new: first commit !minor

order/models.py

@@ -0,0 +1,50 @@
+from datetime import datetime
+from django.contrib.auth.models import User
+from django.db import models
+
+
+class BaseModel(models.Model):
+    class Meta:
+        abstract = True
+
+    class ReadonlyMeta:
+        readonly = []
+
+
+class SaleOrder(BaseModel):
+    class ReadonlyMeta:
+        readonly = ["sold_to", "sold_at", "total"]
+
+    name = models.CharField(max_length=200, unique=True)
+    sold_to = models.ForeignKey(User, on_delete=models.DO_NOTHING, default=None, null=True)
+    total = models.FloatField(max_length=200, default=0.0)
+    sold_at = models.DateTimeField(max_length=200, null=True, default=None)
+
+    @property
+    def amount_total(self) -> float:
+        return sum(
+            map(
+                lambda x: x.product.unit_price * x.quantity,
+                self.saleorderline_set.all(),
+            )
+        )
+
+    def sell(self, user: User):
+        if not self.sold_at:
+            self.sold_at = datetime.now()
+            self.sold_to = user
+            self.total = self.amount_total
+            self.save()
+        return self
+
+
+class Product(models.Model):
+    name = models.CharField(max_length=200)
+    unit_price = models.IntegerField(default=0)
+
+
+class SaleOrderLine(models.Model):
+    name = models.CharField(max_length=200)
+    product = models.ForeignKey(Product, on_delete=models.DO_NOTHING, null=True)
+    order = models.ForeignKey(SaleOrder, on_delete=models.CASCADE, null=True)
+    quantity = models.IntegerField(default=1)