Fix deposit time logic when move quote token (#623)

Fix deposit time logic when move quote token
  - account current deposit time in to bucket as max(depositTime, bankruptcyTime + 1)
  - when setting the new deposit time take into account the current deposit time:  max(fromDepositTime, targetDepositTime)
  - unit test to assert all 3 scenarios:
      move from an older deposit to a newer one (newer deposit should preserve its time)
      move from a newer deposit to an older one (old deposit time should be set to the newer deposit time)
      move into a bucket bankrupt (depositTime should be recorded as bankrupcyTime + 1)

src/libraries/external/LenderActions.sol

@@ -44,6 +44,7 @@ library LenderActions {
  uint256 fromBucketRemainingDeposit; // Amount of scaled deposit remaining in from bucket after move.
  uint256 toBucketPrice; // [WAD] Price of the bucket to move amount to.
  uint256 toBucketBankruptcyTime; // Time the bucket to move amount to was marked as insolvent.
+ uint256 toBucketDepositTime; // Time of lender deposit in the bucket to move amount to.
  uint256 toBucketUnscaledDeposit; // Amount of unscaled deposit in to bucket.
  uint256 toBucketDeposit; // Amount of scaled deposit in to bucket.
  uint256 toBucketScale; // Scale deposit of to bucket.
@@ -295,13 +296,19 @@ library LenderActions {
  // update lender and bucket LPs balance in target bucket
  Lender storage toBucketLender = toBucket.lenders[msg.sender];
 
- if (vars.toBucketBankruptcyTime >= toBucketLender.depositTime) {
+ vars.toBucketDepositTime = toBucketLender.depositTime;
+ if (vars.toBucketBankruptcyTime >= vars.toBucketDepositTime) {
+ // bucket is bankrupt and deposit was done before bankruptcy time, reset lender lp amount
  toBucketLender.lps = toBucketLPs_;
+
+ // set deposit time of the lender's to bucket as bucket's last bankruptcy timestamp + 1 so deposit won't get invalidated
+ vars.toBucketDepositTime = vars.toBucketBankruptcyTime + 1;
  } else {
  toBucketLender.lps += toBucketLPs_;
  }
- // set deposit time to the greater of the lender's from bucket and the target bucket's last bankruptcy timestamp + 1 so deposit won't get invalidated
- toBucketLender.depositTime = Maths.max(vars.fromBucketDepositTime, vars.toBucketBankruptcyTime + 1);
+
+ // set deposit time to the greater of the lender's from bucket and the target bucket
+ toBucketLender.depositTime = Maths.max(vars.fromBucketDepositTime, vars.toBucketDepositTime);
 
  // update bucket LPs balance
  toBucket.lps += toBucketLPs_;

tests/forge/ERC20Pool/ERC20PoolLiquidationsSettle.t.sol

@@ -804,8 +804,17 @@ contract ERC20PoolLiquidationsSettleTest is ERC20HelperContract {
  // all operations should work if not in same block
  skip(1 hours);
 
- _pool.addQuoteToken(100 * 1e18, _i9_91, block.timestamp + 1 minutes);
+ // move quote token in a bankrupt bucket should set deposit time to time of bankruptcy + 1 to prevent losing deposit
  _pool.moveQuoteToken(10 * 1e18, _i9_52, _i9_91, block.timestamp + 1 minutes);
+ (, , uint256 bankruptcyTime, , ) = _pool.bucketInfo(_i9_91);
+ _assertLenderLpBalance({
+ lender: _lender1,
+ index: _i9_91,
+ lpBalance: 10 * 1e18,
+ depositTime: bankruptcyTime + 1
+ });
+
+ _pool.addQuoteToken(100 * 1e18, _i9_91, block.timestamp + 1 minutes);
  ERC20Pool(address(_pool)).addCollateral(4 * 1e18, _i9_91, block.timestamp + 1 minutes);
 
  _assertLenderLpBalance({

tests/forge/ERC20Pool/ERC20PoolQuoteToken.t.sol

@@ -918,6 +918,84 @@ contract ERC20PoolQuoteTokenTest is ERC20HelperContract {
  });
  }
 
+ function testPoolMoveQuoteTokenWithDifferentTime() external tearDown {
+ _addLiquidity({
+ from: _lender,
+ amount: 40_000 * 1e18,
+ index: 2549,
+ lpAward: 40_000 * 1e18,
+ newLup: MAX_PRICE
+ });
+
+ skip(7 days);
+ _addLiquidity({
+ from: _lender,
+ amount: 10_000 * 1e18,
+ index: 2550,
+ lpAward: 10_000 * 1e18,
+ newLup: MAX_PRICE
+ });
+
+ _assertLenderLpBalance({
+ lender: _lender,
+ index: 2549,
+ lpBalance: 40_000 * 1e18,
+ depositTime: _startTime
+ });
+ _assertLenderLpBalance({
+ lender: _lender,
+ index: 2550,
+ lpBalance: 10_000 * 1e18,
+ depositTime: _startTime + 7 days
+ });
+
+ // move liquidity from an older deposit to a newer one, deposit time should remain the newer one
+ _moveLiquidity({
+ from: _lender,
+ amount: 5_000 * 1e18,
+ fromIndex: 2549,
+ toIndex: 2550,
+ lpRedeemFrom: 5_000 * 1e18,
+ lpAwardTo: 5_000 * 1e18,
+ newLup: MAX_PRICE
+ });
+ _assertLenderLpBalance({
+ lender: _lender,
+ index: 2549,
+ lpBalance: 35_000 * 1e18,
+ depositTime: _startTime
+ });
+ _assertLenderLpBalance({
+ lender: _lender,
+ index: 2550,
+ lpBalance: 15_000 * 1e18,
+ depositTime: _startTime + 7 days
+ });
+
+ // move liquidity from a newer deposit to an older one, deposit time should be set to the newer one
+ _moveLiquidity({
+ from: _lender,
+ amount: 5_000 * 1e18,
+ fromIndex: 2550,
+ toIndex: 2549,
+ lpRedeemFrom: 5_000 * 1e18,
+ lpAwardTo: 5_000 * 1e18,
+ newLup: MAX_PRICE
+ });
+ _assertLenderLpBalance({
+ lender: _lender,
+ index: 2549,
+ lpBalance: 40_000 * 1e18,
+ depositTime: _startTime + 7 days
+ });
+ _assertLenderLpBalance({
+ lender: _lender,
+ index: 2550,
+ lpBalance: 10_000 * 1e18,
+ depositTime: _startTime + 7 days
+ });
+ }
+
  /**
  * @notice 1 lender, 1 bidder, 1 borrower tests reverts in moveQuoteToken.
  * Reverts: