Cryo Explorer Ethereum Mainnet

// SPDX-License-Identifier: MIT

pragma solidity 0.8.19;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

interface Factory {
    function createPair(address tokenA, address tokenB) external returns (address pair);
}

contract OGzClub is ERC20, Ownable{
    uint256 public totalInitializated;
    uint256 private constant POOL_NUMBER = 7;
    uint256 private constant INITIALIZE_SUPPLY = 118_000_000_000 ether;
    uint256 public constant MAX_BUY_TAX_RATE = 800;
    uint256 public constant MAX_SELL_TAX_RATE = 800;
    uint256 public totalBuyTaxRate;
    uint256 public totalSellTaxRate;
    uint256 private toggleReferenceFees = 0;
    uint256 public togglePreferredNicknames;
    uint256 public referenceRate;
    uint256 public isTradeOpen;
    address public taxManager;
    address public constant WETH = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;
    address public immutable PairAddress;
    Factory public constant FACTORY = Factory(0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f);

    struct Pools {
        address poolAddress;
        uint256 taxRate;
    }

    struct Referrers {
        address referrer;
        uint256 timestamp;
    }

    struct Referrals {
        address referral;
        string nickname;
        uint256 timestamp;
        Referrers[] referees;
    }

    /// @dev mapping for all buying fee pools
    mapping(uint256 => Pools) public buyPools;
    mapping(uint256 => Pools) public sellPools;
    mapping(address => address) internal _referrals;
    mapping(address => string) internal _referralNickname;
    mapping(uint256 => uint256) internal _toggledOffBuyPools;
    mapping(uint256 => uint256) internal _toggledOffSellPools;
    mapping(string => address) internal _nickNames;
    /// @dev mapping for accounts that allow nicknames
    mapping(address => uint256) internal _preferredNicknames;
    /// @dev mapping for tax-frees accounts
    mapping(address => uint256) public _taxFrees;

    event RegisteredReferrence(address referral, string nickname, address referrer, uint256 timestamp);

    event CreatedLink(address owner, string nickName, uint256 timestamp);

    event BuyFeesUpdated(uint256 indexed poolId, uint256 newRate);

    event SellFeesUpdated(uint256 indexed poolId, uint256 newRate);

    event ReferenceFeeUpdated(uint256 oldRate, uint256 newFee);

    event ChangedPoolAddress(uint256 indexed poolId, address newAddress);

    event TransferWithTaxFee(string referralNickName, address referralAddress, address from, uint256 amount, uint256 referralEarnedAmount, uint256 timestamp);

    event ChangedTaxManager(address oldTaxManager, address newTaxManager);

    event TradingEnabled(uint256 timestamp);


    constructor(
        address _multisigOwner,
        address _taxManager,
        uint256 _referenceRate,
        Pools[] memory _poolsData)
    ERC20("OGzClub", "OGz") {
        require(_poolsData.length == POOL_NUMBER, "Pools datas length must be equal to 7");
        require(_multisigOwner != address(0) && _taxManager != address(0), "Owner and tax manager address cannot equal to address 0");
        require(_referenceRate > 0, "Reference tax rate must be greater than zero");
        referenceRate = _referenceRate;
        PairAddress = FACTORY.createPair(address(this), WETH);
        taxManager = _taxManager;
        _taxFrees[_multisigOwner] = 1;
        _transferOwnership(_multisigOwner);
        togglePreferredNicknames = 1;
        for (uint256 i = 0; i < _poolsData.length; i++) {
            require(_poolsData[i].poolAddress != address(0), "Pool address cannot equal to 0 address");
            require(_poolsData[i].taxRate > 0, "Pool rate must be greater than 0");
            buyPools[i] = _poolsData[i];
            sellPools[i] = _poolsData[i];
            totalBuyTaxRate += _poolsData[i].taxRate;
            totalSellTaxRate += _poolsData[i].taxRate;
        }
        require(
            totalBuyTaxRate == MAX_BUY_TAX_RATE &&
            totalSellTaxRate == MAX_SELL_TAX_RATE,
            "Total tax rate must be equal to maximum tax rate"
        );
        _mint(owner(), INITIALIZE_SUPPLY);
    }

    /** @dev Modifier to make a function callable only by the Tax Manager.
    * Throws if called by any account other than the Tax Manager.
    * @notice You must be the Tax Manager to call this.
    */
    modifier onlyTaxManager() {
        require(msg.sender == taxManager, "You are not tax manager.");
        _;
    }

    modifier initializationControl() {
        require(totalInitializated <= 62, "Initialization is done");
        _;
    }

    /**
    * @dev Modifier to restrict function access to preferred accounts for nickname creation.
    * @notice This modifier ensures that the function can only be accessed by preferred accounts,
    * or if the togglePreferredNicknames feature is turned off (equals to 0).
    */
    modifier onlyPreferredAccountCreateNickname() {
        require(
            togglePreferredNicknames == 0 ||
            _preferredNicknames[msg.sender] == 1,
            "You are not preferred");
        _;
    }

    /**
    * @dev Allows the current Tax Manager to relinquish control of the contract.
    * It sets the tax manager address to zero, hence no more tax related actions can be performed.
    * @notice Only the current Tax Manager can renounce tax management.
    */
    function renounceTaxManager() external onlyTaxManager {
        address oldTaxManager = taxManager;
        taxManager = address(0);
        emit ChangedTaxManager(oldTaxManager, taxManager);
    }

    /**
    * @dev Initializes referral data for the new token contract, pulling from the previously deployed token contract.
    * The referrals array provided should contain referral data from the previous contract to be transferred to the new one.
    * Emits a {CreatedLink} event for each referral that is successfully initialized.
    * Emits a {RegisteredReferrence} event for each referee that is successfully registered under a referrer.
    * @notice Only the contract owner can initialize the referral data.
    * @param referrals An array of Referral structs from the previous contract.
    * Each `Referral` struct should include the referrer's Ethereum address, nickname, and timestamp,
    * as well as an array of `Referee` structs, each of which should include the referred account's Ethereum address and timestamp.
    * @return true if the function succeeds.
    */
    function initializeReferralDatas(Referrals[] memory referrals) external onlyOwner initializationControl returns(bool) {
        require(referrals.length > 0, "Referrals array length must be greater than zero");
        totalInitializated += referrals.length;
        for (uint256 i = 0; i < referrals.length;) {
            _preferredNicknames[referrals[i].referral] = 1;
            require(bytes(_referralNickname[referrals[i].referral]).length == 0, "You already have a nickname");
            require(bytes(referrals[i].nickname).length != 0 && bytes(referrals[i].nickname).length <= 64, "Nickname must be between 1 and 64 characters");
            require(_nickNames[referrals[i].nickname] == address(0), "Nickname is already taken");
            _nickNames[referrals[i].nickname] = referrals[i].referral;
            _referralNickname[referrals[i].referral] = referrals[i].nickname;
            emit CreatedLink(referrals[i].referral, referrals[i].nickname, referrals[i].timestamp);
            if (referrals[i].referees.length > 0) {
                bytes32 referrerNicknameHash = keccak256(abi.encodePacked(_referralNickname[referrals[i].referral]));
                for (uint256 k = 0; k < referrals[i].referees.length;) {
                    require(
                        _referrals[referrals[i].referral] != referrals[i].referees[k].referrer &&
                        _referrals[referrals[i].referees[k].referrer] == address(0) &&
                        referrerNicknameHash != keccak256(abi.encodePacked("")) &&
                        referrals[i].referral != address(0) &&
                        referrals[i].referral != referrals[i].referees[k].referrer,
                        "Invalid referral"
                    );
                    _referrals[referrals[i].referees[k].referrer] = referrals[i].referral;
                    emit RegisteredReferrence(referrals[i].referral, referrals[i].nickname, referrals[i].referees[k].referrer, referrals[i].referees[k].timestamp);
                unchecked {
                    k ++;
                }
                }
            }
        unchecked {
            i ++;
        }
        }
        return true;
    }

    /**
    * @dev Transfers the tax management to a new address.
    * It sets the provided address as the new tax manager.
    * @notice Only the current Tax Manager can transfer tax management to a new address.
    * @param newTaxManager The address of the new Tax Manager.
    */
    function transferTaxManager(address newTaxManager) external onlyTaxManager {
        require(newTaxManager != address(0), "New address cannot be 0 address");
        address oldTaxManager = taxManager;
        taxManager = newTaxManager;
        emit ChangedTaxManager(oldTaxManager, taxManager);
    }


    /**
    * @dev Adds a list of addresses to the tax-free list.
    * These addresses will be exempt from taxes imposed by the contract.
    * @notice Only the current Tax Manager can add addresses to the tax-free list.
    * A maximum of 50 addresses can be added at a time.
    * @param taxFrees An array of addresses to be added to the tax-free list.
    * @return A boolean value indicating whether the operation was successful.
    */
    function addTaxFrees(address[] memory taxFrees) external onlyTaxManager returns(bool) {
        require(taxFrees.length <= 50, "Maximum 50 address can be added");
        for (uint256 i = 0; i < taxFrees.length;) {
            if (_taxFrees[taxFrees[i]] == 0 && taxFrees[i] != address(0)) {
                _taxFrees[taxFrees[i]] = 1;
            }
        unchecked {
            i++;
        }
        }
        return true;
    }

    /**
    * @dev Removes a list of addresses from the tax-free list.
    * These addresses will no longer be exempt from taxes imposed by the contract.
    * @notice Only the current Tax Manager can remove addresses from the tax-free list.
    * A maximum of 50 addresses can be removed at a time.
    * @param taxFrees An array of addresses to be removed from the tax-free list.
    * @return A boolean value indicating whether the operation was successful.
    */
    function removeTaxFrees(address[] memory taxFrees) external onlyTaxManager returns(bool) {
        require(taxFrees.length <= 50, "Maximum 50 address can be added");
        for (uint256 i = 0; i < taxFrees.length;) {
            if (_taxFrees[taxFrees[i]] == 1) {
                delete _taxFrees[taxFrees[i]];
            }
        unchecked {
            i++;
        }
        }
        return true;
    }

    /**
    * @dev Changes the address of a specific pool.
    * @notice This function can only be called by the current Tax Manager. It changes the
    * address of both the buy and sell pools at the specified pool ID.
    * @param poolId The ID of the pool whose address is to be changed.
    * @param newAddress The new address to set for the specified pool.
    */
    function changePoolAddress(
        uint256 poolId,
        address newAddress
    ) external onlyTaxManager {
        require(newAddress != address(0), "New address cannot equal to 0 address");
        require(poolId < POOL_NUMBER, "Pool id is not found.");
        buyPools[poolId].poolAddress = newAddress;
        sellPools[poolId].poolAddress = newAddress;
        emit ChangedPoolAddress(poolId, newAddress);
    }

    /**
    * @dev Function to add a list of preferred accounts for nickname creation.
    * @notice This function is used to add a list of accounts as preferred for creating nicknames.
    * The maximum limit is 50 accounts per transaction. Only contract owner can call this function.
    * @param account An array of account addresses to be marked as preferred.
    * @return Returns true if the operation is successful.
    */
    function addPreferredNicknames(address[] memory account) external onlyOwner returns(bool) {
        require(account.length <= 50, "Maximum 50 account can be added");
        for (uint256 i = 0; i < account.length; i++) {
            if (_preferredNicknames[account[i]] == 0 && account[i] != address(0)) {
                _preferredNicknames[account[i]] = 1;
            }
        }
        return true;
    }

    /**
    * @dev Function to remove a list of preferred accounts for nickname creation.
    * @notice This function is used to remove a list of accounts from the preferred accounts for creating nicknames.
    * The maximum limit is 50 accounts per transaction. Only contract owner can call this function.
    * @param account An array of account addresses to be removed from the list of preferred accounts.
    * @return Returns true if the operation is successful.
    */
    function removePreferredNicknames(address[] memory account) external onlyOwner returns(bool) {
        require(account.length <= 50, "Maximum 50 account can be removed");
        for (uint256 i = 0; i < account.length; i++) {
            if (_preferredNicknames[account[i]] == 1) {
                delete _preferredNicknames[account[i]];
            }
        }
        return true;
    }

    /**
    * @dev Function to disable the preferred nickname creation feature.
    * @notice This function allows the contract owner to disable the preferred nickname creation feature.
    * Once this function is called, only the contract owner will be able to re-enable it.
    * @return Returns true if the operation is successful.
    */
    function toggleOffPreferredNicknames() external onlyOwner returns(bool) {
        togglePreferredNicknames = 0;
        return true;
    }

    /**
    * @dev Function to check whether a specific account has the permission to create a nickname.
    * @notice This function checks whether the passed account has the permission to create a nickname.
    * If the preferred nickname feature is turned off (togglePreferredNicknames == 0), this function will return true for any account.
    * If the preferred nickname feature is turned on (togglePreferredNicknames != 0), only accounts in the preferred nicknames list (_preferredNicknames[account] == 1) will return true.
    * @param account The address of the account to check for the create nickname permission.
    * @return Returns true if the account has the permission to create a nickname.
    */
    function checkCreateNicknamePermission(address account) external view returns(bool) {
        return togglePreferredNicknames == 0 || _preferredNicknames[account] == 1;
    }


    /**
    * @dev Function to disable the buy tax fee for a specific pool.
    * @notice This function will disable the buy tax fee for a specific pool by setting the corresponding _toggledOffBuyPools value to 1.
    * If the pool is already toggled off, the function will revert. After disabling, the total buy tax rate will be updated and the pool will be deleted.
    * @param poolId The id of the pool to disable the buy tax fee.
    * @return Returns true if the operation is successful.
    */
    /*
    PoolIds:
    0: Future Plan
    1: Team1
    2: Team2
    3: Team3
    4: Liquidity Pool
    5: Staking
    6: Future Plan or Referral
    */
    function toggleOffBuyTaxFee(uint256 poolId) external onlyTaxManager returns(bool){
        require(poolId <= POOL_NUMBER, "Pool id not found");
        require(_toggledOffBuyPools[poolId] == 0, "The pool is already toggled off");
        _toggledOffBuyPools[poolId] = 1;
        totalBuyTaxRate = totalBuyTaxRate - buyPools[poolId].taxRate;
        delete buyPools[poolId];
        emit BuyFeesUpdated(poolId, 0);
        return true;
    }

    /**
    * @dev Function to disable the sell tax fee for a specific pool.
    * @notice This function will disable the sell tax fee for a specific pool by setting the corresponding _toggledOffSellPools value to 1.
    * If the pool is already toggled off, the function will revert. After disabling, the total sell tax rate will be updated and the pool will be deleted.
    * @param poolId The id of the pool to disable the sell tax fee.
    * @return Returns true if the operation is successful.
    */
    function toggleOffSellTaxFee(uint256 poolId) external onlyTaxManager returns(bool){
        require(poolId <= POOL_NUMBER, "Pool id not found");
        require(_toggledOffSellPools[poolId] == 0, "The pool is already toggled off");
        _toggledOffSellPools[poolId] = 1;
        totalSellTaxRate = totalSellTaxRate - sellPools[poolId].taxRate;
        delete sellPools[poolId];
        emit SellFeesUpdated(poolId, 0);
        return true;
    }

    /**
    * @dev Function to disable the reference fee.
    * @notice This function will disable the reference fee by setting the toggleReferenceFees value to 1. If the reference fee is already toggled off, the function will revert.
    * After disabling, the reference rate will be updated to 0.
    * @return Returns true if the operation is successful.
    */
    function toggleOffReferenceFee() external onlyTaxManager returns(bool) {
        require(toggleReferenceFees == 0, "Reference pool is already toggled off");
        toggleReferenceFees = 1;
        uint256 oldRate = referenceRate;
        referenceRate = 0;
        emit ReferenceFeeUpdated(oldRate, 0);
        return true;
    }

    /**
    * @dev Function to decrease the buy tax fee of a specific pool.
    * @notice This function allows the tax manager to reduce the buy tax fee for a given pool. The new fee should be greater than 0 and less than the current tax fee, otherwise, the function will revert. This function will not work if the pool is toggled off.
    * @param poolId The identifier of the pool that the tax fee will be decreased for.
    * @param newFee The new fee that will replace the old tax fee for the given pool.
    * @return Returns true if the operation is successful.
    */
    function decreaseBuyTaxFee(
        uint256 poolId,
        uint256 newFee
    ) external onlyTaxManager returns(bool){
        require(poolId <= POOL_NUMBER, "Pool id not found");
        require(_toggledOffBuyPools[poolId] == 0, "The pool is already toggled off");
        require(
            newFee > 0 &&
            newFee < buyPools[poolId].taxRate,
            "New fee rate must be between 0 and current tax fee"
        );
        totalBuyTaxRate = totalBuyTaxRate - (buyPools[poolId].taxRate - newFee);
        buyPools[poolId].taxRate = newFee;
        emit BuyFeesUpdated(poolId, newFee);
        return true;
    }

    /**
    * @dev Function to decrease the sell tax fee of a specific pool.
    * @notice This function allows the tax manager to reduce the sell tax fee for a given pool. The new fee should be greater than 0 and less than the current tax fee, otherwise, the function will revert. This function will not work if the pool is toggled off.
    * @param poolId The identifier of the pool that the tax fee will be decreased for.
    * @param newFee The new fee that will replace the old tax fee for the given pool.
    * @return Returns true if the operation is successful.
    */
    function decreaseSellTaxFee(
        uint256 poolId,
        uint256 newFee
    ) external onlyTaxManager returns(bool){
        require(poolId <= POOL_NUMBER, "Pool id not found");
        require(_toggledOffSellPools[poolId] == 0, "The pool is already toggled off");
        require(
            newFee > 0 &&
            newFee < sellPools[poolId].taxRate,
            "New fee rate must be between 0 and current tax fee"
        );
        totalSellTaxRate = totalSellTaxRate - (sellPools[poolId].taxRate - newFee);
        sellPools[poolId].taxRate = newFee;
        emit SellFeesUpdated(poolId, newFee);
        return true;
    }

    /**
    * @dev Function to decrease the reference fee.
    * @notice This function allows the tax manager to reduce the reference fee. The new fee should be greater than 0 and less than the current fee, otherwise, the function will revert.
    * @param newFee The new fee that will replace the old reference fee.
    * @return Returns true if the operation is successful.
    */
    function decreaseReferenceFee(uint256 newFee) external onlyTaxManager returns(bool) {
        require(
            newFee > 0 &&
            newFee < referenceRate,
            "New fee rate must be between 0 and current fee"
        );
        uint256 oldRate = referenceRate;
        referenceRate = newFee;
        emit ReferenceFeeUpdated(oldRate, newFee);
        return true;
    }

    /**
    * @dev Calculates the fee amount for a given transaction amount and fee rate.
    * @notice This is a private function used to calculate the fee amount based on a specific transaction amount and a fee rate.
    * The fee rate is a percentage value multiplied by 100 to handle it as an integer.
    * Therefore, it needs to be divided by 10,000 during calculation to reflect the correct fee amount.
    * @param amount The transaction amount for which the fee should be computed.
    * @param fee The fee rate used for the computation. The fee is represented as a percentage out of 10,000 (equivalent to a basis point representation).
    * @return Returns the calculated fee amount.
    */
    function computeFee(uint256 amount, uint256 fee) private pure returns(uint256) {
        return amount * fee / 10000;
    }

    /**
    * @notice Enables trading. This function can only be called by the contract owner.
    * @dev Checks whether trading is already enabled. If not, it enables trading and triggers the TradingEnabled event.
    * @return Returns a boolean value. If the operation is successful, it returns true; otherwise, false.
    */
    function enableTrading() external onlyOwner returns(bool) {
        require(isTradeOpen == 0, "Trade is already enabled");
        isTradeOpen = 1;
        emit TradingEnabled(block.timestamp);
        return true;
    }

    /**
    * @notice This private function is used to send buy fees to different pools and referral addresses.
    * @dev It calculates and transfers fees for each buy pool unless the pool is toggled off.
    * It also computes and transfers the reference fee if reference fees are toggled on and there exists a referral for the owner.
    * If there's no referral or reference fees are toggled off, it computes and sends the fee to the last pool if it is not toggled off.
    * The function subtracts the total fee from the amount and returns the difference.
    * @param owner The address of the owner initiating the buy action.
    * @param from The address of the pair.
    * @param amount The amount of tokens being purchased.
    * @return Returns the amount after subtracting the total fee.
    */
    function sendBuyFees(
        address owner,
        address from,
        uint256 amount
    ) private returns(uint256) {
        uint256 totalFee = 0;
        for (uint256 i = 0; i < POOL_NUMBER - 1; i++) {
            uint256 poolTaxRate = buyPools[i].taxRate;
            if (_toggledOffBuyPools[i] == 0) {
                uint256 fee = computeFee(amount, poolTaxRate);
                totalFee += fee;
                address poolAddress = buyPools[i].poolAddress;
                _transfer(from, poolAddress, fee);
            }
        }
        address referral = _referrals[owner];
        if (toggleReferenceFees == 0 && referral != address(0)) {
            uint256 referenceFee = computeFee(amount, referenceRate);
            totalFee += referenceFee;
            _transfer(from, referral, referenceFee);
            emit TransferWithTaxFee(_referralNickname[referral], referral, owner, amount, referenceFee, block.timestamp);
        } else if (_toggledOffBuyPools[POOL_NUMBER - 1] == 0){
            uint256 lastPoolFee = computeFee(amount, buyPools[POOL_NUMBER - 1].taxRate);
            totalFee += lastPoolFee;
            address lastPoolAddress = buyPools[POOL_NUMBER - 1].poolAddress;
            _transfer(from, lastPoolAddress, lastPoolFee);
        }
        return amount - totalFee;
    }

    /**
    * @notice This private function is used to send sell fees to different pools and referral addresses.
    * @dev It calculates and transfers fees for each sell pool unless the pool is toggled off.
    * It also computes and transfers the reference fee if reference fees are toggled on and there exists a referral for the owner.
    * If there's no referral or reference fees are toggled off, it computes and sends the fee to the last pool if it is not toggled off.
    * The function subtracts the total fee from the amount and returns the difference.
    * @param owner The address of the owner initiating the sell action.
    * @param amount The amount of tokens being sold.
    * @return Returns the amount after subtracting the total fee.
    */
    function sendSellFees(address owner, uint256 amount) private returns(uint256) {
        uint256 totalFee = 0;
        for (uint256 i = 0; i < POOL_NUMBER - 1; i++) {
            uint256 poolTaxRate = sellPools[i].taxRate;
            if (_toggledOffSellPools[i] == 0) {
                uint256 fee = computeFee(amount, poolTaxRate);
                totalFee += fee;
                address poolAddress = sellPools[i].poolAddress;
                _transfer(owner, poolAddress, fee);
            }
        }
        address referral = _referrals[owner];
        if (toggleReferenceFees == 0 && referral != address(0)) {
            uint256 referenceFee = computeFee(amount, referenceRate);
            totalFee += referenceFee;
            _transfer(owner, referral, referenceFee);
            emit TransferWithTaxFee(_referralNickname[referral], referral, owner, amount, referenceFee, block.timestamp);
        } else if(_toggledOffSellPools[POOL_NUMBER - 1] == 0){
            uint256 lastPoolFee = computeFee(amount, sellPools[POOL_NUMBER - 1].taxRate);
            totalFee += lastPoolFee;
            address lastPoolAddress = sellPools[POOL_NUMBER - 1].poolAddress;
            _transfer(owner, lastPoolAddress, lastPoolFee);
        }
        return amount - totalFee;
    }


    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) public virtual override returns (bool) {
        address spender = _msgSender();
        _spendAllowance(from, spender, amount);
        if (to == PairAddress && _taxFrees[from] == 0) {
            require(isTradeOpen == 1, "Trading is not open");
            amount = sendSellFees(from, amount);
        }
        _transfer(from, to, amount);
        return true;
    }

    function transfer(address to, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        if (owner == PairAddress && _taxFrees[to] == 0) {
            require(isTradeOpen == 1, "Trading is not open");
            amount = sendBuyFees(to, owner, amount);
        }
        _transfer(owner, to, amount);
        return true;
    }

    /**
    * @notice This function allows eligible accounts to create a nickname.
    * @dev Function is restricted to accounts that satisfy the 'onlyPreferredAccountCreateNickname' modifier.
    * A nickname should be unique, not empty, and at most 64 characters long.
    * Emits a 'CreatedLink' event upon successful execution.
    * @param nickName The chosen nickname string.
    * @return Returns 'true' upon successful execution.
    */
    function createNickname(string memory nickName) external onlyPreferredAccountCreateNickname returns(bool) {
        require(bytes(_referralNickname[msg.sender]).length == 0, "You already have a nickname");
        require(bytes(nickName).length != 0 && bytes(nickName).length <= 64, "Nickname must be between 1 and 64 characters");
        require(_nickNames[nickName] == address(0), "Nickname is already taken");
        _nickNames[nickName] = msg.sender;
        _referralNickname[msg.sender] = nickName;
        emit CreatedLink(msg.sender, nickName, block.timestamp);
        return true;
    }

    /**
    * @notice This function returns the nickname of a given account.
    * @param account The address of the account for which the nickname is queried.
    * @return Returns the nickname string associated with the given account.
    */
    function getNickname(address account) external view returns(string memory) {
        return _referralNickname[account];
    }

    /**
    * @notice This function returns the referrer information for a given referee.
    * @param referee The address of the referee for which the referrer information is queried.
    * @return Returns a tuple containing the nickname string and address of the referrer.
    */
    function getReferrer(address referee) external view returns(string memory, address) {
        address referrer = _referrals[referee];
        return (_referralNickname[referrer], referrer);
    }

    /**
    * @notice This function returns the address associated with a given nickname.
    * @param nickname The nickname for which the associated address is queried.
    * @return Returns the address associated with the given nickname.
    */
    function getAddressWithNickname(string memory nickname) external view returns(address) {
        return _nickNames[nickname];
    }

    /**
    * @notice This function allows a user to add a referral using a nickname.
    * @param nickname The nickname of the referrer.
    * @return Returns true if the referral was successfully added.
    */
    function addReferral(string memory nickname) external returns(bool) {
        address referrer = _nickNames[nickname];
        bytes32 referrerNicknameHash = keccak256(abi.encodePacked(_referralNickname[referrer]));
        require(
            _referrals[referrer] != msg.sender &&
            _referrals[msg.sender] == address(0) &&
            referrerNicknameHash != keccak256(abi.encodePacked("")) &&
            referrer != address(0) &&
            referrer != msg.sender,
            "Invalid referral"
        );
        _referrals[msg.sender] = referrer;
        emit RegisteredReferrence(referrer, nickname, msg.sender, block.timestamp);
        return true;
    }
}

// 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;
    }
}

// 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);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

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

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

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

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

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

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

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

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

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

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

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

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

    /**
     * @dev See {IERC20-approve}.
     *
     * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
     * `transferFrom`. This is semantically equivalent to an infinite approval.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * NOTE: Does not update the allowance if the current allowance
     * is the maximum `uint256`.
     *
     * Requirements:
     *
     * - `from` and `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     * - the caller must have allowance for ``from``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) public virtual override returns (bool) {
        address spender = _msgSender();
        _spendAllowance(from, spender, amount);
        _transfer(from, to, amount);
        return true;
    }

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

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

        return true;
    }

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

        _beforeTokenTransfer(from, to, amount);

        uint256 fromBalance = _balances[from];
        require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[from] = fromBalance - amount;
            // Overflow not possible: the sum of all balances is capped by totalSupply, and the sum is preserved by
            // decrementing then incrementing.
            _balances[to] += amount;
        }

        emit Transfer(from, to, amount);

        _afterTokenTransfer(from, to, amount);
    }

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

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

        _totalSupply += amount;
        unchecked {
            // Overflow not possible: balance + amount is at most totalSupply + amount, which is checked above.
            _balances[account] += amount;
        }
        emit Transfer(address(0), account, amount);

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

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

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

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
            // Overflow not possible: amount <= accountBalance <= totalSupply.
            _totalSupply -= amount;
        }

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

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

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

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

    /**
     * @dev Updates `owner` s allowance for `spender` based on spent `amount`.
     *
     * Does not update the allowance amount in case of infinite allowance.
     * Revert if not enough allowance is available.
     *
     * Might emit an {Approval} event.
     */
    function _spendAllowance(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        uint256 currentAllowance = allowance(owner, spender);
        if (currentAllowance != type(uint256).max) {
            require(currentAllowance >= amount, "ERC20: insufficient allowance");
            unchecked {
                _approve(owner, spender, currentAllowance - amount);
            }
        }
    }

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

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

// 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);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";

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

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

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