Good morning OZ community!
I believe I have a working version of the ERC20 I want to use for a DAO I am forming, but would love some feedback on things I could improve upon.
In general, it's a fairly basic ERC20 with the option for auto-burn and auto-liquidity tax. I was trying to get those functions operating correctly before adding the Snapshot feature and possibly Votes feature down the line as this will be used as the Governance token as well as a Utility token.
Below is the code, let me know what you think:
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "@openzeppelin/contracts-upgradeable/token/ERC20/IERC20Upgradeable.sol";
import "@openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
import "@openzeppelin/contracts-upgradeable/proxy/utils/UUPSUpgradeable.sol";
// QuickSwap Interfaces
interface IUniswapV2Factory {
event PairCreated(address indexed token0, address indexed token1, address pair, uint);
function getPair(address tokenA, address tokenB) external view returns (address pair);
function allPairs(uint) external view returns (address pair);
function allPairsLength() external view returns (uint);
function feeTo() external view returns (address);
function feeToSetter() external view returns (address);
function createPair(address tokenA, address tokenB) external returns (address pair);
}
interface IUniswapV2Pair {
event Approval(address indexed owner, address indexed spender, uint value);
event Transfer(address indexed from, address indexed to, uint value);
function name() external pure returns (string memory);
function symbol() external pure returns (string memory);
function decimals() external pure returns (uint8);
function totalSupply() external view returns (uint);
function balanceOf(address owner) external view returns (uint);
function allowance(address owner, address spender) external view returns (uint);
function approve(address spender, uint value) external returns (bool);
function transfer(address to, uint value) external returns (bool);
function transferFrom(address from, address to, uint value) external returns (bool);
function DOMAIN_SEPARATOR() external view returns (bytes32);
function PERMIT_TYPEHASH() external pure returns (bytes32);
function nonces(address owner) external view returns (uint);
function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external;
event Mint(address indexed sender, uint amount0, uint amount1);
event Burn(address indexed sender, uint amount0, uint amount1, address indexed to);
event Swap(
address indexed sender,
uint amount0In,
uint amount1In,
uint amount0Out,
uint amount1Out,
address indexed to
);
event Sync(uint112 reserve0, uint112 reserve1);
function MINIMUM_LIQUIDITY() external pure returns (uint);
function factory() external view returns (address);
function token0() external view returns (address);
function token1() external view returns (address);
function getReserves() external view returns (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast);
function price0CumulativeLast() external view returns (uint);
function price1CumulativeLast() external view returns (uint);
function kLast() external view returns (uint);
function mint(address to) external returns (uint liquidity);
function burn(address to) external returns (uint amount0, uint amount1);
function swap(uint amount0Out, uint amount1Out, address to, bytes calldata data) external;
function skim(address to) external;
function sync() external;
}
interface IUniswapV2Router01 {
function factory() external pure returns (address);
function WETH() external pure returns (address);
function addLiquidity(
address tokenA,
address tokenB,
uint amountADesired,
uint amountBDesired,
uint amountAMin,
uint amountBMin,
address to,
uint deadline
) external returns (uint amountA, uint amountB, uint liquidity);
function addLiquidityETH(
address token,
uint amountTokenDesired,
uint amountTokenMin,
uint amountETHMin,
address to,
uint deadline
) external payable returns (uint amountToken, uint amountETH, uint liquidity);
function removeLiquidity(
address tokenA,
address tokenB,
uint liquidity,
uint amountAMin,
uint amountBMin,
address to,
uint deadline
) external returns (uint amountA, uint amountB);
function removeLiquidityETH(
address token,
uint liquidity,
uint amountTokenMin,
uint amountETHMin,
address to,
uint deadline
) external returns (uint amountToken, uint amountETH);
function removeLiquidityWithPermit(
address tokenA,
address tokenB,
uint liquidity,
uint amountAMin,
uint amountBMin,
address to,
uint deadline,
bool approveMax, uint8 v, bytes32 r, bytes32 s
) external returns (uint amountA, uint amountB);
function removeLiquidityETHWithPermit(
address token,
uint liquidity,
uint amountTokenMin,
uint amountETHMin,
address to,
uint deadline,
bool approveMax, uint8 v, bytes32 r, bytes32 s
) external returns (uint amountToken, uint amountETH);
function swapExactTokensForTokens(
uint amountIn,
uint amountOutMin,
address[] calldata path,
address to,
uint deadline
) external returns (uint[] memory amounts);
function swapTokensForExactTokens(
uint amountOut,
uint amountInMax,
address[] calldata path,
address to,
uint deadline
) external returns (uint[] memory amounts);
function swapExactETHForTokens(uint amountOutMin, address[] calldata path, address to, uint deadline)
external
payable
returns (uint[] memory amounts);
function swapTokensForExactETH(uint amountOut, uint amountInMax, address[] calldata path, address to, uint deadline)
external
returns (uint[] memory amounts);
function swapExactTokensForETH(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline)
external
returns (uint[] memory amounts);
function swapETHForExactTokens(uint amountOut, address[] calldata path, address to, uint deadline)
external
payable
returns (uint[] memory amounts);
function quote(uint amountA, uint reserveA, uint reserveB) external pure returns (uint amountB);
function getAmountOut(uint amountIn, uint reserveIn, uint reserveOut) external pure returns (uint amountOut);
function getAmountIn(uint amountOut, uint reserveIn, uint reserveOut) external pure returns (uint amountIn);
function getAmountsOut(uint amountIn, address[] calldata path) external view returns (uint[] memory amounts);
function getAmountsIn(uint amountOut, address[] calldata path) external view returns (uint[] memory amounts);
}
interface IUniswapV2Router02 is IUniswapV2Router01 {
function removeLiquidityETHSupportingFeeOnTransferTokens(
address token,
uint liquidity,
uint amountTokenMin,
uint amountETHMin,
address to,
uint deadline
) external returns (uint amountETH);
function removeLiquidityETHWithPermitSupportingFeeOnTransferTokens(
address token,
uint liquidity,
uint amountTokenMin,
uint amountETHMin,
address to,
uint deadline,
bool approveMax, uint8 v, bytes32 r, bytes32 s
) external returns (uint amountETH);
function swapExactTokensForTokensSupportingFeeOnTransferTokens(
uint amountIn,
uint amountOutMin,
address[] calldata path,
address to,
uint deadline
) external;
function swapExactETHForTokensSupportingFeeOnTransferTokens(
uint amountOutMin,
address[] calldata path,
address to,
uint deadline
) external payable;
function swapExactTokensForETHSupportingFeeOnTransferTokens(
uint amountIn,
uint amountOutMin,
address[] calldata path,
address to,
uint deadline
) external;
}
// Custom Contract
contract MyToken is Initializable, IERC20Upgradeable, OwnableUpgradeable, UUPSUpgradeable {
mapping(address => uint256) private _balances;
mapping(address => mapping(address => uint256)) private _allowances;
mapping(address => bool) private _isExcluded;
address[] private _excluded;
// Contract Variables
uint256 private _totalSupply;
string private _name;
string private _symbol;
// Burn Variables
uint256 public _burnFee = 5; // 0.5% Burned
bool public burnEnabled;
address private burnWallet = 0x000000000000000000000000000000000000dEaD;
// Liquidity Variables
uint256 public _liquidityFee = 5; // 0.5% Burned
bool public liquifyEnabled;
// QuickSwap Variables
IUniswapV2Router02 public immutable uniswapV2Router;
address public immutable uniswapV2Pair;
constructor() {
_disableInitializers();
_isExcluded[owner()] = true;
_isExcluded[address(this)] = true;
IUniswapV2Router02 _uniswapV2Router = IUniswapV2Router02(0xa5E0829CaCEd8fFDD4De3c43696c57F7D7A678ff);
uniswapV2Pair = IUniswapV2Factory(_uniswapV2Router.factory())
.createPair(address(this), _uniswapV2Router.WETH());
uniswapV2Router = _uniswapV2Router;
}
function initialize() initializer public {
__ERC20_init("MyToken", "MTK");
__Ownable_init();
__UUPSUpgradeable_init();
_mint(msg.sender, 10000 * 10 ** decimals());
}
function _authorizeUpgrade(address newImplementation)
internal
onlyOwner
override
{}
function __ERC20_init(string memory name_, string memory symbol_) internal onlyInitializing {
__ERC20_init_unchained(name_, symbol_);
}
function __ERC20_init_unchained(string memory name_, string memory symbol_) internal onlyInitializing {
_name = name_;
_symbol = symbol_;
}
receive() external payable virtual {}
// QuickSwap Events
bool inSwapAndLiquify;
event SwapAndLiquify(
uint256 tokensSwapped,
uint256 ethReceived,
uint256 tokensIntoLiqudity
);
modifier lockTheSwap {
inSwapAndLiquify = true;
_;
inSwapAndLiquify = false;
}
// ERC20 Functions
function name() public view virtual returns (string memory) {
return _name;
}
function symbol() public view virtual returns (string memory) {
return _symbol;
}
function decimals() public view virtual returns (uint8) {
return 18;
}
function totalSupply() public view virtual override returns (uint256) {
return _totalSupply;
}
function balanceOf(address account) public view virtual override returns (uint256) {
return _balances[account];
}
function transfer(address to, uint256 amount) public virtual override returns (bool) {
address owner = _msgSender();
_transfer(owner, to, amount);
return true;
}
function allowance(address owner, address spender) public view virtual override returns (uint256) {
return _allowances[owner][spender];
}
function approve(address spender, uint256 amount) public virtual override returns (bool) {
address owner = _msgSender();
_approve(owner, spender, amount);
return true;
}
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;
}
function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
address owner = _msgSender();
_approve(owner, spender, allowance(owner, spender) + addedValue);
return true;
}
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;
}
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);
}
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.
}
emit Transfer(account, address(0), amount);
_afterTokenTransfer(account, address(0), amount);
}
function _approve(address owner, address spender, uint256 amount) private {
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);
}
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);
}
}
}
function _beforeTokenTransfer(
address from,
address to,
uint256 amount
) internal virtual {}
function _afterTokenTransfer(
address from,
address to,
uint256 amount
) internal virtual {}
// Custom Functions
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");
require(amount > 0, "Transfer amount must be greater than zero");
uint256 contractTokenBalance = _balances[address(this)];
//Calculate the Fees
uint256 burnFee = amount * _burnFee / 1000;
uint256 liquidityFee = amount * _liquidityFee / 1000;
uint256 totalFee = amount + burnFee + liquidityFee;
// Send Previous Liquidity
if (!inSwapAndLiquify && from != uniswapV2Pair && liquifyEnabled){
swapAndLiquify(contractTokenBalance);
}
_beforeTokenTransfer(from, to, amount);
bool takeFee = true;
if(_isExcluded[from] || _isExcluded[to]){
takeFee = false;
}
if (takeFee && burnEnabled && liquifyEnabled){
require(_balances[from] >= amount + totalFee, "ERC20: transfer amount exceeds balance");
// Subtract the fee and the original amount from the sender's balance
_balances[from] -= amount + totalFee;
// Add the original amount to the recipient's balance
_balances[to] += amount;
// Add Fees to Contract Balance
contractTokenBalance += totalFee;
// Transfer Burn Fee to DumpsterFire
_balances[burnWallet] += burnFee;
} else if (takeFee && burnEnabled && !liquifyEnabled){
require(_balances[from] >= amount + burnFee, "ERC20: transfer amount exceeds balance");
// Subtract the fee and the original amount from the sender's balance
_balances[from] -= amount + burnFee;
// Add the original amount to the recipient's balance
_balances[to] += amount;
// Add Fees to Contract Balance
contractTokenBalance += burnFee;
// Transfer Burn Fee to DumpsterFire
_balances[burnWallet] += burnFee;
} else if (takeFee && !burnEnabled && liquifyEnabled){
require(_balances[from] >= amount + liquidityFee, "ERC20: transfer amount exceeds balance");
// Subtract the fee and the original amount from the sender's balance
_balances[from] -= amount + liquidityFee;
// Add the original amount to the recipient's balance
_balances[to] += amount;
// Add Fees to Contract Balance
contractTokenBalance += liquidityFee;
} else {
require(_balances[from] >= amount, "ERC20: transfer amount exceeds balance");
_balances[from] -= amount;
_balances[to] += amount;
}
emit Transfer(from, to, amount);
_afterTokenTransfer(from, to, amount);
}
// Auto-Liquidity Back-End
function swapAndLiquify(uint256 contractTokenBalance) private lockTheSwap {
uint256 half = contractTokenBalance / 2;
uint256 otherHalf = contractTokenBalance - half;
uint256 initialBalance = address(this).balance;
swapTokensForEth(half);
uint256 newBalance = address(this).balance - initialBalance;
addLiquidity(otherHalf, newBalance);
emit SwapAndLiquify(half, newBalance, otherHalf);
}
function swapTokensForEth(uint256 tokenAmount) private {
address[] memory path = new address[](2);
path[0] = address(this);
path[1] = uniswapV2Router.WETH();
_approve(address(this), address(uniswapV2Router), tokenAmount);
uniswapV2Router.swapExactTokensForETHSupportingFeeOnTransferTokens(
tokenAmount,
0,
path,
address(this),
block.timestamp
);
}
function addLiquidity(uint256 tokenAmount, uint256 ethAmount) private {
_approve(address(this), address(uniswapV2Router), tokenAmount);
uniswapV2Router.addLiquidityETH{value: ethAmount}(
address(this),
tokenAmount,
0,
0,
owner(),
block.timestamp
);
}
// External Control Functions
function excludeFromFee(address account) external onlyOwner {
require(!_isExcluded[account], "Account is already excluded");
_isExcluded[account] = true;
_excluded.push(account);
}
function includeInFee(address account) external onlyOwner() {
require(_isExcluded[account] == false, "Account is already included");
for (uint256 i = 0; i < _excluded.length; i++) {
if (_excluded[i] == account) {
_excluded[i] = _excluded[_excluded.length - 1];
_isExcluded[account] = false;
}
}
}
function enableBurn() public onlyOwner {
burnEnabled = true;
}
function disableBurn() public onlyOwner {
burnEnabled = false;
}
function enableLiquify() public onlyOwner {
liquifyEnabled = true;
}
function disableLiquify() public onlyOwner {
liquifyEnabled = false;
}
function setBurnFee(uint256 BurnFee) external onlyOwner() {
_burnFee = BurnFee;
}
function setLiquidityFee(uint256 liquidityFee) external onlyOwner() {
_liquidityFee = liquidityFee;
}
function getBalance() public view onlyOwner() returns(uint) {
return _balances[address(this)];
}
function withdraw() public onlyOwner() {
address payable to = payable(owner());
to.transfer(getBalance());
}
/**
* @dev This empty reserved space is put in place to allow future versions to add new
* variables without shifting down storage in the inheritance chain.
* See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
*/
uint256[45] private __gap;
}
