from django.core.exceptions import ValidationError
from django.db.models import Count, F, Max, OuterRef, Prefetch, Subquery
from django.db.models.functions import Coalesce
from django.http import Http404
from django.shortcuts import get_object_or_404
from django.utils.functional import cached_property
from django.utils.timezone import now
from django_filters.rest_framework import DjangoFilterBackend, FilterSet
from rest_framework import viewsets
from rest_framework.decorators import detail_route
from rest_framework.fields import DateTimeField
from rest_framework.response import Response

from pretix.api.serializers.checkin import CheckinListSerializer
from pretix.api.serializers.item import QuestionSerializer
from pretix.api.serializers.order import OrderPositionSerializer
from pretix.api.views import RichOrderingFilter
from pretix.api.views.order import OrderPositionFilter
from pretix.base.models import Checkin, CheckinList, Order, OrderPosition
from pretix.base.services.checkin import (
    CheckInError, RequiredQuestionsError, perform_checkin,
)
from pretix.helpers.database import FixedOrderBy


class CheckinListFilter(FilterSet):
    class Meta:
        model = CheckinList
        fields = ['subevent']


class CheckinListViewSet(viewsets.ModelViewSet):
    serializer_class = CheckinListSerializer
    queryset = CheckinList.objects.none()
    filter_backends = (DjangoFilterBackend,)
    filterset_class = CheckinListFilter
    permission = 'can_view_orders'
    write_permission = 'can_change_event_settings'

    def get_queryset(self):
        qs = self.request.event.checkin_lists.prefetch_related(
            'limit_products',
        )
        qs = CheckinList.annotate_with_numbers(qs, self.request.event)
        return qs

    def perform_create(self, serializer):
        serializer.save(event=self.request.event)
        serializer.instance.log_action(
            'pretix.event.checkinlist.added',
            user=self.request.user,
            auth=self.request.auth,
            data=self.request.data
        )

    def get_serializer_context(self):
        ctx = super().get_serializer_context()
        ctx['event'] = self.request.event
        return ctx

    def perform_update(self, serializer):
        serializer.save(event=self.request.event)
        serializer.instance.log_action(
            'pretix.event.checkinlist.changed',
            user=self.request.user,
            auth=self.request.auth,
            data=self.request.data
        )

    def perform_destroy(self, instance):
        instance.log_action(
            'pretix.event.checkinlist.deleted',
            user=self.request.user,
            auth=self.request.auth,
        )
        super().perform_destroy(instance)

    @detail_route(methods=['GET'])
    def status(self, *args, **kwargs):
        clist = self.get_object()
        cqs = Checkin.objects.filter(
            position__order__event=clist.event,
            position__order__status__in=[Order.STATUS_PAID] + ([Order.STATUS_PENDING] if clist.include_pending else []),
            list=clist
        )
        pqs = OrderPosition.objects.filter(
            order__event=clist.event,
            order__status__in=[Order.STATUS_PAID] + ([Order.STATUS_PENDING] if clist.include_pending else []),
            subevent=clist.subevent,
        )
        if not clist.all_products:
            pqs = pqs.filter(item__in=clist.limit_products.values_list('id', flat=True))

        ev = clist.subevent or clist.event
        response = {
            'event': {
                'name': str(ev.name),
            },
            'checkin_count': cqs.count(),
            'position_count': pqs.count()
        }

        op_by_item = {
            p['item']: p['cnt']
            for p in pqs.order_by().values('item').annotate(cnt=Count('id'))
        }
        op_by_variation = {
            p['variation']: p['cnt']
            for p in pqs.order_by().values('variation').annotate(cnt=Count('id'))
        }
        c_by_item = {
            p['position__item']: p['cnt']
            for p in cqs.order_by().values('position__item').annotate(cnt=Count('id'))
        }
        c_by_variation = {
            p['position__variation']: p['cnt']
            for p in cqs.order_by().values('position__variation').annotate(cnt=Count('id'))
        }

        if not clist.all_products:
            items = clist.limit_products
        else:
            items = clist.event.items

        response['items'] = []
        for item in items.order_by('category__position', 'position', 'pk').prefetch_related('variations'):
            i = {
                'id': item.pk,
                'name': str(item),
                'admission': item.admission,
                'checkin_count': c_by_item.get(item.pk, 0),
                'position_count': op_by_item.get(item.pk, 0),
                'variations': []
            }
            for var in item.variations.all():
                i['variations'].append({
                    'id': var.pk,
                    'value': str(var),
                    'checkin_count': c_by_variation.get(var.pk, 0),
                    'position_count': op_by_variation.get(var.pk, 0),
                })
            response['items'].append(i)

        return Response(response)


class CheckinOrderPositionFilter(OrderPositionFilter):

    def has_checkin_qs(self, queryset, name, value):
        return queryset.filter(last_checked_in__isnull=not value)


class CheckinListPositionViewSet(viewsets.ReadOnlyModelViewSet):
    serializer_class = OrderPositionSerializer
    queryset = OrderPosition.objects.none()
    filter_backends = (DjangoFilterBackend, RichOrderingFilter)
    ordering = ('attendee_name_cached', 'positionid')
    ordering_fields = (
        'order__code', 'order__datetime', 'positionid', 'attendee_name',
        'last_checked_in', 'order__email',
    )
    ordering_custom = {
        'attendee_name': {
            '_order': F('display_name').asc(nulls_first=True),
            'display_name': Coalesce('attendee_name_cached', 'addon_to__attendee_name_cached')
        },
        '-attendee_name': {
            '_order': F('display_name').desc(nulls_last=True),
            'display_name': Coalesce('attendee_name_cached', 'addon_to__attendee_name_cached')
        },
        'last_checked_in': {
            '_order': FixedOrderBy(F('last_checked_in'), nulls_first=True),
        },
        '-last_checked_in': {
            '_order': FixedOrderBy(F('last_checked_in'), nulls_last=True, descending=True),
        },
    }

    filterset_class = CheckinOrderPositionFilter
    permission = 'can_view_orders'
    write_permission = 'can_change_orders'

    @cached_property
    def checkinlist(self):
        try:
            return get_object_or_404(CheckinList, event=self.request.event, pk=self.kwargs.get("list"))
        except ValueError:
            raise Http404()

    def get_queryset(self):
        cqs = Checkin.objects.filter(
            position_id=OuterRef('pk'),
            list_id=self.checkinlist.pk
        ).order_by().values('position_id').annotate(
            m=Max('datetime')
        ).values('m')

        qs = OrderPosition.objects.filter(
            order__event=self.request.event,
            order__status__in=[Order.STATUS_PAID, Order.STATUS_PENDING] if self.checkinlist.include_pending else [Order.STATUS_PAID],
            subevent=self.checkinlist.subevent
        ).annotate(
            last_checked_in=Subquery(cqs)
        ).prefetch_related(
            Prefetch(
                lookup='checkins',
                queryset=Checkin.objects.filter(list_id=self.checkinlist.pk)
            )
        ).select_related('item', 'variation', 'order', 'addon_to')

        if not self.checkinlist.all_products:
            qs = qs.filter(item__in=self.checkinlist.limit_products.values_list('id', flat=True))

        return qs

    @detail_route(methods=['POST'])
    def redeem(self, *args, **kwargs):
        force = bool(self.request.data.get('force', False))
        ignore_unpaid = bool(self.request.data.get('ignore_unpaid', False))
        nonce = self.request.data.get('nonce')
        op = self.get_object()

        if 'datetime' in self.request.data:
            dt = DateTimeField().to_internal_value(self.request.data.get('datetime'))
        else:
            dt = now()

        given_answers = {}
        if 'answers' in self.request.data:
            aws = self.request.data.get('answers')
            for q in op.item.questions.filter(ask_during_checkin=True):
                if str(q.pk) in aws:
                    try:
                        given_answers[q] = q.clean_answer(aws[str(q.pk)])
                    except ValidationError:
                        pass

        try:
            perform_checkin(
                op=op,
                clist=self.checkinlist,
                given_answers=given_answers,
                force=force,
                ignore_unpaid=ignore_unpaid,
                nonce=nonce,
                datetime=dt,
                questions_supported=self.request.data.get('questions_supported', True)
            )
        except RequiredQuestionsError as e:
            return Response({
                'status': 'incomplete',
                'questions': [
                    QuestionSerializer(q).data for q in e.questions
                ]
            }, status=400)
        except CheckInError as e:
            return Response({
                'status': 'error',
                'reason': e.code
            }, status=400)
        else:
            return Response({
                'status': 'ok',
            }, status=201)