init

.gitignore

+node_modules
+.env
+
+# Hardhat files
+/cache
+/artifacts
+
+# TypeChain files
+/typechain
+/typechain-types
+
+# solidity-coverage files
+/coverage
+/coverage.json
+
+# Hardhat Ignition default folder for deployments against a local node
+ignition/deployments/chain-31337
+
+node_modules
+.env
+
+# Hardhat files
+/cache
+/artifacts
+
+# TypeChain files
+/typechain
+/typechain-types
+
+# solidity-coverage files
+/coverage
+/coverage.json
+
+# Hardhat Ignition default folder for deployments against a local node
+ignition/deployments/chain-31337
+
+ignition/deployments/chain-17000

README.md

+# Sample Hardhat Project
+
+This project demonstrates a basic Hardhat use case. It comes with a sample contract, a test for that contract, and a Hardhat Ignition module that deploys that contract.
+
+Try running some of the following tasks:
+
+```shell
+npx hardhat help
+npx hardhat test
+REPORT_GAS=true npx hardhat test
+npx hardhat node
+```
+
+
+npx hardhat ignition deploy ./ignition/modules/v2dex.js --network holesky
\ No newline at end of file

contracts/v2-core/UniswapV2ERC20.sol

+pragma solidity =0.5.16;
+
+import './interfaces/IUniswapV2ERC20.sol';
+import './libraries/SafeMath.sol';
+
+contract UniswapV2ERC20 is IUniswapV2ERC20 {
+    using SafeMath for uint;
+
+    string public constant name = 'Uniswap V2';
+    string public constant symbol = 'UNI-V2';
+    uint8 public constant decimals = 18;
+    uint  public totalSupply;
+    mapping(address => uint) public balanceOf;
+    mapping(address => mapping(address => uint)) public allowance;
+
+    bytes32 public DOMAIN_SEPARATOR;
+    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
+    bytes32 public constant PERMIT_TYPEHASH = 0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;
+    mapping(address => uint) public nonces;
+
+    event Approval(address indexed owner, address indexed spender, uint value);
+    event Transfer(address indexed from, address indexed to, uint value);
+
+    constructor() public {
+        uint chainId;
+        assembly {
+            chainId := chainid
+        }
+        DOMAIN_SEPARATOR = keccak256(
+            abi.encode(
+                keccak256('EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)'),
+                keccak256(bytes(name)),
+                keccak256(bytes('1')),
+                chainId,
+                address(this)
+            )
+        );
+    }
+
+    function _mint(address to, uint value) internal {
+        totalSupply = totalSupply.add(value);
+        balanceOf[to] = balanceOf[to].add(value);
+        emit Transfer(address(0), to, value);
+    }
+
+    function _burn(address from, uint value) internal {
+        balanceOf[from] = balanceOf[from].sub(value);
+        totalSupply = totalSupply.sub(value);
+        emit Transfer(from, address(0), value);
+    }
+
+    function _approve(address owner, address spender, uint value) private {
+        allowance[owner][spender] = value;
+        emit Approval(owner, spender, value);
+    }
+
+    function _transfer(address from, address to, uint value) private {
+        balanceOf[from] = balanceOf[from].sub(value);
+        balanceOf[to] = balanceOf[to].add(value);
+        emit Transfer(from, to, value);
+    }
+
+    function approve(address spender, uint value) external returns (bool) {
+        _approve(msg.sender, spender, value);
+        return true;
+    }
+
+    function transfer(address to, uint value) external returns (bool) {
+        _transfer(msg.sender, to, value);
+        return true;
+    }
+
+    function transferFrom(address from, address to, uint value) external returns (bool) {
+        if (allowance[from][msg.sender] != uint(-1)) {
+            allowance[from][msg.sender] = allowance[from][msg.sender].sub(value);
+        }
+        _transfer(from, to, value);
+        return true;
+    }
+
+    function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external {
+        require(deadline >= block.timestamp, 'UniswapV2: 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, 'UniswapV2: INVALID_SIGNATURE');
+        _approve(owner, spender, value);
+    }
+}

contracts/v2-core/UniswapV2Factory.sol

+pragma solidity =0.5.16;
+
+import './interfaces/IUniswapV2Factory.sol';
+import './UniswapV2Pair.sol';
+
+contract UniswapV2Factory is IUniswapV2Factory {
+    address public feeTo;
+    address public feeToSetter;
+
+    mapping(address => mapping(address => address)) public getPair;
+    address[] public allPairs;
+
+    event PairCreated(address indexed token0, address indexed token1, address pair, uint);
+
+    constructor(address _feeToSetter) public {
+        feeToSetter = _feeToSetter;
+    }
+
+    function allPairsLength() external view returns (uint) {
+        return allPairs.length;
+    }
+
+    function createPair(address tokenA, address tokenB) external returns (address pair) {
+        require(tokenA != tokenB, 'UniswapV2: IDENTICAL_ADDRESSES');
+        (address token0, address token1) = tokenA < tokenB ? (tokenA, tokenB) : (tokenB, tokenA);
+        require(token0 != address(0), 'UniswapV2: ZERO_ADDRESS');
+        require(getPair[token0][token1] == address(0), 'UniswapV2: PAIR_EXISTS'); // single check is sufficient
+        bytes memory bytecode = type(UniswapV2Pair).creationCode;
+        bytes32 salt = keccak256(abi.encodePacked(token0, token1));
+        assembly {
+            pair := create2(0, add(bytecode, 32), mload(bytecode), salt)
+        }
+        IUniswapV2Pair(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 {
+        require(msg.sender == feeToSetter, 'UniswapV2: FORBIDDEN');
+        feeTo = _feeTo;
+    }
+
+    function setFeeToSetter(address _feeToSetter) external {
+        require(msg.sender == feeToSetter, 'UniswapV2: FORBIDDEN');
+        feeToSetter = _feeToSetter;
+    }
+}

contracts/v2-core/UniswapV2Pair.sol

+pragma solidity =0.5.16;
+
+import './interfaces/IUniswapV2Pair.sol';
+import './UniswapV2ERC20.sol';
+import './libraries/Math.sol';
+import './libraries/UQ112x112.sol';
+import './interfaces/IERC20.sol';
+import './interfaces/IUniswapV2Factory.sol';
+import './interfaces/IUniswapV2Callee.sol';
+
+contract UniswapV2Pair is IUniswapV2Pair, UniswapV2ERC20 {
+    using SafeMath  for uint;
+    using UQ112x112 for uint224;
+
+    uint public constant MINIMUM_LIQUIDITY = 10**3;
+    bytes4 private constant SELECTOR = bytes4(keccak256(bytes('transfer(address,uint256)')));
+
+    address public factory;
+    address public token0;
+    address public 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
+
+    uint public price0CumulativeLast;
+    uint public price1CumulativeLast;
+    uint public kLast; // reserve0 * reserve1, as of immediately after the most recent liquidity event
+
+    uint private unlocked = 1;
+    modifier lock() {
+        require(unlocked == 1, 'UniswapV2: 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, uint value) private {
+        (bool success, bytes memory data) = token.call(abi.encodeWithSelector(SELECTOR, to, value));
+        require(success && (data.length == 0 || abi.decode(data, (bool))), 'UniswapV2: TRANSFER_FAILED');
+    }
+
+    event Mint(address indexed sender, uint amount0, uint amount1);
+    event Burn(address indexed sender, uint amount0, uint amount1, address indexed to);
+    event Swap(
+        address indexed sender,
+        uint amount0In,
+        uint amount1In,
+        uint amount0Out,
+        uint amount1Out,
+        address indexed to
+    );
+    event Sync(uint112 reserve0, uint112 reserve1);
+
+    constructor() public {
+        factory = msg.sender;
+    }
+
+    // called once by the factory at time of deployment
+    function initialize(address _token0, address _token1) external {
+        require(msg.sender == factory, 'UniswapV2: FORBIDDEN'); // sufficient check
+        token0 = _token0;
+        token1 = _token1;
+    }
+
+    // update reserves and, on the first call per block, price accumulators
+    function _update(uint balance0, uint balance1, uint112 _reserve0, uint112 _reserve1) private {
+        require(balance0 <= uint112(-1) && balance1 <= uint112(-1), 'UniswapV2: OVERFLOW');
+        uint32 blockTimestamp = uint32(block.timestamp % 2**32);
+        uint32 timeElapsed = blockTimestamp - blockTimestampLast; // overflow is desired
+        if (timeElapsed > 0 && _reserve0 != 0 && _reserve1 != 0) {
+            // * never overflows, and + overflow is desired
+            price0CumulativeLast += uint(UQ112x112.encode(_reserve1).uqdiv(_reserve0)) * timeElapsed;
+            price1CumulativeLast += uint(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 = IUniswapV2Factory(factory).feeTo();
+        feeOn = feeTo != address(0);
+        uint _kLast = kLast; // gas savings
+        if (feeOn) {
+            if (_kLast != 0) {
+                uint rootK = Math.sqrt(uint(_reserve0).mul(_reserve1));
+                uint rootKLast = Math.sqrt(_kLast);
+                if (rootK > rootKLast) {
+                    uint numerator = totalSupply.mul(rootK.sub(rootKLast));
+                    uint denominator = rootK.mul(5).add(rootKLast);
+                    uint 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 lock returns (uint liquidity) {
+        (uint112 _reserve0, uint112 _reserve1,) = getReserves(); // gas savings
+        uint balance0 = IERC20(token0).balanceOf(address(this));
+        uint balance1 = IERC20(token1).balanceOf(address(this));
+        uint amount0 = balance0.sub(_reserve0);
+        uint amount1 = balance1.sub(_reserve1);
+
+        bool feeOn = _mintFee(_reserve0, _reserve1);
+        uint _totalSupply = totalSupply; // gas savings, must be defined here since totalSupply can update in _mintFee
+        if (_totalSupply == 0) {
+            liquidity = Math.sqrt(amount0.mul(amount1)).sub(MINIMUM_LIQUIDITY);
+           _mint(address(0), MINIMUM_LIQUIDITY); // permanently lock the first MINIMUM_LIQUIDITY tokens
+        } else {
+            liquidity = Math.min(amount0.mul(_totalSupply) / _reserve0, amount1.mul(_totalSupply) / _reserve1);
+        }
+        require(liquidity > 0, 'UniswapV2: INSUFFICIENT_LIQUIDITY_MINTED');
+        _mint(to, liquidity);
+
+        _update(balance0, balance1, _reserve0, _reserve1);
+        if (feeOn) kLast = uint(reserve0).mul(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 lock returns (uint amount0, uint amount1) {
+        (uint112 _reserve0, uint112 _reserve1,) = getReserves(); // gas savings
+        address _token0 = token0;                                // gas savings
+        address _token1 = token1;                                // gas savings
+        uint balance0 = IERC20(_token0).balanceOf(address(this));
+        uint balance1 = IERC20(_token1).balanceOf(address(this));
+        uint liquidity = balanceOf[address(this)];
+
+        bool feeOn = _mintFee(_reserve0, _reserve1);
+        uint _totalSupply = totalSupply; // gas savings, must be defined here since totalSupply can update in _mintFee
+        amount0 = liquidity.mul(balance0) / _totalSupply; // using balances ensures pro-rata distribution
+        amount1 = liquidity.mul(balance1) / _totalSupply; // using balances ensures pro-rata distribution
+        require(amount0 > 0 && amount1 > 0, 'UniswapV2: 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 = uint(reserve0).mul(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(uint amount0Out, uint amount1Out, address to, bytes calldata data) external lock {
+        require(amount0Out > 0 || amount1Out > 0, 'UniswapV2: INSUFFICIENT_OUTPUT_AMOUNT');
+        (uint112 _reserve0, uint112 _reserve1,) = getReserves(); // gas savings
+        require(amount0Out < _reserve0 && amount1Out < _reserve1, 'UniswapV2: INSUFFICIENT_LIQUIDITY');
+
+        uint balance0;
+        uint balance1;
+        { // scope for _token{0,1}, avoids stack too deep errors
+        address _token0 = token0;
+        address _token1 = token1;
+        require(to != _token0 && to != _token1, 'UniswapV2: 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) IUniswapV2Callee(to).uniswapV2Call(msg.sender, amount0Out, amount1Out, data);
+        balance0 = IERC20(_token0).balanceOf(address(this));
+        balance1 = IERC20(_token1).balanceOf(address(this));
+        }
+        uint amount0In = balance0 > _reserve0 - amount0Out ? balance0 - (_reserve0 - amount0Out) : 0;
+        uint amount1In = balance1 > _reserve1 - amount1Out ? balance1 - (_reserve1 - amount1Out) : 0;
+        require(amount0In > 0 || amount1In > 0, 'UniswapV2: INSUFFICIENT_INPUT_AMOUNT');
+        { // scope for reserve{0,1}Adjusted, avoids stack too deep errors
+        uint balance0Adjusted = balance0.mul(1000).sub(amount0In.mul(3));
+        uint balance1Adjusted = balance1.mul(1000).sub(amount1In.mul(3));
+        require(balance0Adjusted.mul(balance1Adjusted) >= uint(_reserve0).mul(_reserve1).mul(1000**2), 'UniswapV2: 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 lock {
+        address _token0 = token0; // gas savings
+        address _token1 = token1; // gas savings
+        _safeTransfer(_token0, to, IERC20(_token0).balanceOf(address(this)).sub(reserve0));
+        _safeTransfer(_token1, to, IERC20(_token1).balanceOf(address(this)).sub(reserve1));
+    }
+
+    // force reserves to match balances
+    function sync() external lock {
+        _update(IERC20(token0).balanceOf(address(this)), IERC20(token1).balanceOf(address(this)), reserve0, reserve1);
+    }
+}

contracts/v2-core/interfaces/IERC20.sol

+pragma solidity >=0.5.0;
+
+interface IERC20 {
+    event Approval(address indexed owner, address indexed spender, uint value);
+    event Transfer(address indexed from, address indexed to, uint 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 (uint);
+    function balanceOf(address owner) external view returns (uint);
+    function allowance(address owner, address spender) external view returns (uint);
+
+    function approve(address spender, uint value) external returns (bool);
+    function transfer(address to, uint value) external returns (bool);
+    function transferFrom(address from, address to, uint value) external returns (bool);
+}

contracts/v2-core/interfaces/IUniswapV2Callee.sol

+pragma solidity >=0.5.0;
+
+interface IUniswapV2Callee {
+    function uniswapV2Call(address sender, uint amount0, uint amount1, bytes calldata data) external;
+}

contracts/v2-core/interfaces/IUniswapV2ERC20.sol

+pragma solidity >=0.5.0;
+
+interface IUniswapV2ERC20 {
+    event Approval(address indexed owner, address indexed spender, uint value);
+    event Transfer(address indexed from, address indexed to, uint 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 (uint);
+    function balanceOf(address owner) external view returns (uint);
+    function allowance(address owner, address spender) external view returns (uint);
+
+    function approve(address spender, uint value) external returns (bool);
+    function transfer(address to, uint value) external returns (bool);
+    function transferFrom(address from, address to, uint 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 (uint);
+
+    function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external;
+}

contracts/v2-core/interfaces/IUniswapV2Factory.sol

+pragma solidity >=0.5.0;
+
+interface IUniswapV2Factory {
+    event PairCreated(address indexed token0, address indexed token1, address pair, uint);
+
+    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(uint) external view returns (address pair);
+    function allPairsLength() external view returns (uint);
+
+    function createPair(address tokenA, address tokenB) external returns (address pair);
+
+    function setFeeTo(address) external;
+    function setFeeToSetter(address) external;
+}

contracts/v2-core/interfaces/IUniswapV2Pair.sol

+pragma solidity >=0.5.0;
+
+interface IUniswapV2Pair {
+    event Approval(address indexed owner, address indexed spender, uint value);
+    event Transfer(address indexed from, address indexed to, uint 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 (uint);
+    function balanceOf(address owner) external view returns (uint);
+    function allowance(address owner, address spender) external view returns (uint);
+
+    function approve(address spender, uint value) external returns (bool);
+    function transfer(address to, uint value) external returns (bool);
+    function transferFrom(address from, address to, uint 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 (uint);
+
+    function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external;
+
+    event Mint(address indexed sender, uint amount0, uint amount1);
+    event Burn(address indexed sender, uint amount0, uint amount1, address indexed to);
+    event Swap(
+        address indexed sender,
+        uint amount0In,
+        uint amount1In,
+        uint amount0Out,
+        uint amount1Out,
+        address indexed to
+    );
+    event Sync(uint112 reserve0, uint112 reserve1);
+
+    function MINIMUM_LIQUIDITY() external pure returns (uint);
+    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 (uint);
+    function price1CumulativeLast() external view returns (uint);
+    function kLast() external view returns (uint);
+
+    function mint(address to) external returns (uint liquidity);
+    function burn(address to) external returns (uint amount0, uint amount1);
+    function swap(uint amount0Out, uint amount1Out, address to, bytes calldata data) external;
+    function skim(address to) external;
+    function sync() external;
+
+    function initialize(address, address) external;
+}

contracts/v2-core/libraries/Math.sol

+pragma solidity =0.5.16;
+
+// a library for performing various math operations
+
+library Math {
+    function min(uint x, uint y) internal pure returns (uint z) {
+        z = x < y ? x : y;
+    }
+
+    // babylonian method (https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Babylonian_method)
+    function sqrt(uint y) internal pure returns (uint z) {
+        if (y > 3) {
+            z = y;
+            uint x = y / 2 + 1;
+            while (x < z) {
+                z = x;
+                x = (y / x + x) / 2;
+            }
+        } else if (y != 0) {
+            z = 1;
+        }
+    }
+}

contracts/v2-core/libraries/SafeMath.sol

+pragma solidity =0.5.16;
+
+// a library for performing overflow-safe math, courtesy of DappHub (https://github.com/dapphub/ds-math)
+
+library SafeMath {
+    function add(uint x, uint y) internal pure returns (uint z) {
+        require((z = x + y) >= x, 'ds-math-add-overflow');
+    }
+
+    function sub(uint x, uint y) internal pure returns (uint z) {
+        require((z = x - y) <= x, 'ds-math-sub-underflow');
+    }
+
+    function mul(uint x, uint y) internal pure returns (uint z) {
+        require(y == 0 || (z = x * y) / y == x, 'ds-math-mul-overflow');
+    }
+}

contracts/v2-core/libraries/UQ112x112.sol

+pragma solidity =0.5.16;
+
+// 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 {
+    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);
+    }
+}

contracts/v2-core/test/ERC20.sol

+pragma solidity =0.5.16;
+
+import '../UniswapV2ERC20.sol';
+
+contract ERC20 is UniswapV2ERC20 {
+    constructor(uint _totalSupply) public {
+        _mint(msg.sender, _totalSupply);
+    }
+}

contracts/v2-periphery/UniswapV2Migrator.sol

+pragma solidity =0.6.6;
+
+import '@uniswap/lib/contracts/libraries/TransferHelper.sol';
+
+import './interfaces/IUniswapV2Migrator.sol';
+import './interfaces/V1/IUniswapV1Factory.sol';
+import './interfaces/V1/IUniswapV1Exchange.sol';
+import './interfaces/IUniswapV2Router01.sol';
+import './interfaces/IERC20.sol';
+
+contract UniswapV2Migrator is IUniswapV2Migrator {
+    IUniswapV1Factory immutable factoryV1;
+    IUniswapV2Router01 immutable router;
+
+    constructor(address _factoryV1, address _router) public {
+        factoryV1 = IUniswapV1Factory(_factoryV1);
+        router = IUniswapV2Router01(_router);
+    }
+
+    // needs to accept ETH from any v1 exchange and the router. ideally this could be enforced, as in the router,
+    // but it's not possible because it requires a call to the v1 factory, which takes too much gas
+    receive() external payable {}
+
+    function migrate(address token, uint amountTokenMin, uint amountETHMin, address to, uint deadline)
+        external
+        override
+    {
+        IUniswapV1Exchange exchangeV1 = IUniswapV1Exchange(factoryV1.getExchange(token));
+        uint liquidityV1 = exchangeV1.balanceOf(msg.sender);
+        require(exchangeV1.transferFrom(msg.sender, address(this), liquidityV1), 'TRANSFER_FROM_FAILED');
+        (uint amountETHV1, uint amountTokenV1) = exchangeV1.removeLiquidity(liquidityV1, 1, 1, uint(-1));
+        TransferHelper.safeApprove(token, address(router), amountTokenV1);
+        (uint amountTokenV2, uint amountETHV2,) = router.addLiquidityETH{value: amountETHV1}(
+            token,
+            amountTokenV1,
+            amountTokenMin,
+            amountETHMin,
+            to,
+            deadline
+        );
+        if (amountTokenV1 > amountTokenV2) {
+            TransferHelper.safeApprove(token, address(router), 0); // be a good blockchain citizen, reset allowance to 0
+            TransferHelper.safeTransfer(token, msg.sender, amountTokenV1 - amountTokenV2);
+        } else if (amountETHV1 > amountETHV2) {
+            // addLiquidityETH guarantees that all of amountETHV1 or amountTokenV1 will be used, hence this else is safe
+            TransferHelper.safeTransferETH(msg.sender, amountETHV1 - amountETHV2);
+        }
+    }
+}

contracts/v2-periphery/UniswapV2Router01.sol

+pragma solidity =0.6.6;
+
+import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Factory.sol';
+import '@uniswap/lib/contracts/libraries/TransferHelper.sol';
+
+import './libraries/UniswapV2Library.sol';
+import './interfaces/IUniswapV2Router01.sol';
+import './interfaces/IERC20.sol';
+import './interfaces/IWETH.sol';
+
+contract UniswapV2Router01 is IUniswapV2Router01 {
+    address public immutable override factory;
+    address public immutable override WETH;
+
+    modifier ensure(uint deadline) {
+        require(deadline >= block.timestamp, 'UniswapV2Router: EXPIRED');
+        _;
+    }
+
+    constructor(address _factory, address _WETH) public {
+        factory = _factory;
+        WETH = _WETH;
+    }
+
+    receive() external payable {
+        assert(msg.sender == WETH); // only accept ETH via fallback from the WETH contract
+    }
+
+    // **** ADD LIQUIDITY ****
+    function _addLiquidity(
+        address tokenA,
+        address tokenB,
+        uint amountADesired,
+        uint amountBDesired,
+        uint amountAMin,
+        uint amountBMin
+    ) private returns (uint amountA, uint amountB) {
+        // create the pair if it doesn't exist yet
+        if (IUniswapV2Factory(factory).getPair(tokenA, tokenB) == address(0)) {
+            IUniswapV2Factory(factory).createPair(tokenA, tokenB);
+        }
+        (uint reserveA, uint reserveB) = UniswapV2Library.getReserves(factory, tokenA, tokenB);
+        if (reserveA == 0 && reserveB == 0) {
+            (amountA, amountB) = (amountADesired, amountBDesired);
+        } else {
+            uint amountBOptimal = UniswapV2Library.quote(amountADesired, reserveA, reserveB);
+            if (amountBOptimal <= amountBDesired) {
+                require(amountBOptimal >= amountBMin, 'UniswapV2Router: INSUFFICIENT_B_AMOUNT');
+                (amountA, amountB) = (amountADesired, amountBOptimal);
+            } else {
+                uint amountAOptimal = UniswapV2Library.quote(amountBDesired, reserveB, reserveA);
+                assert(amountAOptimal <= amountADesired);
+                require(amountAOptimal >= amountAMin, 'UniswapV2Router: INSUFFICIENT_A_AMOUNT');
+                (amountA, amountB) = (amountAOptimal, amountBDesired);
+            }
+        }
+    }
+    function addLiquidity(
+        address tokenA,
+        address tokenB,
+        uint amountADesired,
+        uint amountBDesired,
+        uint amountAMin,
+        uint amountBMin,
+        address to,
+        uint deadline
+    ) external override ensure(deadline) returns (uint amountA, uint amountB, uint liquidity) {
+        (amountA, amountB) = _addLiquidity(tokenA, tokenB, amountADesired, amountBDesired, amountAMin, amountBMin);
+        address pair = UniswapV2Library.pairFor(factory, tokenA, tokenB);
+        TransferHelper.safeTransferFrom(tokenA, msg.sender, pair, amountA);
+        TransferHelper.safeTransferFrom(tokenB, msg.sender, pair, amountB);
+        liquidity = IUniswapV2Pair(pair).mint(to);
+    }
+    function addLiquidityETH(
+        address token,
+        uint amountTokenDesired,
+        uint amountTokenMin,
+        uint amountETHMin,
+        address to,
+        uint deadline
+    ) external override payable ensure(deadline) returns (uint amountToken, uint amountETH, uint liquidity) {
+        (amountToken, amountETH) = _addLiquidity(
+            token,
+            WETH,
+            amountTokenDesired,
+            msg.value,
+            amountTokenMin,
+            amountETHMin
+        );
+        address pair = UniswapV2Library.pairFor(factory, token, WETH);
+        TransferHelper.safeTransferFrom(token, msg.sender, pair, amountToken);
+        IWETH(WETH).deposit{value: amountETH}();
+        assert(IWETH(WETH).transfer(pair, amountETH));
+        liquidity = IUniswapV2Pair(pair).mint(to);
+        if (msg.value > amountETH) TransferHelper.safeTransferETH(msg.sender, msg.value - amountETH); // refund dust eth, if any
+    }
+
+    // **** REMOVE LIQUIDITY ****
+    function removeLiquidity(
+        address tokenA,
+        address tokenB,
+        uint liquidity,
+        uint amountAMin,
+        uint amountBMin,
+        address to,
+        uint deadline
+    ) public override ensure(deadline) returns (uint amountA, uint amountB) {
+        address pair = UniswapV2Library.pairFor(factory, tokenA, tokenB);
+        IUniswapV2Pair(pair).transferFrom(msg.sender, pair, liquidity); // send liquidity to pair
+        (uint amount0, uint amount1) = IUniswapV2Pair(pair).burn(to);
+        (address token0,) = UniswapV2Library.sortTokens(tokenA, tokenB);
+        (amountA, amountB) = tokenA == token0 ? (amount0, amount1) : (amount1, amount0);
+        require(amountA >= amountAMin, 'UniswapV2Router: INSUFFICIENT_A_AMOUNT');
+        require(amountB >= amountBMin, 'UniswapV2Router: INSUFFICIENT_B_AMOUNT');
+    }
+    function removeLiquidityETH(
+        address token,
+        uint liquidity,
+        uint amountTokenMin,
+        uint amountETHMin,
+        address to,
+        uint deadline
+    ) public override ensure(deadline) returns (uint amountToken, uint amountETH) {
+        (amountToken, amountETH) = removeLiquidity(
+            token,
+            WETH,
+            liquidity,
+            amountTokenMin,
+            amountETHMin,
+            address(this),
+            deadline
+        );
+        TransferHelper.safeTransfer(token, to, amountToken);
+        IWETH(WETH).withdraw(amountETH);
+        TransferHelper.safeTransferETH(to, amountETH);
+    }
+    function removeLiquidityWithPermit(
+        address tokenA,
+        address tokenB,
+        uint liquidity,
+        uint amountAMin,
+        uint amountBMin,
+        address to,
+        uint deadline,
+        bool approveMax, uint8 v, bytes32 r, bytes32 s
+    ) external override returns (uint amountA, uint amountB) {
+        address pair = UniswapV2Library.pairFor(factory, tokenA, tokenB);
+        uint value = approveMax ? uint(-1) : liquidity;
+        IUniswapV2Pair(pair).permit(msg.sender, address(this), value, deadline, v, r, s);
+        (amountA, amountB) = removeLiquidity(tokenA, tokenB, liquidity, amountAMin, amountBMin, to, deadline);
+    }
+    function removeLiquidityETHWithPermit(
+        address token,
+        uint liquidity,
+        uint amountTokenMin,
+        uint amountETHMin,
+        address to,
+        uint deadline,
+        bool approveMax, uint8 v, bytes32 r, bytes32 s
+    ) external override returns (uint amountToken, uint amountETH) {
+        address pair = UniswapV2Library.pairFor(factory, token, WETH);
+        uint value = approveMax ? uint(-1) : liquidity;
+        IUniswapV2Pair(pair).permit(msg.sender, address(this), value, deadline, v, r, s);
+        (amountToken, amountETH) = removeLiquidityETH(token, liquidity, amountTokenMin, amountETHMin, to, deadline);
+    }
+
+    // **** SWAP ****
+    // requires the initial amount to have already been sent to the first pair
+    function _swap(uint[] memory amounts, address[] memory path, address _to) private {
+        for (uint i; i < path.length - 1; i++) {
+            (address input, address output) = (path[i], path[i + 1]);
+            (address token0,) = UniswapV2Library.sortTokens(input, output);
+            uint amountOut = amounts[i + 1];
+            (uint amount0Out, uint amount1Out) = input == token0 ? (uint(0), amountOut) : (amountOut, uint(0));
+            address to = i < path.length - 2 ? UniswapV2Library.pairFor(factory, output, path[i + 2]) : _to;
+            IUniswapV2Pair(UniswapV2Library.pairFor(factory, input, output)).swap(amount0Out, amount1Out, to, new bytes(0));
+        }
+    }
+    function swapExactTokensForTokens(
+        uint amountIn,
+        uint amountOutMin,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external override ensure(deadline) returns (uint[] memory amounts) {
+        amounts = UniswapV2Library.getAmountsOut(factory, amountIn, path);
+        require(amounts[amounts.length - 1] >= amountOutMin, 'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT');
+        TransferHelper.safeTransferFrom(path[0], msg.sender, UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]);
+        _swap(amounts, path, to);
+    }
+    function swapTokensForExactTokens(
+        uint amountOut,
+        uint amountInMax,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external override ensure(deadline) returns (uint[] memory amounts) {
+        amounts = UniswapV2Library.getAmountsIn(factory, amountOut, path);
+        require(amounts[0] <= amountInMax, 'UniswapV2Router: EXCESSIVE_INPUT_AMOUNT');
+        TransferHelper.safeTransferFrom(path[0], msg.sender, UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]);
+        _swap(amounts, path, to);
+    }
+    function swapExactETHForTokens(uint amountOutMin, address[] calldata path, address to, uint deadline)
+        external
+        override
+        payable
+        ensure(deadline)
+        returns (uint[] memory amounts)
+    {
+        require(path[0] == WETH, 'UniswapV2Router: INVALID_PATH');
+        amounts = UniswapV2Library.getAmountsOut(factory, msg.value, path);
+        require(amounts[amounts.length - 1] >= amountOutMin, 'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT');
+        IWETH(WETH).deposit{value: amounts[0]}();
+        assert(IWETH(WETH).transfer(UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]));
+        _swap(amounts, path, to);
+    }
+    function swapTokensForExactETH(uint amountOut, uint amountInMax, address[] calldata path, address to, uint deadline)
+        external
+        override
+        ensure(deadline)
+        returns (uint[] memory amounts)
+    {
+        require(path[path.length - 1] == WETH, 'UniswapV2Router: INVALID_PATH');
+        amounts = UniswapV2Library.getAmountsIn(factory, amountOut, path);
+        require(amounts[0] <= amountInMax, 'UniswapV2Router: EXCESSIVE_INPUT_AMOUNT');
+        TransferHelper.safeTransferFrom(path[0], msg.sender, UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]);
+        _swap(amounts, path, address(this));
+        IWETH(WETH).withdraw(amounts[amounts.length - 1]);
+        TransferHelper.safeTransferETH(to, amounts[amounts.length - 1]);
+    }
+    function swapExactTokensForETH(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline)
+        external
+        override
+        ensure(deadline)
+        returns (uint[] memory amounts)
+    {
+        require(path[path.length - 1] == WETH, 'UniswapV2Router: INVALID_PATH');
+        amounts = UniswapV2Library.getAmountsOut(factory, amountIn, path);
+        require(amounts[amounts.length - 1] >= amountOutMin, 'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT');
+        TransferHelper.safeTransferFrom(path[0], msg.sender, UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]);
+        _swap(amounts, path, address(this));
+        IWETH(WETH).withdraw(amounts[amounts.length - 1]);
+        TransferHelper.safeTransferETH(to, amounts[amounts.length - 1]);
+    }
+    function swapETHForExactTokens(uint amountOut, address[] calldata path, address to, uint deadline)
+        external
+        override
+        payable
+        ensure(deadline)
+        returns (uint[] memory amounts)
+    {
+        require(path[0] == WETH, 'UniswapV2Router: INVALID_PATH');
+        amounts = UniswapV2Library.getAmountsIn(factory, amountOut, path);
+        require(amounts[0] <= msg.value, 'UniswapV2Router: EXCESSIVE_INPUT_AMOUNT');
+        IWETH(WETH).deposit{value: amounts[0]}();
+        assert(IWETH(WETH).transfer(UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]));
+        _swap(amounts, path, to);
+        if (msg.value > amounts[0]) TransferHelper.safeTransferETH(msg.sender, msg.value - amounts[0]); // refund dust eth, if any
+    }
+
+    function quote(uint amountA, uint reserveA, uint reserveB) public pure override returns (uint amountB) {
+        return UniswapV2Library.quote(amountA, reserveA, reserveB);
+    }
+
+    function getAmountOut(uint amountIn, uint reserveIn, uint reserveOut) public pure override returns (uint amountOut) {
+        return UniswapV2Library.getAmountOut(amountIn, reserveIn, reserveOut);
+    }
+
+    function getAmountIn(uint amountOut, uint reserveIn, uint reserveOut) public pure override returns (uint amountIn) {
+        return UniswapV2Library.getAmountOut(amountOut, reserveIn, reserveOut);
+    }
+
+    function getAmountsOut(uint amountIn, address[] memory path) public view override returns (uint[] memory amounts) {
+        return UniswapV2Library.getAmountsOut(factory, amountIn, path);
+    }
+
+    function getAmountsIn(uint amountOut, address[] memory path) public view override returns (uint[] memory amounts) {
+        return UniswapV2Library.getAmountsIn(factory, amountOut, path);
+    }
+}

contracts/v2-periphery/UniswapV2Router02.sol

+pragma solidity =0.6.6;
+
+import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Factory.sol';
+import '@uniswap/lib/contracts/libraries/TransferHelper.sol';
+
+import './interfaces/IUniswapV2Router02.sol';
+import './libraries/UniswapV2Library.sol';
+import './libraries/SafeMath.sol';
+import './interfaces/IERC20.sol';
+import './interfaces/IWETH.sol';
+
+contract UniswapV2Router02 is IUniswapV2Router02 {
+    using SafeMath for uint;
+
+    address public immutable override factory;
+    address public immutable override WETH;
+
+    modifier ensure(uint deadline) {
+        require(deadline >= block.timestamp, 'UniswapV2Router: EXPIRED');
+        _;
+    }
+
+    constructor(address _factory, address _WETH) public {
+        factory = _factory;
+        WETH = _WETH;
+    }
+
+    receive() external payable {
+        assert(msg.sender == WETH); // only accept ETH via fallback from the WETH contract
+    }
+
+    // **** ADD LIQUIDITY ****
+    function _addLiquidity(
+        address tokenA,
+        address tokenB,
+        uint amountADesired,
+        uint amountBDesired,
+        uint amountAMin,
+        uint amountBMin
+    ) internal virtual returns (uint amountA, uint amountB) {
+        // create the pair if it doesn't exist yet
+        if (IUniswapV2Factory(factory).getPair(tokenA, tokenB) == address(0)) {
+            IUniswapV2Factory(factory).createPair(tokenA, tokenB);
+        }
+        (uint reserveA, uint reserveB) = UniswapV2Library.getReserves(factory, tokenA, tokenB);
+        if (reserveA == 0 && reserveB == 0) {
+            (amountA, amountB) = (amountADesired, amountBDesired);
+        } else {
+            uint amountBOptimal = UniswapV2Library.quote(amountADesired, reserveA, reserveB);
+            if (amountBOptimal <= amountBDesired) {
+                require(amountBOptimal >= amountBMin, 'UniswapV2Router: INSUFFICIENT_B_AMOUNT');
+                (amountA, amountB) = (amountADesired, amountBOptimal);
+            } else {
+                uint amountAOptimal = UniswapV2Library.quote(amountBDesired, reserveB, reserveA);
+                assert(amountAOptimal <= amountADesired);
+                require(amountAOptimal >= amountAMin, 'UniswapV2Router: INSUFFICIENT_A_AMOUNT');
+                (amountA, amountB) = (amountAOptimal, amountBDesired);
+            }
+        }
+    }
+    function addLiquidity(
+        address tokenA,
+        address tokenB,
+        uint amountADesired,
+        uint amountBDesired,
+        uint amountAMin,
+        uint amountBMin,
+        address to,
+        uint deadline
+    ) external virtual override ensure(deadline) returns (uint amountA, uint amountB, uint liquidity) {
+        (amountA, amountB) = _addLiquidity(tokenA, tokenB, amountADesired, amountBDesired, amountAMin, amountBMin);
+        address pair = UniswapV2Library.pairFor(factory, tokenA, tokenB);
+        TransferHelper.safeTransferFrom(tokenA, msg.sender, pair, amountA);
+        TransferHelper.safeTransferFrom(tokenB, msg.sender, pair, amountB);
+        liquidity = IUniswapV2Pair(pair).mint(to);
+    }
+    function addLiquidityETH(
+        address token,
+        uint amountTokenDesired,
+        uint amountTokenMin,
+        uint amountETHMin,
+        address to,
+        uint deadline
+    ) external virtual override payable ensure(deadline) returns (uint amountToken, uint amountETH, uint liquidity) {
+        (amountToken, amountETH) = _addLiquidity(
+            token,
+            WETH,
+            amountTokenDesired,
+            msg.value,
+            amountTokenMin,
+            amountETHMin
+        );
+        address pair = UniswapV2Library.pairFor(factory, token, WETH);
+        TransferHelper.safeTransferFrom(token, msg.sender, pair, amountToken);
+        IWETH(WETH).deposit{value: amountETH}();
+        assert(IWETH(WETH).transfer(pair, amountETH));
+        liquidity = IUniswapV2Pair(pair).mint(to);
+        // refund dust eth, if any
+        if (msg.value > amountETH) TransferHelper.safeTransferETH(msg.sender, msg.value - amountETH);
+    }
+
+    // **** REMOVE LIQUIDITY ****
+    function removeLiquidity(
+        address tokenA,
+        address tokenB,
+        uint liquidity,
+        uint amountAMin,
+        uint amountBMin,
+        address to,
+        uint deadline
+    ) public virtual override ensure(deadline) returns (uint amountA, uint amountB) {
+        address pair = UniswapV2Library.pairFor(factory, tokenA, tokenB);
+        IUniswapV2Pair(pair).transferFrom(msg.sender, pair, liquidity); // send liquidity to pair
+        (uint amount0, uint amount1) = IUniswapV2Pair(pair).burn(to);
+        (address token0,) = UniswapV2Library.sortTokens(tokenA, tokenB);
+        (amountA, amountB) = tokenA == token0 ? (amount0, amount1) : (amount1, amount0);
+        require(amountA >= amountAMin, 'UniswapV2Router: INSUFFICIENT_A_AMOUNT');
+        require(amountB >= amountBMin, 'UniswapV2Router: INSUFFICIENT_B_AMOUNT');
+    }
+    function removeLiquidityETH(
+        address token,
+        uint liquidity,
+        uint amountTokenMin,
+        uint amountETHMin,
+        address to,
+        uint deadline
+    ) public virtual override ensure(deadline) returns (uint amountToken, uint amountETH) {
+        (amountToken, amountETH) = removeLiquidity(
+            token,
+            WETH,
+            liquidity,
+            amountTokenMin,
+            amountETHMin,
+            address(this),
+            deadline
+        );
+        TransferHelper.safeTransfer(token, to, amountToken);
+        IWETH(WETH).withdraw(amountETH);
+        TransferHelper.safeTransferETH(to, amountETH);
+    }
+    function removeLiquidityWithPermit(
+        address tokenA,
+        address tokenB,
+        uint liquidity,
+        uint amountAMin,
+        uint amountBMin,
+        address to,
+        uint deadline,
+        bool approveMax, uint8 v, bytes32 r, bytes32 s
+    ) external virtual override returns (uint amountA, uint amountB) {
+        address pair = UniswapV2Library.pairFor(factory, tokenA, tokenB);
+        uint value = approveMax ? uint(-1) : liquidity;
+        IUniswapV2Pair(pair).permit(msg.sender, address(this), value, deadline, v, r, s);
+        (amountA, amountB) = removeLiquidity(tokenA, tokenB, liquidity, amountAMin, amountBMin, to, deadline);
+    }
+    function removeLiquidityETHWithPermit(
+        address token,
+        uint liquidity,
+        uint amountTokenMin,
+        uint amountETHMin,
+        address to,
+        uint deadline,
+        bool approveMax, uint8 v, bytes32 r, bytes32 s
+    ) external virtual override returns (uint amountToken, uint amountETH) {
+        address pair = UniswapV2Library.pairFor(factory, token, WETH);
+        uint value = approveMax ? uint(-1) : liquidity;
+        IUniswapV2Pair(pair).permit(msg.sender, address(this), value, deadline, v, r, s);
+        (amountToken, amountETH) = removeLiquidityETH(token, liquidity, amountTokenMin, amountETHMin, to, deadline);
+    }
+
+    // **** REMOVE LIQUIDITY (supporting fee-on-transfer tokens) ****
+    function removeLiquidityETHSupportingFeeOnTransferTokens(
+        address token,
+        uint liquidity,
+        uint amountTokenMin,
+        uint amountETHMin,
+        address to,
+        uint deadline
+    ) public virtual override ensure(deadline) returns (uint amountETH) {
+        (, amountETH) = removeLiquidity(
+            token,
+            WETH,
+            liquidity,
+            amountTokenMin,
+            amountETHMin,
+            address(this),
+            deadline
+        );
+        TransferHelper.safeTransfer(token, to, IERC20(token).balanceOf(address(this)));
+        IWETH(WETH).withdraw(amountETH);
+        TransferHelper.safeTransferETH(to, amountETH);
+    }
+    function removeLiquidityETHWithPermitSupportingFeeOnTransferTokens(
+        address token,
+        uint liquidity,
+        uint amountTokenMin,
+        uint amountETHMin,
+        address to,
+        uint deadline,
+        bool approveMax, uint8 v, bytes32 r, bytes32 s
+    ) external virtual override returns (uint amountETH) {
+        address pair = UniswapV2Library.pairFor(factory, token, WETH);
+        uint value = approveMax ? uint(-1) : liquidity;
+        IUniswapV2Pair(pair).permit(msg.sender, address(this), value, deadline, v, r, s);
+        amountETH = removeLiquidityETHSupportingFeeOnTransferTokens(
+            token, liquidity, amountTokenMin, amountETHMin, to, deadline
+        );
+    }
+
+    // **** SWAP ****
+    // requires the initial amount to have already been sent to the first pair
+    function _swap(uint[] memory amounts, address[] memory path, address _to) internal virtual {
+        for (uint i; i < path.length - 1; i++) {
+            (address input, address output) = (path[i], path[i + 1]);
+            (address token0,) = UniswapV2Library.sortTokens(input, output);
+            uint amountOut = amounts[i + 1];
+            (uint amount0Out, uint amount1Out) = input == token0 ? (uint(0), amountOut) : (amountOut, uint(0));
+            address to = i < path.length - 2 ? UniswapV2Library.pairFor(factory, output, path[i + 2]) : _to;
+            IUniswapV2Pair(UniswapV2Library.pairFor(factory, input, output)).swap(
+                amount0Out, amount1Out, to, new bytes(0)
+            );
+        }
+    }
+    function swapExactTokensForTokens(
+        uint amountIn,
+        uint amountOutMin,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external virtual override ensure(deadline) returns (uint[] memory amounts) {
+        amounts = UniswapV2Library.getAmountsOut(factory, amountIn, path);
+        require(amounts[amounts.length - 1] >= amountOutMin, 'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT');
+        TransferHelper.safeTransferFrom(
+            path[0], msg.sender, UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]
+        );
+        _swap(amounts, path, to);
+    }
+    function swapTokensForExactTokens(
+        uint amountOut,
+        uint amountInMax,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external virtual override ensure(deadline) returns (uint[] memory amounts) {
+        amounts = UniswapV2Library.getAmountsIn(factory, amountOut, path);
+        require(amounts[0] <= amountInMax, 'UniswapV2Router: EXCESSIVE_INPUT_AMOUNT');
+        TransferHelper.safeTransferFrom(
+            path[0], msg.sender, UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]
+        );
+        _swap(amounts, path, to);
+    }
+    function swapExactETHForTokens(uint amountOutMin, address[] calldata path, address to, uint deadline)
+        external
+        virtual
+        override
+        payable
+        ensure(deadline)
+        returns (uint[] memory amounts)
+    {
+        require(path[0] == WETH, 'UniswapV2Router: INVALID_PATH');
+        amounts = UniswapV2Library.getAmountsOut(factory, msg.value, path);
+        require(amounts[amounts.length - 1] >= amountOutMin, 'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT');
+        IWETH(WETH).deposit{value: amounts[0]}();
+        assert(IWETH(WETH).transfer(UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]));
+        _swap(amounts, path, to);
+    }
+    function swapTokensForExactETH(uint amountOut, uint amountInMax, address[] calldata path, address to, uint deadline)
+        external
+        virtual
+        override
+        ensure(deadline)
+        returns (uint[] memory amounts)
+    {
+        require(path[path.length - 1] == WETH, 'UniswapV2Router: INVALID_PATH');
+        amounts = UniswapV2Library.getAmountsIn(factory, amountOut, path);
+        require(amounts[0] <= amountInMax, 'UniswapV2Router: EXCESSIVE_INPUT_AMOUNT');
+        TransferHelper.safeTransferFrom(
+            path[0], msg.sender, UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]
+        );
+        _swap(amounts, path, address(this));
+        IWETH(WETH).withdraw(amounts[amounts.length - 1]);
+        TransferHelper.safeTransferETH(to, amounts[amounts.length - 1]);
+    }
+    function swapExactTokensForETH(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline)
+        external
+        virtual
+        override
+        ensure(deadline)
+        returns (uint[] memory amounts)
+    {
+        require(path[path.length - 1] == WETH, 'UniswapV2Router: INVALID_PATH');
+        amounts = UniswapV2Library.getAmountsOut(factory, amountIn, path);
+        require(amounts[amounts.length - 1] >= amountOutMin, 'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT');
+        TransferHelper.safeTransferFrom(
+            path[0], msg.sender, UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]
+        );
+        _swap(amounts, path, address(this));
+        IWETH(WETH).withdraw(amounts[amounts.length - 1]);
+        TransferHelper.safeTransferETH(to, amounts[amounts.length - 1]);
+    }
+    function swapETHForExactTokens(uint amountOut, address[] calldata path, address to, uint deadline)
+        external
+        virtual
+        override
+        payable
+        ensure(deadline)
+        returns (uint[] memory amounts)
+    {
+        require(path[0] == WETH, 'UniswapV2Router: INVALID_PATH');
+        amounts = UniswapV2Library.getAmountsIn(factory, amountOut, path);
+        require(amounts[0] <= msg.value, 'UniswapV2Router: EXCESSIVE_INPUT_AMOUNT');
+        IWETH(WETH).deposit{value: amounts[0]}();
+        assert(IWETH(WETH).transfer(UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]));
+        _swap(amounts, path, to);
+        // refund dust eth, if any
+        if (msg.value > amounts[0]) TransferHelper.safeTransferETH(msg.sender, msg.value - amounts[0]);
+    }
+
+    // **** SWAP (supporting fee-on-transfer tokens) ****
+    // requires the initial amount to have already been sent to the first pair
+    function _swapSupportingFeeOnTransferTokens(address[] memory path, address _to) internal virtual {
+        for (uint i; i < path.length - 1; i++) {
+            (address input, address output) = (path[i], path[i + 1]);
+            (address token0,) = UniswapV2Library.sortTokens(input, output);
+            IUniswapV2Pair pair = IUniswapV2Pair(UniswapV2Library.pairFor(factory, input, output));
+            uint amountInput;
+            uint amountOutput;
+            { // scope to avoid stack too deep errors
+            (uint reserve0, uint reserve1,) = pair.getReserves();
+            (uint reserveInput, uint reserveOutput) = input == token0 ? (reserve0, reserve1) : (reserve1, reserve0);
+            amountInput = IERC20(input).balanceOf(address(pair)).sub(reserveInput);
+            amountOutput = UniswapV2Library.getAmountOut(amountInput, reserveInput, reserveOutput);
+            }
+            (uint amount0Out, uint amount1Out) = input == token0 ? (uint(0), amountOutput) : (amountOutput, uint(0));
+            address to = i < path.length - 2 ? UniswapV2Library.pairFor(factory, output, path[i + 2]) : _to;
+            pair.swap(amount0Out, amount1Out, to, new bytes(0));
+        }
+    }
+    function swapExactTokensForTokensSupportingFeeOnTransferTokens(
+        uint amountIn,
+        uint amountOutMin,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external virtual override ensure(deadline) {
+        TransferHelper.safeTransferFrom(
+            path[0], msg.sender, UniswapV2Library.pairFor(factory, path[0], path[1]), amountIn
+        );
+        uint balanceBefore = IERC20(path[path.length - 1]).balanceOf(to);
+        _swapSupportingFeeOnTransferTokens(path, to);
+        require(
+            IERC20(path[path.length - 1]).balanceOf(to).sub(balanceBefore) >= amountOutMin,
+            'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT'
+        );
+    }
+    function swapExactETHForTokensSupportingFeeOnTransferTokens(
+        uint amountOutMin,
+        address[] calldata path,
+        address to,
+        uint deadline
+    )
+        external
+        virtual
+        override
+        payable
+        ensure(deadline)
+    {
+        require(path[0] == WETH, 'UniswapV2Router: INVALID_PATH');
+        uint amountIn = msg.value;
+        IWETH(WETH).deposit{value: amountIn}();
+        assert(IWETH(WETH).transfer(UniswapV2Library.pairFor(factory, path[0], path[1]), amountIn));
+        uint balanceBefore = IERC20(path[path.length - 1]).balanceOf(to);
+        _swapSupportingFeeOnTransferTokens(path, to);
+        require(
+            IERC20(path[path.length - 1]).balanceOf(to).sub(balanceBefore) >= amountOutMin,
+            'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT'
+        );
+    }
+    function swapExactTokensForETHSupportingFeeOnTransferTokens(
+        uint amountIn,
+        uint amountOutMin,
+        address[] calldata path,
+        address to,
+        uint deadline
+    )
+        external
+        virtual
+        override
+        ensure(deadline)
+    {
+        require(path[path.length - 1] == WETH, 'UniswapV2Router: INVALID_PATH');
+        TransferHelper.safeTransferFrom(
+            path[0], msg.sender, UniswapV2Library.pairFor(factory, path[0], path[1]), amountIn
+        );
+        _swapSupportingFeeOnTransferTokens(path, address(this));
+        uint amountOut = IERC20(WETH).balanceOf(address(this));
+        require(amountOut >= amountOutMin, 'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT');
+        IWETH(WETH).withdraw(amountOut);
+        TransferHelper.safeTransferETH(to, amountOut);
+    }
+
+    // **** LIBRARY FUNCTIONS ****
+    function quote(uint amountA, uint reserveA, uint reserveB) public pure virtual override returns (uint amountB) {
+        return UniswapV2Library.quote(amountA, reserveA, reserveB);
+    }
+
+    function getAmountOut(uint amountIn, uint reserveIn, uint reserveOut)
+        public
+        pure
+        virtual
+        override
+        returns (uint amountOut)
+    {
+        return UniswapV2Library.getAmountOut(amountIn, reserveIn, reserveOut);
+    }
+
+    function getAmountIn(uint amountOut, uint reserveIn, uint reserveOut)
+        public
+        pure
+        virtual
+        override
+        returns (uint amountIn)
+    {
+        return UniswapV2Library.getAmountIn(amountOut, reserveIn, reserveOut);
+    }
+
+    function getAmountsOut(uint amountIn, address[] memory path)
+        public
+        view
+        virtual
+        override
+        returns (uint[] memory amounts)
+    {
+        return UniswapV2Library.getAmountsOut(factory, amountIn, path);
+    }
+
+    function getAmountsIn(uint amountOut, address[] memory path)
+        public
+        view
+        virtual
+        override
+        returns (uint[] memory amounts)
+    {
+        return UniswapV2Library.getAmountsIn(factory, amountOut, path);
+    }
+}

contracts/v2-periphery/examples/ExampleComputeLiquidityValue.sol

+pragma solidity =0.6.6;
+
+import '../libraries/UniswapV2LiquidityMathLibrary.sol';
+
+contract ExampleComputeLiquidityValue {
+    using SafeMath for uint256;
+
+    address public immutable factory;
+
+    constructor(address factory_) public {
+        factory = factory_;
+    }
+
+    // see UniswapV2LiquidityMathLibrary#getReservesAfterArbitrage
+    function getReservesAfterArbitrage(
+        address tokenA,
+        address tokenB,
+        uint256 truePriceTokenA,
+        uint256 truePriceTokenB
+    ) external view returns (uint256 reserveA, uint256 reserveB) {
+        return UniswapV2LiquidityMathLibrary.getReservesAfterArbitrage(
+            factory,
+            tokenA,
+            tokenB,
+            truePriceTokenA,
+            truePriceTokenB
+        );
+    }
+
+    // see UniswapV2LiquidityMathLibrary#getLiquidityValue
+    function getLiquidityValue(
+        address tokenA,
+        address tokenB,
+        uint256 liquidityAmount
+    ) external view returns (
+        uint256 tokenAAmount,
+        uint256 tokenBAmount
+    ) {
+        return UniswapV2LiquidityMathLibrary.getLiquidityValue(
+            factory,
+            tokenA,
+            tokenB,
+            liquidityAmount
+        );
+    }
+
+    // see UniswapV2LiquidityMathLibrary#getLiquidityValueAfterArbitrageToPrice
+    function getLiquidityValueAfterArbitrageToPrice(
+        address tokenA,
+        address tokenB,
+        uint256 truePriceTokenA,
+        uint256 truePriceTokenB,
+        uint256 liquidityAmount
+    ) external view returns (
+        uint256 tokenAAmount,
+        uint256 tokenBAmount
+    ) {
+        return UniswapV2LiquidityMathLibrary.getLiquidityValueAfterArbitrageToPrice(
+            factory,
+            tokenA,
+            tokenB,
+            truePriceTokenA,
+            truePriceTokenB,
+            liquidityAmount
+        );
+    }
+
+    // test function to measure the gas cost of the above function
+    function getGasCostOfGetLiquidityValueAfterArbitrageToPrice(
+        address tokenA,
+        address tokenB,
+        uint256 truePriceTokenA,
+        uint256 truePriceTokenB,
+        uint256 liquidityAmount
+    ) external view returns (
+        uint256
+    ) {
+        uint gasBefore = gasleft();
+        UniswapV2LiquidityMathLibrary.getLiquidityValueAfterArbitrageToPrice(
+            factory,
+            tokenA,
+            tokenB,
+            truePriceTokenA,
+            truePriceTokenB,
+            liquidityAmount
+        );
+        uint gasAfter = gasleft();
+        return gasBefore - gasAfter;
+    }
+}

contracts/v2-periphery/examples/ExampleFlashSwap.sol

+pragma solidity =0.6.6;
+
+import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Callee.sol';
+
+import '../libraries/UniswapV2Library.sol';
+import '../interfaces/V1/IUniswapV1Factory.sol';
+import '../interfaces/V1/IUniswapV1Exchange.sol';
+import '../interfaces/IUniswapV2Router01.sol';
+import '../interfaces/IERC20.sol';
+import '../interfaces/IWETH.sol';
+
+contract ExampleFlashSwap is IUniswapV2Callee {
+    IUniswapV1Factory immutable factoryV1;
+    address immutable factory;
+    IWETH immutable WETH;
+
+    constructor(address _factory, address _factoryV1, address router) public {
+        factoryV1 = IUniswapV1Factory(_factoryV1);
+        factory = _factory;
+        WETH = IWETH(IUniswapV2Router01(router).WETH());
+    }
+
+    // needs to accept ETH from any V1 exchange and WETH. ideally this could be enforced, as in the router,
+    // but it's not possible because it requires a call to the v1 factory, which takes too much gas
+    receive() external payable {}
+
+    // gets tokens/WETH via a V2 flash swap, swaps for the ETH/tokens on V1, repays V2, and keeps the rest!
+    function uniswapV2Call(address sender, uint amount0, uint amount1, bytes calldata data) external override {
+        address[] memory path = new address[](2);
+        uint amountToken;
+        uint amountETH;
+        { // scope for token{0,1}, avoids stack too deep errors
+        address token0 = IUniswapV2Pair(msg.sender).token0();
+        address token1 = IUniswapV2Pair(msg.sender).token1();
+        assert(msg.sender == UniswapV2Library.pairFor(factory, token0, token1)); // ensure that msg.sender is actually a V2 pair
+        assert(amount0 == 0 || amount1 == 0); // this strategy is unidirectional
+        path[0] = amount0 == 0 ? token0 : token1;
+        path[1] = amount0 == 0 ? token1 : token0;
+        amountToken = token0 == address(WETH) ? amount1 : amount0;
+        amountETH = token0 == address(WETH) ? amount0 : amount1;
+        }
+
+        assert(path[0] == address(WETH) || path[1] == address(WETH)); // this strategy only works with a V2 WETH pair
+        IERC20 token = IERC20(path[0] == address(WETH) ? path[1] : path[0]);
+        IUniswapV1Exchange exchangeV1 = IUniswapV1Exchange(factoryV1.getExchange(address(token))); // get V1 exchange
+
+        if (amountToken > 0) {
+            (uint minETH) = abi.decode(data, (uint)); // slippage parameter for V1, passed in by caller
+            token.approve(address(exchangeV1), amountToken);
+            uint amountReceived = exchangeV1.tokenToEthSwapInput(amountToken, minETH, uint(-1));
+            uint amountRequired = UniswapV2Library.getAmountsIn(factory, amountToken, path)[0];
+            assert(amountReceived > amountRequired); // fail if we didn't get enough ETH back to repay our flash loan
+            WETH.deposit{value: amountRequired}();
+            assert(WETH.transfer(msg.sender, amountRequired)); // return WETH to V2 pair
+            (bool success,) = sender.call{value: amountReceived - amountRequired}(new bytes(0)); // keep the rest! (ETH)
+            assert(success);
+        } else {
+            (uint minTokens) = abi.decode(data, (uint)); // slippage parameter for V1, passed in by caller
+            WETH.withdraw(amountETH);
+            uint amountReceived = exchangeV1.ethToTokenSwapInput{value: amountETH}(minTokens, uint(-1));
+            uint amountRequired = UniswapV2Library.getAmountsIn(factory, amountETH, path)[0];
+            assert(amountReceived > amountRequired); // fail if we didn't get enough tokens back to repay our flash loan
+            assert(token.transfer(msg.sender, amountRequired)); // return tokens to V2 pair
+            assert(token.transfer(sender, amountReceived - amountRequired)); // keep the rest! (tokens)
+        }
+    }
+}

contracts/v2-periphery/examples/ExampleOracleSimple.sol

+pragma solidity =0.6.6;
+
+import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Factory.sol';
+import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol';
+import '@uniswap/lib/contracts/libraries/FixedPoint.sol';
+
+import '../libraries/UniswapV2OracleLibrary.sol';
+import '../libraries/UniswapV2Library.sol';
+
+// fixed window oracle that recomputes the average price for the entire period once every period
+// note that the price average is only guaranteed to be over at least 1 period, but may be over a longer period
+contract ExampleOracleSimple {
+    using FixedPoint for *;
+
+    uint public constant PERIOD = 24 hours;
+
+    IUniswapV2Pair immutable pair;
+    address public immutable token0;
+    address public immutable token1;
+
+    uint    public price0CumulativeLast;
+    uint    public price1CumulativeLast;
+    uint32  public blockTimestampLast;
+    FixedPoint.uq112x112 public price0Average;
+    FixedPoint.uq112x112 public price1Average;
+
+    constructor(address factory, address tokenA, address tokenB) public {
+        IUniswapV2Pair _pair = IUniswapV2Pair(UniswapV2Library.pairFor(factory, tokenA, tokenB));
+        pair = _pair;
+        token0 = _pair.token0();
+        token1 = _pair.token1();
+        price0CumulativeLast = _pair.price0CumulativeLast(); // fetch the current accumulated price value (1 / 0)
+        price1CumulativeLast = _pair.price1CumulativeLast(); // fetch the current accumulated price value (0 / 1)
+        uint112 reserve0;
+        uint112 reserve1;
+        (reserve0, reserve1, blockTimestampLast) = _pair.getReserves();
+        require(reserve0 != 0 && reserve1 != 0, 'ExampleOracleSimple: NO_RESERVES'); // ensure that there's liquidity in the pair
+    }
+
+    function update() external {
+        (uint price0Cumulative, uint price1Cumulative, uint32 blockTimestamp) =
+            UniswapV2OracleLibrary.currentCumulativePrices(address(pair));
+        uint32 timeElapsed = blockTimestamp - blockTimestampLast; // overflow is desired
+
+        // ensure that at least one full period has passed since the last update
+        require(timeElapsed >= PERIOD, 'ExampleOracleSimple: PERIOD_NOT_ELAPSED');
+
+        // overflow is desired, casting never truncates
+        // cumulative price is in (uq112x112 price * seconds) units so we simply wrap it after division by time elapsed
+        price0Average = FixedPoint.uq112x112(uint224((price0Cumulative - price0CumulativeLast) / timeElapsed));
+        price1Average = FixedPoint.uq112x112(uint224((price1Cumulative - price1CumulativeLast) / timeElapsed));
+
+        price0CumulativeLast = price0Cumulative;
+        price1CumulativeLast = price1Cumulative;
+        blockTimestampLast = blockTimestamp;
+    }
+
+    // note this will always return 0 before update has been called successfully for the first time.
+    function consult(address token, uint amountIn) external view returns (uint amountOut) {
+        if (token == token0) {
+            amountOut = price0Average.mul(amountIn).decode144();
+        } else {
+            require(token == token1, 'ExampleOracleSimple: INVALID_TOKEN');
+            amountOut = price1Average.mul(amountIn).decode144();
+        }
+    }
+}

contracts/v2-periphery/examples/ExampleSlidingWindowOracle.sol

+pragma solidity =0.6.6;
+
+import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Factory.sol';
+import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol';
+import '@uniswap/lib/contracts/libraries/FixedPoint.sol';
+
+import '../libraries/SafeMath.sol';
+import '../libraries/UniswapV2Library.sol';
+import '../libraries/UniswapV2OracleLibrary.sol';
+
+// sliding window oracle that uses observations collected over a window to provide moving price averages in the past
+// `windowSize` with a precision of `windowSize / granularity`
+// note this is a singleton oracle and only needs to be deployed once per desired parameters, which
+// differs from the simple oracle which must be deployed once per pair.
+contract ExampleSlidingWindowOracle {
+    using FixedPoint for *;
+    using SafeMath for uint;
+
+    struct Observation {
+        uint timestamp;
+        uint price0Cumulative;
+        uint price1Cumulative;
+    }
+
+    address public immutable factory;
+    // the desired amount of time over which the moving average should be computed, e.g. 24 hours
+    uint public immutable windowSize;
+    // the number of observations stored for each pair, i.e. how many price observations are stored for the window.
+    // as granularity increases from 1, more frequent updates are needed, but moving averages become more precise.
+    // averages are computed over intervals with sizes in the range:
+    //   [windowSize - (windowSize / granularity) * 2, windowSize]
+    // e.g. if the window size is 24 hours, and the granularity is 24, the oracle will return the average price for
+    //   the period:
+    //   [now - [22 hours, 24 hours], now]
+    uint8 public immutable granularity;
+    // this is redundant with granularity and windowSize, but stored for gas savings & informational purposes.
+    uint public immutable periodSize;
+
+    // mapping from pair address to a list of price observations of that pair
+    mapping(address => Observation[]) public pairObservations;
+
+    constructor(address factory_, uint windowSize_, uint8 granularity_) public {
+        require(granularity_ > 1, 'SlidingWindowOracle: GRANULARITY');
+        require(
+            (periodSize = windowSize_ / granularity_) * granularity_ == windowSize_,
+            'SlidingWindowOracle: WINDOW_NOT_EVENLY_DIVISIBLE'
+        );
+        factory = factory_;
+        windowSize = windowSize_;
+        granularity = granularity_;
+    }
+
+    // returns the index of the observation corresponding to the given timestamp
+    function observationIndexOf(uint timestamp) public view returns (uint8 index) {
+        uint epochPeriod = timestamp / periodSize;
+        return uint8(epochPeriod % granularity);
+    }
+
+    // returns the observation from the oldest epoch (at the beginning of the window) relative to the current time
+    function getFirstObservationInWindow(address pair) private view returns (Observation storage firstObservation) {
+        uint8 observationIndex = observationIndexOf(block.timestamp);
+        // no overflow issue. if observationIndex + 1 overflows, result is still zero.
+        uint8 firstObservationIndex = (observationIndex + 1) % granularity;
+        firstObservation = pairObservations[pair][firstObservationIndex];
+    }
+
+    // update the cumulative price for the observation at the current timestamp. each observation is updated at most
+    // once per epoch period.
+    function update(address tokenA, address tokenB) external {
+        address pair = UniswapV2Library.pairFor(factory, tokenA, tokenB);
+
+        // populate the array with empty observations (first call only)
+        for (uint i = pairObservations[pair].length; i < granularity; i++) {
+            pairObservations[pair].push();
+        }
+
+        // get the observation for the current period
+        uint8 observationIndex = observationIndexOf(block.timestamp);
+        Observation storage observation = pairObservations[pair][observationIndex];
+
+        // we only want to commit updates once per period (i.e. windowSize / granularity)
+        uint timeElapsed = block.timestamp - observation.timestamp;
+        if (timeElapsed > periodSize) {
+            (uint price0Cumulative, uint price1Cumulative,) = UniswapV2OracleLibrary.currentCumulativePrices(pair);
+            observation.timestamp = block.timestamp;
+            observation.price0Cumulative = price0Cumulative;
+            observation.price1Cumulative = price1Cumulative;
+        }
+    }
+
+    // given the cumulative prices of the start and end of a period, and the length of the period, compute the average
+    // price in terms of how much amount out is received for the amount in
+    function computeAmountOut(
+        uint priceCumulativeStart, uint priceCumulativeEnd,
+        uint timeElapsed, uint amountIn
+    ) private pure returns (uint amountOut) {
+        // overflow is desired.
+        FixedPoint.uq112x112 memory priceAverage = FixedPoint.uq112x112(
+            uint224((priceCumulativeEnd - priceCumulativeStart) / timeElapsed)
+        );
+        amountOut = priceAverage.mul(amountIn).decode144();
+    }
+
+    // returns the amount out corresponding to the amount in for a given token using the moving average over the time
+    // range [now - [windowSize, windowSize - periodSize * 2], now]
+    // update must have been called for the bucket corresponding to timestamp `now - windowSize`
+    function consult(address tokenIn, uint amountIn, address tokenOut) external view returns (uint amountOut) {
+        address pair = UniswapV2Library.pairFor(factory, tokenIn, tokenOut);
+        Observation storage firstObservation = getFirstObservationInWindow(pair);
+
+        uint timeElapsed = block.timestamp - firstObservation.timestamp;
+        require(timeElapsed <= windowSize, 'SlidingWindowOracle: MISSING_HISTORICAL_OBSERVATION');
+        // should never happen.
+        require(timeElapsed >= windowSize - periodSize * 2, 'SlidingWindowOracle: UNEXPECTED_TIME_ELAPSED');
+
+        (uint price0Cumulative, uint price1Cumulative,) = UniswapV2OracleLibrary.currentCumulativePrices(pair);
+        (address token0,) = UniswapV2Library.sortTokens(tokenIn, tokenOut);
+
+        if (token0 == tokenIn) {
+            return computeAmountOut(firstObservation.price0Cumulative, price0Cumulative, timeElapsed, amountIn);
+        } else {
+            return computeAmountOut(firstObservation.price1Cumulative, price1Cumulative, timeElapsed, amountIn);
+        }
+    }
+}

contracts/v2-periphery/examples/ExampleSwapToPrice.sol

+pragma solidity =0.6.6;
+
+import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol';
+import '@uniswap/lib/contracts/libraries/Babylonian.sol';
+import '@uniswap/lib/contracts/libraries/TransferHelper.sol';
+
+import '../libraries/UniswapV2LiquidityMathLibrary.sol';
+import '../interfaces/IERC20.sol';
+import '../interfaces/IUniswapV2Router01.sol';
+import '../libraries/SafeMath.sol';
+import '../libraries/UniswapV2Library.sol';
+
+contract ExampleSwapToPrice {
+    using SafeMath for uint256;
+
+    IUniswapV2Router01 public immutable router;
+    address public immutable factory;
+
+    constructor(address factory_, IUniswapV2Router01 router_) public {
+        factory = factory_;
+        router = router_;
+    }
+
+    // swaps an amount of either token such that the trade is profit-maximizing, given an external true price
+    // true price is expressed in the ratio of token A to token B
+    // caller must approve this contract to spend whichever token is intended to be swapped
+    function swapToPrice(
+        address tokenA,
+        address tokenB,
+        uint256 truePriceTokenA,
+        uint256 truePriceTokenB,
+        uint256 maxSpendTokenA,
+        uint256 maxSpendTokenB,
+        address to,
+        uint256 deadline
+    ) public {
+        // true price is expressed as a ratio, so both values must be non-zero
+        require(truePriceTokenA != 0 && truePriceTokenB != 0, "ExampleSwapToPrice: ZERO_PRICE");
+        // caller can specify 0 for either if they wish to swap in only one direction, but not both
+        require(maxSpendTokenA != 0 || maxSpendTokenB != 0, "ExampleSwapToPrice: ZERO_SPEND");
+
+        bool aToB;
+        uint256 amountIn;
+        {
+            (uint256 reserveA, uint256 reserveB) = UniswapV2Library.getReserves(factory, tokenA, tokenB);
+            (aToB, amountIn) = UniswapV2LiquidityMathLibrary.computeProfitMaximizingTrade(
+                truePriceTokenA, truePriceTokenB,
+                reserveA, reserveB
+            );
+        }
+
+        require(amountIn > 0, 'ExampleSwapToPrice: ZERO_AMOUNT_IN');
+
+        // spend up to the allowance of the token in
+        uint256 maxSpend = aToB ? maxSpendTokenA : maxSpendTokenB;
+        if (amountIn > maxSpend) {
+            amountIn = maxSpend;
+        }
+
+        address tokenIn = aToB ? tokenA : tokenB;
+        address tokenOut = aToB ? tokenB : tokenA;
+        TransferHelper.safeTransferFrom(tokenIn, msg.sender, address(this), amountIn);
+        TransferHelper.safeApprove(tokenIn, address(router), amountIn);
+
+        address[] memory path = new address[](2);
+        path[0] = tokenIn;
+        path[1] = tokenOut;
+
+        router.swapExactTokensForTokens(
+            amountIn,
+            0, // amountOutMin: we can skip computing this number because the math is tested
+            path,
+            to,
+            deadline
+        );
+    }
+}

contracts/v2-periphery/examples/README.md

+# Examples
+
+## Disclaimer
+
+These contracts are for demonstrative purposes only.
+While these contracts have unit tests, and we generally expect them to be
+correct, there are no guarantees about the correctness or security of 
+these contracts. We hold these contracts to a different standard of 
+correctness and security than other contracts in this repository. 
+E.g., we have explicitly excluded these contracts from the
+[bug bounty](https://uniswap.org/bug-bounty/#scope). 
+
+You must do your own due diligence if you wish to use code
+from these examples in your project.

contracts/v2-periphery/interfaces/IERC20.sol

+pragma solidity >=0.5.0;
+
+interface IERC20 {
+    event Approval(address indexed owner, address indexed spender, uint value);
+    event Transfer(address indexed from, address indexed to, uint 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 (uint);
+    function balanceOf(address owner) external view returns (uint);
+    function allowance(address owner, address spender) external view returns (uint);
+
+    function approve(address spender, uint value) external returns (bool);
+    function transfer(address to, uint value) external returns (bool);
+    function transferFrom(address from, address to, uint value) external returns (bool);
+}

contracts/v2-periphery/interfaces/IUniswapV2Migrator.sol

+pragma solidity >=0.5.0;
+
+interface IUniswapV2Migrator {
+    function migrate(address token, uint amountTokenMin, uint amountETHMin, address to, uint deadline) external;
+}

contracts/v2-periphery/interfaces/IUniswapV2Router01.sol

+pragma solidity >=0.6.2;
+
+interface IUniswapV2Router01 {
+    function factory() external pure returns (address);
+    function WETH() external pure returns (address);
+
+    function addLiquidity(
+        address tokenA,
+        address tokenB,
+        uint amountADesired,
+        uint amountBDesired,
+        uint amountAMin,
+        uint amountBMin,
+        address to,
+        uint deadline
+    ) external returns (uint amountA, uint amountB, uint liquidity);
+    function addLiquidityETH(
+        address token,
+        uint amountTokenDesired,
+        uint amountTokenMin,
+        uint amountETHMin,
+        address to,
+        uint deadline
+    ) external payable returns (uint amountToken, uint amountETH, uint liquidity);
+    function removeLiquidity(
+        address tokenA,
+        address tokenB,
+        uint liquidity,
+        uint amountAMin,
+        uint amountBMin,
+        address to,
+        uint deadline
+    ) external returns (uint amountA, uint amountB);
+    function removeLiquidityETH(
+        address token,
+        uint liquidity,
+        uint amountTokenMin,
+        uint amountETHMin,
+        address to,
+        uint deadline
+    ) external returns (uint amountToken, uint amountETH);
+    function removeLiquidityWithPermit(
+        address tokenA,
+        address tokenB,
+        uint liquidity,
+        uint amountAMin,
+        uint amountBMin,
+        address to,
+        uint deadline,
+        bool approveMax, uint8 v, bytes32 r, bytes32 s
+    ) external returns (uint amountA, uint amountB);
+    function removeLiquidityETHWithPermit(
+        address token,
+        uint liquidity,
+        uint amountTokenMin,
+        uint amountETHMin,
+        address to,
+        uint deadline,
+        bool approveMax, uint8 v, bytes32 r, bytes32 s
+    ) external returns (uint amountToken, uint amountETH);
+    function swapExactTokensForTokens(
+        uint amountIn,
+        uint amountOutMin,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external returns (uint[] memory amounts);
+    function swapTokensForExactTokens(
+        uint amountOut,
+        uint amountInMax,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external returns (uint[] memory amounts);
+    function swapExactETHForTokens(uint amountOutMin, address[] calldata path, address to, uint deadline)
+        external
+        payable
+        returns (uint[] memory amounts);
+    function swapTokensForExactETH(uint amountOut, uint amountInMax, address[] calldata path, address to, uint deadline)
+        external
+        returns (uint[] memory amounts);
+    function swapExactTokensForETH(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline)
+        external
+        returns (uint[] memory amounts);
+    function swapETHForExactTokens(uint amountOut, address[] calldata path, address to, uint deadline)
+        external
+        payable
+        returns (uint[] memory amounts);
+
+    function quote(uint amountA, uint reserveA, uint reserveB) external pure returns (uint amountB);
+    function getAmountOut(uint amountIn, uint reserveIn, uint reserveOut) external pure returns (uint amountOut);
+    function getAmountIn(uint amountOut, uint reserveIn, uint reserveOut) external pure returns (uint amountIn);
+    function getAmountsOut(uint amountIn, address[] calldata path) external view returns (uint[] memory amounts);
+    function getAmountsIn(uint amountOut, address[] calldata path) external view returns (uint[] memory amounts);
+}

contracts/v2-periphery/interfaces/IUniswapV2Router02.sol

+pragma solidity >=0.6.2;
+
+import './IUniswapV2Router01.sol';
+
+interface IUniswapV2Router02 is IUniswapV2Router01 {
+    function removeLiquidityETHSupportingFeeOnTransferTokens(
+        address token,
+        uint liquidity,
+        uint amountTokenMin,
+        uint amountETHMin,
+        address to,
+        uint deadline
+    ) external returns (uint amountETH);
+    function removeLiquidityETHWithPermitSupportingFeeOnTransferTokens(
+        address token,
+        uint liquidity,
+        uint amountTokenMin,
+        uint amountETHMin,
+        address to,
+        uint deadline,
+        bool approveMax, uint8 v, bytes32 r, bytes32 s
+    ) external returns (uint amountETH);
+
+    function swapExactTokensForTokensSupportingFeeOnTransferTokens(
+        uint amountIn,
+        uint amountOutMin,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external;
+    function swapExactETHForTokensSupportingFeeOnTransferTokens(
+        uint amountOutMin,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external payable;
+    function swapExactTokensForETHSupportingFeeOnTransferTokens(
+        uint amountIn,
+        uint amountOutMin,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external;
+}

contracts/v2-periphery/interfaces/IWETH.sol

+pragma solidity >=0.5.0;
+
+interface IWETH {
+    function deposit() external payable;
+    function transfer(address to, uint value) external returns (bool);
+    function withdraw(uint) external;
+}

contracts/v2-periphery/interfaces/V1/IUniswapV1Exchange.sol

+pragma solidity >=0.5.0;
+
+interface IUniswapV1Exchange {
+    function balanceOf(address owner) external view returns (uint);
+    function transferFrom(address from, address to, uint value) external returns (bool);
+    function removeLiquidity(uint, uint, uint, uint) external returns (uint, uint);
+    function tokenToEthSwapInput(uint, uint, uint) external returns (uint);
+    function ethToTokenSwapInput(uint, uint) external payable returns (uint);
+}

contracts/v2-periphery/interfaces/V1/IUniswapV1Factory.sol

+pragma solidity >=0.5.0;
+
+interface IUniswapV1Factory {
+    function getExchange(address) external view returns (address);
+}

contracts/v2-periphery/libraries/SafeMath.sol

+pragma solidity =0.6.6;
+
+// a library for performing overflow-safe math, courtesy of DappHub (https://github.com/dapphub/ds-math)
+
+library SafeMath {
+    function add(uint x, uint y) internal pure returns (uint z) {
+        require((z = x + y) >= x, 'ds-math-add-overflow');
+    }
+
+    function sub(uint x, uint y) internal pure returns (uint z) {
+        require((z = x - y) <= x, 'ds-math-sub-underflow');
+    }
+
+    function mul(uint x, uint y) internal pure returns (uint z) {
+        require(y == 0 || (z = x * y) / y == x, 'ds-math-mul-overflow');
+    }
+}

contracts/v2-periphery/libraries/UniswapV2Library.sol

+pragma solidity >=0.5.0;
+
+import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol';
+
+import "./SafeMath.sol";
+
+library UniswapV2Library {
+    using SafeMath for uint;
+
+    // returns sorted token addresses, used to handle return values from pairs sorted in this order
+    function sortTokens(address tokenA, address tokenB) internal pure returns (address token0, address token1) {
+        require(tokenA != tokenB, 'UniswapV2Library: IDENTICAL_ADDRESSES');
+        (token0, token1) = tokenA < tokenB ? (tokenA, tokenB) : (tokenB, tokenA);
+        require(token0 != address(0), 'UniswapV2Library: ZERO_ADDRESS');
+    }
+
+    // calculates the CREATE2 address for a pair without making any external calls
+    function pairFor(address factory, address tokenA, address tokenB) internal pure returns (address pair) {
+        (address token0, address token1) = sortTokens(tokenA, tokenB);
+        pair = address(uint(keccak256(abi.encodePacked(
+                hex'ff',
+                factory,
+                keccak256(abi.encodePacked(token0, token1)),
+                hex'96e8ac4277198ff8b6f785478aa9a39f403cb768dd02cbee326c3e7da348845f' // init code hash
+            ))));
+    }
+
+    // fetches and sorts the reserves for a pair
+    function getReserves(address factory, address tokenA, address tokenB) internal view returns (uint reserveA, uint reserveB) {
+        (address token0,) = sortTokens(tokenA, tokenB);
+        (uint reserve0, uint reserve1,) = IUniswapV2Pair(pairFor(factory, tokenA, tokenB)).getReserves();
+        (reserveA, reserveB) = tokenA == token0 ? (reserve0, reserve1) : (reserve1, reserve0);
+    }
+
+    // given some amount of an asset and pair reserves, returns an equivalent amount of the other asset
+    function quote(uint amountA, uint reserveA, uint reserveB) internal pure returns (uint amountB) {
+        require(amountA > 0, 'UniswapV2Library: INSUFFICIENT_AMOUNT');
+        require(reserveA > 0 && reserveB > 0, 'UniswapV2Library: INSUFFICIENT_LIQUIDITY');
+        amountB = amountA.mul(reserveB) / reserveA;
+    }
+
+    // given an input amount of an asset and pair reserves, returns the maximum output amount of the other asset
+    function getAmountOut(uint amountIn, uint reserveIn, uint reserveOut) internal pure returns (uint amountOut) {
+        require(amountIn > 0, 'UniswapV2Library: INSUFFICIENT_INPUT_AMOUNT');
+        require(reserveIn > 0 && reserveOut > 0, 'UniswapV2Library: INSUFFICIENT_LIQUIDITY');
+        uint amountInWithFee = amountIn.mul(997);
+        uint numerator = amountInWithFee.mul(reserveOut);
+        uint denominator = reserveIn.mul(1000).add(amountInWithFee);
+        amountOut = numerator / denominator;
+    }
+
+    // given an output amount of an asset and pair reserves, returns a required input amount of the other asset
+    function getAmountIn(uint amountOut, uint reserveIn, uint reserveOut) internal pure returns (uint amountIn) {
+        require(amountOut > 0, 'UniswapV2Library: INSUFFICIENT_OUTPUT_AMOUNT');
+        require(reserveIn > 0 && reserveOut > 0, 'UniswapV2Library: INSUFFICIENT_LIQUIDITY');
+        uint numerator = reserveIn.mul(amountOut).mul(1000);
+        uint denominator = reserveOut.sub(amountOut).mul(997);
+        amountIn = (numerator / denominator).add(1);
+    }
+
+    // performs chained getAmountOut calculations on any number of pairs
+    function getAmountsOut(address factory, uint amountIn, address[] memory path) internal view returns (uint[] memory amounts) {
+        require(path.length >= 2, 'UniswapV2Library: INVALID_PATH');
+        amounts = new uint[](path.length);
+        amounts[0] = amountIn;
+        for (uint i; i < path.length - 1; i++) {
+            (uint reserveIn, uint reserveOut) = getReserves(factory, path[i], path[i + 1]);
+            amounts[i + 1] = getAmountOut(amounts[i], reserveIn, reserveOut);
+        }
+    }
+
+    // performs chained getAmountIn calculations on any number of pairs
+    function getAmountsIn(address factory, uint amountOut, address[] memory path) internal view returns (uint[] memory amounts) {
+        require(path.length >= 2, 'UniswapV2Library: INVALID_PATH');
+        amounts = new uint[](path.length);
+        amounts[amounts.length - 1] = amountOut;
+        for (uint i = path.length - 1; i > 0; i--) {
+            (uint reserveIn, uint reserveOut) = getReserves(factory, path[i - 1], path[i]);
+            amounts[i - 1] = getAmountIn(amounts[i], reserveIn, reserveOut);
+        }
+    }
+}

contracts/v2-periphery/libraries/UniswapV2LiquidityMathLibrary.sol

+pragma solidity >=0.5.0;
+
+import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol';
+import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Factory.sol';
+import '@uniswap/lib/contracts/libraries/Babylonian.sol';
+import '@uniswap/lib/contracts/libraries/FullMath.sol';
+
+import './SafeMath.sol';
+import './UniswapV2Library.sol';
+
+// library containing some math for dealing with the liquidity shares of a pair, e.g. computing their exact value
+// in terms of the underlying tokens
+library UniswapV2LiquidityMathLibrary {
+    using SafeMath for uint256;
+
+    // computes the direction and magnitude of the profit-maximizing trade
+    function computeProfitMaximizingTrade(
+        uint256 truePriceTokenA,
+        uint256 truePriceTokenB,
+        uint256 reserveA,
+        uint256 reserveB
+    ) pure internal returns (bool aToB, uint256 amountIn) {
+        aToB = FullMath.mulDiv(reserveA, truePriceTokenB, reserveB) < truePriceTokenA;
+
+        uint256 invariant = reserveA.mul(reserveB);
+
+        uint256 leftSide = Babylonian.sqrt(
+            FullMath.mulDiv(
+                invariant.mul(1000),
+                aToB ? truePriceTokenA : truePriceTokenB,
+                (aToB ? truePriceTokenB : truePriceTokenA).mul(997)
+            )
+        );
+        uint256 rightSide = (aToB ? reserveA.mul(1000) : reserveB.mul(1000)) / 997;
+
+        if (leftSide < rightSide) return (false, 0);
+
+        // compute the amount that must be sent to move the price to the profit-maximizing price
+        amountIn = leftSide.sub(rightSide);
+    }
+
+    // gets the reserves after an arbitrage moves the price to the profit-maximizing ratio given an externally observed true price
+    function getReservesAfterArbitrage(
+        address factory,
+        address tokenA,
+        address tokenB,
+        uint256 truePriceTokenA,
+        uint256 truePriceTokenB
+    ) view internal returns (uint256 reserveA, uint256 reserveB) {
+        // first get reserves before the swap
+        (reserveA, reserveB) = UniswapV2Library.getReserves(factory, tokenA, tokenB);
+
+        require(reserveA > 0 && reserveB > 0, 'UniswapV2ArbitrageLibrary: ZERO_PAIR_RESERVES');
+
+        // then compute how much to swap to arb to the true price
+        (bool aToB, uint256 amountIn) = computeProfitMaximizingTrade(truePriceTokenA, truePriceTokenB, reserveA, reserveB);
+
+        if (amountIn == 0) {
+            return (reserveA, reserveB);
+        }
+
+        // now affect the trade to the reserves
+        if (aToB) {
+            uint amountOut = UniswapV2Library.getAmountOut(amountIn, reserveA, reserveB);
+            reserveA += amountIn;
+            reserveB -= amountOut;
+        } else {
+            uint amountOut = UniswapV2Library.getAmountOut(amountIn, reserveB, reserveA);
+            reserveB += amountIn;
+            reserveA -= amountOut;
+        }
+    }
+
+    // computes liquidity value given all the parameters of the pair
+    function computeLiquidityValue(
+        uint256 reservesA,
+        uint256 reservesB,
+        uint256 totalSupply,
+        uint256 liquidityAmount,
+        bool feeOn,
+        uint kLast
+    ) internal pure returns (uint256 tokenAAmount, uint256 tokenBAmount) {
+        if (feeOn && kLast > 0) {
+            uint rootK = Babylonian.sqrt(reservesA.mul(reservesB));
+            uint rootKLast = Babylonian.sqrt(kLast);
+            if (rootK > rootKLast) {
+                uint numerator1 = totalSupply;
+                uint numerator2 = rootK.sub(rootKLast);
+                uint denominator = rootK.mul(5).add(rootKLast);
+                uint feeLiquidity = FullMath.mulDiv(numerator1, numerator2, denominator);
+                totalSupply = totalSupply.add(feeLiquidity);
+            }
+        }
+        return (reservesA.mul(liquidityAmount) / totalSupply, reservesB.mul(liquidityAmount) / totalSupply);
+    }
+
+    // get all current parameters from the pair and compute value of a liquidity amount
+    // **note this is subject to manipulation, e.g. sandwich attacks**. prefer passing a manipulation resistant price to
+    // #getLiquidityValueAfterArbitrageToPrice
+    function getLiquidityValue(
+        address factory,
+        address tokenA,
+        address tokenB,
+        uint256 liquidityAmount
+    ) internal view returns (uint256 tokenAAmount, uint256 tokenBAmount) {
+        (uint256 reservesA, uint256 reservesB) = UniswapV2Library.getReserves(factory, tokenA, tokenB);
+        IUniswapV2Pair pair = IUniswapV2Pair(UniswapV2Library.pairFor(factory, tokenA, tokenB));
+        bool feeOn = IUniswapV2Factory(factory).feeTo() != address(0);
+        uint kLast = feeOn ? pair.kLast() : 0;
+        uint totalSupply = pair.totalSupply();
+        return computeLiquidityValue(reservesA, reservesB, totalSupply, liquidityAmount, feeOn, kLast);
+    }
+
+    // given two tokens, tokenA and tokenB, and their "true price", i.e. the observed ratio of value of token A to token B,
+    // and a liquidity amount, returns the value of the liquidity in terms of tokenA and tokenB
+    function getLiquidityValueAfterArbitrageToPrice(
+        address factory,
+        address tokenA,
+        address tokenB,
+        uint256 truePriceTokenA,
+        uint256 truePriceTokenB,
+        uint256 liquidityAmount
+    ) internal view returns (
+        uint256 tokenAAmount,
+        uint256 tokenBAmount
+    ) {
+        bool feeOn = IUniswapV2Factory(factory).feeTo() != address(0);
+        IUniswapV2Pair pair = IUniswapV2Pair(UniswapV2Library.pairFor(factory, tokenA, tokenB));
+        uint kLast = feeOn ? pair.kLast() : 0;
+        uint totalSupply = pair.totalSupply();
+
+        // this also checks that totalSupply > 0
+        require(totalSupply >= liquidityAmount && liquidityAmount > 0, 'ComputeLiquidityValue: LIQUIDITY_AMOUNT');
+
+        (uint reservesA, uint reservesB) = getReservesAfterArbitrage(factory, tokenA, tokenB, truePriceTokenA, truePriceTokenB);
+
+        return computeLiquidityValue(reservesA, reservesB, totalSupply, liquidityAmount, feeOn, kLast);
+    }
+}

contracts/v2-periphery/libraries/UniswapV2OracleLibrary.sol

+pragma solidity >=0.5.0;
+
+import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol';
+import '@uniswap/lib/contracts/libraries/FixedPoint.sol';
+
+// library with helper methods for oracles that are concerned with computing average prices
+library UniswapV2OracleLibrary {
+    using FixedPoint for *;
+
+    // helper function that returns the current block timestamp within the range of uint32, i.e. [0, 2**32 - 1]
+    function currentBlockTimestamp() internal view returns (uint32) {
+        return uint32(block.timestamp % 2 ** 32);
+    }
+
+    // produces the cumulative price using counterfactuals to save gas and avoid a call to sync.
+    function currentCumulativePrices(
+        address pair
+    ) internal view returns (uint price0Cumulative, uint price1Cumulative, uint32 blockTimestamp) {
+        blockTimestamp = currentBlockTimestamp();
+        price0Cumulative = IUniswapV2Pair(pair).price0CumulativeLast();
+        price1Cumulative = IUniswapV2Pair(pair).price1CumulativeLast();
+
+        // if time has elapsed since the last update on the pair, mock the accumulated price values
+        (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast) = IUniswapV2Pair(pair).getReserves();
+        if (blockTimestampLast != blockTimestamp) {
+            // subtraction overflow is desired
+            uint32 timeElapsed = blockTimestamp - blockTimestampLast;
+            // addition overflow is desired
+            // counterfactual
+            price0Cumulative += uint(FixedPoint.fraction(reserve1, reserve0)._x) * timeElapsed;
+            // counterfactual
+            price1Cumulative += uint(FixedPoint.fraction(reserve0, reserve1)._x) * timeElapsed;
+        }
+    }
+}

contracts/v2-periphery/test/DeflatingERC20.sol

+pragma solidity =0.6.6;
+
+import '../libraries/SafeMath.sol';
+
+contract DeflatingERC20 {
+    using SafeMath for uint;
+
+    string public constant name = 'Deflating Test Token';
+    string public constant symbol = 'DTT';
+    uint8 public constant decimals = 18;
+    uint  public totalSupply;
+    mapping(address => uint) public balanceOf;
+    mapping(address => mapping(address => uint)) public allowance;
+
+    bytes32 public DOMAIN_SEPARATOR;
+    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
+    bytes32 public constant PERMIT_TYPEHASH = 0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;
+    mapping(address => uint) public nonces;
+
+    event Approval(address indexed owner, address indexed spender, uint value);
+    event Transfer(address indexed from, address indexed to, uint value);
+
+    constructor(uint _totalSupply) public {
+        uint chainId;
+        assembly {
+            chainId := chainid()
+        }
+        DOMAIN_SEPARATOR = keccak256(
+            abi.encode(
+                keccak256('EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)'),
+                keccak256(bytes(name)),
+                keccak256(bytes('1')),
+                chainId,
+                address(this)
+            )
+        );
+        _mint(msg.sender, _totalSupply);
+    }
+
+    function _mint(address to, uint value) internal {
+        totalSupply = totalSupply.add(value);
+        balanceOf[to] = balanceOf[to].add(value);
+        emit Transfer(address(0), to, value);
+    }
+
+    function _burn(address from, uint value) internal {
+        balanceOf[from] = balanceOf[from].sub(value);
+        totalSupply = totalSupply.sub(value);
+        emit Transfer(from, address(0), value);
+    }
+
+    function _approve(address owner, address spender, uint value) private {
+        allowance[owner][spender] = value;
+        emit Approval(owner, spender, value);
+    }
+
+    function _transfer(address from, address to, uint value) private {
+        uint burnAmount = value / 100;
+        _burn(from, burnAmount);
+        uint transferAmount = value.sub(burnAmount);
+        balanceOf[from] = balanceOf[from].sub(transferAmount);
+        balanceOf[to] = balanceOf[to].add(transferAmount);
+        emit Transfer(from, to, transferAmount);
+    }
+
+    function approve(address spender, uint value) external returns (bool) {
+        _approve(msg.sender, spender, value);
+        return true;
+    }
+
+    function transfer(address to, uint value) external returns (bool) {
+        _transfer(msg.sender, to, value);
+        return true;
+    }
+
+    function transferFrom(address from, address to, uint value) external returns (bool) {
+        if (allowance[from][msg.sender] != uint(-1)) {
+            allowance[from][msg.sender] = allowance[from][msg.sender].sub(value);
+        }
+        _transfer(from, to, value);
+        return true;
+    }
+
+    function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external {
+        require(deadline >= block.timestamp, '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, 'INVALID_SIGNATURE');
+        _approve(owner, spender, value);
+    }
+}

contracts/v2-periphery/test/ERC20.sol

+pragma solidity =0.6.6;
+
+import '../libraries/SafeMath.sol';
+
+contract ERC20 {
+    using SafeMath for uint;
+
+    string public constant name = 'Test Token';
+    string public constant symbol = 'TT';
+    uint8 public constant decimals = 18;
+    uint  public totalSupply;
+    mapping(address => uint) public balanceOf;
+    mapping(address => mapping(address => uint)) public allowance;
+
+    bytes32 public DOMAIN_SEPARATOR;
+    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
+    bytes32 public constant PERMIT_TYPEHASH = 0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;
+    mapping(address => uint) public nonces;
+
+    event Approval(address indexed owner, address indexed spender, uint value);
+    event Transfer(address indexed from, address indexed to, uint value);
+
+    constructor(uint _totalSupply) public {
+        uint chainId;
+        assembly {
+            chainId := chainid()
+        }
+        DOMAIN_SEPARATOR = keccak256(
+            abi.encode(
+                keccak256('EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)'),
+                keccak256(bytes(name)),
+                keccak256(bytes('1')),
+                chainId,
+                address(this)
+            )
+        );
+        _mint(msg.sender, _totalSupply);
+    }
+
+    function _mint(address to, uint value) internal {
+        totalSupply = totalSupply.add(value);
+        balanceOf[to] = balanceOf[to].add(value);
+        emit Transfer(address(0), to, value);
+    }
+
+    function _burn(address from, uint value) internal {
+        balanceOf[from] = balanceOf[from].sub(value);
+        totalSupply = totalSupply.sub(value);
+        emit Transfer(from, address(0), value);
+    }
+
+    function _approve(address owner, address spender, uint value) private {
+        allowance[owner][spender] = value;
+        emit Approval(owner, spender, value);
+    }
+
+    function _transfer(address from, address to, uint value) private {
+        balanceOf[from] = balanceOf[from].sub(value);
+        balanceOf[to] = balanceOf[to].add(value);
+        emit Transfer(from, to, value);
+    }
+
+    function approve(address spender, uint value) external returns (bool) {
+        _approve(msg.sender, spender, value);
+        return true;
+    }
+
+    function transfer(address to, uint value) external returns (bool) {
+        _transfer(msg.sender, to, value);
+        return true;
+    }
+
+    function transferFrom(address from, address to, uint value) external returns (bool) {
+        if (allowance[from][msg.sender] != uint(-1)) {
+            allowance[from][msg.sender] = allowance[from][msg.sender].sub(value);
+        }
+        _transfer(from, to, value);
+        return true;
+    }
+
+    function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external {
+        require(deadline >= block.timestamp, '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, 'INVALID_SIGNATURE');
+        _approve(owner, spender, value);
+    }
+}

contracts/v2-periphery/test/RouterEventEmitter.sol

+pragma solidity =0.6.6;
+
+import '../interfaces/IUniswapV2Router01.sol';
+
+contract RouterEventEmitter {
+    event Amounts(uint[] amounts);
+
+    receive() external payable {}
+
+    function swapExactTokensForTokens(
+        address router,
+        uint amountIn,
+        uint amountOutMin,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external {
+        (bool success, bytes memory returnData) = router.delegatecall(abi.encodeWithSelector(
+            IUniswapV2Router01(router).swapExactTokensForTokens.selector, amountIn, amountOutMin, path, to, deadline
+        ));
+        assert(success);
+        emit Amounts(abi.decode(returnData, (uint[])));
+    }
+
+    function swapTokensForExactTokens(
+        address router,
+        uint amountOut,
+        uint amountInMax,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external {
+        (bool success, bytes memory returnData) = router.delegatecall(abi.encodeWithSelector(
+            IUniswapV2Router01(router).swapTokensForExactTokens.selector, amountOut, amountInMax, path, to, deadline
+        ));
+        assert(success);
+        emit Amounts(abi.decode(returnData, (uint[])));
+    }
+
+    function swapExactETHForTokens(
+        address router,
+        uint amountOutMin,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external payable {
+        (bool success, bytes memory returnData) = router.delegatecall(abi.encodeWithSelector(
+            IUniswapV2Router01(router).swapExactETHForTokens.selector, amountOutMin, path, to, deadline
+        ));
+        assert(success);
+        emit Amounts(abi.decode(returnData, (uint[])));
+    }
+
+    function swapTokensForExactETH(
+        address router,
+        uint amountOut,
+        uint amountInMax,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external {
+        (bool success, bytes memory returnData) = router.delegatecall(abi.encodeWithSelector(
+            IUniswapV2Router01(router).swapTokensForExactETH.selector, amountOut, amountInMax, path, to, deadline
+        ));
+        assert(success);
+        emit Amounts(abi.decode(returnData, (uint[])));
+    }
+
+    function swapExactTokensForETH(
+        address router,
+        uint amountIn,
+        uint amountOutMin,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external {
+        (bool success, bytes memory returnData) = router.delegatecall(abi.encodeWithSelector(
+            IUniswapV2Router01(router).swapExactTokensForETH.selector, amountIn, amountOutMin, path, to, deadline
+        ));
+        assert(success);
+        emit Amounts(abi.decode(returnData, (uint[])));
+    }
+
+    function swapETHForExactTokens(
+        address router,
+        uint amountOut,
+        address[] calldata path,
+        address to,
+        uint deadline
+    ) external payable {
+        (bool success, bytes memory returnData) = router.delegatecall(abi.encodeWithSelector(
+            IUniswapV2Router01(router).swapETHForExactTokens.selector, amountOut, path, to, deadline
+        ));
+        assert(success);
+        emit Amounts(abi.decode(returnData, (uint[])));
+    }
+}

contracts/v2-periphery/test/WETH9.sol

+// Copyright (C) 2015, 2016, 2017 Dapphub
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+pragma solidity =0.6.6;
+
+contract WETH9 {
+    string public name     = "Wrapped Ether";
+    string public symbol   = "WETH";
+    uint8  public decimals = 18;
+
+    event  Approval(address indexed src, address indexed guy, uint wad);
+    event  Transfer(address indexed src, address indexed dst, uint wad);
+    event  Deposit(address indexed dst, uint wad);
+    event  Withdrawal(address indexed src, uint wad);
+
+    mapping (address => uint)                       public  balanceOf;
+    mapping (address => mapping (address => uint))  public  allowance;
+
+    // function() public payable {
+    //     deposit();
+    // }
+    function deposit() public payable {
+        balanceOf[msg.sender] += msg.value;
+        emit Deposit(msg.sender, msg.value);
+    }
+    function withdraw(uint wad) public {
+        require(balanceOf[msg.sender] >= wad, "");
+        balanceOf[msg.sender] -= wad;
+        msg.sender.transfer(wad);
+        emit Withdrawal(msg.sender, wad);
+    }
+
+    function totalSupply() public view returns (uint) {
+        return address(this).balance;
+    }
+
+    function approve(address guy, uint wad) public returns (bool) {
+        allowance[msg.sender][guy] = wad;
+        emit Approval(msg.sender, guy, wad);
+        return true;
+    }
+
+    function transfer(address dst, uint wad) public returns (bool) {
+        return transferFrom(msg.sender, dst, wad);
+    }
+
+    function transferFrom(address src, address dst, uint wad)
+        public
+        returns (bool)
+    {
+        require(balanceOf[src] >= wad, "");
+
+        if (src != msg.sender && allowance[src][msg.sender] != uint(-1)) {
+            require(allowance[src][msg.sender] >= wad, "");
+            allowance[src][msg.sender] -= wad;
+        }
+
+        balanceOf[src] -= wad;
+        balanceOf[dst] += wad;
+
+        emit Transfer(src, dst, wad);
+
+        return true;
+    }
+}
+
+
+/*
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The GNU General Public License is a free, copyleft license for
+software and other kinds of works.
+
+  The licenses for most software and other practical works are designed
+to take away your freedom to share and change the works.  By contrast,
+the GNU General Public License is intended to guarantee your freedom to
+share and change all versions of a program--to make sure it remains free
+software for all its users.  We, the Free Software Foundation, use the
+GNU General Public License for most of our software; it applies also to
+any other work released this way by its authors.  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
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+
+  To protect your rights, we need to prevent others from denying you
+these rights or asking you to surrender the rights.  Therefore, you have
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+you modify it: responsibilities to respect the freedom of others.
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+
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+
+*/
\ No newline at end of file

hardhat.config.js

+require("@nomicfoundation/hardhat-toolbox");
+// dotenv
+require("dotenv").config();
+
+/** @type import('hardhat/config').HardhatUserConfig */
+module.exports = {
+  solidity: {
+    compilers: [
+      {
+        version: "0.5.16",
+        settings: {
+          optimizer: {
+            enabled: true,
+            runs: 200,
+          },
+        },
+      },
+      {
+        version: "0.6.6",
+        settings: {
+          optimizer: {
+            enabled: true,
+            runs: 200,
+          },
+        },
+      },
+    ],
+  },
+  networks: {
+    holesky: {
+      chainId: 17000,
+      url: "https://1rpc.io/holesky",
+      accounts: [process.env.PRIVATE_KEY],
+    },
+  },
+};

ignition/modules/v2dex.js

+// This setup uses Hardhat Ignition to manage smart contract deployments.
+// Learn more about it at https://hardhat.org/ignition
+
+const { buildModule } = require("@nomicfoundation/hardhat-ignition/modules");
+
+require("dotenv").config();
+
+module.exports = buildModule("UniswapV2Dex", (m) => {
+
+  const deployer = m.getAccount(0);
+
+  // 部署 factory
+  const factory = m.contract("UniswapV2Factory", [deployer]);
+
+  const WETH = process.env.WETH;
+
+  // 部署router
+  const router = m.contract("UniswapV2Router02", [factory, WETH]);
+
+  return { factory, router };
+});

package.json

+{
+  "name": "hardhat-project",
+  "devDependencies": {
+    "@nomicfoundation/hardhat-ignition-ethers": "^0.15.14",
+    "@nomicfoundation/hardhat-toolbox": "^6.1.0",
+    "hardhat": "^2.26.1"
+  },
+  "dependencies": {
+    "@openzeppelin/contracts": "^5.4.0",
+    "@uniswap/lib": "^4.0.1-alpha",
+    "@uniswap/v2-core": "^1.0.1",
+    "dotenv": "^17.2.1"
+  }
+}

test/Lock.js

+const {
+  time,
+  loadFixture,
+} = require("@nomicfoundation/hardhat-toolbox/network-helpers");
+const { anyValue } = require("@nomicfoundation/hardhat-chai-matchers/withArgs");
+const { expect } = require("chai");
+
+describe("Lock", function () {
+  // We define a fixture to reuse the same setup in every test.
+  // We use loadFixture to run this setup once, snapshot that state,
+  // and reset Hardhat Network to that snapshot in every test.
+  async function deployOneYearLockFixture() {
+    const ONE_YEAR_IN_SECS = 365 * 24 * 60 * 60;
+    const ONE_GWEI = 1_000_000_000;
+
+    const lockedAmount = ONE_GWEI;
+    const unlockTime = (await time.latest()) + ONE_YEAR_IN_SECS;
+
+    // Contracts are deployed using the first signer/account by default
+    const [owner, otherAccount] = await ethers.getSigners();
+
+    const Lock = await ethers.getContractFactory("Lock");
+    const lock = await Lock.deploy(unlockTime, { value: lockedAmount });
+
+    return { lock, unlockTime, lockedAmount, owner, otherAccount };
+  }
+
+  describe("Deployment", function () {
+    it("Should set the right unlockTime", async function () {
+      const { lock, unlockTime } = await loadFixture(deployOneYearLockFixture);
+
+      expect(await lock.unlockTime()).to.equal(unlockTime);
+    });
+
+    it("Should set the right owner", async function () {
+      const { lock, owner } = await loadFixture(deployOneYearLockFixture);
+
+      expect(await lock.owner()).to.equal(owner.address);
+    });
+
+    it("Should receive and store the funds to lock", async function () {
+      const { lock, lockedAmount } = await loadFixture(
+        deployOneYearLockFixture
+      );
+
+      expect(await ethers.provider.getBalance(lock.target)).to.equal(
+        lockedAmount
+      );
+    });
+
+    it("Should fail if the unlockTime is not in the future", async function () {
+      // We don't use the fixture here because we want a different deployment
+      const latestTime = await time.latest();
+      const Lock = await ethers.getContractFactory("Lock");
+      await expect(Lock.deploy(latestTime, { value: 1 })).to.be.revertedWith(
+        "Unlock time should be in the future"
+      );
+    });
+  });
+
+  describe("Withdrawals", function () {
+    describe("Validations", function () {
+      it("Should revert with the right error if called too soon", async function () {
+        const { lock } = await loadFixture(deployOneYearLockFixture);
+
+        await expect(lock.withdraw()).to.be.revertedWith(
+          "You can't withdraw yet"
+        );
+      });
+
+      it("Should revert with the right error if called from another account", async function () {
+        const { lock, unlockTime, otherAccount } = await loadFixture(
+          deployOneYearLockFixture
+        );
+
+        // We can increase the time in Hardhat Network
+        await time.increaseTo(unlockTime);
+
+        // We use lock.connect() to send a transaction from another account
+        await expect(lock.connect(otherAccount).withdraw()).to.be.revertedWith(
+          "You aren't the owner"
+        );
+      });
+
+      it("Shouldn't fail if the unlockTime has arrived and the owner calls it", async function () {
+        const { lock, unlockTime } = await loadFixture(
+          deployOneYearLockFixture
+        );
+
+        // Transactions are sent using the first signer by default
+        await time.increaseTo(unlockTime);
+
+        await expect(lock.withdraw()).not.to.be.reverted;
+      });
+    });
+
+    describe("Events", function () {
+      it("Should emit an event on withdrawals", async function () {
+        const { lock, unlockTime, lockedAmount } = await loadFixture(
+          deployOneYearLockFixture
+        );
+
+        await time.increaseTo(unlockTime);
+
+        await expect(lock.withdraw())
+          .to.emit(lock, "Withdrawal")
+          .withArgs(lockedAmount, anyValue); // We accept any value as `when` arg
+      });
+    });
+
+    describe("Transfers", function () {
+      it("Should transfer the funds to the owner", async function () {
+        const { lock, unlockTime, lockedAmount, owner } = await loadFixture(
+          deployOneYearLockFixture
+        );
+
+        await time.increaseTo(unlockTime);
+
+        await expect(lock.withdraw()).to.changeEtherBalances(
+          [owner, lock],
+          [lockedAmount, -lockedAmount]
+        );
+      });
+    });
+  });
+});