"""
Leaderboard views for user rankings
"""
from datetime import timedelta

from django.db.models import Count, Sum
from django.db.models.functions import Coalesce
from django.utils import timezone
from rest_framework.decorators import api_view, permission_classes
from rest_framework.permissions import AllowAny
from rest_framework.response import Response

from apps.moderation.models import EditSubmission
from apps.reviews.models import Review
from apps.rides.models import RideCredit


@api_view(['GET'])
@permission_classes([AllowAny])
def leaderboard(request):
    """
    Get user leaderboard data.

    Query params:
    - category: 'credits' | 'reviews' | 'contributions' (default: credits)
    - period: 'all' | 'monthly' | 'weekly' (default: all)
    - limit: int (default: 25, max: 100)
    """
    category = request.query_params.get('category', 'credits')
    period = request.query_params.get('period', 'all')
    limit = min(int(request.query_params.get('limit', 25)), 100)

    # Calculate date filter based on period
    date_filter = None
    if period == 'weekly':
        date_filter = timezone.now() - timedelta(days=7)
    elif period == 'monthly':
        date_filter = timezone.now() - timedelta(days=30)

    if category == 'credits':
        return _get_credits_leaderboard(date_filter, limit)
    elif category == 'reviews':
        return _get_reviews_leaderboard(date_filter, limit)
    elif category == 'contributions':
        return _get_contributions_leaderboard(date_filter, limit)
    else:
        return Response({'error': 'Invalid category'}, status=400)


def _get_credits_leaderboard(date_filter, limit):
    """Top users by total ride credits."""
    queryset = RideCredit.objects.all()

    if date_filter:
        queryset = queryset.filter(created_at__gte=date_filter)

    # Aggregate credits per user
    users_data = queryset.values('user_id', 'user__username', 'user__display_name').annotate(
        total_credits=Coalesce(Sum('count'), 0),
        unique_rides=Count('ride', distinct=True),
    ).order_by('-total_credits')[:limit]

    results = []
    for rank, entry in enumerate(users_data, 1):
        results.append({
            'rank': rank,
            'user_id': entry['user_id'],
            'username': entry['user__username'],
            'display_name': entry['user__display_name'] or entry['user__username'],
            'total_credits': entry['total_credits'],
            'unique_rides': entry['unique_rides'],
        })

    return Response({
        'category': 'credits',
        'results': results,
    })


def _get_reviews_leaderboard(date_filter, limit):
    """Top users by review count."""
    queryset = Review.objects.all()

    if date_filter:
        queryset = queryset.filter(created_at__gte=date_filter)

    # Count reviews per user
    users_data = queryset.values('user_id', 'user__username', 'user__display_name').annotate(
        review_count=Count('id'),
    ).order_by('-review_count')[:limit]

    results = []
    for rank, entry in enumerate(users_data, 1):
        results.append({
            'rank': rank,
            'user_id': entry['user_id'],
            'username': entry['user__username'],
            'display_name': entry['user__display_name'] or entry['user__username'],
            'review_count': entry['review_count'],
        })

    return Response({
        'category': 'reviews',
        'results': results,
    })


def _get_contributions_leaderboard(date_filter, limit):
    """Top users by approved contributions."""
    queryset = EditSubmission.objects.filter(status='approved')

    if date_filter:
        queryset = queryset.filter(created_at__gte=date_filter)

    # Count contributions per user
    users_data = queryset.values('submitted_by_id', 'submitted_by__username', 'submitted_by__display_name').annotate(
        contribution_count=Count('id'),
    ).order_by('-contribution_count')[:limit]

    results = []
    for rank, entry in enumerate(users_data, 1):
        results.append({
            'rank': rank,
            'user_id': entry['submitted_by_id'],
            'username': entry['submitted_by__username'],
            'display_name': entry['submitted_by__display_name'] or entry['submitted_by__username'],
            'contribution_count': entry['contribution_count'],
        })

    return Response({
        'category': 'contributions',
        'results': results,
    })