@dahlia-labs/stableswap-sdk
Version:
SDK for Mobius's StableSwap program.
206 lines • 10 kB
JavaScript
import { Fraction, ONE, TEN, TokenAmount, ZERO, } from "@dahlia-labs/token-utils";
import JSBI from "jsbi";
import mapValues from "lodash.mapvalues";
import { computeD, computeY } from "./curve";
export const normalizeAmount = (tokenAmount) => JSBI.multiply(tokenAmount.raw, JSBI.exponentiate(TEN, JSBI.BigInt(18 - tokenAmount.token.decimals)));
export const denormalizeAmount = (tokenAmount) => new TokenAmount(tokenAmount.token, JSBI.divide(tokenAmount.raw, JSBI.exponentiate(TEN, JSBI.BigInt(18 - tokenAmount.token.decimals))));
/**
* Calculates the current virtual price of the exchange.
* @param exchange
* @returns
*/
export const calculateVirtualPrice = (exchange) => {
const amount = exchange.lpTotalSupply;
if (amount === undefined || amount.equalTo(0)) {
// pool has no tokens
return null;
}
const price = new Fraction(computeD(exchange.ampFactor, normalizeAmount(exchange.reserves[0]), normalizeAmount(exchange.reserves[1])), amount.raw);
return price;
};
/**
* Calculates the estimated output amount of a swap.
* @param exchange
* @param fromAmount
* @returns
*/
export const calculateEstimatedSwapOutputAmount = (exchange, fromAmount) => {
const [fromReserves, toReserves] = fromAmount.token.equals(exchange.reserves[0].token)
? [exchange.reserves[0], exchange.reserves[1]]
: [exchange.reserves[1], exchange.reserves[0]];
if (fromAmount.equalTo(0)) {
const zero = new TokenAmount(toReserves.token, ZERO);
return {
outputAmountBeforeFees: zero,
outputAmount: zero,
fee: zero,
lpFee: zero,
adminFee: zero,
};
}
const amp = exchange.ampFactor;
const amountBeforeFees = JSBI.subtract(normalizeAmount(toReserves), computeY(amp, JSBI.add(normalizeAmount(fromReserves), normalizeAmount(fromAmount)), computeD(amp, normalizeAmount(fromReserves), normalizeAmount(toReserves))));
const outputAmountBeforeFees = new TokenAmount(toReserves.token, amountBeforeFees);
const fee = new TokenAmount(toReserves.token, exchange.fees.trade.asFraction.multiply(amountBeforeFees).quotient);
const adminFee = new TokenAmount(toReserves.token, exchange.fees.admin.asFraction.multiply(fee.raw).quotient);
const lpFee = fee.subtract(adminFee);
const outputAmount = new TokenAmount(toReserves.token, JSBI.subtract(amountBeforeFees, fee.raw));
return {
outputAmountBeforeFees: denormalizeAmount(outputAmountBeforeFees),
outputAmount: denormalizeAmount(outputAmount),
fee: denormalizeAmount(fee),
lpFee: denormalizeAmount(lpFee),
adminFee: denormalizeAmount(adminFee),
};
};
const N_COINS = JSBI.BigInt(2);
/**
* Calculates the amount of tokens withdrawn if only withdrawing one token.
* @returns
*/
export const calculateEstimatedWithdrawOneAmount = ({ exchange, poolTokenAmount, withdrawToken, }) => {
if (poolTokenAmount.equalTo(0)) {
// final quantities
const quantities = {
withdrawAmount: ZERO,
withdrawAmountBeforeFees: ZERO,
swapFee: ZERO,
withdrawFee: ZERO,
lpSwapFee: ZERO,
adminSwapFee: ZERO,
};
return mapValues(quantities, (q) => new TokenAmount(withdrawToken, q));
}
const { ampFactor, fees } = exchange;
const withdrawReserves = exchange.reserves.find((r) => r.token.equals(withdrawToken));
const nonWithdrawReserves = exchange.reserves.find((r) => !r.token.equals(withdrawToken));
const baseReserves = withdrawReserves
? normalizeAmount(withdrawReserves)
: ZERO;
const quoteReserves = nonWithdrawReserves
? normalizeAmount(nonWithdrawReserves)
: ZERO;
const d_0 = computeD(ampFactor, baseReserves, quoteReserves);
const d_1 = JSBI.subtract(d_0, JSBI.divide(JSBI.multiply(poolTokenAmount.raw, d_0), exchange.lpTotalSupply.raw));
const new_y = computeY(ampFactor, quoteReserves, d_1);
// expected_base_amount = swap_base_amount * d_1 / d_0 - new_y;
const expected_base_amount = JSBI.subtract(JSBI.divide(JSBI.multiply(baseReserves, d_1), d_0), new_y);
// expected_quote_amount = swap_quote_amount - swap_quote_amount * d_1 / d_0;
const expected_quote_amount = JSBI.subtract(quoteReserves, JSBI.divide(JSBI.multiply(quoteReserves, d_1), d_0));
// new_base_amount = swap_base_amount - expected_base_amount * fee / fee_denominator;
const new_base_amount = new Fraction(baseReserves.toString(), 1).subtract(normalizedTradeFee(fees, N_COINS, expected_base_amount));
// new_quote_amount = swap_quote_amount - expected_quote_amount * fee / fee_denominator;
const new_quote_amount = new Fraction(quoteReserves.toString(), 1).subtract(normalizedTradeFee(fees, N_COINS, expected_quote_amount));
const dy = new_base_amount.subtract(computeY(ampFactor, JSBI.BigInt(new_quote_amount.toFixed(0)), d_1).toString());
const dy_0 = JSBI.subtract(baseReserves, new_y);
// lp fees
const swapFee = new Fraction(dy_0.toString(), 1).subtract(dy);
const withdrawFee = dy.multiply(fees.withdraw.asFraction);
// admin fees
const adminSwapFee = swapFee.multiply(fees.admin.asFraction);
// final LP fees
const lpSwapFee = swapFee.subtract(adminSwapFee);
// final withdraw amount
const withdrawAmount = dy.subtract(withdrawFee).subtract(swapFee);
// final quantities
const quantities = {
withdrawAmount,
withdrawAmountBeforeFees: dy,
swapFee,
withdrawFee,
lpSwapFee,
adminSwapFee,
};
return mapValues(quantities, (q) => new TokenAmount(withdrawToken, q.toFixed(0)));
};
/**
* Compute normalized fee for symmetric/asymmetric deposits/withdraws
*/
export const normalizedTradeFee = ({ trade }, n_coins, amount) => {
const adjustedTradeFee = new Fraction(n_coins, JSBI.multiply(JSBI.subtract(n_coins, ONE), JSBI.BigInt(4)));
return new Fraction(amount, 1).multiply(trade).multiply(adjustedTradeFee);
};
export const calculateEstimatedWithdrawAmount = ({ poolTokenAmount, reserves, fees, lpTotalSupply, }) => {
if (lpTotalSupply.equalTo(0)) {
const zero = reserves.map((r) => new TokenAmount(r.token, ZERO));
return {
withdrawAmounts: zero,
withdrawAmountsBeforeFees: zero,
fees: zero,
};
}
const share = poolTokenAmount.divide(lpTotalSupply);
const withdrawAmounts = reserves.map((amount) => {
const baseAmount = share.multiply(normalizeAmount(amount));
const fee = baseAmount.multiply(fees.withdraw.asFraction);
return [
new TokenAmount(amount.token, JSBI.BigInt(baseAmount.subtract(fee).toFixed(0))),
{
beforeFees: JSBI.BigInt(baseAmount.toFixed(0)),
fee: JSBI.BigInt(fee.toFixed(0)),
},
];
});
return {
withdrawAmountsBeforeFees: withdrawAmounts.map(([amt, { beforeFees }]) => denormalizeAmount(new TokenAmount(amt.token, beforeFees))),
withdrawAmounts: [
denormalizeAmount(withdrawAmounts[0][0]),
denormalizeAmount(withdrawAmounts[1][0]),
],
fees: withdrawAmounts.map(([amt, { fee }]) => denormalizeAmount(new TokenAmount(amt.token, fee))),
};
};
/**
* Calculate the estimated amount of LP tokens minted after a deposit.
* @param exchange
* @param depositAmountA
* @param depositAmountB
* @returns
*/
export const calculateEstimatedMintAmount = (exchange, depositAmountA, depositAmountB) => {
const normalizedDepositAmountA = normalizeAmount(new TokenAmount(exchange.reserves[0].token, depositAmountA));
const normalizedDepositAmountB = normalizeAmount(new TokenAmount(exchange.reserves[1].token, depositAmountB));
if (JSBI.equal(depositAmountA, ZERO) && JSBI.equal(depositAmountB, ZERO)) {
const zero = new TokenAmount(exchange.lpTotalSupply.token, ZERO);
return {
mintAmountBeforeFees: zero,
mintAmount: zero,
fees: zero,
};
}
const amp = exchange.ampFactor;
const [reserveA, reserveB] = exchange.reserves;
const d0 = computeD(amp, normalizeAmount(reserveA), normalizeAmount(reserveB));
const d1 = computeD(amp, JSBI.add(normalizeAmount(reserveA), normalizedDepositAmountA), JSBI.add(normalizeAmount(reserveB), normalizedDepositAmountB));
if (JSBI.lessThan(d1, d0)) {
throw new Error("New D cannot be less than previous D");
}
const oldBalances = exchange.reserves.map((r) => normalizeAmount(r));
const newBalances = [
JSBI.add(normalizeAmount(reserveA), normalizedDepositAmountA),
JSBI.add(normalizeAmount(reserveB), normalizedDepositAmountB),
];
const adjustedBalances = newBalances.map((newBalance, i) => {
const oldBalance = oldBalances[i];
const idealBalance = new Fraction(d1, d0).multiply(oldBalance);
const difference = idealBalance.subtract(newBalance);
const diffAbs = difference.greaterThan(0)
? difference
: difference.multiply(-1);
const fee = normalizedTradeFee(exchange.fees, N_COINS, JSBI.BigInt(diffAbs.toFixed(0)));
return JSBI.subtract(newBalance, JSBI.BigInt(fee.toFixed(0)));
});
const d2 = computeD(amp, adjustedBalances[0], adjustedBalances[1]);
const lpSupply = exchange.lpTotalSupply;
const mintAmountRaw = JSBI.divide(JSBI.multiply(lpSupply.raw, JSBI.subtract(d2, d0)), d0);
const mintAmount = new TokenAmount(exchange.lpTotalSupply.token, mintAmountRaw);
const mintAmountRawBeforeFees = JSBI.divide(JSBI.multiply(lpSupply.raw, JSBI.subtract(d1, d0)), d0);
const fees = new TokenAmount(exchange.lpTotalSupply.token, JSBI.subtract(mintAmountRawBeforeFees, mintAmountRaw));
const mintAmountBeforeFees = new TokenAmount(exchange.lpTotalSupply.token, mintAmountRawBeforeFees);
return {
mintAmount,
mintAmountBeforeFees,
fees,
};
};
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