// File: contracts/oracle/uniswap/UniswapOracleTWAPCompare.sol



// SPDX-License-Identifier: GNU

/// @notice adapted from https://github.com/Uniswap/uniswap-v2-periphery/blob/master/contracts/examples/ExampleOracleSimple.sol

pragma solidity 0.7.6;

import "../OracleCommon.sol";
import "../../_openzeppelin/math/SafeMath.sol";
import '../../_uniswap/v2-core/contracts/interfaces/IUniswapV2Factory.sol';
import '../../_uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol';
import '../../_uniswap/lib/contracts/libraries/FixedPoint.sol';
import '../../_uniswap/v2-periphery/contracts/libraries/UniswapV2OracleLibrary.sol';
import '../../_uniswap/v2-periphery/contracts/libraries/UniswapV2Library.sol';

/**
 @notice A oracle that uses 2 TWAP periods and uses the lower of the 2 values.  
 Note that the price average is only guaranteed to be over at least 1 period, but may be over a longer period,
 Periodicity is fixed at deployment time. Index (usually USD) token is fixed at deployment time.
 A single deployment can be shared by multiple oneToken clients and can observe multiple base tokens.
 Non-USD index tokens are possible. Such deployments can used as interim oracles in Composite Oracles. They should
 NOT be registered because they are not, by definition, valid sources of USD quotes.  
 Example calculation MPH/ETH -> ETH/USD 1hr and MPH/ETH -> ETH/USD 24hr take the lower value and return.  This is a safety net to help 
 prevent price manipulation.  This oracle combines 2 TWAPs to save on gas for keeping seperate oracles for these 2 PERIODS.
 */

contract UniswapOracleTWAPCompare is OracleCommon {
    using FixedPoint for *;
    using SafeMath for uint256;

    uint256 public immutable PERIOD_1;
    uint256 public immutable PERIOD_2;

    address public immutable uniswapFactory;

    struct Pair {
        address token0;
        address token1;
        uint256 price0CumulativeLast;
        uint256 price1CumulativeLast;
        uint32  blockTimestampLast;
        FixedPoint.uq112x112 price0Average;
        FixedPoint.uq112x112 price1Average;
    }

    mapping(address => Pair) period_1_pairs;
    mapping(address => Pair) period_2_pairs;

    /**
     @notice the indexToken (index token), averaging period and uniswapfactory cannot be changed post-deployment
     @dev deploy multiple instances to support different configurations
     @param oneTokenFactory_ oneToken factory to bind to
     @param uniswapFactory_ external factory contract needed by the uniswap library
     @param indexToken_ the index token to use for valuations. If not a usd collateral token then the Oracle should not be registered in the factory but it can be used by CompositeOracles.
     @param period_1_ the averaging period to use for price smoothing
     @param period_2_ the averaging period to use for price smoothing
     */
    constructor(address oneTokenFactory_, address uniswapFactory_, address indexToken_, uint256 period_1_, uint256 period_2_)
        OracleCommon(oneTokenFactory_, "ICHI TWAP Compare Uniswap Oracle", indexToken_)
    {
        require(uniswapFactory_ != NULL_ADDRESS, "UniswapOracleTWAPCompare: uniswapFactory cannot be empty");
        require(period_1_ > 0, "UniswapOracleTWAPCompare: period must be > 0");
        require(period_2_ > 0, "UniswapOracleTWAPCompare: period must be > 0");
        uniswapFactory = uniswapFactory_;
        PERIOD_1 = period_1_;
        PERIOD_2 = period_2_;
        indexToken = indexToken_;
    }

    /**
     @notice configures parameters for a pair, token versus indexToken
     @dev initializes the first time, then does no work. Initialized from the Factory when assigned to an asset.
     @param token the base token. index is established at deployment time and cannot be changed
     */
    function init(address token) external onlyModuleOrFactory override {
        require(token != NULL_ADDRESS, "UniswapOracleTWAPCompare: token cannot be null");
        IUniswapV2Pair _pair = IUniswapV2Pair(UniswapV2Library.pairFor(uniswapFactory, token, indexToken));
        // this condition should never be false
        require(address(_pair) != NULL_ADDRESS, "UniswapOracleTWAPCompare: unknown pair");
        Pair storage p1 = period_1_pairs[address(_pair)];
        Pair storage p2 = period_2_pairs[address(_pair)];
        if(p1.token0 == NULL_ADDRESS && p2.token0 == NULL_ADDRESS) {
            p1.token0 = _pair.token0();
            p2.token0 = _pair.token0();
            p1.token1 = _pair.token1();
            p2.token1 = _pair.token1();
            p1.price0CumulativeLast = _pair.price0CumulativeLast(); // fetch the current accumulated price value (1 / 0)
            p2.price0CumulativeLast = _pair.price0CumulativeLast();
            p1.price1CumulativeLast = _pair.price1CumulativeLast(); // fetch the current accumulated price value (0 / 1)
            p2.price1CumulativeLast = _pair.price1CumulativeLast();
            uint112 reserve0;
            uint112 reserve1;
            (reserve0, reserve1, p1.blockTimestampLast) = _pair.getReserves();
            p2.blockTimestampLast = p1.blockTimestampLast;
            require(reserve0 != 0 && reserve1 != 0, 'UniswapOracleTWAPCompare: NO_RESERVES'); // ensure that there's liquidity in the pair
            emit OracleInitialized(msg.sender, token, indexToken);
        }
    }

    /**
     @notice returns equivalent indexTokens for amountIn, token
     @dev index token is established at deployment time
     @param token ERC20 token
     @param amountTokens quantity, token precision
     @param amountUsd US dollar equivalent, precision 18
     @param volatility metric for future use-cases 
     */
    function read(address token, uint256 amountTokens) external view override returns(uint256 amountUsd, uint256 volatility) {
        amountUsd = tokensToNormalized(indexToken, consult(token, amountTokens));
        volatility = 1;
    }

    /**
     @notice returns equivalent baseTokens for amountUsd, indexToken
     @dev index token is established at deployment time
     @param token ERC20 token
     @param amountTokens quantity, token precision
     @param amountUsd US dollar equivalent, precision 18
     @param volatility metric for future use-cases
     */
    function amountRequired(address token, uint256 amountUsd) external view override returns(uint256 amountTokens, uint256 volatility) {
        IUniswapV2Pair _pair = IUniswapV2Pair(UniswapV2Library.pairFor(uniswapFactory, token, indexToken));
        Pair storage p1 = period_1_pairs[address(_pair)];
        Pair storage p2 = period_2_pairs[address(_pair)];
        require(token == p1.token0 || token == p1.token1, 'UniswapOracleTWAPCompare: INVALID_TOKEN');
        require(p1.price0CumulativeLast > 0 && p2.price0CumulativeLast > 0, "UniswapOracleTWAPCompare: Gathering history. Try again later");
        amountUsd = normalizedToTokens(indexToken, amountUsd);
        uint256 p1Tokens = (token == p1.token0 ? p1.price0Average : p1.price1Average).reciprocal().mul(amountUsd).decode144();
        uint256 p2Tokens = (token == p2.token0 ? p2.price0Average : p2.price1Average).reciprocal().mul(amountUsd).decode144();
        if (p1Tokens > p2Tokens) {  //want to take the lower price which is more larger amount of tokens
            amountTokens = p1Tokens;
        } else {
            amountTokens = p2Tokens;
        }
        volatility = 1;
    }

    /**
     @notice updates price observation history, if necessary
     @dev it is permissible for anyone to supply gas and update the oracle's price history.
     @param token baseToken to update
     */
    function update(address token) external override {
        IUniswapV2Pair _pair = IUniswapV2Pair(UniswapV2Library.pairFor(uniswapFactory, token, indexToken));
        Pair storage p1 = period_1_pairs[address(_pair)];
        Pair storage p2 = period_2_pairs[address(_pair)];
        if(p1.token0 != NULL_ADDRESS) {
            (uint256 price0Cumulative, uint256 price1Cumulative, uint32 blockTimestamp) =
                UniswapV2OracleLibrary.currentCumulativePrices(address(_pair));
            uint32 timeElapsed_1 = blockTimestamp - p1.blockTimestampLast; // overflow is desired
            uint32 timeElapsed_2 = blockTimestamp - p2.blockTimestampLast; // overflow is desired

            // ensure that at least one full period has passed since the last update
            ///@ dev require() was dropped in favor of if() to make this safe to call when unsure about elapsed time

            if(timeElapsed_1 >= PERIOD_1 || p1.price0Average.mul(PRECISION).decode144() == 0) {
                // overflow is desired, casting never truncates
                // cumulative price is in (uq112x112 price * seconds) units so we simply wrap it after division by time elapsed
                p1.price0Average = FixedPoint.uq112x112(uint224((price0Cumulative - p1.price0CumulativeLast) / timeElapsed_1));
                p1.price1Average = FixedPoint.uq112x112(uint224((price1Cumulative - p1.price1CumulativeLast) / timeElapsed_1));

                p1.price0CumulativeLast = price0Cumulative;
                p1.price1CumulativeLast = price1Cumulative;
                p1.blockTimestampLast = blockTimestamp;
            }
            if(timeElapsed_2 >= PERIOD_2 || p2.price0Average.mul(PRECISION).decode144() == 0) {
                // overflow is desired, casting never truncates
                // cumulative price is in (uq112x112 price * seconds) units so we simply wrap it after division by time elapsed
                p2.price0Average = FixedPoint.uq112x112(uint224((price0Cumulative - p2.price0CumulativeLast) / timeElapsed_2));
                p2.price1Average = FixedPoint.uq112x112(uint224((price1Cumulative - p2.price1CumulativeLast) / timeElapsed_2));

                p2.price0CumulativeLast = price0Cumulative;
                p2.price1CumulativeLast = price1Cumulative;
                p2.blockTimestampLast = blockTimestamp;
            }
            // No event emitter to save gas
        }
    }

    // note this will always return 0 before update has been called successfully for the first time.
    // this will return an average over a long period of time unless someone calls the update() function.
    
    /**
     @notice returns equivalent indexTokens for amountIn, token
     @dev always returns 0 before update(token) has been called successfully for the first time.
     @param token baseToken to update
     @param amountTokens amount in token native precision
     @param amountOut anount in tokens, reciprocal token
     */
    function consult(address token, uint256 amountTokens) public view returns (uint256 amountOut) {
        IUniswapV2Pair _pair = IUniswapV2Pair(UniswapV2Library.pairFor(uniswapFactory, token, indexToken));
        Pair storage p1 = period_1_pairs[address(_pair)];
        Pair storage p2 = period_2_pairs[address(_pair)];
        require(token == p1.token0 || token == p1.token1, 'UniswapOracleTWAPCompare: INVALID_TOKEN');
        require(p1.price0CumulativeLast > 0 && p2.price0CumulativeLast > 0, "UniswapOracleTWAPCompare: Gathering history. Try again later");
        uint256 p1Out = (token == p1.token0 ? p1.price0Average : p1.price1Average).mul(amountTokens).decode144();
        uint256 p2Out = (token == p2.token0 ? p2.price0Average : p2.price1Average).mul(amountTokens).decode144();
        if (p1Out > p2Out) {
            amountOut = p2Out;
        } else {
            amountOut = p1Out;
        }
    }

    /**
     @notice discoverable internal state. Returns pair info for period 1
     @param token baseToken to inspect
     */
    function pair1Info(address token) external view
        returns
    (
        address token0,
        address token1,
        uint256 price0CumulativeLast,
        uint256 price1CumulativeLast,
        uint256 price0Average,
        uint256 price1Average,
        uint32  blockTimestampLast,
        uint256 period
    )
    {
        IUniswapV2Pair _pair = IUniswapV2Pair(UniswapV2Library.pairFor(uniswapFactory, token, indexToken));
        Pair storage p = period_1_pairs[address(_pair)];
        return(
            p.token0,
            p.token1,
            p.price0CumulativeLast,
            p.price1CumulativeLast,
            p.price0Average.mul(PRECISION).decode144(),
            p.price1Average.mul(PRECISION).decode144(),
            p.blockTimestampLast,
            PERIOD_1
        );
    }

    /**
     @notice discoverable internal state. Returns pair info for period 2
     @param token baseToken to inspect
     */
    function pair2Info(address token) external view
        returns
    (
        address token0,
        address token1,
        uint256 price0CumulativeLast,
        uint256 price1CumulativeLast,
        uint256 price0Average,
        uint256 price1Average,
        uint32  blockTimestampLast,
        uint256 period
    )
    {
        IUniswapV2Pair _pair = IUniswapV2Pair(UniswapV2Library.pairFor(uniswapFactory, token, indexToken));
        Pair storage p = period_2_pairs[address(_pair)];
        return(
            p.token0,
            p.token1,
            p.price0CumulativeLast,
            p.price1CumulativeLast,
            p.price0Average.mul(PRECISION).decode144(),
            p.price1Average.mul(PRECISION).decode144(),
            p.blockTimestampLast,
            PERIOD_2
        );
    }

}
// File: contracts/oracle/OracleCommon.sol



// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;

import "../interface/IOracle.sol";
import "../common/ICHIModuleCommon.sol";

abstract contract OracleCommon is IOracle, ICHIModuleCommon {

    uint256 constant NORMAL = 18;
    bytes32 constant public override MODULE_TYPE = keccak256(abi.encodePacked("ICHI V1 Oracle Implementation"));
    address public override indexToken;

    event OracleDeployed(address sender, string description, address indexToken);
    event OracleInitialized(address sender, address baseToken, address indexToken);
    
    /**
     @notice records the oracle description and the index that will be used for all quotes
     @dev oneToken implementations can share oracles
     @param oneTokenFactory_ oneTokenFactory to bind to
     @param description_ all modules have a description. No processing or validation
     @param indexToken_ every oracle has an index token for reporting the value of a base token
     */
    constructor(address oneTokenFactory_, string memory description_, address indexToken_) 
        ICHIModuleCommon(oneTokenFactory_, ModuleType.Oracle, description_) 
    { 
        require(indexToken_ != NULL_ADDRESS, "OracleCommon: indexToken cannot be empty");
        indexToken = indexToken_;
        emit OracleDeployed(msg.sender, description_, indexToken_);
    }

    /**
     @notice oneTokens can share Oracles. Oracles must be re-initializable. They are initialized from the Factory.
     @param baseToken oracles _can be_ multi-tenant with separately initialized baseTokens
     */
    function init(address baseToken) external onlyModuleOrFactory virtual override {
        emit OracleInitialized(msg.sender, baseToken, indexToken);
    }

    /**
     @notice converts normalized precision 18 amounts to token native precision amounts, truncates low-order values
     @param token ERC20 token contract
     @param amountNormal quantity in precision-18
     @param amountTokens quantity scaled to token decimals()
     */    
    function normalizedToTokens(address token, uint256 amountNormal) public view override returns(uint256 amountTokens) {
        IERC20Extended t = IERC20Extended(token);
        uint256 nativeDecimals = t.decimals();
        require(nativeDecimals <= 18, "OracleCommon: unsupported token precision (greater than 18)");
        if(nativeDecimals == NORMAL) return amountNormal;
        return amountNormal / ( 10 ** (NORMAL - nativeDecimals));
    }

    /**
     @notice converts token native precision amounts to normalized precision 18 amounts
     @param token ERC20 token contract
     @param amountTokens quantity scaled to token decimals
     @param amountNormal quantity in precision-18
     */  
    function tokensToNormalized(address token, uint256 amountTokens) public view override returns(uint256 amountNormal) {
        IERC20Extended t = IERC20Extended(token);
        uint256 nativeDecimals = t.decimals();
        require(nativeDecimals <= 18, "OracleCommon: unsupported token precision (greater than 18)");
        if(nativeDecimals == NORMAL) return amountTokens;
        return amountTokens * ( 10 ** (NORMAL - nativeDecimals));
    }

}

// File: contracts/_openzeppelin/math/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, 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 (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

// File: contracts/_uniswap/v2-core/contracts/interfaces/IUniswapV2Factory.sol



// SPDX-License-Identifier: GNU

pragma solidity >=0.5.0;

interface IUniswapV2Factory {
//    event PairCreated(address indexed token0, address indexed token1, address pair, uint256);

//    function feeTo() external view returns (address);
//    function feeToSetter() external view returns (address);
//
//    function allPairs(uint256) external view returns (address pair);
    function allPairsLength() external view returns (uint256);

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

    function setFeeTo(address) external;
    function setFeeToSetter(address) external;
}

// File: contracts/_uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol



// SPDX-License-Identifier: GNU

pragma solidity =0.7.6;

interface IUniswapV2Pair {
//    event Approval(address indexed owner, address indexed spender, uint256 value);
//    event Transfer(address indexed from, address indexed to, uint256 value);

//    function name() external pure returns (string memory);
//    function symbol() external pure returns (string memory);
//    function decimals() external pure returns (uint8);
//    function totalSupply() external view returns (uint256);
//    function balanceOf(address owner) external view returns (uint256);
//    function allowance(address owner, address spender) external view returns (uint256);
//
//    function approve(address spender, uint256 value) external returns (bool);
//    function transfer(address to, uint256 value) external returns (bool);
//    function transferFrom(address from, address to, uint256 value) external returns (bool);

//    function DOMAIN_SEPARATOR() external view returns (bytes32);
//    function PERMIT_TYPEHASH() external pure returns (bytes32);
//    function nonces(address owner) external view returns (uint256);
//
//    function permit(address owner, address spender, uint256 value, uint256 deadline, uint8 v, bytes32 r, bytes32 s) external;
//
//    event Mint(address indexed sender, uint256 amount0, uint256 amount1);
//    event Burn(address indexed sender, uint256 amount0, uint256 amount1, address indexed to);
//    event Swap(
//        address indexed sender,
//        uint256 amount0In,
//        uint256 amount1In,
//        uint256 amount0Out,
//        uint256 amount1Out,
//        address indexed to
//    );
    event Sync(uint112 reserve0, uint112 reserve1);

//    function MINIMUM_LIQUIDITY() external pure returns (uint256);
//    function factory() external view returns (address);
    function token0() external view returns (address);
    function token1() external view returns (address);
    function getReserves() external view returns (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast);
    function price0CumulativeLast() external view returns (uint256);
    function price1CumulativeLast() external view returns (uint256);
//    function kLast() external view returns (uint256);
//
//    function mint(address to) external returns (uint256 liquidity);
//    function burn(address to) external returns (uint256 amount0, uint256 amount1);
//    function swap(uint256 amount0Out, uint256 amount1Out, address to, bytes calldata data) external;
//    function skim(address to) external;
    function sync() external;

    function initialize(address, address) external;
}

// File: contracts/_uniswap/lib/contracts/libraries/FixedPoint.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity >=0.4.0;

import './FullMath.sol';
import './Babylonian.sol';
import './BitMath.sol';

// a library for handling binary fixed point numbers (https://en.wikipedia.org/wiki/Q_(number_format))
library FixedPoint {
    // range: [0, 2**112 - 1]
    // resolution: 1 / 2**112
    struct uq112x112 {
        uint224 _x;
    }

    // range: [0, 2**144 - 1]
    // resolution: 1 / 2**112
    struct uq144x112 {
        uint256 _x;
    }

    uint8 public constant RESOLUTION = 112;
    uint256 public constant Q112 = 0x10000000000000000000000000000; // 2**112
    uint256 private constant Q224 = 0x100000000000000000000000000000000000000000000000000000000; // 2**224
    uint256 private constant LOWER_MASK = 0xffffffffffffffffffffffffffff; // decimal of UQ*x112 (lower 112 bits)

    // encode a uint112 as a UQ112x112
    function encode(uint112 x) internal pure returns (uq112x112 memory) {
        return uq112x112(uint224(x) << RESOLUTION);
    }

    // encodes a uint144 as a UQ144x112
    function encode144(uint144 x) internal pure returns (uq144x112 memory) {
        return uq144x112(uint256(x) << RESOLUTION);
    }

    // decode a UQ112x112 into a uint112 by truncating after the radix point
    function decode(uq112x112 memory self) internal pure returns (uint112) {
        return uint112(self._x >> RESOLUTION);
    }

    // decode a UQ144x112 into a uint144 by truncating after the radix point
    function decode144(uq144x112 memory self) internal pure returns (uint144) {
        return uint144(self._x >> RESOLUTION);
    }

    // multiply a UQ112x112 by a uint256, returning a UQ144x112
    // reverts on overflow
    function mul(uq112x112 memory self, uint256 y) internal pure returns (uq144x112 memory) {
        uint256 z = 0;
        require(y == 0 || (z = self._x * y) / y == self._x, 'FixedPoint::mul: overflow');
        return uq144x112(z);
    }

    // multiply a UQ112x112 by an int and decode, returning an int
    // reverts on overflow
    function muli(uq112x112 memory self, int256 y) internal pure returns (int256) {
        uint256 z = FullMath.mulDiv(self._x, uint256(y < 0 ? -y : y), Q112);
        require(z < 2**255, 'FixedPoint::muli: overflow');
        return y < 0 ? -int256(z) : int256(z);
    }

    // multiply a UQ112x112 by a UQ112x112, returning a UQ112x112
    // lossy
    function muluq(uq112x112 memory self, uq112x112 memory other) internal pure returns (uq112x112 memory) {
        if (self._x == 0 || other._x == 0) {
            return uq112x112(0);
        }
        uint112 upper_self = uint112(self._x >> RESOLUTION); // * 2^0
        uint112 lower_self = uint112(self._x & LOWER_MASK); // * 2^-112
        uint112 upper_other = uint112(other._x >> RESOLUTION); // * 2^0
        uint112 lower_other = uint112(other._x & LOWER_MASK); // * 2^-112

        // partial products
        uint224 upper = uint224(upper_self) * upper_other; // * 2^0
        uint224 lower = uint224(lower_self) * lower_other; // * 2^-224
        uint224 uppers_lowero = uint224(upper_self) * lower_other; // * 2^-112
        uint224 uppero_lowers = uint224(upper_other) * lower_self; // * 2^-112

        // so the bit shift does not overflow
        require(upper <= uint112(-1), 'FixedPoint::muluq: upper overflow');

        // this cannot exceed 256 bits, all values are 224 bits
        uint256 sum = uint256(upper << RESOLUTION) + uppers_lowero + uppero_lowers + (lower >> RESOLUTION);

        // so the cast does not overflow
        require(sum <= uint224(-1), 'FixedPoint::muluq: sum overflow');

        return uq112x112(uint224(sum));
    }

    // divide a UQ112x112 by a UQ112x112, returning a UQ112x112
    function divuq(uq112x112 memory self, uq112x112 memory other) internal pure returns (uq112x112 memory) {
        require(other._x > 0, 'FixedPoint::divuq: division by zero');
        if (self._x == other._x) {
            return uq112x112(uint224(Q112));
        }
        if (self._x <= uint144(-1)) {
            uint256 value = (uint256(self._x) << RESOLUTION) / other._x;
            require(value <= uint224(-1), 'FixedPoint::divuq: overflow');
            return uq112x112(uint224(value));
        }

        uint256 result = FullMath.mulDiv(Q112, self._x, other._x);
        require(result <= uint224(-1), 'FixedPoint::divuq: overflow');
        return uq112x112(uint224(result));
    }

    // returns a UQ112x112 which represents the ratio of the numerator to the denominator
    // can be lossy
    function fraction(uint256 numerator, uint256 denominator) internal pure returns (uq112x112 memory) {
        require(denominator > 0, 'FixedPoint::fraction: division by zero');
        if (numerator == 0) return FixedPoint.uq112x112(0);

        if (numerator <= uint144(-1)) {
            uint256 result = (numerator << RESOLUTION) / denominator;
            require(result <= uint224(-1), 'FixedPoint::fraction: overflow');
            return uq112x112(uint224(result));
        } else {
            uint256 result = FullMath.mulDiv(numerator, Q112, denominator);
            require(result <= uint224(-1), 'FixedPoint::fraction: overflow');
            return uq112x112(uint224(result));
        }
    }

    // take the reciprocal of a UQ112x112
    // reverts on overflow
    // lossy
    function reciprocal(uq112x112 memory self) internal pure returns (uq112x112 memory) {
        require(self._x != 0, 'FixedPoint::reciprocal: reciprocal of zero');
        require(self._x != 1, 'FixedPoint::reciprocal: overflow');
        return uq112x112(uint224(Q224 / self._x));
    }

    // square root of a UQ112x112
    // lossy between 0/1 and 40 bits
    function sqrt(uq112x112 memory self) internal pure returns (uq112x112 memory) {
        if (self._x <= uint144(-1)) {
            return uq112x112(uint224(Babylonian.sqrt(uint256(self._x) << 112)));
        }

        uint8 safeShiftBits = 255 - BitMath.mostSignificantBit(self._x);
        safeShiftBits -= safeShiftBits % 2;
        return uq112x112(uint224(Babylonian.sqrt(uint256(self._x) << safeShiftBits) << ((112 - safeShiftBits) / 2)));
    }
}

// File: contracts/_uniswap/v2-periphery/contracts/libraries/UniswapV2OracleLibrary.sol



// SPDX-License-Identifier: GNU

pragma solidity 0.7.6;

import "./UniswapV2Library.sol";
import '../../../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 (uint256 price0Cumulative, uint256 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 += uint256(FixedPoint.fraction(reserve1, reserve0)._x) * timeElapsed;
            // counterfactual
            price1Cumulative += uint256(FixedPoint.fraction(reserve0, reserve1)._x) * timeElapsed;
        }
    }
}

// File: contracts/_uniswap/v2-periphery/contracts/libraries/UniswapV2Library.sol



// SPDX-License-Identifier: GNU

pragma solidity 0.7.6;

import '../../../v2-core/contracts/interfaces/IUniswapV2Pair.sol';
import '../../../v2-core/contracts/UniswapV2Pair.sol';

import "./UniswapSafeMath.sol";

library UniswapV2Library {
    using UniswapSafeMath for uint256;

    // 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');
    }

    function getInitHash() public pure returns (bytes32){
        bytes memory bytecode = type(UniswapV2Pair).creationCode;
        return keccak256(abi.encodePacked(bytecode));
    }

    // 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);
        uint chainId;
        assembly {
            chainId := chainid()
        }
        if (chainId == 1) {
            pair = address(uint256(keccak256(abi.encodePacked(
                hex'ff',
                factory,
                keccak256(abi.encodePacked(token0, token1)),
                hex'96e8ac4277198ff8b6f785478aa9a39f403cb768dd02cbee326c3e7da348845f' // init code hash
            ))));
        } else {
            pair = address(uint256(keccak256(abi.encodePacked(
                hex'ff',
                factory,
                keccak256(abi.encodePacked(token0, token1)),
                getInitHash()
            ))));
        }
        
    }

    // fetches and sorts the reserves for a pair
    function getReserves(address factory, address tokenA, address tokenB) internal view returns (uint256 reserveA, uint256 reserveB) {
        (address token0,) = sortTokens(tokenA, tokenB);
        (uint256 reserve0, uint256 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(uint256 amountA, uint256 reserveA, uint256 reserveB) internal pure returns (uint256 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(uint256 amountIn, uint256 reserveIn, uint256 reserveOut) internal pure returns (uint256 amountOut) {
        require(amountIn > 0, 'UniswapV2Library: INSUFFICIENT_INPUT_AMOUNT');
        require(reserveIn > 0 && reserveOut > 0, 'UniswapV2Library: INSUFFICIENT_LIQUIDITY');
        uint256 amountInWithFee = amountIn.mul(997);
        uint256 numerator = amountInWithFee.mul(reserveOut);
        uint256 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(uint256 amountOut, uint256 reserveIn, uint256 reserveOut) internal pure returns (uint256 amountIn) {
        require(amountOut > 0, 'UniswapV2Library: INSUFFICIENT_OUTPUT_AMOUNT');
        require(reserveIn > 0 && reserveOut > 0, 'UniswapV2Library: INSUFFICIENT_LIQUIDITY');
        uint256 numerator = reserveIn.mul(amountOut).mul(1000);
        uint256 denominator = reserveOut.sub(amountOut).mul(997);
        amountIn = (numerator / denominator).add(1);
    }

    // performs chained getAmountOut calculations on any number of pairs
    function getAmountsOut(address factory, uint256 amountIn, address[] memory path) internal view returns (uint256[] memory amounts) {
        require(path.length >= 2, 'UniswapV2Library: INVALID_PATH');
        amounts = new uint256[](path.length);
        amounts[0] = amountIn;
        for (uint256 i; i < path.length - 1; i++) {
            (uint256 reserveIn, uint256 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, uint256 amountOut, address[] memory path) internal view returns (uint256[] memory amounts) {
        require(path.length >= 2, 'UniswapV2Library: INVALID_PATH');
        amounts = new uint256[](path.length);
        amounts[amounts.length - 1] = amountOut;
        for (uint256 i = path.length - 1; i > 0; i--) {
            (uint256 reserveIn, uint256 reserveOut) = getReserves(factory, path[i - 1], path[i]);
            amounts[i - 1] = getAmountIn(amounts[i], reserveIn, reserveOut);
        }
    }
}

// File: contracts/interface/IOracle.sol



// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;

import "./IModule.sol";

interface IOracle is IModule {

    function init(address baseToken) external;
    function update(address token) external;
    function indexToken() external view returns(address);

    /**
     @param token ERC20 token
     @param amountTokens quantity, token native precision
     @param amountUsd US dollar equivalent, precision 18
     @param volatility metric for future use-cases
     */
    function read(address token, uint amountTokens) external view returns(uint amountUsd, uint volatility);

    /**
     @param token ERC20 token
     @param amountTokens token quantity, token native precision
     @param amountUsd US dollar equivalent, precision 18
     @param volatility metric for future use-cases
     */    
    function amountRequired(address token, uint amountUsd) external view returns(uint amountTokens, uint volatility);

    /**
     @notice converts normalized precision-18 amounts to token native precision amounts, truncates low-order values
     @param token ERC20 token contract
     @param amountNormal quantity, precision 18
     @param amountTokens quantity scaled to token precision
     */    
    function normalizedToTokens(address token, uint amountNormal) external view returns(uint amountTokens);

    /**
     @notice converts token native precision amounts to normalized precision-18 amounts
     @param token ERC20 token contract
     @param amountNormal quantity, precision 18
     @param amountTokens quantity scaled to token precision
     */  
    function tokensToNormalized(address token, uint amountTokens) external view returns(uint amountNormal);
}

// File: contracts/common/ICHIModuleCommon.sol



// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;

import "../interface/IModule.sol";
import "../interface/IOneTokenFactory.sol";
import "../interface/IOneTokenV1Base.sol";
import "./ICHICommon.sol";

abstract contract ICHIModuleCommon is IModule, ICHICommon {
    
    ModuleType public immutable override moduleType;
    string public override moduleDescription;
    address public immutable override oneTokenFactory;

    event ModuleDeployed(address sender, ModuleType moduleType, string description);
    event DescriptionUpdated(address sender, string description);
   
    modifier onlyKnownToken {
        require(IOneTokenFactory(oneTokenFactory).isOneToken(msg.sender), "ICHIModuleCommon: msg.sender is not a known oneToken");
        _;
    }
    
    modifier onlyTokenOwner (address oneToken) {
        require(msg.sender == IOneTokenV1Base(oneToken).owner(), "ICHIModuleCommon: msg.sender is not oneToken owner");
        _;
    }

    modifier onlyModuleOrFactory {
        if(!IOneTokenFactory(oneTokenFactory).isModule(msg.sender)) {
            require(msg.sender == oneTokenFactory, "ICHIModuleCommon: msg.sender is not module owner, token factory or registed module");
        }
        _;
    }
    
    /**
     @notice modules are bound to the factory at deployment time
     @param oneTokenFactory_ factory to bind to
     @param moduleType_ type number helps prevent governance errors
     @param description_ human-readable, descriptive only
     */    
    constructor (address oneTokenFactory_, ModuleType moduleType_, string memory description_) {
        require(oneTokenFactory_ != NULL_ADDRESS, "ICHIModuleCommon: oneTokenFactory cannot be empty");
        require(bytes(description_).length > 0, "ICHIModuleCommon: description cannot be empty");
        oneTokenFactory = oneTokenFactory_;
        moduleType = moduleType_;
        moduleDescription = description_;
        emit ModuleDeployed(msg.sender, moduleType_, description_);
    }

    /**
     @notice set a module description
     @param description new module desciption
     */
    function updateDescription(string memory description) external onlyOwner override {
        require(bytes(description).length > 0, "ICHIModuleCommon: description cannot be empty");
        moduleDescription = description;
        emit DescriptionUpdated(msg.sender, description);
    }  
}

// File: contracts/interface/IModule.sol



// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;

import "./IICHICommon.sol";
import "./InterfaceCommon.sol";

interface IModule is IICHICommon { 
       
    function oneTokenFactory() external view returns(address);
    function updateDescription(string memory description) external;
    function moduleDescription() external view returns(string memory);
    function MODULE_TYPE() external view returns(bytes32);
    function moduleType() external view returns(ModuleType);
}

// File: contracts/interface/IICHICommon.sol



// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;

import "./IICHIOwnable.sol";
import "./InterfaceCommon.sol";

interface IICHICommon is IICHIOwnable, InterfaceCommon {}

// File: contracts/interface/InterfaceCommon.sol



// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;
pragma abicoder v2;

interface InterfaceCommon {

    enum ModuleType { Version, Controller, Strategy, MintMaster, Oracle }

}

// File: contracts/interface/IICHIOwnable.sol



// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;

interface IICHIOwnable {
    
    function renounceOwnership() external;
    function transferOwnership(address newOwner) external;
    function owner() external view returns (address);
}

// File: contracts/interface/IOneTokenFactory.sol



// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;
pragma abicoder v2;

import "./InterfaceCommon.sol";

interface IOneTokenFactory is InterfaceCommon {

    function oneTokenProxyAdmins(address) external returns(address);
    function deployOneTokenProxy(
        string memory name,
        string memory symbol,
        address governance, 
        address version,
        address controller,
        address mintMaster,              
        address memberToken, 
        address collateral,
        address oneTokenOracle
    ) 
        external 
        returns(address newOneTokenProxy, address proxyAdmin);

    function admitModule(address module, ModuleType moduleType, string memory name, string memory url) external;
    function updateModule(address module, string memory name, string memory url) external;
    function removeModule(address module) external;

    function admitForeignToken(address foreignToken, bool collateral, address oracle) external;
    function updateForeignToken(address foreignToken, bool collateral) external;
    function removeForeignToken(address foreignToken) external;

    function assignOracle(address foreignToken, address oracle) external;
    function removeOracle(address foreignToken, address oracle) external; 

    /**
     * View functions
     */
    
    function MODULE_TYPE() external view returns(bytes32);

    function oneTokenCount() external view returns(uint256);
    function oneTokenAtIndex(uint256 index) external view returns(address);
    function isOneToken(address oneToken) external view returns(bool);
 
    // modules

    function moduleCount() external view returns(uint256);
    function moduleAtIndex(uint256 index) external view returns(address module);
    function isModule(address module) external view returns(bool);
    function isValidModuleType(address module, ModuleType moduleType) external view returns(bool);

    // foreign tokens

    function foreignTokenCount() external view returns(uint256);
    function foreignTokenAtIndex(uint256 index) external view returns(address);
    function foreignTokenInfo(address foreignToken) external view returns(bool collateral, uint256 oracleCount);
    function foreignTokenOracleCount(address foreignToken) external view returns(uint256);
    function foreignTokenOracleAtIndex(address foreignToken, uint256 index) external view returns(address);
    function isOracle(address foreignToken, address oracle) external view returns(bool);
    function isForeignToken(address foreignToken) external view returns(bool);
    function isCollateral(address foreignToken) external view returns(bool);
}
// File: contracts/interface/IOneTokenV1Base.sol



// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;

import "./IICHICommon.sol";
import "./IERC20Extended.sol";

interface IOneTokenV1Base is IICHICommon, IERC20 {
    
    function init(string memory name_, string memory symbol_, address oneTokenOracle_, address controller_,  address mintMaster_, address memberToken_, address collateral_) external;
    function changeController(address controller_) external;
    function changeMintMaster(address mintMaster_, address oneTokenOracle) external;
    function addAsset(address token, address oracle) external;
    function removeAsset(address token) external;
    function setStrategy(address token, address strategy, uint256 allowance) external;
    function executeStrategy(address token) external;
    function removeStrategy(address token) external;
    function closeStrategy(address token) external;
    function increaseStrategyAllowance(address token, uint256 amount) external;
    function decreaseStrategyAllowance(address token, uint256 amount) external;
    function setFactory(address newFactory) external;

    function MODULE_TYPE() external view returns(bytes32);
    function oneTokenFactory() external view returns(address);
    function controller() external view returns(address);
    function mintMaster() external view returns(address);
    function memberToken() external view returns(address);
    function assets(address) external view returns(address, address);
    function balances(address token) external view returns(uint256 inVault, uint256 inStrategy);
    function collateralTokenCount() external view returns(uint256);
    function collateralTokenAtIndex(uint256 index) external view returns(address);
    function isCollateral(address token) external view returns(bool);
    function otherTokenCount() external view  returns(uint256);
    function otherTokenAtIndex(uint256 index) external view returns(address); 
    function isOtherToken(address token) external view returns(bool);
    function assetCount() external view returns(uint256);
    function assetAtIndex(uint256 index) external view returns(address); 
    function isAsset(address token) external view returns(bool);
}

// File: contracts/common/ICHICommon.sol



// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;

import "../oz_modified/ICHIOwnable.sol";
import "../oz_modified/ICHIInitializable.sol";
import "../interface/IERC20Extended.sol";
import "../interface/IICHICommon.sol";

contract ICHICommon is IICHICommon, ICHIOwnable, ICHIInitializable {

    uint256 constant PRECISION = 10 ** 18;
    uint256 constant INFINITE = uint256(0-1);
    address constant NULL_ADDRESS = address(0);
    
    // @dev internal fingerprints help prevent deployment-time governance errors

    bytes32 constant COMPONENT_CONTROLLER = keccak256(abi.encodePacked("ICHI V1 Controller"));
    bytes32 constant COMPONENT_VERSION = keccak256(abi.encodePacked("ICHI V1 OneToken Implementation"));
    bytes32 constant COMPONENT_STRATEGY = keccak256(abi.encodePacked("ICHI V1 Strategy Implementation"));
    bytes32 constant COMPONENT_MINTMASTER = keccak256(abi.encodePacked("ICHI V1 MintMaster Implementation"));
    bytes32 constant COMPONENT_ORACLE = keccak256(abi.encodePacked("ICHI V1 Oracle Implementation"));
    bytes32 constant COMPONENT_VOTERROLL = keccak256(abi.encodePacked("ICHI V1 VoterRoll Implementation"));
    bytes32 constant COMPONENT_FACTORY = keccak256(abi.encodePacked("ICHI OneToken Factory"));
}

// File: contracts/interface/IERC20Extended.sol



// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;

import "../_openzeppelin/token/ERC20/IERC20.sol";

interface IERC20Extended is IERC20 {
    
    function decimals() external view returns(uint8);
    function symbol() external view returns(string memory);
    function name() external view returns(string memory);
}

// File: contracts/_openzeppelin/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: contracts/oz_modified/ICHIOwnable.sol



// SPDX-License-Identifier: MIT

/**
 * @dev Constructor visibility has been removed from the original.
 * _transferOwnership() has been added to support proxied deployments.
 * Abstract tag removed from contract block.
 * Added interface inheritance and override modifiers.
 * Changed contract identifier in require error messages.
 */

pragma solidity >=0.6.0 <0.8.0;

import "../_openzeppelin/utils/Context.sol";
import "../interface/IICHIOwnable.sol";
/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
contract ICHIOwnable is IICHIOwnable, Context {
    
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Throws if called by any account other than the owner.
     */
     
    modifier onlyOwner() {
        require(owner() == _msgSender(), "ICHIOwnable: caller is not the owner");
        _;
    }    

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     * Ineffective for proxied deployed. Use initOwnable.
     */
    constructor() {
        _transferOwnership(msg.sender);
    }

    /**
     @dev initialize proxied deployment
     */
    function initOwnable() internal {
        require(owner() == address(0), "ICHIOwnable: already initialized");
        _transferOwnership(msg.sender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual override returns (address) {
        return _owner;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual override onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */

    function transferOwnership(address newOwner) public virtual override onlyOwner {
        _transferOwnership(newOwner);
    }

    /**
     * @dev be sure to call this in the initialization stage of proxied deployment or owner will not be set
     */

    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0), "ICHIOwnable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// File: contracts/oz_modified/ICHIInitializable.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.7.6;

import "../_openzeppelin/utils/Address.sol";

contract ICHIInitializable {

    bool private _initialized;
    bool private _initializing;

    modifier initializer() {
        require(_initializing || _isConstructor() || !_initialized, "ICHIInitializable: contract is already initialized");

        bool isTopLevelCall = !_initializing;
        if (isTopLevelCall) {
            _initializing = true;
            _initialized = true;
        }

        _;

        if (isTopLevelCall) {
            _initializing = false;
        }
    }

    modifier initialized {
        require(_initialized, "ICHIInitializable: contract is not initialized");
        _;
    }

    function _isConstructor() private view returns (bool) {
        return !Address.isContract(address(this));
    }
}



// File: contracts/_openzeppelin/utils/Context.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: contracts/_openzeppelin/utils/Address.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: contracts/_uniswap/lib/contracts/libraries/FullMath.sol



// SPDX-License-Identifier: CC-BY-4.0
pragma solidity >=0.4.0;

// taken from https://medium.com/coinmonks/math-in-solidity-part-3-percents-and-proportions-4db014e080b1
// license is CC-BY-4.0
library FullMath {
    function fullMul(uint256 x, uint256 y) internal pure returns (uint256 l, uint256 h) {
        uint256 mm = mulmod(x, y, uint256(-1));
        l = x * y;
        h = mm - l;
        if (mm < l) h -= 1;
    }

    function fullDiv(
        uint256 l,
        uint256 h,
        uint256 d
    ) private pure returns (uint256) {
        uint256 pow2 = d & -d;
        d /= pow2;
        l /= pow2;
        l += h * ((-pow2) / pow2 + 1);
        uint256 r = 1;
        r *= 2 - d * r;
        r *= 2 - d * r;
        r *= 2 - d * r;
        r *= 2 - d * r;
        r *= 2 - d * r;
        r *= 2 - d * r;
        r *= 2 - d * r;
        r *= 2 - d * r;
        return l * r;
    }

    function mulDiv(
        uint256 x,
        uint256 y,
        uint256 d
    ) internal pure returns (uint256) {
        (uint256 l, uint256 h) = fullMul(x, y);

        uint256 mm = mulmod(x, y, d);
        if (mm > l) h -= 1;
        l -= mm;

        if (h == 0) return l / d;

        require(h < d, 'FullMath: FULLDIV_OVERFLOW');
        return fullDiv(l, h, d);
    }
}

// File: contracts/_uniswap/lib/contracts/libraries/Babylonian.sol



// SPDX-License-Identifier: GPL-3.0-or-later

pragma solidity >=0.4.0;

// computes square roots using the babylonian method
// https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Babylonian_method
library Babylonian {
    // credit for this implementation goes to
    // https://github.com/abdk-consulting/abdk-libraries-solidity/blob/master/ABDKMath64x64.sol#L687
    function sqrt(uint256 x) internal pure returns (uint256) {
        if (x == 0) return 0;
        // this block is equivalent to r = uint256(1) << (BitMath.mostSignificantBit(x) / 2);
        // however that code costs significantly more gas
        uint256 xx = x;
        uint256 r = 1;
        if (xx >= 0x100000000000000000000000000000000) {
            xx >>= 128;
            r <<= 64;
        }
        if (xx >= 0x10000000000000000) {
            xx >>= 64;
            r <<= 32;
        }
        if (xx >= 0x100000000) {
            xx >>= 32;
            r <<= 16;
        }
        if (xx >= 0x10000) {
            xx >>= 16;
            r <<= 8;
        }
        if (xx >= 0x100) {
            xx >>= 8;
            r <<= 4;
        }
        if (xx >= 0x10) {
            xx >>= 4;
            r <<= 2;
        }
        if (xx >= 0x8) {
            r <<= 1;
        }
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1; // Seven iterations should be enough
        uint256 r1 = x / r;
        return (r < r1 ? r : r1);
    }
}

// File: contracts/_uniswap/lib/contracts/libraries/BitMath.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity >=0.5.0;

library BitMath {
    // returns the 0 indexed position of the most significant bit of the input x
    // s.t. x >= 2**msb and x < 2**(msb+1)
    function mostSignificantBit(uint256 x) internal pure returns (uint8 r) {
        require(x > 0, 'BitMath::mostSignificantBit: zero');

        if (x >= 0x100000000000000000000000000000000) {
            x >>= 128;
            r += 128;
        }
        if (x >= 0x10000000000000000) {
            x >>= 64;
            r += 64;
        }
        if (x >= 0x100000000) {
            x >>= 32;
            r += 32;
        }
        if (x >= 0x10000) {
            x >>= 16;
            r += 16;
        }
        if (x >= 0x100) {
            x >>= 8;
            r += 8;
        }
        if (x >= 0x10) {
            x >>= 4;
            r += 4;
        }
        if (x >= 0x4) {
            x >>= 2;
            r += 2;
        }
        if (x >= 0x2) r += 1;
    }

    // returns the 0 indexed position of the least significant bit of the input x
    // s.t. (x & 2**lsb) != 0 and (x & (2**(lsb) - 1)) == 0)
    // i.e. the bit at the index is set and the mask of all lower bits is 0
    function leastSignificantBit(uint256 x) internal pure returns (uint8 r) {
        require(x > 0, 'BitMath::leastSignificantBit: zero');

        r = 255;
        if (x & uint128(-1) > 0) {
            r -= 128;
        } else {
            x >>= 128;
        }
        if (x & uint64(-1) > 0) {
            r -= 64;
        } else {
            x >>= 64;
        }
        if (x & uint32(-1) > 0) {
            r -= 32;
        } else {
            x >>= 32;
        }
        if (x & uint16(-1) > 0) {
            r -= 16;
        } else {
            x >>= 16;
        }
        if (x & uint8(-1) > 0) {
            r -= 8;
        } else {
            x >>= 8;
        }
        if (x & 0xf > 0) {
            r -= 4;
        } else {
            x >>= 4;
        }
        if (x & 0x3 > 0) {
            r -= 2;
        } else {
            x >>= 2;
        }
        if (x & 0x1 > 0) r -= 1;
    }
}

// File: contracts/_uniswap/v2-core/contracts/UniswapV2Pair.sol



// SPDX-License-Identifier: ISC

pragma solidity =0.7.6;

import './libraries/UQ112x112.sol';
import './interfaces/IUniswapV2Pair.sol';
import './interfaces/IUniswapV2Factory.sol';
import "./libraries/UniSafeMath.sol";
import "../../../_openzeppelin/token/ERC20/IERC20.sol";

contract UniswapV2Pair is IUniswapV2Pair {
    using UniSafeMath  for uint256;
    using UQ112x112 for uint224;

    uint256 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

    uint256 public _price0CumulativeLast;
    uint256 public _price1CumulativeLast;
    uint256 public kLast; // reserve0 * reserve1, as of immediately after the most recent liquidity event

    constructor() {
        factory = msg.sender;
    }

    // called once by the factory at time of deployment
    function initialize(address __token0, address __token1) override external {
        require(msg.sender == factory, 'UniswapV2: FORBIDDEN');
        // sufficient check
        _token0 = __token0;
        _token1 = __token1;
    }

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

    function token0() override external view returns (address){
        return _token0;
    }
    function token1() override external view returns (address){
        return _token1;
    }

    function price0CumulativeLast() override external view returns (uint256){
        return _price0CumulativeLast;
    }
    function price1CumulativeLast() override external view returns (uint256){
        return _price1CumulativeLast;
    }

    // update reserves and, on the first call per block, price accumulators
    function _update(uint256 balance0, uint256 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 += uint256(UQ112x112.encode(_reserve1).uqdiv(_reserve0)) * timeElapsed;
            _price1CumulativeLast += uint256(UQ112x112.encode(_reserve0).uqdiv(_reserve1)) * timeElapsed;
        }
        reserve0 = uint112(balance0);
        reserve1 = uint112(balance1);
        blockTimestampLast = blockTimestamp;
        emit Sync(reserve0, reserve1);
    }

    // force reserves to match balances
    function sync() override external {
        _update(IERC20(_token0).balanceOf(address(this)), IERC20(_token1).balanceOf(address(this)), reserve0, reserve1);
    }
}

// File: contracts/_uniswap/v2-periphery/contracts/libraries/UniswapSafeMath.sol



// SPDX-License-Identifier: GNU

/**
 * @dev this contract is renamed to prevent conflict with oz while avoiding significant changes 
 */

pragma solidity 0.7.6;

// a library for performing overflow-safe math, courtesy of DappHub (https://github.com/dapphub/ds-math)

library UniswapSafeMath {
    function add(uint256 x, uint256 y) internal pure returns (uint256 z) {
        require((z = x + y) >= x, 'ds-math-add-overflow');
    }

    function sub(uint256 x, uint256 y) internal pure returns (uint256 z) {
        require((z = x - y) <= x, 'ds-math-sub-underflow');
    }

    function mul(uint256 x, uint256 y) internal pure returns (uint256 z) {
        require(y == 0 || (z = x * y) / y == x, 'ds-math-mul-overflow');
    }
}

// File: contracts/_uniswap/v2-core/contracts/libraries/UQ112x112.sol



// SPDX-License-Identifier: ISC

pragma solidity =0.7.6;

// 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);
    }
}

// File: contracts/_uniswap/v2-core/contracts/libraries/UniSafeMath.sol



// SPDX-License-Identifier: ISC

pragma solidity =0.7.6;

// a library for performing overflow-safe math, courtesy of DappHub (https://github.com/dapphub/ds-math)

library UniSafeMath {
    function add(uint256 x, uint256 y) internal pure returns (uint256 z) {
        require((z = x + y) >= x, 'ds-math-add-overflow');
    }

    function sub(uint256 x, uint256 y) internal pure returns (uint256 z) {
        require((z = x - y) <= x, 'ds-math-sub-underflow');
    }

    function mul(uint256 x, uint256 y) internal pure returns (uint256 z) {
        require(y == 0 || (z = x * y) / y == x, 'ds-math-mul-overflow');
    }
}