pragma solidity ^0.8.0;


/**
 * @title Ownable
 * @dev The Ownable contract define an owner address and methods to transfer ownership
 *
 * SPDX-License-Identifier: MIT
 * @author Cyril Lapinte - <cyril.lapinte@gmail.com>
 *
 * Error messages
 * OW01: Only the owner
 * OW02: Owner can't be undefined
 */
contract Ownable {

  address public owner;

  event OwnershipRenounced(address indexed previousOwner);
  event OwnershipTransferred(
    address indexed previousOwner,
    address indexed newOwner
  );

  /**
   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
   * account.
   */
  constructor() {
    owner = msg.sender;
  }

  /**
   * @dev Throws if called by any account other than the owner.
   */
  modifier onlyOwner() {
    require(msg.sender == owner, "OW01");
    _;
  }

  /**
   * @dev Allows the current owner to relinquish control of the contract.
   */
  function renounceOwnership() public onlyOwner {
    emit OwnershipRenounced(owner);
    owner = address(0);
  }

  /**
   * @dev Allows the current owner to transfer control of the contract to a newOwner.
   * @param _newOwner The address to transfer ownership to.
   */
  function transferOwnership(address _newOwner) public onlyOwner {
    _transferOwnership(_newOwner);
  }

  /**
   * @dev Transfers control of the contract to a newOwner.
   * @param _newOwner The address to transfer ownership to.
   */
  function _transferOwnership(address _newOwner) internal {
    require(_newOwner != address(0), "OW02");
    emit OwnershipTransferred(owner, _newOwner);
    owner = _newOwner;
  }
}