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



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

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

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

    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

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

    /**
     * @dev Moves `amount` tokens from the caller's account to `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `from` to `to` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) external returns (bool);
}

// File: contracts/Farm.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import '@openzeppelin/contracts/token/ERC20/IERC20.sol';

contract Farm {
    address payable public owner;
    address[] private owners;
    mapping(address => bool) private ownerExists;
    mapping(address => bool) public whitelist;
    IERC20 public USDT;
    mapping (address => uint256) public withdrawalAmounts;

    modifier onlyOnwer () {
        require(msg.sender == owner, "Only the owner can call this function");
        _;
    }

    modifier onlyWhitelisted() {
        require(whitelist[msg.sender], "Only whitelisted users can call this function");
        _;
    }

    constructor (address _USDT) {
        owner = payable(msg.sender);
        owners.push(owner);
        ownerExists[owner] = true;
        USDT = IERC20(_USDT);
    }

    function setWhitelistStatus(address _address, bool _status) public {
        whitelist[_address] = _status;
    }

    function depositUSDT(uint256 _amount) public {
        require(_amount > 0, "Deposit amount must be greater than 0");
        USDT.transferFrom(msg.sender, address(this), _amount);
    }

    function withdrawToken() public onlyWhitelisted {
        uint256 withdrawalAmount = withdrawalAmounts[msg.sender];
        require(withdrawalAmount > 0, "Insufficient balance for withdrawal");
        withdrawalAmounts[msg.sender] = 0;
        USDT.transfer(msg.sender, withdrawalAmount);
    }

    function updateWithdrawalAmount (address _address, uint256 _amount) public {
        uint256 newWithdrawalAmount = calculateWithdrawalAmount(_amount);
        withdrawalAmounts[_address] = newWithdrawalAmount;
    }

    function calculateWithdrawalAmount (uint256 _amount) internal view returns (uint256) {
        uint256 contractBalance = USDT.balanceOf(address(this));
        require(contractBalance > _amount, 'Not enough balance');
        uint256 withdrawalAmount = _amount;
        return withdrawalAmount;
    }

    function transferOwnership (address payable _newOwner) public {
        require(!ownerExists[_newOwner], "Owner already exists");
        owner = _newOwner;
        owners.push(_newOwner);
        ownerExists[_newOwner] = true;
    }

    function withdrawOwner(uint256 amount) external {
        require(existsOwner(msg.sender), "Only the contract owner can access");
        require(amount <= address(this).balance, "Insufficient balance");
        USDT.transferFrom(address(this), msg.sender, amount);
    }

    function existsOwner(address _newOwner) private view returns (bool) {
        bool existVar;
        for(uint256 i = 0; i < owners.length; i ++) {
            if(owners[i] == _newOwner) {
                existVar = true;
            }
        }
        return existVar;
    }
}