/*

    Copyright 2020 DODO ZOO.
    SPDX-License-Identifier: Apache-2.0

*/

pragma solidity 0.6.9;
pragma experimental ABIEncoderV2;

/**
 * @title Ownable
 * @author DODO Breeder
 *
 * @notice Ownership related functions
 */
contract Ownable {
    address public _OWNER_;

    // ============ Events ============

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

    // ============ Modifiers ============

    modifier onlyOwner() {
        require(msg.sender == _OWNER_, "NOT_OWNER");
        _;
    }

    // ============ Functions ============

    constructor() internal {
        _OWNER_ = msg.sender;
        emit OwnershipTransferred(address(0), _OWNER_);
    }

    function transferOwnership(address newOwner) external onlyOwner {
        require(newOwner != address(0), "INVALID_OWNER");
        emit OwnershipTransferred(_OWNER_, newOwner);
        _OWNER_ = newOwner;
    }
}