import random
import string
import os
import stat
from os.path import dirname, pardir, abspath, join, exists
import datetime

from django.http import HttpResponse
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
from django.http import Http404
from django.db.models import Sum

# Local imports.
from exam.models import Quiz, Question, QuestionPaper, Profile, Answer, User
from exam.forms import UserRegisterForm, UserLoginForm
from exam.xmlrpc_clients import code_server
from settings import URL_ROOT

# The directory where user data can be saved.
OUTPUT_DIR = abspath(join(dirname(__file__), pardir, 'output'))


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 gen_key(no_of_chars):
    """Generate a random key of the number of characters."""
    allowed_chars = string.digits+string.uppercase
    return ''.join([random.choice(allowed_chars) for i in range(no_of_chars)])
    
def get_user_dir(user):
    """Return the output directory for the user."""
    user_dir = join(OUTPUT_DIR, str(user.username))
    if not exists(user_dir):
        os.mkdir(user_dir)
        # Make it rwx by others.
        os.chmod(user_dir, stat.S_IROTH | stat.S_IWOTH | stat.S_IXOTH \
                | stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR \
                | stat.S_IRGRP | stat.S_IWGRP | stat.S_IXGRP)
    return user_dir
    
def index(request):
    """The start page.
    """
    user = request.user
    if user.is_authenticated():
        return my_redirect("/exam/start/")

    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
    if user.is_authenticated():
        return my_redirect("/exam/start/")

    if request.method == "POST":
        form = UserRegisterForm(request.POST)
        if form.is_valid():
            data = form.cleaned_data
            u_name, pwd = form.save()

            new_user = authenticate(username = u_name, password = pwd)
            login(request, new_user)
            return my_redirect("/exam/start/")
                
        else:
            return my_render_to_response('exam/register.html',
                {'form':form},
                context_instance=RequestContext(request))
    else:
        form = UserRegisterForm()
        return my_render_to_response('exam/register.html',
                {'form':form},
                context_instance=RequestContext(request))

def add_question(request):
    return render_to_response('exam/add_question.html',{})

def add_quiz(request):
    return render_to_response('exam/add_quiz.html',{})

def prof_manage(request):
    return render_to_response('manage.html',{})

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

    user = request.user
    if user.is_authenticated():
        return my_redirect("/exam/start/")

    if request.method == "POST":
        form = UserLoginForm(request.POST)
        if form.is_valid():
            user = form.cleaned_data
            login(request, user)
            return my_redirect("/exam/start/")
        else:
            context = {"form": form}
            return my_render_to_response('exam/login.html', context,
                        context_instance=RequestContext(request))
    else:
        form = UserLoginForm()
        context = {"form": form}
        return my_render_to_response('exam/login.html', context,
                                     context_instance=RequestContext(request))

def start(request):
    user = request.user
    try:
        # Right now the app is designed so there is only one active quiz 
        # at a particular time.
        quiz = Quiz.objects.get(active=True)
    except Quiz.DoesNotExist:
        msg = 'No active quiz found, please contact your '\
              'instructor/administrator. Please login again thereafter.'
        return complete(request, reason=msg)
    try:
        old_paper = QuestionPaper.objects.get(user=user, quiz=quiz)
        q = old_paper.current_question()
        return show_question(request, q)
    except QuestionPaper.DoesNotExist:
        ip = request.META['REMOTE_ADDR']
        key = gen_key(10)
        try:
            profile = user.get_profile()
        except Profile.DoesNotExist:
            msg = 'You do not have a profile and cannot take the quiz!'
            raise Http404(msg)

        new_paper = QuestionPaper(user=user, user_ip=ip, key=key, 
                                  quiz=quiz, profile=profile)
        new_paper.start_time = datetime.datetime.now()
        
        # Make user directory.
        user_dir = get_user_dir(user)

        questions = [ str(_.id) for _ in Question.objects.filter(active=True) ]
        random.shuffle(questions)
        
        new_paper.questions = "|".join(questions)
        new_paper.save()
    
        # Show the user the intro page.    
        context = {'user': user}
        ci = RequestContext(request)
        return my_render_to_response('exam/intro.html', context, 
                                     context_instance=ci)

def question(request, q_id):
    user = request.user
    if not user.is_authenticated():
        return my_redirect('/exam/login/')
    q = get_object_or_404(Question, pk=q_id)
    try:
        paper = QuestionPaper.objects.get(user=request.user, quiz__active=True)
    except QuestionPaper.DoesNotExist:
        return my_redirect('/exam/start')
    if not paper.quiz.active:
        return complete(request, reason='The quiz has been deactivated!')

    time_left = paper.time_left()
    if time_left == 0:
        return complete(request, reason='Your time is up!')
    quiz_name = paper.quiz.description
    context = {'question': q, 'paper': paper, 'user': user, 
               'quiz_name': quiz_name, 
               'time_left': time_left}
    ci = RequestContext(request)
    return my_render_to_response('exam/question.html', context, 
                                 context_instance=ci)

def show_question(request, q_id):
    """Show a question if possible."""
    if len(q_id) == 0:
        msg = 'Congratulations!  You have successfully completed the quiz.'
        return complete(request, msg)
    else:
        return question(request, q_id)

def check(request, q_id):
    user = request.user
    if not user.is_authenticated():
        return my_redirect('/exam/login/')
    question = get_object_or_404(Question, pk=q_id)
    paper = QuestionPaper.objects.get(user=user, quiz__active=True)
    answer = request.POST.get('answer')
    skip = request.POST.get('skip', None)
    
    if skip is not None:
        next_q = paper.skip()
        return show_question(request, next_q)

    # Add the answer submitted, regardless of it being correct or not.
    new_answer = Answer(question=question, answer=answer, correct=False)
    new_answer.save()
    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.
    if question.type == 'mcq':
        success = True # Only one attempt allowed for MCQ's.
        if answer.strip() == question.test.strip():
            new_answer.correct = True
            new_answer.marks = question.points
            new_answer.error = 'Correct answer'
        else:
            new_answer.error = 'Incorrect answer'
    else:
        user_dir = get_user_dir(user)
        success, err_msg = code_server.run_code(answer, question.test, 
                                                user_dir, question.type)
        new_answer.error = err_msg
        if success:
            # Note the success and save it along with the marks.
            new_answer.correct = success
            new_answer.marks = question.points

    new_answer.save()

    if not success: # Should only happen for non-mcq questions.
        time_left = paper.time_left()
        if time_left == 0:
            return complete(request, reason='Your time is up!')
        if not paper.quiz.active:
            return complete(request, reason='The quiz has been deactivated!')
            
        context = {'question': question, 'error_message': err_msg,
                   'paper': paper, 'last_attempt': answer,
                   'quiz_name': paper.quiz.description,
                   'time_left': time_left}
        ci = RequestContext(request)

        return my_render_to_response('exam/question.html', context, 
                                     context_instance=ci)
    else:
        next_q = paper.completed_question(question.id)
        return show_question(request, next_q)
        
def quit(request):
   
    return my_render_to_response('exam/quit.html',context_instance=RequestContext(request)) 

def complete(request,reason = None):
    user = request.user
    no = False
    message = reason or 'The quiz has been completed. Thank you.'
    if request.method == 'POST' and 'no' in request.POST:
        no = True
    if not no:
        # Logout the user and quit with the message given.
        logout(request)
        context = {'message': message}
        return my_render_to_response('exam/complete.html', context)
    else:
        return my_redirect('/exam/')

def monitor(request, quiz_id=None):
    """Monitor the progress of the papers taken so far."""
    user = request.user
    if not user.is_authenticated() and not user.is_staff:
        raise Http404('You are not allowed to view this page!')

    if quiz_id is None:
        quizzes = Quiz.objects.all()
        context = {'papers': [], 
                   'quiz': None, 
                   'quizzes':quizzes}
        return my_render_to_response('exam/monitor.html', context,
                                    context_instance=RequestContext(request)) 
    # quiz_id is not None.
    try:
        quiz = Quiz.objects.get(id=quiz_id)
    except Quiz.DoesNotExist:
        papers = []
        quiz = None
    else:
        papers = QuestionPaper.objects.all().annotate(
                    total=Sum('answers__marks')).order_by('-total')

    context = {'papers': papers, 'quiz': quiz, 'quizzes': None}
    return my_render_to_response('exam/monitor.html', context,
                                 context_instance=RequestContext(request)) 

def get_user_data(username):
    """For a given username, this returns a dictionary of important data
    related to the user including all the user's answers submitted.
    """
    user = User.objects.get(username=username)
    papers = QuestionPaper.objects.filter(user=user)

    data = {}
    try:
        profile = user.get_profile()
    except Profile.DoesNotExist:
        # Admin user may have a paper by accident but no profile.
        profile = None
    data['user'] = user
    data['profile'] = profile
    data['papers'] = papers 
    return data

def show_all_users(request):
    user = User.objects.filter(username__contains="")
    context = { 'user':user }
    print context
    return my_render_to_response('exam/showusers.html',context,context_instance=RequestContext(request))

def user_data(request, username):
    """Render user data."""
    current_user = request.user
    if not current_user.is_authenticated() and not current_user.is_staff:
        raise Http404('You are not allowed to view this page!')

    data = get_user_data(username)

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

def grade_user(request, username):
    """Present an interface with which we can easily grade a user's papers
    and update all their marks and also give comments for each paper.
    """
    current_user = request.user
    if not current_user.is_authenticated() and not current_user.is_staff:
        raise Http404('You are not allowed to view this page!')

    data = get_user_data(username)
    if request.method == 'POST':
        papers = data['papers']
        for paper in papers:
            for question, answers in paper.get_question_answers().iteritems():
                marks = float(request.POST.get('q%d_marks'%question.id))
                last_ans = answers[-1]
                last_ans.marks = marks
                last_ans.save()
            paper.comments = request.POST.get('comments_%d'%paper.quiz.id)
            paper.save()

        context = {'data': data}
	print context
        return my_render_to_response('exam/user_data.html', context,
                                 context_instance=RequestContext(request))
    else:
        context = {'data': data}
	print context
        return my_render_to_response('exam/grade_user.html', context,
                                 context_instance=RequestContext(request))