contract DelegatedTokenLogic is Ownable, DelegatedERC20 {
    using SafeMath for uint256;

    address public capTables;
    address public front;

    /**
    * @Dev Index of this security in the global cap table store.
    */
    uint256 public index;

    mapping (address => mapping (address => uint256)) internal allowed;

    modifier onlyFront() {
        require(msg.sender == front, "this method is reserved for the token front");
        _;
    }

    /**
    * @dev Set the fronting token.
    */
    function setFront(address _front) public onlyOwner {
        front = _front;
    }

    /**
    * @dev total number of tokens in existence
    */
    function totalSupply() public view returns (uint256) {
        return ICapTables(capTables).totalSupply(index);
    }

    /**
    * @dev transfer token for a specified address
    * @param _to The address to transfer to.
    * @param _value The amount to be transferred.
    */
    function transfer(address _to, uint256 _value, address sender) 
        public 
        onlyFront 
        returns (bool) 
    {
        require(_to != address(0), "tokens MUST NOT be transferred to the zero address");
        ICapTables(capTables).transfer(index, sender, _to, _value);
        return true;
    }

    /**
    * @dev Gets the balance of the specified address.
    * @param _owner The address to query the the balance of.
    * @return An uint256 representing the amount owned by the passed address.
    */
    function balanceOf(address _owner) public view returns (uint256 balance) {
        return ICapTables(capTables).balanceOf(index, _owner);
    }
    /**
    * @dev Transfer tokens from one address to another
    * @param _from address The address which you want to send tokens from
    * @param _to address The address which you want to transfer to
    * @param _value uint256 the amount of tokens to be transferred
    */
    function transferFrom(address _from, address _to, uint256 _value, address sender) 
        public 
        onlyFront
        returns (bool) 
    {
        require(_to != address(0), "tokens MUST NOT go to the zero address");
        require(_value <= allowed[_from][sender], "transfer value MUST NOT exceed allowance");

        ICapTables(capTables).transfer(index, _from, _to, _value);
        allowed[_from][sender] = allowed[_from][sender].sub(_value);
        return true;
    }

    /**
    * @dev Approve the passed address to spend the specified amount of tokens on behalf of sender.
    *
    * Beware that changing an allowance with this method brings the risk that someone may use both the old
    * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
    * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
    * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
    * @param _spender The address which will spend the funds.
    * @param _value The amount of tokens to be spent.
    */
    function approve(address _spender, uint256 _value, address sender) 
        public 
        onlyFront
        returns (bool) 
    {
        allowed[sender][_spender] = _value;
        return true;
    }

    /**
    * @dev Function to check the amount of tokens that an owner allowed to a spender.
    * @param _owner address The address which owns the funds.
    * @param _spender address The address which will spend the funds.
    * @return A uint256 specifying the amount of tokens still available for the spender.
    */
    function allowance(address _owner, address _spender) public view returns (uint256) {
        return allowed[_owner][_spender];
    }

}
/**
 * @title DelegatedTokenLogic empty token
 */
function approve(address _spender, uint256 _value, address sender) 
        public 
        onlyFront
        returns (bool) 
    {
        allowed[sender][_spender] = _value;
        return true;
    }
/**
 * @dev Approve the passed address to spend the specified amount of tokens on behalf of sender.
 *
 * Beware that changing an allowance with this method brings the risk that someone may use both the old
 * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
 * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
 * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
 * @param _spender The address which will spend the funds.
 * @param _value The amount of tokens to be spent.
 */