IPegStabilityModule

The Fei PSM is a contract which holds a reserve of assets in order to exchange FEI at $1 of underlying assets with a fee. mint() - buy FEI for $1 of underlying tokens redeem() - sell FEI back for $1 of the same

The contract has a reservesThreshold() of underlying meant to stand ready for redemptions. Any surplus reserves can be sent into the PCV using allocateSurplus()

The contract is a PCVDeposit - to track reserves OracleRef - to determine price of underlying, and RateLimitedMinter - to stop infinite mints and related issues (but this is in the implementation due to inheritance-linearization difficulties)

Inspired by MakerDAO PSM, code written without reference

Functions

mint

function mint(
    address to,
    uint256 amountIn,
    uint256 minAmountOut
) external returns (uint256 amountFeiOut)

mint amountFeiOut FEI to address to for amountIn underlying tokens

see getMintAmountOut() to pre-calculate amount out

Parameters

Name	Type	Description
to	address
amountIn	uint256
minAmountOut	uint256

redeem

function redeem(
    address to,
    uint256 amountFeiIn,
    uint256 minAmountOut
) external returns (uint256 amountOut)

redeem amountFeiIn FEI for amountOut underlying tokens and send to address to

see getRedeemAmountOut() to pre-calculate amount out

Parameters

Name	Type	Description
to	address
amountFeiIn	uint256
minAmountOut	uint256

allocateSurplus

function allocateSurplus() external

send any surplus reserves to the PCV allocation

setMintFee

function setMintFee(
    uint256 newMintFeeBasisPoints
) external

set the mint fee vs oracle price in basis point terms

Parameters

Name	Type	Description
newMintFeeBasisPoints	uint256

setRedeemFee

function setRedeemFee(
    uint256 newRedeemFeeBasisPoints
) external

set the redemption fee vs oracle price in basis point terms

Parameters

Name	Type	Description
newRedeemFeeBasisPoints	uint256

setReservesThreshold

function setReservesThreshold(
    uint256 newReservesThreshold
) external

set the ideal amount of reserves for the contract to hold for redemptions

Parameters

Name	Type	Description
newReservesThreshold	uint256

setSurplusTarget

function setSurplusTarget(
    contract IPCVDeposit newTarget
) external

set the target for sending surplus reserves

Parameters

Name	Type	Description
newTarget	contract IPCVDeposit

getMintAmountOut

function getMintAmountOut(
    uint256 amountIn
) external returns (uint256 amountFeiOut)

calculate the amount of FEI out for a given amountIn of underlying

Parameters

Name	Type	Description
amountIn	uint256

getRedeemAmountOut

function getRedeemAmountOut(
    uint256 amountFeiIn
) external returns (uint256 amountOut)

calculate the amount of underlying out for a given amountFeiIn of FEI

Parameters

Name	Type	Description
amountFeiIn	uint256

getMaxMintAmountOut

function getMaxMintAmountOut() external returns (uint256)

the maximum mint amount out

hasSurplus

function hasSurplus() external returns (bool)

a flag for whether the current balance is above (true) or below and equal (false) to the reservesThreshold

reservesSurplus

function reservesSurplus() external returns (int256)

an integer representing the positive surplus or negative deficit of contract balance vs reservesThreshold

reservesThreshold

function reservesThreshold() external returns (uint256)

the ideal amount of reserves for the contract to hold for redemptions

mintFeeBasisPoints

function mintFeeBasisPoints() external returns (uint256)

the mint fee vs oracle price in basis point terms

redeemFeeBasisPoints

function redeemFeeBasisPoints() external returns (uint256)

the redemption fee vs oracle price in basis point terms

underlyingToken

function underlyingToken() external returns (contract IERC20)

the underlying token exchanged for FEI

surplusTarget

function surplusTarget() external returns (contract IPCVDeposit)

the PCV deposit target to send surplus reserves

MAX_FEE

function MAX_FEE() external returns (uint256)

the max mint and redeem fee in basis points

Events

AllocateSurplus

event AllocateSurplus(
    address caller,
    uint256 amount
)

event emitted when excess PCV is allocated

Parameters

Name	Type	Description
caller	address
amount	uint256

MaxFeeUpdate

event MaxFeeUpdate(
    uint256 oldMaxFee,
    uint256 newMaxFee
)

event emitted when a new max fee is set

Parameters

Name	Type	Description
oldMaxFee	uint256
newMaxFee	uint256

MintFeeUpdate

event MintFeeUpdate(
    uint256 oldMintFee,
    uint256 newMintFee
)

event emitted when a new mint fee is set

Parameters

Name	Type	Description
oldMintFee	uint256
newMintFee	uint256

RedeemFeeUpdate

event RedeemFeeUpdate(
    uint256 oldRedeemFee,
    uint256 newRedeemFee
)

event emitted when a new redeem fee is set

Parameters

Name	Type	Description
oldRedeemFee	uint256
newRedeemFee	uint256

ReservesThresholdUpdate

event ReservesThresholdUpdate(
    uint256 oldReservesThreshold,
    uint256 newReservesThreshold
)

event emitted when reservesThreshold is updated

Parameters

Name	Type	Description
oldReservesThreshold	uint256
newReservesThreshold	uint256

SurplusTargetUpdate

event SurplusTargetUpdate(
    contract IPCVDeposit oldTarget,
    contract IPCVDeposit newTarget
)

event emitted when surplus target is updated

Parameters

Name	Type	Description
oldTarget	contract IPCVDeposit
newTarget	contract IPCVDeposit

Redeem

event Redeem(
    address to,
    uint256 amountFeiIn,
    uint256 amountAssetOut
)

event emitted upon a redemption

Parameters

Name	Type	Description
to	address
amountFeiIn	uint256
amountAssetOut	uint256

Mint

event Mint(
    address to,
    uint256 amountIn,
    uint256 amountFeiOut
)

event emitted when fei gets minted

Parameters

Name	Type	Description
to	address
amountIn	uint256
amountFeiOut	uint256