Doing a sort of catch-up on previous work after returning 2 months later

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

trading/models.py

@@ -7,6 +7,7 @@ from django.db.models.signals import post_save, pre_save
 from django.dispatch import receiver
 from django.utils.translation import gettext_lazy as _
 from frozendict import frozendict
+from guardian.shortcuts import assign_perm
 from hashid_field import HashidAutoField
 from trading.managers import UserManager
 
@@ -89,9 +90,9 @@ class User(PermissionsMixin, AbstractBaseUser):
         }
         tx_requests = {
             row["source_sends"]: row["source_amount__sum"]
-            for row in self.transaction_requests_sent.filter(
-                status=TxRequest.OPEN
-            ).values("source_sends").annotate(Sum("source_amount"))
+            for row in self.transaction_requests_sent.filter(status=TxRequest.OPEN)
+            .values("source_sends")
+            .annotate(Sum("source_amount"))
         }
         keys = (
             set(ipos.keys())
@@ -244,21 +245,27 @@ class TxRequest(models.Model):
     # )
 
     source = models.ForeignKey(
-        User, on_delete=models.CASCADE, related_name="transaction_requests_sent",
+        User,
+        on_delete=models.CASCADE,
+        related_name="transaction_requests_sent",
+        editable=False,
     )
     dest = models.ForeignKey(
-        User, on_delete=models.CASCADE, related_name="transaction_requests_received",
+        User,
+        on_delete=models.CASCADE,
+        related_name="transaction_requests_received",
+        editable=False,
     )
 
     source_sends = models.ForeignKey(
-        Commodity, on_delete=models.CASCADE, related_name="+", null=True,
+        Commodity, on_delete=models.CASCADE, related_name="+", null=True, editable=False,
     )
     dest_sends = models.ForeignKey(
-        Commodity, on_delete=models.CASCADE, related_name="+", null=True,
+        Commodity, on_delete=models.CASCADE, related_name="+", null=True, editable=False,
     )
 
-    source_amount = models.PositiveIntegerField()
-    dest_amount = models.PositiveIntegerField()
+    source_amount = models.PositiveIntegerField(editable=False)
+    dest_amount = models.PositiveIntegerField(editable=False)
 
     @staticmethod
     def open(
@@ -275,7 +282,9 @@ class TxRequest(models.Model):
         # Check balance
         source_balance = source.balance_of(source_sends)
         if source_balance < source_amount:
-            raise BalanceError(source_balance, source, dest, source_amount, source_sends)
+            raise BalanceError(
+                source_balance, source, dest, source_amount, source_sends
+            )
         req = TxRequest.objects.create(
             status=TxRequest.OPEN,
             source=source,
@@ -288,20 +297,28 @@ class TxRequest(models.Model):
         req.save()
         return req
 
+    def can_accept(self) -> bool:
+        """
+        Gets whether this request can be accepted.
+        """
+        dest_balance = self.dest.balance_of(self.dest_sends)
+        return self.status == TxRequest.OPEN and dest_balance >= self.dest_amount
+
+
     def accept(self):
         """
         Accepts an open transaction request.
         """
         assert self.status == TxRequest.OPEN
 
-        # ensure destination balance before continuing
-        dest_balance = self.dest.balance_of(self.dest_sends)
-        if dest_balance < self.dest_amount:
+        # Ensure destination balance before continuing
+        if not self.can_accept():
+            dest_balance = self.dest.balance_of(self.dest_sends)
             raise BalanceError(
                 dest_balance, self.dest, self.source, self.dest_amount, self.dest_sends
             )
 
-        # update status
+        # Update status
         self.status = TxRequest.ACCEPTED
 
         # Create source transaction
@@ -336,6 +353,8 @@ class TxRequest(models.Model):
         self.save()
 
 
+
+
 class BalanceError(Exception):
     def __init__(
         self, balance: int, source: User, dest: User, amount: int, commodity: Commodity
@@ -364,3 +383,11 @@ def _tx_pre_save(sender, instance, *args, **kwargs):
                 instance.amount,
                 instance.commodity,
             )
+
+
+@receiver(post_save, sender=TxRequest)
+def __tx_post_save(sender, instance, created, **kwargs):
+    if not created:
+        return
+    assign_perm("view_txrequest", instance.source, instance)
+    assign_perm("view_txrequest", instance.dest, instance)