Game

pragma solidity >=0.4.22 <0.6.0;

contract RockPaperScissorsSimpleGame {
    enum Choice {
        Rock, // 0
        Paper, // 1
        Scissor // 2
    }

    bool public isDraw;
    address public winner;
    uint256 count;

    struct GamePlayer {
        address playeraddress;
        Choice choice;
        uint256 time;
    }

    GamePlayer[2] playerlist;

    mapping(address => uint256) users; // mapping users register information

    constructor() public {
        isDraw = false;
    }

    function addPlayer() public payable {
        // one player can only register once
        require(users[msg.sender] == 0);
        // only two player can register
        require(count < 2, "only open for two players");
        // register the msg.sender address
        playerlist[count].playeraddress = msg.sender;
        // player registration times plus 1
        users[msg.sender]++;
        count++;
    }

    function input(Choice _choice) public {
        // compare the players choices
        uint8 currentPlayer;
        // Only registered player can input choice
        require(
            registerCheck(msg.sender),
            "Only available for registered player"
        );

        if (playerlist[currentPlayer].playeraddress == msg.sender) {
            // check the current player is the registered player 1
            /* if current player has already input choice, 
            he need to wait for other player which means that a player can only input one choice in one time */
            require(
                playerlist[currentPlayer].time <= playerlist[currentPlayer + 1].time,
                "Waiting "
            );
            // store the choice, player play time plus 1
            playerlist[currentPlayer].choice = _choice;
            playerlist[currentPlayer].time++;
        } else if (playerlist[currentPlayer + 1].playeraddress == msg.sender) {
            // check the current player is the registered player 2
            require(
                playerlist[currentPlayer + 1].time <= playerlist[currentPlayer].time,
                "Waiting "
            );
            // store the choice, player play time plus 1
            playerlist[currentPlayer + 1].choice = _choice;
            playerlist[currentPlayer + 1].time++;
        }
        // two players have the same play time which means that they all input their choice
        if (playerlist[currentPlayer].time == playerlist[currentPlayer + 1].time) {
            // check the winner
            winner = winning(playerlist[currentPlayer].choice, playerlist[currentPlayer + 1].choice);
        }
    }

    function winning(Choice _a, Choice _b) public returns (address) {
        address winner_address;
        // a is player1, b is player2
        if (_a == _b) {
            // If the players make the same choice, set isDraw as true
            isDraw = true;
            // If the game is draw, set winner address as 0
            winner_address = 0x0000000000000000000000000000000000000000;
        } else if (_a == Choice.Rock && _b == Choice.Scissor) {
            // Rock > Scissor, player 1 win
            winner_address = playerlist[0].playeraddress;
        } else if (_a == Choice.Scissor && _b == Choice.Paper) {
            // Scissor > Paper, player 1 win
            winner_address = playerlist[0].playeraddress;
        } else if (_a == Choice.Paper && _b == Choice.Rock) {
            // Paper > Rock, player 1 win
            winner_address = playerlist[0].playeraddress;
        } else if (_b == Choice.Rock && _a == Choice.Scissor) {
            // Rock > Scissor, player 2 win
            winner_address = playerlist[1].playeraddress;
        } else if (_b == Choice.Scissor && _a == Choice.Paper) {
            // Scissor > Paper, player 2 win
            winner_address = playerlist[1].playeraddress;
        } else if (_b == Choice.Paper && _a == Choice.Rock) {
            // Paper > Rock, player 2 win
            winner_address = playerlist[1].playeraddress;
        }
        return winner_address;
    }

    function registerCheck(address _address) public view returns (bool) {
        // Check if the player is registered
        if (_address == playerlist[0].playeraddress || _address == playerlist[1].playeraddress) {
            return true;
        // Not registered player cannot play the game
        } else {
            return false;
        }
    }

}