reveal.sol

pragma solidity >=0.8.0 <0.9.0;

/**
 * @notice Function for players to reveal their choice. The first player to reveal sets a deadline for the second player
 * this is prevent players for abandoning the game once they know they have lost based on the revealed hash.
 * At the end of the deadline, the player who committed can trigger a "win-by-default".
 * If both players reveal in time, the second player's reveal will call determineWinner() and advance the game to the result phase
 * @notice Unlike commit, players can only reveal once
 * @param salt - a player chosen secret string from the "commit" phase used to prove their choice via a hash match
 */
function reveal(string memory salt)
    public
    validGameState(activeGame[msg.sender], GameState.RevealPhase)
{
    // Get the game hash from active game mapping
    address gameHash = activeGame[msg.sender];

    bool isPlayer1 = games[gameHash].player1 == msg.sender;
    // Check that player hasn't already revealed
    if (isPlayer1) {
        require(games[gameHash].reveal1 == 0, "Already revealed");
    } else {
        require(games[gameHash].reveal2 == 0, "Already revealed");
    }

    // Verify that one of the choices + salt hashes matches commit hash
    // Compare all three possible choices so they don't have to enter their choice again
    bytes32 verificationHashRock = keccak256(abi.encodePacked("rock", salt));
    bytes32 verificationHashPaper = keccak256(abi.encodePacked("paper", salt));
    bytes32 verificationHashScissors = keccak256(
        abi.encodePacked("scissors", salt)
    );

    bytes32 commitHash = isPlayer1
        ? games[gameHash].commit1
        : games[gameHash].commit2;

    require(
        verificationHashRock == commitHash ||
            verificationHashPaper == commitHash ||
            verificationHashScissors == commitHash,
        "Reveal hash doesn't match commit hash. Salt not the same as commit."
    );

    // Work backwards to infer their choice
    string memory choice;
    if (verificationHashRock == commitHash) {
        choice = "rock";
    } else if (verificationHashPaper == commitHash) {
        choice = "paper";
    } else {
        choice = "scissors";
    }

    // Save the revealed hash w/o salt
    if (isPlayer1) {
        games[gameHash].reveal1 = keccak256(abi.encodePacked(choice));
    } else {
        games[gameHash].reveal2 = keccak256(abi.encodePacked(choice));
    }

    // if both players revealed, determine winner
    if (games[gameHash].reveal1 != 0 && games[gameHash].reveal2 != 0) {
        games[gameHash].gameResult = determineWinner(
            games[gameHash].reveal1,
            games[gameHash].reveal2
        );
        games[gameHash].gameState = GameState.ResultPhase;
    } else {
        // Set deadline for other player to reveal
        games[gameHash].revealDeadline = block.timestamp + 3 minutes;
    }
}