Pool

• Source Code

Overview

The Pool contract is the core contract of the SparkLend Protocol, serving as the main entry point for all lending and borrowing operations. It manages the entire lifecycle of assets in the protocol, from supply and borrowing to liquidation and flash loans.

Key responsibilities include:

1. Asset Management
   • Enables users to supply assets to the protocol and earn interest
   • Manages the minting and burning of aTokens (interest-bearing tokens)
   • Tracks total supply, borrow rates, and liquidity indexes for each asset
2. Borrowing System
   • Allows users to borrow assets against supplied collateral
   • Supports both stable and variable interest rate modes
   • Implements health factor calculations to ensure protocol solvency
   • Manages debt positions and interest accrual
3. Collateral Management
   • Enables users to use supplied assets as collateral
   • Implements Loan-to-Value (LTV) and liquidation threshold parameters
   • Supports efficiency mode (E-mode) for optimized collateral usage
   • Manages isolation mode for riskier assets
4. Liquidation System
   • Allows liquidators to repay unhealthy positions
   • Implements liquidation bonuses and protocol fees
   • Manages the liquidation process to maintain protocol health
5. Flash Loans
   • Enables uncollateralized flash loans
   • Manages flash loan fees and premiums
   • Supports both single-asset and multi-asset flash loans

The contract is designed to be upgradeable through a proxy pattern and is managed by the PoolAddressesProvider. It uses a modular architecture with separate logic libraries for different operations, making it maintainable and extensible.

Architecture

The Pool contract uses a modular architecture with separate logic libraries for different operations:

• SupplyLogic: Handles supply and withdraw operations
• BorrowLogic: Manages borrow and repay operations
• FlashLoanLogic: Implements flash loan functionality
• LiquidationLogic: Handles liquidation of unhealthy positions
• EModeLogic: Manages efficiency mode operations
• BridgeLogic: Handles bridge operations
• PoolLogic: Contains general pool operations

Access Control

The contract has three main access control modifiers:

• onlyPoolConfigurator: Functions that can only be called by the PoolConfigurator contract
• onlyPoolAdmin: Functions that can only be called by pool admins
• onlyBridge: Functions that can only be called by bridge contracts

Constructor and Initialization

constructor(IPoolAddressesProvider provider)

Initializes the Pool with the address of the PoolAddressesProvider contract.

function initialize(IPoolAddressesProvider provider) external virtual initializer

Initializes the Pool when it's added to the PoolAddressesProvider. This function:

• Verifies the provider address
• Sets the maximum stable rate borrow size percent to 25%

Core Operations

The Pool contract enables users to:

1. Supply assets to the protocol
2. Withdraw supplied assets
3. Borrow assets against supplied collateral
4. Repay borrowed assets
5. Swap between stable and variable rate loans
6. Enable/disable assets as collateral
7. Rebalance stable rate positions
8. Liquidate unhealthy positions
9. Execute flash loans
10. Use efficiency mode (E-mode) for optimized collateral usage

Write Methods

supply

The referralCode is emitted in Supply event and can be for third party referral integrations. To activate referral feature and obtain a unique referral code, integrators need to submit proposal to Maker Governance.

supplyWithPermit

function supplyWithPermit(address asset, uint256 amount, address onBehalfOf, uint16 referralCode, uint256 deadline, uint8 permitV, permitR, bytes32 permitS)

Supply with transfer approval of supplied asset via permit function. This method removes the need for separate approval tx before supplying asset to the pool.

Call Params

withdraw

Withdraws amount of the underlying asset, i.e. redeems the underlying token and burns the spTokens.

If user has any existing debt backed by the underlying token, then the max amount available to withdraw is the amount that will not leave user health factor < 1 after withdrawal.

Call Params

borrow

Borrows amount of asset with interestRateMode, sending the amount to msg.sender, with the debt being incurred by onBehalfOf.

Call Params

repay

Repays onBehalfOf's debt amount of asset which has a rateMode.

Call Params

repayWithPermit

function repayWithPermit(address asset, uint256 amount, uint256 interestRateMode, address onBehalfOf, uint256 deadline, uint8 permitV, permitR, bytes32 permitS)

Repay with transfer approval of borrowed asset via permit function. This method removes the need for separate approval tx before repaying asset to the pool.

Call Params

repayWithSpTokens

function repayWithSpTokens(address asset,uint256 amount,uint256 interestRateMode)

Allows user to repay with spTokens of the underlying debt asset without any approvals eg. Pay DAI debt using aDAI tokens.

Call Params

swapBorrowRateMode

Swaps msg.sender's borrow rate mode between stable and variable.

Call Params

rebalanceStableBorrowRate

function rebalanceStableBorrowRate(address asset, address user)

Rebalances stable borrow rate of the user for given asset. In case of liquidity crunches on the protocol, stable rate borrows might need to be rebalanced to bring back equilibrium between the borrow and supply rates.

Call Params

setUserUseReserveAsCollateral

Sets the asset of msg.sender to be used as collateral or not.

Call Params

liquidationCall

Liquidate positions with a health factor below 1.

When the health factor of a position is below 1, liquidators repay part or all of the outstanding borrowed amount on behalf of the borrower, while receiving a discounted amount of collateral in return (also known as a liquidation 'bonus"). Liquidators can decide if they want to receive an equivalent amount of collateral spTokens instead of the underlying asset. When the liquidation is completed successfully, the health factor of the position is increased, bringing the health factor above 1.

Liquidators can only close a certain amount of collateral defined by a close factor. Currently the close factor is 0.5. In other words, liquidators can only liquidate a maximum of 50% of the amount pending to be repaid in a position. The liquidation discount applies to this amount.

• In most scenarios, profitable liquidators will choose to liquidate as much as they can (50% of the user position).
• debtToCover parameter can be set to uint(-1) and the protocol will proceed with the highest possible liquidation allowed by the close factor.
• To check a user's health factor, use getUserAccountData().

Call Params

flashLoan

function flashLoan( address receiverAddress, address[] calldata assets, uint256[] calldata amounts, uint256[] interestRateModes, address onBehalfOf, bytes calldata params, uint16 referralCode)

Allows users to access liquidity of the pool for given list of assets for one transaction as long as the amount taken plus fee is returned or debt position is opened by the end of transaction.

Call Params

flashLoanSimple

function flashLoanSimple( address receiverAddress, address asset, uint256 amount, bytes calldata params, uint16 referralCode)

Allows users to access liquidity of one reserve or one transaction as long as the amount taken plus fee is returned.

Call Params

mintToTreasury

function mintToTreasury(address[] calldata assets)

Mints reserve income accrued to treasury (as per the reserve factor) for the given list of assets.

Call Params

setUserEMode

function setUserEMode(uint8 categoryId)

Updates the user efficiency mode category. The category id must be a valid id already defined by Pool or Risk Admins

Call Params

mintUnbacked

mintUnbacked (asset, amount, onBehalfOf, referralCode)

Allows contracts, with BRIDGE role permission, to mint unbacked spTokens to the onBehalfOf address.

backUnbacked

backUnbacked (asset, amount, fee)

Allows contracts, with BRIDGE role permission, to back the currently unbacked spTokens with amount of underlying asset and pay fee.

rescueTokens

function rescueTokens(address token, address to, uint256 amount)

Rescue and transfer tokens locked in this contract.

deposit

function deposit(address asset, uint256 amount, address onBehalfOf, uint16 referralCode)

Alias for supply(). See supply documentation for details.

finalizeTransfer

function finalizeTransfer(address asset, address from, address to, uint256 amount, uint256 balanceFromBefore, uint256 balanceToBefore)

Internal function called by aTokens to finalize transfers. This function should not be called directly.

View Methods

getReserveData

Returns the state and configuration of the reserve.

Call Params

Return Values

getUserAccountData

Returns the user account data across all the reserves. All values are expressed in the market's base currency.

Call params

Return Values

getConfiguration

Returns the configuration of the reserve.

Call Params

Return Values

getUserConfiguration

Returns the configuration of the user across all the reserves.

Call Params

Return Values

getReserveNormalizedIncome

function getReserveNormalizedIncome(address asset)

Returns the ongoing normalized income for the reserve. A value of 1e27 means there is no income. As time passes, the yield is accrued. A value of 2*1e27 means for each unit of asset one unit of income has been accrued.

Return Value

getReserveNormalizedDebt

function getReserveNormalizedVariableDebt(address asset)

Returns the ongoing normalized variable debt for the reserve. A value of 1e27 means there is no debt. As time passes, the debt is accrued. A value of 2*1e27 means that for each unit of debt, one unit worth of interest has been accumulated.

Return Value

getReservesList

function getReservesList()

Returns the list of initialized reserves.

getEModeCategoryData

function getEModeCategoryData(uint8 id)

Returns category data for the given eModeCategory id.

Return Values

getUserEMode

function getUserEMode(address user)

Returns eModeCategory Id of the user's eMode. 0 ⇒ no eMode.

FLASHLOAN_PREMIUM_TOTAL

function FLASHLOAN_PREMIUM_TOTAL() public view returns (uint128)

Returns the percent of total flashloan premium paid by the borrower.
A part of this premium is added to reserve's liquidity index i.e. paid to the liquidity provider and the other part is paid to the protocol i.e. accrued to the treasury.

FLASHLOAN_PREMIUM_TO_PROTOCOL

function FLASHLOAN_PREMIUM_TO_PROTOCOL() public view returns (uint128)

Returns the percent of flashloan premium that is accrued to the treasury.

Error Codes

Common error codes and their meanings:

• CALLER_NOT_POOL_CONFIGURATOR: Only PoolConfigurator can call this function
• CALLER_NOT_POOL_ADMIN: Only PoolAdmin can call this function
• CALLER_NOT_BRIDGE: Only Bridge can call this function
• INVALID_ADDRESSES_PROVIDER: Invalid PoolAddressesProvider address
• ASSET_NOT_LISTED: Asset is not listed in the protocol
• HEALTH_FACTOR_LOWER_THAN_LIQUIDATION_THRESHOLD: Operation would result in health factor below liquidation threshold
• COLLATERAL_CANNOT_COVER_NEW_BORROW: Not enough collateral to cover new borrow
• COLLATERAL_SAME_AS_BORROWING_CURRENCY: Cannot use same asset as collateral and borrowing
• AMOUNT_BIGGER_THAN_MAX_LOAN_SIZE_STABLE: Amount exceeds max stable rate loan size
• NO_DEBT_OF_SELECTED_TYPE: No debt of selected type to repay
• NO_EXPLICIT_AMOUNT_TO_REPAY_ON_BEHALF: No explicit amount to repay on behalf
• NO_MORE_RESERVES_ALLOWED: Maximum number of reserves reached
• ZERO_ADDRESS_NOT_VALID: Zero address not valid
• EMODE_CATEGORY_RESERVED: E-mode category 0 is reserved
• CALLER_NOT_ATOKEN: Only aToken can call this function