Some optimizations to trade_offers to reduce loading times

trades/signals.py

@@ -1,8 +1,9 @@
 from django.core.exceptions import ValidationError
-from django.db.models.signals import m2m_changed, post_save, post_delete
+from django.db.models.signals import m2m_changed, post_save, post_delete, pre_save
 from django.dispatch import receiver
 from .models import TradeOffer
 from cards.models import Card
+from django.db.models import F
 from trades.models import TradeOfferHaveCard, TradeOfferWantCard, TradeAcceptance
 
 def check_trade_offer_rarity(instance):
@@ -31,46 +32,79 @@ ACTIVE_STATES = [
     TradeAcceptance.AcceptanceState.THANKED_BY_BOTH,
 ]
 
-def update_qty_for_trade_offer(trade_offer, card, side):
+def adjust_qty_for_trade_offer(trade_offer, card, side, delta):
+    """
+    Increment (or decrement) qty_accepted by delta for the given card on the specified side.
+    """
     if side == 'have':
-        count = TradeAcceptance.objects.filter(
-            trade_offer=trade_offer,
-            requested_card=card,
-            state__in=ACTIVE_STATES
-        ).count()
         TradeOfferHaveCard.objects.filter(
-            trade_offer=trade_offer, 
-            card=card
-        ).update(qty_accepted=count)
-
-        if count >= TradeOfferHaveCard.objects.filter(trade_offer=trade_offer, card=card).first().quantity:
-            trade_offer.is_closed = True
-            trade_offer.save(update_fields=["is_closed"])
-    elif side == 'want':
-        count = TradeAcceptance.objects.filter(
             trade_offer=trade_offer,
-            offered_card=card,
-            state__in=ACTIVE_STATES
-        ).count()
-        TradeOfferWantCard.objects.filter(
-            trade_offer=trade_offer, 
             card=card
-        ).update(qty_accepted=count)
-        
-        if count >= TradeOfferWantCard.objects.filter(trade_offer=trade_offer, card=card).first().quantity:
-            trade_offer.is_closed = True
-            trade_offer.save(update_fields=["is_closed"])
+        ).update(qty_accepted=F('qty_accepted') + delta)
+    elif side == 'want':
+        TradeOfferWantCard.objects.filter(
+            trade_offer=trade_offer,
+            card=card
+        ).update(qty_accepted=F('qty_accepted') + delta)
 
+def update_trade_offer_closed_status(trade_offer):
+    """
+    Check if both sides of the trade offer meet the quantity requirement.
+    Mark the trade_offer as closed if all cards have qty_accepted
+    greater than or equal to quantity; otherwise, mark it as open.
+    """
+    have_complete = not TradeOfferHaveCard.objects.filter(
+        trade_offer=trade_offer,
+        qty_accepted__lt=F('quantity')
+    ).exists()
+    want_complete = not TradeOfferWantCard.objects.filter(
+        trade_offer=trade_offer,
+        qty_accepted__lt=F('quantity')
+    ).exists()
+    closed = have_complete or want_complete
+    if trade_offer.is_closed != closed:
+        trade_offer.is_closed = closed
+        trade_offer.save(update_fields=["is_closed"])
 
-def update_all_qty(instance):
-    trade_offer = instance.trade_offer
-    update_qty_for_trade_offer(trade_offer, instance.requested_card, 'have')
-    update_qty_for_trade_offer(trade_offer, instance.offered_card, 'want')
+# Pre-save signal to capture the original state before any changes.
+@receiver(pre_save, sender=TradeAcceptance)
+def trade_acceptance_pre_save(sender, instance, **kwargs):
+    if instance.pk:
+        old_instance = TradeAcceptance.objects.get(pk=instance.pk)
+        instance._old_state = old_instance.state
 
+# Post-save signal to adjust qty_accepted incrementally.
 @receiver(post_save, sender=TradeAcceptance)
-def trade_acceptance_post_save(sender, instance, **kwargs):
-    update_all_qty(instance)
+def trade_acceptance_post_save(sender, instance, created, **kwargs):
+    delta = 0
+    if created:
+        # For a new acceptance, increment only if the state is active.
+        if instance.state in ACTIVE_STATES:
+            delta = 1
+    else:
+        old_state = getattr(instance, '_old_state', None)
+        if old_state is not None:
+            # Transition from active to non-active (e.g. a rejection)
+            if old_state in ACTIVE_STATES and instance.state not in ACTIVE_STATES:
+                delta = -1
+            # Transition from non-active to active
+            elif old_state not in ACTIVE_STATES and instance.state in ACTIVE_STATES:
+                delta = 1
 
+    if delta != 0:
+        trade_offer = instance.trade_offer
+        # Update the "have" side using the requested_card.
+        adjust_qty_for_trade_offer(trade_offer, instance.requested_card, side='have', delta=delta)
+        # Update the "want" side using the offered_card.
+        adjust_qty_for_trade_offer(trade_offer, instance.offered_card, side='want', delta=delta)
+        update_trade_offer_closed_status(trade_offer)
+
+# Post-delete signal to decrement qty_accepted if the deleted acceptance was active.
 @receiver(post_delete, sender=TradeAcceptance)
 def trade_acceptance_post_delete(sender, instance, **kwargs):
-    update_all_qty(instance) 
+    if instance.state in ACTIVE_STATES:
+        delta = -1
+        trade_offer = instance.trade_offer
+        adjust_qty_for_trade_offer(trade_offer, instance.requested_card, side='have', delta=delta)
+        adjust_qty_for_trade_offer(trade_offer, instance.offered_card, side='want', delta=delta)
+        update_trade_offer_closed_status(trade_offer)