// File: GOONappToken.sol



pragma solidity ^0.6.0;

contract GOONappToken {
string  public name = "GOON Token";
    string  public symbol = "GOON";
    string  public standard = "GOON Token v1.0";
    uint256 public totalSupply;

    event Transfer(
        address indexed _from,
        address indexed _to,
        uint256 _value
    );

    event Approval(
        address indexed _owner,
        address indexed _spender,
        uint256 _value
    );

    mapping(address => uint256) public balanceOf;
    mapping(address => mapping(address => uint256)) public allowance;

    constructor (uint256 _initialSupply) public {
        balanceOf[msg.sender] = _initialSupply;
        totalSupply = _initialSupply;
    }

    function transfer(address _to, uint256 _value) public returns (bool success) {
        require(balanceOf[msg.sender] >= _value);

        balanceOf[msg.sender] -= _value;
        balanceOf[_to] += _value;

        emit Transfer(msg.sender, _to, _value);

        return true;
    }

    function approve(address _spender, uint256 _value) public returns (bool success) {
        allowance[msg.sender][_spender] = _value;

        emit Approval(msg.sender, _spender, _value);

        return true;
    }

    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        require(_value <= balanceOf[_from]);
        require(_value <= allowance[_from][msg.sender]);

        balanceOf[_from] -= _value;
        balanceOf[_to] += _value;

        allowance[_from][msg.sender] -= _value;

        emit Transfer(_from, _to, _value);

        return true;
    }
}
// File: GOONappTokenSale.sol



pragma solidity ^0.6.0;

import "./GOONappToken.sol";

contract GOONappTokenSale {
    address payable admin;
    GOONappToken public tokenContract;
    uint256 public tokenPrice;
    uint256 public tokensSold;

    event Sell(address _buyer, uint256 _amount);
    event Bought(uint256 amount);

    constructor (GOONappToken _tokenContract, uint256 _tokenPrice) public payable{
        admin = msg.sender;
        tokenContract = _tokenContract;
        tokenPrice = _tokenPrice;
    }

    function multiply(uint x, uint y) internal pure returns (uint z) {
        require(y == 0 || (z = x * y) / y == x);
    }

    receive() external payable {
        if (msg.sender == admin) {
            admin.send(address(this).balance);
        }
        else {
            uint256 amountTobuy = msg.value / tokenPrice;
            uint256 dexBalance = tokenContract.balanceOf(address(this));
            require(amountTobuy > 19999, "Minimal amount to buy is 20000");
            require(amountTobuy <= dexBalance, "Not enough tokens in the reserve");
            require(tokenContract.transfer(msg.sender, amountTobuy));
            tokensSold += amountTobuy;
            emit Sell(msg.sender, amountTobuy);
        }
    }

    function buyTokens(uint256 _numberOfTokens) public payable {
        require(msg.value == multiply(_numberOfTokens, tokenPrice));
        require(tokenContract.balanceOf(address(this)) >= _numberOfTokens);
        require(tokenContract.transfer(msg.sender, _numberOfTokens));
        tokensSold += _numberOfTokens;
        emit Sell(msg.sender, _numberOfTokens);
    }

    function endSale() public {
        require(msg.sender == admin);
        require(tokenContract.transfer(admin, tokenContract.balanceOf(address(this))));
        selfdestruct(admin);
    }
}