diff --git a/substrate/client/tests/dex.rs b/substrate/client/tests/dex.rs
index 93422f5e..3127c883 100644
--- a/substrate/client/tests/dex.rs
+++ b/substrate/client/tests/dex.rs
@@ -116,7 +116,7 @@ serai_test!(
send_to: pair.public().into(),
path,
amount_in: amount_in.0,
- amount_out: 16633299966633
+ amount_out: 16611018363939
}]
);
@@ -144,7 +144,7 @@ serai_test!(
send_to: pair.public().into(),
path,
amount_in: amount_in.0,
- amount_out: 17254428681101
+ amount_out: 17207430166736
}]
);
})
@@ -210,7 +210,7 @@ serai_test!(
send_to: pair.public().into(),
path,
amount_in: amount_in.0,
- amount_out: 12453103964435,
+ amount_out: 12421816676180,
}]
);
})
@@ -264,8 +264,8 @@ serai_test!(
mint_to: pair.public().into(),
pool_id: coin,
coin_amount: 10_000_000_000_000, // half of sent amount
- sri_amount: 111_333_778_668,
- lp_token_minted: 1_054_092_553_383
+ sri_amount: 111631562261,
+ lp_token_minted: 1055499886564
}]
);
})
@@ -349,7 +349,7 @@ serai_test!(
send_to: IN_INSTRUCTION_EXECUTOR,
path,
amount_in: 200_000_000_000_000,
- amount_out: 19_044_944_233
+ amount_out: 18970355346
}]
);
}
@@ -388,7 +388,7 @@ serai_test!(
send_to: out_address.as_native().unwrap(),
path,
amount_in: 200_000_000_000,
- amount_out: 1487294253782353
+ amount_out: 1482888317565764
}]
);
}
@@ -426,7 +426,7 @@ serai_test!(
send_to: out_address.as_native().unwrap(),
path,
amount_in: 100_000_000_000_000,
- amount_out: 1_762_662_819
+ amount_out: 1755477054
}]
);
}
diff --git a/substrate/dex/pallet/src/lib.rs b/substrate/dex/pallet/src/lib.rs
index 8da63a7b..613568da 100644
--- a/substrate/dex/pallet/src/lib.rs
+++ b/substrate/dex/pallet/src/lib.rs
@@ -81,7 +81,7 @@ mod mock;
use frame_support::{ensure, pallet_prelude::*, BoundedBTreeSet};
use frame_system::{
pallet_prelude::{BlockNumberFor, OriginFor},
- ensure_signed,
+ ensure_signed, RawOrigin,
};
pub use pallet::*;
@@ -109,7 +109,7 @@ pub mod pallet {
use sp_core::sr25519::Public;
- use coins_pallet::{Pallet as CoinsPallet, Config as CoinsConfig};
+ use coins_pallet::{Pallet as Coins, Config as CoinsConfig};
/// Pool ID.
///
@@ -828,7 +828,7 @@ pub mod pallet {
to: &T::AccountId,
balance: Balance,
) -> Result<Amount, DispatchError> {
- CoinsPallet::<T>::transfer_internal(*from, *to, balance)?;
+ Coins::<T>::transfer_internal(*from, *to, balance)?;
Ok(balance.amount)
}
@@ -927,7 +927,7 @@ pub mod pallet {
/// Get the `owner`'s balance of `coin`, which could be the chain's native coin or another
/// fungible. Returns a value in the form of an `Amount`.
fn get_balance(owner: &T::AccountId, coin: Coin) -> SubstrateAmount {
- CoinsPallet::<T>::balance(*owner, coin).0
+ Coins::<T>::balance(*owner, coin).0
}
/// Returns a pool id constructed from 2 coins.
@@ -992,6 +992,10 @@ pub mod pallet {
let (reserve_in, reserve_out) = Self::get_reserves(coin1, coin2)?;
let prev_amount = amounts.last().expect("Always has at least one element");
let amount_out = Self::get_amount_out(*prev_amount, reserve_in, reserve_out)?;
+
+ // now that we got swap fee from the user, burn half of it.
+ Self::burn_half_of_swap_fee(Self::get_pool_id(*coin1, *coin2)?, *coin1, *prev_amount)?;
+
amounts.push(amount_out);
}
}
@@ -999,6 +1003,24 @@ pub mod pallet {
Ok(amounts)
}
+ fn burn_half_of_swap_fee(
+ pool: PoolId,
+ coin: Coin,
+ amount: SubstrateAmount,
+ ) -> Result<(), DispatchError> {
+ let pool_account = Self::get_pool_account(pool);
+
+ // half of the taken fee
+ let burn_percent = T::LPFee::get().checked_div(2).ok_or(Error::<T>::Overflow)?;
+ let burn_amount = Self::mul_div(amount, burn_percent.into(), 1000)?;
+
+ Coins::<T>::burn(
+ RawOrigin::Signed(pool_account).into(),
+ Balance { coin, amount: Amount(burn_amount) },
+ )?;
+ Ok(())
+ }
+
/// Used by the RPC service to provide current prices.
pub fn quote_price_exact_tokens_for_tokens(
coin1: Coin,
diff --git a/substrate/dex/pallet/src/tests.rs b/substrate/dex/pallet/src/tests.rs
index 8770b517..82fa0a1b 100644
--- a/substrate/dex/pallet/src/tests.rs
+++ b/substrate/dex/pallet/src/tests.rs
@@ -29,6 +29,7 @@ pub use coins_pallet as coins;
use coins::Pallet as CoinsPallet;
use serai_primitives::{Balance, COINS, PublicKey, system_address, Amount};
+use sp_core::Get;
type LiquidityTokens<T> = coins_pallet::Pallet<T, coins::Instance1>;
type LiquidityTokensError<T> = coins_pallet::Error<T, coins::Instance1>;
@@ -63,6 +64,20 @@ fn pool_balance(owner: PublicKey, token_id: Coin) -> u64 {
LiquidityTokens::<Test>::balance(owner, token_id).0
}
+fn get_burn_amount(liquidity: u64) -> u64 {
+ // burn half of the swap fee left in the pool
+ let burn_percent = HigherPrecisionBalance::from(<<Test as Config>::LPFee as Get<u32>>::get())
+ .checked_div(2)
+ .unwrap();
+
+ let burn_amount = HigherPrecisionBalance::from(liquidity)
+ .checked_mul(burn_percent)
+ .unwrap()
+ .checked_div(1000)
+ .unwrap();
+ u64::try_from(burn_amount).unwrap()
+}
+
macro_rules! bvec {
($( $x:tt )*) => {
vec![$( $x )*].try_into().unwrap()
@@ -1083,15 +1098,16 @@ fn swap_exact_tokens_for_tokens_in_multi_hops() {
assert_ok!(CoinsPallet::<Test>::mint(user, Balance { coin: coin2, amount: Amount(base2) }));
assert_ok!(CoinsPallet::<Test>::mint(user, Balance { coin: coin3, amount: Amount(base2) }));
- let liquidity1 = 10000;
- let liquidity2 = 200;
+ let liquidity1_pool1 = 10000;
+ let mut liquidity1_pool2 = liquidity1_pool1;
+ let mut liquidity2 = 200;
let liquidity3 = 2000;
assert_ok!(Dex::add_liquidity(
RuntimeOrigin::signed(user),
coin2.try_into().unwrap(),
liquidity2,
- liquidity1,
+ liquidity1_pool1,
1,
1,
user,
@@ -1100,15 +1116,15 @@ fn swap_exact_tokens_for_tokens_in_multi_hops() {
RuntimeOrigin::signed(user),
coin3.try_into().unwrap(),
liquidity3,
- liquidity1,
+ liquidity1_pool2,
1,
1,
user,
));
let input_amount = 500;
- let expect_out2 = Dex::get_amount_out(input_amount, liquidity2, liquidity1).ok().unwrap();
- let expect_out3 = Dex::get_amount_out(expect_out2, liquidity1, liquidity3).ok().unwrap();
+ let expect_out2 = Dex::get_amount_out(input_amount, liquidity2, liquidity1_pool1).ok().unwrap();
+ let expect_out3 = Dex::get_amount_out(expect_out2, liquidity1_pool2, liquidity3).ok().unwrap();
assert_noop!(
Dex::swap_exact_tokens_for_tokens(
@@ -1140,6 +1156,13 @@ fn swap_exact_tokens_for_tokens_in_multi_hops() {
user,
));
+ // burn half of the taken fees
+ let burn_amount = get_burn_amount(input_amount);
+ liquidity2 -= burn_amount;
+
+ let burn_amount = get_burn_amount(expect_out2);
+ liquidity1_pool2 -= burn_amount;
+
let pool_id1 = Dex::get_pool_id(coin1, coin2).unwrap();
let pool_id2 = Dex::get_pool_id(coin1, coin3).unwrap();
let pallet_account1 = Dex::get_pool_account(pool_id1);
@@ -1147,8 +1170,8 @@ fn swap_exact_tokens_for_tokens_in_multi_hops() {
assert_eq!(balance(user, coin2), base2 - liquidity2 - input_amount);
assert_eq!(balance(pallet_account1, coin2), liquidity2 + input_amount);
- assert_eq!(balance(pallet_account1, coin1), liquidity1 - expect_out2);
- assert_eq!(balance(pallet_account2, coin1), liquidity1 + expect_out2);
+ assert_eq!(balance(pallet_account1, coin1), liquidity1_pool1 - expect_out2);
+ assert_eq!(balance(pallet_account2, coin1), liquidity1_pool2 + expect_out2);
assert_eq!(balance(pallet_account2, coin3), liquidity3 - expect_out3);
assert_eq!(balance(user, coin3), 10000 - liquidity3 + expect_out3);
});
diff --git a/substrate/runtime/src/lib.rs b/substrate/runtime/src/lib.rs
index d9d11e34..b458343f 100644
--- a/substrate/runtime/src/lib.rs
+++ b/substrate/runtime/src/lib.rs
@@ -215,7 +215,8 @@ impl coins::Config<coins::Instance1> for Runtime {
impl dex::Config for Runtime {
type RuntimeEvent = RuntimeEvent;
- type LPFee = ConstU32<3>; // 0.3%
+ // 0.5% in total but only half will go to LPs(0.25%) other half to be burned.
+ type LPFee = ConstU32<5>;
type MintMinLiquidity = ConstU64<10000>;
type MaxSwapPathLength = ConstU32<3>; // coin1 -> SRI -> coin2