EthFiddle - Solidity IDE in the Browser. Powered By Loom Network

// File: contracts/swap/interfaces/IFluxSwapCallee.sol

//solhint-disable-next-line compiler-version
pragma solidity >=0.5.0;

interface IFluxSwapCallee {
    function fluxSwapCall(
        address sender,
        uint256 amount0,
        uint256 amount1,
        bytes calldata data
    ) external;
}

// File: contracts/swap/interfaces/IERC20.sol

//solhint-disable-next-line compiler-version
pragma solidity >=0.5.0;

interface IERC20 {
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
    event Transfer(address indexed from, address indexed to, uint256 value);

function name() external view returns (string memory);

function symbol() external view returns (string memory);

function decimals() external view returns (uint8);

function totalSupply() external view returns (uint256);

function balanceOf(address owner) external view returns (uint256);

function allowance(address owner, address spender)
        external
        view
        returns (uint256);

function approve(address spender, uint256 value) external returns (bool);

function transfer(address to, uint256 value) external returns (bool);

function transferFrom(
        address from,
        address to,
        uint256 value
    ) external returns (bool);
}

// File: contracts/swap/libraries/UQ112x112.sol

pragma solidity ^0.8.4;

// a library for handling binary fixed point numbers (https://en.wikipedia.org/wiki/Q_(number_format))

// range: [0, 2**112 - 1]
// resolution: 1 / 2**112

library UQ112x112 {
    //solhint-disable-next-line state-visibility
    uint224 constant Q112 = 2**112;

// encode a uint112 as a UQ112x112
    function encode(uint112 y) internal pure returns (uint224 z) {
        z = uint224(y) * Q112; // never overflows
    }

// divide a UQ112x112 by a uint112, returning a UQ112x112
    function uqdiv(uint224 x, uint112 y) internal pure returns (uint224 z) {
        z = x / uint224(y);
    }
}

// File: contracts/swap/libraries/Math.sol

pragma solidity ^0.8.4;

// a library for performing various math operations

library Math {
    function min(uint256 x, uint256 y) internal pure returns (uint256 z) {
        z = x < y ? x : y;
    }

// babylonian method (https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Babylonian_method)
    function sqrt(uint256 y) internal pure returns (uint256 z) {
        if (y > 3) {
            z = y;
            uint256 x = y / 2 + 1;
            while (x < z) {
                z = x;
                x = (y / x + x) / 2;
            }
        } else if (y != 0) {
            z = 1;
        }
    }
}

// File: contracts/swap/interfaces/IFluxSwapERC20.sol

//solhint-disable-next-line compiler-version
pragma solidity >=0.5.0;

//solhint-disable func-name-mixedcase
interface IFluxSwapERC20 {
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
    event Transfer(address indexed from, address indexed to, uint256 value);

function name() external pure returns (string memory);

function symbol() external pure returns (string memory);

function decimals() external pure returns (uint8);

function totalSupply() external view returns (uint256);

function balanceOf(address owner) external view returns (uint256);

function allowance(address owner, address spender)
        external
        view
        returns (uint256);

function approve(address spender, uint256 value) external returns (bool);

function transfer(address to, uint256 value) external returns (bool);

function transferFrom(
        address from,
        address to,
        uint256 value
    ) external returns (bool);

function DOMAIN_SEPARATOR() external view returns (bytes32);

function PERMIT_TYPEHASH() external pure returns (bytes32);

function nonces(address owner) external view returns (uint256);

function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;
}

// File: contracts/swap/FluxSwapERC20.sol

pragma solidity ^0.8.4;

//solhint-disable var-name-mixedcase
//solhint-disable reason-string
//solhint-disable const-name-snakecase

contract FluxSwapERC20 is IFluxSwapERC20 {
    string public constant override name = "FLUX-LP";
    string public constant override symbol = "FSLP";
    uint8 public constant override decimals = 18;
    uint256 public override totalSupply;
    mapping(address => uint256) public override balanceOf;
    mapping(address => mapping(address => uint256)) public override allowance;

bytes32 public override DOMAIN_SEPARATOR;
    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
    bytes32 public constant override PERMIT_TYPEHASH =
        0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;
    mapping(address => uint256) public override nonces;

constructor() {
        DOMAIN_SEPARATOR = keccak256(
            abi.encode(
                keccak256(
                    "EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
                ),
                keccak256(bytes(name)),
                keccak256(bytes("1")),
                block.chainid,
                address(this)
            )
        );
    }

function _mint(address to, uint256 value) internal {
        totalSupply += value;
        balanceOf[to] += value;
        emit Transfer(address(0), to, value);
    }

function _burn(address from, uint256 value) internal {
        balanceOf[from] -= value;
        totalSupply -= value;
        emit Transfer(from, address(0), value);
    }

function _approve(
        address owner,
        address spender,
        uint256 value
    ) private {
        allowance[owner][spender] = value;
        emit Approval(owner, spender, value);
    }

function _transfer(
        address from,
        address to,
        uint256 value
    ) private {
        balanceOf[from] -= value;
        balanceOf[to] += value;
        emit Transfer(from, to, value);
    }

function approve(address spender, uint256 value)
        external
        override
        returns (bool)
    {
        _approve(msg.sender, spender, value);
        return true;
    }

function transfer(address to, uint256 value)
        external
        override
        returns (bool)
    {
        _transfer(msg.sender, to, value);
        return true;
    }

function transferFrom(
        address from,
        address to,
        uint256 value
    ) external override returns (bool) {
        if (allowance[from][msg.sender] != type(uint256).max) {
            allowance[from][msg.sender] -= value;
        }
        _transfer(from, to, value);
        return true;
    }

function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external override {
        //solhint-disable-next-line not-rely-on-time
        require(deadline >= block.timestamp, "FluxSwapERC20: EXPIRED");
        bytes32 digest = keccak256(
            abi.encodePacked(
                "\x19\x01",
                DOMAIN_SEPARATOR,
                keccak256(
                    abi.encode(
                        PERMIT_TYPEHASH,
                        owner,
                        spender,
                        value,
                        nonces[owner]++,
                        deadline
                    )
                )
            )
        );
        address recoveredAddress = ecrecover(digest, v, r, s);
        require(
            recoveredAddress != address(0) && recoveredAddress == owner,
            "FluxSwapERC20: INVALID_SIGNATURE"
        );
        _approve(owner, spender, value);
    }
}

// File: contracts/swap/interfaces/IFluxSwapPair.sol

//solhint-disable-next-line compiler-version
pragma solidity >=0.5.0;

//solhint-disable func-name-mixedcase

interface IFluxSwapPair is IFluxSwapERC20 {
    event Mint(address indexed sender, uint256 amount0, uint256 amount1);
    event Burn(
        address indexed sender,
        uint256 amount0,
        uint256 amount1,
        address indexed to
    );
    event Swap(
        address indexed sender,
        uint256 amount0In,
        uint256 amount1In,
        uint256 amount0Out,
        uint256 amount1Out,
        address indexed to
    );
    event Sync(uint112 reserve0, uint112 reserve1);

function MINIMUM_LIQUIDITY() external pure returns (uint256);

function factory() external view returns (address);

function token0() external view returns (address);

function token1() external view returns (address);

function getReserves()
        external
        view
        returns (
            uint112 reserve0,
            uint112 reserve1,
            uint32 blockTimestampLast
        );

function price0CumulativeLast() external view returns (uint256);

function price1CumulativeLast() external view returns (uint256);

function kLast() external view returns (uint256);

function mint(address to) external returns (uint256 liquidity);

function burn(address to)
        external
        returns (uint256 amount0, uint256 amount1);

function swap(
        uint256 amount0Out,
        uint256 amount1Out,
        address to,
        bytes calldata data
    ) external;

function skim(address to) external;

function sync() external;

function initialize(address, address) external;
}

// File: contracts/swap/interfaces/IFluxSwapFactory.sol

//solhint-disable-next-line compiler-version
pragma solidity >=0.5.0;

interface IFluxSwapFactory {
    event PairCreated(
        address indexed token0,
        address indexed token1,
        address pair,
        uint256
    );

function feeTo() external view returns (address);

function feeToSetter() external view returns (address);

function getPair(address tokenA, address tokenB)
        external
        view
        returns (address pair);

function allPairs(uint256) external view returns (address pair);

function allPairsLength() external view returns (uint256);

function createPair(address tokenA, address tokenB)
        external
        returns (address pair);

function setFeeTo(address) external;

function setFeeToSetter(address) external;
}

// File: contracts/swap/FluxSwapPair.sol

pragma solidity ^0.8.0;

//solhint-disable func-name-mixedcase
//solhint-disable avoid-low-level-calls
//solhint-disable reason-string
//solhint-disable not-rely-on-time

contract FluxSwapPair is IFluxSwapPair, FluxSwapERC20 {
    using UQ112x112 for uint224;

uint256 public constant override MINIMUM_LIQUIDITY = 10**3;

address public override factory;
    address public override token0;
    address public override token1;

uint112 private reserve0; // uses single storage slot, accessible via getReserves
    uint112 private reserve1; // uses single storage slot, accessible via getReserves
    uint32 private blockTimestampLast; // uses single storage slot, accessible via getReserves

uint256 public override price0CumulativeLast;
    uint256 public override price1CumulativeLast;
    uint256 public override kLast; // reserve0 * reserve1, as of immediately after the most recent liquidity event

uint256 private unlocked = 1;
    modifier lock() {
        require(unlocked == 1, "UniswapV2Pair: LOCKED");
        unlocked = 0;
        _;
        unlocked = 1;
    }

function getReserves()
        public
        view
        returns (
            uint112 _reserve0,
            uint112 _reserve1,
            uint32 _blockTimestampLast
        )
    {
        _reserve0 = reserve0;
        _reserve1 = reserve1;
        _blockTimestampLast = blockTimestampLast;
    }

function _safeTransfer(
        address token,
        address to,
        uint256 value
    ) private {
        (bool success, bytes memory data) = token.call(
            abi.encodeWithSelector(IERC20.transfer.selector, to, value)
        );
        require(
            success && (data.length == 0 || abi.decode(data, (bool))),
            "FluxSwapPair: TRANSFER_FAILED"
        );
    }

constructor() {
        factory = msg.sender;
    }

// called once by the factory at time of deployment
    function initialize(address _token0, address _token1) external override {
        require(msg.sender == factory, "FluxSwapPair: FORBIDDEN"); // sufficient check
        token0 = _token0;
        token1 = _token1;
    }

// update reserves and, on the first call per block, price accumulators
    function _update(
        uint256 balance0,
        uint256 balance1,
        uint112 _reserve0,
        uint112 _reserve1
    ) private {
        require(
            balance0 <= type(uint112).max && balance1 <= type(uint112).max,
            "FluxSwapPair: OVERFLOW"
        );
        uint32 blockTimestamp = uint32(block.timestamp % 2**32);
        unchecked {
            uint32 timeElapsed = blockTimestamp - blockTimestampLast; // overflow is desired
            if (timeElapsed > 0 && _reserve0 != 0 && _reserve1 != 0) {
                // * never overflows, and + overflow is desired
                price0CumulativeLast +=
                    uint256(UQ112x112.encode(_reserve1).uqdiv(_reserve0)) *
                    timeElapsed;
                price1CumulativeLast +=
                    uint256(UQ112x112.encode(_reserve0).uqdiv(_reserve1)) *
                    timeElapsed;
            }
        }
        reserve0 = uint112(balance0);
        reserve1 = uint112(balance1);
        blockTimestampLast = blockTimestamp;
        emit Sync(reserve0, reserve1);
    }

// if fee is on, mint liquidity equivalent to 1/6th of the growth in sqrt(k)
    function _mintFee(uint112 _reserve0, uint112 _reserve1)
        private
        returns (bool feeOn)
    {
        address feeTo = IFluxSwapFactory(factory).feeTo();
        feeOn = feeTo != address(0);
        uint256 _kLast = kLast; // gas savings
        if (feeOn) {
            if (_kLast != 0) {
                uint256 rootK = Math.sqrt(uint256(_reserve0) * _reserve1);
                uint256 rootKLast = Math.sqrt(_kLast);
                if (rootK > rootKLast) {
                    uint256 numerator = totalSupply * (rootK - rootKLast);
                    uint256 denominator = rootK * 5 + rootKLast;
                    uint256 liquidity = numerator / denominator;
                    if (liquidity > 0) _mint(feeTo, liquidity);
                }
            }
        } else if (_kLast != 0) {
            kLast = 0;
        }
    }

// this low-level function should be called from a contract which performs important safety checks
    function mint(address to)
        external
        override
        lock
        returns (uint256 liquidity)
    {
        (uint112 _reserve0, uint112 _reserve1, ) = getReserves(); // gas savings
        uint256 balance0 = IERC20(token0).balanceOf(address(this));
        uint256 balance1 = IERC20(token1).balanceOf(address(this));
        uint256 amount0 = balance0 - _reserve0;
        uint256 amount1 = balance1 - _reserve1;

bool feeOn = _mintFee(_reserve0, _reserve1);
        uint256 _totalSupply = totalSupply; // gas savings, must be defined here since totalSupply can update in _mintFee
        if (_totalSupply == 0) {
            liquidity = Math.sqrt(amount0 * amount1) - MINIMUM_LIQUIDITY;
            _mint(address(0), MINIMUM_LIQUIDITY); // permanently lock the first MINIMUM_LIQUIDITY tokens
        } else {
            liquidity = Math.min(
                (amount0 * _totalSupply) / _reserve0,
                (amount1 * _totalSupply) / _reserve1
            );
        }
        require(liquidity > 0, "FluxSwapPair: INSUFFICIENT_LIQUIDITY_MINTED");
        _mint(to, liquidity);

_update(balance0, balance1, _reserve0, _reserve1);
        if (feeOn) kLast = uint256(reserve0) * reserve1; // reserve0 and reserve1 are up-to-date
        emit Mint(msg.sender, amount0, amount1);
    }

// this low-level function should be called from a contract which performs important safety checks
    function burn(address to)
        external
        override
        lock
        returns (uint256 amount0, uint256 amount1)
    {
        (uint112 _reserve0, uint112 _reserve1, ) = getReserves(); // gas savings
        address _token0 = token0; // gas savings
        address _token1 = token1; // gas savings
        uint256 balance0 = IERC20(_token0).balanceOf(address(this));
        uint256 balance1 = IERC20(_token1).balanceOf(address(this));
        uint256 liquidity = balanceOf[address(this)];

bool feeOn = _mintFee(_reserve0, _reserve1);
        uint256 _totalSupply = totalSupply; // gas savings, must be defined here since totalSupply can update in _mintFee
        amount0 = (liquidity * balance0) / _totalSupply; // using balances ensures pro-rata distribution
        amount1 = (liquidity * balance1) / _totalSupply; // using balances ensures pro-rata distribution
        require(
            amount0 > 0 && amount1 > 0,
            "FluxSwapPair: INSUFFICIENT_LIQUIDITY_BURNED"
        );
        _burn(address(this), liquidity);
        _safeTransfer(_token0, to, amount0);
        _safeTransfer(_token1, to, amount1);
        balance0 = IERC20(_token0).balanceOf(address(this));
        balance1 = IERC20(_token1).balanceOf(address(this));

_update(balance0, balance1, _reserve0, _reserve1);
        if (feeOn) kLast = uint256(reserve0) * reserve1; // reserve0 and reserve1 are up-to-date
        emit Burn(msg.sender, amount0, amount1, to);
    }

// this low-level function should be called from a contract which performs important safety checks
    function swap(
        uint256 amount0Out,
        uint256 amount1Out,
        address to,
        bytes calldata data
    ) external override lock {
        require(
            amount0Out > 0 || amount1Out > 0,
            "FluxSwapPair: INSUFFICIENT_OUTPUT_AMOUNT"
        );
        (uint112 _reserve0, uint112 _reserve1, ) = getReserves(); // gas savings
        require(
            amount0Out < _reserve0 && amount1Out < _reserve1,
            "FluxSwapPair: INSUFFICIENT_LIQUIDITY"
        );

uint256 balance0;
        uint256 balance1;
        {
            // scope for _token{0,1}, avoids stack too deep errors
            address _token0 = token0;
            address _token1 = token1;
            require(to != _token0 && to != _token1, "FluxSwapPair: INVALID_TO");
            if (amount0Out > 0) _safeTransfer(_token0, to, amount0Out); // optimistically transfer tokens
            if (amount1Out > 0) _safeTransfer(_token1, to, amount1Out); // optimistically transfer tokens
            if (data.length > 0)
                IFluxSwapCallee(to).fluxSwapCall(
                    msg.sender,
                    amount0Out,
                    amount1Out,
                    data
                );
            balance0 = IERC20(_token0).balanceOf(address(this));
            balance1 = IERC20(_token1).balanceOf(address(this));
        }
        uint256 amount0In = balance0 > _reserve0 - amount0Out
            ? balance0 - (_reserve0 - amount0Out)
            : 0;
        uint256 amount1In = balance1 > _reserve1 - amount1Out
            ? balance1 - (_reserve1 - amount1Out)
            : 0;
        require(
            amount0In > 0 || amount1In > 0,
            "FluxSwapPair: INSUFFICIENT_INPUT_AMOUNT"
        );
        {
            // scope for reserve{0,1}Adjusted, avoids stack too deep errors
            uint256 balance0Adjusted = balance0 * 1000 - amount0In * 3;
            uint256 balance1Adjusted = balance1 * 1000 - amount1In * 3;
            require(
                balance0Adjusted * balance1Adjusted >=
                    uint256(_reserve0) * _reserve1 * 1e6,
                "FluxSwapPair: K"
            );
        }

_update(balance0, balance1, _reserve0, _reserve1);
        emit Swap(msg.sender, amount0In, amount1In, amount0Out, amount1Out, to);
    }

// force balances to match reserves
    function skim(address to) external override lock {
        address _token0 = token0; // gas savings
        address _token1 = token1; // gas savings
        _safeTransfer(
            _token0,
            to,
            IERC20(_token0).balanceOf(address(this)) - reserve0
        );
        _safeTransfer(
            _token1,
            to,
            IERC20(_token1).balanceOf(address(this)) - reserve1
        );
    }

// force reserves to match balances
    function sync() external override lock {
        _update(
            IERC20(token0).balanceOf(address(this)),
            IERC20(token1).balanceOf(address(this)),
            reserve0,
            reserve1
        );
    }
}

// File: contracts/swap/FluxSwapFactory.sol

pragma solidity ^0.8.4;

contract FluxSwapFactory is IFluxSwapFactory {
    bytes32 public constant PAIR_HASH =
        keccak256(type(FluxSwapPair).creationCode);

address public override feeTo;
    address public override feeToSetter;

mapping(address => mapping(address => address)) public override getPair;
    address[] public override allPairs;

constructor(address _feeToSetter) {
        feeToSetter = _feeToSetter;
    }

function allPairsLength() external view override returns (uint256) {
        return allPairs.length;
    }

function createPair(address tokenA, address tokenB)
        external
        override
        returns (address pair)
    {
        require(tokenA != tokenB, "FluxSwapFactory: IDENTICAL_ADDRESSES");
        (address token0, address token1) = tokenA < tokenB
            ? (tokenA, tokenB)
            : (tokenB, tokenA);
        require(token0 != address(0), "FluxSwapFactory: ZERO_ADDRESS");
        require(
            getPair[token0][token1] == address(0),
            "FluxSwapFactory: PAIR_EXISTS"
        ); // single check is sufficient

pair = address(
            new FluxSwapPair{
                salt: keccak256(abi.encodePacked(token0, token1))
            }()
        );
        IFluxSwapPair(pair).initialize(token0, token1);
        getPair[token0][token1] = pair;
        getPair[token1][token0] = pair; // populate mapping in the reverse direction
        allPairs.push(pair);
        emit PairCreated(token0, token1, pair, allPairs.length);
    }

function setFeeTo(address _feeTo) external override {
        require(msg.sender == feeToSetter, "FluxSwapFactory: FORBIDDEN");
        feeTo = _feeTo;
    }

function setFeeToSetter(address _feeToSetter) external override {
        require(msg.sender == feeToSetter, "FluxSwapFactory: FORBIDDEN");
        feeToSetter = _feeToSetter;
    }
}