bug fixes

substrate/client/tests/dex.rs

@@ -131,7 +131,7 @@ serai_test!(
         send_to: pair.public().into(),
         path,
         amount_in: amount_in.0,
-        amount_out: 17260886638951
+        amount_out: 17166744497317
       }]
     );
   })
@@ -246,8 +246,8 @@ serai_test!(
         mint_to: pair.public().into(),
         pool_id: Coin::Bitcoin,
         coin_amount: 10_000_000_000_000, // half of sent amount
-        sri_amount: 110557340473,
-        lp_token_minted: 1054092553386
+        sri_amount: 111669009482,
+        lp_token_minted: 1055147701082
       }]
     );
   })
@@ -372,7 +372,7 @@ serai_test!(
           send_to: out_address.as_native().unwrap(),
           path,
           amount_in: 200_000_000_000,
-          amount_out: 1487256912435088
+          amount_out: 1473437558561637
         }]
       );
     }
@@ -410,7 +410,7 @@ serai_test!(
           send_to: out_address.as_native().unwrap(),
           path,
           amount_in: 100_000_000_000_000,
-          amount_out: 1760904169
+          amount_out: 1751430396
         }]
       );
     }

substrate/dex/pallet/src/lib.rs

@@ -981,7 +981,7 @@ pub mod pallet {
           amounts.push(amount_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)?, *coin2)?;
+          Self::burn_half_of_swap_fee(Self::get_pool_id(*coin1, *coin2)?, *coin1)?;
         }
       }
 
@@ -990,7 +990,7 @@ pub mod pallet {
 
     fn burn_half_of_swap_fee(pool: PoolId, coin: Coin) -> Result<(), DispatchError> {
       let pool_account = Self::get_pool_account(pool);
-      let origin = RawOrigin::Signed(pool_account.into());
+      let origin = RawOrigin::Signed(pool_account);
 
       let balance = Coins::<T>::balance(pool_account, coin).0;
       let burn_percent =

substrate/dex/pallet/src/tests.rs

@@ -26,6 +26,7 @@ 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>;
@@ -60,6 +61,20 @@ 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()
@@ -1013,15 +1028,16 @@ 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,
       liquidity2,
-      liquidity1,
+      liquidity1_pool1,
       1,
       1,
       user,
@@ -1030,15 +1046,15 @@ fn swap_exact_tokens_for_tokens_in_multi_hops() {
       RuntimeOrigin::signed(user),
       coin3,
       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(
@@ -1070,6 +1086,13 @@ fn swap_exact_tokens_for_tokens_in_multi_hops() {
       user,
     ));
 
+    // burn half of the taken fees
+    let burn_amount = get_burn_amount(liquidity2);
+    liquidity2 -= burn_amount;
+
+    let burn_amount = get_burn_amount(liquidity1_pool2);
+    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);
@@ -1077,8 +1100,8 @@ 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);
   });