fix rates

lib/domain/entities/carton.dart

@@ -62,7 +62,7 @@ class Carton {
   double get actualWeight =>
       cargoTypes == null ? 0 : cargoTypes.fold(0, (p, e) => e.weight + p);
 
-  double getShipmentWeight(double volumetricRatio) {
+  int getShipmentWeight(double volumetricRatio) {
     if (length == null ||
         length <= 0 ||
         width == null ||
@@ -71,8 +71,8 @@ class Carton {
         height <= 0 ||
         volumetricRatio == null ||
         volumetricRatio <= 0) return 0;
-
-    return (length * width * height) / volumetricRatio;
+  
+    return ((length * width * height) / volumetricRatio).round();
   }
 
   /// getCargoTypeForCalWeight returns carton with shipment weight
@@ -95,25 +95,26 @@ class Carton {
   /// calAmount returns total amount
   double calAmount(Rate rate) {
     // get shipment weight
-    double volume = (length ?? 0) * (width ?? 0) * (height ?? 0);
-    double sw = volume / rate.volumetricRatio ?? 0;
+    int sw = getShipmentWeight(rate.volumetricRatio);
 
     // get actual weight
     double aw = cargoTypes.fold(0.0, (p, c) => p + c.weight);
     if (aw == 0 || sw == 0) return 0;
 
-    DiscountByWeight discountByWeight =
-        rate.getDiscountByWeight(sw > aw ? sw : aw);
+    double wd = sw - aw;
+    wd = wd - rate.diffDiscountWeight;
+    double wdAmount = wd > 0 ? wd * rate.diffWeightRate : 0;
+
+    DiscountByWeight discountByWeight = rate.getDiscountByWeight(aw);
 
     double total = 0;
     cargoTypes.forEach((e) {
-      double cargoWeight = aw > sw ? e.weight : e.weight / aw * sw;
       double r =
           e.rate - (discountByWeight != null ? discountByWeight.discount : 0);
-      double amount = cargoWeight * r;
+      double amount = e.weight * r;
       total += amount;
     });
-    return total;
+    return total + wdAmount;
   }
 
   List<ShipmentStatus> shipmentHistory;