abstract contract CoreRef is ICoreRef, Pausable {
    ICore private _core;

    /// @notice CoreRef constructor
    /// @param core Fei Core to reference
    constructor(address core) public {
        _core = ICore(core);
    }

    modifier ifMinterSelf() {
        if (_core.isMinter(address(this))) {
            _;
        }
    }

    modifier ifBurnerSelf() {
        if (_core.isBurner(address(this))) {
            _;
        }
    }

    modifier onlyMinter() {
        require(_core.isMinter(msg.sender), "CoreRef: Caller is not a minter");
        _;
    }

    modifier onlyBurner() {
        require(_core.isBurner(msg.sender), "CoreRef: Caller is not a burner");
        _;
    }

    modifier onlyPCVController() {
        require(
            _core.isPCVController(msg.sender),
            "CoreRef: Caller is not a PCV controller"
        );
        _;
    }

    modifier onlyGovernor() {
        require(
            _core.isGovernor(msg.sender),
            "CoreRef: Caller is not a governor"
        );
        _;
    }

    modifier onlyGuardianOrGovernor() {
        require(
            _core.isGovernor(msg.sender) ||
            _core.isGuardian(msg.sender),
            "CoreRef: Caller is not a guardian or governor"
        );
        _;
    }

    modifier onlyFei() {
        require(msg.sender == address(fei()), "CoreRef: Caller is not FEI");
        _;
    }

    modifier onlyGenesisGroup() {
        require(
            msg.sender == _core.genesisGroup(),
            "CoreRef: Caller is not GenesisGroup"
        );
        _;
    }

    modifier postGenesis() {
        require(
            _core.hasGenesisGroupCompleted(),
            "CoreRef: Still in Genesis Period"
        );
        _;
    }

    modifier nonContract() {
        require(!Address.isContract(msg.sender), "CoreRef: Caller is a contract");
        _;
    }

    /// @notice set new Core reference address
    /// @param core the new core address
    function setCore(address core) external override onlyGovernor {
        _core = ICore(core);
        emit CoreUpdate(core);
    }

    /// @notice set pausable methods to paused
    function pause() public override onlyGuardianOrGovernor {
        _pause();
    }

    /// @notice set pausable methods to unpaused
    function unpause() public override onlyGuardianOrGovernor {
        _unpause();
    }

    /// @notice address of the Core contract referenced
    /// @return ICore implementation address
    function core() public view override returns (ICore) {
        return _core;
    }

    /// @notice address of the Fei contract referenced by Core
    /// @return IFei implementation address
    function fei() public view override returns (IFei) {
        return _core.fei();
    }

    /// @notice address of the Tribe contract referenced by Core
    /// @return IERC20 implementation address
    function tribe() public view override returns (IERC20) {
        return _core.tribe();
    }

    /// @notice fei balance of contract
    /// @return fei amount held
    function feiBalance() public view override returns (uint256) {
        return fei().balanceOf(address(this));
    }

    /// @notice tribe balance of contract
    /// @return tribe amount held
    function tribeBalance() public view override returns (uint256) {
        return tribe().balanceOf(address(this));
    }

    function _burnFeiHeld() internal {
        fei().burn(feiBalance());
    }

    function _mintFei(uint256 amount) internal {
        fei().mint(address(this), amount);
    }
}
/// @title A Reference to Core
/// @author Fei Protocol
/// @notice defines some modifiers and utilities around interacting with Core
function feiBalance() public view override returns (uint256) {
        return fei().balanceOf(address(this));
    }
/// @notice fei balance of contract
/// @return fei amount held