Sith/counter/models.py

# -*- coding:utf-8 -*
#
# Copyright 2016,2017
# - Skia <skia@libskia.so>
#
# Ce fichier fait partie du site de l'Association des Étudiants de l'UTBM,
# http://ae.utbm.fr.
#
# This program is free software; you can redistribute it and/or modify it under
# the terms of the GNU General Public License a published by the Free Software
# Foundation; either version 3 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 Sofware Foundation, Inc., 59 Temple
# Place - Suite 330, Boston, MA 02111-1307, USA.
#
#

from sith.settings import SITH_COUNTER_OFFICES, SITH_MAIN_CLUB
from django.db import models
from django.utils.translation import gettext_lazy as _
from django.utils import timezone
from django.conf import settings
from django.urls import reverse
from django.core.validators import MinLengthValidator
from django.forms import ValidationError
from django.utils.functional import cached_property

from datetime import timedelta, date
import random
import string
import os
import base64
import datetime

from club.models import Club, Membership
from accounting.models import CurrencyField
from core.models import Group, User, Notification
from subscription.models import Subscription


class Customer(models.Model):
    """
    This class extends a user to make a customer. It adds some basic customers informations, such as the accound ID, and
    is used by other accounting classes as reference to the customer, rather than using User
    """

    user = models.OneToOneField(User, primary_key=True, on_delete=models.CASCADE)
    account_id = models.CharField(_("account id"), max_length=10, unique=True)
    amount = CurrencyField(_("amount"))
    recorded_products = models.IntegerField(_("recorded product"), default=0)

    class Meta:
        verbose_name = _("customer")
        verbose_name_plural = _("customers")
        ordering = ["account_id"]

    def __str__(self):
        return "%s - %s" % (self.user.username, self.account_id)

    @property
    def can_record(self):
        return self.recorded_products > -settings.SITH_ECOCUP_LIMIT

    def can_record_more(self, number):
        return self.recorded_products - number >= -settings.SITH_ECOCUP_LIMIT

    @property
    def can_buy(self) -> bool:
        """
        Check if whether this customer has the right to
        purchase any item.
        This must be not confused with the Product.can_be_sold_to(user)
        method as the present method returns an information
        about a customer whereas the other tells something
        about the relation between a User (not a Customer,
        don't mix them) and a Product.
        """
        return self.user.subscriptions.last() and (
            date.today()
            - self.user.subscriptions.order_by("subscription_end")
            .last()
            .subscription_end
        ) < timedelta(days=90)

    @staticmethod
    def generate_account_id(number):
        number = str(number)
        letter = random.choice(string.ascii_lowercase)
        while Customer.objects.filter(account_id=number + letter).exists():
            letter = random.choice(string.ascii_lowercase)
        return number + letter

    def save(self, allow_negative=False, is_selling=False, *args, **kwargs):
        """
        is_selling : tell if the current action is a selling
        allow_negative : ignored if not a selling. Allow a selling to put the account in negative
        Those two parameters avoid blocking the save method of a customer if his account is negative
        """
        if self.amount < 0 and (is_selling and not allow_negative):
            raise ValidationError(_("Not enough money"))
        super(Customer, self).save(*args, **kwargs)

    def recompute_amount(self):
        self.amount = 0
        for r in self.refillings.all():
            self.amount += r.amount
        for s in self.buyings.filter(payment_method="SITH_ACCOUNT"):
            self.amount -= s.quantity * s.unit_price
            self.save()

    def get_absolute_url(self):
        return reverse("core:user_account", kwargs={"user_id": self.user.pk})

    def get_full_url(self):
        return "".join(["https://", settings.SITH_URL, self.get_absolute_url()])


class ProductType(models.Model):
    """
    This describes a product type
    Useful only for categorizing, changes are made at the product level for now
    """

    name = models.CharField(_("name"), max_length=30)
    description = models.TextField(_("description"), null=True, blank=True)
    comment = models.TextField(_("comment"), null=True, blank=True)
    icon = models.ImageField(upload_to="products", null=True, blank=True)

    # priority holds no real backend logic but helps to handle the order in which
    # the items are to be shown to the user
    priority = models.PositiveIntegerField(default=0)

    class Meta:
        verbose_name = _("product type")
        ordering = ["-priority", "name"]

    def is_owned_by(self, user):
        """
        Method to see if that object can be edited by the given user
        """
        if user.is_in_group(settings.SITH_GROUP_ACCOUNTING_ADMIN_ID):
            return True
        return False

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse("counter:producttype_list")


class Product(models.Model):
    """
    This describes a product, with all its related informations
    """

    name = models.CharField(_("name"), max_length=64)
    description = models.TextField(_("description"), blank=True)
    product_type = models.ForeignKey(
        ProductType,
        related_name="products",
        verbose_name=_("product type"),
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
    )
    code = models.CharField(_("code"), max_length=16, blank=True)
    purchase_price = CurrencyField(_("purchase price"))
    selling_price = CurrencyField(_("selling price"))
    special_selling_price = CurrencyField(_("special selling price"))
    icon = models.ImageField(
        upload_to="products", null=True, blank=True, verbose_name=_("icon")
    )
    club = models.ForeignKey(
        Club, related_name="products", verbose_name=_("club"), on_delete=models.CASCADE
    )
    limit_age = models.IntegerField(_("limit age"), default=0)
    tray = models.BooleanField(_("tray price"), default=False)
    parent_product = models.ForeignKey(
        "self",
        related_name="children_products",
        verbose_name=_("parent product"),
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
    )
    buying_groups = models.ManyToManyField(
        Group, related_name="products", verbose_name=_("buying groups"), blank=True
    )
    archived = models.BooleanField(_("archived"), default=False)

    class Meta:
        verbose_name = _("product")

    @property
    def is_record_product(self):
        return settings.SITH_ECOCUP_CONS == self.id

    @property
    def is_unrecord_product(self):
        return settings.SITH_ECOCUP_DECO == self.id

    def is_owned_by(self, user):
        """
        Method to see if that object can be edited by the given user
        """
        if user.is_in_group(
            settings.SITH_GROUP_ACCOUNTING_ADMIN_ID
        ) or user.is_in_group(settings.SITH_GROUP_COUNTER_ADMIN_ID):
            return True
        return False

    def get_absolute_url(self):
        return reverse("counter:product_list")

    def can_be_sold_to(self, user: User) -> bool:
        """
        Check if whether the user given in parameter has the right to buy
        this product or not.

        This must be not confused with the Customer.can_buy()
        method as the present method returns an information
        about the relation between a User and a Product,
        whereas the other tells something about a Customer
        (and not a user, they are not the same model).

        :return: True if the user can buy this product else False
        """
        if not self.buying_groups.exists():
            return True
        for group in self.buying_groups.all():
            if user.is_in_group(group.name):
                return True
        return False

    def __str__(self):
        return "%s (%s)" % (self.name, self.code)


class Counter(models.Model):
    name = models.CharField(_("name"), max_length=30)
    club = models.ForeignKey(
        Club, related_name="counters", verbose_name=_("club"), on_delete=models.CASCADE
    )
    products = models.ManyToManyField(
        Product, related_name="counters", verbose_name=_("products"), blank=True
    )
    type = models.CharField(
        _("counter type"),
        max_length=255,
        choices=[("BAR", _("Bar")), ("OFFICE", _("Office")), ("EBOUTIC", _("Eboutic"))],
    )
    sellers = models.ManyToManyField(
        User, verbose_name=_("sellers"), related_name="counters", blank=True
    )
    edit_groups = models.ManyToManyField(
        Group, related_name="editable_counters", blank=True
    )
    view_groups = models.ManyToManyField(
        Group, related_name="viewable_counters", blank=True
    )
    token = models.CharField(_("token"), max_length=30, null=True, blank=True)

    class Meta:
        verbose_name = _("counter")

    def __getattribute__(self, name):
        if name == "edit_groups":
            return Group.objects.filter(
                name=self.club.unix_name + settings.SITH_BOARD_SUFFIX
            ).all()
        return object.__getattribute__(self, name)

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        if self.type == "EBOUTIC":
            return reverse("eboutic:main")
        return reverse("counter:details", kwargs={"counter_id": self.id})

    def is_owned_by(self, user):
        mem = self.club.get_membership_for(user)
        if mem and mem.role >= 7:
            return True
        return user.is_in_group(settings.SITH_GROUP_COUNTER_ADMIN_ID)

    def can_be_viewed_by(self, user):
        if self.type == "BAR":
            return True
        return (
            user.is_in_group(settings.SITH_MAIN_BOARD_GROUP)
            or user in self.sellers.all()
        )

    def gen_token(self):
        """Generate a new token for this counter"""
        self.token = "".join(
            random.choice(string.ascii_letters + string.digits) for x in range(30)
        )
        self.save()

    def add_barman(self, user):
        """
        Logs a barman in to the given counter
        A user is stored as a tuple with its login time
        """
        Permanency(user=user, counter=self, start=timezone.now(), end=None).save()

    def del_barman(self, user):
        """
        Logs a barman out and store its permanency
        """
        perm = Permanency.objects.filter(counter=self, user=user, end=None).all()
        for p in perm:
            p.end = p.activity
            p.save()

    @cached_property
    def barmen_list(self):
        return self.get_barmen_list()

    def get_barmen_list(self):
        """
        Returns the barman list as list of User

        Also handle the timeout of the barmen
        """
        pl = Permanency.objects.filter(counter=self, end=None).all()
        bl = []
        for p in pl:
            if timezone.now() - p.activity < timedelta(
                minutes=settings.SITH_BARMAN_TIMEOUT
            ):
                bl.append(p.user)
            else:
                p.end = p.activity
                p.save()
        return bl

    def get_random_barman(self):
        """
        Return a random user being currently a barman
        """
        bl = self.get_barmen_list()
        return bl[random.randrange(0, len(bl))]

    def update_activity(self):
        """
        Update the barman activity to prevent timeout
        """
        for p in Permanency.objects.filter(counter=self, end=None).all():
            p.save()  # Update activity

    def is_open(self):
        return len(self.barmen_list) > 0

    def is_inactive(self):
        """
        Returns True if the counter self is inactive from SITH_COUNTER_MINUTE_INACTIVE's value minutes, else False
        """
        return self.is_open() and (
            (timezone.now() - self.permanencies.order_by("-activity").first().activity)
            > datetime.timedelta(minutes=settings.SITH_COUNTER_MINUTE_INACTIVE)
        )

    def barman_list(self):
        """
        Returns the barman id list
        """
        return [b.id for b in self.get_barmen_list()]

    def can_refill(self):
        """
        Show if the counter authorize the refilling with physic money
        """

        if (
            self.id in SITH_COUNTER_OFFICES
        ):  # If the counter is the counters 'AE' or 'BdF', the refiling are authorized
            return True

        is_ae_member = False
        ae = Club.objects.get(unix_name=SITH_MAIN_CLUB["unix_name"])
        for barman in self.get_barmen_list():
            if ae.get_membership_for(barman):
                is_ae_member = True
        return is_ae_member


class Refilling(models.Model):
    """
    Handle the refilling
    """

    counter = models.ForeignKey(
        Counter, related_name="refillings", blank=False, on_delete=models.CASCADE
    )
    amount = CurrencyField(_("amount"))
    operator = models.ForeignKey(
        User,
        related_name="refillings_as_operator",
        blank=False,
        on_delete=models.CASCADE,
    )
    customer = models.ForeignKey(
        Customer, related_name="refillings", blank=False, on_delete=models.CASCADE
    )
    date = models.DateTimeField(_("date"))
    payment_method = models.CharField(
        _("payment method"),
        max_length=255,
        choices=settings.SITH_COUNTER_PAYMENT_METHOD,
        default="CASH",
    )
    bank = models.CharField(
        _("bank"), max_length=255, choices=settings.SITH_COUNTER_BANK, default="OTHER"
    )
    is_validated = models.BooleanField(_("is validated"), default=False)

    class Meta:
        verbose_name = _("refilling")

    def __str__(self):
        return "Refilling: %.2f for %s" % (
            self.amount,
            self.customer.user.get_display_name(),
        )

    def is_owned_by(self, user):
        return user.is_owner(self.counter) and self.payment_method != "CARD"

    def delete(self, *args, **kwargs):
        self.customer.amount -= self.amount
        self.customer.save()
        super(Refilling, self).delete(*args, **kwargs)

    def save(self, *args, **kwargs):
        if not self.date:
            self.date = timezone.now()
        self.full_clean()
        if not self.is_validated:
            self.customer.amount += self.amount
            self.customer.save()
            self.is_validated = True
        if self.customer.user.preferences.notify_on_refill:
            Notification(
                user=self.customer.user,
                url=reverse(
                    "core:user_account_detail",
                    kwargs={
                        "user_id": self.customer.user.id,
                        "year": self.date.year,
                        "month": self.date.month,
                    },
                ),
                param=str(self.amount),
                type="REFILLING",
            ).save()
        super(Refilling, self).save(*args, **kwargs)


class Selling(models.Model):
    """
    Handle the sellings
    """

    label = models.CharField(_("label"), max_length=64)
    product = models.ForeignKey(
        Product,
        related_name="sellings",
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
    )
    counter = models.ForeignKey(
        Counter,
        related_name="sellings",
        null=True,
        blank=False,
        on_delete=models.SET_NULL,
    )
    club = models.ForeignKey(
        Club, related_name="sellings", null=True, blank=False, on_delete=models.SET_NULL
    )
    unit_price = CurrencyField(_("unit price"))
    quantity = models.IntegerField(_("quantity"))
    seller = models.ForeignKey(
        User,
        related_name="sellings_as_operator",
        null=True,
        blank=False,
        on_delete=models.SET_NULL,
    )
    customer = models.ForeignKey(
        Customer,
        related_name="buyings",
        null=True,
        blank=False,
        on_delete=models.SET_NULL,
    )
    date = models.DateTimeField(_("date"))
    payment_method = models.CharField(
        _("payment method"),
        max_length=255,
        choices=[("SITH_ACCOUNT", _("Sith account")), ("CARD", _("Credit card"))],
        default="SITH_ACCOUNT",
    )
    is_validated = models.BooleanField(_("is validated"), default=False)

    class Meta:
        verbose_name = _("selling")

    def __str__(self):
        return "Selling: %d x %s (%f) for %s" % (
            self.quantity,
            self.label,
            self.quantity * self.unit_price,
            self.customer.user.get_display_name(),
        )

    def is_owned_by(self, user):
        return user.is_owner(self.counter) and self.payment_method != "CARD"

    def can_be_viewed_by(self, user):
        if (
            not hasattr(self, "customer") or self.customer is None
        ):  # Customer can be set to Null
            return False
        return user == self.customer.user

    def delete(self, *args, **kwargs):
        if self.payment_method == "SITH_ACCOUNT":
            self.customer.amount += self.quantity * self.unit_price
            self.customer.save()
        super(Selling, self).delete(*args, **kwargs)

    def send_mail_customer(self):
        event = self.product.eticket.event_title or _("Unknown event")
        subject = _("Eticket bought for the event %(event)s") % {"event": event}
        message_html = _(
            "You bought an eticket for the event %(event)s.\nYou can download it directly from this link %(eticket)s.\nYou can also retrieve all your e-tickets on your account page %(url)s."
        ) % {
            "event": event,
            "url": "".join(
                (
                    '<a href="',
                    self.customer.get_full_url(),
                    '">',
                    self.customer.get_full_url(),
                    "</a>",
                )
            ),
            "eticket": "".join(
                (
                    '<a href="',
                    self.get_eticket_full_url(),
                    '">',
                    self.get_eticket_full_url(),
                    "</a>",
                )
            ),
        }
        message_txt = _(
            "You bought an eticket for the event %(event)s.\nYou can download it directly from this link %(eticket)s.\nYou can also retrieve all your e-tickets on your account page %(url)s."
        ) % {
            "event": event,
            "url": self.customer.get_full_url(),
            "eticket": self.get_eticket_full_url(),
        }
        self.customer.user.email_user(subject, message_txt, html_message=message_html)

    def save(self, allow_negative=False, *args, **kwargs):
        """
        allow_negative : Allow this selling to use more money than available for this user
        """
        if not self.date:
            self.date = timezone.now()
        self.full_clean()
        if not self.is_validated:
            self.customer.amount -= self.quantity * self.unit_price
            self.customer.save(allow_negative=allow_negative, is_selling=True)
            self.is_validated = True
        u = User.objects.filter(id=self.customer.user.id).first()
        if u.was_subscribed:
            if (
                self.product
                and self.product.id == settings.SITH_PRODUCT_SUBSCRIPTION_ONE_SEMESTER
            ):
                sub = Subscription(
                    member=u,
                    subscription_type="un-semestre",
                    payment_method="EBOUTIC",
                    location="EBOUTIC",
                )
                sub.subscription_start = Subscription.compute_start()
                sub.subscription_start = Subscription.compute_start(
                    duration=settings.SITH_SUBSCRIPTIONS[sub.subscription_type][
                        "duration"
                    ]
                )
                sub.subscription_end = Subscription.compute_end(
                    duration=settings.SITH_SUBSCRIPTIONS[sub.subscription_type][
                        "duration"
                    ],
                    start=sub.subscription_start,
                )
                sub.save()
            elif (
                self.product
                and self.product.id == settings.SITH_PRODUCT_SUBSCRIPTION_TWO_SEMESTERS
            ):
                u = User.objects.filter(id=self.customer.user.id).first()
                sub = Subscription(
                    member=u,
                    subscription_type="deux-semestres",
                    payment_method="EBOUTIC",
                    location="EBOUTIC",
                )
                sub.subscription_start = Subscription.compute_start()
                sub.subscription_start = Subscription.compute_start(
                    duration=settings.SITH_SUBSCRIPTIONS[sub.subscription_type][
                        "duration"
                    ]
                )
                sub.subscription_end = Subscription.compute_end(
                    duration=settings.SITH_SUBSCRIPTIONS[sub.subscription_type][
                        "duration"
                    ],
                    start=sub.subscription_start,
                )
                sub.save()
        if self.customer.user.preferences.notify_on_click:
            Notification(
                user=self.customer.user,
                url=reverse(
                    "core:user_account_detail",
                    kwargs={
                        "user_id": self.customer.user.id,
                        "year": self.date.year,
                        "month": self.date.month,
                    },
                ),
                param="%d x %s" % (self.quantity, self.label),
                type="SELLING",
            ).save()
        super(Selling, self).save(*args, **kwargs)
        try:
            # The product has no id until it's saved
            if self.product.eticket:
                self.send_mail_customer()
        except:
            pass

    def get_eticket_full_url(self):
        eticket_url = reverse("counter:eticket_pdf", kwargs={"selling_id": self.id})
        return "".join(["https://", settings.SITH_URL, eticket_url])


class Permanency(models.Model):
    """
    This class aims at storing a traceability of who was barman where and when
    """

    user = models.ForeignKey(
        User,
        related_name="permanencies",
        verbose_name=_("user"),
        on_delete=models.CASCADE,
    )
    counter = models.ForeignKey(
        Counter,
        related_name="permanencies",
        verbose_name=_("counter"),
        on_delete=models.CASCADE,
    )
    start = models.DateTimeField(_("start date"))
    end = models.DateTimeField(_("end date"), null=True, db_index=True)
    activity = models.DateTimeField(_("last activity date"), auto_now=True)

    class Meta:
        verbose_name = _("permanency")

    def __str__(self):
        return "%s in %s from %s (last activity: %s) to %s" % (
            self.user,
            self.counter,
            self.start.strftime("%Y-%m-%d %H:%M:%S"),
            self.activity.strftime("%Y-%m-%d %H:%M:%S"),
            self.end.strftime("%Y-%m-%d %H:%M:%S") if self.end else "",
        )


class CashRegisterSummary(models.Model):
    user = models.ForeignKey(
        User,
        related_name="cash_summaries",
        verbose_name=_("user"),
        on_delete=models.CASCADE,
    )
    counter = models.ForeignKey(
        Counter,
        related_name="cash_summaries",
        verbose_name=_("counter"),
        on_delete=models.CASCADE,
    )
    date = models.DateTimeField(_("date"))
    comment = models.TextField(_("comment"), null=True, blank=True)
    emptied = models.BooleanField(_("emptied"), default=False)

    class Meta:
        verbose_name = _("cash register summary")

    def __str__(self):
        return "At %s by %s - Total: %s €" % (self.counter, self.user, self.get_total())

    def __getattribute__(self, name):
        if name[:5] == "check":
            checks = self.items.filter(check=True).order_by("value").all()
        if name == "ten_cents":
            return self.items.filter(value=0.1, check=False).first()
        elif name == "twenty_cents":
            return self.items.filter(value=0.2, check=False).first()
        elif name == "fifty_cents":
            return self.items.filter(value=0.5, check=False).first()
        elif name == "one_euro":
            return self.items.filter(value=1, check=False).first()
        elif name == "two_euros":
            return self.items.filter(value=2, check=False).first()
        elif name == "five_euros":
            return self.items.filter(value=5, check=False).first()
        elif name == "ten_euros":
            return self.items.filter(value=10, check=False).first()
        elif name == "twenty_euros":
            return self.items.filter(value=20, check=False).first()
        elif name == "fifty_euros":
            return self.items.filter(value=50, check=False).first()
        elif name == "hundred_euros":
            return self.items.filter(value=100, check=False).first()
        elif name == "check_1":
            return checks[0] if 0 < len(checks) else None
        elif name == "check_2":
            return checks[1] if 1 < len(checks) else None
        elif name == "check_3":
            return checks[2] if 2 < len(checks) else None
        elif name == "check_4":
            return checks[3] if 3 < len(checks) else None
        elif name == "check_5":
            return checks[4] if 4 < len(checks) else None
        else:
            return object.__getattribute__(self, name)

    def is_owned_by(self, user):
        """
        Method to see if that object can be edited by the given user
        """
        if user.is_in_group(settings.SITH_GROUP_COUNTER_ADMIN_ID):
            return True
        return False

    def get_total(self):
        t = 0
        for it in self.items.all():
            t += it.quantity * it.value
        return t

    def save(self, *args, **kwargs):
        if not self.id:
            self.date = timezone.now()
        return super(CashRegisterSummary, self).save(*args, **kwargs)

    def get_absolute_url(self):
        return reverse("counter:cash_summary_list")


class CashRegisterSummaryItem(models.Model):
    cash_summary = models.ForeignKey(
        CashRegisterSummary,
        related_name="items",
        verbose_name=_("cash summary"),
        on_delete=models.CASCADE,
    )
    value = CurrencyField(_("value"))
    quantity = models.IntegerField(_("quantity"), default=0)
    check = models.BooleanField(_("check"), default=False)

    class Meta:
        verbose_name = _("cash register summary item")


class Eticket(models.Model):
    """
    Eticket can be linked to a product an allows PDF generation
    """

    product = models.OneToOneField(
        Product,
        related_name="eticket",
        verbose_name=_("product"),
        on_delete=models.CASCADE,
    )
    banner = models.ImageField(
        upload_to="etickets", null=True, blank=True, verbose_name=_("banner")
    )
    event_date = models.DateField(_("event date"), null=True, blank=True)
    event_title = models.CharField(
        _("event title"), max_length=64, null=True, blank=True
    )
    secret = models.CharField(_("secret"), max_length=64, unique=True)

    def __str__(self):
        return "%s" % (self.product.name)

    def get_absolute_url(self):
        return reverse("counter:eticket_list")

    def save(self, *args, **kwargs):
        if not self.id:
            self.secret = base64.b64encode(os.urandom(32))
        return super(Eticket, self).save(*args, **kwargs)

    def is_owned_by(self, user):
        """
        Method to see if that object can be edited by the given user
        """
        return user.is_in_group(settings.SITH_GROUP_COUNTER_ADMIN_ID)

    def get_hash(self, string):
        import hashlib
        import hmac

        return hmac.new(
            bytes(self.secret, "utf-8"), bytes(string, "utf-8"), hashlib.sha1
        ).hexdigest()


class StudentCard(models.Model):
    """
    Alternative way to connect a customer into a counter
    We are using Mifare DESFire EV1 specs since it's used for izly cards
    https://www.nxp.com/docs/en/application-note/AN10927.pdf
    UID is 7 byte long that means 14 hexa characters
    """

    UID_SIZE = 14

    @staticmethod
    def is_valid(uid):
        return (
            (uid.isupper() or uid.isnumeric())
            and len(uid) == StudentCard.UID_SIZE
            and not StudentCard.objects.filter(uid=uid).exists()
        )

    @staticmethod
    def can_create(customer, user):
        return user.pk == customer.user.pk or user.is_board_member or user.is_root

    def can_be_edited_by(self, obj):
        if isinstance(obj, User):
            return StudentCard.can_create(self.customer, obj)
        return False

    uid = models.CharField(
        _("uid"), max_length=14, unique=True, validators=[MinLengthValidator(4)]
    )
    customer = models.ForeignKey(
        Customer,
        related_name="student_cards",
        verbose_name=_("student cards"),
        null=False,
        blank=False,
        on_delete=models.CASCADE,
    )