contract SiringClockAuction is ClockAuction {

    // @dev Sanity check that allows us to ensure that we are pointing to the
    //  right auction in our setSiringAuctionAddress() call.
    bool public isSiringClockAuction = true;

    // Delegate constructor
    function SiringClockAuction(address _nftAddr, uint256 _cut) public
        ClockAuction(_nftAddr, _cut) {}

    /// @dev Creates and begins a new auction. Since this function is wrapped,
    /// require sender to be KittyCore contract.
    /// @param _tokenId - ID of token to auction, sender must be owner.
    /// @param _startingPrice - Price of item (in wei) at beginning of auction.
    /// @param _endingPrice - Price of item (in wei) at end of auction.
    /// @param _duration - Length of auction (in seconds).
    /// @param _seller - Seller, if not the message sender
    function createAuction(
        uint256 _tokenId,
        uint256 _startingPrice,
        uint256 _endingPrice,
        uint256 _duration,
        address _seller
    )
        external
    {
        // Sanity check that no inputs overflow how many bits we've allocated
        // to store them in the auction struct.
        require(_startingPrice == uint256(uint128(_startingPrice)));
        require(_endingPrice == uint256(uint128(_endingPrice)));
        require(_duration == uint256(uint64(_duration)));

        require(msg.sender == address(nonFungibleContract));
        _escrow(_seller, _tokenId);
        Auction memory auction = Auction(
            _seller,
            uint128(_startingPrice),
            uint128(_endingPrice),
            uint64(_duration),
            uint64(now)
        );
        _addAuction(_tokenId, auction);
    }

    /// @dev Places a bid for siring. Requires the sender
    /// is the KittyCore contract because all bid methods
    /// should be wrapped. Also returns the kitty to the
    /// seller rather than the winner.
    function bid(uint256 _tokenId)
        external
        payable
    {
        require(msg.sender == address(nonFungibleContract));
        address seller = tokenIdToAuction[_tokenId].seller;
        // _bid checks that token ID is valid and will throw if bid fails
        _bid(_tokenId, msg.value);
        // We transfer the kitty back to the seller, the winner will get
        // the offspring
        _transfer(seller, _tokenId);
    }

}
/// @title Reverse auction modified for siring
/// @notice We omit a fallback function to prevent accidental sends to this contract.
function createAuction(
    uint256 _tokenId,
    uint256 _startingPrice,
    uint256 _endingPrice,
    uint256 _duration,
    address _seller
)
    external
{
    // Sanity check that no inputs overflow how many bits we've allocated
    // to store them in the auction struct.
    require(_startingPrice == uint256(uint128(_startingPrice)));
    require(_endingPrice == uint256(uint128(_endingPrice)));
    require(_duration == uint256(uint64(_duration)));

    require(msg.sender == address(nonFungibleContract));
    _escrow(_seller, _tokenId);
    Auction memory auction = Auction(
        _seller,
        uint128(_startingPrice),
        uint128(_endingPrice),
        uint64(_duration),
        uint64(now)
    );
    _addAuction(_tokenId, auction);
}

/// @dev Creates and begins a new auction. Since this function is wrapped,
/// require sender to be KittyCore contract.
/// @param _tokenId - ID of token to auction, sender must be owner.
/// @param _startingPrice - Price of item (in wei) at beginning of auction.
/// @param _endingPrice - Price of item (in wei) at end of auction.
/// @param _duration - Length of auction (in seconds).
/// @param _seller - Seller, if not the message sender