poprawki i optymalizacje kodu

app.py

@@ -2379,20 +2379,27 @@ def admin_panel():
     total_expense = db.session.query(func.sum(Expense.amount)).scalar() or 0
     avg_list_expense = round(total_expense / list_count, 2) if list_count else 0
 
+    if db.engine.name == "sqlite":
+        timestamp_diff = func.strftime("%s", Item.purchased_at) - func.strftime("%s", Item.added_at)
+    elif db.engine.name in ("postgresql", "postgres"):
+        timestamp_diff = func.extract("epoch", Item.purchased_at) - func.extract("epoch", Item.added_at)
+    elif db.engine.name in ("mysql", "mariadb"):
+        timestamp_diff = func.timestampdiff(text("SECOND"), Item.added_at, Item.purchased_at)
+    else:
+        timestamp_diff = None
+
     time_to_purchase = (
-        db.session.query(
-            func.avg(
-                func.strftime("%s", Item.purchased_at)
-                - func.strftime("%s", Item.added_at)
-            )
-        )
+        db.session.query(func.avg(timestamp_diff))
         .filter(
             Item.purchased == True,
             Item.purchased_at.isnot(None),
             Item.added_at.isnot(None),
         )
         .scalar()
+        if timestamp_diff is not None
+        else None
     )
+
     avg_hours_to_purchase = round(time_to_purchase / 3600, 2) if time_to_purchase else 0
 
     first_list = db.session.query(func.min(ShoppingList.created_at)).scalar()