if (user.amount > 0) {
    uint256 pending = (user.amount * accRJoePerShare) /
        PRECISION -
        user.rewardDebt;
    _safeRJoeTransfer(msg.sender, pending);
}
user.amount = user.amount + _amount;
user.rewardDebt = (user.amount * accRJoePerShare) / PRECISION;
