abstract contract AccessControl is Context {
        using EnumerableSet for EnumerableSet.AddressSet;
        using Address for address;

        struct RoleData {
            EnumerableSet.AddressSet members;
            bytes32 adminRole;
        }

        mapping(bytes32 => RoleData) private _roles;

        bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;

        /**
        * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
        *
        * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
        * {RoleAdminChanged} not being emitted signaling this.
        *
        * _Available since v3.1._
        */
        event RoleAdminChanged(
            bytes32 indexed role,
            bytes32 indexed previousAdminRole,
            bytes32 indexed newAdminRole
        );

        /**
        * @dev Emitted when `account` is granted `role`.
        *
        * `sender` is the account that originated the contract call, an admin role
        * bearer except when using {_setupRole}.
        */
        event RoleGranted(
            bytes32 indexed role,
            address indexed account,
            address indexed sender
        );

        /**
        * @dev Emitted when `account` is revoked `role`.
        *
        * `sender` is the account that originated the contract call:
        *   - if using `revokeRole`, it is the admin role bearer
        *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
        */
        event RoleRevoked(
            bytes32 indexed role,
            address indexed account,
            address indexed sender
        );

        /**
        * @dev Returns `true` if `account` has been granted `role`.
        */
        function hasRole(bytes32 role, address account) public view returns (bool) {
            return _roles[role].members.contains(account);
        }

        /**
        * @dev Returns the number of accounts that have `role`. Can be used
        * together with {getRoleMember} to enumerate all bearers of a role.
        */
        function getRoleMemberCount(bytes32 role) public view returns (uint256) {
            return _roles[role].members.length();
        }

        /**
        * @dev Returns one of the accounts that have `role`. `index` must be a
        * value between 0 and {getRoleMemberCount}, non-inclusive.
        *
        * Role bearers are not sorted in any particular way, and their ordering may
        * change at any point.
        *
        * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
        * you perform all queries on the same block. See the following
        * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
        * for more information.
        */
        function getRoleMember(bytes32 role, uint256 index)
            public
            view
            returns (address)
        {
            return _roles[role].members.at(index);
        }

        /**
        * @dev Returns the admin role that controls `role`. See {grantRole} and
        * {revokeRole}.
        *
        * To change a role's admin, use {_setRoleAdmin}.
        */
        function getRoleAdmin(bytes32 role) public view returns (bytes32) {
            return _roles[role].adminRole;
        }

        /**
        * @dev Grants `role` to `account`.
        *
        * If `account` had not been already granted `role`, emits a {RoleGranted}
        * event.
        *
        * Requirements:
        *
        * - the caller must have ``role``'s admin role.
        */
        function grantRole(bytes32 role, address account) public virtual {
            require(
                hasRole(_roles[role].adminRole, _msgSender()),
                "AccessControl: sender must be an admin to grant"
            );

            _grantRole(role, account);
        }

        /**
        * @dev Revokes `role` from `account`.
        *
        * If `account` had been granted `role`, emits a {RoleRevoked} event.
        *
        * Requirements:
        *
        * - the caller must have ``role``'s admin role.
        */
        function revokeRole(bytes32 role, address account) public virtual {
            require(
                hasRole(_roles[role].adminRole, _msgSender()),
                "AccessControl: sender must be an admin to revoke"
            );

            _revokeRole(role, account);
        }

        /**
        * @dev Revokes `role` from the calling account.
        *
        * Roles are often managed via {grantRole} and {revokeRole}: this function's
        * purpose is to provide a mechanism for accounts to lose their privileges
        * if they are compromised (such as when a trusted device is misplaced).
        *
        * If the calling account had been granted `role`, emits a {RoleRevoked}
        * event.
        *
        * Requirements:
        *
        * - the caller must be `account`.
        */
        function renounceRole(bytes32 role, address account) public virtual {
            require(
                account == _msgSender(),
                "AccessControl: can only renounce roles for self"
            );

            _revokeRole(role, account);
        }

        /**
        * @dev Grants `role` to `account`.
        *
        * If `account` had not been already granted `role`, emits a {RoleGranted}
        * event. Note that unlike {grantRole}, this function doesn't perform any
        * checks on the calling account.
        *
        * [WARNING]
        * ====
        * This function should only be called from the constructor when setting
        * up the initial roles for the system.
        *
        * Using this function in any other way is effectively circumventing the admin
        * system imposed by {AccessControl}.
        * ====
        */
        function _setupRole(bytes32 role, address account) internal virtual {
            _grantRole(role, account);
        }

        /**
        * @dev Sets `adminRole` as ``role``'s admin role.
        *
        * Emits a {RoleAdminChanged} event.
        */
        function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
            emit RoleAdminChanged(role, _roles[role].adminRole, adminRole);
            _roles[role].adminRole = adminRole;
        }

        function _grantRole(bytes32 role, address account) private {
            if (_roles[role].members.add(account)) {
                emit RoleGranted(role, account, _msgSender());
            }
        }

        function _revokeRole(bytes32 role, address account) private {
            if (_roles[role].members.remove(account)) {
                emit RoleRevoked(role, account, _msgSender());
            }
        }
    }
/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms.
 *
 * Roles are referred to by their `bytes32` identifier. These should be exposed
 * in the external API and be unique. The best way to achieve this is by
 * using `public constant` hash digests:
 *
 * ```
 * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
 * ```
 *
 * Roles can be used to represent a set of permissions. To restrict access to a
 * function call, use {hasRole}:
 *
 * ```
 * function foo() public {
 *     require(hasRole(MY_ROLE, msg.sender));
 *     ...
 * }
 * ```
 *
 * Roles can be granted and revoked dynamically via the {grantRole} and
 * {revokeRole} functions. Each role has an associated admin role, and only
 * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
 *
 * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
 * that only accounts with this role will be able to grant or revoke other
 * roles. More complex role relationships can be created by using
 * {_setRoleAdmin}.
 *
 * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
 * grant and revoke this role. Extra precautions should be taken to secure
 * accounts that have been granted it.
 */
function getRoleMember(bytes32 role, uint256 index)
            public
            view
            returns (address)
        {
            return _roles[role].members.at(index);
        }
/**
 * @dev Returns one of the accounts that have `role`. `index` must be a
 * value between 0 and {getRoleMemberCount}, non-inclusive.
 *
 * Role bearers are not sorted in any particular way, and their ordering may
 * change at any point.
 *
 * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
 * you perform all queries on the same block. See the following
 * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
 * for more information.
 */