feat(pally): support customer-pays-fees scenario with BalanceAmount validation

api/routes/pally.py

@@ -51,8 +51,8 @@ async def pally_callback(
     
     logger.info(
         "Pally webhook received - InvId: %s, OutSum: %s, Commission: %s, TrsId: %s, Status: %s, "
-        "CurrencyIn: %s, custom: %s, SignatureValue: %s",
-        InvId, OutSum, Commission, TrsId, Status, CurrencyIn, custom, SignatureValue
+        "CurrencyIn: %s, custom: %s, BalanceAmount: %s, SignatureValue: %s",
+        InvId, OutSum, Commission, TrsId, Status, CurrencyIn, custom, BalanceAmount, SignatureValue
     )
     
     # Enhanced logging for failed payments
@@ -105,15 +105,43 @@ async def pally_callback(
         return "OK"
 
     try:
-        amount = int(float(OutSum))
-
-        # Validate payment amount
-        if bill.amount != amount:
-            logger.error(
-                "Amount mismatch for bill %s (TrsId: %s) - Expected: %s, Received: %s",
-                bill.id, TrsId, bill.amount, amount
+        # Handle fee scenarios: use BalanceAmount if available (net amount after fees),
+        # otherwise use OutSum (gross amount paid by customer)
+        if BalanceAmount is not None:
+            # Customer pays fees - BalanceAmount is the net amount credited to merchant
+            credited_amount = int(float(BalanceAmount))
+            gross_amount = int(float(OutSum))
+            
+            logger.info(
+                "Customer-pays-fees payment: bill_id=%s, expected=%s, gross_paid=%s, net_credited=%s",
+                bill.id, bill.amount, gross_amount, credited_amount
             )
-            return "OK"
+            
+            # Validate that the net credited amount matches our bill amount
+            if bill.amount != credited_amount:
+                logger.error(
+                    "Net amount mismatch for bill %s (TrsId: %s) - Expected: %s, Net credited: %s, Gross paid: %s",
+                    bill.id, TrsId, bill.amount, credited_amount, gross_amount
+                )
+                return "OK"
+                
+            amount = credited_amount  # Credit the net amount (without fees)
+            
+        else:
+            # Standard payment - OutSum should match bill amount exactly
+            amount = int(float(OutSum))
+            
+            logger.info(
+                "Standard payment: bill_id=%s, expected=%s, received=%s",
+                bill.id, bill.amount, amount
+            )
+            
+            if bill.amount != amount:
+                logger.error(
+                    "Amount mismatch for bill %s (TrsId: %s) - Expected: %s, Received: %s",
+                    bill.id, TrsId, bill.amount, amount
+                )
+                return "OK"
 
         logger.info("Processing payment: bill_id=%s, user_id=%s, amount=%s", 
                    bill.id, bill.creator_id, amount)