from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework.permissions import IsAuthenticated, IsAdminUser
from django.utils import timezone
from datetime import timedelta
from django.db.models import Count, Sum, Q
from django.db.models.functions import TruncDate

from apps.account.models import User, LoginHistory
from apps.course.models import Course, Participant, CourseLiveSession
from apps.course.models.course import extract_text_from_json
from apps.quiz.models import QuizParticipant
from apps.blog.models import Blog
from apps.chat.models import ChatMessage, RoomMessage
from apps.transaction.models import TransactionParticipant
from apps.certificate.models import Certificate
from rest_framework.authentication import TokenAuthentication

class AdminDashboardStatsView(APIView):
    authentication_classes = [TokenAuthentication]
    permission_classes = [IsAuthenticated, IsAdminUser]

    def get(self, request):
        now = timezone.now()
        thirty_days_ago = now - timedelta(days=30)

        # ---------------------------------------------------------
        # 1. CARDS & BASIC STATS
        # ---------------------------------------------------------
        active_students = User.objects.filter(
            Q(user_type=User.UserType.STUDENT) | Q(user_type=User.UserType.CLIENT),
            is_active=True
        ).count()
        professors = User.objects.filter(user_type=User.UserType.PROFESSOR, is_active=True).count()
        active_courses = Course.objects.filter(status__contains=[{"title": Course.StatusChoices.ONGOING}]).count()
        total_blogs = Blog.objects.count()
        pending_certificates = Certificate.objects.filter(status='pending').count()
        active_live_sessions = CourseLiveSession.objects.filter(ended_at__isnull=True).count()

        # Revenue (30d sum of successful transactions)
        revenue_result = TransactionParticipant.objects.filter(
            status=TransactionParticipant.TransactionStatus.SUCCESS,
            created_at__gte=thirty_days_ago
        ).aggregate(total=Sum('price'))
        revenue_30d = float(revenue_result['total'] or 0.0)

        # Private vs Group Chat Usage
        chat_types = RoomMessage.objects.values('room_type').annotate(count=Count('id'))
        chat_type_stats = {item['room_type']: item['count'] for item in chat_types}

        # ---------------------------------------------------------
        # 2. CHARTS DATA
        # ---------------------------------------------------------
        
        # Payment Methods (Pie Chart)
        payment_methods = TransactionParticipant.objects.values('payment_method').annotate(total=Count('id'))
        payment_method_chart = [
            {"name": item['payment_method'], "value": item['total']} 
            for item in payment_methods
        ]

        # Transaction Status (Donut Chart)
        transaction_status = TransactionParticipant.objects.values('status').annotate(total=Count('id'))
        transaction_chart = [
            {"name": item['status'], "value": item['total']} 
            for item in transaction_status
        ]

        # Global Student Distribution (Bar Chart)
        top_countries = LoginHistory.objects.exclude(country__isnull=True).exclude(country="").values('country').annotate(
            count=Count('id')
        ).order_by('-count')[:5]
        country_chart = [{"country": item['country'], "students": item['count']} for item in top_countries]

        # New User Registrations Trend (Line Chart)
        registrations = User.objects.filter(date_joined__gte=thirty_days_ago).annotate(
            date=TruncDate('date_joined')
        ).values('date').annotate(count=Count('id')).order_by('date')
        registration_chart = [{"date": item['date'].strftime('%Y-%m-%d'), "users": item['count']} for item in registrations]

        # Community Chat Volume Trend (Area Chart)
        chat_volume = ChatMessage.objects.filter(sent_at__gte=thirty_days_ago).annotate(
            date=TruncDate('sent_at')
        ).values('date').annotate(count=Count('id')).order_by('date')
        chat_chart = [{"date": item['date'].strftime('%Y-%m-%d'), "messages": item['count']} for item in chat_volume]

        # Course Pipeline (Stacked Bar)
        course_pipeline = {"name": "Courses"}
        for choice in Course.StatusChoices.values:
            course_pipeline[choice] = Course.objects.filter(status__contains=[{"title": choice}]).count()

        # Course Efficacy: Completed vs Enrolled (Bar Chart)
        # We take the top 5 courses, check how many users are enrolled, and how many have at least 1 completed lesson
        top_courses_qs = Course.objects.annotate(participant_count=Count('participants')).order_by('-participant_count')[:5]
        course_efficacy = []
        for course in top_courses_qs:
            enrolled = course.participant_count
            completed = Participant.objects.filter(
                course=course, 
                student__lesson_completions__course_lesson__course=course
            ).distinct().count()
            title_text = extract_text_from_json(course.title)
            course_efficacy.append({
                "title": title_text[:20] + "..." if len(title_text) > 20 else title_text,
                "enrolled": enrolled,
                "completed": completed
            })

        # ---------------------------------------------------------
        # 3. LISTS & LEADERBOARDS
        # ---------------------------------------------------------
        
        # Top 5 Courses (List)
        top_courses_list = [
            {
                "id": c.id,
                "title": extract_text_from_json(c.title),
                "professor": c.professor.fullname if c.professor else "Unknown",
                "participants": c.participant_count
            } for c in top_courses_qs
        ]

        # Top 5 Blogs (List)
        top_blogs = Blog.objects.order_by('-views_count')[:5]
        top_blogs_list = [
            {"id": b.id, "title": b._extract_text_from_json(b.title), "views": b.views_count} 
            for b in top_blogs
        ]

        # Top Performing Students (Leaderboard)
        top_students = QuizParticipant.objects.select_related('user').order_by('-total_score', 'total_timing')[:5]
        leaderboard = [
            {"id": s.user.id, "name": s.user.fullname, "score": s.total_score, "time": s.total_timing} 
            for s in top_students
        ]

        return Response({
            "cards": {
                "active_students": active_students,
                "professors": professors,
                "active_courses": active_courses,
                "total_blogs": total_blogs,
                "revenue_30d": revenue_30d,
                "pending_certificates": pending_certificates,
                "active_live_sessions": active_live_sessions,
                "group_rooms": chat_type_stats.get('group', 0),
                "private_rooms": chat_type_stats.get('private', 0),
            },
            "charts": {
                "transactions_status": transaction_chart,
                "payment_methods": payment_method_chart,
                "countries": country_chart,
                "registrations": registration_chart,
                "chat_volume": chat_chart,
                "course_pipeline": [course_pipeline],
                "course_efficacy": course_efficacy
            },
            "lists": {
                "top_courses": top_courses_list,
                "top_blogs": top_blogs_list,
                "leaderboard": leaderboard
            }
        })