// SPDX-License-Identifier: MIT
pragma solidity 0.8.4;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}


/**
 * @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);
}

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain `call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
     * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
     *
     * _Available since v4.8._
     */
    function verifyCallResultFromTarget(
        address target,
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal view returns (bytes memory returnedData) {
        if (success) {
            if (returndata.length == 0) {
                // only check isContract if the call was successful and the return data is empty
                // otherwise we already know that it was a contract
                require(isContract(target), "Address: call to non-contract");
            }
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    /**
     * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason or using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory returnedData) {
        if (success) {
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    function _revert(bytes memory returndata, string memory errorMessage) private pure {
        // Look for revert reason and bubble it up if present
        if (returndata.length > 0) {
            // The easiest way to bubble the revert reason is using memory via assembly
            /// @solidity memory-safe-assembly
            assembly {
                let returndata_size := mload(returndata)
                revert(add(32, returndata), returndata_size)
            }
        } else {
            revert(errorMessage);
        }
    }
}


/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender) + value;
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender) - value;
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}


/**
 * @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].
 */
abstract 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 () {
        _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 IERC20Metadata is IERC20 {
    function decimals() external view returns (uint8);
}

contract MultiRewardPool is Ownable, ReentrancyGuard {
    using SafeERC20 for IERC20Metadata;

    IERC20Metadata public immutable stakingToken;
    uint256 public immutable stakingTokenMultiplier;
    uint256 public immutable devFee;    // 100 = 1%
    uint256 public immutable tokenFee;  // 100 = 1%
    uint256 public totalSupply;         // Returns the total staked tokens on the contract

    address public treasury;    // The address to receive devFee

    struct PoolInfo {
        IERC20Metadata rewardToken;
        uint256 rewardPoolID;
        uint256 duration;
        uint256 periodFinish;
        uint256 startTime;
        uint256 lastUpdateTime;
        uint256 rewardRate;
        uint256 rewardPerTokenStored;
    }

    struct UserRewardInfo {
        uint256 rewards;
        uint256 userRewardPerTokenPaid;
    }

    PoolInfo[] public poolInfo;

    mapping(address => uint256) internal _balances;
    mapping(address => bool) public addedRewardTokens;
    mapping(uint256 => mapping(address => UserRewardInfo)) public rewardsInPool;

    event Withdrawn(address indexed user, uint256 amount);
    event Staked(address indexed user, uint256 amount);
    event RewardPaid(
        address indexed user,
        address rewardToken,
        uint256 rewardAmount
    );
    event RewardPoolAdded(
        uint256 rewardPoolID,
        address rewardTokenAddress
    );
    event RewardPoolStarted(
        uint256 rewardPoolID,
        address rewardTokenAddress,
        uint256 rewardAmount,
        uint256 rewardDuration,
        uint256 rewardPeriodFinish
    );
    event RewardPoolExtended(
        uint256 rewardPoolID,
        address rewardTokenAddress,
        uint256 oldRewardAmount,
        uint256 newRewardAmount,
        uint256 totalRewardAmount,
        uint256 rewardDuration,
        uint256 rewardPeriodFinish
    );

    /// @param _stakingToken The token that can be staked on the contract
    /// @param _treasury The address of the treasury that receives devFee
    /// @param _devFee The fee in percentage to take from staked tokens when withdrawing (100 = 1%)
    /// @param _tokenFee The fee in percentage of any transfer fees for stakingToken (100 = 1%)
    constructor(
        address _stakingToken,
        address _treasury,
        uint256 _devFee,
        uint256 _tokenFee
    )
    {
        require(
            _stakingToken != address(0) &&
                _treasury != address(0),
            "!constructor"
        );
        devFee = _devFee;
        stakingToken = IERC20Metadata(_stakingToken);
        treasury = _treasury;
        tokenFee = _tokenFee;
        stakingTokenMultiplier =
            10**uint256(IERC20Metadata(_stakingToken).decimals());
    }

    /*//////////////////////////////////////////////////////////////
                            POOL LOGIC
    //////////////////////////////////////////////////////////////*/

    /// @dev Updates the rewards a user has earned. Loops through all reward pools
    /// @param account The address of the account to update rewards for
    function updateReward(address account) internal {
        // loop through all reward pools for user
        for (uint256 i = 0; i < poolInfo.length; i++) {
            PoolInfo storage pool = poolInfo[i];

            if (address(pool.rewardToken) == address(0)) {
                continue;
            } else {
                updateRewardPerTokenStored(i);
                rewardsInPool[i][account].rewards = earned(account, i);
                rewardsInPool[i][account].userRewardPerTokenPaid = pool.rewardPerTokenStored;
            }
        }
    }

    /// @dev Updates the amount of rewards to distribute in a reward pool
    /// @param _pid The pool ID of the reward pool to update
    function updateRewardPerTokenStored(uint256 _pid) internal {
        PoolInfo storage pool = poolInfo[_pid];

        pool.rewardPerTokenStored = rewardPerToken(_pid);
        pool.lastUpdateTime = lastTimeRewardsActive(_pid);
    }

    /// @dev Updates the last time the calculations were done for pool rewards of a reward pool
    /// @param _pid The pool ID of the reward pool to get lastUpdateTime
    /// @return The UNIX time that last time pool calculations were done
    function lastTimeRewardsActive(uint256 _pid) public view returns (uint256) {
        PoolInfo storage pool = poolInfo[_pid];
        return Math.min(block.timestamp, pool.periodFinish);
    }

    /// @dev Returns the time that a specified reward pool will end
    /// @param _pid The pool ID of the reward pools end time
    /// @return The UNIX time that pool ID `_pid` will end
    function endTime(uint256 _pid) public view returns (uint256) {
        PoolInfo storage pool = poolInfo[_pid];

        return pool.periodFinish;
    }

    /// @dev Returns the amount of reward pools created
    /// @return The number of reward pools
    function poolLength() public view returns (uint256) {
        return poolInfo.length;
    }

    /// @dev Returns the current rate of rewards per token stored for a reward pool
    /// @param _pid The pool ID of the reward pool to get rewardPerTokenStored 
    /// @return The rewardPerTokenStored of pool ID `_pid`
    function rewardPerToken(uint256 _pid) public view returns (uint256) {
        PoolInfo storage pool = poolInfo[_pid];

        // Do not distribute rewards before startTime.
        if (block.timestamp < pool.startTime) {
            return 0;
        }

        if (totalSupply == 0) {
            return pool.rewardPerTokenStored;
        }

        // The returrn value is time-based on last time the contract had rewards active
        // multiplied by the reward-rate and it's evened out with a division of bonus effective supply.
        return
            pool.rewardPerTokenStored
                + (pool.rewardRate 
                * (lastTimeRewardsActive(_pid) - pool.lastUpdateTime)
                * stakingTokenMultiplier)
                / totalSupply;
    }

    /// @notice The amount of reward tokens that `account` has earned in pool ID `_pid`
    /// @dev Returns the amount of reward tokens claimable by the user at specified reward pool
    /// @param account The address of the user to check
    /// @param _pid The pool ID of the reward pool to check rewards
    /// @return The amount of reward tokens earned
    function earned(address account, uint256 _pid)
        public
        view
        returns (uint256)
    {
        uint256 reward = rewardsInPool[_pid][account].rewards;
        uint256 rewardPerTokenPaid = rewardsInPool[_pid][account].userRewardPerTokenPaid;

        return
            ((_balances[account]
            * (rewardPerToken(_pid) - rewardPerTokenPaid))
            / stakingTokenMultiplier)
            + reward;
    }

    /*//////////////////////////////////////////////////////////////
                            USER FUNCTIONS
    //////////////////////////////////////////////////////////////*/

    /// @notice Stakes `amount` of stakingToken onto the contract
    /// @dev Stakes a users tokens to start earning rewards
    /// @param amount The amount of tokens to stake
    function stake(uint256 amount) public nonReentrant {
        require(amount > 0, "Cannot stake 0");
        updateReward(msg.sender);
        
        // Transfer staking token from caller to contract
        stakingToken.safeTransferFrom(msg.sender, address(this), amount);

        // Increment sender's balances and total supply
        if (tokenFee > 0) {
            uint256 tokenFeeBalance = amount * tokenFee / 10000;
            uint256 stakedBalance = amount - tokenFeeBalance;
            _balances[msg.sender] += stakedBalance;
            totalSupply += stakedBalance;
        } else {
            _balances[msg.sender] += amount;
            totalSupply += amount;
        }

        emit Staked(msg.sender, amount);
    }

    /// @notice Withdraws `amount` of stakingToken from the contract
    /// @dev Withdrawing incurs a fee specified as devFee
    /// @param amount The amount of tokens to withdraw
    function withdraw(uint256 amount) public nonReentrant {
        require(amount > 0, "Cannot withdraw 0");
        updateReward(msg.sender);

        // Reduce sender's balances and total supply
        totalSupply -= amount;
        _balances[msg.sender] -= amount;

        // Calculate the withdraw tax
        uint256 tax = amount * devFee / 10000;

        // Transfer the tokens to user
        stakingToken.safeTransfer(msg.sender, amount - tax);
        // Tax to treasury
        stakingToken.safeTransfer(treasury, tax);

        emit Withdrawn(msg.sender, amount);
    }

    /// @dev Gets reward tokens and withdraws user stake
    function exit() external nonReentrant {
        getReward();
        withdraw(balanceOf(msg.sender));
    }

    /// @dev Gets reward tokens from all reward pools
    function getReward() public nonReentrant {
        updateReward(msg.sender);
        uint256 arraysize = poolInfo.length;

        // loop through all the reward pools for a user
        for (uint256 i = 0; i < arraysize; i++) {
            PoolInfo storage pool = poolInfo[i];
            uint256 reward = rewardsInPool[i][msg.sender].rewards;

            if (address(pool.rewardToken) == address(0) || reward == 0) {
                continue;
            } else {
                rewardsInPool[i][msg.sender].rewards = 0;
                pool.rewardToken.safeTransfer(msg.sender, reward);
                emit RewardPaid(
                    msg.sender,
                    address(pool.rewardToken),
                    reward
                );
            }
        }
    }

    /// @dev Gets reward tokens and re-stakes rewards if rewardToken = stakingToken
    function getRewardCompound() public {
        updateReward(msg.sender);

        // loop through all the reward pools for a user
        for (uint256 i = 0; i < poolInfo.length; i++) {
            PoolInfo storage pool = poolInfo[i];
            uint256 reward = rewardsInPool[i][msg.sender].rewards;

            if (address(pool.rewardToken) == address(0) || reward == 0) {
                continue;
            } else {
                rewardsInPool[i][msg.sender].rewards = 0;

                if (address(pool.rewardToken) == address(stakingToken)) {
                    stake(reward);
                } else {
                    pool.rewardToken.safeTransfer(msg.sender, reward);
                    emit RewardPaid(
                        msg.sender,
                        address(pool.rewardToken),
                        reward
                    );
                }
            }
        }
    }

    /// @dev Returns staking balance of an account
    /// @param account The account to check
    /// @return The amount of stakingTokens staked by `account`
    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }

    /*//////////////////////////////////////////////////////////////
                            ADMIN FUNCTIONS
    //////////////////////////////////////////////////////////////*/

    /// @dev Sets up a new reward pool
    /// @param _rewardToken The address of the reward token that will be added as a reward pool
    function addRewardPool(IERC20Metadata _rewardToken) public onlyOwner {
        require(address(_rewardToken) != address(0), "Cannot add burn address");
        require(
            !addedRewardTokens[address(_rewardToken)],
            "Token already added"
        );
        // calculate info relevant for storing in the pool array
        uint256 totalPools = poolInfo.length;
        uint256 _rewardTokenID = totalPools++;

        poolInfo.push(
            PoolInfo({
                rewardToken: _rewardToken,
                rewardPoolID: _rewardTokenID,
                duration: 0,
                periodFinish: 0,
                startTime: 0,
                lastUpdateTime: 0,
                rewardRate: 0,
                rewardPerTokenStored: 0
            })
        );

        addedRewardTokens[address(_rewardToken)] = true;

        emit RewardPoolAdded(_rewardTokenID, address(_rewardToken));
    }

    /// @dev Called to change the details of a reward pool
    /// @param _pid The pool ID of the reward pool to change details
    /// @param _reward The amount of new reward tokens to be added to the pool
    /// @param _duration The duration of the pool from the current time
    function extendRewardPool(uint256 _pid, uint256 _reward, uint256 _duration) external onlyOwner {
        require(_reward > 0, "Can not add zero balance");
        require(_duration > 0, "Must define valid duration length");

        PoolInfo storage pool = poolInfo[_pid];
        uint256 timeNow = block.timestamp;
        uint256 rewardsRemaining;
        uint256 totalRewards;

        // Transfer reward token from caller to contract
        pool.rewardToken.safeTransferFrom(
            msg.sender,
            address(this),
            _reward
        );

        // Update reward per token stored value + last updated value
        updateRewardPerTokenStored(_pid);

        // Update duration of pool
        pool.duration = _duration;

        // Update reward rate
        // if pool has already finished
        if (timeNow > pool.periodFinish) {
            pool.rewardRate = _reward / _duration;
            totalRewards = _reward;
        } else {
            // if pool has not finished yet
            // Remaining time for the pool
            uint256 remainingTime = pool.periodFinish - timeNow;
            // And the rewards
            rewardsRemaining = remainingTime * pool.rewardRate;
            // Find new amount of rewards in pool
            totalRewards = rewardsRemaining + _reward;
            // Set the current rate
            pool.rewardRate = totalRewards / pool.duration;
        }

        // Set the last updated time
        pool.lastUpdateTime = timeNow;

        // Add the period to be equal to duration set
        pool.periodFinish = timeNow + pool.duration;

        emit RewardPoolExtended(
            _pid,
            address(pool.rewardToken),
            rewardsRemaining,
            _reward,
            totalRewards,
            pool.duration,
            pool.periodFinish
        );
    }

    /// @dev Called to start the emissions on a reward pool
    /// @param _pid The pool ID of the reward pool to start
    /// @param _reward The amount of reward tokens to be distributed
    /// @param _duration The duration of the reward pool in seconds
    function startRewardPool(uint256 _pid, uint256 _reward, uint256 _duration) external onlyOwner {
        require(_reward > 0, "Can not add zero balance");
        require(_duration > 0, "Must define valid duration length");

        PoolInfo storage pool = poolInfo[_pid];
        uint256 timeNow = block.timestamp;

        // Transfer reward token from caller to contract
        pool.rewardToken.safeTransferFrom(
            msg.sender,
            address(this),
            _reward
        );

        // Set reward values
        updateRewardPerTokenStored(_pid);

        // Set duration of pool
        pool.duration = _duration;

        // Set the current rate
        pool.rewardRate = _reward / pool.duration;

        // Set the last updated time
        pool.lastUpdateTime = timeNow;

        // Set the initial start time
        pool.startTime = timeNow;

        // Add the period to be equal to duration set
        pool.periodFinish = timeNow + pool.duration;
        emit RewardPoolStarted(
            _pid,
            address(pool.rewardToken),
            _reward,
            pool.duration,
            pool.periodFinish
        );
    }

    /// @dev Ejects any remaining reward tokens from the reward pool specified
    /// @param _pid The pool ID of the reward pool having reward tokens ejected
    function eject(uint256 _pid) public onlyOwner {
        PoolInfo storage pool = poolInfo[_pid];

        require(block.timestamp >= pool.periodFinish + 7 days,
            "Can only eject 7 days after pool has finished"
        );
        uint256 currBalance = pool.rewardToken.balanceOf(address(this));

        // If Staking Token = Reward Token of Pool, do not withdraw the users staked tokens
        if (address(stakingToken) == address(pool.rewardToken)) {
            currBalance = currBalance - totalSupply;
        }

        pool.rewardToken.safeTransfer(msg.sender, currBalance);
    }

    /// @dev Ejects any remaining reward tokens from all reward pools
    function ejectAll() public onlyOwner {
        // loop through all reward pools to eject all
        for (uint256 i = 0; i < poolInfo.length; i++) {
            PoolInfo storage pool = poolInfo[i];

            if (address(pool.rewardToken) == address(0)) {
                continue;
            } else {
                eject(i);
            }
        }
    }

    /// @dev Forcefully retire a pool, preventing more rewards from being distributed
    /// @param _pid The pool ID of the reward pool to be retired
    function kill(uint256 _pid) external onlyOwner {
        PoolInfo storage pool = poolInfo[_pid];

        pool.periodFinish = block.timestamp;
    }

    /// @dev Recovers tokens that are stuck on the contract
    /// @param tokenAddress The address of the stuck token
    /// @param tokenAmount The amount of tokens stuck on the contract
    function emergencyWithdraw(address tokenAddress, uint256 tokenAmount)
        external
        onlyOwner
    {
        IERC20Metadata(tokenAddress).safeTransfer(msg.sender, tokenAmount);
    }

    /// @dev Sets a new treasury address
    /// @param _treasury The new treasury address
    function setNewTreasury(address _treasury) external onlyOwner {
        treasury = _treasury;
    }
    
}