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feat: adjust position for multiple lenders #2

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feat: adjust position for multiple lenders #2

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51 changes: 29 additions & 22 deletions contracts/OptStrategy.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,11 @@ contract OptStrategy is BaseStrategy {
uint256 public withdrawalThreshold = 1e12;
uint256 public constant SECONDSPERYEAR = 31556952;

// in bips - basis points, 100 = 1%
uint256 public marginApr = 1000;
// 10000 = 100%
uint256 public constant BASE_MARGIN_APR = 10000;

IGenericLender[] public lenders;
bool public externalOracle; // default is false
address public wantToEthOracle;
Expand Down Expand Up @@ -362,7 +367,7 @@ contract OptStrategy is BaseStrategy {

uint256 amountToFree = _profit.add(_debtPayment);
//we need to add outstanding to our profit
//dont need to do logic if there is nothiing to free
//dont need to do logic if there is nothing to free
if (amountToFree > 0 && looseAssets < amountToFree) {
//withdraw what we can withdraw
_withdrawSome(amountToFree.sub(looseAssets));
Expand Down Expand Up @@ -404,33 +409,35 @@ contract OptStrategy is BaseStrategy {

/*
* Key logic.
* The algorithm moves assets from lowest return to highest
* like a very slow idiots bubble sort
* we ignore debt outstanding for an easy life
* The algorithm moves assets from the lower return lenders to the higher in iterations.
* The adjustment loop stops when the lowest APR is the margin of the highest.
*/
function adjustPosition(uint256 _debtOutstanding) internal override {
_debtOutstanding; //ignored. we handle it in prepare return
//emergency exit is dealt with at beginning of harvest
if (emergencyExit) {
return;
}

//we just keep all money in want if we dont have any lenders
if (lenders.length == 0) {
//emergency exit is dealt with at beginning of harvest, cannot adjust 1 lender
if (emergencyExit || lenders.length < 2) {
return;
}

(uint256 lowest, uint256 lowestApr, uint256 highest, uint256 potential) = estimateAdjustPosition();

if (potential > lowestApr) {
//apr should go down after deposit so wont be withdrawing from self
lenders[lowest].withdrawAll();
}
// don't adjust the lender with the highest apy
uint256 maxNumberOfAdjustments = lenders.length - 1;
for (uint256 i = 0; i < maxNumberOfAdjustments; i++) {
// TODO: calculate estimated without _debtOutstanding
(uint256 lowest, uint256 lowestApr, uint256 highest, uint256 potential) = estimateAdjustPosition();
// potentialApr > lowestApr * (1 + margin in %)
if (potential > lowestApr.mul(BASE_MARGIN_APR.add(marginApr)).div(BASE_MARGIN_APR)) {
// new APR must be higher for at least a defined margin than the current APR
lenders[lowest].withdrawAll();
} else {
// quit adjustments when lowest APR is below the margin, others will be also
break;
}

uint256 bal = want.balanceOf(address(this));
if (bal > 0) {
want.safeTransfer(address(lenders[highest]), bal);
lenders[highest].deposit();
uint256 bal = want.balanceOf(address(this));
if (bal > _debtOutstanding) {
// TODO: deposit only amount above _debtOutstanding, after changing the estimate calculation
want.safeTransfer(address(lenders[highest]), bal);
lenders[highest].deposit();
}
}
}

Expand Down