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Fix XST LP fees calculation #635

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merged 3 commits into from
Jul 31, 2023
Merged

Fix XST LP fees calculation #635

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3200097
fix
pakrentos Jul 28, 2023
a0105fe
Merge branch 'develop' into fix/xst-lp-fees-fix
pakrentos Jul 31, 2023
6e1948a
Merge branch 'develop' into fix/xst-lp-fees-fix
vovac12 Jul 31, 2023
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4 changes: 2 additions & 2 deletions pallets/xst/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -852,11 +852,11 @@ impl<T: Config> Pallet<T> {
<T as pallet::Config>::PriceToolsPallet::get_average_price(
&T::GetSyntheticBaseAssetId::get(),
&T::GetBaseAssetId::get(),
// Since `Sell` is more expensive in case if we are selling XST
// Since `Buy` is more expensive in case if we are buying XOR
// (x XST -> y XOR; y XOR -> x' XST, x' < x),
// it seems logical to show this amount in order
// to not accidentally lie about the price.
PriceVariant::Sell,
PriceVariant::Buy,
)?
.into();
Ok((fee_amount * output_to_base)
Expand Down
28 changes: 14 additions & 14 deletions pallets/xst/src/tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -356,8 +356,8 @@ mod tests {
// amount in = 100 XSTUSD (A_in)
// amount out = (A_in * S) / X = (100 * 1) / 220 = 0.(45) XST (A_out)
// deduced fee = A_out * F = 0.(45) * 0.00666 = 0.0030(27) XST (F_xst)
// deduced fee in XOR = F_xst / X_b = 0.0030(27) / 0.6 = 0.0050(45) XOR (since we are buying XOR with XST)
assert_approx_eq!(price_a.fee, balance!(0.005045454545454545), 2);
// deduced fee in XOR = F_xst / X_b = 0.0030(27) / 0.6 = 0.0060(54) XOR (since we are buying XOR with XST)
assert_approx_eq!(price_a.fee, balance!(0.006054545454545454), 2);
// amount out with deduced fee = A_out - F_xst = 0.(45) - 0.0030(27) = 0.4515(18) XST
assert_approx_eq!(price_a.amount, balance!(0.451518181818181818), 2);

Expand All @@ -371,7 +371,7 @@ mod tests {
.unwrap();
assert_eq!(price_b.fee, balance!(0));
// we need to convert XOR fee back to XST
let xst_fee = (FixedWrapper::from(price_a.fee)*balance!(0.6)).into_balance();
let xst_fee = (FixedWrapper::from(price_a.fee)*balance!(0.5)).into_balance();
assert_approx_eq!(price_b.amount, xst_fee + price_a.amount, 2);

let (price_a, _) = XSTPool::quote(
Expand All @@ -393,8 +393,8 @@ mod tests {
// amount out = 100 XST (A_in)
// deduced fee = A_out / (1 - F_r) - A_out = 100 / (1 - 0.00666) - 100 = 0.670465298890611 XST (F_xst)
// amount in = ((A_out + F_xst) * X) / S = ((100 + 0.670465298890611) * 220) / 1 = 22147.5023657559344 XSTUSD (A_in)
// deduced fee in XOR = F_xst / X_b = 0.670465298890611 / 0.6 = 1.11744216481768504 XOR (since we are buying XOR with XST)
assert_approx_eq!(price_a.fee, balance!(1.11744216481768504), 1000);
// deduced fee in XOR = F_xst / X_b = 0.670465298890611 / 0.5 = 1.340930597781222944 XOR (since we are buying XOR with XST)
assert_approx_eq!(price_a.fee, balance!(1.340930597781222944), 1000);
assert_approx_eq!(price_a.amount, balance!(22147.5023657559344), 1000_000);

let (price_b, _) = XSTPool::quote(
Expand Down Expand Up @@ -465,8 +465,8 @@ mod tests {
// amount in = 100 XSTUSD (A_in)
// amount out = (A_in * S) / X = (100 * 1) / 220 = 0.(45) XST (A_out)
// deduced fee = A_out * F = 0.(45) * 0.00666 = 0.0030(27) XST (F_xst)
// deduced fee in XOR = F_xst / X_b = 0.0030(27) / 0.6 = 0.0050(45) XOR (since we are buying XOR with XST)
assert_approx_eq!(price_a.fee, balance!(0.005045454545454545), 2);
// deduced fee in XOR = F_xst / X_b = 0.0030(27) / 0.5 = 0.0060(54) XOR (since we are buying XOR with XST)
assert_approx_eq!(price_a.fee, balance!(0.006054545454545454), 2);

// Sell
let (price_c, _) = XSTPool::quote(
Expand Down Expand Up @@ -497,9 +497,9 @@ mod tests {
// amount out = 100 XSTUSD (A_out)
// amount in = (A_out * S) / X = (100 * 1) / 150 = 0.(6) XST (A_in)
// deduced fee = A_in / (1 - F) - A_in = 0.(6) / (1 - 0.00666) - A_in ~ 0.004469768659270743 XST (F_xst)
// deduced fee in XOR = F_xst / X_b = 0.004469768659270743 / 0.6 ~ 0.007449614432117905 XOR
// deduced fee in XOR = F_xst / X_b = 0.004469768659270743 / 0.5 ~ 0.008939537319 XOR
// (since we are buying XOR with XST)
assert_approx_eq!(price_c.fee, balance!(0.007449614432117905), 2);
assert_approx_eq!(price_c.fee, balance!(0.008939537318541485), 2);
});
}

Expand Down Expand Up @@ -741,7 +741,7 @@ mod tests {
let xst_to_xor_price = PriceTools::get_average_price(
&XST.into(),
&XOR.into(),
PriceVariant::Sell,
PriceVariant::Buy,
).expect("Expected to calculate price XST->XOR");
let expected_fee_amount = FixedWrapper::from(quote_amount.amount() / 2) * FixedWrapper::from(xst_to_xor_price);

Expand Down Expand Up @@ -880,9 +880,9 @@ mod tests {
// fee ratio for XSTEURO = 0.3 (F_r)
// amount in = 100 XST (A_in)
// amount out = (A_in * X * (1 - F_r)) / S = (100 * 150 * 0.7) / 3 = 3500 XSTEURO (A_out)
// fee = F_xst / X_b = 0.3 * 100 / 0.6 = 50 XOR
// fee = F_xst / X_b = 0.3 * 100 / 0.5 = 60 XOR
assert_approx_eq!(swap_outcome_before.amount, balance!(3500), 10000);
assert_approx_eq!(swap_outcome_before.fee, balance!(50), 10000);
assert_approx_eq!(swap_outcome_before.fee, balance!(60), 10000);

assert_ok!(XSTPool::set_synthetic_asset_fee(
RuntimeOrigin::root(),
Expand All @@ -908,9 +908,9 @@ mod tests {
// fee ratio for XSTEURO = 0.6 (F_r) <- dynamic fee + synthetic fee
// amount in = 100 XST (A_in)
// amount out = (A_in * X * (1 - F_r)) / S = (100 * 150 * 0.4) / 3 = 2000 XSTEURO (A_out)
// fee = F_xst / X_b = 0.6 * 100 / 0.6 = 100 XOR
// fee = F_xst / X_b = 0.6 * 100 / 0.5 = 120 XOR
assert_approx_eq!(swap_outcome_after.amount, balance!(2000), 10000);
assert_approx_eq!(swap_outcome_after.fee, balance!(100), 10000);
assert_approx_eq!(swap_outcome_after.fee, balance!(120), 10000);
});
}

Expand Down