fix duplicated fee issue

modules/homa-lite/src/lib.rs

@@ -420,17 +420,26 @@ pub mod module {
 
 					Self::deposit_event(Event::<T>::RedeemRequestCancelled(who, request_amount));
 				}
-			} else {
-				// Redeem amount must be above a certain limit.
-				ensure!(
-					Self::liquid_amount_is_above_minimum_threshold(liquid_amount),
-					Error::<T>::AmountBelowMinimumThreshold
-				);
+				return Ok(());
+			}
+
+			// Redeem amount must be above a certain limit.
+			ensure!(
+				Self::liquid_amount_is_above_minimum_threshold(liquid_amount),
+				Error::<T>::AmountBelowMinimumThreshold
+			);
+
+			RedeemRequests::<T>::try_mutate(&who, |request| -> DispatchResult {
+				let old_amount = request.take().map(|(amount, _)| amount).unwrap_or_default();
 
-				// Withdraw fee is burned.
-				let base_withdraw_fee = T::BaseWithdrawFee::get().mul(liquid_amount);
-				let slash_amount = T::Currency::slash(T::LiquidCurrencyId::get(), &who, base_withdraw_fee);
-				ensure!(slash_amount.is_zero(), Error::<T>::InsufficientLiquidBalance);
+				let diff_amount = liquid_amount.saturating_sub(old_amount);
+
+				let base_withdraw_fee = T::BaseWithdrawFee::get().mul(diff_amount);
+				if !base_withdraw_fee.is_zero() {
+					// Burn withdraw fee for increased amount
+					let slash_amount = T::Currency::slash(T::LiquidCurrencyId::get(), &who, base_withdraw_fee);
+					ensure!(slash_amount.is_zero(), Error::<T>::InsufficientLiquidBalance);
+				}
 
 				// Deduct BaseWithdrawFee from the liquid amount.
 				let liquid_amount = liquid_amount.saturating_sub(base_withdraw_fee);
@@ -492,12 +501,17 @@ pub mod module {
 					}?;
 
 					// Insert/replace the new redeem request into storage.
-					RedeemRequests::<T>::insert(&who, (liquid_remaining, additional_fee));
+					*request = Some((liquid_remaining, additional_fee));
 
-					Self::deposit_event(Event::<T>::RedeemRequested(who, liquid_remaining, additional_fee));
+					Self::deposit_event(Event::<T>::RedeemRequested(
+						who.clone(),
+						liquid_remaining,
+						additional_fee,
+					));
 				}
-			}
-			Ok(())
+
+				Ok(())
+			})
 		}
 
 		/// Request staking currencies to be unbonded from the RelayChain.
@@ -850,7 +864,6 @@ pub mod module {
 
 		fn liquid_amount_is_above_minimum_threshold(liquid_amount: Balance) -> bool {
 			liquid_amount > T::MinimumRedeemThreshold::get()
-				&& Self::convert_liquid_to_staking(liquid_amount).unwrap_or_default() > T::XcmUnbondFee::get()
 		}
 
 		/// Construct a XCM message

modules/homa-lite/src/tests.rs

@@ -894,3 +894,55 @@ fn process_scheduled_unbond_with_multiple_requests() {
 		assert_eq!(Currencies::reserved_balance(LKSM, &CHARLIE), 99899999999996);
 	});
 }
+
+#[test]
+fn not_overcharge_redeem_fee() {
+	ExtBuilder::empty().build().execute_with(|| {
+		assert_ok!(Currencies::update_balance(
+			Origin::root(),
+			ALICE,
+			LKSM,
+			dollar(100) as i128
+		));
+
+		assert_ok!(HomaLite::set_total_staking_currency(Origin::root(), dollar(10)));
+
+		assert_ok!(HomaLite::request_redeem(
+			Origin::signed(ALICE),
+			dollar(50),
+			Permill::zero()
+		));
+
+		let fee = dollar(50) / 1000;
+
+		assert_eq!(Currencies::free_balance(LKSM, &ALICE), dollar(50));
+		assert_eq!(Currencies::reserved_balance(LKSM, &ALICE), dollar(50) - fee);
+
+		assert_ok!(HomaLite::request_redeem(
+			Origin::signed(ALICE),
+			dollar(50) - fee,
+			Permill::zero()
+		));
+
+		assert_eq!(Currencies::free_balance(LKSM, &ALICE), dollar(50));
+		assert_eq!(Currencies::reserved_balance(LKSM, &ALICE), dollar(50) - fee);
+
+		assert_ok!(HomaLite::request_redeem(
+			Origin::signed(ALICE),
+			dollar(100) - fee,
+			Permill::zero()
+		));
+
+		assert_eq!(Currencies::free_balance(LKSM, &ALICE), 0);
+		assert_eq!(Currencies::reserved_balance(LKSM, &ALICE), dollar(100) - fee * 2);
+
+		assert_ok!(HomaLite::request_redeem(
+			Origin::signed(ALICE),
+			dollar(10) - fee * 2,
+			Permill::zero()
+		));
+
+		assert_eq!(Currencies::free_balance(LKSM, &ALICE), dollar(90));
+		assert_eq!(Currencies::reserved_balance(LKSM, &ALICE), dollar(10) - fee * 2);
+	});
+}

runtime/karura/src/lib.rs

@@ -127,7 +127,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	spec_name: create_runtime_str!("karura"),
 	impl_name: create_runtime_str!("karura"),
 	authoring_version: 1,
-	spec_version: 1017,
+	spec_version: 1018,
 	impl_version: 0,
 	apis: RUNTIME_API_VERSIONS,
 	transaction_version: 1,