Random3-part2.sol

pragma solidity ^0.8.0;

contract RandomNumbers{
  // Result varibles
  uint256[] public winnerNumbers;
  uint256 public rollCount;
  function random(uint256 maxNumber) public view returns (uint256) {
        /**
        Generates a random number between 0 and maxNumber. Uses current block difficulty, timestamp, caller address, and the blockhash of the block when prepareRandom has been called.
        Although the output of this function can be precalculated, the manager not knowing the blockhash of the block they called "prepareRandom" makes the system fair.
         */
        return
            uint256(blockhash(preparationBlockNumber)) % maxNumber;
    }

    function roll(uint256 maxNumber) public onlyOwner {
        require(
            canCallRandom,
            "You need to prepare the random before calling it."
        );
        canCallRandom = false;
        winnerNumbers.push(random(maxNumber));
        rollCount++;
    }
}