Fix fee (#1891)

* change fee calculation * fix fee * update weight * update benchmark * transfer all to treasury * apply review * extract calculate rate and use it in test * set threshold to 2.5 KAR * udpate testcase * cargo run --release --color=never --bin=acala --features=runtime-benchmarks --features=with-karura-runtime -- benchmark --chain=karura-dev --steps=50 --repeat=20 --pallet=module_transaction_payment --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --template=./templates/runtime-weight-template.hbs --output=./runtime/karura/src/weights/ * cargo run --release --color=never --bin=acala --features=runtime-benchmarks --features=with-acala-runtime -- benchmark --chain=acala-latest --steps=50 --repeat=20 --pallet=module_transaction_payment --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --template=./templates/runtime-weight-template.hbs --output=./runtime/acala/src/weights/ Co-authored-by: Acala Benchmarking Bot <[email protected]> Co-authored-by: Bryan Chen <[email protected]>
AcalaNetwork · Feb 16, 2022 · 14bd3bf · 14bd3bf
1 parent 4efe8a0
commit 14bd3bf
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Showing 9 changed files with 383 additions and 50 deletions.
diff --git a/modules/transaction-payment/src/lib.rs b/modules/transaction-payment/src/lib.rs
@@ -355,6 +355,8 @@ pub mod module {
 		InvalidBalance,
 		/// Can't find rate by the supply token
 		InvalidRate,
+		/// Can't find the token info in the charge fee pool
+		InvalidToken,
 		/// Dex swap pool is not available now
 		DexNotAvailable,
 		/// Charge fee pool is already exist
@@ -364,7 +366,7 @@ pub mod module {
 	}
 
 	#[pallet::event]
-	#[pallet::generate_deposit(pub(crate) fn deposit_event)]
+	#[pallet::generate_deposit(pub fn deposit_event)]
 	pub enum Event<T: Config> {
 		/// The global fee swap path was updated.
 		GlobalFeeSwapPathUpdated {
@@ -386,6 +388,19 @@ pub mod module {
 			pool_size: Balance,
 			swap_threshold: Balance,
 		},
+		/// The charge fee pool is swapped
+		ChargeFeePoolSwapped {
+			old_exchange_rate: Ratio,
+			swap_exchange_rate: Ratio,
+			new_exchange_rate: Ratio,
+			new_pool_size: Balance,
+		},
+		/// The charge fee pool is disabled
+		ChargeFeePoolDisabled {
+			currency_id: CurrencyId,
+			foreign_amount: Balance,
+			native_amount: Balance,
+		},
 	}
 
 	/// The next fee multiplier.
@@ -607,6 +622,14 @@ pub mod module {
 			T::UpdateOrigin::ensure_origin(origin)?;
 			Self::initialize_pool(currency_id, pool_size, swap_threshold)
 		}
+
+		/// Disable charge fee pool.
+		#[pallet::weight(<T as Config>::WeightInfo::disable_charge_fee_pool())]
+		#[transactional]
+		pub fn disable_charge_fee_pool(origin: OriginFor<T>, currency_id: CurrencyId) -> DispatchResult {
+			T::UpdateOrigin::ensure_origin(origin)?;
+			Self::disable_pool(currency_id)
+		}
 	}
 }
 
@@ -838,24 +861,31 @@ where
 		// this means the charge fee pool is exhausted for this given token pair.
 		// we normally set the `SwapBalanceThreshold` gt ED to prevent this case.
 		let native_balance = T::Currency::free_balance(&sub_account);
-		if native_balance < SwapBalanceThreshold::<T>::get(supply_currency_id) {
+		let threshold_balance = SwapBalanceThreshold::<T>::get(supply_currency_id);
+		if native_balance < threshold_balance {
 			let trading_path = Self::get_trading_path_by_currency(&sub_account, supply_currency_id);
 			if let Some(trading_path) = trading_path {
 				let supply_balance = T::MultiCurrency::free_balance(supply_currency_id, &sub_account);
 				let supply_amount =
 					supply_balance.saturating_sub(T::MultiCurrency::minimum_balance(supply_currency_id));
-				if let Ok((_, swap_native_balance)) = T::DEX::swap_with_specific_path(
+				if let Ok((supply_amount, swap_native_balance)) = T::DEX::swap_with_specific_path(
 					&sub_account,
 					&trading_path,
 					SwapLimit::ExactSupply(supply_amount, 0),
 				) {
 					// calculate and update new rate, also update the pool size
+					let swap_exchange_rate = Ratio::saturating_from_rational(supply_amount, swap_native_balance);
 					let new_pool_size = swap_native_balance.saturating_add(native_balance);
-					let new_native_balance = rate.saturating_mul_int(new_pool_size);
-					let next_updated_rate =
-						Ratio::saturating_from_rational(new_native_balance, PoolSize::<T>::get(supply_currency_id));
-					TokenExchangeRate::<T>::insert(supply_currency_id, next_updated_rate);
+					let new_exchange_rate = Self::calculate_exchange_rate(supply_currency_id, swap_exchange_rate)?;
+
+					TokenExchangeRate::<T>::insert(supply_currency_id, new_exchange_rate);
 					PoolSize::<T>::insert(supply_currency_id, new_pool_size);
+					Pallet::<T>::deposit_event(Event::<T>::ChargeFeePoolSwapped {
+						old_exchange_rate: rate,
+						swap_exchange_rate,
+						new_exchange_rate,
+						new_pool_size,
+					});
 				} else {
 					debug_assert!(false, "Swap tx fee pool should not fail!");
 				}
@@ -910,8 +940,21 @@ where
 		T::PalletId::get().into_sub_account(id)
 	}
 
-	/// Initiate a charge fee swap pool. Usually used in `on_runtime_upgrade` or manual
-	/// `enable_charge_fee_pool` dispatch call.
+	/// Calculate the new exchange rate.
+	/// old_rate * (threshold/poolSize) + swap_exchange_rate * (1-threshold/poolSize)
+	fn calculate_exchange_rate(currency_id: CurrencyId, swap_exchange_rate: Ratio) -> Result<Ratio, Error<T>> {
+		let threshold_balance = SwapBalanceThreshold::<T>::get(currency_id);
+		let old_threshold_rate = Ratio::saturating_from_rational(threshold_balance, PoolSize::<T>::get(currency_id));
+		let new_threshold_rate = Ratio::one().saturating_sub(old_threshold_rate);
+
+		let rate = TokenExchangeRate::<T>::get(currency_id).ok_or(Error::<T>::InvalidRate)?;
+		let old_parts = rate.saturating_mul(old_threshold_rate);
+		let new_parts = swap_exchange_rate.saturating_mul(new_threshold_rate);
+		let new_exchange_rate = old_parts.saturating_add(new_parts);
+		Ok(new_exchange_rate)
+	}
+
+	/// Initiate a charge fee pool, transfer token from treasury account to sub account.
 	fn initialize_pool(currency_id: CurrencyId, pool_size: Balance, swap_threshold: Balance) -> DispatchResult {
 		let treasury_account = T::TreasuryAccount::get();
 		let sub_account = Self::sub_account_id(currency_id);
@@ -950,14 +993,46 @@ where
 		SwapBalanceThreshold::<T>::insert(currency_id, swap_threshold);
 		TokenExchangeRate::<T>::insert(currency_id, exchange_rate);
 		PoolSize::<T>::insert(currency_id, pool_size);
+
 		Self::deposit_event(Event::ChargeFeePoolEnabled {
 			sub_account,
 			currency_id,
 			exchange_rate,
 			pool_size,
 			swap_threshold,
 		});
+		Ok(())
+	}
 
+	/// Disable a charge fee pool, return token from sub account to treasury account.
+	fn disable_pool(currency_id: CurrencyId) -> DispatchResult {
+		ensure!(
+			TokenExchangeRate::<T>::contains_key(currency_id),
+			Error::<T>::InvalidToken
+		);
+		let treasury_account = T::TreasuryAccount::get();
+		let sub_account = Self::sub_account_id(currency_id);
+		let foreign_amount: Balance = T::MultiCurrency::free_balance(currency_id, &sub_account);
+		let native_amount: Balance = T::Currency::free_balance(&sub_account);
+
+		T::MultiCurrency::transfer(currency_id, &sub_account, &treasury_account, foreign_amount)?;
+		T::Currency::transfer(
+			&sub_account,
+			&treasury_account,
+			native_amount,
+			ExistenceRequirement::AllowDeath,
+		)?;
+
+		// remove map entry, then `swap_from_pool_or_dex` method will throw error.
+		TokenExchangeRate::<T>::remove(currency_id);
+		PoolSize::<T>::remove(currency_id);
+		SwapBalanceThreshold::<T>::remove(currency_id);
+
+		Self::deposit_event(Event::ChargeFeePoolDisabled {
+			currency_id,
+			foreign_amount,
+			native_amount,
+		});
 		Ok(())
 	}
 }

diff --git a/modules/transaction-payment/src/mock.rs b/modules/transaction-payment/src/mock.rs
@@ -236,11 +236,12 @@ impl PriceProvider<CurrencyId> for MockPriceSource {
 parameter_types! {
 	// DO NOT CHANGE THIS VALUE, AS IT EFFECT THE TESTCASES.
 	pub const FeePoolSize: Balance = 10_000;
-	pub const SwapThreshold: Balance = 20;
+	pub const LowerSwapThreshold: Balance = 20;
+	pub const MiddSwapThreshold: Balance = 5000;
+	pub const HigerSwapThreshold: Balance = 9500;
 	pub const TransactionPaymentPalletId: PalletId = PalletId(*b"aca/fees");
 	pub const TreasuryPalletId: PalletId = PalletId(*b"aca/trsy");
 	pub KaruraTreasuryAccount: AccountId = TreasuryPalletId::get().into_account();
-	pub FeePoolExchangeTokens: Vec<CurrencyId> = vec![AUSD, DOT];
 }
 ord_parameter_types! {
 	pub const ListingOrigin: AccountId = ALICE;