// SPDX-License-Identifier: MIT

pragma solidity >=0.8.0;

import "./Ownable.sol";

/**
 * @title Roles
 * @dev Library for managing addresses assigned to a Role.
 */
library Roles {
  struct Role {
    mapping (address => bool) bearer;
  }

  /**
   * @dev Give an account access to this role.
   */
  function add(Role storage role, address account) internal {
    require(!has(role, account), "Roles: account already has role");
    role.bearer[account] = true;
  }

  /**
   * @dev Remove an account's access to this role.
   */
  function remove(Role storage role, address account) internal {
    require(has(role, account), "Roles: account does not have role");
    role.bearer[account] = false;
  }

  /**
   * @dev Check if an account has this role.
   * @return bool
   */
  function has(Role storage role, address account) internal view returns (bool) {
    require(account != address(0), "Roles: account is the zero address");
    return role.bearer[account];
  }
}

contract OperatorRole {
  using Roles for Roles.Role;

  event OperatorAdded(address indexed account);
  event OperatorRemoved(address indexed account);

  Roles.Role private _operators;

  modifier onlyOperator() {
    require(isOperator(msg.sender), "OperatorRole: caller does not have the Operator role");
    _;
  }

  function isOperator(address account) public view returns (bool) {
    return _operators.has(account);
  }

  function _addOperator(address account) internal {
    _operators.add(account);
    emit OperatorAdded(account);
  }

  function _removeOperator(address account) internal {
    _operators.remove(account);
    emit OperatorRemoved(account);
  }
}

contract OwnableOperatorRole is Ownable, OperatorRole {
  function __OwnableOperatorRole_init () internal {
    __Ownable_init();
  }

  function addOperator(address account) external onlyOwner {
    _addOperator(account);
  }

  function removeOperator(address account) external onlyOwner {
    _removeOperator(account);
  }
}