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contracts...master.sol

pragma solidity ^0.8.0;
//SPDX-License-Identifier: SPDX-License-Identifier: <SPDX-License>

import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/ERC20.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/IERC20.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/Context.sol"; 
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/math/SafeMath.sol"; 

//import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/";
// https://docs.openzeppelin.com/contracts/4.x/erc20
// https://docs.soliditylang.org/en/latest/common-patterns.html
// https://medium.com/@david.michael/sending-eth-to-a-contract-address-a73c84e2cc9c
contract Token is ERC20 {
    address payable private _owner;
    uint256 private _ExRate;
    uint256 private _Fees;
    uint256 private _ExRateBase;
    address private _contract_address;
    address payable private _payable_contract_address;
    constructor () ERC20("DEFI ALX TOKEN", "ALX") {
        uint256 supply = (10**6) * (10 ** uint256(decimals()));
        _mint(msg.sender,supply);// (10**12) * (10 ** uint256(decimals())));
        _owner=payable (_msgSender());
        _ExRate    =  50000000;
        _ExRateBase=1000000000;
        _Fees=_ExRate/1000;
        _contract_address=address(this);
        _payable_contract_address=payable(_contract_address);
        _transfer( _owner,_contract_address,supply );
    }
    event TxnLog(address indexed sender, string message);
    function burrn(uint256 val) public {  
        _burn( address(_msgSender()),val);
    }
    function minnt(uint256 val) public {  
        require(_msgSender() == _owner);
        _mint(_contract_address,val);
    }
    function showOwner() public view returns(address) {
        return _owner;
    }
    function buyToken( ) public payable {
        // Call returns a boolean value indicating success or failure.
        // This is the current recommended method to use. 
        uint256 weii = msg.value;
        (bool sent, bytes memory data) = _contract_address.call{value: weii}("");
        _transfer(  _contract_address,_msgSender(),getTokVal(weii));
        emit TxnLog(_msgSender(),"Bought ALX");
        require(sent, "Failed to send Ether");
    }
    // function sellToken(uint256 tok) public { 
    //     _transfer( _msgSender(),_owner,getEthVal(tok));
    //     (bool sent, bytes memory data) = (_msgSender()).call{value: msg.value}("");
    //     emit TxnLog(_msgSender(),"Sold ALX");
    //     require(sent, "Failed to send Ether");
    // }
    function getTokVal(uint256 tok) public view returns(uint256){ // no fee
        return SafeMath.div( SafeMath.mul(tok,_ExRateBase), _ExRate);
    }
    function getEthVal(uint256 tok) public view returns(uint256){ // yes fee
        return SafeMath.mul( SafeMath.mul(tok,_ExRateBase), SafeMath.sub(_ExRate,_Fees));
    }
    // see https://solidity-by-example.org/sending-ether/ 
    receive() external payable {buyToken();}
    fallback() external payable {buyToken();}
    function getBalEther() public view returns (uint) {
        return _contract_address.balance;
    }
}