Option.sol

contract BuyOptionForUNIToken {
  address public constant UNIERC20Address = "0x....";
  
  uint public price;
  uint public endPeriod;
  address public contractHolder;
  
  constructor(uint _price, uint _endPeriod, address _contractHolder) {
    price = _price;
    endPeriod = _endPeriod;
    contractHolder = _contractHolder;
  }
  
  function buy(uint amount) {
    require(msg.sender == contractHolder, "You are not the contract holder");
    require(msg.value >= (amount * price), "Not enough ETH");
    require(block.timestamp < endPeriod, "Contract expired");
    
    ERC20(UNIERC20Address).transfer(msg.sender, amount);
  }
}