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Update DAIInterestRateModel to v4 (compound-finance#230)
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| pragma solidity ^0.8.10; | ||
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| import "./JumpRateModelV2.sol"; | ||
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| /** | ||
| * @title Compound's DAIInterestRateModel Contract (version 4) | ||
| * @author Compound, Dharma (modified by Maker Growth) | ||
| * @notice The change from v3 to v4 of this contract was just the `SECONDS_PER_BLOCK` constant, | ||
| * as noted in https://github.com/compound-finance/compound-protocol/issues/230 | ||
| */ | ||
| contract DAIInterestRateModelV4 is JumpRateModelV2 { | ||
| uint256 private constant BASE = 1e18; | ||
| uint256 private constant RAY_BASE = 1e27; | ||
| uint256 private constant RAY_TO_BASE_SCALE = 1e9; | ||
| uint256 private constant SECONDS_PER_BLOCK = 12; | ||
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| /** | ||
| * @notice The additional margin per block separating the base borrow rate from the roof. | ||
| */ | ||
| uint public gapPerBlock; | ||
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| /** | ||
| * @notice The assumed (1 - reserve factor) used to calculate the minimum borrow rate (reserve factor = 0.05) | ||
| */ | ||
| uint public constant assumedOneMinusReserveFactorMantissa = 0.95e18; | ||
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| PotLike pot; | ||
| JugLike jug; | ||
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| /** | ||
| * @notice Construct an interest rate model | ||
| * @param jumpMultiplierPerYear The multiplierPerBlock after hitting a specified utilization point | ||
| * @param kink_ The utilization point at which the jump multiplier is applied | ||
| * @param pot_ The address of the Dai pot (where DSR is earned) | ||
| * @param jug_ The address of the Dai jug (where SF is kept) | ||
| * @param owner_ The address of the owner, i.e. the Timelock contract (which has the ability to update parameters directly) | ||
| */ | ||
| constructor(uint jumpMultiplierPerYear, uint kink_, address pot_, address jug_, address owner_) JumpRateModelV2(0, 0, jumpMultiplierPerYear, kink_, owner_) public { | ||
| gapPerBlock = 4e16 / blocksPerYear; | ||
| pot = PotLike(pot_); | ||
| jug = JugLike(jug_); | ||
| poke(); | ||
| } | ||
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| /** | ||
| * @notice External function to update the parameters of the interest rate model | ||
| * @param baseRatePerYear The approximate target base APR, as a mantissa (scaled by BASE). For DAI, this is calculated from DSR and SF. Input not used. | ||
| * @param gapPerYear The Additional margin per year separating the base borrow rate from the roof. (scaled by BASE) | ||
| * @param jumpMultiplierPerYear The jumpMultiplierPerYear after hitting a specified utilization point | ||
| * @param kink_ The utilization point at which the jump multiplier is applied | ||
| */ | ||
| function updateJumpRateModel(uint baseRatePerYear, uint gapPerYear, uint jumpMultiplierPerYear, uint kink_) override external { | ||
| require(msg.sender == owner, "only the owner may call this function."); | ||
| gapPerBlock = gapPerYear / blocksPerYear; | ||
| updateJumpRateModelInternal(0, 0, jumpMultiplierPerYear, kink_); | ||
| poke(); | ||
| } | ||
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| /** | ||
| * @notice Calculates the current supply interest rate per block including the Dai savings rate | ||
| * @param cash The total amount of cash the market has | ||
| * @param borrows The total amount of borrows the market has outstanding | ||
| * @param reserves The total amnount of reserves the market has | ||
| * @param reserveFactorMantissa The current reserve factor the market has | ||
| * @return The supply rate per block (as a percentage, and scaled by BASE) | ||
| */ | ||
| function getSupplyRate(uint cash, uint borrows, uint reserves, uint reserveFactorMantissa) override public view returns (uint) { | ||
| uint protocolRate = super.getSupplyRate(cash, borrows, reserves, reserveFactorMantissa); | ||
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| uint underlying = cash + borrows - reserves; | ||
| if (underlying == 0) { | ||
| return protocolRate; | ||
| } else { | ||
| uint cashRate = cash * dsrPerBlock() / underlying; | ||
| return cashRate + protocolRate; | ||
| } | ||
| } | ||
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| /** | ||
| * @notice Calculates the Dai savings rate per block | ||
| * @return The Dai savings rate per block (as a percentage, and scaled by BASE) | ||
| */ | ||
| function dsrPerBlock() public view returns (uint) { | ||
| return (pot.dsr() - RAY_BASE) // scaled RAY_BASE aka RAY, and includes an extra "ONE" before subtraction | ||
| / RAY_TO_BASE_SCALE // descale to BASE | ||
| * SECONDS_PER_BLOCK; // seconds per block | ||
| } | ||
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| /** | ||
| * @notice Resets the baseRate and multiplier per block based on the stability fee and Dai savings rate | ||
| */ | ||
| function poke() public { | ||
| (uint duty, ) = jug.ilks("ETH-A"); | ||
| uint stabilityFeePerBlock = (duty + jug.base() - RAY_BASE) / RAY_TO_BASE_SCALE * SECONDS_PER_BLOCK; | ||
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| // We ensure the minimum borrow rate >= DSR / (1 - reserve factor) | ||
| baseRatePerBlock = dsrPerBlock() * BASE / assumedOneMinusReserveFactorMantissa; | ||
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| // The roof borrow rate is max(base rate, stability fee) + gap, from which we derive the slope | ||
| if (baseRatePerBlock < stabilityFeePerBlock) { | ||
| multiplierPerBlock = (stabilityFeePerBlock - baseRatePerBlock + gapPerBlock) * BASE / kink; | ||
| } else { | ||
| multiplierPerBlock = gapPerBlock * BASE / kink; | ||
| } | ||
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| emit NewInterestParams(baseRatePerBlock, multiplierPerBlock, jumpMultiplierPerBlock, kink); | ||
| } | ||
| } | ||
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| /*** Maker Interfaces ***/ | ||
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| interface PotLike { | ||
| function chi() external view returns (uint); | ||
| function dsr() external view returns (uint); | ||
| function rho() external view returns (uint); | ||
| function pie(address) external view returns (uint); | ||
| function drip() external returns (uint); | ||
| function join(uint) external; | ||
| function exit(uint) external; | ||
| } | ||
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| contract JugLike { | ||
| // --- Data --- | ||
| struct Ilk { | ||
| uint256 duty; | ||
| uint256 rho; | ||
| } | ||
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| mapping (bytes32 => Ilk) public ilks; | ||
| uint256 public base; | ||
| } |
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