pragma ever-solidity >= 0.68.0;

/// @title Upgradable by Request Base Interface
interface IUpgradableByRequestBase {
    /// @dev Emits when the contract's upgrader was changed
    /// @dev Should be emitted only inside _setUpgraderInternal()
    event UpgraderChanged(
        address current,
        address previous
    );

    /// @notice Get the current contract's upgrader
    /// @return address Upgrader's address
    function getUpgrader() external view responsible returns (address);

    /// @dev Request contract upgrade from upgrader
    /// @param _remainingGasTo Gas recipient
    function requestUpgrade(optional(address) _remainingGasTo) external view;
}