import datetime

from django.core.mail import get_connection, mail_admins
from django.core.management import BaseCommand
from django.db import transaction
from django.db.models import F, Max, OuterRef, Subquery
from django.db.models.functions import Greatest
from django.utils import timezone

from desecapi import models, serializers, views
from desecapi.pdns_change_tracker import PDNSChangeTracker


fresh_days = 183
notice_days_notify = 28
notice_days_warn = 7


class Command(BaseCommand):
    base_queryset = models.Domain.objects.exclude(
        renewal_state=models.Domain.RenewalState.IMMORTAL
    ).filter(owner__is_active=True)
    _rrsets_outer_queryset = models.RRset.objects.filter(domain=OuterRef("pk")).values(
        "domain"
    )  # values() is GROUP BY
    _max_touched = Subquery(
        _rrsets_outer_queryset.annotate(max_touched=Max("touched")).values(
            "max_touched"
        )
    )

    @classmethod
    def renew_touched_domains(cls):
        recently_active_domains = cls.base_queryset.annotate(
            last_active=Greatest(cls._max_touched, "published")
        ).filter(
            last_active__date__gte=timezone.localdate() - datetime.timedelta(days=183),
            renewal_changed__lt=F("last_active"),
        )

        print(
            "Renewing domains:", *recently_active_domains.values_list("name", flat=True)
        )
        recently_active_domains.update(
            renewal_state=models.Domain.RenewalState.FRESH,
            renewal_changed=F("last_active"),
        )

    @classmethod
    def warn_domain_deletion(cls, renewal_state, notice_days, inactive_days):
        # We act when `renewal_changed` is at least this date (or older)
        inactive_threshold = timezone.localdate() - datetime.timedelta(
            days=inactive_days
        )
        # Filter candidates which have the state of interest, at least since the calculated date
        expiry_candidates = cls.base_queryset.filter(
            renewal_state=renewal_state, renewal_changed__date__lte=inactive_threshold
        )

        # Group domains by user, so that we can send one message per user
        domain_user_map = {}
        for domain in expiry_candidates.order_by("name"):
            if domain.owner not in domain_user_map:
                domain_user_map[domain.owner] = []
            domain_user_map[domain.owner].append(domain)

        # Prepare and send emails, and keep renewal status in sync
        context = {
            "deletion_date": timezone.localdate() + datetime.timedelta(days=notice_days)
        }
        for user, domains in domain_user_map.items():
            with transaction.atomic():
                # Update renewal status of the user's affected domains, but don't commit before sending the email
                actions = []
                for domain in domains:
                    domain.renewal_state += 1
                    domain.renewal_changed = timezone.now()
                    domain.save(update_fields=["renewal_state", "renewal_changed"])
                    actions.append(
                        models.AuthenticatedRenewDomainBasicUserAction(
                            user=user, domain=domain
                        )
                    )
                serializers.AuthenticatedRenewDomainBasicUserActionSerializer(
                    actions, many=True, context=context
                ).save()

    @classmethod
    def delete_domains(cls, inactive_days):
        expired_domains = (
            cls.base_queryset.filter(renewal_state=models.Domain.RenewalState.WARNED)
            .annotate(last_active=Greatest(cls._max_touched, "published"))
            .filter(
                renewal_changed__date__lte=timezone.localdate()
                - datetime.timedelta(days=notice_days_warn),
                last_active__date__lte=timezone.localdate()
                - datetime.timedelta(days=inactive_days),
            )
        )

        for domain in expired_domains:
            with PDNSChangeTracker():
                domain.delete()
            if not domain.owner.domains.exists():
                domain.owner.delete()
        # Do one large delegation update
        with PDNSChangeTracker():
            for domain in expired_domains:
                views.DomainViewSet.auto_delegate(domain)

    def handle(self, *args, **kwargs):
        try:
            # Reset renewal status for domains that have recently been touched
            self.renew_touched_domains()

            # Announce domain deletion in `notice_days_notice` days if not yet notified (FRESH) and inactive for
            # `inactive_days` days. Updates status from FRESH to NOTIFIED.
            self.warn_domain_deletion(
                models.Domain.RenewalState.FRESH, notice_days_notify, fresh_days
            )

            # After `notice_days_notify - notice_days_warn` more days, warn again if the status has not changed
            # Updates status from NOTIFIED to WARNED.
            self.warn_domain_deletion(
                models.Domain.RenewalState.NOTIFIED,
                notice_days_warn,
                notice_days_notify - notice_days_warn,
            )

            # Finally, delete domains inactive for `inactive_days + notice_days_notify` days if status has not changed
            self.delete_domains(fresh_days + notice_days_notify)
        except Exception as e:
            subject = "Renewal Exception!"
            message = f"{type(e)}\n\n{str(e)}"
            print(f"Chores exception: {type(e)}, {str(e)}")
            mail_admins(
                subject,
                message,
                connection=get_connection(
                    "django.core.mail.backends.smtp.EmailBackend"
                ),
            )