Credit Lines

Credit lines allow unverified borrowers to access capital from lenders who trust them. Borrowers don't need to be verified to create credit lines, thus making it ideal for those who prefer to keep their identities private.
Purpose
The credit lines contract allows a single borrower and a single lender to set up a direct agreement for a line of credit with no specific end term. A credit line can be created by either party - a borrower can request a credit line from a lender, or a lender can offer a credit line to a borrower - however, it has to be accepted by the other party to be activated.
Capital for a credit line is directly sourced from the lender's savings account. To do this, lender's balance in every strategy is iterated upon and the required capital removed to fulfill the loan request (the order of iteration over the strategies is preset).
Roles
Admin
Assignment
by deploying the contract
gaining ownership from previous owner
Permissions
Can transfer ownership to another admin
Can update logic contract implementation addresses
Borrower
Assignment
by accepting a credit line offered by a lender
by requesting a credit line to a lender that gets accepted
Every active credit line has a borrower. A single address can be a borrower in multiple active credit lines
Permissions
Can request or accept a credit line
Can borrow from credit line
Can add/withdraw collateral, repay, or close the credit line
Lender
Assignment
by accepting a credit line requested by a borrower
by offering a credit line to a borrower that gets accepted
Every active credit line has a lender. A single address can be a lender in multiple active credit lines
Permissions
Can offer or accept a credit line request
Can liquidate the credit line. Will be the only liquidator if autoLiquidation is set to false
Can close the credit line
Liquidator
Assignment
If autoLiquidation is true, any one can act as liquidator by calling liquidate(), if set as false, only lender can be the liquidator
Permissions
Liquidator liquidates a credit line that is undercollateralized. Note that the liquidator roles are not set - anyone that calls the liquidate() function is technically assigned the liquidator rule for the credit line in question
Functionality
Creating a credit line request
The first step in establishing a credit line is creating a request. The request can either be created by a borrower or by a lender. Once the credit line request is created, it needs to be accepted by the recipient (the lender, in case the creator was the borrower, or vice versa) for the credit line to be activated. Every credit line is represented by an id which is simply the serial number of the credit line.
Function
function request(
        address _requestTo,
        uint256 _borrowLimit,
        uint256 _borrowRate,
        bool _autoLiquidation,
        uint256 _collateralRatio,
        address _borrowAsset,
        address _collateralAsset,
        bool _requestAsLender
    ) external returns (uint256) {
Approvals
None
Restrictions
Requires that the collateral and borrow asset chosen have a valid price feed
Arguments
_requestTo: address of the recipient. If msg.sender is the borrower, then _requestTo should be the lender's address, or vice versa
_borrowLimit: the maximum debt (principal+interest) that the borrower can have as part of the credit line. Once the limit is reached, the borrower cannot withdraw more capital from the credit line. Note that the borrower's actual debt can in fact exceed _borrowLimit because of accrual of interest. Including interest to calculate the max. debt applies soft pressure on the borrower to occasionally repay their debt since interest accrual slowly eats away their borrowing capacity
_borrowRate: simple interest rate that the borrower must provide
_autoLiquidation: If set as false only lender can liquidate the credit line. If set as true anyone can liquidate the credit line by calling the liquidate()
_collateralRatio: the ideal collateral ratio that the borrower must maintain for the credit line to be considered sufficiently collateralized. If the borrower's collateral ratio drops below they're liable for liquidation
_borrowAsset: asset the borrower wishes to borrow
_collateralAsset: asset the borrower will be putting up as collateral
_requestAsLender: If true msg.sender is the lender for the credit line, while _requestTo represents the borrower's address. The assignments are switched if this parameter is false
Accepting a credit line
Once a credit line is created, it needs to be accepted by the recipient for the credit line to be established. As soon as it is accepted, the borrower can start drawing credit from it.
Function
function accept(uint256 _id) external
Approvals
None
Restrictions
Only the recipient (_requestTo) can accept the credit line
Arguments
_id: The credit line identifier
Borrowing from a credit line
As soon as a credit line is activated, the borrower can start withdrawing capital from the credit line. This capital is withdrawn from the lender's savings account by iterating over the lender's balance in the supported savings strategies. The order of traversal within the strategy list is fixed at a protocol level.
Function
function borrow(uint256 _id, uint256 _amount) 
    external payable nonReentrant onlyCreditLineBorrower(_id) {
Approvals
None
Restrictions
The credit line identified by _id must be ACTIVE
msg.sender is the borrower of the said credit line
The borrower's total final debt be less than or equal to borrowLimit as defined by the credit line instance
Borrower's collateral ratio after the borrow must be greater than or equal to idealCollateralRatio as defined by the credit line instance
Arguments
_id:  unique identifier of the credit line instance
_amount: amount (denominated in borrowAsset) that the borrower wishes to withdraw
Repaying credit line debt
As the borrower accummulates debt, both due to principal borrowing as well as interest accrual on the principal, the borrower can repay the debt to replenish their borrowing limit. Note that there are no specified repayment plans or intervals. Additionally, calling the repay() function does not require msg.sender to be the borrower of the credit line instance. This crucially allows others to repay a borrower's debt as well.
Any amount repaid first counts towards repaying the interest. Prinicipal repayment occurs only if there are no outstanding interests. 
Function
function repay(
        uint256 _id,
        uint256 _amount,
        bool _fromSavingsAccount
    ) external payable nonReentrant {
Approvals
None
Restrictions
The credit line identified by _id must be ACTIVE
Lender of the credit line cannot repay the credit line
Arguments
_id: unique identifier of the credit line instance
_amount: amount msg.sender wishes to repay
_fromSavingsAccount: if true, _amount is withdrawn by traversing through the msg.sender's Savings Account on Sublime. If false, _amount is directly transferred from msg.sender's wallet
Depositing Collateral
Collateral deposits might be necessary depending on the terms of the credit line instance. If the borrower's collateral ratio falls below _collateralRatio set during the credit line creation, the borrower becomes liable for liquidation. Hence, regular replenishment of collateral might be necessary. Additionally, note that msg.sender does not have to be the borrower of the credit line instance. This allows the borrower to transfer the collateral required from a different wallet address than the one associated with the credit line instance.
Function
function depositCollateral(
        uint256 _id,
        uint256 _amount,
        address _strategy,
        bool _fromSavingsAccount
    ) external payable nonReentrant ifCreditLineExists(_id) {
Approvals
None
Restrictions
The credit line identified by _id must be ACTIVE
Arguments
_id: unique identifier of the credit line instance
_amount: amount msg.sender wishes to deposit
_strategy: the savings strategy to which _amount collateral should be deployed. Note that if _fromSavingsAccount is true, this argument remains unused - a direct transfer of LP tokens takes place so that the original strategy remains intact
_fromSavingsAccount: If true collateral is transferred from msg.sender's Sublime Savings Account. If false collateral is transferred directly from msg.sender's wallet
Withdrawing collateral
Borrower can withdraw collateral from a credit line instance, as long as the borrower's collateral ratio after the withdrawal is greater than or equal to the _collateralRatio as defined during the credit line instantiation.
Function
function withdrawCollateral(
        uint256 _id,
        uint256 _amount,
        bool _toSavingsAccount
    ) external nonReentrant onlyCreditLineBorrower(_id) {
Approvals
None
Restrictions
The credit line identified by _id must be ACTIVE
Borrower's collateral ratio due to the withdrawal cannot fall below the collateralRatio for the credit line instance
msg.sender must be the borrower of the credit line
Arguments
_id: unique identifier of the credit line instance
_amount: amount the msg.sender wishes to withdraw
_toSavingsAccount: If true, the collateral is withdrawn to the msg.sender's Sublime Savings Account through direct transfer of LP tokens. If false, collateral is withdrawn to the msg.sender address after conversion to base tokens
Liquidation
If the borrower's collateral ratio falls below _collateralRatio as defined during the credit line instantiation. This requires msg.sender to pay an amount equivalent to the value of the collateral denominated in the credit line's borrowAsset less the liquidation reward that is fixed at the protocol level. For example, if a credit line that is collateralized $1,000 WBTC is up for liquidation, and the borrowAsset is USDC, then the liquidator might have to repay $900 USDC ($100 WBTC is the liquidation reward).
Valid liquidators for a credit line are determined by the _autoLiquidate parameter set during credit line instantiation. If _autoLiquidate is set as false, only the lender of the credit line can call the liquidation function. If set as true, anyone can call liquidate the credit line instance by calling the liquidate() function. Collateral is transferred to the liquidator, while the amount repaid (if _autoLiquidate is true) by the liquidator is transferred to the lender's wallet address.
Furthermore, the entire collateral needs to be liquidated at once, ie, partial liquidations are not possible.
Function
function liquidate(uint256 _id, bool _toSavingsAccount) 
    external payable nonReentrant {
Approvals
None
Restrictions
The credit line identified by _id must be ACTIVE
The current collateral ratio of the credit line must be less than _collateralRatio set during instantiation
Arguments
_id: unique identifier of the credit line instance
_toSavingsAccount: If true, the collateral is withdrawn to the msg.sender's Sublime Savings Account through direct transfer of LP tokens. If false, collateral is withdrawn to the msg.sender address after conversion to base tokens (the collateralAsset)
Closing a credit line
An active credit line can be closed by either the borrower or the lender. Active debt by the borrower must be 0 for the credit line to be closed.
Function
function close(uint256 _id) external ifCreditLineExists(_id) {
Approvals
None
Restrictions
The credit line identified by _id must be ACTIVE
Total debt must be 0
Arguments
_id: unique identifier of the credit line instance
Flow
The typical flow is as follows: 
1.Borrower/lender requests/grants credit line to the lender/borrower 
2.Lender/borrower accepts the credit line. Allowance for credit line is set to allow withdrawals from the lender's credit line when the borrower wishes to withdraw
3.Borrower deposits collateral into the credit line's Savings Account 
4.Borrower withdraws amount from the credit line if their current total debt + amount <= borrowLimit 
5.Borrower can repay part of the credit line at any point 
6.In case the borrower's collateral ratio crosses the liquidation threshold, the borrower can be liquidated 
7.In case the current borrowed amount is 0, the credit line can be closed by the lender or the borrower
Simple interest is used to perform interest accruals. To perform all the required calculations, we keep track of
totalInterestRepaid - total amount repaid by the borrower 
principal - principal borrowed
interestAccruedTillPrincipalUpdate - interest accrued before last principle update.
lastPrincipleUpdateTime - Timestamp at which principle was last updated 
_interestSincePrincipalUpdate(temp) - interest accrued after a principal update.
Helpers
calculateBorrowableAmount
This function is used to calculateBorrowableAmount based on the collateral tokens for the credit line.
function calculateBorrowableAmount(uint256 _id) returns (uint256)
_id: The unique ID that represents the credit line
RETURN: The amount of tokens that can be borrowed
Note: The borrowableAmount depends on the price of the collateral and borrow tokens, so it might change with every block. So it is advisable to borrow a little less than the amount returned by the function to account for price fluctuations from the time of query. Ignore if the function is being called in the same block as the tx.
calculateCurrentDebt
This function is used to calculateCurrentDebt which includes principle and the interest accrued till that point.
function calculateCurrentDebt(uint256 _id) returns (uint256)
_id: The unique ID that represents the credit line
RETURN: The amount of debt till now
Note: currentDebt changes per block based on the time difference between blocks. So when trying to completely repay it is advised to repay a little higher than the value returned by the function to account for the difference in time between the query and the actual tx. Ignore if the query and repayment are done in same block.
calculateInterestAccrued
This function is used to calculate the interest accrued till the current block
function calculateInterestAccrued(uint256 _id) returns (uint256)
_id: The unique ID that represents the credit line
RETURN: The amount of interest accrued till now
Note: The interest accrued will change based on the block number it is queried at. So please account for any difference between the time of query and when it is used.
calculateCurrentCollateralRatio
This function is used to calculate the current collateral ratio of the credit line.
function calculateCurrentCollateralRatio(uint256 _id) returns (uint256)
_id: The unique ID that represents the credit line
RETURN: The collateral ratio at the time of query
Note: The collateral ratio depends on the price of collateral asset and borrow asset, hence can vary every block.
calculateTotalCollateralTokens
This function is used to calculate the current collateral tokens as they might change based on the strategy they are invested in.
function calculateTotalCollateralTokens(uint256 _id) returns (uint256)
_id: The unique ID that represents the credit line
RETURN: Total collateral tokens at the time of query
Note: Total collateral tokens depends on the strategy that is used and hence can change every block.
Error Codes
Error Code
Error Message
Function/Modifier name
CL1
Credit line does not exist
ifCreditLineExists
CL2
Only credit line Borrower can access
onlyCreditLineBorrower
CL3
Invalid Strategy
_updateDefaultStrategy
CL4
Protocol fee collector can't be 0 address
_updateProtocolFeeCollector
CL5
Strategy registry can't be 0 address
_updateStrategyRegistry
CL6
Reward fraction has to be less than 1
_updateLiquidatorRewardFraction
CL7
Function can only be called if credit line is ACTIVE or REQUESTED
calculateBorrowableAmount
CL8
Function cannot be called since credit line doesn't exist
updateinterestAccruedTillLastPrincipalUpdate
CL9
Borrow asset and collateral asset can't be the same
request
CL10
Price feed doesn't exist for the passed asset pair
request
CL11
Borrow limit is out of the allowed range
request
CL12
Borrow rate is out of the allowed range
request
CL13
Ideal collateral ratio is out of the allowed range
request
CL14
Borrower and lender cannot be the same address
request
CL15
Credit lines has already been accepted
accept
CL16
msg.sender is not valid
accept
CL17
Credit line is not active
depositCollateral
CL18
Lender cannot deposit collateral
depositCollateral
CL19
Lender cannot deposit collateral
_depositCollateral
CL20
ETH is not required for this operation
_depositCollateral
CL21
Credit line is not active
borrow
CL22
Requested amount cannot be withdrawn
borrow
CL23
Credit line is not active
repay
CL24
Lender address cannot repay
repay
CL25
ETH is not required for this operation
repay
CL26
msg.sender needs to be lender or borrower
close
CL27
Credit line is not active
close
CL28
Credit line cannot be closed since principal is non-zero
close
CL29
Credit line cannot be closed since interest is non-zero
close
CL30
msg.sender should be the borrower or lender
cancel
CL31
Credit line is not in the requested state
cancel
CL32
Collateral ratio cannot fall below the ideal collateral ratio
withdrawCollateral
CL33
Insufficient collateral
_transferCollateral
CL34
Credit line is not active
liquidate
CL35
ETH is not required for this operation
liquidate
CL36
Cannot liquidate since principal is 0
liquidate
CL37
Collateral ratio is above the liquidation threshold
liquidate
​
​

Error Code	Error Message	Function/Modifier name
CL1	Credit line does not exist	ifCreditLineExists
CL2	Only credit line Borrower can access	onlyCreditLineBorrower
CL3	Invalid Strategy	_updateDefaultStrategy
CL4	Protocol fee collector can't be 0 address	_updateProtocolFeeCollector
CL5	Strategy registry can't be 0 address	_updateStrategyRegistry
CL6	Reward fraction has to be less than 1	_updateLiquidatorRewardFraction
CL7	Function can only be called if credit line is ACTIVE or REQUESTED	calculateBorrowableAmount
CL8	Function cannot be called since credit line doesn't exist	updateinterestAccruedTillLastPrincipalUpdate
CL9	Borrow asset and collateral asset can't be the same	request
CL10	Price feed doesn't exist for the passed asset pair	request
CL11	Borrow limit is out of the allowed range	request
CL12	Borrow rate is out of the allowed range	request
CL13	Ideal collateral ratio is out of the allowed range	request
CL14	Borrower and lender cannot be the same address	request
CL15	Credit lines has already been accepted	accept
CL16	msg.sender is not valid	accept
CL17	Credit line is not active	depositCollateral
CL18	Lender cannot deposit collateral	depositCollateral
CL19	Lender cannot deposit collateral	_depositCollateral
CL20	ETH is not required for this operation	_depositCollateral
CL21	Credit line is not active	borrow
CL22	Requested amount cannot be withdrawn	borrow
CL23	Credit line is not active	repay
CL24	Lender address cannot repay	repay
CL25	ETH is not required for this operation	repay
CL26	msg.sender needs to be lender or borrower	close
CL27	Credit line is not active	close
CL28	Credit line cannot be closed since principal is non-zero	close
CL29	Credit line cannot be closed since interest is non-zero	close
CL30	msg.sender should be the borrower or lender	cancel
CL31	Credit line is not in the requested state	cancel
CL32	Collateral ratio cannot fall below the ideal collateral ratio	withdrawCollateral
CL33	Insufficient collateral	_transferCollateral
CL34	Credit line is not active	liquidate
CL35	ETH is not required for this operation	liquidate
CL36	Cannot liquidate since principal is 0	liquidate
CL37	Collateral ratio is above the liquidation threshold	liquidate

Last modified 1yr ago