// SPDX-License-Identifier: BUSL-1.1
pragma solidity 0.7.6;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

abstract contract Permissions {
    address public governance;
    address public pendingGovernance;
    address internal initializer;

    event GovernanceClaimed(address newGovernance, address previousGovernance);

    event TransferGovernancePending(address pendingGovernance);

    constructor(address _governance) {
        require(_governance != address(0), "ZERO_ADDRESS");
        initializer = msg.sender;
        governance = _governance;
    }

    modifier initialized() {
        require(initializer == address(0), "NOT_INITIALIZED");
        _;
    }

    modifier onlyGovernance() {
        require(msg.sender == governance, "ONLY_GOVERNANCE");
        _;
    }

    /**
     * @dev Allows the pendingGovernance address to finalize the change governance process.
     */
    function claimGovernance() public {
        require(pendingGovernance == msg.sender, "WRONG_GOVERNANCE");
        emit GovernanceClaimed(pendingGovernance, governance);
        governance = pendingGovernance;
        pendingGovernance = address(0);
    }

    /**
     * @dev Allows the current governance to set the pendingGovernance address.
     * @param _governance The address to transfer ownership to.
     */
    function transferGovernance(address _governance) public onlyGovernance {
        require(_governance != address(0), "ZERO_ADDRESS");
        pendingGovernance = _governance;

        emit TransferGovernancePending(pendingGovernance);
    }
}