[ERC6617] ビットベースの権限管理の仕組みを理解しよう！

pragma solidity ^0.8.7;

/**
    @title EIP-6617 Bit Based Permission
    @dev See https://eips.ethereum.org/EIPS/eip-6617
*/
interface IEIP6617 {

    /**
        MUST trigger when a permission is granted.
        @param _grantor        Grantor of the permission
        @param _permission     Permission that is granted
        @param _user           User who received the permission
    */
    event PermissionGranted(address indexed _grantor, uint256 indexed _permission, address indexed _user);

    /**
        MUST trigger when a permission is revoked.
        @param _revoker        Revoker of the permission
        @param _permission     Permission that is revoked
        @param _user           User who lost the permission
    */
    event PermissionRevoked(address indexed _revoker, uint256 indexed _permission, address indexed _user);

    /**
        @notice Check if user has permission
        @param _user                Address of the user whose permission we need to check
        @param _requiredPermission  The required permission
        @return                     True if the _permission is a superset of the _requiredPermission else False
    */
    function hasPermission(address _user, uint256 _requiredPermission)
        external
        view
        returns (bool);

    /**
        @notice Add permission to user
        @param _user                Address of the user to whom we are going to add a permission
        @param _permissionToAdd     The permission that will be added
        @return                     The new permission with the _permissionToAdd
    */
    function grantPermission(address _user, uint256 _permissionToAdd)
        external
        returns (bool);

    /**
        @notice Revoke permission from user
        @param _user                Address of the user to whom we are going to revoke a permission
        @param _permissionToRevoke  The permission that will be revoked
        @return                     The new permission without the _permissionToRevoke
    */
    function revokePermission(address _user, uint256 _permissionToRevoke)
        external
        returns (bool);
}

/**
 * @dev Defined the interface of the metadata of EIP6617, MAY NOT be implemented
 */
interface IEIP6617Meta {
    
    /**
        Structure of permission description
        @param _permission     Permission
        @param _name           Name of the permission
        @param _description    Description of the permission
    */
    struct PermissionDescription {
        uint256 permission;
        string name;
        string description;
    }

    /**
        MUST trigger when the description is updated.
        @param _permission     Permission
        @param _name           Name of the permission
        @param _description    Description of the permission
    */
    event UpdatePermissionDescription(uint256 indexed _permission, string indexed _name, string indexed _description);

    /**
        Returns the description of a given `_permission`.
        @param _permission     Permission
    */
    function getPermissionDescription(uint256 _permission) external view returns (PermissionDescription memory description);

    /**
        Return `true` if the description was set otherwise return `false`. It MUST emit `UpdatePermissionDescription` event.
        @param _permission     Permission
        @param _name           Name of the permission
        @param _description    Description of the permission
    */
    function setPermissionDescription(uint256 _permission, string memory _name, string memory _description)
        external
        returns (bool success);
}