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pragma solidity 0.4.26;

// File: contracts/token/interfaces/IERC20Token.sol

/*
    ERC20 Standard Token interface
*/
contract IERC20Token {
    // these functions aren't abstract since the compiler emits automatically generated getter functions as external
    function name() public view returns (string) {this;}
    function symbol() public view returns (string) {this;}
    function decimals() public view returns (uint8) {this;}
    function totalSupply() public view returns (uint256) {this;}
    function balanceOf(address _owner) public view returns (uint256) {_owner; this;}
    function allowance(address _owner, address _spender) public view returns (uint256) {_owner; _spender; this;}

    function transfer(address _to, uint256 _value) public returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);
    function approve(address _spender, uint256 _value) public returns (bool success);
}

// File: contracts/utility/interfaces/IWhitelist.sol

/*
    Whitelist interface
*/
contract IWhitelist {
    function isWhitelisted(address _address) public view returns (bool);
}

// File: contracts/converter/interfaces/IBancorConverter.sol

/*
    Bancor Converter interface
*/
contract IBancorConverter {
    function getReturn(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount) public view returns (uint256, uint256);
    function convert2(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn, address _affiliateAccount, uint256 _affiliateFee) public returns (uint256);
    function quickConvert2(IERC20Token[] _path, uint256 _amount, uint256 _minReturn, address _affiliateAccount, uint256 _affiliateFee) public payable returns (uint256);
    function conversionWhitelist() public view returns (IWhitelist) {this;}
    function conversionFee() public view returns (uint32) {this;}
    function reserves(address _address) public view returns (uint256, uint32, bool, bool, bool) {_address; this;}
    function getReserveBalance(IERC20Token _reserveToken) public view returns (uint256);
    function reserveTokens(uint256 _index) public view returns (IERC20Token) {_index; this;}
    // deprecated, backward compatibility
    function change(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn) public returns (uint256);
    function convert(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn) public returns (uint256);
    function quickConvert(IERC20Token[] _path, uint256 _amount, uint256 _minReturn) public payable returns (uint256);
    function connectors(address _address) public view returns (uint256, uint32, bool, bool, bool);
    function getConnectorBalance(IERC20Token _connectorToken) public view returns (uint256);
    function connectorTokens(uint256 _index) public view returns (IERC20Token);
}

// File: contracts/converter/interfaces/IBancorConverterUpgrader.sol

/*
    Bancor Converter Upgrader interface
*/
contract IBancorConverterUpgrader {
    function upgrade(bytes32 _version) public;
    function upgrade(uint16 _version) public;
}

// File: contracts/converter/interfaces/IBancorFormula.sol

/*
    Bancor Formula interface
*/
contract IBancorFormula {
    function calculatePurchaseReturn(uint256 _supply, uint256 _reserveBalance, uint32 _reserveRatio, uint256 _depositAmount) public view returns (uint256);
    function calculateSaleReturn(uint256 _supply, uint256 _reserveBalance, uint32 _reserveRatio, uint256 _sellAmount) public view returns (uint256);
    function calculateCrossReserveReturn(uint256 _fromReserveBalance, uint32 _fromReserveRatio, uint256 _toReserveBalance, uint32 _toReserveRatio, uint256 _amount) public view returns (uint256);
    // deprecated, backward compatibility
    function calculateCrossConnectorReturn(uint256 _fromConnectorBalance, uint32 _fromConnectorWeight, uint256 _toConnectorBalance, uint32 _toConnectorWeight, uint256 _amount) public view returns (uint256);
}

// File: contracts/IBancorNetwork.sol

/*
    Bancor Network interface
*/
contract IBancorNetwork {
    function convert2(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _affiliateAccount,
        uint256 _affiliateFee
    ) public payable returns (uint256);

    function claimAndConvert2(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _affiliateAccount,
        uint256 _affiliateFee
    ) public returns (uint256);

    function convertFor2(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        address _affiliateAccount,
        uint256 _affiliateFee
    ) public payable returns (uint256);

    function claimAndConvertFor2(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        address _affiliateAccount,
        uint256 _affiliateFee
    ) public returns (uint256);

    function convertForPrioritized4(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        uint256[] memory _signature,
        address _affiliateAccount,
        uint256 _affiliateFee
    ) public payable returns (uint256);

    // deprecated, backward compatibility
    function convert(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn
    ) public payable returns (uint256);

    // deprecated, backward compatibility
    function claimAndConvert(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn
    ) public returns (uint256);

    // deprecated, backward compatibility
    function convertFor(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for
    ) public payable returns (uint256);

    // deprecated, backward compatibility
    function claimAndConvertFor(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for
    ) public returns (uint256);

    // deprecated, backward compatibility
    function convertForPrioritized3(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        uint256 _customVal,
        uint256 _block,
        uint8 _v,
        bytes32 _r,
        bytes32 _s
    ) public payable returns (uint256);

    // deprecated, backward compatibility
    function convertForPrioritized2(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        uint256 _block,
        uint8 _v,
        bytes32 _r,
        bytes32 _s
    ) public payable returns (uint256);

    // deprecated, backward compatibility
    function convertForPrioritized(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        uint256 _block,
        uint256 _nonce,
        uint8 _v,
        bytes32 _r,
        bytes32 _s
    ) public payable returns (uint256);
}

// File: contracts/ContractIds.sol

/**
  * @dev Id definitions for bancor contracts
  * 
  * Can be used in conjunction with the contract registry to get contract addresses
*/
contract ContractIds {
    // generic
    bytes32 public constant CONTRACT_FEATURES = "ContractFeatures";
    bytes32 public constant CONTRACT_REGISTRY = "ContractRegistry";
    bytes32 public constant NON_STANDARD_TOKEN_REGISTRY = "NonStandardTokenRegistry";

    // bancor logic
    bytes32 public constant BANCOR_NETWORK = "BancorNetwork";
    bytes32 public constant BANCOR_FORMULA = "BancorFormula";
    bytes32 public constant BANCOR_GAS_PRICE_LIMIT = "BancorGasPriceLimit";
    bytes32 public constant BANCOR_CONVERTER_UPGRADER = "BancorConverterUpgrader";
    bytes32 public constant BANCOR_CONVERTER_FACTORY = "BancorConverterFactory";

    // BNT core
    bytes32 public constant BNT_TOKEN = "BNTToken";

    // BancorX
    bytes32 public constant BANCOR_X = "BancorX";
    bytes32 public constant BANCOR_X_UPGRADER = "BancorXUpgrader";
}

// File: contracts/FeatureIds.sol

/**
  * @dev Id definitions for bancor contract features
  * 
  * Can be used to query the ContractFeatures contract to check whether a certain feature is supported by a contract
*/
contract FeatureIds {
    // converter features
    uint256 public constant CONVERTER_CONVERSION_WHITELIST = 1 << 0;
}

// File: contracts/utility/interfaces/IOwned.sol

/*
    Owned contract interface
*/
contract IOwned {
    // this function isn't abstract since the compiler emits automatically generated getter functions as external
    function owner() public view returns (address) {this;}

    function transferOwnership(address _newOwner) public;
    function acceptOwnership() public;
}

// File: contracts/utility/Owned.sol

/**
  * @dev Provides support and utilities for contract ownership
*/
contract Owned is IOwned {
    address public owner;
    address public newOwner;

    /**
      * @dev triggered when the owner is updated
      * 
      * @param _prevOwner previous owner
      * @param _newOwner  new owner
    */
    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
      * @dev initializes a new Owned instance
    */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        require(msg.sender == owner);
        _;
    }

    /**
      * @dev allows transferring the contract ownership
      * the new owner still needs to accept the transfer
      * can only be called by the contract owner
      * 
      * @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public ownerOnly {
        require(_newOwner != owner);
        newOwner = _newOwner;
    }

    /**
      * @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: contracts/utility/Managed.sol

/**
  * @dev Provides support and utilities for contract management
  * Note that a managed contract must also have an owner
*/
contract Managed is Owned {
    address public manager;
    address public newManager;

    /**
      * @dev triggered when the manager is updated
      * 
      * @param _prevManager previous manager
      * @param _newManager  new manager
    */
    event ManagerUpdate(address indexed _prevManager, address indexed _newManager);

    /**
      * @dev initializes a new Managed instance
    */
    constructor() public {
        manager = msg.sender;
    }

    // allows execution by the manager only
    modifier managerOnly {
        assert(msg.sender == manager);
        _;
    }

    // allows execution by either the owner or the manager only
    modifier ownerOrManagerOnly {
        require(msg.sender == owner || msg.sender == manager);
        _;
    }

    /**
      * @dev allows transferring the contract management
      * the new manager still needs to accept the transfer
      * can only be called by the contract manager
      * 
      * @param _newManager    new contract manager
    */
    function transferManagement(address _newManager) public ownerOrManagerOnly {
        require(_newManager != manager);
        newManager = _newManager;
    }

    /**
      * @dev used by a new manager to accept a management transfer
    */
    function acceptManagement() public {
        require(msg.sender == newManager);
        emit ManagerUpdate(manager, newManager);
        manager = newManager;
        newManager = address(0);
    }
}

// File: contracts/utility/Utils.sol

/**
  * @dev Utilities & Common Modifiers
*/
contract Utils {
    /**
      * constructor
    */
    constructor() public {
    }

    // verifies that an amount is greater than zero
    modifier greaterThanZero(uint256 _amount) {
        require(_amount > 0);
        _;
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != address(0));
        _;
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        require(_address != address(this));
        _;
    }

}

// File: contracts/utility/SafeMath.sol

/**
  * @dev Library for basic math operations with overflow/underflow protection
*/
library SafeMath {
    /**
      * @dev returns the sum of _x and _y, reverts if the calculation overflows
      * 
      * @param _x   value 1
      * @param _y   value 2
      * 
      * @return sum
    */
    function add(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x + _y;
        require(z >= _x);
        return z;
    }

    /**
      * @dev returns the difference of _x minus _y, reverts if the calculation underflows
      * 
      * @param _x   minuend
      * @param _y   subtrahend
      * 
      * @return difference
    */
    function sub(uint256 _x, uint256 _y) internal pure returns (uint256) {
        require(_x >= _y);
        return _x - _y;
    }

    /**
      * @dev returns the product of multiplying _x by _y, reverts if the calculation overflows
      * 
      * @param _x   factor 1
      * @param _y   factor 2
      * 
      * @return product
    */
    function mul(uint256 _x, uint256 _y) internal pure returns (uint256) {
        // gas optimization
        if (_x == 0)
            return 0;

        uint256 z = _x * _y;
        require(z / _x == _y);
        return z;
    }

      /**
        * ev Integer division of two numbers truncating the quotient, reverts on division by zero.
        * 
        * aram _x   dividend
        * aram _y   divisor
        * 
        * eturn quotient
    */
    function div(uint256 _x, uint256 _y) internal pure returns (uint256) {
        require(_y > 0);
        uint256 c = _x / _y;

        return c;
    }
}

// File: contracts/utility/interfaces/IContractRegistry.sol

/*
    Contract Registry interface
*/
contract IContractRegistry {
    function addressOf(bytes32 _contractName) public view returns (address);

    // deprecated, backward compatibility
    function getAddress(bytes32 _contractName) public view returns (address);
}

// File: contracts/utility/interfaces/IContractFeatures.sol

/*
    Contract Features interface
*/
contract IContractFeatures {
    function isSupported(address _contract, uint256 _features) public view returns (bool);
    function enableFeatures(uint256 _features, bool _enable) public;
}

// File: contracts/utility/interfaces/IAddressList.sol

/*
    Address list interface
*/
contract IAddressList {
    mapping (address => bool) public listedAddresses;
}

// File: contracts/token/interfaces/ISmartToken.sol

/*
    Smart Token interface
*/
contract ISmartToken is IOwned, IERC20Token {
    function disableTransfers(bool _disable) public;
    function issue(address _to, uint256 _amount) public;
    function destroy(address _from, uint256 _amount) public;
}

// File: contracts/token/interfaces/ISmartTokenController.sol

/*
    Smart Token Controller interface
*/
contract ISmartTokenController {
    function claimTokens(address _from, uint256 _amount) public;
    function token() public view returns (ISmartToken) {this;}
}

// File: contracts/utility/interfaces/ITokenHolder.sol

/*
    Token Holder interface
*/
contract ITokenHolder is IOwned {
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount) public;
}

// File: contracts/token/interfaces/INonStandardERC20.sol

/*
    ERC20 Standard Token interface which doesn't return true/false for transfer, transferFrom and approve
*/
contract INonStandardERC20 {
    // these functions aren't abstract since the compiler emits automatically generated getter functions as external
    function name() public view returns (string) {this;}
    function symbol() public view returns (string) {this;}
    function decimals() public view returns (uint8) {this;}
    function totalSupply() public view returns (uint256) {this;}
    function balanceOf(address _owner) public view returns (uint256) {_owner; this;}
    function allowance(address _owner, address _spender) public view returns (uint256) {_owner; _spender; this;}

    function transfer(address _to, uint256 _value) public;
    function transferFrom(address _from, address _to, uint256 _value) public;
    function approve(address _spender, uint256 _value) public;
}

// File: contracts/utility/TokenHolder.sol

/**
  * @dev We consider every contract to be a 'token holder' since it's currently not possible
  * for a contract to deny receiving tokens.
  * 
  * The TokenHolder's contract sole purpose is to provide a safety mechanism that allows
  * the owner to send tokens that were sent to the contract by mistake back to their sender.
  * 
  * Note that we use the non standard ERC-20 interface which has no return value for transfer
  * in order to support both non standard as well as standard token contracts.
  * see https://github.com/ethereum/solidity/issues/4116
*/
contract TokenHolder is ITokenHolder, Owned, Utils {
    /**
      * @dev initializes a new TokenHolder instance
    */
    constructor() public {
    }

    /**
      * @dev withdraws tokens held by the contract and sends them to an account
      * can only be called by the owner
      * 
      * @param _token   ERC20 token contract address
      * @param _to      account to receive the new amount
      * @param _amount  amount to withdraw
    */
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount)
        public
        ownerOnly
        validAddress(_token)
        validAddress(_to)
        notThis(_to)
    {
        INonStandardERC20(_token).transfer(_to, _amount);
    }
}

// File: contracts/token/SmartTokenController.sol

/**
  * @dev The smart token controller is an upgradable part of the smart token that allows
  * more functionality as well as fixes for bugs/exploits.
  * Once it accepts ownership of the token, it becomes the token's sole controller
  * that can execute any of its functions.
  * 
  * To upgrade the controller, ownership must be transferred to a new controller, along with
  * any relevant data.
  * 
  * The smart token must be set on construction and cannot be changed afterwards.
  * Wrappers are provided (as opposed to a single 'execute' function) for each of the token's functions, for easier access.
  * 
  * Note that the controller can transfer token ownership to a new controller that
  * doesn't allow executing any function on the token, for a trustless solution.
  * Doing that will also remove the owner's ability to upgrade the controller.
*/
contract SmartTokenController is ISmartTokenController, TokenHolder {
    ISmartToken public token;   // Smart Token contract
    address public bancorX;     // BancorX contract

    /**
      * @dev initializes a new SmartTokenController instance
      * 
      * @param  _token      smart token governed by the controller
    */
    constructor(ISmartToken _token)
        public
        validAddress(_token)
    {
        token = _token;
    }

    // ensures that the controller is the token's owner
    modifier active() {
        require(token.owner() == address(this));
        _;
    }

    // ensures that the controller is not the token's owner
    modifier inactive() {
        require(token.owner() != address(this));
        _;
    }

    /**
      * @dev allows transferring the token ownership
      * the new owner needs to accept the transfer
      * can only be called by the contract owner
      * 
      * @param _newOwner    new token owner
    */
    function transferTokenOwnership(address _newOwner) public ownerOnly {
        token.transferOwnership(_newOwner);
    }

    /**
      * @dev used by a new owner to accept a token ownership transfer
      * can only be called by the contract owner
    */
    function acceptTokenOwnership() public ownerOnly {
        token.acceptOwnership();
    }

    /**
      * @dev withdraws tokens held by the controller and sends them to an account
      * can only be called by the owner
      * 
      * @param _token   ERC20 token contract address
      * @param _to      account to receive the new amount
      * @param _amount  amount to withdraw
    */
    function withdrawFromToken(IERC20Token _token, address _to, uint256 _amount) public ownerOnly {
        ITokenHolder(token).withdrawTokens(_token, _to, _amount);
    }

    /**
      * @dev allows the associated BancorX contract to claim tokens from any address (so that users
      * dont have to first give allowance when calling BancorX)
      * 
      * @param _from      address to claim the tokens from
      * @param _amount    the amount of tokens to claim
     */
    function claimTokens(address _from, uint256 _amount) public {
        // only the associated BancorX contract may call this method
        require(msg.sender == bancorX);

        // destroy the tokens belonging to _from, and issue the same amount to bancorX
        token.destroy(_from, _amount);
        token.issue(msg.sender, _amount);
    }

    /**
      * @dev allows the owner to set the associated BancorX contract
      * @param _bancorX    BancorX contract
     */
    function setBancorX(address _bancorX) public ownerOnly {
        bancorX = _bancorX;
    }
}

// File: contracts/token/interfaces/IEtherToken.sol

/*
    Ether Token interface
*/
contract IEtherToken is ITokenHolder, IERC20Token {
    function deposit() public payable;
    function withdraw(uint256 _amount) public;
    function withdrawTo(address _to, uint256 _amount) public;
}

// File: contracts/bancorx/interfaces/IBancorX.sol

contract IBancorX {
    function xTransfer(bytes32 _toBlockchain, bytes32 _to, uint256 _amount, uint256 _id) public;
    function getXTransferAmount(uint256 _xTransferId, address _for) public view returns (uint256);
}

// File: contracts/converter/BancorConverter.sol

/**
  * @dev Bancor Converter
  * 
  * The Bancor converter allows for conversions between a Smart Token and other ERC20 tokens and between different ERC20 tokens and themselves. 
  * 
  * The ERC20 reserve balance can be virtual, meaning that conversions between reserve tokens are based on the virtual balance instead of relying on the actual reserve balance.
  * 
  * This mechanism opens the possibility to create different financial tools (for example, lower slippage in conversions).
  * 
  * The converter is upgradable (just like any SmartTokenController) and all upgrades are opt-in. 
  * 
  * WARNING: It is NOT RECOMMENDED to use the converter with Smart Tokens that have less than 8 decimal digits or with very small numbers because of precision loss 
  * 
  * Open issues:
  * - Front-running attacks are currently mitigated by the following mechanisms:
  *     - minimum return argument for each conversion provides a way to define a minimum/maximum price for the transaction
  *     - gas price limit prevents users from having control over the order of execution
  *     - gas price limit check can be skipped if the transaction comes from a trusted, whitelisted signer
  * 
  * Other potential solutions might include a commit/reveal based schemes
  * - Possibly add getters for the reserve fields so that the client won't need to rely on the order in the struct
*/
contract BancorConverter is IBancorConverter, SmartTokenController, Managed, ContractIds, FeatureIds {
    using SafeMath for uint256;

    uint32 private constant RATIO_RESOLUTION = 1000000;
    uint64 private constant CONVERSION_FEE_RESOLUTION = 1000000;

    struct Reserve {
        uint256 virtualBalance;         // reserve virtual balance
        uint32 ratio;                   // reserve ratio, represented in ppm, 1-1000000
        bool isVirtualBalanceEnabled;   // true if virtual balance is enabled, false if not
        bool isSaleEnabled;             // is sale of the reserve token enabled, can be set by the owner
        bool isSet;                     // used to tell if the mapping element is defined
    }

    /**
      * @dev version number
    */
    uint16 public version = 20;
    string public converterType = 'bancor';

    bool public allowRegistryUpdate = true;             // allows the owner to prevent/allow the registry to be updated
    IContractRegistry public prevRegistry;              // address of previous registry as security mechanism
    IContractRegistry public registry;                  // contract registry contract
    IWhitelist public conversionWhitelist;              // whitelist contract with list of addresses that are allowed to use the converter
    IERC20Token[] public reserveTokens;                 // ERC20 standard token addresses (prior version 17, use 'connectorTokens' instead)
    mapping (address => Reserve) public reserves;       // reserve token addresses -> reserve data (prior version 17, use 'connectors' instead)
    uint32 private totalReserveRatio = 0;               // used to efficiently prevent increasing the total reserve ratio above 100%
    uint32 public maxConversionFee = 0;                 // maximum conversion fee for the lifetime of the contract,
                                                        // represented in ppm, 0...1000000 (0 = no fee, 100 = 0.01%, 1000000 = 100%)
    uint32 public conversionFee = 0;                    // current conversion fee, represented in ppm, 0...maxConversionFee
    bool public conversionsEnabled = true;              // true if token conversions is enabled, false if not

    /**
      * @dev triggered when a conversion between two tokens occurs
      * 
      * @param _fromToken       ERC20 token converted from
      * @param _toToken         ERC20 token converted to
      * @param _trader          wallet that initiated the trade
      * @param _amount          amount converted, in fromToken
      * @param _return          amount returned, minus conversion fee
      * @param _conversionFee   conversion fee
    */
    event Conversion(
        address indexed _fromToken,
        address indexed _toToken,
        address indexed _trader,
        uint256 _amount,
        uint256 _return,
        int256 _conversionFee
    );

    /**
      * @dev triggered after a conversion with new price data
      * 
      * @param  _connectorToken     reserve token
      * @param  _tokenSupply        smart token supply
      * @param  _connectorBalance   reserve balance
      * @param  _connectorWeight    reserve ratio
    */
    event PriceDataUpdate(
        address indexed _connectorToken,
        uint256 _tokenSupply,
        uint256 _connectorBalance,
        uint32 _connectorWeight
    );

    /**
      * @dev triggered when the conversion fee is updated
      * 
      * @param  _prevFee    previous fee percentage, represented in ppm
      * @param  _newFee     new fee percentage, represented in ppm
    */
    event ConversionFeeUpdate(uint32 _prevFee, uint32 _newFee);

    /**
      * @dev triggered when conversions are enabled/disabled
      * 
      * @param  _conversionsEnabled true if conversions are enabled, false if not
    */
    event ConversionsEnable(bool _conversionsEnabled);

    /**
      * @dev triggered when virtual balances are enabled/disabled
      * 
      * @param  _enabled true if virtual balances are enabled, false if not
    */
    event VirtualBalancesEnable(bool _enabled);

    /**
      * @dev initializes a new BancorConverter instance
      * 
      * @param  _token              smart token governed by the converter
      * @param  _registry           address of a contract registry contract
      * @param  _maxConversionFee   maximum conversion fee, represented in ppm
      * @param  _reserveToken       optional, initial reserve, allows defining the first reserve at deployment time
      * @param  _reserveRatio       optional, ratio for the initial reserve
    */
    constructor(
        ISmartToken _token,
        IContractRegistry _registry,
        uint32 _maxConversionFee,
        IERC20Token _reserveToken,
        uint32 _reserveRatio
    )
        public
        SmartTokenController(_token)
        validAddress(_registry)
        validConversionFee(_maxConversionFee)
    {
        registry = _registry;
        prevRegistry = _registry;
        IContractFeatures features = IContractFeatures(registry.addressOf(ContractIds.CONTRACT_FEATURES));

        // initialize supported features
        if (features != address(0))
            features.enableFeatures(FeatureIds.CONVERTER_CONVERSION_WHITELIST, true);

        maxConversionFee = _maxConversionFee;

        if (_reserveToken != address(0))
            addReserve(_reserveToken, _reserveRatio);
    }

    // validates a reserve token address - verifies that the address belongs to one of the reserve tokens
    modifier validReserve(IERC20Token _address) {
        require(reserves[_address].isSet);
        _;
    }

    // validates conversion fee
    modifier validConversionFee(uint32 _conversionFee) {
        require(_conversionFee >= 0 && _conversionFee <= CONVERSION_FEE_RESOLUTION);
        _;
    }

    // validates reserve ratio
    modifier validReserveRatio(uint32 _ratio) {
        require(_ratio > 0 && _ratio <= RATIO_RESOLUTION);
        _;
    }

    // allows execution only when the total ratio is 100%
    modifier fullTotalRatioOnly() {
        require(totalReserveRatio == RATIO_RESOLUTION);
        _;
    }

    // allows execution only when conversions aren't disabled
    modifier conversionsAllowed {
        require(conversionsEnabled);
        _;
    }

    // allows execution by the BancorNetwork contract only
    modifier bancorNetworkOnly {
        IBancorNetwork bancorNetwork = IBancorNetwork(registry.addressOf(ContractIds.BANCOR_NETWORK));
        require(msg.sender == address(bancorNetwork));
        _;
    }

    // allows execution by the converter upgrader contract only
    modifier converterUpgraderOnly {
        address converterUpgrader = registry.addressOf(ContractIds.BANCOR_CONVERTER_UPGRADER);
        require(msg.sender == converterUpgrader);
        _;
    }

    // allows execution only if the total-supply of the token is greater than zero
    modifier totalSupplyGreaterThanZeroOnly {
        require(token.totalSupply() > 0);
        _;
    }

    /**
      * @dev sets the contract registry to whichever address the current registry is pointing to
     */
    function updateRegistry() public {
        // require that upgrading is allowed or that the caller is the owner
        require(allowRegistryUpdate || msg.sender == owner);

        // get the address of whichever registry the current registry is pointing to
        address newRegistry = registry.addressOf(ContractIds.CONTRACT_REGISTRY);

        // if the new registry hasn't changed or is the zero address, revert
        require(newRegistry != address(registry) && newRegistry != address(0));

        // set the previous registry as current registry and current registry as newRegistry
        prevRegistry = registry;
        registry = IContractRegistry(newRegistry);
    }

    /**
      * @dev security mechanism allowing the converter owner to revert to the previous registry,
      * to be used in emergency scenario
    */
    function restoreRegistry() public ownerOrManagerOnly {
        // set the registry as previous registry
        registry = prevRegistry;

        // after a previous registry is restored, only the owner can allow future updates
        allowRegistryUpdate = false;
    }

    /**
      * @dev disables the registry update functionality
      * this is a safety mechanism in case of a emergency
      * can only be called by the manager or owner
      * 
      * @param _disable    true to disable registry updates, false to re-enable them
    */
    function disableRegistryUpdate(bool _disable) public ownerOrManagerOnly {
        allowRegistryUpdate = !_disable;
    }

    /**
      * @dev returns the number of reserve tokens defined
      * note that prior to version 17, you should use 'connectorTokenCount' instead
      * 
      * @return number of reserve tokens
    */
    function reserveTokenCount() public view returns (uint16) {
        return uint16(reserveTokens.length);
    }

    /**
      * @dev allows the owner to update & enable the conversion whitelist contract address
      * when set, only addresses that are whitelisted are actually allowed to use the converter
      * note that the whitelist check is actually done by the BancorNetwork contract
      * 
      * @param _whitelist    address of a whitelist contract
    */
    function setConversionWhitelist(IWhitelist _whitelist)
        public
        ownerOnly
        notThis(_whitelist)
    {
        conversionWhitelist = _whitelist;
    }

    /**
      * @dev disables the entire conversion functionality
      * this is a safety mechanism in case of a emergency
      * can only be called by the manager
      * 
      * @param _disable true to disable conversions, false to re-enable them
    */
    function disableConversions(bool _disable) public ownerOrManagerOnly {
        if (conversionsEnabled == _disable) {
            conversionsEnabled = !_disable;
            emit ConversionsEnable(conversionsEnabled);
        }
    }

    /**
      * @dev allows transferring the token ownership
      * the new owner needs to accept the transfer
      * can only be called by the contract owner
      * note that token ownership can only be transferred while the owner is the converter upgrader contract
      * 
      * @param _newOwner    new token owner
    */
    function transferTokenOwnership(address _newOwner)
        public
        ownerOnly
        converterUpgraderOnly
    {
        super.transferTokenOwnership(_newOwner);
    }

    /**
      * @dev used by a new owner to accept a token ownership transfer
      * can only be called by the contract owner
      * note that token ownership can only be accepted if its total-supply is greater than zero
    */
    function acceptTokenOwnership()
        public
        ownerOnly
        totalSupplyGreaterThanZeroOnly
    {
        super.acceptTokenOwnership();
    }

    /**
      * @dev updates the current conversion fee
      * can only be called by the manager
      * 
      * @param _conversionFee new conversion fee, represented in ppm
    */
    function setConversionFee(uint32 _conversionFee)
        public
        ownerOrManagerOnly
    {
        require(_conversionFee >= 0 && _conversionFee <= maxConversionFee);
        emit ConversionFeeUpdate(conversionFee, _conversionFee);
        conversionFee = _conversionFee;
    }

    /**
      * @dev given a return amount, returns the amount minus the conversion fee
      * 
      * @param _amount      return amount
      * @param _magnitude   1 for standard conversion, 2 for cross reserve conversion
      * 
      * @return return amount minus conversion fee
    */
    function getFinalAmount(uint256 _amount, uint8 _magnitude) public view returns (uint256) {
        return _amount.mul((CONVERSION_FEE_RESOLUTION - conversionFee) ** _magnitude).div(CONVERSION_FEE_RESOLUTION ** _magnitude);
    }

    /**
      * @dev withdraws tokens held by the converter and sends them to an account
      * can only be called by the owner
      * note that reserve tokens can only be withdrawn by the owner while the converter is inactive
      * unless the owner is the converter upgrader contract
      * 
      * @param _token   ERC20 token contract address
      * @param _to      account to receive the new amount
      * @param _amount  amount to withdraw
    */
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount) public {
        address converterUpgrader = registry.addressOf(ContractIds.BANCOR_CONVERTER_UPGRADER);

        // if the token is not a reserve token, allow withdrawal
        // otherwise verify that the converter is inactive or that the owner is the upgrader contract
        require(!reserves[_token].isSet || token.owner() != address(this) || owner == converterUpgrader);
        super.withdrawTokens(_token, _to, _amount);
    }

    /**
      * @dev upgrades the converter to the latest version
      * can only be called by the owner
      * note that the owner needs to call acceptOwnership/acceptManagement on the new converter after the upgrade
    */
    function upgrade() public ownerOnly {
        IBancorConverterUpgrader converterUpgrader = IBancorConverterUpgrader(registry.addressOf(ContractIds.BANCOR_CONVERTER_UPGRADER));

        transferOwnership(converterUpgrader);
        converterUpgrader.upgrade(version);
        acceptOwnership();
    }

    /**
      * @dev defines a new reserve for the token
      * can only be called by the owner while the converter is inactive
      * note that prior to version 17, you should use 'addConnector' instead
      * 
      * @param _token                  address of the reserve token
      * @param _ratio                  constant reserve ratio, represented in ppm, 1-1000000
    */
    function addReserve(IERC20Token _token, uint32 _ratio)
        public
        ownerOnly
        inactive
        validAddress(_token)
        notThis(_token)
        validReserveRatio(_ratio)
    {
        require(_token != token && !reserves[_token].isSet && totalReserveRatio + _ratio <= RATIO_RESOLUTION); // validate input

        reserves[_token].ratio = _ratio;
        reserves[_token].isVirtualBalanceEnabled = false;
        reserves[_token].virtualBalance = 0;
        reserves[_token].isSaleEnabled = true;
        reserves[_token].isSet = true;
        reserveTokens.push(_token);
        totalReserveRatio += _ratio;
    }

    /**
      * @dev updates a reserve's virtual balance
      * only used during an upgrade process
      * can only be called by the contract owner while the owner is the converter upgrader contract
      * note that prior to version 17, you should use 'updateConnector' instead
      * 
      * @param _reserveToken    address of the reserve token
      * @param _virtualBalance  new reserve virtual balance, or 0 to disable virtual balance
    */
    function updateReserveVirtualBalance(IERC20Token _reserveToken, uint256 _virtualBalance)
        public
        ownerOnly
        converterUpgraderOnly
        validReserve(_reserveToken)
    {
        Reserve storage reserve = reserves[_reserveToken];
        reserve.isVirtualBalanceEnabled = _virtualBalance != 0;
        reserve.virtualBalance = _virtualBalance;
    }

    /**
      * @dev enables virtual balance for the reserves
      * virtual balance only affects conversions between reserve tokens
      * virtual balance of all reserves can only scale by the same factor, to keep the ratio between them the same
      * note that the balance is determined during the execution of this function and set statically -
      * meaning that it's not calculated dynamically based on the factor after each conversion
      * can only be called by the contract owner while the converter is active
      * 
      * @param _scaleFactor  percentage, 100-1000 (100 = no virtual balance, 1000 = virtual balance = actual balance * 10)
    */
    function enableVirtualBalances(uint16 _scaleFactor)
        public
        ownerOnly
        active
    {
        // validate input
        require(_scaleFactor >= 100 && _scaleFactor <= 1000);
        bool enable = _scaleFactor != 100;

        // iterate through the reserves and scale their balance by the ratio provided,
        // or disable virtual balance altogether if a factor of 100% is passed in
        IERC20Token reserveToken;
        for (uint16 i = 0; i < reserveTokens.length; i++) {
            reserveToken = reserveTokens[i];
            Reserve storage reserve = reserves[reserveToken];
            reserve.isVirtualBalanceEnabled = enable;
            reserve.virtualBalance = enable ? reserveToken.balanceOf(this).mul(_scaleFactor).div(100) : 0;
        }

        emit VirtualBalancesEnable(enable);
    }

    /**
      * @dev disables converting from the given reserve token in case the reserve token got compromised
      * can only be called by the owner
      * note that converting to the token is still enabled regardless of this flag and it cannot be disabled by the owner
      * note that prior to version 17, you should use 'disableConnectorSale' instead
      * 
      * @param _reserveToken    reserve token contract address
      * @param _disable         true to disable the token, false to re-enable it
    */
    function disableReserveSale(IERC20Token _reserveToken, bool _disable)
        public
        ownerOnly
        validReserve(_reserveToken)
    {
        reserves[_reserveToken].isSaleEnabled = !_disable;
    }

    /**
      * @dev returns the reserve's virtual balance if one is defined, otherwise returns the actual balance
      * note that prior to version 17, you should use 'getConnectorBalance' instead
      * 
      * @param _reserveToken    reserve token contract address
      * 
      * @return reserve balance
    */
    function getReserveBalance(IERC20Token _reserveToken)
        public
        view
        validReserve(_reserveToken)
        returns (uint256)
    {
        Reserve storage reserve = reserves[_reserveToken];
        return reserve.isVirtualBalanceEnabled ? reserve.virtualBalance : _reserveToken.balanceOf(this);
    }

    /**
      * @dev calculates the expected return of converting a given amount of tokens
      * 
      * @param _fromToken  contract address of the token to convert from
      * @param _toToken    contract address of the token to convert to
      * @param _amount     amount of tokens received from the user
      * 
      * @return amount of tokens that the user will receive
      * @return amount of tokens that the user will pay as fee
    */
    function getReturn(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount) public view returns (uint256, uint256) {
        require(_fromToken != _toToken); // validate input

        // conversion between the token and one of its reserves
        if (_toToken == token)
            return getPurchaseReturn(_fromToken, _amount);
        else if (_fromToken == token)
            return getSaleReturn(_toToken, _amount);

        // conversion between 2 reserves
        return getCrossReserveReturn(_fromToken, _toToken, _amount);
    }

    /**
      * @dev calculates the expected return of buying with a given amount of tokens
      * 
      * @param _reserveToken    contract address of the reserve token
      * @param _depositAmount   amount of reserve-tokens received from the user
      * 
      * @return amount of supply-tokens that the user will receive
      * @return amount of supply-tokens that the user will pay as fee
    */
    function getPurchaseReturn(IERC20Token _reserveToken, uint256 _depositAmount)
        public
        view
        active
        validReserve(_reserveToken)
        returns (uint256, uint256)
    {
        Reserve storage reserve = reserves[_reserveToken];
        require(reserve.isSaleEnabled); // validate input

        uint256 tokenSupply = token.totalSupply();
        uint256 reserveBalance = _reserveToken.balanceOf(this);
        IBancorFormula formula = IBancorFormula(registry.addressOf(ContractIds.BANCOR_FORMULA));
        uint256 amount = formula.calculatePurchaseReturn(tokenSupply, reserveBalance, reserve.ratio, _depositAmount);
        uint256 finalAmount = getFinalAmount(amount, 1);

        // return the amount minus the conversion fee and the conversion fee
        return (finalAmount, amount - finalAmount);
    }

    /**
      * @dev calculates the expected return of selling a given amount of tokens
      * 
      * @param _reserveToken    contract address of the reserve token
      * @param _sellAmount      amount of supply-tokens received from the user
      * 
      * @return amount of reserve-tokens that the user will receive
      * @return amount of reserve-tokens that the user will pay as fee
    */
    function getSaleReturn(IERC20Token _reserveToken, uint256 _sellAmount)
        public
        view
        active
        validReserve(_reserveToken)
        returns (uint256, uint256)
    {
        Reserve storage reserve = reserves[_reserveToken];
        uint256 tokenSupply = token.totalSupply();
        uint256 reserveBalance = _reserveToken.balanceOf(this);
        IBancorFormula formula = IBancorFormula(registry.addressOf(ContractIds.BANCOR_FORMULA));
        uint256 amount = formula.calculateSaleReturn(tokenSupply, reserveBalance, reserve.ratio, _sellAmount);
        uint256 finalAmount = getFinalAmount(amount, 1);

        // return the amount minus the conversion fee and the conversion fee
        return (finalAmount, amount - finalAmount);
    }

    /**
      * @dev calculates the expected return of converting a given amount from one reserve to another
      * note that prior to version 17, you should use 'getCrossConnectorReturn' instead
      * 
      * @param _fromReserveToken    contract address of the reserve token to convert from
      * @param _toReserveToken      contract address of the reserve token to convert to
      * @param _amount              amount of tokens received from the user
      * 
      * @return amount of tokens that the user will receive
      * @return amount of tokens that the user will pay as fee
    */
    function getCrossReserveReturn(IERC20Token _fromReserveToken, IERC20Token _toReserveToken, uint256 _amount)
        public
        view
        active
        validReserve(_fromReserveToken)
        validReserve(_toReserveToken)
        returns (uint256, uint256)
    {
        Reserve storage fromReserve = reserves[_fromReserveToken];
        Reserve storage toReserve = reserves[_toReserveToken];
        require(fromReserve.isSaleEnabled); // validate input

        IBancorFormula formula = IBancorFormula(registry.addressOf(ContractIds.BANCOR_FORMULA));
        uint256 amount = formula.calculateCrossReserveReturn(
            getReserveBalance(_fromReserveToken), 
            fromReserve.ratio, 
            getReserveBalance(_toReserveToken), 
            toReserve.ratio, 
            _amount);
        uint256 finalAmount = getFinalAmount(amount, 2);

        // return the amount minus the conversion fee and the conversion fee
        // the fee is higher (magnitude = 2) since cross reserve conversion equals 2 conversions (from / to the smart token)
        return (finalAmount, amount - finalAmount);
    }

    /**
      * @dev converts a specific amount of _fromToken to _toToken
      * can only be called by the bancor network contract
      * 
      * @param _fromToken  ERC20 token to convert from
      * @param _toToken    ERC20 token to convert to
      * @param _amount     amount to convert, in fromToken
      * @param _minReturn  if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero
      * 
      * @return conversion return amount
    */
    function convertInternal(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn)
        public
        bancorNetworkOnly
        conversionsAllowed
        greaterThanZero(_minReturn)
        returns (uint256)
    {
        require(_fromToken != _toToken); // validate input

        // conversion between the token and one of its reserves
        if (_toToken == token)
            return buy(_fromToken, _amount, _minReturn);
        else if (_fromToken == token)
            return sell(_toToken, _amount, _minReturn);

        uint256 amount;
        uint256 feeAmount;

        // conversion between 2 reserves
        (amount, feeAmount) = getCrossReserveReturn(_fromToken, _toToken, _amount);
        // ensure the trade gives something in return and meets the minimum requested amount
        require(amount != 0 && amount >= _minReturn);

        // update the source token virtual balance if relevant
        Reserve storage fromReserve = reserves[_fromToken];
        if (fromReserve.isVirtualBalanceEnabled)
            fromReserve.virtualBalance = fromReserve.virtualBalance.add(_amount);

        // update the target token virtual balance if relevant
        Reserve storage toReserve = reserves[_toToken];
        if (toReserve.isVirtualBalanceEnabled)
            toReserve.virtualBalance = toReserve.virtualBalance.sub(amount);

        // ensure that the trade won't deplete the reserve balance
        uint256 toReserveBalance = getReserveBalance(_toToken);
        assert(amount < toReserveBalance);

        // transfer funds from the caller in the from reserve token
        ensureTransferFrom(_fromToken, msg.sender, this, _amount);
        // transfer funds to the caller in the to reserve token
        // the t...

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