// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import {Context, Ownable} from "@openzeppelin/contracts/access/Ownable.sol";

abstract contract Operator is Context, Ownable {
  address private _operator;

  event OperatorTransferred(
    address indexed previousOperator,
    address indexed newOperator
  );

  constructor() {
    _operator = _msgSender();
    emit OperatorTransferred(address(0), _operator);
  }

  function operator() public view returns (address) {
    return _operator;
  }

  modifier onlyOperator() {
    require(_operator == _msgSender(), "operator: caller is not the operator");
    _;
  }

  function isOperator() public view returns (bool) {
    return _msgSender() == _operator;
  }

  function transferOperator(address newOperator_) public onlyOwner {
    _transferOperator(newOperator_);
  }

  function _transferOperator(address newOperator_) internal {
    require(
      newOperator_ != address(0),
      "operator: zero address given for new operator"
    );
    emit OperatorTransferred(address(0), newOperator_);
    _operator = newOperator_;
  }
}