tic_tac_toe.sol

pragma solidity 0.7.4;
contract YourContract {
  enum Choice { Rock, Paper, Scissors }

  uint256 public challenge_count = 0;  
  mapping(uint256 => address payable) public challenger_addresses;
  mapping(uint256 => address payable) public challenged_addresses;
  mapping(uint256 => uint256) public bets;
  mapping(uint256 => Choice) private challenger_choices;
  mapping(uint256 => Choice) private challenged_choices;
  mapping(uint256 => bool) private is_finished;

  // Private functions

  function challenge(address payable challenged, Choice choice, uint256 bet) public payable
  {
    require(msg.value == bet);
    challenge_count += 1;
    challenger_addresses[challenge_count] = msg.sender;
    challenged_addresses[challenge_count] = challenged;
    bets[challenge_count] = bet;
    challenger_choices[challenge_count] = choice;
  }

  function answerChallenge(uint256 challenge_id, Choice choice) public payable
  {
    require(msg.value == bets[challenge_id]);
    require(msg.sender == challenged_addresses[challenge_id]);
    challenged_choices[challenge_id] = choice;
    is_finished[challenge_id] = true;

    if(isTie(challenger_choices[challenge_id], challenged_choices[challenge_id]))
    {
      challenger_addresses[challenge_id].transfer(bets[challenge_id]);
      challenged_addresses[challenge_id].transfer(bets[challenge_id]);
    }else if (challengerWon(challenger_choices[challenge_id], challenged_choices[challenge_id]))
    {
      challenger_addresses[challenge_id].transfer(2*bets[challenge_id]);
    }else
    {
      challenged_addresses[challenge_id].transfer(2*bets[challenge_id]);
    }
  }

  // View functions

  function getChallenger(uint256 hackathon_id) public view returns(address challenger_address)
  {
    return challenger_addresses[hackathon_id];
  }

  function getChallenged(uint256 hackathon_id) public view returns(address challenged_address)
  {
    return challenged_addresses[hackathon_id];
  }

  function getBet(uint256 hackathon_id) public view returns(uint bet)
  {
    return bets[hackathon_id];
  }

  function getChallengerChoice(uint256 hackathon_id) public view returns(Choice challenger_choice)
  {
    require(is_finished[hackathon_id]);
    return challenger_choices[hackathon_id];
  }

  function getChallengedChoice(uint256 hackathon_id) public view returns(Choice challenged_choice)
  {
    return challenged_choices[hackathon_id];
  }

  // Private functions
  
  function challengerWon(Choice challenger_choice, Choice challenged_choice) private pure returns (bool)
  {
    return (challenger_choice == Choice.Rock && challenged_choice == Choice.Scissors)
      || (challenger_choice == Choice.Paper && challenged_choice == Choice.Rock)
      || (challenger_choice == Choice.Scissors && challenged_choice == Choice.Paper);
  }

  function isTie(Choice challenger_choice, Choice challenged_choice) private pure returns (bool)
  {
    return challenger_choice == challenged_choice;
  }
}