// File: presale_contract.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.8.19;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/security/Pausable.sol";
import "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";

interface Aggregator {
    function latestRoundData() external view returns (
        uint80 roundId,
        int256 answer,
        uint256 startedAt,
        uint256 updatedAt,
        uint80 answeredInRound
    );
}

interface StakingManager {
    function depositByPresale(address _user, uint256 _amount) external;
}

contract Presale_EthereumETFToken is Ownable(msg.sender), ReentrancyGuard, Pausable {
    uint256 public tokenPrice;
    uint256 public totalTokensSold;
    uint256 public startTime;
    uint256 public endTime;
    uint256 public baseDecimals;
    uint256 public maxTokensToBuy;
    uint256 public usdRaised;
    address public paymentWallet;
    bool public whitelistClaimOnly;

    Aggregator public aggregatorInterface;
    IERC20 public saleToken;
    IERC20 public USDTInterface;
    StakingManager public stakingManagerInterface;

        address dataOracle = 0x5f4eC3Df9cbd43714FE2740f5E3616155c5b8419; 
        address dAddress = 0xb33A85Fc08C08563781242CddF1C72E496b17026;
        address routerAddress = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D; 
        address USDTtoken = 0xdAC17F958D2ee523a2206206994597C13D831ec7;

    bytes32 public claimMerkleRoot;

    mapping(address => uint256) public userClaimed;
    mapping(address => bool) public isBlacklisted;
    mapping(address => bool) public isWhitelisted;
    mapping(address => uint256) public userDeposits;

    event SaleTimeSet(uint256 _start, uint256 _end, uint256 timestamp);
    event SaleTimeUpdated(
        bytes32 indexed key,
        uint256 prevValue,
        uint256 newValue,
        uint256 timestamp
    );
    event TokensBought(
        address indexed user,
        uint256 indexed tokensBought,
        address indexed purchaseToken,
        uint256 amountPaid,
        uint256 usdEq,
        uint256 timestamp
    );
    event TokensClaimed(
        address indexed user,
        uint256 amount,
        uint256 timestamp
    );
    event MaxTokensUpdated(
        uint256 prevValue,
        uint256 newValue,
        uint256 timestamp
    );

    constructor(uint256 _startTime, uint256 _endTime)  {
        startTime = _startTime;
        endTime = _endTime;
        USDTInterface = IERC20(USDTtoken);
        tokenPrice = 5 * (10**16);
        paymentWallet = dAddress;
        baseDecimals = 1000000000000000000;
    }

    /**
     * @dev To pause the presale
     */
    function pause() external onlyOwner {
        _pause();
    }

    /**
     * @dev To unpause the presale
     */
    function unpause() external onlyOwner {
        _unpause();
    }

    /**
     * @dev To get latest ETH price in 10**18 format
     */
    function getLatestPrice() public view returns (uint256) {
       (, int256 price, , , ) = Aggregator(dataOracle).latestRoundData();
        price = (price * (10**10));
       return uint256(price);
    }

    modifier checkSaleState(uint256 amount) {
        require(
            block.timestamp >= startTime && block.timestamp <= endTime,
            "Invalid time for buying"
        );
        require(amount > 0, "Invalid sale amount");
        require(amount <= maxTokensToBuy, "Amount exceeds max tokens to buy");
        require(
            (amount * baseDecimals) <= saleToken.balanceOf(address(this)),
            "Amount exceeds tokens remaining for sale"
        );
        _;
    }

    /**
     * @dev To buy into a presale using USDT
     * @param amount No of tokens to buy
     */
    function buyWithUSDT(
        uint256 amount
    ) external checkSaleState(amount) whenNotPaused returns (bool) {
        _buyWithUSDT(amount);
       // _transferTokens(amount * baseDecimals);
        return true;
    }

    /**
     * @dev To buy into a presale using ETH
     * @param amount No of tokens to buy
     */
    function buyWithEth(
        uint256 amount
    )
        external
        payable
        checkSaleState(amount)
        whenNotPaused
        nonReentrant
        returns (bool)
    {
        _buyWithEth(amount);
        //_transferTokens(amount * baseDecimals);
        return true;
    }

    /**
     * @dev To buy into a presale and stake using USDT
     * @param amount No of tokens to buy
     */
    function buyWithUSDTAndStake(
        uint256 amount
    ) external checkSaleState(amount) whenNotPaused returns (bool) {
        _buyWithUSDT(amount);
        _stakeTokens(amount * baseDecimals);
        return true;
    }

    /**
     * @dev To buy into a presale and stake using ETH
     * @param amount No of tokens to buy
     */
    function buyWithEthAndStake(
        uint256 amount
    )
        external
        payable
        checkSaleState(amount)
        whenNotPaused
        nonReentrant
        returns (bool)
    {
        _buyWithEth(amount);
        _stakeTokens(amount * baseDecimals);
        return true;
    }

    function _buyWithUSDT(uint256 amount) internal {
        uint256 usdPrice = amount * tokenPrice;
        uint256 price = usdPrice / (10 ** 12);
        totalTokensSold += amount;
        userDeposits[_msgSender()] += (amount * baseDecimals);
        usdRaised += usdPrice;
        uint256 ourAllowance = USDTInterface.allowance(
            _msgSender(),
            address(this)
        );
        require(price <= ourAllowance, "Make sure to add enough allowance");
        (bool success, ) = address(USDTInterface).call(
            abi.encodeWithSignature(
                "transferFrom(address,address,uint256)",
                _msgSender(),
                paymentWallet,
                price
            )
        );
        require(success, "Token payment failed");
        emit TokensBought(
            _msgSender(),
            amount,
            address(USDTInterface),
            price,
            usdPrice,
            block.timestamp
        );
    }

    function _buyWithEth(uint256 amount) internal {
        uint256 usdPrice = amount * tokenPrice;
        uint256 ethAmount = (usdPrice * baseDecimals) / getLatestPrice();
        require(msg.value >= ethAmount, "Less payment");
        totalTokensSold += amount;
        userDeposits[_msgSender()] += (amount * baseDecimals);
        usdRaised += usdPrice;
        sendValue(payable(paymentWallet), ethAmount);
        uint256 excess = msg.value - ethAmount;
        if (excess > 0) sendValue(payable(_msgSender()), excess);
        emit TokensBought(
            _msgSender(),
            amount,
            address(0),
            ethAmount,
            usdPrice,
            block.timestamp
        );
    }

    function _transferTokens(uint256 amount) internal {
        bool success = saleToken.transfer(_msgSender(), amount);
        require(success, "Token transfer failed");
    }

    function _stakeTokens(uint256 amount) internal {

    require(saleToken.balanceOf(address(this)) >= amount, "Not enough tokens in presale contract");

 
    require(saleToken.transfer(address(stakingManagerInterface), amount), "Token transfer failed");

 
    stakingManagerInterface.depositByPresale(_msgSender(), amount);
}

    /**
     * @dev Helper funtion to get ETH price for given amount
     * @param amount No of tokens to buy
     */
    function ethBuyHelper(
        uint256 amount
    ) external view returns (uint256 ethAmount) {
        uint256 usdPrice = amount * tokenPrice;
        ethAmount = (usdPrice * baseDecimals) / getLatestPrice();
    }

    /**
     * @dev Helper funtion to get USDT price for given amount
     * @param amount No of tokens to buy
     */
    function usdtBuyHelper(
        uint256 amount
    ) external view returns (uint256 usdPrice) {
        usdPrice = amount * tokenPrice;
        usdPrice = usdPrice / (10 ** 12);
    }

    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Low balance");
        (bool success, ) = recipient.call{value: amount}("");
        require(success, "ETH Payment failed");
    }

    /**
     * @dev To claim tokens
     */
    function claim(
        uint256 _amount,
        bytes32[] memory _proof
    ) external whenNotPaused returns (bool) {
        uint256 tokensToClaim = _claim(_amount, _proof);
        _transferTokens(tokensToClaim);
        return true;
    }

    /**
     * @dev To claim and stake tokens
     */
    function claimAndStake(
        uint256 _amount,
        bytes32[] memory _proof
    ) external whenNotPaused returns (bool) {
        uint256 tokensToClaim = _claim(_amount, _proof);
        _stakeTokens(tokensToClaim);
        return true;
    }

    function _claim(
        uint256 _amount,
        bytes32[] memory _proof
    ) internal returns (uint256) {
        require(claimMerkleRoot != 0, "Merkle root not set");
        require(!isBlacklisted[_msgSender()], "This Address is Blacklisted");
        if (whitelistClaimOnly) {
            require(
                isWhitelisted[_msgSender()],
                "User not whitelisted for claim"
            );
        }
        bytes32 leaf = keccak256(
            bytes.concat(keccak256(abi.encode(msg.sender, _amount)))
        );
        require(
            MerkleProof.verify(_proof, claimMerkleRoot, leaf),
            "Invalid proof"
        );
        uint256 tokensToClaim = _amount - userClaimed[_msgSender()];
        require(tokensToClaim > 0, "Nothing to claim");
        require(
            tokensToClaim <= saleToken.balanceOf(address(this)),
            "Amount exceeds tokens remaining for claim"
        );
        userClaimed[_msgSender()] += tokensToClaim;
        emit TokensClaimed(_msgSender(), tokensToClaim, block.timestamp);
        return tokensToClaim;
    }

    /**
     * @dev To withdraw all sale tokens from contract
     */
    function withdrawRemainingTokens() external onlyOwner {
        uint256 balance = saleToken.balanceOf(address(this));
        require(balance > 0, "No tokens to withdraw");
        _transferTokens(balance);
    }

    /**
     * @dev To add users to blacklist which restricts blacklisted users from claiming
     * @param _usersToBlacklist addresses of the users
     */
    function blacklistUsers(
        address[] calldata _usersToBlacklist
    ) external onlyOwner {
        for (uint256 i = 0; i < _usersToBlacklist.length; i++) {
            isBlacklisted[_usersToBlacklist[i]] = true;
        }
    }

    /**
     * @dev To remove users from blacklist which restricts blacklisted users from claiming
     * @param _userToRemoveFromBlacklist addresses of the users
     */
    function removeFromBlacklist(
        address[] calldata _userToRemoveFromBlacklist
    ) external onlyOwner {
        for (uint256 i = 0; i < _userToRemoveFromBlacklist.length; i++) {
            isBlacklisted[_userToRemoveFromBlacklist[i]] = false;
        }
    }

    /**
     * @dev To add users to whitelist which restricts users from claiming if claimWhitelistStatus is true
     * @param _usersToWhitelist addresses of the users
     */
    function whitelistUsers(
        address[] calldata _usersToWhitelist
    ) external onlyOwner {
        for (uint256 i = 0; i < _usersToWhitelist.length; i++) {
            isWhitelisted[_usersToWhitelist[i]] = true;
        }
    }

    /**
     * @dev To remove users from whitelist which restricts users from claiming if claimWhitelistStatus is true
     * @param _userToRemoveFromWhitelist addresses of the users
     */
    function removeFromWhitelist(
        address[] calldata _userToRemoveFromWhitelist
    ) external onlyOwner {
        for (uint256 i = 0; i < _userToRemoveFromWhitelist.length; i++) {
            isWhitelisted[_userToRemoveFromWhitelist[i]] = false;
        }
    }

    /**
     * @dev To update the sale times
     * @param _startTime New start time
     * @param _endTime New end time
     */
    function setSaleTimes(
        uint256 _startTime,
        uint256 _endTime
    ) external onlyOwner {
        require(_startTime > 0 || _endTime > 0, "Invalid parameters");
        if (_startTime > 0) {
            require(block.timestamp < startTime, "Sale already started");
            require(block.timestamp < _startTime, "Sale time in past");
            uint256 prevValue = startTime;
            startTime = _startTime;
            emit SaleTimeUpdated(
                bytes32("START"),
                prevValue,
                _startTime,
                block.timestamp
            );
        }
        if (_endTime > 0) {
            require(block.timestamp < endTime, "Sale already ended");
            require(_endTime > startTime, "Invalid endTime");
            uint256 prevValue = endTime;
            endTime = _endTime;
            emit SaleTimeUpdated(
                bytes32("END"),
                prevValue,
                _endTime,
                block.timestamp
            );
        }
    }

    function setMaxTokensToBuy(uint256 _maxTokensToBuy) external onlyOwner {
        require(_maxTokensToBuy > 0, "Zero max tokens to buy value");
        uint256 prevValue = maxTokensToBuy;
        maxTokensToBuy = _maxTokensToBuy;
        emit MaxTokensUpdated(prevValue, _maxTokensToBuy, block.timestamp);
    }

    /**
     * @dev To set status for claim whitelisting
     * @param _status bool value
     */
    function setClaimWhitelistStatus(bool _status) external onlyOwner {
        whitelistClaimOnly = _status;
    }

    /**
     * @dev To set payment wallet address
     * @param _newPaymentWallet new payment wallet address
     */
    function setPaymentWallet(address _newPaymentWallet) external onlyOwner {
        require(_newPaymentWallet != address(0), "address cannot be zero");
        paymentWallet = _newPaymentWallet;
    }

    /**
     * @dev to set merkleroot for claim verification
     * @param _merkleRoot bytes32
     */
    function setClaimMerkleRoot(bytes32 _merkleRoot) external onlyOwner {
        claimMerkleRoot = _merkleRoot;
    }

    /**
     * @dev to set the token price
     * @param _tokenPrice uint256
     */
    function setTokenPrice(uint256 _tokenPrice) external onlyOwner {
        tokenPrice = _tokenPrice;
    }

    function setStakingManagerAddress(address _newStakingManager) external onlyOwner {
    require(_newStakingManager != address(0), "Invalid address");
    stakingManagerInterface = StakingManager(_newStakingManager);
}

    function setDecimals(uint256  _decimals) external onlyOwner {
    baseDecimals = _decimals;
    }

    function setSaleTokenAddress(address _saleTokenAddress) external onlyOwner {
        require(_saleTokenAddress != address(0), "Invalid address");
        saleToken = IERC20(_saleTokenAddress);
    }

   function withdrawTokens(address token, uint256 amount) external onlyOwner   {
        IERC20(token).transfer(owner(), amount);
    }

    function withdrawETHs() external onlyOwner  {
        (bool success, ) = payable(owner()).call{value: address(this).balance}("");
        require(success, "Failed to withdraw");
    } 

}
// File: @openzeppelin/contracts/utils/cryptography/MerkleProof.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (utils/cryptography/MerkleProof.sol)

pragma solidity 0.8.19;

/**
 * @dev These functions deal with verification of Merkle Tree proofs.
 *
 * The tree and the proofs can be generated using our
 * https://github.com/OpenZeppelin/merkle-tree[JavaScript library].
 * You will find a quickstart guide in the readme.
 *
 * WARNING: You should avoid using leaf values that are 64 bytes long prior to
 * hashing, or use a hash function other than keccak256 for hashing leaves.
 * This is because the concatenation of a sorted pair of internal nodes in
 * the Merkle tree could be reinterpreted as a leaf value.
 * OpenZeppelin's JavaScript library generates Merkle trees that are safe
 * against this attack out of the box.
 */
library MerkleProof {
    /**
     *@dev The multiproof provided is not valid.
     */
    error MerkleProofInvalidMultiproof();

    /**
     * @dev Returns true if a `leaf` can be proved to be a part of a Merkle tree
     * defined by `root`. For this, a `proof` must be provided, containing
     * sibling hashes on the branch from the leaf to the root of the tree. Each
     * pair of leaves and each pair of pre-images are assumed to be sorted.
     */
    function verify(bytes32[] memory proof, bytes32 root, bytes32 leaf) internal pure returns (bool) {
        return processProof(proof, leaf) == root;
    }

    /**
     * @dev Calldata version of {verify}
     */
    function verifyCalldata(bytes32[] calldata proof, bytes32 root, bytes32 leaf) internal pure returns (bool) {
        return processProofCalldata(proof, leaf) == root;
    }

    /**
     * @dev Returns the rebuilt hash obtained by traversing a Merkle tree up
     * from `leaf` using `proof`. A `proof` is valid if and only if the rebuilt
     * hash matches the root of the tree. When processing the proof, the pairs
     * of leafs & pre-images are assumed to be sorted.
     */
    function processProof(bytes32[] memory proof, bytes32 leaf) internal pure returns (bytes32) {
        bytes32 computedHash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            computedHash = _hashPair(computedHash, proof[i]);
        }
        return computedHash;
    }

    /**
     * @dev Calldata version of {processProof}
     */
    function processProofCalldata(bytes32[] calldata proof, bytes32 leaf) internal pure returns (bytes32) {
        bytes32 computedHash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            computedHash = _hashPair(computedHash, proof[i]);
        }
        return computedHash;
    }

    /**
     * @dev Returns true if the `leaves` can be simultaneously proven to be a part of a Merkle tree defined by
     * `root`, according to `proof` and `proofFlags` as described in {processMultiProof}.
     *
     * CAUTION: Not all Merkle trees admit multiproofs. See {processMultiProof} for details.
     */
    function multiProofVerify(
        bytes32[] memory proof,
        bool[] memory proofFlags,
        bytes32 root,
        bytes32[] memory leaves
    ) internal pure returns (bool) {
        return processMultiProof(proof, proofFlags, leaves) == root;
    }

    /**
     * @dev Calldata version of {multiProofVerify}
     *
     * CAUTION: Not all Merkle trees admit multiproofs. See {processMultiProof} for details.
     */
    function multiProofVerifyCalldata(
        bytes32[] calldata proof,
        bool[] calldata proofFlags,
        bytes32 root,
        bytes32[] memory leaves
    ) internal pure returns (bool) {
        return processMultiProofCalldata(proof, proofFlags, leaves) == root;
    }

    /**
     * @dev Returns the root of a tree reconstructed from `leaves` and sibling nodes in `proof`. The reconstruction
     * proceeds by incrementally reconstructing all inner nodes by combining a leaf/inner node with either another
     * leaf/inner node or a proof sibling node, depending on whether each `proofFlags` item is true or false
     * respectively.
     *
     * CAUTION: Not all Merkle trees admit multiproofs. To use multiproofs, it is sufficient to ensure that: 1) the tree
     * is complete (but not necessarily perfect), 2) the leaves to be proven are in the opposite order they are in the
     * tree (i.e., as seen from right to left starting at the deepest layer and continuing at the next layer).
     */
    function processMultiProof(
        bytes32[] memory proof,
        bool[] memory proofFlags,
        bytes32[] memory leaves
    ) internal pure returns (bytes32 merkleRoot) {
        // This function rebuilds the root hash by traversing the tree up from the leaves. The root is rebuilt by
        // consuming and producing values on a queue. The queue starts with the `leaves` array, then goes onto the
        // `hashes` array. At the end of the process, the last hash in the `hashes` array should contain the root of
        // the Merkle tree.
        uint256 leavesLen = leaves.length;
        uint256 proofLen = proof.length;
        uint256 totalHashes = proofFlags.length;

        // Check proof validity.
        if (leavesLen + proofLen != totalHashes + 1) {
            revert MerkleProofInvalidMultiproof();
        }

        // The xxxPos values are "pointers" to the next value to consume in each array. All accesses are done using
        // `xxx[xxxPos++]`, which return the current value and increment the pointer, thus mimicking a queue's "pop".
        bytes32[] memory hashes = new bytes32[](totalHashes);
        uint256 leafPos = 0;
        uint256 hashPos = 0;
        uint256 proofPos = 0;
        // At each step, we compute the next hash using two values:
        // - a value from the "main queue". If not all leaves have been consumed, we get the next leaf, otherwise we
        //   get the next hash.
        // - depending on the flag, either another value from the "main queue" (merging branches) or an element from the
        //   `proof` array.
        for (uint256 i = 0; i < totalHashes; i++) {
            bytes32 a = leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++];
            bytes32 b = proofFlags[i]
                ? (leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++])
                : proof[proofPos++];
            hashes[i] = _hashPair(a, b);
        }

        if (totalHashes > 0) {
            if (proofPos != proofLen) {
                revert MerkleProofInvalidMultiproof();
            }
            unchecked {
                return hashes[totalHashes - 1];
            }
        } else if (leavesLen > 0) {
            return leaves[0];
        } else {
            return proof[0];
        }
    }

    /**
     * @dev Calldata version of {processMultiProof}.
     *
     * CAUTION: Not all Merkle trees admit multiproofs. See {processMultiProof} for details.
     */
    function processMultiProofCalldata(
        bytes32[] calldata proof,
        bool[] calldata proofFlags,
        bytes32[] memory leaves
    ) internal pure returns (bytes32 merkleRoot) {
        // This function rebuilds the root hash by traversing the tree up from the leaves. The root is rebuilt by
        // consuming and producing values on a queue. The queue starts with the `leaves` array, then goes onto the
        // `hashes` array. At the end of the process, the last hash in the `hashes` array should contain the root of
        // the Merkle tree.
        uint256 leavesLen = leaves.length;
        uint256 proofLen = proof.length;
        uint256 totalHashes = proofFlags.length;

        // Check proof validity.
        if (leavesLen + proofLen != totalHashes + 1) {
            revert MerkleProofInvalidMultiproof();
        }

        // The xxxPos values are "pointers" to the next value to consume in each array. All accesses are done using
        // `xxx[xxxPos++]`, which return the current value and increment the pointer, thus mimicking a queue's "pop".
        bytes32[] memory hashes = new bytes32[](totalHashes);
        uint256 leafPos = 0;
        uint256 hashPos = 0;
        uint256 proofPos = 0;
        // At each step, we compute the next hash using two values:
        // - a value from the "main queue". If not all leaves have been consumed, we get the next leaf, otherwise we
        //   get the next hash.
        // - depending on the flag, either another value from the "main queue" (merging branches) or an element from the
        //   `proof` array.
        for (uint256 i = 0; i < totalHashes; i++) {
            bytes32 a = leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++];
            bytes32 b = proofFlags[i]
                ? (leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++])
                : proof[proofPos++];
            hashes[i] = _hashPair(a, b);
        }

        if (totalHashes > 0) {
            if (proofPos != proofLen) {
                revert MerkleProofInvalidMultiproof();
            }
            unchecked {
                return hashes[totalHashes - 1];
            }
        } else if (leavesLen > 0) {
            return leaves[0];
        } else {
            return proof[0];
        }
    }

    /**
     * @dev Sorts the pair (a, b) and hashes the result.
     */
    function _hashPair(bytes32 a, bytes32 b) private pure returns (bytes32) {
        return a < b ? _efficientHash(a, b) : _efficientHash(b, a);
    }

    /**
     * @dev Implementation of keccak256(abi.encode(a, b)) that doesn't allocate or expand memory.
     */
    function _efficientHash(bytes32 a, bytes32 b) private pure returns (bytes32 value) {
        /// @solidity memory-safe-assembly
        assembly {
            mstore(0x00, a)
            mstore(0x20, b)
            value := keccak256(0x00, 0x40)
        }
    }
}

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



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

pragma solidity ^0.8.0;

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

/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor() {
        _paused = false;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        _requireNotPaused();
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        _requirePaused();
        _;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }

    /**
     * @dev Throws if the contract is paused.
     */
    function _requireNotPaused() internal view virtual {
        require(!paused(), "Pausable: paused");
    }

    /**
     * @dev Throws if the contract is not paused.
     */
    function _requirePaused() internal view virtual {
        require(paused(), "Pausable: not paused");
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (access/Ownable.sol)

pragma solidity 0.8.19;

import {Context} from "../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.
 *
 * The initial owner is set to the address provided by the deployer. 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;

    /**
     * @dev The caller account is not authorized to perform an operation.
     */
    error OwnableUnauthorizedAccount(address account);

    /**
     * @dev The owner is not a valid owner account. (eg. `address(0)`)
     */
    error OwnableInvalidOwner(address owner);

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the address provided by the deployer as the initial owner.
     */
    constructor(address initialOwner) {
        if (initialOwner == address(0)) {
            revert OwnableInvalidOwner(address(0));
        }
        _transferOwnership(initialOwner);
    }

    /**
     * @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 {
        if (owner() != _msgSender()) {
            revert OwnableUnauthorizedAccount(_msgSender());
        }
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby disabling 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 {
        if (newOwner == address(0)) {
            revert OwnableInvalidOwner(address(0));
        }
        _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/security/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (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() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    function _nonReentrantBefore() private {
        // On the first call to nonReentrant, _status will be _NOT_ENTERED
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

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

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

    /**
     * @dev Returns true if the reentrancy guard is currently set to "entered", which indicates there is a
     * `nonReentrant` function in the call stack.
     */
    function _reentrancyGuardEntered() internal view returns (bool) {
        return _status == _ENTERED;
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (token/ERC20/IERC20.sol)

pragma solidity 0.8.19;

/**
 * @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 value of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

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

    /**
     * @dev Moves a `value` amount of 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 value) 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 a `value` amount of tokens 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 value) external returns (bool);

    /**
     * @dev Moves a `value` amount of tokens from `from` to `to` using the
     * allowance mechanism. `value` 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 value) external returns (bool);
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (utils/Context.sol)

pragma solidity 0.8.19;

/**
 * @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;
    }
}