off-by-one (#1747)

* always transfer one more ksm to fix rounding issue

* add integration tests

Co-authored-by: Frank Yin <Test Account>

runtime/integration-tests/src/lib.rs

@@ -88,6 +88,13 @@ mod runtime;
 ))]
 mod session_manager;
 
+#[cfg(any(
+	feature = "with-mandala-runtime",
+	feature = "with-karura-runtime",
+	feature = "with-acala-runtime"
+))]
+mod stable_asset;
+
 #[cfg(any(
 	feature = "with-mandala-runtime",
 	feature = "with-karura-runtime",

runtime/integration-tests/src/setup.rs

@@ -52,11 +52,12 @@ mod mandala_imports {
 		HomaXcm, Honzon, IdleScheduler, Loans, MaxTipsOfPriority, MinRewardDistributeAmount, MinimumDebitValue,
 		MultiLocation, NativeTokenExistentialDeposit, NetworkId, NftPalletId, OneDay, Origin, OriginCaller,
 		PalletCurrency, ParachainInfo, ParachainSystem, Proxy, ProxyType, Runtime, Scheduler, Session, SessionKeys,
-		SessionManager, SevenDays, System, Timestamp, TipPerWeightStep, TokenSymbol, Tokens, TransactionPayment,
-		TreasuryAccount, TreasuryPalletId, UncheckedExtrinsic, Utility, Vesting, XcmConfig, XcmExecutor, EVM, NFT,
+		SessionManager, SevenDays, StableAsset, StableAssetPalletId, System, Timestamp, TipPerWeightStep, TokenSymbol,
+		Tokens, TransactionPayment, TreasuryAccount, TreasuryPalletId, UncheckedExtrinsic, Utility, Vesting, XcmConfig,
+		XcmExecutor, EVM, NFT,
 	};
 
-	pub use runtime_common::{cent, dollar, millicent, ACA, AUSD, DOT, LDOT};
+	pub use runtime_common::{cent, dollar, millicent, ACA, AUSD, DOT, KSM, LDOT, LKSM};
 	pub const NATIVE_CURRENCY: CurrencyId = ACA;
 	pub const LIQUID_CURRENCY: CurrencyId = LDOT;
 	pub const RELAY_CHAIN_CURRENCY: CurrencyId = DOT;

runtime/integration-tests/src/stable_asset.rs

@@ -0,0 +1,77 @@
+// This file is part of Acala.
+
+// Copyright (C) 2020-2021 Acala Foundation.
+// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+use crate::setup::*;
+use module_asset_registry::AssetMetadata;
+
+#[cfg(feature = "with-mandala-runtime")]
+#[test]
+fn test_mint() {
+	ExtBuilder::default()
+		.balances(vec![
+			(
+				// NetworkContractSource
+				MockAddressMapping::get_account_id(&H160::from_low_u64_be(0)),
+				NATIVE_CURRENCY,
+				1_000_000_000 * dollar(NATIVE_CURRENCY),
+			),
+			(AccountId::from(ALICE), KSM, 1_000_000_000 * dollar(NATIVE_CURRENCY)),
+			(AccountId::from(ALICE), LKSM, 12_000_000_000 * dollar(NATIVE_CURRENCY)),
+		])
+		.build()
+		.execute_with(|| {
+			let pool_asset = CurrencyId::StableAssetPoolToken(0);
+			assert_ok!(StableAsset::create_pool(
+				Origin::root(),
+				pool_asset,
+				vec![KSM, LKSM],
+				vec![1u128, 1u128],
+				10_000_000u128,
+				20_000_000u128,
+				50_000_000u128,
+				1_000u128,
+				AccountId::from(BOB),
+				AccountId::from(CHARLIE),
+				1_000_000_000_000u128,
+			));
+			let asset_metadata = AssetMetadata {
+				name: b"Token Name".to_vec(),
+				symbol: b"TN".to_vec(),
+				decimals: 12,
+				minimal_balance: 1,
+			};
+			assert_ok!(AssetRegistry::register_stable_asset(
+				RawOrigin::Root.into(),
+				Box::new(asset_metadata.clone())
+			));
+			let ksm_target_amount = 10_000_123u128;
+			let lksm_target_amount = 10_000_456u128;
+			let exchange_rate = Homa::current_exchange_rate();
+			let account_id: AccountId = StableAssetPalletId::get().into_sub_account(0);
+			assert_ok!(StableAsset::mint(
+				Origin::signed(AccountId::from(ALICE)),
+				0,
+				vec![ksm_target_amount, lksm_target_amount],
+				0u128
+			));
+			assert_eq!(Currencies::free_balance(KSM, &account_id), ksm_target_amount);
+			let lksm_balance = Currencies::free_balance(LKSM, &account_id);
+			let converted_lksm_balance = exchange_rate.checked_mul_int(lksm_balance).unwrap_or_default();
+			assert_eq!(converted_lksm_balance >= lksm_target_amount, true);
+		});
+}

runtime/mandala/src/lib.rs

@@ -1855,11 +1855,16 @@ impl orml_tokens::ConvertBalance<Balance, Balance> for ConvertBalanceHoma {
 	}
 
 	fn convert_balance_back(balance: Balance, asset_id: CurrencyId) -> Balance {
+		/*
+		 * When overflow occurs, it's better to return 0 than max because returning zero will fail the
+		 * current transaction. If returning max here, the current transaction won't fail but latter
+		 * transactions have a possibility to fail, and this is undesirable.
+		 */
 		match asset_id {
 			CurrencyId::Token(TokenSymbol::LKSM) => Homa::get_exchange_rate()
 				.reciprocal()
-				.unwrap_or_default()
-				.checked_mul_int(balance)
+				.and_then(|x| x.checked_mul_int(balance))
+				.and_then(|x| x.checked_add(1))
 				.unwrap_or_default(),
 			_ => balance,
 		}