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Merge pull request #102 from liquity/redemption_interest_2
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Add apply/mint interest for redemptions and leave redeemed Troves open
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@RickGriff
RickGriff authored Apr 10, 2024
2 parents 128a2cc + c59da4b commit 7e4b362
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Showing 7 changed files with 444 additions and 110 deletions.
109 changes: 62 additions & 47 deletions contracts/src/TroveManager.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -216,12 +216,22 @@ contract TroveManager is ERC721, LiquityBase, Ownable, CheckContract, ITroveMana
uint decayedBaseRate;
uint price;
uint totalBoldSupplyAtStart;
uint256 totalRedistDebtGains;
uint256 totalNewRecordedTroveDebts;
uint256 totalOldRecordedTroveDebts;
uint256 totalNewWeightedRecordedTroveDebts;
uint256 totalOldWeightedRecordedTroveDebts;
}


struct SingleRedemptionValues {
uint BoldLot;
uint ETHLot;
bool cancelledPartial;
uint256 redistDebtGain;
uint256 oldRecordedTroveDebt;
uint256 newRecordedTroveDebt;
uint256 oldWeightedRecordedTroveDebt;
uint256 newWeightedRecordedTroveDebt;
}

// --- Events ---
Expand Down Expand Up @@ -827,53 +837,46 @@ contract TroveManager is ERC721, LiquityBase, Ownable, CheckContract, ITroveMana
)
internal returns (SingleRedemptionValues memory singleRedemption)
{
singleRedemption.oldWeightedRecordedTroveDebt = getTroveWeightedRecordedDebt(_troveId);
singleRedemption.oldRecordedTroveDebt = Troves[_troveId].debt;

(, singleRedemption.redistDebtGain) = _getAndApplyRedistributionGains(_contractsCache.activePool, _contractsCache.defaultPool, _troveId);

// TODO: Gas. We apply accrued interest here, but could gas optimize this, since all-but-one Trove in the sequence will have their
// debt zero'd by redemption. However, gas optimization for redemption is not as critical as for borrower & SP ops.
uint256 entireTroveDebt = getTroveEntireDebt(_troveId);
_updateTroveDebt(_troveId, entireTroveDebt);

// Determine the remaining amount (lot) to be redeemed, capped by the entire debt of the Trove minus the liquidation reserve
singleRedemption.BoldLot = LiquityMath._min(_maxBoldamount, Troves[_troveId].debt - BOLD_GAS_COMPENSATION);
// TODO: should we leave gas compensation (and corresponding debt) untouched for zombie Troves? Currently it's not touched.
singleRedemption.BoldLot = LiquityMath._min(_maxBoldamount, entireTroveDebt - BOLD_GAS_COMPENSATION);

// Get the ETHLot of equivalent value in USD
singleRedemption.ETHLot = singleRedemption.BoldLot * DECIMAL_PRECISION / _price;

// Decrease the debt and collateral of the current Trove according to the Bold lot and corresponding ETH to send
uint newDebt = Troves[_troveId].debt - singleRedemption.BoldLot;
uint newColl = Troves[_troveId].coll - singleRedemption.ETHLot;

// TODO: zombi troves
if (newDebt == BOLD_GAS_COMPENSATION) {
// No debt left in the Trove (except for the liquidation reserve), therefore the trove gets closed
_removeStake(_troveId);
_closeTrove(_troveId, Status.closedByRedemption);
_redeemCloseTrove(_contractsCache, _troveId, BOLD_GAS_COMPENSATION, newColl);
emit TroveUpdated(_troveId, 0, 0, 0, TroveManagerOperation.redeemCollateral);

} else {
Troves[_troveId].debt = newDebt;
Troves[_troveId].coll = newColl;
_updateStakeAndTotalStakes(_troveId);
singleRedemption.newRecordedTroveDebt = entireTroveDebt - singleRedemption.BoldLot;
uint newColl = Troves[_troveId].coll - singleRedemption.ETHLot;

emit TroveUpdated(
_troveId,
newDebt, newColl,
Troves[_troveId].stake,
TroveManagerOperation.redeemCollateral
);
if (singleRedemption.newRecordedTroveDebt <= MIN_NET_DEBT) {
// TODO: tag it as a zombie Trove and remove from Sorted List
}
Troves[_troveId].debt = singleRedemption.newRecordedTroveDebt;
Troves[_troveId].coll = newColl;

return singleRedemption;
}
singleRedemption.newWeightedRecordedTroveDebt = getTroveWeightedRecordedDebt(_troveId);

/*
* Called when a full redemption occurs, and closes the trove.
* The redeemer swaps (debt - liquidation reserve) Bold for (debt - liquidation reserve) worth of ETH, so the Bold liquidation reserve left corresponds to the remaining debt.
* In order to close the trove, the Bold liquidation reserve is burned, and the corresponding debt is removed from the active pool.
* The debt recorded on the trove's struct is zero'd elswhere, in _closeTrove.
* Any surplus ETH left in the trove, is sent to the Coll surplus pool, and can be later claimed by the borrower.
*/
function _redeemCloseTrove(ContractsCache memory _contractsCache, uint256 _troveId, uint _bold, uint _ETH) internal {
_contractsCache.boldToken.burn(gasPoolAddress, _bold);
// TODO: Gas optimize? We update totalStakes N times for a sequence of N Trovres(!).
_updateStakeAndTotalStakes(_troveId);

emit TroveUpdated(
_troveId,
singleRedemption.newRecordedTroveDebt, newColl,
Troves[_troveId].stake,
TroveManagerOperation.redeemCollateral
);

// send ETH from Active Pool to CollSurplus Pool
_contractsCache.collSurplusPool.accountSurplus(_troveId, _ETH);
_contractsCache.activePool.sendETH(address(_contractsCache.collSurplusPool), _ETH);
return singleRedemption;
}

/* Send _boldamount Bold to the system and redeem the corresponding amount of collateral from as many Troves as are needed to fill the redemption
Expand Down Expand Up @@ -935,31 +938,36 @@ contract TroveManager is ERC721, LiquityBase, Ownable, CheckContract, ITroveMana
if (_maxIterations == 0) { _maxIterations = type(uint256).max; }
while (currentTroveId != 0 && totals.remainingBold > 0 && _maxIterations > 0) {
_maxIterations--;
// Save the uint256 of the Trove preceding the current one, before potentially modifying the list
// Save the uint256 of the Trove preceding the current one
uint256 nextUserToCheck = contractsCache.sortedTroves.getPrev(currentTroveId);
// Skip if ICR < 100%, to make sure that redemptions always improve the CR of hit Troves
if (getCurrentICR(currentTroveId, totals.price) < _100pct) {
currentTroveId = nextUserToCheck;
continue;
}

_getAndApplyRedistributionGains(contractsCache.activePool, contractsCache.defaultPool, currentTroveId);

SingleRedemptionValues memory singleRedemption = _redeemCollateralFromTrove(
contractsCache,
currentTroveId,
totals.remainingBold,
totals.price
);

if (singleRedemption.cancelledPartial) break; // Partial redemption was cancelled (out-of-date hint, or new net debt < minimum), therefore we could not redeem from the last Trove


totals.totalBoldToRedeem = totals.totalBoldToRedeem + singleRedemption.BoldLot;
totals.totalETHDrawn = totals.totalETHDrawn + singleRedemption.ETHLot;
totals.totalRedistDebtGains = totals.totalRedistDebtGains + singleRedemption.redistDebtGain;
// For recorded and weighted recorded debt totals, we need to capture the increases and decreases,
// since the net debt change for a given Trove could be positive or negative: redemptions decrease a Trove's recorded
// (and weighted recorded) debt, but the accrued interest increases it.
totals.totalNewRecordedTroveDebts = totals.totalNewRecordedTroveDebts + singleRedemption.newRecordedTroveDebt;
totals.totalOldRecordedTroveDebts = totals.totalOldRecordedTroveDebts + singleRedemption.oldRecordedTroveDebt;
totals.totalNewWeightedRecordedTroveDebts = totals.totalNewWeightedRecordedTroveDebts + singleRedemption.newWeightedRecordedTroveDebt;
totals.totalOldWeightedRecordedTroveDebts = totals.totalOldWeightedRecordedTroveDebts + singleRedemption.oldWeightedRecordedTroveDebt;

totals.totalETHDrawn = totals.totalETHDrawn + singleRedemption.ETHLot;
totals.remainingBold = totals.remainingBold - singleRedemption.BoldLot;
currentTroveId = nextUserToCheck;
}

require(totals.totalETHDrawn > 0, "TroveManager: Unable to redeem any amount");

// Decay the baseRate due to time passed, and then increase it according to the size of this redemption.
Expand All @@ -976,10 +984,17 @@ contract TroveManager is ERC721, LiquityBase, Ownable, CheckContract, ITroveMana

emit Redemption(_boldamount, totals.totalBoldToRedeem, totals.totalETHDrawn, totals.ETHFee);

activePool.mintAggInterest(
totals.totalRedistDebtGains,
totals.totalBoldToRedeem,
totals.totalNewRecordedTroveDebts,
totals.totalOldRecordedTroveDebts,
totals.totalNewWeightedRecordedTroveDebts,
totals.totalOldWeightedRecordedTroveDebts
);

// Burn the total Bold that is cancelled with debt, and send the redeemed ETH to msg.sender
contractsCache.boldToken.burn(msg.sender, totals.totalBoldToRedeem);
// Update Active Pool Bold, and send ETH to account
contractsCache.activePool.decreaseRecordedDebtSum(totals.totalBoldToRedeem);
contractsCache.activePool.sendETH(msg.sender, totals.ETHToSendToRedeemer);
}

Expand Down Expand Up @@ -1108,7 +1123,7 @@ contract TroveManager is ERC721, LiquityBase, Ownable, CheckContract, ITroveMana
entireColl = recordedColl + pendingETHReward;
}

function getTroveEntireDebt(uint256 _troveId) external view returns (uint256) {
function getTroveEntireDebt(uint256 _troveId) public view returns (uint256) {
(uint256 entireTroveDebt, , , , ) = getEntireDebtAndColl(_troveId);
return entireTroveDebt;
}
Expand Down
17 changes: 17 additions & 0 deletions contracts/src/test/TestContracts/BaseTest.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -56,24 +56,35 @@ contract BaseTest is Test {
uint256 A;
uint256 B;
uint256 C;
uint256 D;
}

struct TroveIDs {
uint256 A;
uint256 B;
uint256 C;
uint256 D;
}

struct TroveCollAmounts {
uint256 A;
uint256 B;
uint256 C;
uint256 D;
}

struct TroveInterestRates {
uint256 A;
uint256 B;
uint256 C;
uint256 D;
}

struct TroveAccruedInterests {
uint256 A;
uint256 B;
uint256 C;
uint256 D;
}

// --- functions ---
Expand Down Expand Up @@ -226,6 +237,12 @@ contract BaseTest is Test {
vm.stopPrank();
}


function redeem(address _from, uint256 _boldAmount) public {
vm.startPrank(_from);
troveManager.redeemCollateral(_boldAmount, MAX_UINT256, 1e18);
vm.stopPrank();
}
function logContractAddresses() public view {
console.log("ActivePool addr: ", address(activePool));
console.log("BorrowerOps addr: ", address(borrowerOperations));
Expand Down
29 changes: 29 additions & 0 deletions contracts/src/test/TestContracts/DevTestSetup.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -153,4 +153,33 @@ contract DevTestSetup is BaseTest {

return (ATroveId, BTroveId, CTroveId, DTroveId);
}

function _setupForRedemption() public returns (uint256, uint256, TroveIDs memory) {
TroveIDs memory troveIDs;

priceFeed.setPrice(2000e18);

uint256 interestRate_A = 10e16;
uint256 interestRate_B = 20e16;
uint256 interestRate_C = 30e16;
uint256 interestRate_D = 40e16;
uint256 coll = 20 ether;
uint256 debtRequest = 20000e18;
// Open in increasing order of interst rate
troveIDs.A = openTroveNoHints100pctMaxFee(A, coll, debtRequest, interestRate_A);
troveIDs.B = openTroveNoHints100pctMaxFee(B, coll, debtRequest, interestRate_B);
troveIDs.C = openTroveNoHints100pctMaxFee(C, coll, debtRequest, interestRate_C);
troveIDs.D = openTroveNoHints100pctMaxFee(D, coll, debtRequest, interestRate_D);

// fast-forward to pass bootstrap phase
vm.warp(block.timestamp + 14 days);

// A, B, C, D transfer all their Bold to E
transferBold(A, E, boldToken.balanceOf(A));
transferBold(B, E, boldToken.balanceOf(B));
transferBold(C, E, boldToken.balanceOf(C));
transferBold(D, E, boldToken.balanceOf(D));

return (coll, debtRequest, troveIDs);
}
}
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