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fix: NO full interest on partially repaid extensions #61

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Sep 15, 2023
Merged

fix: NO full interest on partially repaid extensions #61

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29 changes: 14 additions & 15 deletions src/Clearinghouse.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -186,14 +186,15 @@ contract Clearinghouse is Policy, RolesConsumer, CoolerCallback {
if (loan.lender != address(this)) revert NotLender();

uint256 interestNew;
if (loan.interestDue == 0) {
uint256 interestBase = interestForLoan(loan.principal, loan.request.duration);
if (loan.interestDue != interestBase) {
// If interest has manually been repaid, user only pays for the subsequent extensions.
interestNew = interestForLoan(loan.principal, loan.request.duration * (times_ - 1));
interestNew = interestBase * (times_ - 1) + loan.interestDue;
// Receivables need to be updated.
interestReceivables += interestForLoan(loan.principal, loan.request.duration);
interestReceivables += interestBase - loan.interestDue;
} else {
// Otherwise, user pays for all the extensions.
interestNew = interestForLoan(loan.principal, loan.request.duration * times_);
interestNew = interestBase * times_;
}
// Transfer in extension interest from the caller.
dai.transferFrom(msg.sender, loan.recipient, interestNew);
Expand Down Expand Up @@ -267,10 +268,8 @@ contract Clearinghouse is Policy, RolesConsumer, CoolerCallback {

// Reward keeper.
gohm.transfer(msg.sender, keeperRewards);

// Unstake and burn the collateral of the defaulted loans.
gohm.approve(address(staking), totalCollateral - keeperRewards);
MINTR.burnOhm(address(this), staking.unstake(address(this), totalCollateral - keeperRewards, false, false));
// Burn the outstanding collateral of defaulted loans.
burn();
}

// --- CALLBACKS -----------------------------------------------------
Expand Down Expand Up @@ -315,6 +314,10 @@ contract Clearinghouse is Policy, RolesConsumer, CoolerCallback {
if (fundTime > block.timestamp) return false;
fundTime += FUND_CADENCE;

// Sweep DAI into DSR if necessary.
uint256 idle = dai.balanceOf(address(this));
if (idle != 0) _sweepIntoDSR(idle);

uint256 daiBalance = sdai.maxWithdraw(address(this));
uint256 outstandingDebt = TRSRY.reserveDebt(dai, address(this));
// Rebalance funds on hand with treasury's reserves.
Expand All @@ -334,10 +337,6 @@ contract Clearinghouse is Policy, RolesConsumer, CoolerCallback {
TRSRY.increaseWithdrawApproval(address(this), sdai, sdaiAmount);
TRSRY.withdrawReserves(address(this), sdai, sdaiAmount);

// Sweep DAI into DSR if necessary.
uint256 idle = dai.balanceOf(address(this));
if (idle != 0) _sweepIntoDSR(idle);

// Log the event.
emit Rebalance(false, fundAmount);

Expand Down Expand Up @@ -408,10 +407,10 @@ contract Clearinghouse is Policy, RolesConsumer, CoolerCallback {
emit Defund(address(token_), amount_);
}

/// @notice Burn any gOHM defaulted using the Cooler instead of the Clearinghouse.
function burn() external {
/// @notice Public function to burn gOHM.
/// @dev Can be used to burn any gOHM defaulted using the Cooler instead of the Clearinghouse.
function burn() public {
uint256 gohmBalance = gohm.balanceOf(address(this));

// Unstake and burn gOHM holdings.
gohm.approve(address(staking), gohmBalance);
MINTR.burnOhm(address(this), staking.unstake(address(this), gohmBalance, false, false));
Expand Down
18 changes: 11 additions & 7 deletions src/test/Clearinghouse.t.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -325,7 +325,7 @@ contract ClearinghouseTest is Test {
uint256 initInterest = clearinghouse.interestReceivables();
uint256 initPrincipal = clearinghouse.principalReceivables();
// Approve the interest of the extensions
uint256 interestOwed = clearinghouse.interestForLoan(initLoan.principal, initLoan.request.duration * times_);
uint256 interestOwed = clearinghouse.interestForLoan(initLoan.principal, initLoan.request.duration) * times_;
dai.approve(address(clearinghouse), interestOwed);
// Extend loan
clearinghouse.extendLoan(cooler, loanID, times_);
Expand All @@ -346,7 +346,7 @@ contract ClearinghouseTest is Test {
assertEq(clearinghouse.principalReceivables(), initPrincipal);
}

function testFuzz_extendLoan_withPriorRepayment(uint256 loanAmount_, uint256 elapsed_, uint8 times_) public {
function testFuzz_extendLoan_withPriorRepayment(uint256 loanAmount_, uint256 repay_, uint256 elapsed_, uint8 times_) public {
// Loan amount cannot exceed Clearinghouse funding
loanAmount_ = bound(loanAmount_, 1e10, clearinghouse.FUND_AMOUNT());
elapsed_ = bound(elapsed_, 0, clearinghouse.DURATION());
Expand All @@ -358,18 +358,22 @@ contract ClearinghouseTest is Test {
// Move forward without defaulting
_skip(elapsed_);

vm.startPrank(user);
dai.approve(address(cooler), initLoan.interestDue);
// Bound repayment
repay_ = bound(elapsed_, 1, initLoan.interestDue);

// Repay interest of the first extension manually
cooler.repayLoan(loanID, initLoan.interestDue);
vm.startPrank(user);
dai.approve(address(cooler), repay_);
cooler.repayLoan(loanID, repay_);

// Cache DAI balance and interest after repayment
Cooler.Loan memory repaidLoan = cooler.getLoan(loanID);
uint256 initDaiUser = dai.balanceOf(user);
uint256 initDaiCH = dai.balanceOf(address(clearinghouse));
uint256 initInterest = clearinghouse.interestReceivables();
uint256 initPrincipal = clearinghouse.principalReceivables();
// Approve the interest of the followup extensions
uint256 interestOwed = clearinghouse.interestForLoan(initLoan.principal, initLoan.request.duration * (times_ - 1));
uint256 interestOwed = clearinghouse.interestForLoan(initLoan.principal, initLoan.request.duration) * (times_ - 1) + repaidLoan.interestDue;
dai.approve(address(clearinghouse), interestOwed);

// Extend loan
Expand All @@ -387,7 +391,7 @@ contract ClearinghouseTest is Test {
assertEq(extendedLoan.collateral, initLoan.collateral, "collateral");
assertEq(extendedLoan.expiry, initLoan.expiry + initLoan.request.duration * times_, "expiry");
// Check: clearinghouse storage
assertEq(clearinghouse.interestReceivables(), initInterest + extendedLoan.interestDue);
assertEq(clearinghouse.interestReceivables(), initInterest + extendedLoan.interestDue - repaidLoan.interestDue);
assertEq(clearinghouse.principalReceivables(), initPrincipal);
}

Expand Down