coin/coin/billing/models.py

# -*- coding: utf-8 -*-
from __future__ import unicode_literals

import datetime
import random
import uuid
import os
import re
from decimal import Decimal

from django.conf import settings
from django.db import models, transaction
from django.db.models.signals import post_save
from django.dispatch import receiver
from django.utils.encoding import python_2_unicode_compatible


from coin.offers.models import OfferSubscription
from coin.members.models import Member
from coin.html2pdf import render_as_pdf
from coin.utils import private_files_storage, start_of_month, end_of_month, \
                       disable_for_loaddata, postgresql_regexp
from coin.isp_database.context_processors import branding


def invoice_pdf_filename(instance, filename):
    """Nom et chemin du fichier pdf à stocker pour les factures"""
    member_id = instance.member.id if instance.member else 0
    return 'invoices/%d_%s_%s.pdf' % (member_id,
                                      instance.number,
                                      uuid.uuid4())

@python_2_unicode_compatible
class InvoiceNumber:
    """ Logic and validation of invoice numbers

    Defines invoice numbers serie in a way that is legal in france.

    https://www.service-public.fr/professionnels-entreprises/vosdroits/F23208#fiche-item-3

    Our format is YYYY-MM-XXXXXX
    - YYYY the year of the bill
    - MM month of the bill
    - XXXXXX a per-month sequence
    """
    RE_INVOICE_NUMBER = re.compile(
        r'(?P<year>\d{4})-(?P<month>\d{2})-(?P<index>\d{6})')

    def __init__(self, date, index):
        self.date = date
        self.index = index

    def get_next(self):
        return InvoiceNumber(self.date, self.index + 1)

    def __str__(self):
        return '{:%Y-%m}-{:0>6}'.format(self.date, self.index)

    @classmethod
    def parse(cls, string):
        m = cls.RE_INVOICE_NUMBER.match(string)
        if not m:
            raise ValueError('Not a valid invoice number: "{}"'.format(string))

        return cls(
            datetime.date(
                year=int(m.group('year')),
                month=int(m.group('month')),
                day=1),
            int(m.group('index')))

    @staticmethod
    def time_sequence_filter(date, field_name='date'):
        """ Build queryset filter to be used to get the invoices from the
        numbering sequence of a given date.

        :param field_name: the invoice field name to filter on.

        :type date: datetime
        :rtype: dict
        """

        return {'{}__month'.format(field_name): date.month}


class InvoiceQuerySet(models.QuerySet):
    def get_next_invoice_number(self, date):
        last_invoice_number_str = self._get_last_invoice_number(date)

        if last_invoice_number_str is None:
            # It's the first bill of the month
            invoice_number = InvoiceNumber(date, 1)
        else:
            invoice_number = InvoiceNumber.parse(last_invoice_number_str).get_next()

        return str(invoice_number)

    def _get_last_invoice_number(self, date):
        same_seq_filter = InvoiceNumber.time_sequence_filter(date)
        return self.filter(**same_seq_filter).with_valid_number().aggregate(
            models.Max('number'))['number__max']

    def with_valid_number(self):
        """ Excludes previous numbering schemes or draft invoices
        """
        return self.filter(number__regex=postgresql_regexp(
            InvoiceNumber.RE_INVOICE_NUMBER))

class Invoice(models.Model):

    INVOICES_STATUS_CHOICES = (
        ('open', 'À payer'),
        ('closed', 'Réglée'),
        ('trouble', 'Litige')
    )

    validated = models.BooleanField(default=False, verbose_name='validée',
                                    help_text='Once validated, a PDF is generated'
                                    ' and the invoice cannot be modified')
    number = models.CharField(max_length=25,
                              unique=True,
                              verbose_name='numéro')
    status = models.CharField(max_length=50, choices=INVOICES_STATUS_CHOICES,
                              default='open',
                              verbose_name='statut')
    date = models.DateField(
        default=datetime.date.today, null=True, verbose_name='date',
        help_text='Cette date sera définie à la date de validation dans la facture finale')
    date_due = models.DateField(
        null=True, blank=True,
        verbose_name="date d'échéance de paiement",
        help_text='Le délai de paiement sera fixé à {} jours à la validation si laissé vide'.format(settings.PAYMENT_DELAY))
    member = models.ForeignKey(Member, null=True, blank=True, default=None,
                               related_name='invoices',
                               verbose_name='membre',
                               on_delete=models.SET_NULL)
    pdf = models.FileField(storage=private_files_storage,
                           upload_to=invoice_pdf_filename,
                           null=True, blank=True,
                           verbose_name='PDF')

    def save(self, *args, **kwargs):
        # First save to get a PK
        super(Invoice, self).save(*args, **kwargs)
        # Then use that pk to build draft invoice number
        if not self.validated and self.pk and not self.number:
            self.number = 'DRAFT-{}'.format(self.pk)
            self.save()

    def amount(self):
        """
        Calcul le montant de la facture
        en fonction des éléments de détails
        """
        total = Decimal('0.0')
        for detail in self.details.all():
            total += detail.total()
        return total.quantize(Decimal('0.01'))
    amount.short_description = 'Montant'

    def amount_before_tax(self):
        total = Decimal('0.0')
        for detail in self.details.all():
            total += detail.amount
        return total.quantize(Decimal('0.01'))
    amount_before_tax.short_description = 'Montant HT'

    def amount_paid(self):
        """
        Calcul le montant payé de la facture en fonction des éléments
        de paiements
        """
        total = Decimal('0.0')
        for payment in self.payments.all():
            total += payment.amount
        return total.quantize(Decimal('0.01'))
    amount_paid.short_description = 'Montant payé'

    def amount_remaining_to_pay(self):
        """
        Calcul le montant restant à payer
        """
        return self.amount() - self.amount_paid()
    amount_remaining_to_pay.short_description = 'Reste à payer'

    def has_owner(self, username):
        """
        Check if passed username (ex gmajax) is owner of the invoice
        """
        return (self.member and self.member.username == username)

    def generate_pdf(self):
        """
        Make and store a pdf file for the invoice
        """
        context = {"invoice": self}
        context.update(branding(None))
        pdf_file = render_as_pdf('billing/invoice_pdf.html', context)
        self.pdf.save('%s.pdf' % self.number, pdf_file)

    @transaction.atomic
    def validate(self):
        """
        Switch invoice to validate mode. This set to False the draft field
        and generate the pdf
        """
        self.date = datetime.date.today()
        if not self.date_due:
            self.date_due = self.date + datetime.timedelta(days=settings.PAYMENT_DELAY)
        self.number = Invoice.objects.get_next_invoice_number(self.date)
        self.validated = True
        self.save()
        self.generate_pdf()
        
        assert self.pdf_exists()

    def pdf_exists(self):
        return (self.validated
                and bool(self.pdf)
                and private_files_storage.exists(self.pdf.name))

    def get_absolute_url(self):
        from django.core.urlresolvers import reverse
        return reverse('billing:invoice', args=[self.number])

    def __unicode__(self):
        return '#%s %0.2f€ %s' % (self.number, self.amount(), self.date_due)

    class Meta:
        verbose_name = 'facture'

    objects = InvoiceQuerySet().as_manager()

class InvoiceDetail(models.Model):

    label = models.CharField(max_length=100)
    amount = models.DecimalField(max_digits=5, decimal_places=2,
                                 verbose_name='montant')
    quantity = models.DecimalField(null=True, verbose_name='quantité',
                                   default=1.0, decimal_places=2, max_digits=4)
    tax = models.DecimalField(null=True, default=0.0, decimal_places=2,
                              max_digits=4, verbose_name='TVA',
                              help_text='en %')
    invoice = models.ForeignKey(Invoice, verbose_name='facture',
                                related_name='details')
    offersubscription = models.ForeignKey(OfferSubscription, null=True,
                                          blank=True, default=None,
                                          verbose_name='abonnement')
    period_from = models.DateField(
        default=start_of_month,
        null=True,
        blank=True,
        verbose_name='début de période',
        help_text='Date de début de période sur laquelle est facturé cet item')
    period_to = models.DateField(
        default=end_of_month,
        null=True,
        blank=True,
        verbose_name='fin de période',
        help_text='Date de fin de période sur laquelle est facturé cet item')

    def __unicode__(self):
        return self.label

    def total(self):
        """Calcul le total"""
        return (self.amount * (self.tax / Decimal('100.0') +
                               Decimal('1.0')) *
                self.quantity).quantize(Decimal('0.01'))

    class Meta:
        verbose_name = 'détail de facture'


class Payment(models.Model):

    PAYMENT_MEAN_CHOICES = (
        ('cash', 'Espèces'),
        ('check', 'Chèque'),
        ('transfer', 'Virement'),
        ('other', 'Autre')
    )

    payment_mean = models.CharField(max_length=100, null=True,
                                    default='transfer',
                                    choices=PAYMENT_MEAN_CHOICES,
                                    verbose_name='moyen de paiement')
    amount = models.DecimalField(max_digits=5, decimal_places=2, null=True,
                                 verbose_name='montant')
    date = models.DateField(default=datetime.date.today)
    invoice = models.ForeignKey(Invoice, verbose_name='facture',
                                related_name='payments')

    def __unicode__(self):
        return 'Paiment de %0.2f€' % self.amount

    class Meta:
        verbose_name = 'paiement'


@receiver(post_save, sender=Payment)
@disable_for_loaddata
def set_invoice_as_paid_if_needed(sender, instance, **kwargs):
    """
    Lorsqu'un paiement est enregistré, vérifie si la facture est alors
    complétement payée. Dans ce cas elle passe en réglée
    """
    if (instance.invoice.amount_paid() >= instance.invoice.amount() and
            instance.invoice.status == 'open'):
        instance.invoice.status = 'closed'
        instance.invoice.save()