from random import sample

  import django

  from django.contrib import auth

  from django.shortcuts import get_object_or_404

  from flashcards.api import StandardResultsSetPagination, IsEnrolledInAssociatedSection, IsFlashcardReviewer

  from flashcards.models import Section, User, Flashcard, FlashcardHide, UserFlashcard, UserFlashcardQuiz

  from flashcards.notifications import notify_new_card

  from flashcards.serializers import SectionSerializer, UserUpdateSerializer, RegistrationSerializer, UserSerializer, \

      PasswordResetSerializer, PasswordResetRequestSerializer, EmailPasswordSerializer, FlashcardSerializer, \

      FlashcardUpdateSerializer, QuizRequestSerializer, QuizResponseSerializer, \
      QuizAnswerRequestSerializer, DeepSectionSerializer

  from rest_framework.decorators import detail_route, permission_classes, api_view, list_route

  from rest_framework.generics import ListAPIView, GenericAPIView

  from rest_framework.mixins import CreateModelMixin, RetrieveModelMixin, UpdateModelMixin

  from rest_framework.permissions import IsAuthenticated

  from rest_framework.viewsets import ReadOnlyModelViewSet, GenericViewSet

  from django.core.mail import send_mail

  from django.contrib.auth import authenticate

  from django.contrib.auth.tokens import default_token_generator

  from rest_framework.status import HTTP_204_NO_CONTENT, HTTP_201_CREATED, HTTP_200_OK

  from rest_framework.response import Response

  from rest_framework.exceptions import AuthenticationFailed, NotAuthenticated, ValidationError, PermissionDenied

  from simple_email_confirmation import EmailAddress

  class SectionViewSet(ReadOnlyModelViewSet):

      queryset = Section.objects.all()

      serializer_class = DeepSectionSerializer

      pagination_class = StandardResultsSetPagination

      permission_classes = [IsAuthenticated]

      @detail_route(methods=['GET'])

      def flashcards(self, request, pk):
          """
          Gets flashcards for a section, excluding hidden cards.
          Returned in strictly chronological order (material date).
          """

          flashcards = Flashcard.cards_visible_to(request.user).filter(section=self.get_object()).all()

          return Response(FlashcardSerializer(flashcards, many=True).data)

      @detail_route(methods=['POST'])

      def enroll(self, request, pk):
          """
          Add the current user to a specified section
          If the class has a whitelist, but the user is not on the whitelist, the request will fail.
          ---

          view_mocker: flashcards.api.mock_no_params

          """

          try:
              self.get_object().enroll(request.user)
          except django.core.exceptions.PermissionDenied as e:
              raise PermissionDenied(e)
          except django.core.exceptions.ValidationError as e:
              raise ValidationError(e)

          return Response(status=HTTP_204_NO_CONTENT)

      @detail_route(methods=['POST'])

      def drop(self, request, pk):
          """
          Remove the current user from a specified section
          If the user is not in the class, the request will fail.
          ---

          view_mocker: flashcards.api.mock_no_params

          """

          try:
              self.get_object().drop(request.user)

          except django.core.exceptions.PermissionDenied as e:
              raise PermissionDenied(e)
          except django.core.exceptions.ValidationError as e:
              raise ValidationError(e)

          return Response(status=HTTP_204_NO_CONTENT)

      @list_route(methods=['GET'])

      def search(self, request):

          """
          Returns a list of sections which match a user's query

          ---
          parameters:
              - name: q
                description: space-separated list of terms
                required: true
                type: form

          response_serializer: SectionSerializer

          """

          query = request.GET.get('q', None)

          if not query: return Response('[]')

          qs = Section.search(query.split(' '))[:20]

          data = SectionSerializer(qs, many=True).data

          return Response(data)

      @detail_route(methods=['GET'])

      def deck(self, request, pk):

          """
          Gets the contents of a user's deck for a given section.
          """

          qs = request.user.get_deck(self.get_object())

          serializer = FlashcardSerializer(qs, many=True)
          return Response(serializer.data)

      @detail_route(methods=['GET'], permission_classes=[IsAuthenticated])

      def ordered_deck(self, request, pk):
          """
          Get a chronological order by material_date of flashcards for a section.
          This excludes hidden card.
          """

          qs = request.user.get_deck(self.get_object()).order_by('-material_date')

          serializer = FlashcardSerializer(qs, many=True)
          return Response(serializer.data)

      @detail_route(methods=['GET'])
      def feed(self, request, pk):
          """
          Gets the contents of a user's feed for a section.
          Exclude cards that are already in the user's deck
          """
          serializer = FlashcardSerializer(self.get_object().get_feed_for_user(request.user), many=True)
          return Response(serializer.data)

  class UserSectionListView(ListAPIView):

      serializer_class = DeepSectionSerializer

      permission_classes = [IsAuthenticated]

      def get_queryset(self):
          return self.request.user.sections.all()

      def paginate_queryset(self, queryset): return None

  class UserDetail(GenericAPIView):
      serializer_class = UserSerializer
      permission_classes = [IsAuthenticated]

      def patch(self, request, format=None):
          """
          Updates the user's password, or verifies their email address
          ---
          request_serializer: UserUpdateSerializer
          response_serializer: UserSerializer
          """
          data = UserUpdateSerializer(data=request.data, context={'user': request.user})
          data.is_valid(raise_exception=True)

          data = data.validated_data

  
          if 'new_password' in data:
              if not request.user.check_password(data['old_password']):
                  raise ValidationError('old_password is incorrect')

              request.user.set_password(data['new_password'])

              request.user.save()

          if 'confirmation_key' in data:
              try:
                  request.user.confirm_email(data['confirmation_key'])
              except EmailAddress.DoesNotExist:
                  raise ValidationError('confirmation_key is invalid')

  
          return Response(UserSerializer(request.user).data)
  
      def get(self, request, format=None):
          """
          Return data about the user
          ---
          response_serializer: UserSerializer
          """

          serializer = UserSerializer(request.user, context={'request': request})

          return Response(serializer.data)

      def delete(self, request):
          """
          Irrevocably delete the user and their data
  
          Yes, really
          """
          request.user.delete()
          return Response(status=HTTP_204_NO_CONTENT)

  @api_view(['POST'])
  def register(request, format=None):
      """
      Register a new user
      ---
      request_serializer: EmailPasswordSerializer
      response_serializer: UserSerializer
      """
      data = RegistrationSerializer(data=request.data)
      data.is_valid(raise_exception=True)

      User.objects.create_user(**data.validated_data)
      user = authenticate(**data.validated_data)
      auth.login(request, user)

      return Response(UserSerializer(request.user).data, status=HTTP_201_CREATED)

  @api_view(['POST'])
  def login(request):
      """
      Authenticates user and returns user data if valid.
      ---
      request_serializer: EmailPasswordSerializer
      response_serializer: UserSerializer
      """
  
      data = EmailPasswordSerializer(data=request.data)
      data.is_valid(raise_exception=True)
      user = authenticate(**data.validated_data)
  
      if user is None:
          raise AuthenticationFailed('Invalid email or password')
      if not user.is_active:
          raise NotAuthenticated('Account is disabled')
      auth.login(request, user)
      return Response(UserSerializer(request.user).data)

  @api_view(['POST'])

  @permission_classes((IsAuthenticated,))

  def logout(request, format=None):

      """

      Logs the authenticated user out.

      """

      auth.logout(request)
      return Response(status=HTTP_204_NO_CONTENT)

  @api_view(['POST'])
  def request_password_reset(request, format=None):
      """
      Send a password reset token/link to the provided email.
      ---
      request_serializer: PasswordResetRequestSerializer
      """
      data = PasswordResetRequestSerializer(data=request.data)
      data.is_valid(raise_exception=True)

      get_object_or_404(User, email=data['email'].value).request_password_reset()

      return Response(status=HTTP_204_NO_CONTENT)

  @api_view(['POST'])
  def reset_password(request, format=None):
      """
      Updates user's password to new password if token is valid.
      ---
      request_serializer: PasswordResetSerializer
      """
      data = PasswordResetSerializer(data=request.data)
      data.is_valid(raise_exception=True)

      user = User.objects.get(id=data['uid'].value)
      # Check token validity.

      if default_token_generator.check_token(user, data['token'].value):
          user.set_password(data['new_password'].value)
          user.save()
      else:
          raise ValidationError('Could not verify reset token')
      return Response(status=HTTP_204_NO_CONTENT)

  class FlashcardViewSet(GenericViewSet, CreateModelMixin, RetrieveModelMixin):

      queryset = Flashcard.objects.all()
      serializer_class = FlashcardSerializer

      permission_classes = [IsAuthenticated, IsEnrolledInAssociatedSection]

      # Override create in CreateModelMixin
      def create(self, request, *args, **kwargs):

          serializer = FlashcardSerializer(data=request.data)

          serializer.is_valid(raise_exception=True)

          data = serializer.validated_data

          if not request.user.is_in_section(data['section']):
              raise PermissionDenied('The user is not enrolled in that section')

          data['author'] = request.user
          flashcard = Flashcard.objects.create(**data)
          self.perform_create(flashcard)

          notify_new_card(flashcard)

          headers = self.get_success_headers(data)

          request.user.pull(flashcard)

          response_data = FlashcardSerializer(flashcard).data

          return Response(response_data, status=HTTP_201_CREATED, headers=headers)

      @detail_route(methods=['POST'])

      def unhide(self, request, pk):
          """

          Unhide the given card

          ---

          view_mocker: flashcards.api.mock_no_params

          """

          hide = get_object_or_404(FlashcardHide, user=request.user, flashcard=self.get_object())

          hide.delete()

          return Response(status=HTTP_204_NO_CONTENT)

      @detail_route(methods=['POST'])

      def report(self, request, pk):
          """

          Hide the given card

          ---

          view_mocker: flashcards.api.mock_no_params

          """

          self.get_object().report(request.user)

          return Response(status=HTTP_204_NO_CONTENT)

      hide = report

      @detail_route(methods=['POST'])

      def pull(self, request, pk):
          """
          Pull a card from the live feed into the user's deck.

          ---
          view_mocker: flashcards.api.mock_no_params

          """

  
          request.user.pull(self.get_object())

          return Response(status=HTTP_204_NO_CONTENT)

      @detail_route(methods=['POST'])
      def unpull(self, request, pk):
          """
          Unpull a card from the user's deck

          ---
          view_mocker: flashcards.api.mock_no_params

          """
          user = request.user
          flashcard = self.get_object()
          user.unpull(flashcard)
          return Response(status=HTTP_204_NO_CONTENT)

      def partial_update(self, request, *args, **kwargs):

          """
          Edit settings related to a card for the user.

          ---
          request_serializer: FlashcardUpdateSerializer

          """
          user = request.user

          flashcard = self.get_object()

          data = FlashcardUpdateSerializer(data=request.data)
          data.is_valid(raise_exception=True)
          new_flashcard = data.validated_data

          new_flashcard = flashcard.edit(user, new_flashcard)

          return Response(FlashcardSerializer(new_flashcard).data, status=HTTP_200_OK)

  class UserFlashcardQuizViewSet(GenericViewSet, CreateModelMixin, UpdateModelMixin):

      permission_classes = [IsAuthenticated, IsFlashcardReviewer]

      queryset = UserFlashcardQuiz.objects.all()
  
      def get_serializer_class(self):
          if self.request.method == 'POST':
              return QuizRequestSerializer
          return QuizAnswerRequestSerializer

  
      def create(self, request, *args, **kwargs):
          """
          Return a card based on the request params.
          :param request: A request object.
          :param format: Format of the request.
          :return: A response containing

          request_serializer: serializers.QuizRequestSerializer
          response_serializer: serializers.QuizResponseSerializer

          """

          serializer = QuizRequestSerializer(data=request.data)

          serializer.is_valid(raise_exception=True)

          data = serializer.validated_data
          user_flashcard_filter = UserFlashcard.objects.filter(
              user=request.user, flashcard__section__pk__in=data['sections'],
              flashcard__material_date__gte=data['material_date_begin'],
              flashcard__material_date__lte=data['material_date_end']
          )
  
          if not user_flashcard_filter.exists():
              raise ValidationError("No matching flashcard found in your decks")
  
          user_flashcard = user_flashcard_filter.order_by('?').first()

          mask = user_flashcard.get_mask().get_random_blank()

          user_flashcard_quiz = UserFlashcardQuiz(user_flashcard=user_flashcard,
                                                  blanked_word=user_flashcard.flashcard.text[slice(*mask)])

          user_flashcard_quiz.save()

          response = QuizResponseSerializer(instance=user_flashcard_quiz, mask=mask)
          return Response(response.data, status=HTTP_200_OK)

      def partial_update(self, request, *args, **kwargs):

          """
          Receive the user's response to the quiz.
          :param request: A request object.
          :param format: Format of the request.
          :return: A response containing

          request_serializer: serializers.QuizAnswerRequestSerializer

          """
          user_flashcard_quiz = self.get_object()
          serializer = QuizAnswerRequestSerializer(instance=user_flashcard_quiz, data=request.data)

          serializer.is_valid(raise_exception=True)

          serializer.update(user_flashcard_quiz, serializer.validated_data)
          return Response(status=HTTP_204_NO_CONTENT)