// SPDX-License-Identifier: MIT
// vuln-code-snippet start nftUnlockChallenge
pragma solidity ^0.8.4;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Counters.sol";

contract JuiceShopSBT is ERC721, ERC721URIStorage, Ownable {
    using Counters for Counters.Counter;

    Counters.Counter private _tokenIdCounter;

    constructor() ERC721("JuiceShopSBT", "JS") {}

    function safeMint(address to, string memory uri) public onlyOwner {
        uint256 tokenId = _tokenIdCounter.current(); // vuln-code-snippet vuln-line nftUnlockChallenge
        _tokenIdCounter.increment();
        _safeMint(to, tokenId);
        _setTokenURI(tokenId, uri);
    }

    function _beforeTokenTransfer(
    address from,
    address to,
    uint256 tokenId // vuln-code-snippet neutral-line nftUnlockChallenge
    ) internal override virtual {
    require(from == address(0), "Err: token transfer is BLOCKED");
    super._beforeTokenTransfer(from, to, tokenId);
    }

    function _burn(uint256 tokenId) internal override(ERC721, ERC721URIStorage) { // vuln-code-snippet neutral-line nftUnlockChallenge
        super._burn(tokenId);
    }

    function tokenURI(uint256 tokenId) // vuln-code-snippet neutral-line nftUnlockChallenge
        public
        view
        override(ERC721, ERC721URIStorage)
        returns (string memory)
    {
        return super.tokenURI(tokenId);
    }
}
// vuln-code-snippet end nftUnlockChallenge