// SPDX-License-Identifier: GPL-3.0-or-later

/**

Author: CoFiX Core, https://cofix.io
Commit hash: v0.9.3-1-g68dc8fd
Repository: https://github.com/Computable-Finance/CoFiX
Issues: https://github.com/Computable-Finance/CoFiX/issues

*/

pragma solidity 0.6.12;


// 
/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// 
// helper methods for interacting with ERC20 tokens and sending ETH that do not consistently return true/false
library TransferHelper {
    function safeApprove(address token, address to, uint value) internal {
        // bytes4(keccak256(bytes('approve(address,uint256)')));
        (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0x095ea7b3, to, value));
        require(success && (data.length == 0 || abi.decode(data, (bool))), 'TransferHelper: APPROVE_FAILED');
    }

    function safeTransfer(address token, address to, uint value) internal {
        // bytes4(keccak256(bytes('transfer(address,uint256)')));
        (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0xa9059cbb, to, value));
        require(success && (data.length == 0 || abi.decode(data, (bool))), 'TransferHelper: TRANSFER_FAILED');
    }

    function safeTransferFrom(address token, address from, address to, uint value) internal {
        // bytes4(keccak256(bytes('transferFrom(address,address,uint256)')));
        (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0x23b872dd, from, to, value));
        require(success && (data.length == 0 || abi.decode(data, (bool))), 'TransferHelper: TRANSFER_FROM_FAILED');
    }

    function safeTransferETH(address to, uint value) internal {
        (bool success,) = to.call{value:value}(new bytes(0));
        require(success, 'TransferHelper: ETH_TRANSFER_FAILED');
    }
}

// 
/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }
}

// 
/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor () internal {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// 
interface ICoFiXStakingRewards {
    // Views

    /// @dev The rewards vault contract address set in factory contract
    /// @return Returns the vault address
    function rewardsVault() external view returns (address);

    /// @dev The lastBlock reward applicable
    /// @return Returns the latest block.number on-chain
    function lastBlockRewardApplicable() external view returns (uint256);

    /// @dev Reward amount represents by per staking token
    function rewardPerToken() external view returns (uint256);

    /// @dev How many reward tokens a user has earned but not claimed at present
    /// @param  account The target account
    /// @return The amount of reward tokens a user earned
    function earned(address account) external view returns (uint256);

    /// @dev How many reward tokens accrued recently
    /// @return The amount of reward tokens accrued recently
    function accrued() external view returns (uint256);

    /// @dev Get the latest reward rate of this mining pool (tokens amount per block)
    /// @return The latest reward rate
    function rewardRate() external view returns (uint256);

    /// @dev How many stakingToken (XToken) deposited into to this reward pool (mining pool)
    /// @return The total amount of XTokens deposited in this mining pool
    function totalSupply() external view returns (uint256);

    /// @dev How many stakingToken (XToken) deposited by the target account
    /// @param  account The target account
    /// @return The total amount of XToken deposited in this mining pool
    function balanceOf(address account) external view returns (uint256);

    /// @dev Get the address of token for staking in this mining pool
    /// @return The staking token address
    function stakingToken() external view returns (address);

    /// @dev Get the address of token for rewards in this mining pool
    /// @return The rewards token address
    function rewardsToken() external view returns (address);

    // Mutative

    /// @dev Stake/Deposit into the reward pool (mining pool)
    /// @param  amount The target amount
    function stake(uint256 amount) external;

    /// @dev Stake/Deposit into the reward pool (mining pool) for other account
    /// @param  other The target account
    /// @param  amount The target amount
    function stakeForOther(address other, uint256 amount) external;

    /// @dev Withdraw from the reward pool (mining pool), get the original tokens back
    /// @param  amount The target amount
    function withdraw(uint256 amount) external;

    /// @dev Withdraw without caring about rewards. EMERGENCY ONLY.
    function emergencyWithdraw() external;

    /// @dev Claim the reward the user earned
    function getReward() external;

    function getRewardAndStake() external;

    /// @dev User exit the reward pool, it's actually withdraw and getReward
    function exit() external;

    /// @dev Add reward to the mining pool
    function addReward(uint256 amount) external;

    // Events
    event RewardAdded(address sender, uint256 reward);
    event Staked(address indexed user, uint256 amount);
    event StakedForOther(address indexed user, address indexed other, uint256 amount);
    event Withdrawn(address indexed user, uint256 amount);
    event EmergencyWithdraw(address indexed user, uint256 amount);
    event RewardPaid(address indexed user, uint256 reward);
}

// 
interface ICoFiXVaultForLP {

    enum POOL_STATE {INVALID, ENABLED, DISABLED}

    event NewPoolAdded(address pool, uint256 index);
    event PoolEnabled(address pool);
    event PoolDisabled(address pool);

    function setGovernance(address _new) external;
    function setInitCoFiRate(uint256 _new) external;
    function setDecayPeriod(uint256 _new) external;
    function setDecayRate(uint256 _new) external;

    function addPool(address pool) external;
    function enablePool(address pool) external;
    function disablePool(address pool) external;
    function setPoolWeight(address pool, uint256 weight) external;
    function batchSetPoolWeight(address[] memory pools, uint256[] memory weights) external;
    function distributeReward(address to, uint256 amount) external;

    function getPendingRewardOfLP(address pair) external view returns (uint256);
    function currentPeriod() external view returns (uint256);
    function currentCoFiRate() external view returns (uint256);
    function currentPoolRate(address pool) external view returns (uint256 poolRate);
    function currentPoolRateByPair(address pair) external view returns (uint256 poolRate);

    /// @dev Get the award staking pool address of pair (XToken)
    /// @param  pair The address of XToken(pair) contract
    /// @return pool The pool address
    function stakingPoolForPair(address pair) external view returns (address pool);

    function getPoolInfo(address pool) external view returns (POOL_STATE state, uint256 weight);
    function getPoolInfoByPair(address pair) external view returns (POOL_STATE state, uint256 weight);

    function getEnabledPoolCnt() external view returns (uint256);

    function getCoFiStakingPool() external view returns (address pool);

}

// 
/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// 
interface ICoFiStakingRewards {
    // Views

    /// @dev Reward amount represents by per staking token
    function rewardPerToken() external view returns (uint256);

    /// @dev How many reward tokens a user has earned but not claimed at present
    /// @param  account The target account
    /// @return The amount of reward tokens a user earned
    function earned(address account) external view returns (uint256);

    /// @dev How many reward tokens accrued recently
    /// @return The amount of reward tokens accrued recently
    function accrued() external view returns (uint256);

    /// @dev How many stakingToken (XToken) deposited into to this reward pool (staking pool)
    /// @return The total amount of XTokens deposited in this staking pool
    function totalSupply() external view returns (uint256);

    /// @dev How many stakingToken (XToken) deposited by the target account
    /// @param  account The target account
    /// @return The total amount of XToken deposited in this staking pool
    function balanceOf(address account) external view returns (uint256);

    /// @dev Get the address of token for staking in this staking pool
    /// @return The staking token address
    function stakingToken() external view returns (address);

    /// @dev Get the address of token for rewards in this staking pool
    /// @return The rewards token address
    function rewardsToken() external view returns (address);

    // Mutative

    /// @dev Stake/Deposit into the reward pool (staking pool)
    /// @param  amount The target amount
    function stake(uint256 amount) external;

    /// @dev Stake/Deposit into the reward pool (staking pool) for other account
    /// @param  other The target account
    /// @param  amount The target amount
    function stakeForOther(address other, uint256 amount) external;

    /// @dev Withdraw from the reward pool (staking pool), get the original tokens back
    /// @param  amount The target amount
    function withdraw(uint256 amount) external;
    
    /// @dev Withdraw without caring about rewards. EMERGENCY ONLY.
    function emergencyWithdraw() external;

    /// @dev Claim the reward the user earned
    function getReward() external;

    /// @dev Add ETH reward to the staking pool
    function addETHReward() external payable;

    /// @dev User exit the reward pool, it's actually withdraw and getReward
    function exit() external;

    // Events
    event Staked(address indexed user, uint256 amount);
    event StakedForOther(address indexed user, address indexed other, uint256 amount);
    event Withdrawn(address indexed user, uint256 amount);
    event SavingWithdrawn(address indexed to, uint256 amount);
    event EmergencyWithdraw(address indexed user, uint256 amount);
    event RewardPaid(address indexed user, uint256 reward);
    
}

// 
interface ICoFiXFactory {
    // All pairs: {ETH <-> ERC20 Token}
    event PairCreated(address indexed token, address pair, uint256);
    event NewGovernance(address _new);
    event NewController(address _new);
    event NewFeeReceiver(address _new);
    event NewVaultForLP(address _new);
    event NewVaultForTrader(address _new);
    event NewVaultForCNode(address _new);

    /// @dev Create a new token pair for trading
    /// @param  token the address of token to trade
    /// @return pair the address of new token pair
    function createPair(
        address token
        )
        external
        returns (address pair);

    function getPair(address token) external view returns (address pair);
    function allPairs(uint256) external view returns (address pair);
    function allPairsLength() external view returns (uint256);

    function getTradeMiningStatus(address token) external view returns (bool status);
    function setTradeMiningStatus(address token, bool status) external;

    function setGovernance(address _new) external;
    function setController(address _new) external;
    function setFeeReceiver(address _new) external;
    function setVaultForLP(address _new) external;
    function setVaultForTrader(address _new) external;
    function setVaultForCNode(address _new) external;
    function getController() external view returns (address controller);
    function getFeeReceiver() external view returns (address feeReceiver);
    function getVaultForLP() external view returns (address vaultForLP);
    function getVaultForTrader() external view returns (address vaultForTrader);
    function getVaultForCNode() external view returns (address vaultForCNode);
}

// 
// Stake XToken to earn CoFi Token
contract CoFiXStakingRewards is ICoFiXStakingRewards, ReentrancyGuard {
    using SafeMath for uint256;

    /* ========== STATE VARIABLES ========== */

    address public override rewardsToken; // CoFi
    address public override stakingToken; // XToken or CNode

    address public factory;

    uint256 public lastUpdateBlock;
    uint256 public rewardPerTokenStored;

    mapping(address => uint256) public userRewardPerTokenPaid;
    mapping(address => uint256) public rewards;

    uint256 private _totalSupply;
    mapping(address => uint256) private _balances;

    /* ========== CONSTRUCTOR ========== */

    constructor(
        address _rewardsToken,
        address _stakingToken,
        address _factory
    ) public {
        rewardsToken = _rewardsToken;
        stakingToken = _stakingToken;
        require(ICoFiXFactory(_factory).getVaultForLP() != address(0), "VaultForLP not set yet"); // check
        factory = _factory;
        lastUpdateBlock = block.number;        
    }

    /* ========== VIEWS ========== */

    // replace cofixVault with rewardsVault, this could introduce more calls, but clear is more important 
    function rewardsVault() public virtual override view returns (address) {
        return ICoFiXFactory(factory).getVaultForLP();
    }

    function totalSupply() external override view returns (uint256) {
        return _totalSupply;
    }

    function balanceOf(address account) external override view returns (uint256) {
        return _balances[account];
    }

    function lastBlockRewardApplicable() public override view returns (uint256) {
        return block.number;
    }

    function rewardPerToken() public override view returns (uint256) {
        if (_totalSupply == 0) {
            return rewardPerTokenStored;
        }
        return
            rewardPerTokenStored.add(
                accrued().mul(1e18).div(_totalSupply)
            );
    }

    function _rewardPerTokenAndAccrued() internal view returns (uint256, uint256) {
        if (_totalSupply == 0) {
            // use the old rewardPerTokenStored, and accrued should be zero here
            // if not the new accrued amount will never be distributed to anyone
            return (rewardPerTokenStored, 0);
        }
        uint256 _accrued = accrued();
        uint256 _rewardPerToken = rewardPerTokenStored.add(
                _accrued.mul(1e18).div(_totalSupply)
            );
        return (_rewardPerToken, _accrued);
    }

    function rewardRate() public virtual override view returns (uint256) {
        return ICoFiXVaultForLP(rewardsVault()).currentPoolRate(address(this));
    }

    function accrued() public virtual override view returns (uint256) {
        // calc block rewards
        uint256 blockReward = lastBlockRewardApplicable().sub(lastUpdateBlock).mul(rewardRate());
        // query pair trading rewards
        uint256 tradingReward = ICoFiXVaultForLP(rewardsVault()).getPendingRewardOfLP(stakingToken);
        return blockReward.add(tradingReward);
    }

    function earned(address account) public override view returns (uint256) {
        return _balances[account].mul(rewardPerToken().sub(userRewardPerTokenPaid[account])).div(1e18).add(rewards[account]);
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    function stake(uint256 amount) external override nonReentrant updateReward(msg.sender) {
        require(amount > 0, "Cannot stake 0");
        _totalSupply = _totalSupply.add(amount);
        _balances[msg.sender] = _balances[msg.sender].add(amount);
        TransferHelper.safeTransferFrom(stakingToken, msg.sender, address(this), amount);
        emit Staked(msg.sender, amount);
    }

    function stakeForOther(address other, uint256 amount) external override nonReentrant updateReward(other) {
        require(amount > 0, "Cannot stake 0");
        _totalSupply = _totalSupply.add(amount);
        _balances[other] = _balances[other].add(amount);
        TransferHelper.safeTransferFrom(stakingToken, msg.sender, address(this), amount);
        emit StakedForOther(msg.sender, other, amount);
    }

    function withdraw(uint256 amount) public override nonReentrant updateReward(msg.sender) {
        require(amount > 0, "Cannot withdraw 0");
        _totalSupply = _totalSupply.sub(amount);
        _balances[msg.sender] = _balances[msg.sender].sub(amount);
        TransferHelper.safeTransfer(stakingToken, msg.sender, amount);
        emit Withdrawn(msg.sender, amount);
    }

    // Withdraw without caring about rewards. EMERGENCY ONLY.
    function emergencyWithdraw() external override nonReentrant {
        uint256 amount = _balances[msg.sender];
        require(amount > 0, "Cannot withdraw 0");
        _totalSupply = _totalSupply.sub(amount);
        _balances[msg.sender] = 0;
        rewards[msg.sender] = 0;
        TransferHelper.safeTransfer(stakingToken, msg.sender, amount);
        emit EmergencyWithdraw(msg.sender, amount);
    }

    function getReward() public override nonReentrant updateReward(msg.sender) {
        uint256 reward = rewards[msg.sender];
        if (reward > 0) {
            rewards[msg.sender] = 0;
            // TransferHelper.safeTransfer(rewardsToken, msg.sender, reward);
            uint256 transferred = _safeCoFiTransfer(msg.sender, reward);
            emit RewardPaid(msg.sender, transferred);
        }
    }

    // get CoFi rewards and staking into CoFiStakingRewards pool
    function getRewardAndStake() external override nonReentrant updateReward(msg.sender) {
        uint256 reward = rewards[msg.sender];
        if (reward > 0) {
            rewards[msg.sender] = 0;
            address cofiStakingPool = ICoFiXVaultForLP(rewardsVault()).getCoFiStakingPool(); // also work for VaultForCNode
            require(cofiStakingPool != address(0), "cofiStakingPool not set");
            // approve to staking pool
            address _rewardsToken = rewardsToken;
            IERC20(_rewardsToken).approve(cofiStakingPool, reward);
            ICoFiStakingRewards(cofiStakingPool).stakeForOther(msg.sender, reward);
            IERC20(_rewardsToken).approve(cofiStakingPool, 0); // ensure
            emit RewardPaid(msg.sender, reward);
        }
    }

    function exit() external override {
        withdraw(_balances[msg.sender]);
        getReward();
    }

    // add reward from trading pool or anyone else
    function addReward(uint256 amount) public override nonReentrant updateReward(address(0)) {
        // transfer from caller (router contract)
        TransferHelper.safeTransferFrom(rewardsToken, msg.sender, address(this), amount);
        // update rewardPerTokenStored
        rewardPerTokenStored = rewardPerTokenStored.add(amount.mul(1e18).div(_totalSupply));
        emit RewardAdded(msg.sender, amount);
    }

    // Safe CoFi transfer function, just in case if rounding error or ending of mining causes pool to not have enough CoFis.
    function _safeCoFiTransfer(address _to, uint256 _amount) internal returns (uint256) {
        uint256 cofiBal = IERC20(rewardsToken).balanceOf(address(this));
        if (_amount > cofiBal) {
            _amount = cofiBal;
        }
        TransferHelper.safeTransfer(rewardsToken, _to, _amount); // allow zero amount
        return _amount;
    }

    /* ========== MODIFIERS ========== */

    modifier updateReward(address account) virtual {
        // rewardPerTokenStored = rewardPerToken();
        // uint256 newAccrued = accrued();
        (uint256 newRewardPerToken, uint256 newAccrued) = _rewardPerTokenAndAccrued();
        rewardPerTokenStored = newRewardPerToken;
        if (newAccrued > 0) {
            // distributeReward could fail if CoFiXVaultForLP is not minter of CoFi anymore
            // Should set reward rate to zero first, and then do a settlement of pool reward by call getReward
            ICoFiXVaultForLP(rewardsVault()).distributeReward(address(this), newAccrued);
        } 
        lastUpdateBlock = lastBlockRewardApplicable();
        if (account != address(0)) {
            rewards[account] = earned(account);
            userRewardPerTokenPaid[account] = rewardPerTokenStored;
        }
        _;
    }

    /* ========== EVENTS ========== */

    event RewardAdded(address sender, uint256 reward);
    event Staked(address indexed user, uint256 amount);
    event StakedForOther(address indexed user, address indexed other, uint256 amount);
    event Withdrawn(address indexed user, uint256 amount);
    event EmergencyWithdraw(address indexed user, uint256 amount);
    event RewardPaid(address indexed user, uint256 reward);
}