Improved precision converter (#74)

* Improved precision converter

* Update trait doc

Author: vovac12

pallets/parachain-app/src/lib.rs

@@ -281,8 +281,9 @@ pub mod pallet {
 
             let precision = SidechainPrecision::<T>::get(network_id, &asset_id)
                 .ok_or(Error::<T>::UnknownPrecision)?;
-            let amount = T::BalancePrecisionConverter::from_sidechain(&asset_id, precision, amount)
-                .ok_or(Error::<T>::WrongAmount)?;
+            let (amount, _) =
+                T::BalancePrecisionConverter::from_sidechain(&asset_id, precision, amount)
+                    .ok_or(Error::<T>::WrongAmount)?;
             ensure!(amount > Zero::zero(), Error::<T>::WrongAmount);
 
             T::BridgeAssetLocker::unlock_asset(
@@ -366,7 +367,7 @@ pub mod pallet {
 
             let sidechain_precision = T::AssetRegistry::get_raw_info(asset_id.clone()).precision;
 
-            let minimal_xcm_amount = T::BalancePrecisionConverter::to_sidechain(
+            let (_, minimal_xcm_amount) = T::BalancePrecisionConverter::to_sidechain(
                 &asset_id,
                 sidechain_precision,
                 minimal_xcm_amount,
@@ -403,7 +404,7 @@ pub mod pallet {
             ensure_root(origin)?;
 
             let asset_id = T::AssetRegistry::register_asset(network_id.into(), name, symbol)?;
-            let minimal_xcm_amount =
+            let (_, minimal_xcm_amount) =
                 T::BalancePrecisionConverter::to_sidechain(&asset_id, decimals, minimal_xcm_amount)
                     .ok_or(Error::<T>::WrongAmount)?;
 
@@ -500,7 +501,7 @@ pub mod pallet {
                 fail!(Error::<T>::UnknownPrecision);
             };
 
-            let minimal_xcm_amount = T::BalancePrecisionConverter::to_sidechain(
+            let (_, minimal_xcm_amount) = T::BalancePrecisionConverter::to_sidechain(
                 &asset_id,
                 sidechain_precision,
                 minimal_xcm_amount,
@@ -588,7 +589,7 @@ pub mod pallet {
             let precision = SidechainPrecision::<T>::get(network_id, &asset_id)
                 .ok_or(Error::<T>::UnknownPrecision)?;
 
-            let sidechain_amount =
+            let (amount, sidechain_amount) =
                 T::BalancePrecisionConverter::to_sidechain(&asset_id, precision, amount.clone())
                     .ok_or(Error::<T>::WrongAmount)?;
 

pallets/parachain-app/src/mock.rs

@@ -298,23 +298,23 @@ impl BalancePrecisionConverter<AssetId, Balance, Balance> for BalancePrecisionCo
         asset_id: &AssetId,
         _sidechain_precision: u8,
         amount: Balance,
-    ) -> Option<Balance> {
+    ) -> Option<(Balance, Balance)> {
         if matches!(asset_id, AssetId::Custom(_)) {
-            Some(amount)
+            Some((amount, amount))
         } else {
-            Some(amount * 10)
+            Some((amount, amount * 10))
         }
     }
 
     fn from_sidechain(
         asset_id: &AssetId,
         _sidechain_precision: u8,
         amount: Balance,
-    ) -> Option<Balance> {
+    ) -> Option<(Balance, Balance)> {
         if matches!(asset_id, AssetId::Custom(_)) {
-            Some(amount)
+            Some((amount, amount))
         } else {
-            Some(amount / 10)
+            Some((amount / 10, amount))
         }
     }
 }

pallets/parachain-app/src/tests.rs

@@ -72,7 +72,7 @@ fn it_works_mint() {
             recipient.clone(),
             amount
         ));
-        let sidechain_amount =
+        let (_, sidechain_amount) =
             BalancePrecisionConverterImpl::from_sidechain(&AssetId::Custom(1), 0, amount).unwrap();
         assert_eq!(
             Currencies::total_balance(asset_id, &recipient),

pallets/types/src/traits.rs

@@ -358,35 +358,52 @@ impl AuxiliaryDigestHandler for () {
     fn add_item(_item: AuxiliaryDigestItem) {}
 }
 
+/// Converter trait for Balance precision in different networks.
 pub trait BalancePrecisionConverter<AssetId, Balance, SidechainBalance> {
+    /// Convert thischain balance to sidechain balance.
+    ///
+    /// **Returns**
+    /// * `Balance` - rounded thischain balance
+    /// * `SidechainBalance` - converted sidechain balance
+    ///
+    /// Or
+    /// * `None` - if thischain balance can't be converted to sidechain balance
     fn to_sidechain(
         asset_id: &AssetId,
         sidechain_precision: u8,
         amount: Balance,
-    ) -> Option<SidechainBalance>;
-
+    ) -> Option<(Balance, SidechainBalance)>;
+
+    /// Convert sidechain balance to thischain balance.
+    ///
+    /// **Returns**
+    /// * `Balance` - rounded thischain balance
+    /// * `SidechainBalance` - converted sidechain balance
+    ///
+    /// Or
+    /// * `None` - if sidechain balance can't be converted to thischain balance
     fn from_sidechain(
         asset_id: &AssetId,
         sidechain_precision: u8,
         amount: SidechainBalance,
-    ) -> Option<Balance>;
+    ) -> Option<(Balance, SidechainBalance)>;
 }
 
-impl<AssetId, Balance> BalancePrecisionConverter<AssetId, Balance, Balance> for () {
+impl<AssetId, Balance: Clone> BalancePrecisionConverter<AssetId, Balance, Balance> for () {
     fn to_sidechain(
         _asset_id: &AssetId,
         _sidechain_precision: u8,
         amount: Balance,
-    ) -> Option<Balance> {
-        Some(amount)
+    ) -> Option<(Balance, Balance)> {
+        Some((amount.clone(), amount))
     }
 
     fn from_sidechain(
         _asset_id: &AssetId,
         _sidechain_precision: u8,
         amount: Balance,
-    ) -> Option<Balance> {
-        Some(amount)
+    ) -> Option<(Balance, Balance)> {
+        Some((amount.clone(), amount))
     }
 }