pragma solidity ^0.6.12;



interface IWETH {
    function deposit() external payable;
    function transfer(address to, uint value) external returns (bool);
    function withdraw(uint) external;
}

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    function totalSupply() external view returns (uint256);
    function balanceOf(address account) external view returns (uint256);
    function transfer(address recipient, uint256 amount) external returns (bool);
    function allowance(address owner, address spender) external view returns (uint256);
    function approve(address spender, uint256 amount) external returns (bool);
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

interface IBPool {

    function isPublicSwap() external view returns (bool);
    function isFinalized() external view returns (bool);
    function isBound(address t) external view returns (bool);
    function getNumTokens() external view returns (uint);
    function getCurrentTokens() external view returns (address[] memory tokens);
    function getFinalTokens() external view returns (address[] memory tokens);
    function getDenormalizedWeight(address token) external view returns (uint);
    function getTotalDenormalizedWeight() external view returns (uint);
    function getNormalizedWeight(address token) external view returns (uint);
    function getBalance(address token) external view returns (uint);
    function getSwapFee() external view returns (uint);
    function getController() external view returns (address);
    
    function setSwapFee(uint swapFee) external;
    function setController(address manager) external;
    function setPublicSwap(bool public_) external;
    function finalize() external;
    function bind(address token, uint balance, uint denorm) external;
    function rebind(address token, uint balance, uint denorm) external;
    function unbind(address token) external;
    function gulp(address token) external;

    function getSpotPrice(address tokenIn, address tokenOut) external view returns (uint spotPrice);
    function getSpotPriceSansFee(address tokenIn, address tokenOut) external view returns (uint spotPrice);

    function joinPool(uint poolAmountOut, uint[] calldata maxAmountsIn) external;   
    function exitPool(uint poolAmountIn, uint[] calldata minAmountsOut) external;

    function swapExactAmountIn(
        address tokenIn,
        uint tokenAmountIn,
        address tokenOut,
        uint minAmountOut,
        uint maxPrice
    ) external returns (uint tokenAmountOut, uint spotPriceAfter);
    
    function swapExactAmountOut(
        address tokenIn,
        uint maxAmountIn,
        address tokenOut,
        uint tokenAmountOut,
        uint maxPrice
    ) external returns (uint tokenAmountIn, uint spotPriceAfter);

    function joinswapExternAmountIn(
        address tokenIn,
        uint tokenAmountIn,
        uint minPoolAmountOut
    ) external returns (uint poolAmountOut);

    function joinswapPoolAmountOut(
        address tokenIn,
        uint poolAmountOut,
        uint maxAmountIn
    ) external returns (uint tokenAmountIn);
    
    function exitswapPoolAmountIn(
        address tokenOut,
        uint poolAmountIn,
        uint minAmountOut
    ) external returns (uint tokenAmountOut);

    function exitswapExternAmountOut(
        address tokenOut,
        uint tokenAmountOut,
        uint maxPoolAmountIn
    ) external returns (uint poolAmountIn);
    
    function totalSupply() external view returns (uint);
    function balanceOf(address whom) external view returns (uint);
    function allowance(address src, address dst) external view returns (uint);

    function approve(address dst, uint amt) external returns (bool);
    function transfer(address dst, uint amt) external returns (bool);
    function transferFrom(
        address src, address dst, uint amt
    ) external returns (bool);
    
    function calcSpotPrice(
        uint tokenBalanceIn,
        uint tokenWeightIn,
        uint tokenBalanceOut,
        uint tokenWeightOut,
        uint swapFee
    ) external pure returns (uint spotPrice);
    
    function calcOutGivenIn(
        uint tokenBalanceIn,
        uint tokenWeightIn,
        uint tokenBalanceOut,
        uint tokenWeightOut,
        uint tokenAmountIn,
        uint swapFee
    ) external pure returns (uint tokenAmountOut);
    
    function calcInGivenOut(
        uint tokenBalanceIn,
        uint tokenWeightIn,
        uint tokenBalanceOut,
        uint tokenWeightOut,
        uint tokenAmountOut,
        uint swapFee
    ) external pure returns (uint tokenAmountIn);
    
    function calcPoolOutGivenSingleIn(
        uint tokenBalanceIn,
        uint tokenWeightIn,
        uint poolSupply,
        uint totalWeight,
        uint tokenAmountIn,
        uint swapFee
    ) external pure returns (uint poolAmountOut);
    
    function calcSingleInGivenPoolOut(
        uint tokenBalanceIn,
        uint tokenWeightIn,
        uint poolSupply,
        uint totalWeight,
        uint poolAmountOut,
        uint swapFee
    ) external pure returns (uint tokenAmountIn);
    
    function calcSingleOutGivenPoolIn(
        uint tokenBalanceOut,
        uint tokenWeightOut,
        uint poolSupply,
        uint totalWeight,
        uint poolAmountIn,
        uint swapFee
    ) external pure returns (uint tokenAmountOut);
    
    function calcPoolInGivenSingleOut(
        uint tokenBalanceOut,
        uint tokenWeightOut,
        uint poolSupply,
        uint totalWeight,
        uint tokenAmountOut,
        uint swapFee
    ) external pure returns (uint poolAmountIn);

}


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;
}



/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 */
library SafeMath {

    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }

    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;
        }
    }
}




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);
        }
    }
}

contract BalancerZAP {

    using SafeMath for uint256;

    address public _token;
    address public _balancerPool;
    address public _tokenWETHPair;
    IWETH public _WETH;
    bool private initialized;

    function initBalancerZAP(address token, address balancerPool, address WETH, address tokenWethPair) public  {
        require(!initialized);
        _token = token;
        _balancerPool = balancerPool;
        require(IERC20(_token).approve(balancerPool, uint(-1)));
        _WETH = IWETH(WETH);
        _tokenWETHPair = tokenWethPair;
        initialized = true;
    }

    fallback() external payable {
        if(msg.sender != address(_WETH)){
             addLiquidityETHOnly(msg.sender);
        }
    }
    receive() external payable {
        if(msg.sender != address(_WETH)){
             addLiquidityETHOnly(msg.sender);
        }
    }

    function addLiquidityETHOnly(address payable to) public payable {
        require(to != address(0), "Invalid address");

        uint256 buyAmount = msg.value;
        require(buyAmount > 0, "Insufficient ETH amount");
        _WETH.deposit{value : msg.value}();

        (uint256 reserveWeth, uint256 reserveTokens) = getPairReserves();
        uint256 outTokens = UniswapV2Library.getAmountOut(buyAmount, reserveWeth, reserveTokens);
        
        _WETH.transfer(_tokenWETHPair, buyAmount);

        (address token0, address token1) = UniswapV2Library.sortTokens(address(_WETH), _token);
        IUniswapV2Pair(_tokenWETHPair).swap(_token == token0 ? outTokens : 0, _token == token1 ? outTokens : 0, address(this), "");

        _addLiquidity(outTokens, to);

    }

    function addLiquidityTokenOnly(uint256 tokenAmount, address payable to) public payable {
        require(to != address(0), "Invalid address");
        require(tokenAmount > 0, "Insufficient token amount");

        require(IERC20(_token).transferFrom(msg.sender, address(this), tokenAmount)); 
        _addLiquidity(tokenAmount, to);

    }

    function _addLiquidity(uint256 tokenAmount, address payable to) internal {

        //mint BPTs 
        uint256 bptTokens = IBPool(_balancerPool).joinswapExternAmountIn( _token, tokenAmount, 0);
        require(bptTokens > 0, "Insufficient BPT amount");
    
        //transfer tokens to user
        require(IBPool(_balancerPool).transfer(to, bptTokens));

    }

    function getPairReserves() internal view returns (uint256 wethReserves, uint256 tokenReserves) {
        (address token0,) = UniswapV2Library.sortTokens(address(_WETH), _token);
        (uint256 reserve0, uint reserve1,) = IUniswapV2Pair(_tokenWETHPair).getReserves();
        (wethReserves, tokenReserves) = token0 == _token ? (reserve1, reserve0) : (reserve0, reserve1);
    }


}