// File: YashaStaking.sol



// SPDX-License-Identifier: MIT
/// @title YashaStaking Staking Contract
/// @author MrD 

pragma solidity >=0.8.11;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

contract YashaStaking is Ownable, ReentrancyGuard {
    using SafeERC20 for IERC20;

    struct LockSetting {
        uint256 stakeMultiplier; // multiplier this setting gives to the bonus points (15 = 1.5x)
        uint256 lockDuration; // how long you need to lock for this setting in seconds
        uint256 totalLocked; // total number of tokens locked with this setting
    }

    struct UserLock {
        uint256 stakeMultiplier; // multiplier from the settings (15 = 1.5x)
        uint256 tokenAmount; // total amount they locked
        uint256 startTime; // start of the lock
        uint256 endTime; //when the lock ends
        uint256 lastHarvest; // block last harvested
    }

    struct Adjustment {
        uint256 blockNumber; // block the adjustment was made
        uint256 tokensPerBlock; // snapshot of the current token per/block
        uint256 nativePerBlock; // snapshot of the current native per/block
    }


    // aray of the different lock options
    LockSetting[] public lockSettings;

    // maping for the users locks
    // mapping(address => mapping( uint256 => UserLock)) public userLocks;
    mapping(address => UserLock[]) public userLocks;
    mapping(address => uint256) public userTotalLocks;

    // maping for the adjustments
    mapping(uint256 => Adjustment) public adjustments;
    uint256 public totalAdjustments;

    // Global active flag
    bool isActive;

    // max locks 1 account can ever have
    uint256 public constant maxLocks = 10;

    // The Tokens
    // token given as a reward
    IERC20 public rewardToken;

    // token that is staked
    IERC20 public stakeToken; 

    // distribution per block
    // amount per block for the rewardToken
    uint256 public tokensPerBlock; 

    // amount per block for ETH
    uint256 public nativePerBlock; 

    // The block number when rewards start 
    uint256 public startBlock;

    uint256 constant totalAllocPoint = 10000;

    event SetActive( bool isActive);
    event Deposit(address indexed user, uint256 indexed settingId, uint256 amount);
    event Withdraw(address indexed user, uint256 indexed settingId, uint256 amount);
    event Harvest(address indexed user, uint256 tokenAmount, uint256 ethAmount);
    event EmergencyWithdraw(address indexed user, uint256 indexed pid, uint256 amount);
    event UpdateEmissionRate(address indexed user, uint256 tokensPerBlock, uint256 nativePerBlock);
    event SetLockSettings(uint256[] locksMultiplier, uint256[] locksDuration);

    constructor(
        IERC20 _rewardToken,
        IERC20  _stakeToken,
        uint256 _tokensPerBlock,
        uint256 _nativePerBlock,
        uint256 _startBlock,
        uint256[] memory _locksMultiplier,
        uint256[] memory  _locksDuration
    ) {

        rewardToken = _rewardToken;
        stakeToken = _stakeToken;
        tokensPerBlock = _tokensPerBlock;
        nativePerBlock = _nativePerBlock;
        startBlock = _startBlock;

        _setLockSettings( _locksMultiplier , _locksDuration );
    }


    function setLockSettings(  uint256[] memory _locksMultiplier ,uint256[] memory  _locksDuration ) public onlyOwner {
        _setLockSettings( _locksMultiplier , _locksDuration );
    }

    function _setLockSettings( uint256[] memory _locksMultiplier ,uint256[] memory  _locksDuration ) private {
        delete lockSettings;
        for (uint256 i = 0; i < _locksMultiplier.length; ++i) {
            lockSettings.push(LockSetting({
                lockDuration : _locksDuration[i],
                stakeMultiplier : _locksMultiplier[i],
                totalLocked: 0
            }));
        }
        emit SetLockSettings(_locksMultiplier,_locksDuration);
    }

    /* @dev Return reward multiplier over the given _from to _to block */
    function _getMultiplier(uint256 _from, uint256 _to) private pure returns (uint256) {
        return _to - _from;
    }

    function _calc(uint256 _var, uint256 _mul, uint256 _div) private pure returns (uint256) {
        return (_var * _mul)/_div;
    }
    
    /* @dev View function to see pending rewards on frontend.*/
    function pendingRewards(uint256 _lockId, address _user)  external view returns (uint256,uint256) {
        return _pendingRewards(_lockId, _user);
    }

    /* @dev calc the pending rewards */
    function _pendingRewards(uint256 _lockId, address _user) internal view returns (uint256,uint256) {
        UserLock storage userLock = userLocks[_user][_lockId];

        uint256 stakedSupply = stakeToken.balanceOf(address(this));
        uint256 lastHarvest = userLock.lastHarvest;

        // if there are no adjustments or we have recently harvested, only get the current amount
        if(totalAdjustments == 0 || adjustments[totalAdjustments-1].blockNumber < lastHarvest) {
            return _calcRewardPeriod(userLock.tokenAmount, tokensPerBlock, nativePerBlock, userLock.stakeMultiplier, lastHarvest, stakedSupply, block.number);
        } else {

            // otherwise we break apart the rewards per adjustment block
            uint256 tokenAmount;
            uint256 nativeAmount;

            // get the current values first
            ( tokenAmount,  nativeAmount ) = _calcRewardPeriod(userLock.tokenAmount, tokensPerBlock, nativePerBlock, userLock.stakeMultiplier, adjustments[totalAdjustments-1].blockNumber, stakedSupply, block.number);

            for(uint256 i=totalAdjustments-1; i >= 0; --i){
                uint256 _tokenAmount;
                uint256 _nativeAmount;
                if(i == 0 || lastHarvest > adjustments[i-1].blockNumber){
                    (_tokenAmount, _nativeAmount ) = _calcRewardPeriod(userLock.tokenAmount, adjustments[i].tokensPerBlock, adjustments[i].nativePerBlock, userLock.stakeMultiplier, lastHarvest, stakedSupply, adjustments[i].blockNumber);
                    tokenAmount = tokenAmount + _tokenAmount;
                    nativeAmount = nativeAmount + _nativeAmount;
                    break;
                }

                ( _tokenAmount,  _nativeAmount ) = _calcRewardPeriod(userLock.tokenAmount, adjustments[i].tokensPerBlock, adjustments[i].nativePerBlock, userLock.stakeMultiplier, adjustments[i-1].blockNumber, stakedSupply, adjustments[i].blockNumber);
                tokenAmount = tokenAmount + _tokenAmount;
                nativeAmount = nativeAmount + _nativeAmount;

            }

            return (tokenAmount, nativeAmount);
        }
        
    }

    function _calcRewardPeriod(uint256 _tokenAmount, uint256 _tokensPerBlock, uint256 _nativePerBlock, uint256 _stakeMultiplier, uint256 _lastHarvest, uint256 _stakedSupply, uint256 _endBlock) private pure returns (uint256,uint256){


        uint256 tokenReward = _calc(_getMultiplier(_lastHarvest, _endBlock),_tokensPerBlock, totalAllocPoint); 
        uint256 nativeReward = _calc(_getMultiplier(_lastHarvest, _endBlock),_nativePerBlock, totalAllocPoint);
        
        uint256 _accTokensPerShare = _calc(tokenReward,1e12, _stakedSupply); 
        uint256 _accNativePerShare = _calc(nativeReward,1e12, _stakedSupply);

        uint256 _tokenMultiplier = _calc(_tokenAmount,_stakeMultiplier, totalAllocPoint)/10;

        return (
            _calc(_tokenMultiplier,_accTokensPerShare, 1e12),
            _calc(_tokenMultiplier,_accNativePerShare, 1e12)       
        );
    }   

    function harvest(uint256 _lockId) public nonReentrant {
        return _harvest(_lockId, msg.sender);

    }   

    function _harvest(uint256 _lockId, address _user) private {
       // UserLock storage userLock = userLocks[_user][_lockId];

        (uint256 pendingTokens, uint256 pendingNative) = _pendingRewards(_lockId, _user);

        if(pendingTokens > 0){
            safeTokenTransfer(_user, pendingTokens);
        }

        if(pendingNative > 0){
            (bool sent,) = address(_user).call{value: (pendingNative)}("");
            require(sent,"native harvest failed");
        }
        userLocks[_user][_lockId].lastHarvest = block.number;

        emit Harvest(_user, pendingTokens, pendingNative);

    }

    /* @dev deposit tokens into the pool */
    function deposit(uint256 _settingId, uint256 _amount) public nonReentrant {
        require(isActive,'Not active');
        require(userTotalLocks[msg.sender] < maxLocks, 'Max locks');
        require(_amount > 0 && stakeToken.balanceOf(address(msg.sender)) >= _amount, "Not enough tokens");

        LockSetting storage lockSetting = lockSettings[_settingId];

        stakeToken.safeTransferFrom(address(msg.sender), address(this), _amount);
        
        userLocks[msg.sender].push(UserLock({
            stakeMultiplier: lockSetting.stakeMultiplier,
            tokenAmount: _amount,
            startTime: block.timestamp,
            endTime: block.timestamp + lockSetting.lockDuration,
            lastHarvest:block.number
        }));

         userTotalLocks[msg.sender] = userLocks[msg.sender].length;
         
         lockSetting.totalLocked = lockSetting.totalLocked + _amount;
        emit Deposit(msg.sender, _settingId, _amount);
    }

    /* @dev withdraw unlocked tokens from the pool */
    function withdraw(uint256 _lockId) public nonReentrant {
        require(isActive,'Not active');

        UserLock storage userLock = userLocks[msg.sender][_lockId];

        require(userLock.tokenAmount > 0, "Nothing Staked");
        require(block.timestamp >= userLock.endTime, "Tokens Locked");

        (uint256 pendingToken, uint256 pendingNative) = _pendingRewards(_lockId, msg.sender);
        
        if (pendingToken > 0 || pendingNative > 0) {
            _harvest(_lockId,msg.sender);
        }

        
        // transfer to user 
        stakeToken.safeTransfer(address(msg.sender), userLock.tokenAmount);

        // keep things clean
        userLocks[msg.sender][_lockId] = userLocks[msg.sender][userLocks[msg.sender].length - 1];
        userLocks[msg.sender].pop();
        userTotalLocks[msg.sender] = userLocks[msg.sender].length;
        
        emit Withdraw(msg.sender, _lockId, userLock.tokenAmount);
    }

    function totalUserWeight(address _user) public view returns(uint256) {
        uint256 totalValue;
        
        for(uint256 i=0; i < userTotalLocks[_user]; ++i){
            totalValue = totalValue + ((userLocks[_user][i].tokenAmount * userLocks[_user][i].stakeMultiplier)/10);
        }

        return totalValue;
    }

    function totalUserStake(address _user) public view returns(uint256) {
        uint256 totalValue;
        
        for(uint256 i=0; i < userTotalLocks[_user]; ++i){
            totalValue = totalValue + userLocks[_user][i].tokenAmount;
        }

        return totalValue;
    }

    /* @dev Safe token transfer function, just in case if rounding error causes pool to not have enough tokens */
    function safeTokenTransfer(address _to, uint256 _amount) internal {
        uint256 bal = rewardToken.balanceOf(address(this));
        bool transferSuccess = false;
        if (_amount > bal) {
            transferSuccess = rewardToken.transfer(_to, bal);
        } else {
            transferSuccess = rewardToken.transfer(_to, _amount);
        }
        require(transferSuccess, "safeTokenTransfer: transfer failed");
    }

    function setActive(bool _isActive) public onlyOwner {
        isActive = _isActive;
        emit SetActive(_isActive);
    }

    function updateRewardTokenContract(IERC20 _rewardToken) public onlyOwner {
        rewardToken = _rewardToken;
    }

    function updateStakeTokenContract(IERC20 _stakeToken) public onlyOwner {
        stakeToken = _stakeToken;
    }

    function updateEmissionRate(uint256 _tokensPerBlock, uint256 _nativePerBlock) public onlyOwner {
        adjustments[totalAdjustments] = Adjustment({
            blockNumber: block.number,
            tokensPerBlock: _tokensPerBlock,
            nativePerBlock: _nativePerBlock
        });

        totalAdjustments = totalAdjustments + 1;
        emit UpdateEmissionRate(msg.sender, _tokensPerBlock, _nativePerBlock);
    }

    // pull all the tokens out of the contract, needed for migrations/emergencies 
    function withdrawToken() public onlyOwner {
        safeTokenTransfer(address(owner()), rewardToken.balanceOf(address(this)));
    }

    // pull all the bnb out of the contract, needed for migrations/emergencies 
    function withdrawETH() public onlyOwner {
         (bool sent,) =address(owner()).call{value: (address(this).balance)}("");
        require(sent,"withdraw failed");
    }


    receive() external payable {}
}
// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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 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 `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, 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 `from` to `to` 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 from,
        address to,
        uint256 amount
    ) external returns (bool);
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../extensions/draft-IERC20Permit.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));
        }
    }

    function safePermit(
        IERC20Permit token,
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        uint256 nonceBefore = token.nonces(owner);
        token.permit(owner, spender, value, deadline, v, r, s);
        uint256 nonceAfter = token.nonces(owner);
        require(nonceAfter == nonceBefore + 1, "SafeERC20: permit did not succeed");
    }

    /**
     * @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/security/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (security/ReentrancyGuard.sol)

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 making 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;
    }
}

// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @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() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        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 {
        _transferOwnership(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");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @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 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
                /// @solidity memory-safe-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin/contracts/token/ERC20/extensions/draft-IERC20Permit.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/draft-IERC20Permit.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
 * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
 *
 * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
 * presenting a message signed by the account. By not relying on {IERC20-approve}, the token holder account doesn't
 * need to send a transaction, and thus is not required to hold Ether at all.
 */
interface IERC20Permit {
    /**
     * @dev Sets `value` as the allowance of `spender` over ``owner``'s tokens,
     * given ``owner``'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);

    /**
     * @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
     */
    // solhint-disable-next-line func-name-mixedcase
    function DOMAIN_SEPARATOR() external view returns (bytes32);
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

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;
    }
}