gistfile1.txt

//
// GuessToWin.solpp
//
// Simple contract allowing anyone to guess secret passwords. If they guess any right, they
// will be awarded an amount of Vite based on the amount funded to the contract.
//
// Contract initially has no rewards balances stored. Any user can create rewards for a guess
// by calling the Fund function and providing the appropriate hash of the secret guess they
// would like to award, along with a patment of the amount of Vite they want to fund the award with.
//
// The hash of the guesses can be generated via the shell command:
// echo -n YOURSECRETPASSWORD | b2sum -l 256
//
// Guesses are submitted by sending a string of the guess to the Guess function. Correct
// guessers are awarded the entire fund for that hash/guess pair
//
// Warning: If you send funds with a hash value of an unknown string, those funds will be
// permanently locked in the contract! Also be warned that all guesses/hashes are logged
// into the ledger, so testing a particular hash/guess combination permanently reveals it.
// It's good to test this with a known hash/guess and a small value first, before putting
// in a larger reward with a truly secret hash/guess.
//
// Example:
// Fund() with 10 Vite and the 32 byte hash "324dcf027dd4a30a932c441f365a25e86b173defa4b8e58948253471b81b72cf"
// Guess() with 0 Vite and the string "hello"

pragma soliditypp ^0.4.2;

contract GuessToWin {
   // use Vite as token for funding and rewards, for ids see https://vitescan.io/tokens
   tokenId token = tokenId("tti_5649544520544f4b454e6e40");

   // mapping from hashes of correct guesses to the reward balance for that guess.
   mapping(bytes32 => uint) public balances;

   // events
   event Funded(address indexed addr, uint256 amount, bytes32 hashval, string log);
   event Awarded(address indexed addr, uint256 amount, string guess, string log);
   event Failed(address indexed addr, uint256 amount, string guess, string log);

   // function for creating and funding awards, must send Vite and provide hash of secret as argument.
   onMessage Fund(bytes32 hashval) payable {
      require(msg.tokenid == token);// "Please send vite rewards only.");
      require(msg.amount > 0);// "Must send tokens to fund award.");
      balances[hashval] += msg.amount;
      emit Funded(msg.sender, msg.amount, hashval, "Funded!");
   }

   onMessage Guess(string calldata body) {
      // here we encode and hash the input string and check if an award fund/balance
      // exists for this hashed string.
      bytes32 hashval = blake2b(abi.encodePacked(body));
      if( balances[hashval] > 0 ) {
         // Note: The following order of the transfer and the setting balances to zero
         // would expose a Solidity contract to reentrancy attacks, but this NOT an
         // issue in Solidity++ due to async design. Also easier to write this way.
         msg.sender.transfer(token, balances[hashval]);
         emit Awarded(msg.sender, balances[hashval], body, "Correct!");// guess! Awarded!");
         balances[hashval] = 0;
      } else {
         emit Failed(msg.sender, 0, body, "Try again!");
      }
   }

}