re2o/preferences/models.py

# -*- mode: python; coding: utf-8 -*-
# Re2o un logiciel d'administration développé initiallement au rezometz. Il
# se veut agnostique au réseau considéré, de manière à être installable en
# quelques clics.
#
# Copyright © 2017  Gabriel Détraz
# Copyright © 2017  Lara Kermarec
# Copyright © 2017  Augustin Lemesle
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
"""
Reglages généraux, machines, utilisateurs, mail, general pour l'application.
"""
from __future__ import unicode_literals
import os

from django.utils.functional import cached_property
from django.utils import timezone
from django.db import models
from django.db.models.signals import post_save
from django.dispatch import receiver
from django.core.cache import cache
from django.forms import ValidationError
from django.utils.translation import ugettext_lazy as _

import machines.models

from re2o.mixins import AclMixin, RevMixin
from re2o.aes_field import AESEncryptedField

from datetime import timedelta


class PreferencesModel(models.Model):
    """ Base object for the Preferences objects
    Defines methods to handle the cache of the settings (they should
    not change a lot) """
    @classmethod
    def set_in_cache(cls):
        """ Save the preferences in a server-side cache """
        instance, _created = cls.objects.get_or_create()
        cache.set(cls().__class__.__name__.lower(), instance, None)
        return instance

    @classmethod
    def get_cached_value(cls, key):
        """ Get the preferences from the server-side cache """
        instance = cache.get(cls().__class__.__name__.lower())
        if instance is None:
            instance = cls.set_in_cache()
        return getattr(instance, key)

    class Meta:
        abstract = True


class OptionalUser(AclMixin, PreferencesModel):
    """Options pour l'user : obligation ou nom du telephone,
    activation ou non du solde, autorisation du negatif, fingerprint etc"""

    is_tel_mandatory = models.BooleanField(default=True)
    gpg_fingerprint = models.BooleanField(default=True)
    all_can_create_club = models.BooleanField(
        default=False,
        help_text=_("Users can create a club.")
    )
    all_can_create_adherent = models.BooleanField(
        default=False,
        help_text=_("Users can create a member."),
    )

    shell_default = models.OneToOneField(
        'users.ListShell',
        on_delete=models.PROTECT,
        blank=True,
        null=True
    )
    self_change_shell = models.BooleanField(
        default=False,
        help_text=_("Users can edit their shell.")
    )
    self_change_room = models.BooleanField(
        default=False,
        help_text=_("Users can edit their room.")
    )
    local_email_accounts_enabled = models.BooleanField(
        default=False,
        help_text=_("Enable local email accounts for users.")
    )
    local_email_domain = models.CharField(
        max_length=32,
        default="@example.org",
        help_text=_("Domain to use for local email accounts")
    )
    max_email_address = models.IntegerField(
        default=15,
        help_text=_("Maximum number of local email addresses for a standard"
                    " user.")
    )
    delete_notyetactive = models.IntegerField(
        default=15,
        help_text=_("Not yet active users will be deleted after this number of"
                    " days.")
    )
    self_adhesion = models.BooleanField(
        default=False,
        help_text=_("A new user can create their account on Re2o.")
    )
    all_users_active = models.BooleanField(
        default=False,
        help_text=_("If True, all new created and connected users are active."
                    " If False, only when a valid registration has been paid.")
    )
    allow_archived_connexion = models.BooleanField(
        default=False,
        help_text=_("If True, archived users are allowed to connect.")
    )

    class Meta:
        permissions = (
            ("view_optionaluser", _("Can view the user options")),
        )
        verbose_name = _("user options")

    def clean(self):
        """Clean model:
        Check the mail_extension
        """
        if self.local_email_domain[0] != "@":
            raise ValidationError(_("Email domain must begin with @"))


@receiver(post_save, sender=OptionalUser)
def optionaluser_post_save(**kwargs):
    """Ecriture dans le cache"""
    user_pref = kwargs['instance']
    user_pref.set_in_cache()


class OptionalMachine(AclMixin, PreferencesModel):
    """Options pour les machines : maximum de machines ou d'alias par user
    sans droit, activation de l'ipv6"""

    SLAAC = 'SLAAC'
    DHCPV6 = 'DHCPV6'
    DISABLED = 'DISABLED'
    CHOICE_IPV6 = (
        (SLAAC, _("Autoconfiguration by RA")),
        (DHCPV6, _("IP addresses assigning by DHCPv6")),
        (DISABLED, _("Disabled")),
    )

    password_machine = models.BooleanField(default=False)
    max_lambdauser_interfaces = models.IntegerField(default=10)
    max_lambdauser_aliases = models.IntegerField(default=10)
    ipv6_mode = models.CharField(
        max_length=32,
        choices=CHOICE_IPV6,
        default='DISABLED'
    )
    create_machine = models.BooleanField(
        default=True
    )

    @cached_property
    def ipv6(self):
        """ Check if the IPv6 option is activated """
        return not self.get_cached_value('ipv6_mode') == 'DISABLED'

    class Meta:
        permissions = (
            ("view_optionalmachine", _("Can view the machine options")),
        )
        verbose_name = _("machine options")


@receiver(post_save, sender=OptionalMachine)
def optionalmachine_post_save(**kwargs):
    """Synchronisation ipv6 et ecriture dans le cache"""
    machine_pref = kwargs['instance']
    machine_pref.set_in_cache()
    if machine_pref.ipv6_mode != "DISABLED":
        for interface in machines.models.Interface.objects.all():
            interface.sync_ipv6()


class OptionalTopologie(AclMixin, PreferencesModel):
    """Reglages pour la topologie : mode d'accès radius, vlan où placer
    les machines en accept ou reject"""
    MACHINE = 'MACHINE'
    DEFINED = 'DEFINED'
    CHOICE_RADIUS = (
        (MACHINE, _("On the IP range's VLAN of the machine")),
        (DEFINED, _("Preset in 'VLAN for machines accepted by RADIUS'")),
    )
    CHOICE_PROVISION = (
        ('sftp', 'sftp'),
        ('tftp', 'tftp'),
    )

    switchs_web_management = models.BooleanField(
        default=False,
        help_text=_("Web management, activated in case of automatic provision")
    )
    switchs_web_management_ssl = models.BooleanField(
        default=False,
        help_text=_("SSL web management, make sure that a certificate is"
                    " installed on the switch")
    )
    switchs_rest_management = models.BooleanField(
        default=False,
        help_text=_("REST management, activated in case of automatic provision")
    )
    switchs_ip_type = models.OneToOneField(
        'machines.IpType',
        on_delete=models.PROTECT,
        blank=True,
        null=True,
        help_text=_("IP range for the management of switches")
    )
    switchs_provision = models.CharField(
        max_length=32,
        choices=CHOICE_PROVISION,
        default='tftp',
        help_text=_("Provision of configuration mode for switches")
    )
    sftp_login = models.CharField(
        max_length=32,
        null=True,
        blank=True,
        help_text=_("SFTP login for switches")
    )
    sftp_pass = AESEncryptedField(
        max_length=63,
        null=True,
        blank=True,
        help_text=_("SFTP password")
    )

    @cached_property
    def provisioned_switchs(self):
        """Liste des switches provisionnés"""
        from topologie.models import Switch
        return Switch.objects.filter(automatic_provision=True).order_by('interface__domain__name')

    @cached_property
    def switchs_management_interface(self):
        """Return the ip of the interface that the switch have to contact to get it's config"""
        if self.switchs_ip_type:
            from machines.models import Role, Interface
            return Interface.objects.filter(machine__interface__in=Role.interface_for_roletype("switch-conf-server")).filter(machine_type__ip_type=self.switchs_ip_type).first()
        else:
            return None

    @cached_property
    def switchs_management_interface_ip(self):
        """Same, but return the ipv4"""
        if not self.switchs_management_interface:
            return None
        return self.switchs_management_interface.ipv4

    @cached_property
    def switchs_management_sftp_creds(self):
        """Credentials des switchs pour provion sftp"""
        if self.sftp_login and self.sftp_pass:
            return {'login' : self.sftp_login, 'pass' : self.sftp_pass}
        else:
            return None

    @cached_property
    def switchs_management_utils(self):
        """Used for switch_conf, return a list of ip on vlans"""
        from machines.models import Role, Ipv6List, Interface
        def return_ips_dict(interfaces):
            return {'ipv4' : [str(interface.ipv4) for interface in interfaces], 'ipv6' : Ipv6List.objects.filter(interface__in=interfaces).values_list('ipv6', flat=True)}

        ntp_servers = Role.all_interfaces_for_roletype("ntp-server").filter(machine_type__ip_type=self.switchs_ip_type)
        log_servers = Role.all_interfaces_for_roletype("log-server").filter(machine_type__ip_type=self.switchs_ip_type)
        radius_servers = Role.all_interfaces_for_roletype("radius-server").filter(machine_type__ip_type=self.switchs_ip_type)
        dhcp_servers = Role.all_interfaces_for_roletype("dhcp-server")
        dns_recursive_servers = Role.all_interfaces_for_roletype("dns-recursive-server").filter(machine_type__ip_type=self.switchs_ip_type)
        subnet = None
        subnet6 = None
        if self.switchs_ip_type:
            subnet = self.switchs_ip_type.ip_set_full_info
            subnet6 = self.switchs_ip_type.ip6_set_full_info
        return {'ntp_servers': return_ips_dict(ntp_servers), 'log_servers': return_ips_dict(log_servers), 'radius_servers': return_ips_dict(radius_servers), 'dhcp_servers': return_ips_dict(dhcp_servers), 'dns_recursive_servers': return_ips_dict(dns_recursive_servers), 'subnet': subnet, 'subnet6': subnet6}

    @cached_property
    def provision_switchs_enabled(self):
        """Return true if all settings are ok : switchs on automatic provision,
        ip_type"""
        return bool(self.provisioned_switchs and self.switchs_ip_type and SwitchManagementCred.objects.filter(default_switch=True).exists() and self.switchs_management_interface_ip and bool(self.switchs_provision != 'sftp'  or self.switchs_management_sftp_creds))
    class Meta:
        permissions = (
            ("view_optionaltopologie", _("Can view the topology options")),
        )
        verbose_name = _("topology options")


@receiver(post_save, sender=OptionalTopologie)
def optionaltopologie_post_save(**kwargs):
    """Ecriture dans le cache"""
    topologie_pref = kwargs['instance']
    topologie_pref.set_in_cache()


class RadiusKey(AclMixin, models.Model):
    """Class of a radius key"""
    radius_key = AESEncryptedField(
        max_length=255,
        help_text=_("RADIUS key")
    )
    comment = models.CharField(
        max_length=255,
        null=True,
        blank=True,
        help_text=_("Comment for this key")
    )
    default_switch = models.BooleanField(
        default=True,
        unique=True,
        help_text=_("Default key for switches")
    )

    class Meta:
        permissions = (
            ("view_radiuskey", _("Can view a RADIUS key object")),
        )
        verbose_name = _("RADIUS key")
        verbose_name_plural = _("RADIUS keys")

    def __str__(self):
        return _("RADIUS key ") + str(self.id) + " " + str(self.comment)


class SwitchManagementCred(AclMixin, models.Model):
    """Class of a management creds of a switch, for rest management"""
    management_id = models.CharField(
        max_length=63,
        help_text=_("Switch login")
    )
    management_pass = AESEncryptedField(
        max_length=63,
        help_text=_("Password")
    )
    default_switch = models.BooleanField(
        default=True,
        unique=True,
        help_text=_("Default credentials for switches")
    )

    class Meta:
        permissions = (
            ("view_switchmanagementcred", _("Can view a switch management"
                                            " credentials object")),
        )
        verbose_name = _("switch management credentials")

    def __str__(self):
        return _("Switch login ") + str(self.management_id)


class Reminder(AclMixin, models.Model):
    """Options pour les mails de notification de fin d'adhésion.
    Days: liste des nombres de jours pour lesquells un mail est envoyé
    optionalMessage: message additionel pour le mail
    """

    days = models.IntegerField(
        default=7,
        unique=True,
        help_text=_("Delay between the email and the membership's end")
    )
    message = models.TextField(
        default="",
        null=True,
        blank=True,
        help_text=_("Message displayed specifically for this reminder")
    )

    class Meta:
        permissions = (
            ("view_reminder", _("Can view a reminder object")),
        )
        verbose_name = _("reminder")
        verbose_name_plural = _("reminders")

    def users_to_remind(self):
        from re2o.utils import all_has_access
        date = timezone.now().replace(minute=0,hour=0)
        futur_date = date + timedelta(days=self.days)
        users = all_has_access(futur_date).exclude(pk__in = all_has_access(futur_date + timedelta(days=1)))
        return users


class GeneralOption(AclMixin, PreferencesModel):
    """Options générales : nombre de resultats par page, nom du site,
    temps où les liens sont valides"""

    general_message_fr = models.TextField(
        default="",
        blank=True,
        help_text=_("General message displayed on the French version of the"
                    " website (e.g. in case of maintenance)")
    )
    general_message_en = models.TextField(
        default="",
        blank=True,
        help_text=_("General message displayed on the English version of the"
                    " website (e.g. in case of maintenance)")
    )
    search_display_page = models.IntegerField(default=15)
    pagination_number = models.IntegerField(default=25)
    pagination_large_number = models.IntegerField(default=8)
    req_expire_hrs = models.IntegerField(default=48)
    site_name = models.CharField(max_length=32, default="Re2o")
    email_from = models.EmailField(default="www-data@example.com")
    main_site_url = models.URLField(max_length=255, default="http://re2o.example.org")
    GTU_sum_up = models.TextField(
        default="",
        blank=True,
    )
    GTU = models.FileField(
        upload_to='',
        default="",
        null=True,
        blank=True,
    )

    class Meta:
        permissions = (
            ("view_generaloption", _("Can view the general options")),
        )
        verbose_name = _("general options")


@receiver(post_save, sender=GeneralOption)
def generaloption_post_save(**kwargs):
    """Ecriture dans le cache"""
    general_pref = kwargs['instance']
    general_pref.set_in_cache()


class Service(AclMixin, models.Model):
    """Liste des services affichés sur la page d'accueil : url, description,
    image et nom"""
    name = models.CharField(max_length=32)
    url = models.URLField()
    description = models.TextField()
    image = models.ImageField(upload_to='logo', blank=True)

    class Meta:
        permissions = (
            ("view_service", _("Can view the service options")),
        )
        verbose_name = _("service")
        verbose_name_plural =_("services")

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

class MailContact(AclMixin, models.Model):
    """Contact email adress with a commentary."""

    address = models.EmailField(
        default = "contact@example.org",
        help_text = _("Contact email address")
    )

    commentary = models.CharField(
        blank = True,
        null = True,
        help_text = _("Description of the associated email address."),
        max_length = 256
    )

    @cached_property
    def get_name(self):
        return self.address.split("@")[0]

    class Meta:
        permissions = (
            ("view_mailcontact", _("Can view a contact email address object")),
        )
        verbose_name = _("contact email address")
        verbose_name_plural = _("contact email addresses")

    def __str__(self):
        return(self.address)

class Mandate(RevMixin, AclMixin, models.Model):
    class Meta:
        verbose_name = _("Mandate")
        verbose_name_plural = _("Mandates")
        permissions = (
            ("view_mandate", _("Can view a mandate")),
        )

    president = models.ForeignKey(
        'users.User',
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        verbose_name=_("President of the association"),
        help_text=_("Displayed on subscription vouchers")
    )
    start_date = models.DateTimeField(
        verbose_name=_("start date")
    )
    end_date = models.DateTimeField(
        verbose_name=_("end date"),
        blank=True,
        null=True
    )

    @classmethod
    def get_mandate(cls, date=timezone.now):
        """"Find the mandate taking place at the given date. If none is found
        look for the nearest in the future. If none is found (again), look
        for the nearest in the past."""
        if callable(date):
            date = date()
        try:
            return cls.objects.get(
                start_date__gte=date, end_date__lte=date
            )
        except cls.DoesNotExist:
            try:
                return cls.objects.filter(start_date__gte=date).earliest('start_date')
            except cls.DoesNotExist:
                try:
                    return cls.objects.filter(start_date__lte=date).latest('start_date')
                except cls.DoesNotExist:
                    raise cls.DoesNotExist("No mandate have been created. Please go to the preferences page to create one.")


    def is_over(self):
        return self.end_date is None

class AssoOption(AclMixin, PreferencesModel):
    """Options générales de l'asso : siret, addresse, nom, etc"""

    name = models.CharField(
        default=_("Networking organisation school Something"),
        max_length=256
    )
    siret = models.CharField(default="00000000000000", max_length=32)
    adresse1 = models.CharField(default=_("Threadneedle Street"), max_length=128)
    adresse2 = models.CharField(default=_("London EC2R 8AH"), max_length=128)
    contact = models.EmailField(default="contact@example.org")
    telephone = models.CharField(max_length=15, default="0000000000")
    pseudo = models.CharField(default=_("Organisation"), max_length=32)
    utilisateur_asso = models.OneToOneField(
        'users.User',
        on_delete=models.PROTECT,
        blank=True,
        null=True
    )
    description = models.TextField(
        null=True,
        blank=True,
    )
    pres_name = models.CharField(
        max_length=255,
        default="",
        verbose_name=_("President of the association"),
        help_text=_("Displayed on subscription vouchers")
    )

    class Meta:
        permissions = (
            ("view_assooption", _("Can view the organisation options")),
        )
        verbose_name = _("organisation options")


@receiver(post_save, sender=AssoOption)
def assooption_post_save(**kwargs):
    """Ecriture dans le cache"""
    asso_pref = kwargs['instance']
    asso_pref.set_in_cache()


class HomeOption(AclMixin, PreferencesModel):
    """Settings of the home page (facebook/twitter etc)"""

    facebook_url = models.URLField(
        null=True,
        blank=True
    )
    twitter_url = models.URLField(
        null=True,
        blank=True
    )
    twitter_account_name = models.CharField(
        max_length=32,
        null=True,
        blank=True
    )

    class Meta:
        permissions = (
            ("view_homeoption", _("Can view the homepage options")),
        )
        verbose_name = _("homepage options")


@receiver(post_save, sender=HomeOption)
def homeoption_post_save(**kwargs):
    """Ecriture dans le cache"""
    home_pref = kwargs['instance']
    home_pref.set_in_cache()


class MailMessageOption(AclMixin, models.Model):
    """Reglages, mail de bienvenue et autre"""

    welcome_mail_fr = models.TextField(default="", help_text=_("Welcome email in French"))
    welcome_mail_en = models.TextField(default="", help_text=_("Welcome email in English"))

    class Meta:
        permissions = (
            ("view_mailmessageoption", _("Can view the email message"
                                         " options")),
        )
        verbose_name = _("email message options")


class RadiusAttribute(RevMixin, AclMixin, models.Model):
    class Meta:
        verbose_name = _("RADIUS attribute")
        verbose_name_plural = _("RADIUS attributes")

    attribute = models.CharField(
        max_length=255,
        verbose_name=_("Attribute"),
        help_text=_("See http://freeradius.org/rfc/attributes.html"),
    )
    value = models.CharField(
        max_length=255,
        verbose_name=_("Value")
    )
    comment = models.TextField(
        verbose_name=_("Comment"),
        help_text=_("Use this field to document this attribute."),
        blank=True,
        default=""
    )

    def __str__(self):
        return ' '.join([self.attribute, '=', self.value])



class RadiusOption(AclMixin, PreferencesModel):
    class Meta:
        verbose_name = _("RADIUS policy")
        verbose_name_plural = _("RADIUS policies")

    MACHINE = 'MACHINE'
    DEFINED = 'DEFINED'
    CHOICE_RADIUS = (
        (MACHINE, _("On the IP range's VLAN of the machine")),
        (DEFINED, _("Preset in 'VLAN for machines accepted by RADIUS'")),
    )
    REJECT = 'REJECT'
    SET_VLAN = 'SET_VLAN'
    CHOICE_POLICY = (
        (REJECT, _("Reject the machine")),
        (SET_VLAN, _("Place the machine on the VLAN"))
    )
    radius_general_policy = models.CharField(
        max_length=32,
        choices=CHOICE_RADIUS,
        default='DEFINED'
    )
    unknown_machine = models.CharField(
        max_length=32,
        choices=CHOICE_POLICY,
        default=REJECT,
        verbose_name=_("Policy for unknown machines"),
    )
    unknown_machine_vlan = models.ForeignKey(
        'machines.Vlan',
        on_delete=models.PROTECT,
        related_name='unknown_machine_vlan',
        blank=True,
        null=True,
        verbose_name=_("Unknown machines VLAN"),
        help_text=_("VLAN for unknown machines if not rejected")
    )
    unknown_machine_attributes = models.ManyToManyField(
        RadiusAttribute,
        related_name='unknown_machine_attribute',
        blank=True,
        verbose_name=_("Unknown machines attributes."),
        help_text=_("Answer attributes for unknown machines."),
    )
    unknown_port = models.CharField(
        max_length=32,
        choices=CHOICE_POLICY,
        default=REJECT,
        verbose_name=_("Policy for unknown ports"),
    )
    unknown_port_vlan = models.ForeignKey(
        'machines.Vlan',
        on_delete=models.PROTECT,
        related_name='unknown_port_vlan',
        blank=True,
        null=True,
        verbose_name=_("Unknown ports VLAN"),
        help_text=_("VLAN for unknown ports if not rejected")
    )
    unknown_port_attributes = models.ManyToManyField(
        RadiusAttribute,
        related_name='unknown_port_attribute',
        blank=True,
        verbose_name=_("Unknown ports attributes."),
        help_text=_("Answer attributes for unknown ports."),
    )
    unknown_room = models.CharField(
        max_length=32,
        choices=CHOICE_POLICY,
        default=REJECT,
        verbose_name=_("Policy for machines connecting from unregistered rooms"
                       " (relevant on ports with STRICT RADIUS mode)"),
    )
    unknown_room_vlan = models.ForeignKey(
        'machines.Vlan',
        related_name='unknown_room_vlan',
        on_delete=models.PROTECT,
        blank=True,
        null=True,
        verbose_name=_("Unknown rooms VLAN"),
        help_text=_("VLAN for unknown rooms if not rejected")
    )
    unknown_room_attributes = models.ManyToManyField(
        RadiusAttribute,
        related_name='unknown_room_attribute',
        blank=True,
        verbose_name=_("Unknown rooms attributes."),
        help_text=_("Answer attributes for unknown rooms."),
    )
    non_member = models.CharField(
        max_length=32,
        choices=CHOICE_POLICY,
        default=REJECT,
        verbose_name=_("Policy for non members"),
    )
    non_member_vlan = models.ForeignKey(
        'machines.Vlan',
        related_name='non_member_vlan',
        on_delete=models.PROTECT,
        blank=True,
        null=True,
        verbose_name=_("Non members VLAN"),
        help_text=_("VLAN for non members if not rejected")
    )
    non_member_attributes = models.ManyToManyField(
        RadiusAttribute,
        related_name='non_member_attribute',
        blank=True,
        verbose_name=_("Non member attributes."),
        help_text=_("Answer attributes for non members."),
    )
    banned = models.CharField(
        max_length=32,
        choices=CHOICE_POLICY,
        default=REJECT,
        verbose_name=_("Policy for banned users"),
    )
    banned_vlan = models.ForeignKey(
        'machines.Vlan',
        related_name='banned_vlan',
        on_delete=models.PROTECT,
        blank=True,
        null=True,
        verbose_name=_("Banned users VLAN"),
        help_text=_("VLAN for banned users if not rejected")
    )
    banned_attributes = models.ManyToManyField(
        RadiusAttribute,
        related_name='banned_attribute',
        blank=True,
        verbose_name=_("Banned attributes."),
        help_text=_("Answer attributes for banned users."),
    )
    vlan_decision_ok = models.OneToOneField(
        'machines.Vlan',
        on_delete=models.PROTECT,
        related_name='vlan_ok_option',
        blank=True,
        null=True
    )
    ok_attributes = models.ManyToManyField(
        RadiusAttribute,
        related_name='ok_attribute',
        blank=True,
        verbose_name=_("Accepted users attributes."),
        help_text=_("Answer attributes for accepted users."),
    )

    @classmethod
    def get_attributes(cls, name, attribute_kwargs={}):
        return (
            (
                str(attribute.attribute),
                str(attribute.value % attribute_kwargs)
            )
            for attribute in cls.get_cached_value(name).all()
        )


def default_invoice():
    tpl, _ = DocumentTemplate.objects.get_or_create(
        name="Re2o default invoice",
        template="templates/default_invoice.tex"
    )
    return tpl.id


def default_voucher():
    tpl, _ = DocumentTemplate.objects.get_or_create(
        name="Re2o default voucher",
        template="templates/default_voucher.tex"
    )
    return tpl.id


class CotisationsOption(AclMixin, PreferencesModel):
    class Meta:
        verbose_name = _("cotisations options")

    invoice_template = models.OneToOneField(
        'preferences.DocumentTemplate',
        verbose_name=_("Template for invoices"),
        related_name="invoice_template",
        on_delete=models.PROTECT,
        default=default_invoice,
    )
    voucher_template = models.OneToOneField(
        'preferences.DocumentTemplate',
        verbose_name=_("Template for subscription voucher"),
        related_name="voucher_template",
        on_delete=models.PROTECT,
        default=default_voucher,
    )
    send_voucher_mail = models.BooleanField(
        verbose_name=_("Send voucher by email when the invoice is controlled."),
        help_text=_("Be carefull, if no mandate is defined on the preferences page, errors will be triggered when generating vouchers."),
        default=False,
    )


class DocumentTemplate(RevMixin, AclMixin, models.Model):
    """Represent a template in order to create documents such as invoice or
    subscription voucher.
    """
    template = models.FileField(
        upload_to='templates/',
        verbose_name=_('template')
    )
    name = models.CharField(
        max_length=125,
        verbose_name=_('name'),
        unique=True
    )

    class Meta:
        verbose_name = _("document template")
        verbose_name_plural = _("document templates")

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

@receiver(models.signals.post_delete, sender=DocumentTemplate)
def auto_delete_file_on_delete(sender, instance, **kwargs):
    """
    Deletes file from filesystem
    when corresponding `DocumentTemplate` object is deleted.
    """
    if instance.template:
        if os.path.isfile(instance.template.path):
            os.remove(instance.template.path)


@receiver(models.signals.pre_save, sender=DocumentTemplate)
def auto_delete_file_on_change(sender, instance, **kwargs):
    """
    Deletes old file from filesystem
    when corresponding `DocumentTemplate` object is updated
    with new file.
    """
    if not instance.pk:
        return False

    try:
        old_file = DocumentTemplate.objects.get(pk=instance.pk).template
    except DocumentTemplate.DoesNotExist:
        return False

    new_file = instance.template
    if not old_file == new_file:
        if os.path.isfile(old_file.path):
            os.remove(old_file.path)