function end() external { require(started, "not started"); require(block.timestamp >= endAt, "not ended"); require(!ended, "ended"); ended = true; if (highestBidder != address(0)) { nft.safeTransferFrom(address(this), highestBidder, nftId); seller.transfer(highestBid); } else { nft.safeTransferFrom(address(this), seller, nftId); } emit End(highestBidder, highestBid); } 0.7.1