djadhere/banking/models.py

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


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)')
    payment_method = models.IntegerField(choices=PAYMENT_CHOICES,
                                         verbose_name='Méthode de paiement')
    date = models.DateField(verbose_name='Date de paiement ou de début de paiement')

    class Meta:
        verbose_name = 'paiement'

    def reason_verbose(self):
        if self.reason_type.app_label == 'adhesions':
            return 'Cotisation de %s' % self.reason
        if self.reason_type.app_label == 'services':
            return 'Service %s' % self.reason
    reason_verbose.short_description = 'Paiement'


    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