shobhitic/LazyNFT.sol

## index.html
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>LazyMinting</title>
  <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/ethers/5.6.9/ethers.umd.min.js"></script>
</head>
<body>
  <script type="text/javascript">
    const SIGNING_DOMAIN_NAME = "Voucher-Domain"
    const SIGNING_DOMAIN_VERSION = "1"
    const chainId = 1
    const contractAddress = "0xa131AD247055FD2e2aA8b156A11bdEc81b9eAD95" // Put the address here from remix
    const signer = new ethers.Wallet("503f38a9c967ed597e47fe25643985f032b072db8075426a92110f82df48dfcb") // private key that I use for address 0x5B38Da6a701c568545dCfcB03FcB875f56beddC4

    const domain = {
      name: SIGNING_DOMAIN_NAME,
      version: SIGNING_DOMAIN_VERSION,
      verifyingContract: contractAddress,
      chainId
    }

    async function createVoucher(tokenId, price, uri, buyer) {
      const voucher = { tokenId, price, uri, buyer }
      const types = {
        LazyNFTVoucher: [
          {name: "tokenId", type: "uint256"},
          {name: "price", type: "uint256"},
          {name: "uri", type: "string"},
          {name: "buyer", type: "address"}
        ]
      }

      const signature = await signer._signTypedData(domain, types, voucher)
      return {
        ...voucher,
        signature
      }
    }

    async function main() {
      const voucher = await createVoucher(5, 50, "uri", "0x5B38Da6a701c568545dCfcB03FcB875f56beddC4") // the address is the address which receives the NFT
      console.log(`[${voucher.tokenId}, ${voucher.price}, "${voucher.uri}", "${voucher.buyer}", "${voucher.signature}"]`)
    }
  </script>
</body>
</html>

## LazyNFT.sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

import "@openzeppelin/contracts@4.7.3/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts@4.7.3/token/ERC721/extensions/ERC721URIStorage.sol";
import "@openzeppelin/contracts@4.7.3/access/Ownable.sol";
import "@openzeppelin/contracts@4.7.3/utils/cryptography/draft-EIP712.sol";

contract LazyNFT is ERC721, ERC721URIStorage, Ownable, EIP712 {
    string private constant SIGNING_DOMAIN = "Voucher-Domain";
    string private constant SIGNATURE_VERSION = "1";
    address public minter;

    constructor(address _minter) ERC721("LazyNFT", "LNFT") EIP712(SIGNING_DOMAIN, SIGNATURE_VERSION) {
        minter = _minter;
    }

    struct LazyNFTVoucher {
        uint256 tokenId;
        uint256 price;
        string uri;
        address buyer;
        bytes signature;
    }

    function recover(LazyNFTVoucher calldata voucher) public view returns (address) {
        bytes32 digest = _hashTypedDataV4(keccak256(abi.encode(
            keccak256("LazyNFTVoucher(uint256 tokenId,uint256 price,string uri,address buyer)"),
            voucher.tokenId,
            voucher.price,
            keccak256(bytes(voucher.uri)),
            voucher.buyer
        )));
        address signer = ECDSA.recover(digest, voucher.signature);
        return signer;
    }

    function safeMint(LazyNFTVoucher calldata voucher)
        public
        payable
    {
        require(minter == recover(voucher), "Wrong signature.");
        require(msg.value >= voucher.price, "Not enough ether sent.");
        _safeMint(voucher.buyer, voucher.tokenId);
        _setTokenURI(voucher.tokenId, voucher.uri);
    }

    // The following functions are overrides required by Solidity.

    function _burn(uint256 tokenId) internal override(ERC721, ERC721URIStorage) {
        super._burn(tokenId);
    }

    function tokenURI(uint256 tokenId)
        public
        view
        override(ERC721, ERC721URIStorage)
        returns (string memory)
    {
        return super.tokenURI(tokenId);
    }
}
	<!DOCTYPE html>
	<html>
	<head>
	<meta charset="utf-8">
	<meta name="viewport" content="width=device-width, initial-scale=1">
	<title>LazyMinting</title>
	<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/ethers/5.6.9/ethers.umd.min.js"></script>
	</head>
	<body>
	<script type="text/javascript">
	const SIGNING_DOMAIN_NAME = "Voucher-Domain"
	const SIGNING_DOMAIN_VERSION = "1"
	const chainId = 1
	const contractAddress = "0xa131AD247055FD2e2aA8b156A11bdEc81b9eAD95" // Put the address here from remix
	const signer = new ethers.Wallet("503f38a9c967ed597e47fe25643985f032b072db8075426a92110f82df48dfcb") // private key that I use for address 0x5B38Da6a701c568545dCfcB03FcB875f56beddC4

	const domain = {
	name: SIGNING_DOMAIN_NAME,
	version: SIGNING_DOMAIN_VERSION,
	verifyingContract: contractAddress,
	chainId
	}

	async function createVoucher(tokenId, price, uri, buyer) {
	const voucher = { tokenId, price, uri, buyer }
	const types = {
	LazyNFTVoucher: [
	{name: "tokenId", type: "uint256"},
	{name: "price", type: "uint256"},
	{name: "uri", type: "string"},
	{name: "buyer", type: "address"}
	]
	}

	const signature = await signer._signTypedData(domain, types, voucher)
	return {
	...voucher,
	signature
	}
	}

	async function main() {
	const voucher = await createVoucher(5, 50, "uri", "0x5B38Da6a701c568545dCfcB03FcB875f56beddC4") // the address is the address which receives the NFT
	console.log(`[${voucher.tokenId}, ${voucher.price}, "${voucher.uri}", "${voucher.buyer}", "${voucher.signature}"]`)
	}
	</script>
	</body>
	</html>
	// SPDX-License-Identifier: MIT
	pragma solidity ^0.8.4;

	import "@openzeppelin/contracts@4.7.3/token/ERC721/ERC721.sol";
	import "@openzeppelin/contracts@4.7.3/token/ERC721/extensions/ERC721URIStorage.sol";
	import "@openzeppelin/contracts@4.7.3/access/Ownable.sol";
	import "@openzeppelin/contracts@4.7.3/utils/cryptography/draft-EIP712.sol";

	contract LazyNFT is ERC721, ERC721URIStorage, Ownable, EIP712 {
	string private constant SIGNING_DOMAIN = "Voucher-Domain";
	string private constant SIGNATURE_VERSION = "1";
	address public minter;

	constructor(address _minter) ERC721("LazyNFT", "LNFT") EIP712(SIGNING_DOMAIN, SIGNATURE_VERSION) {
	minter = _minter;
	}

	struct LazyNFTVoucher {
	uint256 tokenId;
	uint256 price;
	string uri;
	address buyer;
	bytes signature;
	}

	function recover(LazyNFTVoucher calldata voucher) public view returns (address) {
	bytes32 digest = _hashTypedDataV4(keccak256(abi.encode(
	keccak256("LazyNFTVoucher(uint256 tokenId,uint256 price,string uri,address buyer)"),
	voucher.tokenId,
	voucher.price,
	keccak256(bytes(voucher.uri)),
	voucher.buyer
	)));
	address signer = ECDSA.recover(digest, voucher.signature);
	return signer;
	}

	function safeMint(LazyNFTVoucher calldata voucher)
	public
	payable
	{
	require(minter == recover(voucher), "Wrong signature.");
	require(msg.value >= voucher.price, "Not enough ether sent.");
	_safeMint(voucher.buyer, voucher.tokenId);
	_setTokenURI(voucher.tokenId, voucher.uri);
	}

	// The following functions are overrides required by Solidity.

	function _burn(uint256 tokenId) internal override(ERC721, ERC721URIStorage) {
	super._burn(tokenId);
	}

	function tokenURI(uint256 tokenId)
	public
	view
	override(ERC721, ERC721URIStorage)
	returns (string memory)
	{
	return super.tokenURI(tokenId);
	}
	}