bug fixes

substrate/client/tests/dex.rs

@@ -116,7 +116,7 @@ serai_test!(
         send_to: pair.public().into(),
         path,
         amount_in: amount_in.0,
-        amount_out: 16599866399465
+        amount_out: 16611018363939
       }]
     );
 
@@ -144,7 +144,7 @@ serai_test!(
         send_to: pair.public().into(),
         path,
         amount_in: amount_in.0,
-        amount_out: 17166744497317
+        amount_out: 17207430166736
       }]
     );
   })
@@ -210,7 +210,7 @@ serai_test!(
         send_to: pair.public().into(),
         path,
         amount_in: amount_in.0,
-        amount_out: 12406166091918,
+        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: 111669009482,
-        lp_token_minted: 1055147701082
+        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: 18933113030
+          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: 1473437558561637
+          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: 1751430396
+          amount_out: 1755477054
         }]
       );
     }

substrate/dex/pallet/src/lib.rs

@@ -992,32 +992,30 @@ 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)?;
-          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)?, *coin1)?;
+          Self::burn_half_of_swap_fee(Self::get_pool_id(*coin1, *coin2)?, *coin1, *prev_amount)?;
+
+          amounts.push(amount_out);
         }
       }
 
       Ok(amounts)
     }
 
-    fn burn_half_of_swap_fee(pool: PoolId, coin: Coin) -> Result<(), DispatchError> {
+    fn burn_half_of_swap_fee(
+      pool: PoolId,
+      coin: Coin,
+      amount: SubstrateAmount,
+    ) -> Result<(), DispatchError> {
       let pool_account = Self::get_pool_account(pool);
-      let origin = RawOrigin::Signed(pool_account);
 
-      let balance = Coins::<T>::balance(pool_account, coin).0;
-      let burn_percent =
-        HigherPrecisionBalance::from(T::LPFee::get()).checked_div(2).ok_or(Error::<T>::Overflow)?;
-
-      let burn_amount = HigherPrecisionBalance::from(balance)
-        .checked_mul(burn_percent)
-        .ok_or(Error::<T>::Overflow)?
-        .checked_div(1000)
-        .ok_or(Error::<T>::Overflow)?;
+      // 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(
-        origin.into(),
+        RawOrigin::Signed(pool_account).into(),
         Balance { coin, amount: Amount(burn_amount.try_into().map_err(|_| Error::<T>::Overflow)?) },
       )?;
       Ok(())

substrate/dex/pallet/src/tests.rs

@@ -1157,10 +1157,10 @@ fn swap_exact_tokens_for_tokens_in_multi_hops() {
     ));
 
     // burn half of the taken fees
-    let burn_amount = get_burn_amount(liquidity2);
+    let burn_amount = get_burn_amount(input_amount);
     liquidity2 -= burn_amount;
 
-    let burn_amount = get_burn_amount(liquidity1_pool2);
+    let burn_amount = get_burn_amount(expect_out2);
     liquidity1_pool2 -= burn_amount;
 
     let pool_id1 = Dex::get_pool_id(coin1, coin2).unwrap();

substrate/runtime/src/lib.rs

@@ -215,8 +215,8 @@ impl coins::Config<coins::Instance1> for Runtime {
 impl dex::Config for Runtime {
   type RuntimeEvent = RuntimeEvent;
 
-  // 0.6% in total but only half will go to LPs(0.3%) other half to be burned.
-  type LPFee = ConstU32<6>;
+  // 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