// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;

library SafeMath {
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        return c;
    }

    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

interface IERC20 {
    function totalSupply() external view returns (uint256);
    function balanceOf(address account) external view returns (uint256);
    function transfer(address recipient, 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 sender, address recipient, 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 Callable {
	function tokenCallback(address _from, uint256 _tokens, bytes calldata _data) external returns (bool);
}


contract Context {
    
    constructor () internal { }

    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this;
        return msg.data;
    }
}

contract Ownable {

    bool public paused = false;

    address public owner;

    event OwnershipTransferred(address previousOwner, address newOwner);
    event Pause();
    event Unpause();

    modifier onlyOwner {
        require(msg.sender == owner,"must be owner");
        _;
    }

    modifier whenNotPaused() {
        require(!paused);
        _;
    }

    modifier whenPaused() {
        require(paused);
        _;
    }

    constructor() public {
        owner = msg.sender;
    }


    function isOwner(address wallet) public view returns(bool) {
        return wallet == owner;
    }


    function transferOwnership(address _newOwner, address _oldOwner) public onlyOwner {
        _transferOwnership(_newOwner, _oldOwner);
    }


    function pause() public onlyOwner whenNotPaused {

        paused = true;
        emit Pause();
    }


    function unpause() public onlyOwner whenPaused {
        paused = false;
        emit Unpause();
    }

    function _transferOwnership(address _newOwner, address _oldOwner) internal {
        require(_newOwner != address(0));
        owner = _newOwner;
        emit OwnershipTransferred(_oldOwner, _newOwner);
    }
}


contract ERC20 is Context, IERC20,Ownable {
  using SafeMath for uint256;

    mapping (address => uint256) private _balances;
    mapping (address => mapping (address => uint256)) private _allowances;
    mapping (address => bool) _burnWhitelist;

    string private _name;
    string private _symbol;
    uint8 private _decimals;
    uint256 private _totalSupply;

    constructor()public{
        _name = "USDH";
        _symbol = "USDH";
        _decimals = 18;
        _totalSupply = 1000000000e18;  //100,000,000
        
        _balances[msg.sender] = _totalSupply;
        emit Transfer(address(0x0), msg.sender, _totalSupply);
    }
    
    function name() public view returns (string memory) {
        return _name;
    }

    function symbol() public view returns (string memory) {
        return _symbol;
    }
    function decimals() public view 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 transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, 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) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
        return true;
    }

    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
        return true;
    }

    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }

    function _transfer(address sender, address recipient, uint256 amount) internal virtual returns(uint256){

        _beforeTokenTransfer(sender, recipient, amount);

        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
        return amount;
    }
    
    function transferAndCall(address _to, uint256 _tokens, bytes calldata _data) external returns (bool) {
		uint256 _transferred = _transfer(_msgSender(), _to, _tokens);
		uint32 _size;
		assembly {
			_size := extcodesize(_to)
		}
		if (_size > 0) {
			require(Callable(_to).tokenCallback(_msgSender(), _transferred, _data));
		}
		return true;
	}

    function _approve(address owner, address spender, uint256 amount) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }
}

contract USDH is ERC20 {

    constructor() ERC20()  public {
        
    }
    
    

}