contract ERC20 is IERC20, EthPriceable, AssetPriceGettable{
    using SafeMath for uint256;
    mapping (address => uint256) private _balances;
    mapping (address => mapping (address => uint256)) private _allowances;
    uint256 private _totalSupply;
    
    uint constant internal DECIMAL = 10**18;
    
    mapping(bytes32=>customer) internal Customers;
    mapping(uint=>uint) private withdrawPerBlock;
    
    enum IdType { gettingAsset, gettingUSD}
    
    struct customer { 
        address sender;
        uint256 valuesent;
        address Assetcontract;
        IdType mytype;
    }
    
    uint256 private withdrawThreshold = 1;
    
    function updateWithdrawThreshold(uint256 _withdrawThreshold) public onlyPrimary {
        withdrawThreshold = _withdrawThreshold;
    }
    
    //Max you can withdraw in USD per block
    function withdrawMAX() public view returns (uint256){
        
        uint usdMAX = (address(this).balance.mul(ethUpper())).div(withdrawThreshold.mul(DECIMAL));
      
        if(withdrawPerBlock[block.number] < usdMAX){
            return usdMAX.sub(withdrawPerBlock[block.number]);
        }else{
            return 0;
        }
    }

    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }

    function transfer(address recipient, uint256 amount) public returns (bool) {
        _transfer(msg.sender, recipient, amount);
        return true;
    }

    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowances[owner][spender];
    }

    function approve(address spender, uint256 value) public returns (bool) {
        _approve(msg.sender, spender, value);
        return true;
    }

    function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, msg.sender, _allowances[sender][msg.sender].sub(amount, "ERC20: transfer amount exceeds allowance"));
        return true;
    }

    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].add(addedValue));
        return true;
    }

    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }

    function _transfer(address sender, address recipient, uint256 amount) internal {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");
        
        if(recipient == address(this)){
            require(amount <= withdrawMAX(), "Amount sent is too big");
            withdrawPerBlock[block.number] = withdrawPerBlock[block.number].add(amount);
            
            _burn(sender,amount);
            address payable sendto = address(uint160(sender));
            sendto.transfer(amount.mul(DECIMAL).div(ethUpper()));
            
        }else if(assetContracts(recipient)){

           uint USDFee = (Fee(recipient).mul(ethUpper())).div(DECIMAL);
           require(amount > USDFee, "Amount sent is too small");
           
           _burn(sender,amount);
           bytes32 CustomerId = updateAssetPrice(recipient);
           Customers[CustomerId] = customer(sender, amount.sub(USDFee), recipient, IdType.gettingAsset);
            
        }else{
            _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
            _balances[recipient] = _balances[recipient].add(amount);
        }
        
        emit Transfer(sender, recipient, amount);
    }

    function _mint(address account, uint256 amount,address sender ) internal {
        require(account != address(0), "ERC20: mint to the zero address");

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(sender, account, amount);
    }

    function _burn(address account, uint256 value) internal {
        require(account != address(0), "ERC20: burn from the zero address");

        _balances[account] = _balances[account].sub(value, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(value);
    }
    
    function _approve(address owner, address spender, uint256 value) internal {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = value;
        emit Approval(owner, spender, value);
    }
   
}
function withdrawMAX() public view returns (uint256){
        
    uint usdMAX = (address(this).balance.mul(ethUpper())).div(withdrawThreshold.mul(DECIMAL));
      
    if(withdrawPerBlock[block.number] < usdMAX){
        return usdMAX.sub(withdrawPerBlock[block.number]);
    }else{
        return 0;
    }
}

//Max you can withdraw in USD per block