// SPDX-License-Identifier: MIT

pragma solidity ^0.8.4;

abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }
    function _msgData() internal view virtual returns (bytes calldata) {
        this;
        return msg.data;
    }
}

abstract contract Ownable is Context {
    address private _owner;
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
    constructor () {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }
    function owner() public view virtual returns (address) {
        return _owner;
    }
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }
    function renounceOwnership() public virtual onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

interface IST20 {
    function name() external view returns (string memory);
    function symbol() external view returns (string memory);
    function decimals() external view returns (uint8);
    function totalSupply() external view returns (uint256);
    function balanceOf(address account) external view returns (uint256);
    function getOwner() external view returns (address);
    function transfer(address recipient, uint256 amount) external returns (bool);
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
    function approve(address spender, uint256 amount) external returns (bool);
    function allowance(address _owner, address spender) external view returns (uint256);
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

contract ST20 is Ownable, IST20 {
    mapping (address => uint256) private _balances;
    mapping (address => mapping (address => uint256)) private _allowances;
    uint256 private _totalSupply;
    string private _name;
    string private _symbol;
    uint8 private _decimals;

    constructor (string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
        _decimals = 18;
    }
    function _setupDecimals(uint8 decimals_) internal {
        _decimals = decimals_;
    }
    function name() public view override returns (string memory) {
        return _name;
    }
    function symbol() public view override returns (string memory) {
        return _symbol;
    }
    function decimals() public view override returns (uint8) {
        return _decimals;
    }
    function totalSupply() public view override returns (uint256) {
        return _totalSupply;
    }
    function balanceOf(address account) public view override returns (uint256) {
        return _balances[account];
    }
    function getOwner() public view override returns (address) {
        return owner();
    }
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }
    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        uint256 currentAllowance = _allowances[sender][_msgSender()];
        require(currentAllowance >= amount, "Token: transfer amount exceeds allowance");
        _approve(sender, _msgSender(), currentAllowance - amount);

        return true;
    }
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender] + addedValue);
        return true;
    }
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        uint256 currentAllowance = _allowances[_msgSender()][spender];
        require(currentAllowance >= subtractedValue, "Token: decreased allowance below zero");
        _approve(_msgSender(), spender, currentAllowance - subtractedValue);
        return true;
    }
    function _transfer(address sender, address recipient, uint256 amount) internal virtual {
        require(sender != address(0), "Token: transfer from the zero address");
        require(recipient != address(0), "Token: transfer to the zero address");
        _beforeTokenTransfer(sender, recipient, amount);
        uint256 senderBalance = _balances[sender];
        require(senderBalance >= amount, "Token: transfer amount exceeds balance");
        _balances[sender] = senderBalance - amount;
        _balances[recipient] += amount;
        emit Transfer(sender, recipient, amount);
    }
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "Token: mint to the zero address");
        _beforeTokenTransfer(address(0), account, amount);
        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);
    }
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "Token: burn from the zero address");
        _beforeTokenTransfer(account, address(0), amount);
        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "Token: burn amount exceeds balance");
        _balances[account] = accountBalance - amount;
        _totalSupply -= amount;
        emit Transfer(account, address(0), amount);
    }
    function _approve(address owner, address spender, uint256 amount) internal virtual {
        require(owner != address(0), "Token: approve from the zero address");
        require(spender != address(0), "Token: approve to the zero address");
        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }
    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }
}

interface IPayable {
    function pay(string memory serviceName) external payable;
}

abstract contract ServicePayer {
    constructor (address payable receiver, string memory serviceName) payable {
        IPayable(receiver).pay{value: msg.value}(serviceName);
    }
}

contract ST_Standard_Token is ST20, ServicePayer {
    constructor (
        string memory name,
        string memory symbol,
        uint8 decimals,
        uint256 initialBalance,
        address payable feeReceiver
    )
        ST20(name, symbol)
        ServicePayer(feeReceiver, "ST_Standard_Token")
        payable
    {
        require(initialBalance > 0, "ST_Standard_Token: supply cannot be zero");
        _setupDecimals(decimals);
        _mint(_msgSender(), initialBalance);
    }
}