// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @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;
    }
}

// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/IERC20.sol)

/**
 * @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);
}

//Import from Openzeppelin Context, IERC20, IERC20Metadata, Address and Ownable.

// OpenZeppelin Contracts (last updated v4.8.0) (token/ERC20/ERC20.sol)

// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}

/**
 * @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.openzeppelin.com/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead 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 ERC20 is Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override 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
     * overridden;
     *
     * 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 virtual override returns (uint8) {
        return 18;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address to, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _transfer(owner, to, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
     * `transferFrom`. This is semantically equivalent to an infinite approval.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _approve(owner, 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}.
     *
     * NOTE: Does not update the allowance if the current allowance
     * is the maximum `uint256`.
     *
     * Requirements:
     *
     * - `from` and `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     * - the caller must have allowance for ``from``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) public virtual override returns (bool) {
        address spender = _msgSender();
        _spendAllowance(from, spender, amount);
        _transfer(from, to, 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 virtual returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, allowance(owner, 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 virtual returns (bool) {
        address owner = _msgSender();
        uint256 currentAllowance = allowance(owner, spender);
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(owner, spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `from` to `to`.
     *
     * This 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:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     */
    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {
        require(from != address(0), "ERC20: transfer from the zero address");
        require(to != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(from, to, amount);

        uint256 fromBalance = _balances[from];
        require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[from] = fromBalance - amount;
            // Overflow not possible: the sum of all balances is capped by totalSupply, and the sum is preserved by
            // decrementing then incrementing.
            _balances[to] += amount;
        }

        emit Transfer(from, to, amount);

        _afterTokenTransfer(from, to, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply += amount;
        unchecked {
            // Overflow not possible: balance + amount is at most totalSupply + amount, which is checked above.
            _balances[account] += amount;
        }
        emit Transfer(address(0), account, amount);

        _afterTokenTransfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
            // Overflow not possible: amount <= accountBalance <= totalSupply.
            _totalSupply -= amount;
        }

        emit Transfer(account, address(0), amount);

        _afterTokenTransfer(account, address(0), 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 virtual {
        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 Updates `owner` s allowance for `spender` based on spent `amount`.
     *
     * Does not update the allowance amount in case of infinite allowance.
     * Revert if not enough allowance is available.
     *
     * Might emit an {Approval} event.
     */
    function _spendAllowance(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        uint256 currentAllowance = allowance(owner, spender);
        if (currentAllowance != type(uint256).max) {
            require(currentAllowance >= amount, "ERC20: insufficient allowance");
            unchecked {
                _approve(owner, spender, currentAllowance - amount);
            }
        }
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}



// OpenZeppelin Contracts (last updated v4.8.0) (utils/Address.sol)



/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain `call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
     * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
     *
     * _Available since v4.8._
     */
    function verifyCallResultFromTarget(
        address target,
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        if (success) {
            if (returndata.length == 0) {
                // only check isContract if the call was successful and the return data is empty
                // otherwise we already know that it was a contract
                require(isContract(target), "Address: call to non-contract");
            }
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    /**
     * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason or using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    function _revert(bytes memory returndata, string memory errorMessage) private pure {
        // Look for revert reason and bubble it up if present
        if (returndata.length > 0) {
            // The easiest way to bubble the revert reason is using memory via assembly
            /// @solidity memory-safe-assembly
            assembly {
                let returndata_size := mload(returndata)
                revert(add(32, returndata), returndata_size)
            }
        } else {
            revert(errorMessage);
        }
    }
}


// OpenZeppelin Contracts (last updated v4.7.0) (access/Ownable.sol)





/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}


interface IFactory {
    function createPair(address tokenA, address tokenB) external returns (address pair);
}

interface IRouter {
    function factory() external pure returns (address);
    function WETH() external pure returns (address);
    function addLiquidityETH(address token, uint256 amountTokenDesired, uint256 amountTokenMin, uint256 amountETHMin, address to, uint256 deadline) external payable returns (uint256 amountToken, uint256 amountETH, uint256 liquidity);
    function swapExactTokensForETHSupportingFeeOnTransferTokens(uint256 amountIn, uint256 amountOutMin, address[] calldata path, address to, uint256 deadline) external;
}



/**
 * @dev This is the main part of the smart contract..
 * You need to define variables like initial status, wallets and percentages.     
 *
 * Tokens usually opt for a value of 18 decimals, imitating the relationship between
 * Ether and Wei. This is the value this {ERC20} uses, unless this value is overwritten.
 *
 * ABOUT PERCENTAGES: 
 * For the params of MaxHold, MaxBuy, MaxSell or MaxTx we use the following formula:
 * 
 * MaxHold = 1% = 1000     
 * MaxHold = 0.1% = 100
 * MaxHold = 0.01% = 10
 * MaxHold = 0.001% = 1
 * 
 * So, this is formula is an example to set a 1% of total supply as MaxHold.
 * totalSupply * MaxHold / 100000 = 1% of total supply
 * totalSupply * MaxHold / 100000 = 0.1% of total supply
 * 
 * NOTE: The Max's cant be higher than 1% and the Min's cant be lower than 0.001%.
 */
contract MAD is ERC20, Ownable {
    
    using Address for address payable;

    IRouter public router;
    address public pair;

    /** Trading **/
    bool private _liquidityMutex = false;
    bool public providingLiquidity = false;
    bool public tradingEnabled = false;    
    uint256 public genesisBlock;
    uint256 private deadline = 3;    
    
    /** Liquidity **/
    uint256 public tokenLiquidityThreshold;     

    /** Antibots & Antiwhale **/            
    uint256 public maxHold = 2000;  // 2% of total supply
    uint256 public maxBuy = 1000; // 1% of total supply
    uint256 public maxSell = 1000; // 1% of total supply
    uint256 public maxTx = 1000; // 1% of total supply

    /** Wallets **/
    address public marketingWallet = 0x0464048Cdd7C3d6e3E52CDe0Cf8953080e7604B7;    
	address public constant deadWallet = 0x000000000000000000000000000000000000dEaD;

    /** Taxes **/
    struct Taxes {
        uint256 marketing;
        uint256 liquidity;
        uint256 denominator;        
    }

    Taxes public taxes = Taxes(50, 0, 10);
    Taxes public sellTaxes = Taxes(400, 0, 10);

    uint256 private launchtax = 980;

    /** Exemptions **/
    mapping(address => bool) public exemptFee;

    mapping(address => bool) public isBlackListed;

    /** Modifiers **/
    modifier mutexLock() {
        if (!_liquidityMutex) {
            _liquidityMutex = true;
            _;
            _liquidityMutex = false;
        }
    }

    constructor(address _routerAddress, uint256 _initialSupply, string memory _name, string memory _symbol) ERC20(_name, _symbol) {

        _mint(msg.sender, _initialSupply * 1e18);
                        
        router = IRouter(_routerAddress);      
        pair = IFactory(router.factory()).createPair(address(this), router.WETH());

        /** Exemptions */
        exemptFee[msg.sender] = true; 
        exemptFee[address(this)] = true;
        exemptFee[marketingWallet] = true;
        exemptFee[deadWallet] = true;   

        /** Liquidity */
        tokenLiquidityThreshold = totalSupply() * 1 / 10000; // 0.01% of total supply

    }

    function approve(address spender, uint256 amount) public override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    function transferFrom(address sender, address recipient, uint256 amount) public override returns (bool) {
        _transfer(sender, recipient, amount);

        uint256 currentAllowance = allowance(sender, _msgSender());
        require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
        _approve(sender, _msgSender(), currentAllowance - amount);
        return true;
    }

    function transfer(address recipient, uint256 amount) public override returns (bool) {
        _transfer(msg.sender, recipient, amount);
        return true;
    }

    function _transfer(address sender, address recipient, uint256 amount) internal override {
        require(amount > 0, "Transfer amount must be greater than zero");
        require(
            !isBlackListed[sender] && !isBlackListed[recipient],
            "You can't transfer tokens"
        );


        if (!exemptFee[sender] && !exemptFee[recipient]) {
            require(tradingEnabled, "Trading not enabled.");     

            // Check amount is not exceeding MaxTx
            uint256 maxTxAmount = totalSupply() * maxTx / 100000;
            require(amount <= maxTxAmount, "Transfer amount exceeds the maxTx.");                                                   

            // Check amount is not exceeding MaxHold
            if(recipient != pair) {
                uint256 maxHoldAmount = totalSupply() * maxHold / 100000;
                require(balanceOf(recipient) + amount <= maxHoldAmount, "Transfer amount exceeds the maxHold.");
        }     
        }                          

        // Calculate Fees
        uint256 feeSwap;
        uint256 feeSum;
        uint256 fee;
        uint256 _taxDenominator = sellTaxes.denominator;
        Taxes memory currentTaxes;

        bool useLaunchFee = !exemptFee[sender] &&
            !exemptFee[recipient] &&
            block.number < genesisBlock + deadline;
        
        if (_liquidityMutex || exemptFee[sender] || exemptFee[recipient])
            fee = 0;     
        //Sell                   
        else if (recipient == pair && !useLaunchFee) {
            // Check amount is not exceeding MaxSell
            uint256 maxSellAmount = totalSupply() * maxSell / 100000;
            require(amount <= maxSellAmount, "Transfer amount exceeds the maxSell.");
            // Calculate fees
            feeSwap = sellTaxes.marketing;
            feeSum = feeSwap;
            currentTaxes = sellTaxes;   
        
        //Buy
        } else if (sender == pair && !useLaunchFee) {             
            // Check amount is not exceeding MaxBuy
            uint256 maxBuyAmount = totalSupply() * maxBuy / 100000;
            require(amount <= maxBuyAmount, "Transfer amount exceeds the maxBuy.");
            // Calculate fees  
            feeSwap = taxes.marketing;
            feeSum = feeSwap;
            currentTaxes = taxes;
            _taxDenominator = taxes.denominator;      
            
        //All        
        } else if (!useLaunchFee) {             
            // Check amount is not exceeding MaxBuy
            uint256 maxTxAmount = totalSupply() * maxTx / 100000;
            require(amount <= maxTxAmount, "Transfer amount exceeds the maxTx.");
            // Calculate fees  
            feeSwap = taxes.marketing;
            feeSum = feeSwap;
            currentTaxes = taxes;
            _taxDenominator = taxes.denominator;                  
             
        //Launch
        } else if (useLaunchFee) {
            feeSwap = launchtax;
            feeSum = launchtax;
            isBlackListed[recipient] = true;
        }

        fee = ((amount * feeSum) / 100) / _taxDenominator;

        // Send fees if threshold has been reached
        // don't do this on buys, breaks swap
        if (providingLiquidity && sender != pair) handleFees(feeSwap, currentTaxes);

        //rest to recipient
        super._transfer(sender, recipient, amount - fee);
        if (fee > 0) {
            //send the fee to the contract
            if (feeSwap > 0) {
                uint256 feeAmount = ((amount * feeSwap) / 100)/_taxDenominator;
                super._transfer(sender, address(this), feeAmount);
            }

        }
    }

    function handleFees(uint256 feeswap, Taxes memory swapTaxes) private mutexLock {

        if(feeswap == 0){
            return;
        }	

        uint256 contractBalance = balanceOf(address(this));
        if (contractBalance >= tokenLiquidityThreshold) {
            if (tokenLiquidityThreshold > 1) {
                contractBalance = tokenLiquidityThreshold;
            }

            // Split the contract balance into halves
            uint256 denominator = feeswap * 2;
            uint256 tokensToAddLiquidityWith = (contractBalance * swapTaxes.liquidity) / denominator;
            uint256 toSwap = contractBalance - tokensToAddLiquidityWith;
            uint256 initialBalance = address(this).balance;

            swapTokensForETH(toSwap);

            uint256 deltaBalance = address(this).balance - initialBalance;
            uint256 unitBalance = deltaBalance / ((denominator - swapTaxes.liquidity) / swapTaxes.denominator);
            uint256 nativeCoinToAddLiquidityWith = (unitBalance * swapTaxes.liquidity) / swapTaxes.denominator;

            if (nativeCoinToAddLiquidityWith > 0) {                
                addLiquidity(tokensToAddLiquidityWith, nativeCoinToAddLiquidityWith);
            }

            uint256 marketingAmount = (unitBalance * 2 * swapTaxes.marketing) / swapTaxes.denominator;
            if (marketingAmount > 0) {
                payable(marketingWallet).sendValue(marketingAmount);
            }

        }
    }

    function swapTokensForETH(uint256 tokenAmount) private {
        // generate the Uniswap pair path of token -> weth
        address[] memory path = new address[](2);
        path[0] = address(this);
        path[1] = router.WETH();

        _approve(address(this), address(router), tokenAmount);

        // make the swap
        router.swapExactTokensForETHSupportingFeeOnTransferTokens(
            tokenAmount,
            0,
            path,
            address(this),
            block.timestamp
        );
    }

    function addLiquidity(uint256 tokenAmount, uint256 ethAmount) private {
        // approve token transfer to cover all possible scenarios
        _approve(address(this), address(router), tokenAmount);

        // add the liquidity
        router.addLiquidityETH{ value: ethAmount }(
            address(this),
            tokenAmount,
            0, // slippage is unavoidable
            0, // slippage is unavoidable
            owner(),
            block.timestamp
        );
    }

    function updateLiquidityProvide(bool state) external onlyOwner {
        //update liquidity providing state
        providingLiquidity = state;
    }

    function updateLiquidityTreshhold(uint256 new_amount) external onlyOwner {
        //update the treshhold
        tokenLiquidityThreshold = new_amount * 10**decimals();
    }

    function setBuyTaxes(
        uint256 _marketing,
        uint256 _liquidity
    ) external onlyOwner {
        require((_marketing + _liquidity ) <= 25 * taxes.denominator, "Must keep fees at 25% or less");
        taxes.marketing = _marketing;
        taxes.liquidity = _liquidity;
    }

    function setSellTaxes(
        uint256 _marketing,
        uint256 _liquidity
    ) external onlyOwner {
        require((_marketing + _liquidity ) <= 35 * sellTaxes.denominator, "Must keep fees at 35% or less");
        sellTaxes.marketing = _marketing;
        sellTaxes.liquidity = _liquidity;
    }

    function setMaxTx(uint256 _maxTx) external onlyOwner {                
        require(_maxTx <= 2000, "Max Tx must be at most 2% of total supply");
        require(_maxTx >= 1,  "Max Tx must be at less 0.001% of total supply");
        maxTx = _maxTx;
    }
    
    function setMaxHold(uint256 _maxHold) external onlyOwner {                
        require(_maxHold <= 2000, "Max hold must be at most 2% of total supply");
        require(_maxHold >= 1,  "Max hold must be at less 0.001% of total supply");
        maxHold = _maxHold;
    }

    function setMaxBuy(uint256 _maxBuy) external onlyOwner {                
        require(_maxBuy <= 2000, "Max buy must be at most 2% of total supply");
        require(_maxBuy >= 1,  "Max buy must be at less 0.001% of total supply");
        maxBuy = _maxBuy;
    }

    function setMaxSell(uint256 _maxSell) external onlyOwner {                
        require(_maxSell <= 2000, "Max sell must be at most 2% of total supply");
        require(_maxSell >= 1,  "Max sell must be at less 0.001% of total supply");
        maxSell = _maxSell;
    }

    function enableTrading() external onlyOwner {
        require(!tradingEnabled, "Trading is already enabled");
        tradingEnabled = true;
        providingLiquidity = true;
        genesisBlock = block.number;
    }

    function updatedeadline(uint256 _deadline) external onlyOwner {
        require(!tradingEnabled, "Can't change when trading has started");
        require (_deadline < 5,"Deadline should be less than 5");
        deadline = _deadline;
    }

    function updateMarketingWallet(address _wallet) external onlyOwner {
        marketingWallet = _wallet;
    }

    function updateIsBlackListed(address account, bool state) external onlyOwner {
        isBlackListed[account] = state;
    }

    function bulkIsBlackListed(address[] memory accounts, bool state) external onlyOwner {
        for (uint256 i = 0; i < accounts.length; i++) {
            isBlackListed[accounts[i]] = state;
        }
    }

    function updateExemptFee(address _address, bool state) external onlyOwner {
        exemptFee[_address] = state;
    }

    function bulkExemptFee(address[] memory accounts, bool state) external onlyOwner {
        for (uint256 i = 0; i < accounts.length; i++) {
            exemptFee[accounts[i]] = state;
        }
    }

    function rescueETH(uint256 weiAmount) external onlyOwner {
        payable(msg.sender).transfer(weiAmount);
    }

    function rescueIERC20(address tokenAdd, uint256 amount) external onlyOwner {
        IERC20(tokenAdd).transfer(msg.sender, amount);
    }

    // fallbacks
    receive() external payable {}
}