// File: contracts/PublicRound.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.15;


/**
 * @dev Modifier 'onlyOwner' becomes available, where owner is the contract deployer
 */ 
import "@openzeppelin/contracts/access/Ownable.sol";

/**
 * @dev ERC20 token interface
 */
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

/**
 * @dev Allows use of SafeERC20 transfer functions
 */
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

/**
 * @dev Chainlink price oracle interface
 */
import "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";

/**
 * @dev Makes mofifier nonReentrant available for use
 */
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";

/**
 * @dev SBT interface
 */
import "./Interfaces/ISBT.sol";



contract PublicRound is Ownable, ReentrancyGuard {

    
    using SafeERC20 for IERC20;


    // --- VARIABLES -- //

    ISBT sbt;
    AggregatorV3Interface internal priceFeed;

    address[] stables;

    uint public roundStartTime;
    uint public roundEndTime;

    uint public tokenPrice = 0.369*10**6; // $0.369 (6 decimal)
    uint public walletTokenLimit = 56910569105691056910569; // $21,000 worth of XCAL @ $0.369 per token
    uint public totalTokenLimit; // 18 decimal

    uint public totalTokens; // 18 decimal

    bool public withdrawalsEnabled;



    // --- CONSTRUCTOR -- //

    constructor(
        uint _totalTokenLimit, // XCAL (18 token decimal)
        address _dai,   // Eth main net: 0x6B175474E89094C44Da98b954EedeAC495271d0F  --- Arb: 0xDA10009cBd5D07dd0CeCc66161FC93D7c9000da1
        address _frax,  // Eth main net: 0x853d955aCEf822Db058eb8505911ED77F175b99e  --- Arb: 0x17FC002b466eEc40DaE837Fc4bE5c67993ddBd6F
        address _usdc,  // Eth main net: 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48  --- Arb: 0xFF970A61A04b1cA14834A43f5dE4533eBDDB5CC8
        address _usdt,  // Eth main net: 0xdAC17F958D2ee523a2206206994597C13D831ec7  --- Arb: 0xFd086bC7CD5C481DCC9C85ebE478A1C0b69FCbb9
        address _sbtAddress,
        address _aggregatorContract // Eth main net: 0x5f4eC3Df9cbd43714FE2740f5E3616155c5b8419  --- Arb: 0x639Fe6ab55C921f74e7fac1ee960C0B6293ba612
        ) {
        
        totalTokenLimit = _totalTokenLimit;

        stables = [_dai, _frax, _usdc, _usdt];

        for (uint i=1; i<=stables.length; i++) {
            acceptedStables[stables[i-1]] = i;
        }

        sbt = ISBT(_sbtAddress);
        priceFeed = AggregatorV3Interface(_aggregatorContract);
    }


    // --- MAPPINGS -- //

    /* user -> (
        ETH: 0, 
        DAI: 1, 
        FRAX: 2,
        USDC: 3
        USDT: 4
        ) -> balance
    */
    mapping(address => mapping(uint => uint)) userDeposits;
    mapping(address => uint) acceptedStables;
    mapping(address => uint) prXCAL;
    mapping(address => uint) dcrXCAL;


    // --- EVENTS --- //

    event TokensPurchased(address indexed benificiary, uint amount);
    event EtherWithdrawal(uint amount, address indexed recipient);
    event StableWithdrawal(address indexed stable, uint amount, address indexed recipient);

    

    // --- USER FUNCTIONS -- //

    /// @dev Accepts direct ETH deposits. Functions the same as buyWithEth.
    receive() external payable {
        buyWithEth();
    }

    
    /**
     * @dev Exchange Ether for SBT representing ownership of XCAL tokens claimable upon XCAL token launch
     */
    function buyWithEth() public payable nonReentrant {

        require(
            msg.value > 0,
            "invalid amount"
        );

        require(
            block.timestamp >= roundStartTime && block.timestamp < roundEndTime,
            "Round not live"
        );

        uint numberOfTokens = (msg.value * uint(getLatestPrice())) / (tokenPrice * 10**2); 
        
        tokenPurchase(msg.sender, numberOfTokens);
        userDeposits[msg.sender][0] += msg.value;
    }


    /**
     * @dev Exchange DAI, FRAX, USDC or USDT for a SBT representing ownership of XCAL tokens claimable upon XCAL token launch
     * @param _amount - amount of stable coin to exchange
     * Note: Stable coin must already have been approved for spend
     */
    function buyWithStable(uint _amount, address _stable) public nonReentrant {

        require(
            acceptedStables[_stable] != 0,
            "Stable coin not accepted"
        );

        require(
            block.timestamp >= roundStartTime && block.timestamp < roundEndTime,
            "Round not live"
        );

        IERC20(_stable).safeTransferFrom(msg.sender, address(this), _amount);

        uint numberOfTokens;

        // if DAI or FRAX
        if (_stable == stables[0] || _stable == stables[1]) {
            numberOfTokens = (_amount*10**6) / tokenPrice; // accounting for DAI & FRAX 18 token decimals
        } else {
            numberOfTokens = (_amount*10**18) / tokenPrice;
        }

        tokenPurchase(msg.sender, numberOfTokens);
        userDeposits[msg.sender][acceptedStables[_stable]] += _amount;
    }


    function depositorEtherWithdrawal(address payable _recipient) public nonReentrant {

        require(
            withdrawalsEnabled,
            "Still within product launch window"
        );

        require(
            userDeposits[msg.sender][0] > 0,
            "No Ether to withdraw"
        );

        uint amount = userDeposits[msg.sender][0];
        userDeposits[msg.sender][0] = 0;

        _recipient.transfer(amount);

        emit EtherWithdrawal(amount, _recipient);
    }


    function depositorStableWithdrawal(address _stable, address _recipient) public nonReentrant {

        require(
            withdrawalsEnabled,
            "Still within product launch window"
        );

        require(
            userDeposits[msg.sender][acceptedStables[_stable]] > 0,
            "No tokens to withdraw"
        );

        uint amount = userDeposits[msg.sender][acceptedStables[_stable]];
        userDeposits[msg.sender][acceptedStables[_stable]] = 0;

        IERC20(_stable).safeTransfer(_recipient, amount);

        emit StableWithdrawal(_stable, amount, _recipient);
    }


    // --- INTERNAL FUNCTIONS --- //

    /**
     * @dev Mints SBT if not already in possesion of one
     * @param _user - user address to mint SBT to and attribute owed XCAL to
     * @param _numberOfTokens - amount of XCAL owed to _user upon XCAL token launch
     */
    function tokenPurchase(address _user, uint _numberOfTokens) internal {

        require(
            viewUserXCAL(_user) + _numberOfTokens <= walletTokenLimit,
            "Exceeds wallet token limit"
        );

        require(
            totalTokens + _numberOfTokens <= totalTokenLimit,
            "Exceeds total token limit"
        );

        prXCAL[_user] += _numberOfTokens;
        totalTokens += _numberOfTokens;

        // no need to mint new SBT if _user already owns one
        if ((sbt.balanceOf(_user)) < 1) {
            sbt.mint(_user);
        }

        emit TokensPurchased(_user, _numberOfTokens);
    }


    // --- VIEW FUNCTIONS -- //

    /**
     * @dev Returns the amount of ETH still possible to deposit for a given address
     */
    function remainingEthDeposit(address _depositer) public view returns(uint) {

        uint remainingUsdValue = ((walletTokenLimit - viewUserXCAL(_depositer)) * tokenPrice) / (10**6); // 18 decimal

        return (remainingUsdValue *10**8) / uint(getLatestPrice()); // 18 decimal
    }
   
    /**
     * @dev Returns the latest price of ETH/USD as proposed by Chainlink's price oracle
     */
    function getLatestPrice() public view returns (int) {
        (
            /*uint80 roundID*/,
            int price,
            /*uint startedAt*/,
            /*uint timeStamp*/,
            /*uint80 answeredInRound*/
        ) = priceFeed.latestRoundData();

        return price;
    }

    /**
     * @dev View number of XCAL tokens owed to _user (18 token decimal) including XCAL from DCR
     * @param _user - address of user XCAL balance to view
     * Note: only callable by contract owner OR if msg.sender == _user
     */
    function viewUserXCAL(address _user) public view returns(uint) {

        return prXCAL[_user] + dcrXCAL[_user];
    }

    /**
     * @dev View user deposits for Public Round (does not include DCR deposits)
     * @param _user - address of depositor
     * @param _tokenId - 0: ETH, 1: DAI, 2: FRAX, 3: USDC, 4: USDT
     */
    function viewUserDeposits(address _user, uint _tokenId) public view returns(uint) {
        return userDeposits[_user][_tokenId];
    }    


    // --- ONLY OWNER --- //

    /**
     * @dev Set the start and end timestamps of the round
     * @param _startTimestamp - unix timestamp of round start
     * @param _endTimestamp - unix timestamp of round end
     * Note: only callable by contract owner
     */
    function setRoundTimestamps(uint _startTimestamp, uint _endTimestamp) public onlyOwner {
        
        require(
            _endTimestamp > _startTimestamp,
            "round cannot end before it starts"
        );

        roundStartTime = _startTimestamp;
        roundEndTime = _endTimestamp;
    }

    /**
     * @dev Set the dcrXCAL mapping
     * @param _addresses - array of DCR participant addresses
     * @param _amounts - array of owed XCAL, corresponding with the addresses in '_addresses' (18 token decimals)
     * Note: only callable by contract owner
     */
    function setDcrXCAL(address[] memory _addresses, uint[] memory _amounts) public onlyOwner {
        
        require(
            _addresses.length == _amounts.length,
            "Array sizes differ"
        );

        for (uint i=0; i<_addresses.length; i++) {
            dcrXCAL[_addresses[i]] = _amounts[i];
        }
    }

    /**
     * @dev Set the address of the SBT contract
     * @param _sbtAddress - address of SBT contract
     * Note: only callable by contract owner
     */
    function setSBT(address _sbtAddress) public onlyOwner {
        sbt = ISBT(_sbtAddress);
    }

    /**
     * @dev Set the maximum number of tokens availbale for purcahse by any one wallet (18 token decimal)
     * @param _walletTokenLimit - number of tokens availbale for purcahse by any one wallet
     * Note: only callable by contract owner
     */
    function setWalletTokenLimit(uint _walletTokenLimit) public onlyOwner {
        walletTokenLimit = _walletTokenLimit;
    }

    /**
     * @dev Set the maximum number of tokens availbale for purcahse via this contract (18 token decimal)
     * @param _totalTokenLimit - number of tokens availbale for purcahse through this contract
     * Note: only callable by contract owner
     */
    function setTotalTokenLimit(uint _totalTokenLimit) public onlyOwner {
        totalTokenLimit = _totalTokenLimit;
    }

    /**
     * @dev Set the status of withdrawalsEnabled. To be used in the event 3six9 does not launch in agreed window.
     * @param _status - bool of whether deposited funds are available for withdrawal
     * Note: only callable by contract owner
     */
    function setWithdrawalStatus(bool _status) public onlyOwner {
        withdrawalsEnabled = _status;
    }

    /**
     * @dev Withdraw ERC20 tokens from contract
     * @param _token - address of token to withdraw
     * @param _to - recipient of token transfer
     * @param _amount - amount of tokens to trasnfer
     */
    function withdrawERC20(
        address _token,
        address _to,
        uint _amount
        ) external onlyOwner {

        require(
            _amount <= IERC20(_token).balanceOf(address(this)),
            "Withdrawal amount greater than contract balance"
        );

        IERC20(_token).safeTransfer(_to, _amount);
    }

    /**
     * @dev Withdraw Ether from contract
     * @param _to - recipient of transfer
     * @param _amount - amount of Ether to trasnfer (18 token decimals)
     */
    function withdrawEther(
        address payable _to,
        uint _amount
        ) external onlyOwner {

        require(
            _amount <= address(this).balance,
            "Withdrawal amount greater than contract balance"
        );

        _to.transfer(_amount);
    }

}

// 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/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: @chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

interface AggregatorV3Interface {
  function decimals() external view returns (uint8);

  function description() external view returns (string memory);

  function version() external view returns (uint256);

  function getRoundData(uint80 _roundId)
    external
    view
    returns (
      uint80 roundId,
      int256 answer,
      uint256 startedAt,
      uint256 updatedAt,
      uint80 answeredInRound
    );

  function latestRoundData()
    external
    view
    returns (
      uint80 roundId,
      int256 answer,
      uint256 startedAt,
      uint256 updatedAt,
      uint80 answeredInRound
    );
}

// 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: contracts/Interfaces/ISBT.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.15;

interface ISBT {

    function mint(address _user) external;

    function balanceOf(address _user) external returns(uint);

    function totalSupply() external returns(uint);

}
// 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;
    }
}

// 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/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);
            }
        }
    }
}