// File: /contracts/cvxFxsStaking.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.8.10;

import "./interfaces/MathUtil.sol";
import "./interfaces/IBooster.sol";
import "./interfaces/IVoterProxy.sol";
import "./interfaces/IFxsDepositor.sol";
import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
import '@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol';
import '@openzeppelin/contracts/token/ERC20/ERC20.sol';
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";


contract cvxFxsStaking is ERC20, ReentrancyGuard{
    using SafeERC20 for IERC20;


    /* ========== STATE VARIABLES ========== */

    struct Reward {
        uint256 periodFinish;
        uint256 rewardRate;
        uint256 lastUpdateTime;
        uint256 rewardPerTokenStored;
    }

    struct EarnedData {
        address token;
        uint256 amount;
    }

    address public constant vefxsProxy = address(0x59CFCD384746ec3035299D90782Be065e466800B);
    address public constant cvxfxs = address(0xFEEf77d3f69374f66429C91d732A244f074bdf74);
    address public constant fxs = address(0x3432B6A60D23Ca0dFCa7761B7ab56459D9C964D0);
    address public constant fxsDepositor = address(0x8f55d7c21bDFf1A51AFAa60f3De7590222A3181e);

    //rewards
    address[] public rewardTokens;
    mapping(address => Reward) public rewardData;
    mapping(address => address) public rewardRedirect;

    // Duration that rewards are streamed over
    uint256 public constant rewardsDuration = 86400 * 7;

    // reward token -> distributor -> is approved to add rewards
    mapping(address => mapping(address => bool)) public rewardDistributors;

    // user -> reward token -> amount
    mapping(address => mapping(address => uint256)) public userRewardPerTokenPaid;
    mapping(address => mapping(address => uint256)) public rewards;

    /* ========== CONSTRUCTOR ========== */

    constructor() ERC20(
            "Staked CvxFxs",
            "stkCvxFxs"
        ){
        IERC20(fxs).approve(fxsDepositor,type(uint256).max);
    }

    /* ========== ADMIN CONFIGURATION ========== */

    // Add a new reward token to be distributed to stakers
    function addReward(
        address _rewardsToken,
        address _distributor
    ) public onlyOwner {
        require(rewardData[_rewardsToken].lastUpdateTime == 0);
        require(_rewardsToken != cvxfxs && _rewardsToken != address(this), "invalid token");

        rewardTokens.push(_rewardsToken);
        rewardData[_rewardsToken].lastUpdateTime = block.timestamp;
        rewardData[_rewardsToken].periodFinish = block.timestamp;
        rewardDistributors[_rewardsToken][_distributor] = true;
        emit RewardAdded(_rewardsToken, _distributor);
    }

    // Modify approval for an address to call notifyRewardAmount
    function approveRewardDistributor(
        address _rewardsToken,
        address _distributor,
        bool _approved
    ) external onlyOwner {
        require(rewardData[_rewardsToken].lastUpdateTime > 0);
        rewardDistributors[_rewardsToken][_distributor] = _approved;
        emit RewardDistributorApproved(_rewardsToken, _distributor);
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    //deposit fxs for cvxfxs and stake
    function deposit(uint256 _amount, bool _lock) public nonReentrant{
        require(_amount > 0, 'RewardPool : Cannot deposit 0');

        //mint will call _updateReward
        _mint(msg.sender, _amount);

        //transfer fxs
        IERC20(fxs).safeTransferFrom(msg.sender, address(this), _amount);
        //deposit, cvxfxs will be returned here
        IFxsDepositor(fxsDepositor).deposit(_amount,_lock);
        
        emit Staked(msg.sender, _amount);
    }

    //deposit fxs for cvxfxs and stake
    function deposit(uint256 _amount) external{
        deposit(_amount, false);
    }

    //deposit cvxfxs
    function stake(uint256 _amount) public nonReentrant{
        require(_amount > 0, 'RewardPool : Cannot stake 0');

        //mint will call _updateReward
        _mint(msg.sender, _amount);

        //pull cvxfxs
        IERC20(cvxfxs).safeTransferFrom(msg.sender, address(this), _amount);
        
        emit Staked(msg.sender, _amount);
    }

    //deposit all cvxfxs
    function stakeAll() external{
        uint256 balance = IERC20(cvxfxs).balanceOf(msg.sender);
        stake(balance);
    }

    //deposit cvxfxs and accredit a different address
    function stakeFor(address _for, uint256 _amount) external nonReentrant{
        require(_amount > 0, 'RewardPool : Cannot stake 0');
        
        //give to _for
        //mint will call _updateReward
        _mint(_for, _amount);

        //pull from sender
        IERC20(cvxfxs).safeTransferFrom(msg.sender, address(this), _amount);
        emit Staked(_for, _amount);
    }

    //withdraw cvxfxs
    function withdraw(uint256 _amount) external nonReentrant{
        require(_amount > 0, 'RewardPool : Cannot withdraw 0');

        //burn will call _updateReward
        _burn(msg.sender, _amount);

        //send cvxfxs
        IERC20(cvxfxs).safeTransfer(msg.sender, _amount);

        emit Withdrawn(msg.sender, _amount);
    }


    /* ========== VIEWS ========== */

    function _rewardPerToken(address _rewardsToken) internal view returns(uint256) {
        if (totalSupply() == 0) {
            return rewardData[_rewardsToken].rewardPerTokenStored;
        }
        return
        rewardData[_rewardsToken].rewardPerTokenStored 
        + (
            (_lastTimeRewardApplicable(rewardData[_rewardsToken].periodFinish) - rewardData[_rewardsToken].lastUpdateTime)     
            * rewardData[_rewardsToken].rewardRate
            * 1e18
            / totalSupply()
        );
    }

    function _earned(
        address _user,
        address _rewardsToken,
        uint256 _balance
    ) internal view returns(uint256) {
        return (_balance * (_rewardPerToken(_rewardsToken) - userRewardPerTokenPaid[_user][_rewardsToken] ) / 1e18) + rewards[_user][_rewardsToken];
    }

    function _lastTimeRewardApplicable(uint256 _finishTime) internal view returns(uint256){
        return MathUtil.min(block.timestamp, _finishTime);
    }

    function lastTimeRewardApplicable(address _rewardsToken) public view returns(uint256) {
        return _lastTimeRewardApplicable(rewardData[_rewardsToken].periodFinish);
    }

    function rewardPerToken(address _rewardsToken) external view returns(uint256) {
        return _rewardPerToken(_rewardsToken);
    }

    function getRewardForDuration(address _rewardsToken) external view returns(uint256) {
        return rewardData[_rewardsToken].rewardRate * rewardsDuration;
    }

    // Address and claimable amount of all reward tokens for the given account
    function claimableRewards(address _account) external view returns(EarnedData[] memory userRewards) {
        userRewards = new EarnedData[](rewardTokens.length);
        for (uint256 i = 0; i < userRewards.length; i++) {
            address token = rewardTokens[i];
            userRewards[i].token = token;
            userRewards[i].amount = _earned(_account, token,  balanceOf(_account));
        }
        return userRewards;
    }

    //set any claimed rewards to automatically go to a different address
    //set address to zero to disable
    function setRewardRedirect(address _to) external nonReentrant{
        rewardRedirect[msg.sender] = _to;
        emit RewardRedirected(msg.sender, _to);
    }

    // Claim all pending rewards
    function getReward(address _address) public nonReentrant updateReward(_address) {
        for (uint i; i < rewardTokens.length; i++) {
            address _rewardsToken = rewardTokens[i];
            uint256 reward = rewards[_address][_rewardsToken];
            if (reward > 0) {
                rewards[_address][_rewardsToken] = 0;
                if(rewardRedirect[_address] != address(0)){
                    IERC20(_rewardsToken).safeTransfer(rewardRedirect[_address], reward);
                }else{
                    IERC20(_rewardsToken).safeTransfer(_address, reward);
                }
                emit RewardPaid(_address, _rewardsToken, reward);
            }
        }
    }

    // Claim all pending rewards and forward
    function getReward(address _address, address _forwardTo) public nonReentrant updateReward(_address) {
        //if forwarding, require caller is self
        require(msg.sender == _address, "!self");

        for (uint i; i < rewardTokens.length; i++) {
            address _rewardsToken = rewardTokens[i];
            uint256 reward = rewards[_address][_rewardsToken];
            if (reward > 0) {
                rewards[_address][_rewardsToken] = 0;
                IERC20(_rewardsToken).safeTransfer(_forwardTo, reward);
                emit RewardPaid(_address, _rewardsToken, reward);
            }
        }
    }


    /* ========== RESTRICTED FUNCTIONS ========== */

    function rewardTokenLength() external view returns(uint256){
        return rewardTokens.length;
    }

    function _notifyReward(address _rewardsToken, uint256 _reward) internal {
        Reward storage rdata = rewardData[_rewardsToken];

        if (block.timestamp >= rdata.periodFinish) {
            rdata.rewardRate = _reward / rewardsDuration;
        } else {
            uint256 remaining = rdata.periodFinish - block.timestamp;
            uint256 leftover = remaining * rdata.rewardRate;
            rdata.rewardRate = (_reward + leftover) / rewardsDuration;
        }

        rdata.lastUpdateTime = block.timestamp;
        rdata.periodFinish = block.timestamp + rewardsDuration;
    }

    function notifyRewardAmount(address _rewardsToken, uint256 _reward) external nonReentrant updateReward(address(0)) {
        require(rewardDistributors[_rewardsToken][msg.sender]);
        require(_reward > 0 && _reward < 1e30, "bad reward value");

        _notifyReward(_rewardsToken, _reward);

        // handle the transfer of reward tokens via `transferFrom` to reduce the number
        // of transactions required and ensure correctness of the _reward amount
        IERC20(_rewardsToken).safeTransferFrom(msg.sender, address(this), _reward);
        
        emit RewardAdded(_rewardsToken, _reward);
    }

    // Added to support recovering LP Rewards from other systems such as BAL to be distributed to holders
    function recoverERC20(address _tokenAddress, uint256 _tokenAmount) external nonReentrant onlyOwner {
        require(rewardData[_tokenAddress].lastUpdateTime == 0, "Cannot withdraw reward token");
        require(_tokenAddress != cvxfxs, "Cannot withdraw staking token");
        IERC20(_tokenAddress).safeTransfer(IBooster(IVoterProxy(vefxsProxy).operator()).rewardManager(), _tokenAmount);
        emit Recovered(_tokenAddress, _tokenAmount);
    }

    function _updateReward(address _account) internal{
        uint256 userBal = balanceOf(_account);
        for (uint i = 0; i < rewardTokens.length; i++) {
            address token = rewardTokens[i];
            rewardData[token].rewardPerTokenStored = _rewardPerToken(token);
            rewardData[token].lastUpdateTime = _lastTimeRewardApplicable(rewardData[token].periodFinish);
            if (_account != address(0)) {
                rewards[_account][token] = _earned(_account, token, userBal );
                userRewardPerTokenPaid[_account][token] = rewardData[token].rewardPerTokenStored;
            }
        }
    }

    function _beforeTokenTransfer(address _from, address _to, uint256 ) internal override {
        //checkpoint from and to, can skip if address 0 so no extra gas
        //is used when minting burning
        if(_from != address(0)){
            _updateReward(_from);
        }
        if(_to != address(0)){
            _updateReward(_to);
        }
    }

    /* ========== MODIFIERS ========== */

    modifier onlyOwner() {
        require(IBooster(IVoterProxy(vefxsProxy).operator()).rewardManager() == msg.sender, "!owner");
        _;
    }

    modifier updateReward(address _account) {
        _updateReward(_account);
        _;
    }

    /* ========== EVENTS ========== */
    event RewardAdded(address indexed _token, uint256 _reward);
    event Staked(address indexed _user, uint256 _amount);
    event Withdrawn(address indexed _user, uint256 _amount);
    event RewardPaid(address indexed _user, address indexed _rewardsToken, uint256 _reward);
    event Recovered(address _token, uint256 _amount);
    event RewardAdded(address indexed _reward, address indexed _distributor);
    event RewardDistributorApproved(address indexed _reward, address indexed _distributor);
    event RewardRedirected(address indexed _account, address _forward);
}
// File: /contracts/interfaces/MathUtil.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.8.10;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library MathUtil {
    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }
}
// File: /contracts/interfaces/IVoterProxy.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.8.10;

interface IVoterProxy{
    function operator() external view returns(address);
}
// File: /contracts/interfaces/IFxsDepositor.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.8.10;

interface IFxsDepositor {
   function deposit(uint256 _amount, bool _lock) external;
}
// File: /contracts/interfaces/IBooster.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.8.10;

interface IBooster {
   function addPool(address _implementation, address _stakingAddress, address _stakingToken) external;
   function deactivatePool(uint256 _pid) external;
   function voteGaugeWeight(address _controller, address _gauge, uint256 _weight) external;
   function setDelegate(address _delegateContract, address _delegate, bytes32 _space) external;
   function owner() external returns(address);
   function rewardManager() external returns(address);
   function isShutdown() external returns(bool);
}
// File: @openzeppelin/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @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;
    }
}

// File: @openzeppelin/contracts/utils/Address.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @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
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        assembly {
            size := extcodesize(account)
        }
        return size > 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 functionCall(target, data, "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");
        require(isContract(target), "Address: call to non-contract");

        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResult(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) {
        require(isContract(target), "Address: static call to non-contract");

        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResult(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) {
        require(isContract(target), "Address: delegate call to non-contract");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // 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

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../../../utils/Address.sol";

/**
 * @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'
        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 {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            uint256 newAllowance = oldAllowance - 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
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: @openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @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);
}

// File: @openzeppelin/contracts/token/ERC20/ERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./IERC20.sol";
import "./extensions/IERC20Metadata.sol";
import "../../utils/Context.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead returning `false` on failure. This behavior is nonetheless
 * conventional and does not conflict with the expectations of ERC20
 * applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
     * overridden;
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);

        uint256 currentAllowance = _allowances[sender][_msgSender()];
        require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
        unchecked {
            _approve(sender, _msgSender(), currentAllowance - amount);
        }

        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender] + addedValue);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        uint256 currentAllowance = _allowances[_msgSender()][spender];
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(_msgSender(), spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `sender` to `recipient`.
     *
     * This internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(sender, recipient, amount);

        uint256 senderBalance = _balances[sender];
        require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[sender] = senderBalance - amount;
        }
        _balances[recipient] += amount;

        emit Transfer(sender, recipient, amount);

        _afterTokenTransfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);

        _afterTokenTransfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
        }
        _totalSupply -= amount;

        emit Transfer(account, address(0), amount);

        _afterTokenTransfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

// File: @openzeppelin/contracts/security/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @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;
    }
}