DCIPs/assets/eip-5008/contracts/ERC5008.sol

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// SPDX-License-Identifier: CC0-1.0
pragma solidity ^0.8.0;
import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "./IERC5008.sol";
contract ERC5008 is ERC721, IERC5008 {
mapping(uint256 => uint256) private _tokenNonce;
constructor(string memory name_, string memory symbol_)ERC721(name_, symbol_){
}
/// @notice Get the nonce of an NFT
/// Throws if `tokenId` is not a valid NFT
/// @param tokenId The NFT to get the nonce for
/// @return The nonce of this NFT
function nonce(uint256 tokenId) public virtual override view returns(uint256) {
require(_exists(tokenId), "Error: query for nonexistent token");
return _tokenNonce[tokenId];
}
function _beforeTokenTransfer(
address from,
address to,
uint256 tokenId
) internal virtual override{
super._beforeTokenTransfer(from, to, tokenId);
_tokenNonce[tokenId]++;
}
/// @dev See {IERC165-supportsInterface}.
function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
return interfaceId == type(IERC5008).interfaceId || super.supportsInterface(interfaceId);
}
}