// SPDX-License-Identifier: MIT

pragma solidity ^0.8.12;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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 Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `from` to `to` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address from, address to, uint256 amount) external returns (bool);
}

interface IUniswapV2Factory {
    function createPair(address tokenA, address tokenB) external returns (address pair);
}

interface IUniswapV2Router02 {
    function swapExactTokensForETHSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;

    function factory() external pure returns (address);

    /* solhint-disable-next-line func-name-mixedcase */
    function WETH() external pure returns (address);

    function addLiquidityETH(
        address token,
        uint amountTokenDesired,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external payable returns (uint amountToken, uint amountETH, uint liquidity);
}

contract KMINING is Context, IERC20 {
    mapping(address => uint256) private _balances;
    mapping(address => mapping(address => uint256)) private _allowances;


    address payable private constant TREASURY_WALLET = payable(0x375Ad7A3f94441b2A5b093169893aA3F6D1D3d3a);

    uint256 public constant INIT_TAX = 30;
    uint256 public constant N_FIRST_SWAPS = 50;
    uint256 public _currentSwap;

    uint256 public constant BUY_TAX = 3;
    uint256 public constant SELL_TAX = 3;

    string private constant _NAME = "KMINING";
    string private constant _SYMBOL = "KMN";
    uint8 private constant _DECIMALS = 9;
    uint256 private constant _SUPPLY = 100_000_000 * 10 ** _DECIMALS; 

    uint256 public constant MAX_TX_AMOUNT = _SUPPLY / 100; //1%
    uint256 public constant MAX_WALLET_SIZE = _SUPPLY / 50; //2%
    uint256 public constant TAX_SWAP_THRESHOLD = _SUPPLY / 2000; //0.05%
    uint256 public constant MAX_TAX_SWAP = _SUPPLY / 1000; //0.1%

    IUniswapV2Router02 private immutable uniswapV2Router;
    address private immutable uniswapV2Pair;
    bool private tradingOpen;
    bool private inSwap = false;
    bool private swapEnabled = false;

    modifier lockTheSwap() {
        inSwap = true;
        _;
        inSwap = false;
    }

    constructor() {
        _balances[TREASURY_WALLET] = _SUPPLY;

        uniswapV2Router = IUniswapV2Router02(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);
        uniswapV2Pair = IUniswapV2Factory(uniswapV2Router.factory()).createPair(address(this), uniswapV2Router.WETH());

        emit Transfer(address(0), TREASURY_WALLET, _SUPPLY);
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public pure returns (string memory) {
        return _NAME;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public pure returns (string memory) {
        return _SYMBOL;
    }

    /**
     * @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 this function is
     * overloaded;
     *
     * 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 pure returns (uint8) {
        return _DECIMALS;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public pure override returns (uint256) {
        return _SUPPLY;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view override returns (uint256) {
        return _balances[account];
    }

    /**
     * @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 override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    /**
     * @dev See previous function, same functionality but recipient is dead address.
     *
     * Requirements:
     *
     * - the caller must have a balance of at least `amount`.
     */
    function burn(uint256 amount) public returns (bool) {
        _transfer(_msgSender(), address(0xdEaD), amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @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 override returns (bool) {
        require(_allowances[sender][_msgSender()] >= amount, "ERC20: transfer amount exceeds allowance");
        _transfer(sender, recipient, amount);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()] - amount);
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender] + addedValue);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        uint256 currentAllowance = _allowances[_msgSender()][spender];
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        _approve(_msgSender(), spender, currentAllowance - subtractedValue);

        return true;
    }

    /**
     * @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 from, address to, uint256 amount) private {
        require(from != address(0), "ERC20: transfer from the zero address");
        require(to != address(0), "ERC20: transfer to the zero address");
        require(amount > 0, "Transfer amount must be greater than zero");

        if (to != address(this) && to != uniswapV2Pair && _currentSwap < N_FIRST_SWAPS && to != TREASURY_WALLET && from != TREASURY_WALLET) {
            uint256 heldTokens = balanceOf(to);
            require(
                (heldTokens + amount) <= MAX_WALLET_SIZE,
                "Total Holding is currently limited, you can not buy that much."
            );
            require(amount <= MAX_TX_AMOUNT, "TX Limit Exceeded");
        }

        uint256 taxAmount = 0;   
        uint256 taxApply = 0;    
        if(to != TREASURY_WALLET && from != TREASURY_WALLET) {
            if (from == uniswapV2Pair && to != address(this)) {                
                taxApply = _currentSwap < N_FIRST_SWAPS ? INIT_TAX : BUY_TAX;
            }
            if (to == uniswapV2Pair && from != address(this)) {
                taxApply = _currentSwap < N_FIRST_SWAPS ? INIT_TAX : SELL_TAX;
            }
        }
        taxAmount = amount * taxApply / 100;        

        uint256 contractTokenBalance = balanceOf(address(this));
        if (!inSwap && to == uniswapV2Pair && swapEnabled && contractTokenBalance > TAX_SWAP_THRESHOLD) {
            swapTokensForEth(min(amount, min(contractTokenBalance, MAX_TAX_SWAP)));
            uint256 contractETHBalance = address(this).balance;
            if (contractETHBalance > 0) {
                sendETHToFee(address(this).balance);
            }
        }

        if (taxAmount > 0) {
            _currentSwap++;
            _balances[address(this)] += taxAmount;
            emit Transfer(from, address(this), taxAmount);
        }

        _balances[from] -= amount;
        _balances[to] += (amount - taxAmount);
        emit Transfer(from, to, amount - taxAmount);
    }

    /**
     * @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) private {
        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);
    }

    function min(uint256 a, uint256 b) private pure returns (uint256) {
        return (a > b) ? b : a;
    }

    function swapTokensForEth(uint256 tokenAmount) private lockTheSwap {
        address[] memory path = new address[](2);
        path[0] = address(this);
        path[1] = uniswapV2Router.WETH();
        _approve(address(this), address(uniswapV2Router), tokenAmount);
        uniswapV2Router.swapExactTokensForETHSupportingFeeOnTransferTokens(
            tokenAmount,
            0,
            path,
            address(this),
            block.timestamp
        );
    }

    function sendETHToFee(uint256 amount) private {
        TREASURY_WALLET.transfer(amount);
    }

    function openTrading() external payable {
        require(!tradingOpen, "Trading is already open");
        require(msg.sender == TREASURY_WALLET, "Not allowed");
        
        _approve(address(this), address(uniswapV2Router), type(uint256).max);        
        uniswapV2Router.addLiquidityETH{value: msg.value}(
            address(this),
            balanceOf(address(this)),
            0,
            0,
            address(msg.sender),
            block.timestamp
        );
        IERC20(uniswapV2Pair).approve(address(uniswapV2Router), type(uint).max);
        swapEnabled = true;
        tradingOpen = true;
    }

    /* solhint-disable-next-line no-empty-blocks */
    receive() external payable {}
}