feat: OTC fees

pallets/otc/src/lib.rs

@@ -40,6 +40,7 @@ use hydradx_traits::Inspect;
 use orml_traits::{GetByKey, MultiCurrency, NamedMultiReservableCurrency};
 use sp_core::U256;
 use sp_runtime::traits::{One, Zero};
+use sp_runtime::Permill;
 
 #[cfg(test)]
 mod tests;
@@ -101,6 +102,14 @@ pub mod pallet {
 		#[pallet::constant]
 		type ExistentialDepositMultiplier: Get<u8>;
 
+		/// Fee
+		#[pallet::constant]
+		type Fee: Get<Permill>;
+
+		/// Fee receiver
+		#[pallet::constant]
+		type FeeReceiver: Get<Self::AccountId>;
+
 		/// Weight information for the extrinsics.
 		type WeightInfo: WeightInfo;
 	}
@@ -116,13 +125,15 @@ pub mod pallet {
 			who: T::AccountId,
 			amount_in: Balance,
 			amount_out: Balance,
+			fee: Balance,
 		},
 		/// An Order has been partially filled
 		PartiallyFilled {
 			order_id: OrderId,
 			who: T::AccountId,
 			amount_in: Balance,
 			amount_out: Balance,
+			fee: Balance,
 		},
 		/// An Order has been placed
 		Placed {
@@ -266,13 +277,16 @@ pub mod pallet {
 				Self::ensure_min_order_amount(order.asset_out, order.amount_out)?;
 				Self::ensure_min_order_amount(order.asset_in, order.amount_in)?;
 
-				Self::execute_order(order, &who, amount_in, amount_out)?;
+				let fee = Self::calculate_fee(order.amount_out);
+
+				Self::execute_order(order, &who, amount_in, amount_out, fee)?;
 
 				Self::deposit_event(Event::PartiallyFilled {
 					order_id,
 					who,
 					amount_in,
 					amount_out,
+					fee,
 				});
 				Ok(())
 			})
@@ -291,14 +305,17 @@ pub mod pallet {
 			let who = ensure_signed(origin)?;
 			let order = <Orders<T>>::get(order_id).ok_or(Error::<T>::OrderNotFound)?;
 
-			Self::execute_order(&order, &who, order.amount_in, order.amount_out)?;
+			let fee = Self::calculate_fee(order.amount_out);
+
+			Self::execute_order(&order, &who, order.amount_in, order.amount_out, fee)?;
 			<Orders<T>>::remove(order_id);
 
 			Self::deposit_event(Event::Filled {
 				order_id,
 				who,
 				amount_in: order.amount_in,
 				amount_out: order.amount_out,
+				fee,
 			});
 			Ok(())
 		}
@@ -352,13 +369,23 @@ impl<T: Config> Pallet<T> {
 		who: &T::AccountId,
 		amount_in: Balance,
 		amount_out: Balance,
+		fee: Balance
 	) -> DispatchResult {
 		T::Currency::transfer(order.asset_in, who, &order.owner, amount_in)?;
 		let remaining_to_unreserve =
+			// returns any amount that was unable to be unreserved
 			T::Currency::unreserve_named(&NAMED_RESERVE_ID, order.asset_out, &order.owner, amount_out);
 		ensure!(remaining_to_unreserve.is_zero(), Error::<T>::InsufficientReservedAmount);
-		T::Currency::transfer(order.asset_out, &order.owner, who, amount_out)?;
+
+		let amount_out_without_fee = amount_out.checked_sub(fee).ok_or(Error::<T>::MathError)?;
+
+		T::Currency::transfer(order.asset_out, &order.owner, who, amount_out_without_fee)?;
+		T::Currency::transfer(order.asset_out, &order.owner, &T::FeeReceiver::get(), fee)?;
 
 		Ok(())
 	}
+
+	fn calculate_fee(amount: Balance) -> Balance {
+		T::Fee::get().mul_ceil(amount)
+	}
 }

pallets/otc/src/tests/mock.rs

@@ -16,7 +16,7 @@
 use crate as otc;
 use crate::Config;
 use frame_support::{
-	parameter_types,
+	parameter_types, PalletId,
 	traits::{Everything, Nothing},
 };
 use frame_system as system;
@@ -25,8 +25,8 @@ use orml_tokens::AccountData;
 use orml_traits::parameter_type_with_key;
 use sp_core::H256;
 use sp_runtime::{
-	traits::{BlakeTwo256, IdentityLookup},
-	BuildStorage,
+	traits::{BlakeTwo256, IdentityLookup, AccountIdConversion},
+	BuildStorage, Permill,
 };
 use std::{cell::RefCell, collections::HashMap};
 
@@ -66,6 +66,9 @@ thread_local! {
 parameter_types! {
 	pub NativeCurrencyId: AssetId = HDX;
 	pub ExistentialDepositMultiplier: u8 = 5;
+	pub OtcFee: Permill = Permill::zero(); // Permill::from_rational(1u32, 1_000_u32); // 0.1%
+	pub const TreasuryPalletId: PalletId = PalletId(*b"aca/trsy");
+	pub TreasuryAccount: AccountId = TreasuryPalletId::get().into_account_truncating();
 }
 
 parameter_type_with_key! {
@@ -81,6 +84,8 @@ impl otc::Config for Test {
 	type RuntimeEvent = RuntimeEvent;
 	type ExistentialDeposits = ExistentialDeposits;
 	type ExistentialDepositMultiplier = ExistentialDepositMultiplier;
+	type Fee = OtcFee;
+	type FeeReceiver = TreasuryAccount;
 	type WeightInfo = ();
 }
 

runtime/hydradx/src/assets.rs

@@ -1114,6 +1114,7 @@ parameter_types! {
 	pub const ExistentialDepositMultiplier: u8 = 5;
 	pub const PricePrecision: FixedU128 = FixedU128::from_rational(1, 100);
 	pub MinProfitPercentage: Perbill = Perbill::from_rational(1u32, 100_000_u32); // 0.001%
+	pub OtcFee: Permill = Permill::from_rational(1u32, 1_000_u32); // 0.1%
 }
 
 impl pallet_otc::Config for Runtime {
@@ -1123,6 +1124,8 @@ impl pallet_otc::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type ExistentialDeposits = AssetRegistry;
 	type ExistentialDepositMultiplier = ExistentialDepositMultiplier;
+	type Fee = OtcFee;
+	type FeeReceiver = TreasuryAccount;
 	type WeightInfo = weights::pallet_otc::HydraWeight<Runtime>;
 }