Move test directory, add TxRequest

* ./tests is moved to ./trading/tests
* Remove trading/tests.py
* Add TxRequest model
* Add tests for TxRequests

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

trading/models.py

@@ -87,12 +87,26 @@ class User(PermissionsMixin, AbstractBaseUser):
             row["pk"]: row["in_circulation"]
             for row in self.commodity_set.values("pk", "in_circulation")
         }
-        keys = set(ipos.keys()) | set(credits.keys()) | set(debits.keys())
+        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"))
+        }
+        keys = (
+            set(ipos.keys())
+            | set(credits.keys())
+            | set(debits.keys())
+            | set(tx_requests.keys())
+        )
         return frozendict(
             [
                 (
                     Commodity.objects.get(pk=pk),
-                    credits.get(pk, 0) + ipos.get(pk, 0) - debits.get(pk, 0),
+                    credits.get(pk, 0)
+                    + ipos.get(pk, 0)
+                    - debits.get(pk, 0)
+                    - tx_requests.get(pk, 0),
                 )
                 for pk in keys
             ]
@@ -142,9 +156,7 @@ class Commodity(models.Model):
     )
     in_circulation = models.PositiveIntegerField()
     created_by = models.ForeignKey(User, null=True, on_delete=models.SET_NULL)
-    symbol = models.CharField(
-        blank=True, unique=True, max_length=6, verbose_name=_("symbol")
-    )
+    symbol = models.CharField(blank=True, max_length=6, verbose_name=_("symbol"))
 
     class Meta:
         verbose_name = _("commodity")
@@ -157,7 +169,7 @@ class Commodity(models.Model):
         if self.symbol:
             return f"<span>{self.symbol}</span>"
         else:
-            return f"<span>units of {self.name}"
+            return f"<span>units of {self.name}</span>"
 
 
 class MaxCommodityError(Exception):
@@ -191,51 +203,51 @@ class Tx(models.Model):
     )
     amount = models.PositiveIntegerField(verbose_name=_("amount"), editable=False)
     commodity = models.ForeignKey(Commodity, on_delete=models.PROTECT, editable=False)
+    request = models.ForeignKey(
+        "TxRequest", null=True, default=None, on_delete=models.SET_NULL
+    )
 
     class Meta:
         verbose_name = _("transaction")
         verbose_name_plural = _("transactions")
 
 
-class TxRequests(models.Model):
+class TxRequest(models.Model):
     """
     A transaction request between two users.
     """
 
-    WAITING = "WAIT"
+    OPEN = "OPEN"
     DECLINED = "DECL"
-    REVISED = "REV"
+    # REVISED = "REV"
+    ACCEPTED = "ACC"
 
     STATUS_CHOICES = [
-        (WAITING, "Waiting"),
+        (OPEN, "Open"),
         (DECLINED, "Declined"),
-        (REVISED, "Revised"),
+        # (REVISED, "Revised"),
+        (ACCEPTED, "Accepted"),
     ]
 
     status = models.CharField(
         max_length=max([len(c) for c in STATUS_CHOICES]),
         choices=STATUS_CHOICES,
-        default=WAITING,
-    )
-    previous_request = models.OneToOneField(
-        "TxRequests",
-        null=True,
-        default=None,
-        on_delete=models.SET_NULL,
-        related_name="revised_request",
+        default=OPEN,
     )
 
+    # previous_request = models.OneToOneField(
+    #    "TxRequest",
+    #    null=True,
+    #    default=None,
+    #    on_delete=models.SET_NULL,
+    #    related_name="revised_request",
+    # )
+
     source = models.ForeignKey(
-        User,
-        on_delete=models.CASCADE,
-        null=True,
-        related_name="transaction_requests_sent",
+        User, on_delete=models.CASCADE, related_name="transaction_requests_sent",
     )
     dest = models.ForeignKey(
-        User,
-        on_delete=models.CASCADE,
-        null=True,
-        related_name="transaction_requests_received",
+        User, on_delete=models.CASCADE, related_name="transaction_requests_received",
     )
 
     source_sends = models.ForeignKey(
@@ -248,6 +260,81 @@ class TxRequests(models.Model):
     source_amount = models.PositiveIntegerField()
     dest_amount = models.PositiveIntegerField()
 
+    @staticmethod
+    def open(
+        source: User,
+        dest: User,
+        source_sends: Commodity,
+        dest_sends: Commodity,
+        source_amount: int,
+        dest_amount: int,
+    ) -> "TxRequest":
+        """
+        Opens a new transaction request.
+        """
+        # Check balance
+        source_balance = source.balance_of(source_sends)
+        if source_balance < source_amount:
+            raise BalanceError(source_balance, source, dest, source_amount, source_sends)
+        req = TxRequest.objects.create(
+            status=TxRequest.OPEN,
+            source=source,
+            dest=dest,
+            source_sends=source_sends,
+            dest_sends=dest_sends,
+            source_amount=source_amount,
+            dest_amount=dest_amount,
+        )
+        req.save()
+        return req
+
+    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:
+            raise BalanceError(
+                dest_balance, self.dest, self.source, self.dest_amount, self.dest_sends
+            )
+
+        # update status
+        self.status = TxRequest.ACCEPTED
+
+        # Create source transaction
+        source_tx = Tx.objects.create(
+            source=self.source,
+            dest=self.dest,
+            amount=self.source_amount,
+            commodity=self.source_sends,
+            request=self,
+        )
+
+        # Create dest transaction
+        dest_tx = Tx.objects.create(
+            source=self.dest,
+            dest=self.source,
+            amount=self.dest_amount,
+            commodity=self.dest_sends,
+            request=self,
+        )
+
+        # Save everything
+        source_tx.save()
+        dest_tx.save()
+        self.save()
+
+    def decline(self):
+        """
+        Declines an open transaction request.
+        """
+        assert self.status == TxRequest.OPEN
+        self.status = TxRequest.DECLINED
+        self.save()
+
 
 class BalanceError(Exception):
     def __init__(