contract Owned {

    address public owner;
    address public newOwnerCandidate;

    event OwnershipRequested(address indexed by, address indexed to);
    event OwnershipTransferred(address indexed from, address indexed to);
    event OwnershipRemoved();

    /// @dev The constructor sets the `msg.sender` as the`owner` of the contract
    function Owned() {
        owner = msg.sender;
    }

    /// @dev `owner` is the only address that can call a function with this
    /// modifier
    modifier onlyOwner() {
        require (msg.sender == owner);
        _;
    }
    
    /// @dev In this 1st option for ownership transfer `proposeOwnership()` must
    ///  be called first by the current `owner` then `acceptOwnership()` must be
    ///  called by the `newOwnerCandidate`
    /// @notice `onlyOwner` Proposes to transfer control of the contract to a
    ///  new owner
    /// @param _newOwnerCandidate The address being proposed as the new owner
    function proposeOwnership(address _newOwnerCandidate) onlyOwner {
        newOwnerCandidate = _newOwnerCandidate;
        OwnershipRequested(msg.sender, newOwnerCandidate);
    }

    /// @notice Can only be called by the `newOwnerCandidate`, accepts the
    ///  transfer of ownership
    function acceptOwnership() {
        require(msg.sender == newOwnerCandidate);

        address oldOwner = owner;
        owner = newOwnerCandidate;
        newOwnerCandidate = 0x0;

        OwnershipTransferred(oldOwner, owner);
    }

    /// @dev In this 2nd option for ownership transfer `changeOwnership()` can
    ///  be called and it will immediately assign ownership to the `newOwner`
    /// @notice `owner` can step down and assign some other address to this role
    /// @param _newOwner The address of the new owner
    function changeOwnership(address _newOwner) onlyOwner {
        require(_newOwner != 0x0);

        address oldOwner = owner;
        owner = _newOwner;
        newOwnerCandidate = 0x0;

        OwnershipTransferred(oldOwner, owner);
    }

    /// @dev In this 3rd option for ownership transfer `removeOwnership()` can
    ///  be called and it will immediately assign ownership to the 0x0 address;
    ///  it requires a 0xdece be input as a parameter to prevent accidental use
    /// @notice Decentralizes the contract, this operation cannot be undone 
    /// @param _dac `0xdac` has to be entered for this function to work
    function removeOwnership(uint _dac) onlyOwner {
        require(_dac == 0xdac);
        owner = 0x0;
        newOwnerCandidate = 0x0;
        OwnershipRemoved();     
    }
}
/// @title Owned
/// @author Adrià Massanet <adria@codecontext.io>
/// @notice The Owned contract has an owner address, and provides basic 
///  authorization control functions, this simplifies & the implementation of
///  user permissions; this contract has three work flows for a change in
///  ownership, the first requires the new owner to validate that they have the
///  ability to accept ownership, the second allows the ownership to be
///  directly transfered without requiring acceptance, and the third allows for
///  the ownership to be removed to allow for decentralization 
function changeOwnership(address _newOwner) onlyOwner {
    require(_newOwner != 0x0);

    address oldOwner = owner;
    owner = _newOwner;
    newOwnerCandidate = 0x0;

    OwnershipTransferred(oldOwner, owner);
}

/// @dev In this 2nd option for ownership transfer `changeOwnership()` can
///  be called and it will immediately assign ownership to the `newOwner`
/// @notice `owner` can step down and assign some other address to this role
/// @param _newOwner The address of the new owner