_id, msg=None):
    user = request.user
    course = Course.objects.get(id=course_id)
    if user not in course.students.all():
        msg = 'You are not enrolled for this course!'
        return quizlist_user(request, msg=msg)

    if not course.active or not course.is_active_enrollment():
        msg = "{0} is either expired or not active".format(course.name)
        return quizlist_user(request, msg=msg)
    learning_modules = course.get_learning_modules()
    context = {"course": course, "learning_modules": learning_modules,
               "user": user, "msg": msg}
    return my_render_to_response('yaksh/course_modules.html', context)


@login_required
@email_verified
def course_status(request, course_id):
    user = request.user
    if not is_moderator(user):
        raise Http404('You are not allowed to view this page!')
    course = get_object_or_404(Course, pk=course_id)
    if not course.is_creator(user) and not course.is_teacher(user):
        raise Http404('This course does not belong to you')
    students = course.get_only_students()
    context = {
        'course': course, 'students': students,
        'state': 'course_status', 'modules': course.get_learning_modules()
    }
    return my_render_to_response('yaksh/course_detail.html', context)


def _update_unit_status(course_id, user, unit):
    """ Update course status with current unit """
    course_status = CourseStatus.objects.filter(
        user=user, course_id=course_id,
    )
    if not course_status.exists():
        course_status = CourseStatus.objects.create(
            user=user, course_id=course_id
        )
    else:
        course_status = course_status.first()
    # make next available unit as current unit
    course_status.current_unit = unit
    course_status.save()