pragma ever-solidity >= 0.68.0;

pragma AbiHeader expire;
pragma AbiHeader pubkey;

import "../libraries/UtilityErrors.tsol";

contract ExternalOwner {
    uint public owner;

    event OwnershipTransferred(uint previousOwner, uint newOwner);

    modifier onlyOwner() {
        require(msg.pubkey() == owner, UtilityErrors.CALLER_IS_NOT_OWNER);
        _;
    }

    /*
        @dev Internal function for setting owner
        Can be used in child contracts
    */
    function setOwnership(uint newOwner) internal {
        uint oldOwner = owner;

        owner = newOwner;

        emit OwnershipTransferred(oldOwner, newOwner);
    }

    /*
        @dev Transfer ownership to the new owner
    */
    function transferOwnership(uint newOwner) external onlyOwner {
        require(newOwner != 0, UtilityErrors.INVALID_NEW_OWNER);

        tvm.accept();

        setOwnership(newOwner);
    }
}