from django.db.models import Q
from rest_framework.viewsets import ModelViewSet
from rest_framework.generics import ListAPIView
from rest_framework.permissions import IsAuthenticated
from rest_framework.authentication import TokenAuthentication
from rest_framework.decorators import action
from rest_framework.response import Response
from django.shortcuts import get_object_or_404
from utils.pagination import StandardResultsSetPagination

from apps.quiz.models import Quiz, Question, QuizParticipant
from apps.course.models import Course, CourseLesson, Participant
from apps.course.models.course import extract_text_from_json
from apps.account.models import User
from apps.account.permissions import IsPanelUser

from apps.quiz.serializers.admin import (
    AdminCourseSerializer,
    AdminCourseLessonSerializer,
    AdminQuizListSerializer,
    AdminQuizDetailSerializer,
    AdminQuestionSerializer,
    AdminQuizParticipantSerializer,
    AdminQuizAbsenteeSerializer
)


def is_professor(request):
    return getattr(request.user, 'user_type', None) == 'professor'


def find_matching_course_ids(search_term: str):
    normalized = (search_term or "").strip().lower()
    if not normalized:
        return []

    matching_ids = list(
        Course.objects.filter(
            Q(title__icontains=search_term) | Q(slug__icontains=search_term)
        ).values_list("id", flat=True)
    )

    if matching_ids:
        return matching_ids

    for course in Course.objects.all().only("id", "title", "slug"):
        title_text = extract_text_from_json(course.title).lower()
        slug_text = extract_text_from_json(course.slug).lower()
        if normalized in title_text or normalized in slug_text:
            matching_ids.append(course.id)

    return matching_ids


def find_matching_lesson_ids(search_term: str):
    normalized = (search_term or "").strip().lower()
    if not normalized:
        return []

    matching_ids = []
    for lesson in CourseLesson.objects.select_related("lesson").all():
        lesson_title = extract_text_from_json(
            lesson.title or (lesson.lesson.title if lesson.lesson else [])
        ).lower()
        if normalized in lesson_title:
            matching_ids.append(lesson.id)

    return matching_ids


def find_matching_quiz_ids(search_term: str):
    normalized = (search_term or "").strip().lower()
    if not normalized:
        return []

    matching_ids = []
    for quiz in Quiz.objects.all().only("id", "title", "description"):
        title_text = extract_text_from_json(quiz.title).lower()
        description_text = extract_text_from_json(quiz.description).lower()
        if normalized in title_text or normalized in description_text:
            matching_ids.append(quiz.id)

    return matching_ids


class AdminQuizViewSet(ModelViewSet):
    """
    Admin CRUD ViewSet for Quiz management.
    Professors can only access quizzes of their own courses.
    """
    permission_classes = [IsAuthenticated, IsPanelUser]
    authentication_classes = [TokenAuthentication]
    pagination_class = StandardResultsSetPagination

    def get_serializer_class(self):
        if self.action == 'list':
            return AdminQuizListSerializer
        return AdminQuizDetailSerializer

    def get_queryset(self):
        queryset = Quiz.objects.all().select_related('course', 'lesson')

        # Professors can only see quizzes of their own courses
        if is_professor(self.request):
            queryset = queryset.filter(course__professor_id=self.request.user.id)

        # Handle Search
        search_query = self.request.query_params.get('search', None)
        has_search = False
        if search_query:
            has_search = True
            matching_course_ids = find_matching_course_ids(search_query)
            matching_lesson_ids = find_matching_lesson_ids(search_query)
            matching_quiz_ids = find_matching_quiz_ids(search_query)
            from django.db.models import Case, When, Value, IntegerField
            queryset = queryset.filter(
                Q(id__in=matching_quiz_ids) |
                Q(course_id__in=matching_course_ids) |
                Q(lesson_id__in=matching_lesson_ids)
            ).annotate(
                search_relevance=Case(
                    When(id__in=matching_quiz_ids, then=Value(2)),
                    default=Value(1),
                    output_field=IntegerField()
                )
            )

        # Handle Course Filter
        course_id = self.request.query_params.get('course', None)
        if course_id:
            queryset = queryset.filter(course_id=course_id)

        # Handle Lesson Filter
        lesson_id = self.request.query_params.get('lesson', None)
        if lesson_id:
            try:
                lesson_obj = CourseLesson.objects.get(id=lesson_id)
                course = lesson_obj.course
                lessons = list(CourseLesson.objects.filter(
                    course=course,
                    is_active=True
                ).order_by('chapter__priority', 'priority'))
                try:
                    pos = lessons.index(lesson_obj) + 1
                    queryset = queryset.filter(
                        Q(lesson_id=lesson_id) | (Q(course=course) & Q(lesson_number=pos))
                    )
                except ValueError:
                    queryset = queryset.filter(lesson_id=lesson_id)
            except CourseLesson.DoesNotExist:
                queryset = queryset.filter(lesson_id=lesson_id)

        # Handle Status Filter
        status_param = self.request.query_params.get('status', None)
        if status_param is not None:
            if status_param.lower() == 'true':
                queryset = queryset.filter(status=True)
            elif status_param.lower() == 'false':
                queryset = queryset.filter(status=False)

        if has_search:
            return queryset.order_by('-search_relevance', '-id')
        return queryset.order_by('-id')

    @action(detail=True, methods=['get'])
    def participants(self, request, pk=None):
        """
        Returns two lists:
        1. Participants: users who have participated in the quiz.
        2. Absentees: users who are enrolled in the course but have not participated.
        """
        quiz = self.get_object()

        # 1. Fetch participants
        participants_qs = QuizParticipant.objects.filter(quiz=quiz).select_related('user').prefetch_related('answers')
        participants_serializer = AdminQuizParticipantSerializer(participants_qs, many=True)

        # 2. Fetch absentees
        absentees_data = []
        if quiz.course:
            # Enrolled course student IDs
            enrolled_student_ids = Participant.objects.filter(
                course=quiz.course,
                is_active=True
            ).values_list('student_id', flat=True)

            # Participated user IDs
            participated_user_ids = participants_qs.values_list('user_id', flat=True)

            # Absentee IDs
            absentee_ids = set(enrolled_student_ids) - set(participated_user_ids)

            # Fetch User details for absentees
            absentees_qs = User.objects.filter(id__in=absentee_ids)
            absentees_serializer = AdminQuizAbsenteeSerializer(absentees_qs, many=True)
            absentees_data = absentees_serializer.data

        return Response({
            'participants': participants_serializer.data,
            'absentees': absentees_data
        })


class AdminQuestionViewSet(ModelViewSet):
    """
    Admin CRUD ViewSet for Question management.
    Professors can only access questions of quizzes belonging to their own courses.
    """
    serializer_class = AdminQuestionSerializer
    permission_classes = [IsAuthenticated, IsPanelUser]
    authentication_classes = [TokenAuthentication]
    pagination_class = None

    def get_queryset(self):
        queryset = Question.objects.all()

        # Professors can only see questions of their own courses' quizzes
        if is_professor(self.request):
            queryset = queryset.filter(quiz__course__professor_id=self.request.user.id)

        quiz_id = self.request.query_params.get('quiz_id', None)
        if not quiz_id:
            # Fallback parameter name
            quiz_id = self.request.query_params.get('quiz', None)

        if quiz_id:
            queryset = queryset.filter(quiz_id=quiz_id)

        return queryset.order_by('priority', 'id')

    @action(detail=False, methods=['post'])
    def reorder(self, request):
        """
        Reorders questions in bulk.
        Accepts a list of question IDs.
        Format:
        {
            "question_ids": [10, 12, 11, 15]
        }
        """
        question_ids = request.data.get('question_ids', [])
        if not question_ids:
            return Response({'error': 'question_ids list is required'}, status=400)

        # Update priority for each question based on its position in the list
        from django.db import transaction
        questions = Question.objects.filter(id__in=question_ids)
        question_map = {q.id: q for q in questions}

        with transaction.atomic():
            for idx, q_id in enumerate(question_ids):
                if q_id in question_map:
                    question = question_map[q_id]
                    question.priority = idx + 1
                    question.save(update_fields=['priority'])

        return Response({'status': 'success'})


class AdminCourseListView(ListAPIView):
    """
    Dropdown listing helper for all courses.
    Professors only see their own courses.
    """
    serializer_class = AdminCourseSerializer
    permission_classes = [IsAuthenticated, IsPanelUser]
    authentication_classes = [TokenAuthentication]
    pagination_class = None  # Return all courses for dropdown usage

    def get_queryset(self):
        queryset = Course.objects.all().order_by('-id')
        if is_professor(self.request):
            queryset = queryset.filter(professor_id=self.request.user.id)
        return queryset


class AdminLessonListView(ListAPIView):
    """
    Dropdown listing helper for lessons. Filtered by course_id.
    Professors only see lessons of their own courses.
    """
    serializer_class = AdminCourseLessonSerializer
    permission_classes = [IsAuthenticated, IsPanelUser]
    authentication_classes = [TokenAuthentication]
    pagination_class = None  # Return all matching lessons for dropdown usage

    def get_queryset(self):
        course_id = self.request.query_params.get('course_id', None)
        if course_id:
            qs = CourseLesson.objects.filter(course_id=course_id).select_related('lesson').order_by('priority')
        else:
            qs = CourseLesson.objects.all().select_related('lesson').order_by('-id')

        # Professors only see lessons of their own courses
        if is_professor(self.request):
            qs = qs.filter(course__professor_id=self.request.user.id)

        return qs