from django.db import models
from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType
from django.core.validators import MaxValueValidator
from django.core.urlresolvers import reverse
from django.core.exceptions import ValidationError

from djadhere.utils import is_overlapping


class Payment(models.Model):
    TRANSFERT = 0
    WITHDRAWAL = 1
    PAYMENT_CHOICES = (
        (TRANSFERT, 'Virement'),
        (WITHDRAWAL, 'Prélèvement'),
    )
    limit = models.Q(app_label='adhesions', model='Adherent') \
        | models.Q(app_label='services', model='Service')
    reason_type = models.ForeignKey(ContentType, on_delete=models.CASCADE,
                                    limit_choices_to=limit)
    reason_id = models.PositiveIntegerField()
    reason = GenericForeignKey('reason_type', 'reason_id')
    amount = models.DecimalField(max_digits=9, decimal_places=2, verbose_name='Montant')
    period = models.PositiveIntegerField(validators=[MaxValueValidator(12)],
                                         verbose_name='Période (mois) (0 si non récurrent)')
    payment_method = models.IntegerField(choices=PAYMENT_CHOICES,
                                         verbose_name='Méthode de paiement')
    start = models.DateField(verbose_name='Date de paiement ou de début de paiement')
    end = models.DateField(null=True, blank=True, verbose_name='Date de fin de paiement (si récurrent)')
    validated = models.BooleanField(default=False, verbose_name='Paiement validé')

    class Meta:
        verbose_name = 'paiement'
        permissions = (
            ('validate_payment', 'Peut valider les paiements'),
        )

    def payment_type_verbose(self):
        if self.reason_type.app_label == 'adhesions' \
                and self.reason_type.model == 'adherent':
            return 'Cotisation'
        if self.reason_type.app_label == 'services' \
                and self.reason_type.model == 'service':
            return 'Service (%s)' % self.reason.service_type
    payment_type_verbose.short_description = 'Type'

    def period_verbose(self):
        if self.period == 0:
            return 'non récurrent'
        elif self.period == 1:
            return 'mensuel'
        elif self.period == 3:
            return 'trimestriel'
        elif self.period == 6:
            return 'biannuel'
        elif self.period == 12:
            return 'annuel'
        else:
            return '%d mois' % self.period

    # Note: 'adherent' is already used as the related_query_name
    #        of the GenericRelation on Adherent
    def get_adherent(self):
        if self.reason_type.app_label == 'adhesions' \
                and self.reason_type.model == 'adherent':
            return self.reason
        if self.reason_type.app_label == 'services' \
                and self.reason_type.model == 'service':
            return self.reason.adherent
    get_adherent.short_description = 'Adhérent'

    def clean(self):
        super().clean()
        # S’il s’agit d’un paiement non récurrent, le champ end doit rester blanc
        if self.period == 0 and self.end:
            raise ValidationError({'end': "Un paiement non récurrent ne doit pas avoir de date de fin."})
        # Vérification de la cohérence des champs start et end
        if self.end and self.start > self.end:
            raise ValidationError("La date de début de paiement doit être antérieur à la date de fin de paiement.")
        # Vérification de l’absence de chevauchement avec une période existante
        if self.reason:
            payments = Payment.objects.filter(reason_type=self.reason_type, reason_id=self.reason_id)
            if is_overlapping(self, payments):
                raise ValidationError("Les périodes de paiement ne doivent pas se chevaucher.")


    def __str__(self):
        s = str(self.amount) + '€'
        if self.period:
            if self.period == 1:
                s += '/mois'
            elif self.period == 12:
                s += '/an'
            else:
                s += '/%d mois' % self.period
        if self.payment_method == self.TRANSFERT:
            s += ' (virement)'
        elif self.payment_method == self.WITHDRAWAL:
            s += ' (prélèvement)'
        return s