contract ContractRegistryClient is Owned, Utils {
    bytes32 internal constant CONTRACT_REGISTRY = "ContractRegistry";
    bytes32 internal constant BANCOR_NETWORK = "BancorNetwork";
    bytes32 internal constant CONVERTER_FACTORY = "ConverterFactory";
    bytes32 internal constant CONVERSION_PATH_FINDER = "ConversionPathFinder";
    bytes32 internal constant CONVERTER_UPGRADER = "BancorConverterUpgrader";
    bytes32 internal constant CONVERTER_REGISTRY = "BancorConverterRegistry";
    bytes32 internal constant CONVERTER_REGISTRY_DATA = "BancorConverterRegistryData";
    bytes32 internal constant BNT_TOKEN = "BNTToken";
    bytes32 internal constant BANCOR_X = "BancorX";
    bytes32 internal constant BANCOR_X_UPGRADER = "BancorXUpgrader";
    bytes32 internal constant LIQUIDITY_PROTECTION = "LiquidityProtection";
    bytes32 internal constant NETWORK_SETTINGS = "NetworkSettings";

    // address of the current contract registry
    IContractRegistry private _registry;

    // address of the previous contract registry
    IContractRegistry private _prevRegistry;

    // only the owner can update the contract registry
    bool private _onlyOwnerCanUpdateRegistry;

    /**
     * @dev verifies that the caller is mapped to the given contract name
     */
    modifier only(bytes32 contractName) {
        _only(contractName);
        _;
    }

    // error message binary size optimization
    function _only(bytes32 contractName) internal view {
        require(msg.sender == _addressOf(contractName), "ERR_ACCESS_DENIED");
    }

    /**
     * @dev initializes a new ContractRegistryClient instance
     */
    constructor(IContractRegistry initialRegistry) internal validAddress(address(initialRegistry)) {
        _registry = IContractRegistry(initialRegistry);
        _prevRegistry = IContractRegistry(initialRegistry);
    }

    /**
     * @dev updates to the new contract registry
     */
    function updateRegistry() external {
        // verify that this function is permitted
        require(msg.sender == owner() || !_onlyOwnerCanUpdateRegistry, "ERR_ACCESS_DENIED");

        // get the new contract registry
        IContractRegistry newRegistry = IContractRegistry(_addressOf(CONTRACT_REGISTRY));

        // verify that the new contract registry is different and not zero
        require(newRegistry != _registry && address(newRegistry) != address(0), "ERR_INVALID_REGISTRY");

        // verify that the new contract registry is pointing to a non-zero contract registry
        require(newRegistry.addressOf(CONTRACT_REGISTRY) != address(0), "ERR_INVALID_REGISTRY");

        // save a backup of the current contract registry before replacing it
        _prevRegistry = _registry;

        // replace the current contract registry with the new contract registry
        _registry = newRegistry;
    }

    /**
     * @dev restores the previous contract registry
     */
    function restoreRegistry() external ownerOnly {
        // restore the previous contract registry
        _registry = _prevRegistry;
    }

    /**
     * @dev restricts the permission to update the contract registry
     */
    function restrictRegistryUpdate(bool restrictOwnerOnly) public ownerOnly {
        // change the permission to update the contract registry
        _onlyOwnerCanUpdateRegistry = restrictOwnerOnly;
    }

    /**
     * @dev returns the address of the current contract registry
     */
    function registry() public view returns (IContractRegistry) {
        return _registry;
    }

    /**
     * @dev returns the address of the previous contract registry
     */
    function prevRegistry() external view returns (IContractRegistry) {
        return _prevRegistry;
    }

    /**
     * @dev returns whether only the owner can update the contract registry
     */
    function onlyOwnerCanUpdateRegistry() external view returns (bool) {
        return _onlyOwnerCanUpdateRegistry;
    }

    /**
     * @dev returns the address associated with the given contract name
     */
    function _addressOf(bytes32 contractName) internal view returns (address) {
        return _registry.addressOf(contractName);
    }
}
/**
 * @dev This is the base contract for ContractRegistry clients.
 */
function registry() public view returns (IContractRegistry) {
        return _registry;
    }
/**
 * @dev returns the address of the current contract registry
 */