from django.db import models
from django.db.models import Q
from django.core.validators import MaxValueValidator
from django.utils import timezone
from django.contrib.auth.models import Group
from django.contrib.contenttypes.fields import GenericRelation
from django.core.exceptions import ValidationError
from django.urls import reverse
from django.utils import timezone
from django.core.exceptions import PermissionDenied

from djadhere.utils import get_active_filter, is_overlapping
from adhesions.models import Adhesion
from banking.models import Payment


class IPResource(models.Model):
    ip = models.GenericIPAddressField(verbose_name='IP')
    mask = models.PositiveIntegerField(validators=[MaxValueValidator(128)],
                                       default=0, verbose_name='Masque')

    @property
    def in_use(self):
        return self.allocation is not None

    @property
    def allocation(self):
        try:
            return self.allocations.get(get_active_filter())
        except ResourceAllocation.DoesNotExist:
            return None

    class Meta:
        verbose_name = 'ressource IP'
        verbose_name_plural = 'ressources IP'

    def get_absolute_url(self):
        return reverse('ip-detail', kwargs={'pk': self.pk})

    def __str__(self):
        r = str(self.ip)
        if self.mask:
            r += '/%d' % self.mask
        return r


class ServiceType(models.Model):
    name = models.CharField(max_length=64, verbose_name='Nom', unique=True)
    group = models.ForeignKey(Group, null=True, blank=True,
                              verbose_name='Groupe de gestion',
                              related_name='service_types')

    class Meta:
        verbose_name = 'type de service'
        verbose_name_plural = 'types de service'

    def get_absolute_url(self):
        return reverse('servicetype-detail', kwargs={'pk': self.pk})

    def __str__(self):
        return self.name


class Service(models.Model):
    adhesion = models.ForeignKey(Adhesion, verbose_name='Adhérent', related_name='services')
    service_type = models.ForeignKey(ServiceType, related_name='services',
                                     verbose_name='Type de service')
    label = models.CharField(blank=True, default='', max_length=128)
    notes = models.TextField(blank=True, default='')
    active = models.BooleanField(default=True, verbose_name='actif')
    created = models.DateTimeField(auto_now_add=True)
    contributions = GenericRelation(Payment,
                                   content_type_field='reason_type',
                                   object_id_field='reason_id',
                                   related_query_name='service')

    @property
    def contribution(self):
        try:
            return self.contributions.exclude(period=0).get(get_active_filter())
        except Payment.DoesNotExist:
            return None
        # MultipleObjectsReturned non catché volontairement, cf remarque adhesions.Adhesion.contribution

    @property
    def active_allocations(self):
        return self.allocations.filter(get_active_filter())

    @property
    def inactive_allocations(self):
        return self.allocations.exclude(get_active_filter())

    def clean(self):
        super().clean()
        # Vérification de l’unicité par type de service du label
        if self.label != '' and Service.objects.exclude(pk=self.pk).filter(service_type=self.service_type, label=self.label):
            raise ValidationError("Un service du même type existe déjà avec ce label.")

    def get_absolute_url(self):
        return reverse('service-detail', kwargs={'pk': self.pk})

    def __str__(self):
        s = str(self.service_type)
        if self.label:
            s += ' ' + self.label
        return s


class ResourceAllocation(models.Model):
    resource = models.ForeignKey(IPResource, verbose_name='Ressource', related_name='allocations', related_query_name='allocation')
    service = models.ForeignKey(Service, related_name='allocations', related_query_name='allocation')
    start = models.DateTimeField(verbose_name='Début de la période d’allocation', default=timezone.now)
    end = models.DateTimeField(null=True, blank=True, verbose_name='Fin de la période d’allocation')

    @property
    def active(self):
        return ResourceAllocation.objects.filter(pk=self.pk).filter(get_active_filter()).exists()

    def clean(self):
        super().clean()
        # Vérification de la cohérence des champs start et end
        if self.end and self.start > self.end:
            raise ValidationError("La date de début de l’allocation doit être antérieur "
                                  "à la date de fin de l’allocation.")
        # Vérification de l’abscence de chevauchement de la période d’allocation
        if self.resource_id:
            allocations = ResourceAllocation.objects.filter(resource__pk=self.resource.pk)
            if is_overlapping(self, allocations):
                raise ValidationError("La période d’allocation de cette ressource chevauche "
                                        "avec une période d’allocation précédente.")

    # Penser à appeler la méthode save !
    def deallocate(self):
        if not self.active:
            raise PermissionDenied
        self.end = timezone.now()

    class Meta:
        verbose_name = 'allocation'
        verbose_name_plural = 'allocations'
        ordering = ['-start']

    def get_absolute_url(self):
        return reverse('ip-detail', kwargs={'pk': self.resource.pk})

    def __str__(self):
        return str(self.resource)