Update commodity and transaction details and list

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

trading/models.py

@@ -1,11 +1,12 @@
-from datetime import date
+from datetime import datetime
 from typing import Mapping, Optional, Sequence
 from django.conf import settings
 from django.contrib.auth.models import AbstractBaseUser, PermissionsMixin
 from django.db import models
-from django.db.models import Q
+from django.db.models import Q, Sum
 from django.db.models.signals import post_save, pre_save
 from django.dispatch import receiver
+from django.urls import reverse
 from django.utils.translation import gettext_lazy as _
 from frozendict import frozendict
 from guardian.shortcuts import assign_perm
@@ -75,8 +76,6 @@ class User(PermissionsMixin, AbstractBaseUser):
         return self.balances().get(commodity, 0)
 
     def balances(self) -> Mapping["Commodity", int]:
-        from django.db.models import Sum
-
         # We are the source, receiving from the destination
         credits_sent = {
             row["dest_sends"]: row["dest_amount__sum"]
@@ -172,24 +171,82 @@ class Commodity(models.Model):
 
     id = HashidAutoField(primary_key=True)
     name = models.CharField(
-        blank=False, unique=True, max_length=100, verbose_name=_("commodity name")
+        blank=False,
+        unique=True,
+        editable=False,
+        max_length=100,
+        verbose_name=_("commodity name"),
+    )
+    symbol = models.CharField(
+        blank=False, unique=True, editable=False, max_length=6, verbose_name=_("symbol")
     )
     in_circulation = models.PositiveIntegerField()
     created_by = models.ForeignKey(User, null=True, on_delete=models.SET_NULL)
-    symbol = models.CharField(blank=True, max_length=6, verbose_name=_("symbol"))
 
     class Meta:
         verbose_name = _("commodity")
         verbose_name_plural = _("commodities")
 
-    def get_absolute_url(self):
-        return "/c/detail/%s" % self.pk
+    def trading_volume(self, since: Optional[datetime] = None) -> int:
+        """
+        Gets the amount of this commodity traded since the given cutoff, inclusive.
 
-    def html_symbol(self) -> str:
-        if self.symbol:
-            return f"<span>{self.symbol}</span>"
-        else:
-            return f"<span>units of {self.name}</span>"
+        If no cutoff is given, then it returns the volume of all transactions.
+        """
+        source_filt = {"source_sends": self, "status": TxRequest.ACCEPTED}
+        dest_filt = {"dest_sends": self, "status": TxRequest.ACCEPTED}
+        if since is not None:
+            source_filt["update_time__gte"] = since
+            dest_filt["update_time__gte"] = since
+        source_query = (
+            TxRequest.objects.filter(**source_filt)
+            .annotate(Sum("source_amount"))
+            .values("source_amount__sum")
+            .first()
+        )
+        dest_query = (
+            TxRequest.objects.filter(**dest_filt)
+            .annotate(Sum("dest_amount"))
+            .values("dest_amount__sum")
+            .first()
+        )
+        source_amount = source_query["source_amount__sum"] if source_query else 0
+        dest_amount = dest_query["dest_amount__sum"] if dest_query else 0
+        return source_amount + dest_amount
+
+    @property
+    def market_spread(self) -> int:
+        count = 0
+        for user in User.objects.all():
+            if not user.is_active:
+                continue
+            if user.balance_of(self) > 0:
+                count += 1
+        return count
+
+    @property
+    def market_spread_ratio(self) -> float:
+        user_count = len(User.objects.all())
+        if user_count == 0:
+            return 0.0
+        return self.market_spread / user_count
+
+    @property
+    def amount_pending(self) -> int:
+        """
+        Gets the amount of this commodity that is currently being held in pending transactions.
+        """
+        pending = (
+            TxRequest.objects.filter(source_sends=self, status=TxRequest.OPEN)
+            .annotate(Sum("source_amount"))
+            .values("source_amount__sum")
+            .first()
+        )
+        return pending["source_amount__sum"] if pending else 0
+
+    @property
+    def url(self) -> str:
+        return f'<a href="{reverse("trading:commodity_detail", args=[self.id])}">{self.symbol}</a>'
 
 
 class MaxCommodityError(Exception):
@@ -230,6 +287,9 @@ class TxRequest(models.Model):
     #    related_name="revised_request",
     # )
 
+    create_time = models.DateTimeField(auto_now_add=True, editable=False)
+    update_time = models.DateTimeField(auto_now=True)
+
     source = models.ForeignKey(
         User, on_delete=models.CASCADE, related_name="tx_sent", editable=False,
     )