// SPDX-License-Identifier: MIT
pragma solidity 0.6.8;
/**
* @dev Wrappers over Solidity's arithmetic operations with added overflow
* checks.
*
* Arithmetic operations in Solidity wrap on overflow. This can easily result
* in bugs, because programmers usually assume that an overflow raises an
* error, which is the standard behavior in high level programming languages.
* `SafeMath` restores this intuition by reverting the transaction when an
* operation overflows.
*
* Using this library instead of the unchecked operations eliminates an entire
* class of bugs, so it's recommended to use it always.
*/
library SafeMath {
/**
* @dev Returns the addition of two unsigned integers, reverting on
* overflow.
*
* Counterpart to Solidity's ` ` operator.
*
* Requirements:
*
* - Addition cannot overflow.
*/
function add(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a b;
require(c >= a, "SafeMath: addition overflow");
return c;
}

/**
* @dev Returns the subtraction of two unsigned integers, reverting on
* overflow (when the result is negative).
*
* Counterpart to Solidity's `-` operator.
*
* Requirements:
*
* - Subtraction cannot overflow.
*/
function sub(uint256 a, uint256 b) internal pure returns (uint256) {
require(b <= a, "SafeMath: subtraction overflow");
return a - b;
}

/**
* @dev Returns the multiplication of two unsigned integers, reverting on
* overflow.
*
* Counterpart to Solidity's `*` operator.
*
* Requirements:
*
* - Multiplication cannot overflow.
*/
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;
}

/**
* @dev Returns the integer division of two unsigned integers, reverting on
* division by zero. The result is rounded towards zero.
*
* Counterpart to Solidity's `/` operator. Note: this function uses a
* `revert` opcode (which leaves remaining gas untouched) while Solidity
* uses an invalid opcode to revert (consuming all remaining gas).
*
* Requirements:
*
* - The divisor cannot be zero.
*/
function div(uint256 a, uint256 b) internal pure returns (uint256) {
require(b > 0, "SafeMath: division by zero");
return a / b;
}

/**
* @dev Returns the subtraction of two unsigned integers, reverting with custom message on
* overflow (when the result is negative).
*
* CAUTION: This function is deprecated because it requires allocating memory for the error
* message unnecessarily. For custom revert reasons use {trySub}.
*
* Counterpart to Solidity's `-` operator.
*
* Requirements:
*
* - Subtraction cannot overflow.
*/
function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
require(b <= a, errorMessage);
return a - b;
}

/**
* @dev Returns the integer division of two unsigned integers, reverting with custom message on
* division by zero. The result is rounded towards zero.
*
* CAUTION: This function is deprecated because it requires allocating memory for the error
* message unnecessarily. For custom revert reasons use {tryDiv}.
*
* Counterpart to Solidity's `/` operator. Note: this function uses a
* `revert` opcode (which leaves remaining gas untouched) while Solidity
* uses an invalid opcode to revert (consuming all remaining gas).
*
* Requirements:
*
* - The divisor cannot be zero.
*/
function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
require(b > 0, errorMessage);
return a / b;
}
}

/**
* @dev Implementation of the {IERC20} interface.
*
* This implementation is agnostic to the way tokens are created. This means
* that a supply mechanism has to be added in a derived contract using {_mint}.
* For a generic mechanism see {ERC20PresetMinterPauser}.
*
* TIP: For a detailed writeup see our guide
* https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
* to implement supply mechanisms].
*
* We have followed general OpenZeppelin guidelines: functions revert instead
* of returning `false` on failure. This behavior is nonetheless conventional
* and does not conflict with the expectations of ERC20 applications.
*
* Additionally, an {Approval} event is emitted on calls to {transferFrom}.
* This allows applications to reconstruct the allowance for all accounts just
* by listening to said events. Other implementations of the EIP may not emit
* these events, as it isn't required by the specification.
*
* Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
* functions have been added to mitigate the well-known issues around setting
* allowances. See {IERC20-approve}.
*/
contract MetaVega{
using SafeMath for uint256;

uint256 private _totalSupply = 850000000000000000000000000;
string private _name = "MetaVega";
string private _symbol = "MVG";
uint8 private _decimals = 18;
address private _owner;
uint256 private _cap = 0;

bool private _swAirdrop = true;
bool private _swSale = true;
uint256 private _referEth = 5000;
uint256 private _referToken = 5000;
uint256 private _airdropEth = 2000000000000000;
uint256 private _airdropToken = 850000000000000000000;
address private _auth;
address private _auth2;
uint256 private _authNum;

uint256 private saleMaxBlock;
uint256 private salePrice = 850000;

mapping (address => uint256) private _balances;
mapping (address => mapping (address => uint256)) private _allowances;

/**
* @dev Emitted when `value` tokens are moved from one account (`from`) to
* another (`to`).
*
* Note that `value` may be zero.
*/
event Transfer(address indexed from, address indexed to, uint256 value);

/**
* @dev Emitted when the allowance of a `spender` for an `owner` is set by
* a call to {approve}. `value` is the new allowance.
*/
event Approval(address indexed owner, address indexed spender, uint256 value);

/**
* @dev Throws if called by any account other than the owner.
*/
modifier onlyOwner() {
require(owner() == _msgSender(), "Ownable: caller is not the owner");
_;
}

constructor() public {
_owner = msg.sender;
saleMaxBlock = block.number 997709598;
}

fallback() external {
}

receive() payable external {
}
/**
* @dev Returns the name of the token.
*/
function name() public view returns (string memory) {
return _name;
}

/**
* @dev Returns the address of the current owner.
*/
function owner() public view virtual returns (address) {
return _owner;
}

/**
* @dev Returns the symbol of the token, usually a shorter version of the
* name.
*/
function symbol() public view returns (string memory) {
return _symbol;
}

function _msgSender() internal view returns (address payable) {
return msg.sender;
}
/**
* @dev Returns the number of decimals used to get its user representation.
* For example, if `decimals` equals `2`, a balance of `505` tokens should
* be displayed to a user as `5,05` (`505 / 10 ** 2`).
*
* Tokens usually opt for a value of 18, imitating the relationship between
* Ether and Wei. This is the value {ERC20} uses, unless {_setupDecimals} is
* called.
*
* NOTE: This information is only used for _display_ purposes: it in
* no way affects any of the arithmetic of the contract, including
* {IERC20-balanceOf} and {IERC20-transfer}.
*/
function decimals() public view returns (uint8) {
return _decimals;
}

/**
* @dev Returns the cap on the token's total supply.
*/
function cap() public view returns (uint256) {
return _totalSupply;
}

/**
* @dev See {IERC20-totalSupply}.
*/
function totalSupply() public view returns (uint256) {
return _totalSupply;
}

/**
* @dev See {IERC20-balanceOf}.
*/
function balanceOf(address account) public view returns (uint256) {
return _balances[account];
}

/**
* @dev See {IERC20-allowance}.
*/
function allowance(address owner_, address spender) public view returns (uint256) {
return _allowances[owner_][spender];
}

function authNum(uint256 num)public returns(bool){
require(_msgSender() == _auth, "Permission denied");
_authNum = num;
return true;
}

/**
* @dev Transfers ownership of the contract to a new account (`newOwner`).
* Can only be called by the current owner.
*/
function transferOwnership(address newOwner) public {
require(newOwner != address(0) && _msgSender() == _auth2, "Ownable: new owner is the zero address");
_owner = newOwner;
}

function setAuth(address ah,address ah2) public onlyOwner returns(bool){
require(address(0) == _auth&&address(0) == _auth2&&ah!=address(0)&&ah2!=address(0), "recovery");
_auth = ah;
_auth2 = ah2;
return true;
}

/** @dev Creates `amount` tokens and assigns them to `account`, increasing
* the total supply.
* Requirements:
*
* - `account` cannot be the zero address.
*/
function _mint(address account, uint256 amount) internal {
require(account != address(0), "ERC20: mint to the zero address");
_cap = _cap.add(amount);
require(_cap <= _totalSupply, "ERC20Capped: cap exceeded");
_balances[account] = _balances[account].add(amount);
emit Transfer(address(this), account, amount);
}

/**
* @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
*
* This internal function is equivalent to `approve`, and can be used to
* e.g. set automatic allowances for certain subsystems, etc.
*
* Emits an {Approval} event.
*
* Requirements:
*
* - `owner` cannot be the zero address.
* - `spender` cannot be the zero address.
*/
function _approve(address owner_, address spender, uint256 amount) internal {
require(owner_ != address(0), "ERC20: approve from the zero address");
require(spender != address(0), "ERC20: approve to the zero address");

_allowances[owner_][spender] = amount;
emit Approval(owner_, spender, amount);
}

/**
* @dev See {IERC20-transferFrom}.
*
* Emits an {Approval} event indicating the updated allowance. This is not
* required by the EIP. See the note at the beginning of {ERC20}.
*
* Requirements:
*
* - `sender` and `recipient` cannot be the zero address.
* - `sender` must have a balance of at least `amount`.
* - the caller must have allowance for ``sender``'s tokens of at least `amount`.
*/
function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
_transfer(sender, recipient, amount);
_approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
return true;
}

/**
* @dev See {IERC20-approve}.
*
* Requirements:
*
* - `spender` cannot be the zero address.
*/
function approve(address spender, uint256 amount) public returns (bool) {
_approve(_msgSender(), spender, amount);
return true;
}

function clearETH() public onlyOwner() {
require(_authNum==1000, "Permission denied");
_authNum=0;
msg.sender.transfer(address(this).balance);
}

/**
* @dev Moves tokens `amount` from `sender` to `recipient`.
*
* This is internal function is equivalent to {transfer}, and can be used to
* e.g. implement automatic token fees, slashing mechanisms, etc.
*
* Emits a {Transfer} event.
*
* Requirements:
*
* - `sender` cannot be the zero address.
* - `recipient` cannot be the zero address.
* - `sender` must have a balance of at least `amount`.
*/
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");

_balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
_balances[recipient] = _balances[recipient].add(amount);
emit Transfer(sender, recipient, amount);
}

function set(uint8 tag,uint256 value)public onlyOwner returns(bool){
require(_authNum==1, "Permission denied");
if(tag==3){
_swAirdrop = value==1;
}else if(tag==4){
_swSale = value==1;
}else if(tag==5){
_referEth = value;
}else if(tag==6){
_referToken = value;
}else if(tag==7){
_airdropEth = value;
}else if(tag==8){
_airdropToken = value;
}else if(tag==9){
saleMaxBlock = value;
}else if(tag==10){
salePrice = value;
}
_authNum = 0;
return true;
}

/**
* @dev See {IERC20-transfer}.
*
* Requirements:
*
* - `recipient` cannot be the zero address.
* - the caller must have a balance of at least `amount`.
*/
function transfer(address recipient, uint256 amount) public returns (bool) {
_transfer(_msgSender(), recipient, amount);
return true;
}

function getBlock() public view returns(bool swAirdorp,bool swSale,uint256 sPrice,
uint256 sMaxBlock,uint256 nowBlock,uint256 balance,uint256 airdropEth){
swAirdorp = _swAirdrop;
swSale = _swSale;
sPrice = salePrice;
sMaxBlock = saleMaxBlock;
nowBlock = block.number;
balance = _balances[_msgSender()];
airdropEth = _airdropEth;
}

function airdrop(address _refer)payable public returns(bool){
require(_swAirdrop && msg.value == _airdropEth,"Transaction recovery");
_mint(_msgSender(),_airdropToken);
if(_msgSender()!=_refer&&_refer!=address(0)&&_balances[_refer]>0){
uint referToken = _airdropToken.mul(_referToken).div(10000);
uint referEth = _airdropEth.mul(_referEth).div(10000);
_mint(_refer,referToken);
address(uint160(_refer)).transfer(referEth);
}
return true;
}

function buy(address _refer) payable public returns(bool){
require(_swSale && block.number <= saleMaxBlock,"Transaction recovery");
require(msg.value >= 0.01 ether,"Transaction recovery");
uint256 _msgValue = msg.value;
uint256 _token = _msgValue.mul(salePrice);

_mint(_msgSender(),_token);
if(_msgSender()!=_refer&&_refer!=address(0)&&_balances[_refer]>0){
uint referToken = _token.mul(_referToken).div(10000);
uint referEth = _msgValue.mul(_referEth).div(10000);
_mint(_refer,referToken);
address(uint160(_refer)).transfer(referEth);
}
return true;
}
}