Contract Address Details

// File @openzeppelin/contracts/token/ERC20/IERC20.sol@v4.5.0

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

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

    /**
     * @dev Moves `amount` tokens from the caller's account to `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);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
}

// File @openzeppelin/contracts/utils/Address.sol@v4.5.0

// OpenZeppelin Contracts (last updated v4.5.0) (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

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

// File @openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol@v4.5.0

// OpenZeppelin Contracts v4.4.1 (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using Address for address;

    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(token.transfer.selector, to, value)
        );
    }

    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(token.transferFrom.selector, from, to, value)
        );
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(token.approve.selector, spender, value)
        );
    }

    function safeIncreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender) + value;
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(
                token.approve.selector,
                spender,
                newAllowance
            )
        );
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(
                oldAllowance >= value,
                "SafeERC20: decreased allowance below zero"
            );
            uint256 newAllowance = oldAllowance - value;
            _callOptionalReturn(
                token,
                abi.encodeWithSelector(
                    token.approve.selector,
                    spender,
                    newAllowance
                )
            );
        }
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(
            data,
            "SafeERC20: low-level call failed"
        );
        if (returndata.length > 0) {
            // Return data is optional
            require(
                abi.decode(returndata, (bool)),
                "SafeERC20: ERC20 operation did not succeed"
            );
        }
    }
}

// File @openzeppelin/contracts/utils/Context.sol@v4.5.0

// 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/access/Ownable.sol@v4.5.0

// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)

pragma solidity ^0.8.0;

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

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _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/security/ReentrancyGuard.sol@v4.5.0

// 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/utils/math/SafeMath.sol@v4.5.0

// OpenZeppelin Contracts v4.4.1 (utils/math/SafeMath.sol)

pragma solidity ^0.8.0;

// CAUTION
// This version of SafeMath should only be used with Solidity 0.8 or later,
// because it relies on the compiler's built in overflow checks.

/**
 * @dev Wrappers over Solidity's arithmetic operations.
 *
 * NOTE: `SafeMath` is generally not needed starting with Solidity 0.8, since the compiler
 * now has built in overflow checking.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        unchecked {
            uint256 c = a + b;
            if (c < a) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        unchecked {
            if (b > a) return (false, 0);
            return (true, a - b);
        }
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        unchecked {
            // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
            // benefit is lost if 'b' is also tested.
            // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
            if (a == 0) return (true, 0);
            uint256 c = a * b;
            if (c / a != b) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a / b);
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a % b);
        }
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        return a + b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        return a * b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator.
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b <= a, errorMessage);
            return a - b;
        }
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a / b;
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a % b;
        }
    }
}

// File contracts/yield-farm/libraries/IBoringERC20.sol

pragma solidity 0.8.16;

interface IBoringERC20 {
    function mint(address to, uint256 amount) external;

    function totalSupply() external view returns (uint256);

    function balanceOf(address account) external view returns (uint256);

    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );

    /// @notice EIP 2612
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;
}

// File contracts/yield-farm/libraries/BoringERC20.sol

pragma solidity 0.8.16;

// solhint-disable avoid-low-level-calls
library BoringERC20 {
    bytes4 private constant SIG_SYMBOL = 0x95d89b41; // symbol()
    bytes4 private constant SIG_NAME = 0x06fdde03; // name()
    bytes4 private constant SIG_DECIMALS = 0x313ce567; // decimals()
    bytes4 private constant SIG_TRANSFER = 0xa9059cbb; // transfer(address,uint256)
    bytes4 private constant SIG_TRANSFER_FROM = 0x23b872dd; // transferFrom(address,address,uint256)

    function returnDataToString(bytes memory data)
        internal
        pure
        returns (string memory)
    {
        if (data.length >= 64) {
            return abi.decode(data, (string));
        } else if (data.length == 32) {
            uint8 i = 0;
            while (i < 32 && data[i] != 0) {
                i++;
            }
            bytes memory bytesArray = new bytes(i);
            for (i = 0; i < 32 && data[i] != 0; i++) {
                bytesArray[i] = data[i];
            }
            return string(bytesArray);
        } else {
            return "???";
        }
    }

    /// @notice Provides a safe ERC20.symbol version which returns '???' as fallback string.
    /// @param token The address of the ERC-20 token contract.
    /// @return (string) Token symbol.
    function safeSymbol(IBoringERC20 token)
        internal
        view
        returns (string memory)
    {
        (bool success, bytes memory data) = address(token).staticcall(
            abi.encodeWithSelector(SIG_SYMBOL)
        );
        return success ? returnDataToString(data) : "???";
    }

    /// @notice Provides a safe ERC20.name version which returns '???' as fallback string.
    /// @param token The address of the ERC-20 token contract.
    /// @return (string) Token name.
    function safeName(IBoringERC20 token)
        internal
        view
        returns (string memory)
    {
        (bool success, bytes memory data) = address(token).staticcall(
            abi.encodeWithSelector(SIG_NAME)
        );
        return success ? returnDataToString(data) : "???";
    }

    /// @notice Provides a safe ERC20.decimals version which returns '18' as fallback value.
    /// @param token The address of the ERC-20 token contract.
    /// @return (uint8) Token decimals.
    function safeDecimals(IBoringERC20 token) internal view returns (uint8) {
        (bool success, bytes memory data) = address(token).staticcall(
            abi.encodeWithSelector(SIG_DECIMALS)
        );
        return success && data.length == 32 ? abi.decode(data, (uint8)) : 18;
    }

    /// @notice Provides a safe ERC20.transfer version for different ERC-20 implementations.
    /// Reverts on a failed transfer.
    /// @param token The address of the ERC-20 token.
    /// @param to Transfer tokens to.
    /// @param amount The token amount.
    function safeTransfer(
        IBoringERC20 token,
        address to,
        uint256 amount
    ) internal {
        (bool success, bytes memory data) = address(token).call(
            abi.encodeWithSelector(SIG_TRANSFER, to, amount)
        );
        require(
            success && (data.length == 0 || abi.decode(data, (bool))),
            "BoringERC20: Transfer failed"
        );
    }

    /// @notice Provides a safe ERC20.transferFrom version for different ERC-20 implementations.
    /// Reverts on a failed transfer.
    /// @param token The address of the ERC-20 token.
    /// @param from Transfer tokens from.
    /// @param to Transfer tokens to.
    /// @param amount The token amount.
    function safeTransferFrom(
        IBoringERC20 token,
        address from,
        address to,
        uint256 amount
    ) internal {
        (bool success, bytes memory data) = address(token).call(
            abi.encodeWithSelector(SIG_TRANSFER_FROM, from, to, amount)
        );
        require(
            success && (data.length == 0 || abi.decode(data, (bool))),
            "BoringERC20: TransferFrom failed"
        );
    }
}

// File contracts/yield-farm/IYodedexPair.sol

pragma solidity 0.8.16;

interface IYodedexPair {
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    function initialize(address, address) external;
}

// File contracts/yield-farm/YodeChef.sol

pragma solidity ^0.8.0;

contract YodeChef is Ownable, ReentrancyGuard {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;
    using BoringERC20 for IBoringERC20;

    // Info of each user.
    struct UserInfo {
        uint256 amount; // How many LP tokens the user has provided.
        uint256 rewardDebt; // Reward debt. See explanation below.
        uint256 rewardLockedUp; // Reward locked up.
        uint256 nextHarvestUntil; // When can the user harvest again.
    }

    // Info of each pool.
    struct PoolInfo {
        IERC20 lpToken; // Address of LP token contract.
        uint256 allocPoint; // How many allocation points assigned to this pool. Yode to distribute per block.
        uint256 lastRewardBlock; // Last block number that Yode distribution occurs.
        uint256 accYodePerShare; // Accumulated Yode per share, times 1e12. See below.
        uint16 depositFeeBP; // Deposit fee in basis points
        uint256 harvestInterval; // Harvest interval in seconds
        uint256 totalLp; // Total token in Pool
    }

    IBoringERC20 public yode;

    // The operator can only update EmissionRate and AllocPoint to protect tokenomics
    //i.e some wrong setting and a pools get too much allocation accidentally
    address private _operator;

    // Yode tokens created per block
    uint256 public yodePerBlock;

    // Max harvest interval: 90 days
    uint256 public constant MAXIMUM_HARVEST_INTERVAL = 90 days;

    // Maximum deposit fee rate: 10%
    uint16 public constant MAXIMUM_DEPOSIT_FEE_RATE = 1000;

    // Info of each pool
    PoolInfo[] public poolInfo;

    // Info of each user that stakes LP tokens.
    mapping(uint256 => mapping(address => UserInfo)) public userInfo;

    // Total allocation points. Must be the sum of all allocation points in all pools.
    uint256 public totalAllocPoint = 0;

    // The block number when Yode mining starts.
    uint256 public startBlock;

    // Total locked up rewards
    uint256 public totalLockedUpRewards;

    // Total Yode in Yode Pools (can be multiple pools)
    uint256 public totalYodeInPools = 0;

    // Control support for EIP-2771 Meta Transactions
    bool public metaTxnsEnabled = false;

    // Team address.
    address public marketingAddress;

    // Percentage of pool rewards that goto the team.
    uint256 public marketingPercent;

    event Deposit(address indexed user, uint256 indexed pid, uint256 amount);
    event Withdraw(address indexed user, uint256 indexed pid, uint256 amount);
    event EmergencyWithdraw(
        address indexed user,
        uint256 indexed pid,
        uint256 amount
    );
    event EmissionRateUpdated(
        address indexed caller,
        uint256 previousAmount,
        uint256 newAmount
    );
    event RewardLockedUp(
        address indexed user,
        uint256 indexed pid,
        uint256 amountLockedUp
    );
    event OperatorTransferred(
        address indexed previousOperator,
        address indexed newOperator
    );

    event AllocPointsUpdated(
        address indexed caller,
        uint256 previousAmount,
        uint256 newAmount
    );
    event MetaTxnsEnabled(address indexed caller);
    event MetaTxnsDisabled(address indexed caller);

    event SetmarketingAddress(
        address indexed oldAddress,
        address indexed newAddress
    );

    event SetmarketingPercent(uint256 oldPercent, uint256 newPercent);

    modifier validatePoolByPid(uint256 _pid) {
        require(_pid < poolInfo.length, "Pool does not exist");
        _;
    }

    modifier onlyOperator() {
        require(
            _operator == msg.sender,
            "Operator: caller is not the operator"
        );
        _;
    }

    constructor(
        IBoringERC20 _yode,
        uint256 _yodePerBlock,
        address _marketingAddress,
        uint256 _marketingPercent
    ) {
        require(
            0 <= _marketingPercent && _marketingPercent <= 100,
            "constructor: invalid team percent value"
        );
        //StartBlock always many years later from contract construct, will be set later in StartFarming function
        startBlock = block.number + (10 * 365 * 24 * 60 * 60);

        yode = _yode;
        yodePerBlock = _yodePerBlock;

        marketingAddress = _marketingAddress;
        marketingPercent = _marketingPercent;

        _operator = msg.sender;
        emit OperatorTransferred(address(0), _operator);
    }

    function operator() public view returns (address) {
        return _operator;
    }

    // Return reward multiplier over the given _from to _to block.
    function getMultiplier(uint256 _from, uint256 _to)
        public
        pure
        returns (uint256)
    {
        return _to.sub(_from);
    }

    function transferOperator(address newOperator) public onlyOperator {
        require(
            newOperator != address(0),
            "TransferOperator: new operator is the zero address"
        );
        emit OperatorTransferred(_operator, newOperator);
        _operator = newOperator;
    }

    // Set farming start, can call only once
    function startFarming() public onlyOwner {
        require(block.number < startBlock, "Error::Farm started already");

        uint256 length = poolInfo.length;
        for (uint256 pid = 0; pid < length; ++pid) {
            PoolInfo storage pool = poolInfo[pid];
            pool.lastRewardBlock = block.number;
        }

        startBlock = block.number;
    }

    function poolLength() external view returns (uint256) {
        return poolInfo.length;
    }

    // Add a new lp to the pool. Can only be called by the owner.
    // Can add multiple pool with same lp token without messing up rewards, because each pool's balance is tracked using its own totalLp
    function add(
        uint256 _allocPoint,
        IERC20 _lpToken,
        uint16 _depositFeeBP,
        uint256 _harvestInterval,
        bool _withUpdate
    ) public onlyOwner {
        require(
            _depositFeeBP <= MAXIMUM_DEPOSIT_FEE_RATE,
            "add: deposit fee too high"
        );
        require(
            _harvestInterval <= MAXIMUM_HARVEST_INTERVAL,
            "add: invalid harvest interval"
        );
        if (_withUpdate) {
            massUpdatePools();
        }
        uint256 lastRewardBlock = block.number > startBlock
            ? block.number
            : startBlock;
        totalAllocPoint = totalAllocPoint.add(_allocPoint);
        poolInfo.push(
            PoolInfo({
                lpToken: _lpToken,
                allocPoint: _allocPoint,
                lastRewardBlock: lastRewardBlock,
                accYodePerShare: 0,
                depositFeeBP: _depositFeeBP,
                harvestInterval: _harvestInterval,
                totalLp: 0
            })
        );
    }

    // Update the given pool's Yode allocation point and deposit fee. Can only be called by the owner.
    function set(
        uint256 _pid,
        uint256 _allocPoint,
        uint16 _depositFeeBP,
        uint256 _harvestInterval,
        bool _withUpdate
    ) public onlyOwner {
        require(
            _depositFeeBP <= MAXIMUM_DEPOSIT_FEE_RATE,
            "set: deposit fee too high"
        );
        require(
            _harvestInterval <= MAXIMUM_HARVEST_INTERVAL,
            "set: invalid harvest interval"
        );
        if (_withUpdate) {
            massUpdatePools();
        }
        totalAllocPoint = totalAllocPoint.sub(poolInfo[_pid].allocPoint).add(
            _allocPoint
        );
        poolInfo[_pid].allocPoint = _allocPoint;
        poolInfo[_pid].depositFeeBP = _depositFeeBP;
        poolInfo[_pid].harvestInterval = _harvestInterval;
    }

    // View function to see pending Yode on frontend.
    function pendingYode(uint256 _pid, address _user)
        external
        view
        returns (uint256)
    {
        PoolInfo storage pool = poolInfo[_pid];
        UserInfo storage user = userInfo[_pid][_user];
        uint256 accYodePerShare = pool.accYodePerShare;
        uint256 lpSupply = pool.lpToken.balanceOf(address(this));

        if (block.number > pool.lastRewardBlock && lpSupply != 0) {
            uint256 multiplier = getMultiplier(
                pool.lastRewardBlock,
                block.number
            );
            uint256 yodeReward = multiplier
                .mul(yodePerBlock)
                .mul(pool.allocPoint)
                .div(totalAllocPoint);
            accYodePerShare = accYodePerShare.add(
                yodeReward.mul(1e12).div(lpSupply)
            );
        }

        uint256 pending = user.amount.mul(accYodePerShare).div(1e12).sub(
            user.rewardDebt
        );
        return pending.add(user.rewardLockedUp);
    }

    // View function to see if user can harvest Yode.
    function canHarvest(uint256 _pid, address _user)
        public
        view
        returns (bool)
    {
        UserInfo storage user = userInfo[_pid][_user];
        return
            block.number >= startBlock &&
            block.timestamp >= user.nextHarvestUntil;
    }

    // Update reward vairables for all pools. Be careful of gas spending!
    function massUpdatePools() public {
        uint256 length = poolInfo.length;
        for (uint256 pid = 0; pid < length; ++pid) {
            updatePool(pid);
        }
    }

    // Update reward variables of the given pool to be up-to-date.
    function updatePool(uint256 _pid) public {
        PoolInfo storage pool = poolInfo[_pid];
        if (block.number <= pool.lastRewardBlock) {
            return;
        }

        uint256 lpSupply = pool.totalLp;
        if (lpSupply == 0 || pool.allocPoint == 0) {
            pool.lastRewardBlock = block.number;
            return;
        }

        uint256 multiplier = getMultiplier(pool.lastRewardBlock, block.number);
        uint256 yodeReward = multiplier
            .mul(yodePerBlock)
            .mul(pool.allocPoint)
            .div(totalAllocPoint);

        uint256 lpPercent = 1000 - marketingPercent;

        yode.mint(marketingAddress, (yodeReward * marketingPercent) / 1000);
        yode.mint(address(this), (yodeReward * lpPercent) / 1000);

        pool.accYodePerShare =
            pool.accYodePerShare +
            (((yodeReward * 1e12) / pool.totalLp) * lpPercent) /
            1000;

        pool.lastRewardBlock = block.number;
    }

    function depositWithPermit(
        uint256 pid,
        uint256 amount,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) public nonReentrant validatePoolByPid(pid) {
        PoolInfo storage pool = poolInfo[pid];
        IYodedexPair pair = IYodedexPair(address(pool.lpToken));
        pair.permit(msg.sender, address(this), amount, deadline, v, r, s);
        deposit(pid, amount);
    }

    // Deposit LP tokens to MasterChef for Yode allocation.
    function deposit(uint256 _pid, uint256 _amount) public nonReentrant {
        require(
            block.number >= startBlock,
            "YodedexChef: Can not deposit before start"
        );

        PoolInfo storage pool = poolInfo[_pid];
        UserInfo storage user = userInfo[_pid][msg.sender];

        updatePool(_pid);

        payOrLockupPendingYode(_pid);

        if (_amount > 0) {
            uint256 beforeDeposit = pool.lpToken.balanceOf(address(this));
            pool.lpToken.safeTransferFrom(msg.sender, address(this), _amount);
            uint256 afterDeposit = pool.lpToken.balanceOf(address(this));

            _amount = afterDeposit.sub(beforeDeposit);

            if (pool.depositFeeBP > 0) {
                uint256 depositFee = _amount.mul(pool.depositFeeBP).div(10000);
                pool.lpToken.safeTransfer(marketingAddress, depositFee);

                _amount = _amount.sub(depositFee);
            }

            user.amount = user.amount.add(_amount);
            pool.totalLp = pool.totalLp.add(_amount);

            if (address(pool.lpToken) == address(yode)) {
                totalYodeInPools = totalYodeInPools.add(_amount);
            }
        }
        user.rewardDebt = user.amount.mul(pool.accYodePerShare).div(1e12);
        emit Deposit(msg.sender, _pid, _amount);
    }

    // Withdraw tokens
    function withdraw(uint256 _pid, uint256 _amount) public nonReentrant {
        PoolInfo storage pool = poolInfo[_pid];
        UserInfo storage user = userInfo[_pid][msg.sender];

        //this will make sure that user can only withdraw from his pool
        require(user.amount >= _amount, "Withdraw: User amount not enough");

        //Cannot withdraw more than pool's balance
        require(pool.totalLp >= _amount, "Withdraw: Pool total not enough");

        updatePool(_pid);

        payOrLockupPendingYode(_pid);

        if (_amount > 0) {
            user.amount = user.amount.sub(_amount);
            pool.totalLp = pool.totalLp.sub(_amount);
            if (address(pool.lpToken) == address(yode)) {
                totalYodeInPools = totalYodeInPools.sub(_amount);
            }
            pool.lpToken.safeTransfer(msg.sender, _amount);
        }
        user.rewardDebt = user.amount.mul(pool.accYodePerShare).div(1e12);
        emit Withdraw(msg.sender, _pid, _amount);
    }

    // Withdraw without caring about rewards. EMERGENCY ONLY.
    function emergencyWithdraw(uint256 _pid) public nonReentrant {
        PoolInfo storage pool = poolInfo[_pid];
        UserInfo storage user = userInfo[_pid][msg.sender];
        uint256 amount = user.amount;

        //Cannot withdraw more than pool's balance
        require(
            pool.totalLp >= amount,
            "EmergencyWithdraw: Pool total not enough"
        );

        user.amount = 0;
        user.rewardDebt = 0;
        user.rewardLockedUp = 0;
        user.nextHarvestUntil = 0;
        pool.totalLp = pool.totalLp.sub(amount);

        if (address(pool.lpToken) == address(yode)) {
            totalYodeInPools = totalYodeInPools.sub(amount);
        }
        pool.lpToken.safeTransfer(msg.sender, amount);

        emit EmergencyWithdraw(msg.sender, _pid, amount);
    }

    // Pay or lockup pending Yode.
    function payOrLockupPendingYode(uint256 _pid) internal {
        PoolInfo storage pool = poolInfo[_pid];
        UserInfo storage user = userInfo[_pid][msg.sender];

        if (user.nextHarvestUntil == 0 && block.number >= startBlock) {
            user.nextHarvestUntil = block.timestamp.add(pool.harvestInterval);
        }

        uint256 pending = user.amount.mul(pool.accYodePerShare).div(1e12).sub(
            user.rewardDebt
        );
        if (canHarvest(_pid, msg.sender)) {
            if (pending > 0 || user.rewardLockedUp > 0) {
                uint256 totalRewards = pending.add(user.rewardLockedUp);

                // reset lockup
                totalLockedUpRewards = totalLockedUpRewards.sub(
                    user.rewardLockedUp
                );
                user.rewardLockedUp = 0;
                user.nextHarvestUntil = block.timestamp.add(
                    pool.harvestInterval
                );

                // send rewards
                safeYodeTransfer(msg.sender, totalRewards);
            }
        } else if (pending > 0) {
            user.rewardLockedUp = user.rewardLockedUp.add(pending);
            totalLockedUpRewards = totalLockedUpRewards.add(pending);
            emit RewardLockedUp(msg.sender, _pid, pending);
        }
    }

    // Safe Yode transfer function, just in case if rounding error causes pool do not have enough Yode.
    function safeYodeTransfer(address _to, uint256 _amount) internal {
        if (yode.balanceOf(address(this)) > totalYodeInPools) {
            //YodeBal = total Yode in YodedexChef - total Yode in Yode pools, this will make sure that YodedexChef never transfer rewards from deposited Yode pools
            uint256 YodeBal = yode.balanceOf(address(this)).sub(
                totalYodeInPools
            );
            if (_amount >= YodeBal) {
                yode.safeTransfer(_to, YodeBal);
            } else if (_amount > 0) {
                yode.safeTransfer(_to, _amount);
            }
        }
    }

    // Pancake has to add hidden dummy pools in order to alter the emission, here we make it simple and transparent to all.
    function updateEmissionRate(uint256 _yodePerBlock) public onlyOperator {
        massUpdatePools();

        emit EmissionRateUpdated(msg.sender, yodePerBlock, _yodePerBlock);
        yodePerBlock = _yodePerBlock;
    }

    function updateAllocPoint(
        uint256 _pid,
        uint256 _allocPoint,
        bool _withUpdate
    ) public onlyOperator {
        if (_withUpdate) {
            massUpdatePools();
        }

        emit AllocPointsUpdated(
            msg.sender,
            poolInfo[_pid].allocPoint,
            _allocPoint
        );

        totalAllocPoint = totalAllocPoint.sub(poolInfo[_pid].allocPoint).add(
            _allocPoint
        );
        poolInfo[_pid].allocPoint = _allocPoint;
    }

    // Function to harvest many pools in a single transaction
    function harvestMany(uint256[] calldata _pids) public {
        for (uint256 index = 0; index < _pids.length; ++index) {
            deposit(_pids[index], 0);
        }
    }

    // Update team address by the previous team address.
    function setmarketingAddress(address _marketingAddress) public {
        require(
            msg.sender == marketingAddress,
            "set team address: only previous team address can call this method"
        );
        marketingAddress = _marketingAddress;
        emit SetmarketingAddress(msg.sender, _marketingAddress);
    }

    function setmarketingPercent(uint256 _newmarketingPercent)
        public
        onlyOwner
    {
        require(
            0 <= _newmarketingPercent && _newmarketingPercent <= 100,
            "set team percent: invalid percent value"
        );
        require(
            _newmarketingPercent <= 100,
            "set team percent: total percent over max"
        );
        emit SetmarketingPercent(marketingPercent, _newmarketingPercent);
        marketingPercent = _newmarketingPercent;
    }
}