Pooled Credit Lines

Pooled credit lines allow a single borrower to raise capital from multiple lenders in the form of a credit line. Pooled credit lines combine elements of credit lines and pools to create more generalized debt offerings.
Purpose
Functions of pooled credit lines have been spread across two contracts: PooledCreditLine.sol and LenderPool.sol. This divide has been roughly to ensure PooledCreditLine only deals with functions pertinent to the borrower, while LenderPool contains all the functions related to the lenders.
Wherever necessary, executing a function in one contract (PooledCreditLine/LenderPool) will trigger an accompanying function in the other contract to change the state of some of the variables stored in LenderPool.sol
Here's an example lifecycle of a pooled credit line:
Pooled credit line example
For a general overview of pooled credit lines please visit Pooled Credit Lines.
Functionality
Creating a pooled credit line request
The first step towards creating a pooled credit line request is calling the request() function in PooledCreditLine.sol. The function checks if the arguments supplied pass necessary checks. This function further calls an internal function (createRequest()) to store the parameters of the raise, and another function (_notifyRequest()) to pass on the details of the loan to the LenderPool contract.
Function
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function request(Request calldata _request) 
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    external returns (uint256) 
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Restrictions
Borrower must be verified by the borrowerVerifier selected by them
Arguments of the loan must pass range checks in the contract
Arguments
_request: A struct containing all the parameters necessary to create the loan request
Starting the pooled credit line
 For a pooled credit line to go active, either:
the total amount lent must be equal to the borrowLimit
at the end of the collection period, the total amount lent (after subtracting the starting fee) must be greater than or equal to the minBorrowAmount
In the first case, the pooled credit line status is changed to the ACTIVE stage in the lend() call that leads to the total amount meeting borrowLimit. In the second case, the start() function needs to be called separately after the end of the collection period for the pool to turn to ACTIVE stage.
Relevant functions
1. LenderPool.start()
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function start(uint256 _id, address _to) external nonReentrant 
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Restrictions
Can only be called after the end of the collection period
Arguments
_id: identifier of the pooled credit line for which start() is being called
_to: receiver address for the start fee
2. PooledCreditLine.accept()
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function accept(uint256 _id, uint256 _amount) 
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    external override onlyLenderPool 
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Restrictions
Can only be called by LenderPool contract
Arguments
_id: identifier of the pooled credit line which is being accepted
_amount: final amount of borrowAsset that will be available for the borrower to borrow
Supplying liquidity into a pooled credit line
Lenders can supply liquidity into a pooled credit line request by calling the lend() function. This can only be done during the collection stage, and requires the lender to be verified by the lenderVerifier chosen by the borrower.
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function lend(uint256 _id, uint256 _amount) 
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    external nonReentrant 
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Arguments
_id: identifier of the pooled credit line which is being accepted
_amount: amount that the lender wishes to lend
Cancelling a pooled credit line
A pooled credit line can be cancelled by the borrower as long as it is still in the collection stage.
Relevant Functions
1. PooledCreditLine.cancelRequest
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function cancelRequest(uint256 _id) external onlyCreditLineBorrower(_id) 
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Restrictions
Requires the pooled credit line to be in the REQUESTED state
Requires that the pooled credit line still be in the collection stage
Can only be called by the borrower of the pooled credit line
Arguments
_id: identifier of the credit line to be cancelled
2. LenderPool.requestCancelled
The requestCancelled function is called by cancelRequest function to delete the startTime variable so that lending into the pooled credit line is effectively paused. Existing lenders can then start withdrawing their deposits since the pooled credit line status is changed to CANCELLED.
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function requestCancelled(uint256 _id) external onlyPooledCreditLine 
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Restrictions
Can only be called by the PooledCreditLine contract
Arguments
_id: identifier for the pooled credit line
Borrowing from pooled credit line
The borrower of the pooled credit line can begin borrowing once the status is changed to ACTIVE and the current timestamp has passed the start time of the loan. Borrowing a given amount requires the borrower to have sufficient collateral such that their new collateral ratio (after the amount is borrowed) must be greater than or equal to the loan's ideal collateral ratio. In case the above condition does not hold true the operation would fail
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function borrow(uint256 _id, uint256 _amount) 
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    external nonReentrant onlyCreditLineBorrower(_id) 
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Restrictions
Only the borrower of the pooled credit line can call this function
The pooled credit line must be in the ACTIVE state
The timestamp must be grater than or equal to the start time of the loan
Arguments
_id: identifier of the pooled credit line
_amount: amount that the borrower wishes to borrow
Repaying debt
The borrower can start repaying their debt when they wish to. A fixed repayment schedule has not be implemented in the contracts to allow for sufficient flexibility in case the borrower cannot make a timely repayment for some reason. Typically we would expect borrowers to come up with a soft repayment schedule with the lenders off-chain which would include conditions for late repayments. While this allows for sufficient flexibility, failure to stick to this repayment schedule would hurt the borrower's future borrowing prospects, thus incentivizing borrowers to maintain a healthy repayment schedule.
Note that borrowers only accrue interests on the principal they're actively borrowing, not the entire pool. This is because any unused capital is redeployed onto the borrowAssetStrategy to earn passive yield. Repayments first count towards repayment of any accrued interest. Repayments count towards repayment of the principal only once all interests are paid.
While there are no fixed repayment schedules, it is enforced that all debt must be repaid by the end of credit line. Failure to do so puts the borrower in a grace period, during which they continue to accrue interest, at an interest rate equal to borrowRate + gracePenaltyRate .
Relevant Functions
1. PooledCreditLine.repay
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function repay(uint256 _id, uint256 _amount) 
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    external nonReentrant 
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Arguments
_id: identifier for the pooled credit line for which amount is being repaid
_amount: amount that the msg.sender wishes to repay
2. LenderPool.repaid
Function called by PooledCreditLine.repay() to update relevant state vars in the LenderPool contract
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function repaid(
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        uint256 _id,
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        uint256 _sharesRepaid,
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        uint256 _interestShares
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    ) external onlyPooledCreditLine nonReentrant 
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Restrictions
Can only be called by the PooledCreditLine contract
Arguments
_id: identifier for the pooled credit line for which amount is being repaid
_amount: amount that was repaid in terms of the LP tokens of the savings strategy chosen
_interestShares: Number of shares that counted towards repaying the interest
Withdrawing interest
Lenders have the power to withdraw interests throughout the period of the loan. Interests are generated by two sources:
Borrower repays interest accrued
Deposits on the yield strategy (borrowAssetStrategy) earns interest
Note that interests repaid by borrower are discrete in time, while deposits in the borrowAssetStrategy earn interest continuously.
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function withdrawInterest(uint256 _id, address _lender) 
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    external nonReentrant 
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Arguments
_id: identifier for the pooled credit line 
_lender: address of lender whose interests are being withdrawn
Withdrawing principal as lender
This function is used to remove the entire debt accumulated in the contract
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function withdrawLiquidity(uint256 _id) external nonReentrant 
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Arguments
_id: identifier for the pooled credit line
Adding collateral
Sufficient collateral must be deposited for the borrow() to be active
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function depositCollateral(
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        uint256 _id,
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        uint256 _amount,
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        bool _fromSavingsAccount
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    ) external nonReentrant 
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Arguments:
`_id`: identifier for the pooled credit line
_amount: the amount that the borrower wants to supply into the pooled credit line
_fromtSavingsAccount: if true, funds are transferred from the msg.sender's savings account. If false, tokens are directly transferred from the user's wallet accrea
Withdrawing collateral
Collateral can be withdrawn by the borrower as long as the new collateral ratio (collateral ratio if _amount is withdrawn), is greater than or equal to the ideal collateral ratio.
Note that withdawCollateral() does not allow for lenders to withdraw excess collateral during the EXPIRED period.
Funcitions
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function withdrawCollateral(
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        uint256 _id,
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        uint256 _amount,
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        bool _toSavingsAccount
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    ) external nonReentrant onlyCreditLineBorrower(_id) 
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Restrictions
Can only be called by the poolcreditline borrower
Arguments
_id: identifier for the pooled credit line
_amount: amount of collateral that the msg.sender wants to withdaw
_to_SavingsAccount: if true, funds are transferred to the borrower's SavingsAccount account. If false, funds are directly transferred to the lender's wallet 
2. PooledCreditLine.withdawCollateral
The below withdrawCollateral() function is fairly similar to the previous one, except it transfers the entire collateral that the msg.sender can withdraw rather than a part of it.
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function withdrawCollateral(uint256 _id, bool _toSavingsAccount) 
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    external nonReentrant onlyCreditLineBorrower(_id) 
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Restrictions
Only pooled credit line borrower can call
Arguments
_id: identifier of the pooled ctredit line
_to_SavingsAccount: if true, funds are transferred to the borrower's SavingsAccount account. If false, funds are directly transferred to the lender's wallet 
Liquidating a pooled credit line
Liquidation can occur under two conditions:
Borrower fails to repay debt by the end of the grace period
The credit line's collateral ratio falls below the ideal collateral ratio
Relevant Functions
1. LenderPool.liquidate
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function liquidate(uint256 _id, bool _withdraw) external nonReentrant 
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Restrictions
msg.sender must be a lender in the credit line
Arguments
_id: identifier of the pooled credit line
_withdraw: if true, the collateral amount that can be repossessed by the msg.sender is transferred to them. If false, they can claim it separately by calling withdrawLiquidation
2. PooledCreditLine.liquidate
Performs the checks necessary to ensure that the credit line can actually be liquidated. It also transfer the collateral to the LenderPool contract so that lenders can start withdrawing their share of the collateral.
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function liquidate(uint256 _id) 
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    external override nonReentrant 
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    onlyLenderPool returns (address, uint256) 
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Restrictions
Can only be called by the LenderPool contract
Arguments
_id: Pooled credit line identifier
Closing a pooled credit line
The borrower of the pooled credit line can close a loan at any time (given, the loan is ACTIVE) as long as the debt is 0. This is checked by ensuring that the active principal being borrowed is 0 (this is because principal is reduced only once all interests are repaid).
Function
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function close(uint256 _id) external onlyCreditLineBorrower(_id) 
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Restrictions
Only the borrower of the pooled credit line can call this function
Arguments
_id: identifier of the pooled credit line
​
Error codes
Error code
Error message
Function/modifier name
OCLB1
Only pooled credit line borrower can call this function
onlyCreditLineBorrower
OLP1
Only LenderPool contract can call this function
onlyLenderPool
ILB1
Borrow limit is out of range
_limitBorrowedInUSD
ILB2
Minimum borrow amount should be less than borrow limit
_limitBorrowedInUSD
ILB3
Minimum borrow amount should be greater than/equal to minimum borrow limit
_limitBorrowedInUSD
UBLL1
min should be less than max  or one of the limits must be 0
updateBorrowLimitLimits
UBLL2
New limits must be different from existing limits
updateBorrowLimitLimits
UICRL1
min should be less than max  or one of the limits must be 0
updateIdealCollateralRatioLimits
UICRL2
New limits must be different from existing limits
updateIdealCollateralRatioLimits
UBRL1
min should be less than max  or one of the limits must be 0
updateBorrowRateLimits
UBRL2
New limits must be different from existing limits
updateBorrowRateLimits
UCPL1
min should be less than max  or one of the limits must be 0
updateCollectionPeriodLimits
UCPL2
New limits must be different from existing limits
updateCollectionPeriodLimits
UDL1
min should be less than max  or one of the limits must be 0
updateDurationLimits
UDL2
New limits must be different from existing limits
updateDurationLimits
UDGPL1
min should be less than max  or one of the limits must be 0
updateDefaultGracePeriodLimits
UDGPL2
New limits must be different from existing limits
updateDefaultGracePeriodLimits
UGPRL1
min should be less than max  or one of the limits must be 0
updateGracePenaltyRateLimits
UGPRL2
New limits must be different from existing limits
updateGracePenaltyRateLimits
UPO1
New implementation cannot match the existing one
updatePriceOracle
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