enforce max amount on sith account

counter/fields.py

@@ -1,22 +1,67 @@
 from decimal import Decimal
 
 from django.conf import settings
+from django.core import checks
+from django.core.validators import MaxValueValidator, MinValueValidator
 from django.db import models
+from django.utils.functional import cached_property
 
 
 class CurrencyField(models.DecimalField):
     """Custom database field used for currency."""
 
-    def __init__(self, *args, **kwargs):
-        kwargs["max_digits"] = 12
-        kwargs["decimal_places"] = 2
-        super().__init__(*args, **kwargs)
+    def __init__(
+        self, verbose_name=None, name=None, min_value=None, max_value=None, **kwargs
+    ):
+        kwargs.update({"max_digits": 12, "decimal_places": 2})
+        self.min_value = min_value
+        self.max_value = max_value
+        super().__init__(verbose_name, name, **kwargs)
 
     def to_python(self, value):
         if value is None:
             return None
         return super().to_python(value).quantize(Decimal("0.01"))
 
+    @cached_property
+    def validators(self):
+        res = []
+        if self.max_value:
+            res.append(MaxValueValidator(self.max_value))
+        if self.min_value:
+            res.append(MinValueValidator(self.min_value))
+        return [*super().validators, *res]
+
+    def check(self, **kwargs):
+        errors = super().check(**kwargs)
+        for name, val in ("min_value", self.min_value), ("max_value", self.max_value):
+            if not val:
+                continue
+            try:
+                float(val)
+            except ValueError:
+                errors.append(
+                    checks.Error(
+                        f"CurrencyField.{name} must be a valid float",
+                        obj=self,
+                        id="sith.E001",
+                    )
+                )
+        return errors
+
+    def formfield(self, **kwargs):
+        return super().formfield(
+            **{"min_value": self.min_value, "max_value": self.max_value, **kwargs}
+        )
+
+    def deconstruct(self):
+        name, path, args, kwargs = super().deconstruct()
+        if self.min_value is not None:
+            kwargs["min_value"] = self.min_value
+        if self.max_value is not None:
+            kwargs["max_value"] = self.max_value
+        return name, path, args, kwargs
+
 
 if settings.TESTING:
     from model_bakery import baker

counter/migrations/0042_alter_customer_amount_alter_refilling_amount.py

@@ -0,0 +1,30 @@
+# Generated by Django 5.2.15 on 2026-06-07 12:08
+
+from django.db import migrations
+
+import counter.fields
+
+
+class Migration(migrations.Migration):
+    dependencies = [("counter", "0041_alter_billinginfo_country_and_more")]
+
+    operations = [
+        migrations.AlterField(
+            model_name="customer",
+            name="amount",
+            field=counter.fields.CurrencyField(
+                decimal_places=2,
+                default=0,
+                max_digits=12,
+                max_value=250,
+                verbose_name="amount",
+            ),
+        ),
+        migrations.AlterField(
+            model_name="refilling",
+            name="amount",
+            field=counter.fields.CurrencyField(
+                decimal_places=2, max_digits=12, min_value=0.01, verbose_name="amount"
+            ),
+        ),
+    ]

counter/models.py

@@ -28,7 +28,7 @@ from dict2xml import dict2xml
 from django.conf import settings
 from django.core.validators import MinLengthValidator
 from django.db import models
-from django.db.models import Exists, F, OuterRef, Q, QuerySet, Subquery, Sum, Value
+from django.db.models import Exists, F, Max, OuterRef, Q, QuerySet, Subquery, Sum, Value
 from django.db.models.functions import Coalesce, Concat, Length
 from django.forms import ValidationError
 from django.urls import reverse
@@ -99,7 +99,9 @@ class Customer(models.Model):
 
     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"), default=0)
+    amount = CurrencyField(
+        _("amount"), max_value=settings.SITH_ACCOUNT_MAX_MONEY, default=0
+    )
 
     objects = CustomerQuerySet.as_manager()
 
@@ -156,13 +158,15 @@ class Customer(models.Model):
             unique_fields=["customer", "returnable"],
         )
 
-    @property
+    @cached_property
     def can_buy(self) -> bool:
         """Check if whether this customer has the right to purchase any item."""
-        subscription = self.user.subscriptions.order_by("subscription_end").last()
-        if subscription is None:
+        subscription_end = self.user.subscriptions.aggregate(
+            res=Max("subscription_end")
+        ).get("res")
+        if subscription_end is None:
             return False
-        return (date.today() - subscription.subscription_end) < timedelta(days=90)
+        return (date.today() - subscription_end) < timedelta(days=90)
 
     @classmethod
     def get_or_create(cls, user: User) -> tuple[Customer, bool]:
@@ -823,7 +827,7 @@ class Refilling(models.Model):
     counter = models.ForeignKey(
         Counter, related_name="refillings", blank=False, on_delete=models.CASCADE
     )
-    amount = CurrencyField(_("amount"))
+    amount = CurrencyField(_("amount"), min_value=0.01)
     operator = models.ForeignKey(
         User,
         related_name="refillings_as_operator",

sith/settings.py

@@ -503,6 +503,8 @@ SITH_ACCOUNT_INACTIVITY_DELTA = relativedelta(years=2)
 SITH_ACCOUNT_DUMP_DELTA = timedelta(days=30)
 """timedelta between the warning mail and the actual account dump"""
 
+SITH_ACCOUNT_MAX_MONEY = 250  # €
+
 # Defines which product type is the refilling type,
 # and thus increases the account amount
 SITH_COUNTER_PRODUCTTYPE_REFILLING = env.int(