abstract contract OracleRef is IOracleRef, CoreRef {
    using Decimal for Decimal.D256;
    using SafeCast for int256;

    /// @notice the oracle reference by the contract
    IOracle public override oracle;

    /// @notice the backup oracle reference by the contract
    IOracle public override backupOracle;

    /// @notice number of decimals to scale oracle price by, i.e. multiplying by 10^(decimalsNormalizer)
    int256 public override decimalsNormalizer;

    bool public override doInvert;

    /// @notice OracleRef constructor
    /// @param _core Fei Core to reference
    /// @param _oracle oracle to reference
    /// @param _backupOracle backup oracle to reference
    /// @param _decimalsNormalizer number of decimals to normalize the oracle feed if necessary
    /// @param _doInvert invert the oracle price if this flag is on
    constructor(address _core, address _oracle, address _backupOracle, int256 _decimalsNormalizer, bool _doInvert) CoreRef(_core) {
        _setOracle(_oracle);
        if (_backupOracle != address(0) && _backupOracle != _oracle) {
            _setBackupOracle(_backupOracle);
        }
        _setDoInvert(_doInvert);
        _setDecimalsNormalizer(_decimalsNormalizer);
    }

    /// @notice sets the referenced oracle
    /// @param newOracle the new oracle to reference
    function setOracle(address newOracle) external override onlyGovernor {
        _setOracle(newOracle);
    }

    /// @notice sets the flag for whether to invert or not
    /// @param newDoInvert the new flag for whether to invert
    function setDoInvert(bool newDoInvert) external override onlyGovernor {
        _setDoInvert(newDoInvert);
    }

    /// @notice sets the new decimalsNormalizer
    /// @param newDecimalsNormalizer the new decimalsNormalizer
    function setDecimalsNormalizer(int256 newDecimalsNormalizer) external override onlyGovernor {
        _setDecimalsNormalizer(newDecimalsNormalizer);
    }
    /// @notice sets the referenced backup oracle
    /// @param newBackupOracle the new backup oracle to reference
    function setBackupOracle(address newBackupOracle) external override onlyGovernor {
        _setBackupOracle(newBackupOracle);
    }

    /// @notice invert a peg price
    /// @param price the peg price to invert
    /// @return the inverted peg as a Decimal
    /// @dev the inverted peg would be X per FEI
    function invert(Decimal.D256 memory price)
        public
        pure
        override
        returns (Decimal.D256 memory)
    {
        return Decimal.one().div(price);
    }

    /// @notice updates the referenced oracle
    function updateOracle() public override {
        oracle.update();
    }

    /// @notice the peg price of the referenced oracle
    /// @return the peg as a Decimal
    /// @dev the peg is defined as FEI per X with X being ETH, dollars, etc
    function readOracle() public view override returns (Decimal.D256 memory) {
        (Decimal.D256 memory _peg, bool valid) = oracle.read();
        if (!valid && address(backupOracle) != address(0)) {
            (_peg, valid) = backupOracle.read();
        }
        require(valid, "OracleRef: oracle invalid");

        // Scale the oracle price by token decimals delta if necessary
        uint256 scalingFactor;
        if (decimalsNormalizer < 0) {
            scalingFactor = 10 ** (-1 * decimalsNormalizer).toUint256();
            _peg = _peg.div(scalingFactor);
        } else {
            scalingFactor = 10 ** decimalsNormalizer.toUint256();
            _peg = _peg.mul(scalingFactor);
        }

        // Invert the oracle price if necessary
        if (doInvert) {
            _peg = invert(_peg);
        }
        return _peg;
    }

    function _setOracle(address newOracle) internal {
        require(newOracle != address(0), "OracleRef: zero address");
        address oldOracle = address(oracle);
        oracle = IOracle(newOracle);
        emit OracleUpdate(oldOracle, newOracle);
    }

    // Supports zero address if no backup
    function _setBackupOracle(address newBackupOracle) internal {
        address oldBackupOracle = address(backupOracle);
        backupOracle = IOracle(newBackupOracle);
        emit BackupOracleUpdate(oldBackupOracle, newBackupOracle);
    }

    function _setDoInvert(bool newDoInvert) internal {
        bool oldDoInvert = doInvert;
        doInvert = newDoInvert;
        
        if (oldDoInvert != newDoInvert) {
            _setDecimalsNormalizer( -1 * decimalsNormalizer);
        }

        emit InvertUpdate(oldDoInvert, newDoInvert);
    }

    function _setDecimalsNormalizer(int256 newDecimalsNormalizer) internal {
        int256 oldDecimalsNormalizer = decimalsNormalizer;
        decimalsNormalizer = newDecimalsNormalizer;
        emit DecimalsNormalizerUpdate(oldDecimalsNormalizer, newDecimalsNormalizer);
    }

    function _setDecimalsNormalizerFromToken(address token) internal {
        int256 feiDecimals = 18;
        int256 _decimalsNormalizer = feiDecimals - int256(uint256(IERC20Metadata(token).decimals()));
        
        if (doInvert) {
            _decimalsNormalizer = -1 * _decimalsNormalizer;
        }
        
        _setDecimalsNormalizer(_decimalsNormalizer);
    }
}
/// @title Reference to an Oracle
/// @author Fei Protocol
/// @notice defines some utilities around interacting with the referenced oracle
function setDecimalsNormalizer(int256 newDecimalsNormalizer) external override onlyGovernor {
    _setDecimalsNormalizer(newDecimalsNormalizer);
}

/// @notice sets the new decimalsNormalizer
/// @param newDecimalsNormalizer the new decimalsNormalizer