IAsset.sol

// SPDX-License-Identifier: BlueOak-1.0.0
pragma solidity 0.8.19;

import "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
import "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";
import "../libraries/Fixed.sol";
import "./IMain.sol";
import "./IRewardable.sol";

// Not used directly in the IAsset interface, but used by many consumers to save stack space
struct Price {
    uint192 low; // {UoA/tok}
    uint192 high; // {UoA/tok}
}

/**
 * @title IAsset
 * @notice Supertype. Any token that interacts with our system must be wrapped in an asset,
 * whether it is used as RToken backing or not. Any token that can report a price in the UoA
 * is eligible to be an asset.
 */
interface IAsset is IRewardable {
    /// Refresh saved price
    /// The Reserve protocol calls this at least once per transaction, before relying on
    /// the Asset's other functions.
    /// @dev Called immediately after deployment, before use
    function refresh() external;

    /// Should not revert
    /// low should be nonzero if the asset could be worth selling
    /// @return low {UoA/tok} The lower end of the price estimate
    /// @return high {UoA/tok} The upper end of the price estimate
    function price() external view returns (uint192 low, uint192 high);

    /// Should not revert
    /// lotLow should be nonzero when the asset might be worth selling
    /// @dev Deprecated. Phased out in 3.1.0, but left on interface for backwards compatibility
    /// @return lotLow {UoA/tok} The lower end of the lot price estimate
    /// @return lotHigh {UoA/tok} The upper end of the lot price estimate
    function lotPrice() external view returns (uint192 lotLow, uint192 lotHigh);

    /// @return {tok} The balance of the ERC20 in whole tokens
    function bal(address account) external view returns (uint192);

    /// @return The ERC20 contract of the token with decimals() available
    function erc20() external view returns (IERC20Metadata);

    /// @return The number of decimals in the ERC20; just for gas optimization
    function erc20Decimals() external view returns (uint8);

    /// @return If the asset is an instance of ICollateral or not
    function isCollateral() external view returns (bool);

    /// @return {UoA} The max trade volume, in UoA
    function maxTradeVolume() external view returns (uint192);

    /// @return {s} The timestamp of the last refresh() that saved prices
    function lastSave() external view returns (uint48);
}

// Used only in Testing. Strictly speaking an Asset does not need to adhere to this interface
interface TestIAsset is IAsset {
    /// @return The address of the chainlink feed
    function chainlinkFeed() external view returns (AggregatorV3Interface);

    /// {1} The max % deviation allowed by the oracle
    function oracleError() external view returns (uint192);

    /// @return {s} Seconds that an oracle value is considered valid
    function oracleTimeout() external view returns (uint48);

    /// @return {s} The maximum of all oracle timeouts on the plugin
    function maxOracleTimeout() external view returns (uint48);

    /// @return {s} Seconds that the price() should decay over, after stale price
    function priceTimeout() external view returns (uint48);

    /// @return {UoA/tok} The last saved low price
    function savedLowPrice() external view returns (uint192);

    /// @return {UoA/tok} The last saved high price
    function savedHighPrice() external view returns (uint192);
}

/// CollateralStatus must obey a linear ordering. That is:
/// - being DISABLED is worse than being IFFY, or SOUND
/// - being IFFY is worse than being SOUND.
enum CollateralStatus {
    SOUND,
    IFFY, // When a peg is not holding or a chainlink feed is stale
    DISABLED // When the collateral has completely defaulted
}

/// Upgrade-safe maximum operator for CollateralStatus
library CollateralStatusComparator {
    /// @return Whether a is worse than b
    function worseThan(CollateralStatus a, CollateralStatus b) internal pure returns (bool) {
        return uint256(a) > uint256(b);
    }
}

/**
 * @title ICollateral
 * @notice A subtype of Asset that consists of the tokens eligible to back the RToken.
 */
interface ICollateral is IAsset {
    /// Emitted whenever the collateral status is changed
    /// @param newStatus The old CollateralStatus
    /// @param newStatus The updated CollateralStatus
    event CollateralStatusChanged(
        CollateralStatus indexed oldStatus,
        CollateralStatus indexed newStatus
    );

    /// @dev refresh()
    /// Refresh exchange rates and update default status.
    /// VERY IMPORTANT: In any valid implemntation, status() MUST become DISABLED in refresh() if
    /// refPerTok() has ever decreased since last call.

    /// @return The canonical name of this collateral's target unit.
    function targetName() external view returns (bytes32);

    /// @return The status of this collateral asset. (Is it defaulting? Might it soon?)
    function status() external view returns (CollateralStatus);

    // ==== Exchange Rates ====

    /// @return {ref/tok} Quantity of whole reference units per whole collateral tokens
    function refPerTok() external view returns (uint192);

    /// @return {target/ref} Quantity of whole target units per whole reference unit in the peg
    function targetPerRef() external view returns (uint192);
}

// Used only in Testing. Strictly speaking a Collateral does not need to adhere to this interface
interface TestICollateral is TestIAsset, ICollateral {
    /// @return The epoch timestamp when the collateral will default from IFFY to DISABLED
    function whenDefault() external view returns (uint256);

    /// @return The amount of time a collateral must be in IFFY status until being DISABLED
    function delayUntilDefault() external view returns (uint48);

    /// @return The underlying refPerTok, likely not included in all collaterals however.
    function underlyingRefPerTok() external view returns (uint192);
}