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update protocol fee docs and remove restrictions #64

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adae939
update protocol fee docs and remove restrictions
gregdhill Feb 7, 2023
e3fd328
add test that higher fee point decreases protocol fee cut
gregdhill Feb 9, 2023
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72 changes: 66 additions & 6 deletions zenlink-protocol/src/fee/tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@
// Licensed under Apache 2.0.

use super::mock::*;
use crate::{AssetId, Error, MultiAssetsHandler};
use crate::{AssetId, MultiAssetsHandler};
use frame_support::{assert_noop, assert_ok, error::BadOrigin};
use frame_system::RawOrigin;
use sp_core::U256;
Expand Down Expand Up @@ -44,11 +44,6 @@ fn fee_meta_setter_should_not_work() {
);

assert_noop!(DexPallet::set_fee_point(RawOrigin::Signed(BOB).into(), 0), BadOrigin);

assert_noop!(
DexPallet::set_fee_point(RawOrigin::Root.into(), 31u8),
Error::<Test>::InvalidFeePoint
);
})
}

Expand Down Expand Up @@ -507,3 +502,68 @@ fn turn_on_protocol_fee_swap_have_fee_at_should_work() {
assert_eq!(lp_total, lp_of_alice_0 + alice_lp_add + lp_of_bob);
});
}

#[test]
fn assert_higher_fee_point_decreases_protocol_fee() {
new_test_ext().execute_with(|| {
assert_ok!(DexPallet::set_fee_receiver(RawOrigin::Root.into(), Some(BOB)));

assert_ok!(DexPallet::foreign_mint(DOT_ASSET_ID, &ALICE, 100_000_000 * DOT_UNIT));
assert_ok!(DexPallet::foreign_mint(BTC_ASSET_ID, &ALICE, 100_000_000 * BTC_UNIT));
assert_ok!(DexPallet::foreign_mint(DOT_ASSET_ID, &CHARLIE, 100_000_000 * DOT_UNIT));

assert_ok!(DexPallet::create_pair(RawOrigin::Root.into(), DOT_ASSET_ID, BTC_ASSET_ID,));

let total_supply_dot: u128 = 1_000_000 * DOT_UNIT;
let total_supply_btc: u128 = 1_000_000 * BTC_UNIT;

assert_ok!(DexPallet::add_liquidity(
RawOrigin::Signed(ALICE).into(),
DOT_ASSET_ID,
BTC_ASSET_ID,
total_supply_dot,
total_supply_btc,
0,
0,
100
));

assert_ok!(DexPallet::inner_swap_exact_assets_for_assets(
&CHARLIE,
DOT_UNIT,
1,
&vec![DOT_ASSET_ID, BTC_ASSET_ID],
&CHARLIE,
));

fn mint_fee_for_point(fee_point: u8) -> u128 {
let reserve_0 =
<Test as Config>::MultiAssetsHandler::balance_of(DOT_ASSET_ID, &PAIR_DOT_BTC);
let reserve_1 =
<Test as Config>::MultiAssetsHandler::balance_of(BTC_ASSET_ID, &PAIR_DOT_BTC);
let total_supply = <Test as Config>::MultiAssetsHandler::total_supply(LP_DOT_BTC);
assert_ok!(DexPallet::set_fee_point(RawOrigin::Root.into(), fee_point));
DexPallet::mint_protocol_fee(
reserve_0,
reserve_1,
DOT_ASSET_ID,
BTC_ASSET_ID,
total_supply,
)
.unwrap()
}

// 1/(1/1)-1=0
let total_fee = mint_fee_for_point(0);
// 1/(1/2)-1=1
assert_eq!(mint_fee_for_point(1), total_fee / 2);
// 1/(1/4)-1=3
assert_eq!(mint_fee_for_point(3), total_fee / 4);
// 1/(1/6)-1=5
assert_eq!(mint_fee_for_point(5), total_fee / 6);
// 1/(1/10)-1=9
assert_eq!(mint_fee_for_point(9), total_fee / 10);
// 1/(1/100)-1=99
assert_eq!(mint_fee_for_point(99), total_fee / 100);
});
}
22 changes: 8 additions & 14 deletions zenlink-protocol/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -232,14 +232,10 @@ pub mod pallet {
#[pallet::genesis_config]
/// Refer: https://github.com/Uniswap/uniswap-v2-core/blob/master/contracts/UniswapV2Pair.sol#L88
pub struct GenesisConfig<T: Config> {
/// The admin of the protocol fee.
// pub fee_admin: T::AccountId,
/// The receiver of the protocol fee.
pub fee_receiver: Option<T::AccountId>,
/// The fee point which integer between [0,30]
/// 0 means no protocol fee.
/// 30 means 0.3% * 100% = 0.0030.
/// default is 5 and means 0.3% * 1 / 6 = 0.0005.
/// The higher the fee point, the smaller the
/// cut of the exchange fee taken from LPs.
pub fee_point: u8,
}

Expand Down Expand Up @@ -391,8 +387,6 @@ pub mod pallet {
RequireProtocolAdmin,
/// Require the admin candidate who can become new admin after confirm.
RequireProtocolAdminCandidate,
/// Invalid fee_point
InvalidFeePoint,
/// Unsupported AssetId by this ZenlinkProtocol Version.
UnsupportedAssetType,
/// Account balance must be greater than or equal to the transfer amount.
Expand Down Expand Up @@ -469,7 +463,7 @@ pub mod pallet {
/// - `send_to`:
/// (1) Some(receiver): it turn on the protocol fee and the new receiver account.
/// (2) None: it turn off the protocol fee.
#[pallet::call_index(0)]
#[pallet::call_index(0)]
#[pallet::weight(T::WeightInfo::set_fee_receiver())]
pub fn set_fee_receiver(
origin: OriginFor<T>,
Expand All @@ -495,15 +489,15 @@ pub mod pallet {
/// # Arguments
///
/// - `fee_point`:
/// The fee_point which integer between [0,30]
/// 0 means no protocol fee.
/// 30 means 0.3% * 100% = 0.0030.
/// default is 5 and means 0.3% * 1 / 6 = 0.0005.
/// An integer y which satisfies the equation `1/x-1=y`
/// where x is the percentage of the exchange fee, a
/// value of 0 gives everything to the fee receiver
/// e.g. 1/(1/6)-1=5, 1/(1/2)-1=1
/// See section 2.4 of the Uniswap v2 whitepaper
#[pallet::call_index(1)]
#[pallet::weight(T::WeightInfo::set_fee_point())]
pub fn set_fee_point(origin: OriginFor<T>, fee_point: u8) -> DispatchResult {
ensure_root(origin)?;
ensure!(fee_point <= 30, Error::<T>::InvalidFeePoint);

FeeMeta::<T>::mutate(|fee_meta| fee_meta.1 = fee_point);

Expand Down
53 changes: 24 additions & 29 deletions zenlink-protocol/src/swap/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -94,7 +94,7 @@ impl<T: Config> Pallet<T> {
parameter.total_supply,
)?;
if let Some(fee_to) = Self::fee_meta().0 {
if mint_fee > 0 && Self::fee_meta().1 > 0 {
if mint_fee > 0 {
T::MultiAssetsHandler::deposit(lp_asset_id, &fee_to, mint_fee)
.map(|_| mint_fee)?;
parameter.total_supply = parameter
Expand Down Expand Up @@ -125,18 +125,16 @@ impl<T: Config> Pallet<T> {
T::MultiAssetsHandler::transfer(asset_1, who, &parameter.pair_account, amount_1)?;

if let Some(_fee_to) = Self::fee_meta().0 {
if Self::fee_meta().1 > 0 {
// update reserve_0 and reserve_1
let reserve_0 =
T::MultiAssetsHandler::balance_of(asset_0, &parameter.pair_account);
let reserve_1 =
T::MultiAssetsHandler::balance_of(asset_1, &parameter.pair_account);

let last_k_value = U256::from(reserve_0)
.checked_mul(U256::from(reserve_1))
.ok_or(Error::<T>::Overflow)?;
Self::mutate_k_last(asset_0, asset_1, last_k_value);
}
// update reserve_0 and reserve_1
let reserve_0 =
T::MultiAssetsHandler::balance_of(asset_0, &parameter.pair_account);
let reserve_1 =
T::MultiAssetsHandler::balance_of(asset_1, &parameter.pair_account);

let last_k_value = U256::from(reserve_0)
.checked_mul(U256::from(reserve_1))
.ok_or(Error::<T>::Overflow)?;
Self::mutate_k_last(asset_0, asset_1, last_k_value);
}

Self::deposit_event(Event::LiquidityAdded(
Expand Down Expand Up @@ -198,7 +196,7 @@ impl<T: Config> Pallet<T> {
parameter.total_supply,
)?;
if let Some(fee_to) = Self::fee_meta().0 {
if mint_fee > 0 && Self::fee_meta().1 > 0 {
if mint_fee > 0 {
//Self::mutate_liquidity(asset_0, asset_1, &fee_to, mint_fee, true)?;
T::MultiAssetsHandler::deposit(lp_asset_id, &fee_to, mint_fee)
.map(|_| mint_fee)?;
Expand Down Expand Up @@ -232,18 +230,16 @@ impl<T: Config> Pallet<T> {
)?;

if let Some(_fee_to) = Self::fee_meta().0 {
if Self::fee_meta().1 > 0 {
// update reserve_0 and reserve_1
let reserve_0 =
T::MultiAssetsHandler::balance_of(asset_0, &parameter.pair_account);
let reserve_1 =
T::MultiAssetsHandler::balance_of(asset_1, &parameter.pair_account);

let last_k_value = U256::from(reserve_0)
.checked_mul(U256::from(reserve_1))
.ok_or(Error::<T>::Overflow)?;
Self::mutate_k_last(asset_0, asset_1, last_k_value);
}
// update reserve_0 and reserve_1
let reserve_0 =
T::MultiAssetsHandler::balance_of(asset_0, &parameter.pair_account);
let reserve_1 =
T::MultiAssetsHandler::balance_of(asset_1, &parameter.pair_account);

let last_k_value = U256::from(reserve_0)
.checked_mul(U256::from(reserve_1))
.ok_or(Error::<T>::Overflow)?;
Self::mutate_k_last(asset_0, asset_1, last_k_value);
}

Self::deposit_event(Event::LiquidityRemoved(
Expand Down Expand Up @@ -362,7 +358,7 @@ impl<T: Config> Pallet<T> {
let mut mint_fee: AssetBalance = 0;

if let Some(_fee_to) = Self::fee_meta().0 {
if !new_k_last.is_zero() && Self::fee_meta().1 > 0 {
if !new_k_last.is_zero() {
let root_k = U256::from(reserve_0)
.checked_mul(U256::from(reserve_1))
.map(|n| n.integer_sqrt())
Expand All @@ -371,13 +367,12 @@ impl<T: Config> Pallet<T> {
let root_k_last = new_k_last.integer_sqrt();
if root_k > root_k_last {
let fee_point = Self::fee_meta().1;
let fix_fee_point = (30 - fee_point) / fee_point;
let numerator = U256::from(total_liquidity)
.checked_mul(root_k.checked_sub(root_k_last).ok_or(Error::<T>::Overflow)?)
.ok_or(Error::<T>::Overflow)?;

let denominator = root_k
.checked_mul(U256::from(fix_fee_point))
.checked_mul(U256::from(fee_point))
.and_then(|n| n.checked_add(root_k_last))
.ok_or(Error::<T>::Overflow)?;

Expand Down