Balancer is a Project that has caught my attention because is innovating in the Defi space. Balancer allows investors getting passive income while keeping a portfolio that suits them, traders can do swaps with low gas fees and protected against MEV, bots have good arbitrage opportunities among other things. All of this while offering a modern UI and Smart contracts.
In this video we will launch a token that charges transaction fees for each swap on the Balancer pools.
Before we start
For this tutorial you will need Metamask or another compatible wallet with Goerli funds that you can get from a faucet.
Smart contracts with transactions fees in Balancer
// SPDX-License-Identifier: MIT
pragma solidity 0.8.17;
abstract contract Context {
function _msgSender() internal view virtual returns (address) {
return msg.sender;
}
function _msgData() internal view virtual returns (bytes calldata) {
return msg.data;
}
}
interface IERC20 {
function totalSupply() external view returns (uint256);
function balanceOf(address account) external view returns (uint256);
function transfer(address to, uint256 amount) external returns (bool);
function allowance(address owner, address spender) external view returns (uint256);
function approve(address spender, uint256 amount) external returns (bool);
function transferFrom(
address from,
address to,
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);
}
interface IERC20Metadata is IERC20 {
function name() external view returns (string memory);
function symbol() external view returns (string memory);
function decimals() external view returns (uint8);
}
contract BalancerToken is Context, IERC20, IERC20Metadata {
// Openzeppelin variables
mapping(address => uint256) private _balances;
mapping(address => mapping(address => uint256)) private _allowances;
uint256 private _totalSupply;
string private _name;
string private _symbol;
// My variables
address public balancerVault = 0xBA12222222228d8Ba445958a75a0704d566BF2C8;
address public feeWallet;
uint public _feeDecimal = 2;
// index 0 = buy fee, index 1 = sell fee, index 2 = p2p fee
uint[] public fees;
mapping(address => bool) public isTaxless;
// Openzeppelin functions
constructor() {
_name = "My Balancer Token";
_symbol = "BT";
feeWallet = 0x0000000000000000000000000000000000000000;
fees.push(100); // 1% buy fee
fees.push(200); // 2% sell fee
fees.push(0); // 0% p2p fee
isTaxless[msg.sender] = true;
isTaxless[address(this)] = true;
isTaxless[feeWallet] = true;
isTaxless[address(0)] = true;
_mint(msg.sender, 1_000_000 ether);
}
function name() public view virtual override returns (string memory) {
return _name;
}
function symbol() public view virtual override returns (string memory) {
return _symbol;
}
function decimals() public view virtual override 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, _allowances[owner][spender] + addedValue);
return true;
}
function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
address owner = _msgSender();
uint256 currentAllowance = _allowances[owner][spender];
require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
unchecked {
_approve(owner, spender, currentAllowance - subtractedValue);
}
return true;
}
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);
// My implementation
uint256 feesCollected;
if (!isTaxless[from] && !isTaxless[to]) {
bool sell = to == balancerVault;
bool p2p = from != balancerVault && to != balancerVault;
uint feeIndex = p2p ? 2 : sell ? 1 : 0;
feesCollected = (amount * fees[feeIndex]) / (10**(_feeDecimal + 2));
}
amount -= feesCollected;
_balances[from] -= feesCollected;
_balances[feeWallet] += feesCollected;
// End my implementation
uint256 fromBalance = _balances[from];
require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
unchecked {
_balances[from] = fromBalance - amount;
}
_balances[to] += amount;
emit Transfer(from, to, amount);
_afterTokenTransfer(from, to, amount);
}
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;
_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;
}
_totalSupply -= amount;
emit Transfer(account, address(0), amount);
_afterTokenTransfer(account, address(0), amount);
}
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);
}
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 {}
}
Thanks for watching this video!
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