conflux开发NFT智能合约（ERC721 & 工厂合约 & 可升级合约）

以下场景可借鉴本文内容

• 需要创建很多合约
• 需要使用conflux代付机制（只需将工厂合约设置为代付，即可无限创建新合约）
• 合约想要有可升级的能力（如：特殊玩法 or 代码有bug）
• ERC-721 NFT

基于以上场景，需要三个主要合约实现

• 工厂合约
• 代理合约
• 逻辑合约

想要完全掌握本文内容，你需要提前了解

• Conflux交易详解：https://juejin.cn/post/6971741780429668365
• conflux-rpc文档：OPEN-RPC Playground
• NFT开发示例：https://forum.conflux.fun/t/conflux-2022-5-18-721-20-721-1155-nft/8781
• conflux metadata: https://forum.conflux.fun/t/conflux-metadata/16083
• "数字藏品"开发规范：https://forum.conflux.fun/t/conflux/15538
• 合约之间互相调用：https://zhuanlan.zhihu.com/p/503497056
• 可升级合约：https://learnblockchain.cn/article/4257
• 工厂 + 代理：http://t.csdn.cn/aym0I
• eip1967: https://zhuanlan.zhihu.com/p/480217161

代码实现

1、工厂合约（创建代理合约、创建逻辑合约、代付）

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@confluxfans/contracts/InternalContracts/InternalContractsHandler.sol";
import "./Monkey.sol";
import "./MonkeyProxy.sol";
import "./CloneFactory.sol";


interface LogicInterface {
    function initialize(string memory name, string memory symbol, string memory uri) external;
}

interface ProxyInterface {

    function mint(address to, uint256 tokenId) external;

    function transfer(address from, address to, uint256 tokenId) external;

    function burn(uint256 tokenId) external;
}

contract MonkeyFactory is CloneFactory {
    address private _admin;
    address private _logicTemplate;

    SponsorWhitelistControl constant private SPONSOR = SponsorWhitelistControl(0x0888000000000000000000000000000000000001);

    constructor(address admin, address logicTemplate) public{
        _admin = admin;
        _logicTemplate = logicTemplate;
        _addPrivilege(admin);
    }

    function _addPrivilege(address admin) private {
        address[] memory addressList = new address[](1);
        addressList[0] = admin;
        SPONSOR.addPrivilege(addressList);
    }

    function updateLogicTemplate(address logicTemplate) public {
        require(_admin == msg.sender, "MonkeyFactory: must have admin role");
        _logicTemplate = logicTemplate;
    }

    function createLogic() external returns(address){
        require(_admin == msg.sender, "MonkeyFactory: must have admin role");

        LogicInterface logic = LogicInterface(createClone(_logicTemplate));

        return address(logic); // 这里可以考虑使用event
    }

    function createProxy(address logicAddr, string memory name, string memory symbol, string memory uri) external returns(address){
        require(_admin == msg.sender, "MonkeyFactory: must have admin role");

        bytes memory initData = abi.encodeWithSignature("initialize(string,string,string)", name, symbol, uri);

        MonkeyProxy proxy = new MonkeyProxy(logicAddr, initData);

        return address(proxy);  // 这里可以考虑使用event
    }

    function upgradeLogic(address proxyAddr, address newAddress) public{
        require(_admin == msg.sender, "MonkeyFactory: must have admin role");

        (bool _ok, bytes memory ret) = proxyAddr.call(abi.encodeWithSignature(
            "upgradeVersion(address,address)", newAddress
        ));
        require(_ok, string(ret));
    }

    function mint(address proxyAddr, address to, uint256 tokenId) public{
        require(_admin == msg.sender, "MonkeyFactory: must have admin role");

        ProxyInterface proxy = ProxyInterface(proxyAddr);

        proxy.mint(to, tokenId);
        
        // 如果使用featureCode，可以在这里继续操作，其他代码则按需实现
    }

    function transfer(address proxyAddr, address from, address to, uint256 tokenId) external {
        require(_admin == msg.sender, "MonkeyFactory: must have admin role");

        ProxyInterface proxy = ProxyInterface(proxyAddr);

        proxy.transfer(from, to, tokenId);
    }

    function burn(address proxyAddr, uint256 tokenId) external {
        require(_admin == msg.sender, "MonkeyFactory: must have admin role");

        ProxyInterface proxy = ProxyInterface(proxyAddr);

        proxy.burn(tokenId);
    }
    // 考虑使用fallback调用代理合约，即使方法变更，也可以正常发起调用
}

2、代理合约

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

// 看明白这个合约，先了解下eip-1967，很多代码是固定写法
contract MonkeyProxy {
    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-1967.md
    bytes32 internal constant _ADMIN_SLOT = 0xb53127684a568b3173ae13b9f8a6016e243e63b6e8ee1178d6a717850b5d6103;
    bytes32 internal constant _IMPLEMENTATION_SLOT = 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;
    
    constructor(address logic, bytes memory initData) { 
        require(logic != address(0),"MonkeyProxy: wrong proxy contract address");
        StorageSlotUpgradeable.getAddressSlot(_ADMIN_SLOT).value = msg.sender;
        StorageSlotUpgradeable.getAddressSlot(_IMPLEMENTATION_SLOT).value = logic;
        (bool _ok, bytes memory returnData) = logic.delegatecall(initData);
        require(_ok, string(returnData));
    }
    
    // 基本是固定写法
    fallback() external payable {
        address _impl = StorageSlotUpgradeable.getAddressSlot(_IMPLEMENTATION_SLOT).value;
        assembly {
            let ptr := mload(0x40)
            calldatacopy(ptr, 0, calldatasize())
            let result := delegatecall(gas(), _impl, ptr, calldatasize(), 0, 0)
            let size := returndatasize()
            returndatacopy(ptr, 0, size)
            switch result
                case 0 {
                    revert(ptr, size)
                }
                default {
                    return(ptr, size)
                }
        }
    }

    function upgradeVersion(address newAddress) public {
        require(StorageSlotUpgradeable.getAddressSlot(_ADMIN_SLOT).value == msg.sender, "MonkeyProxy: only admin can be modified");
        StorageSlotUpgradeable.getAddressSlot(_IMPLEMENTATION_SLOT).value = newAddress;
    }
}

3、逻辑合约

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@confluxfans/contracts/token/CRC721/extensions/CRC721Enumerable.sol";
import "@openzeppelin/contracts/access/AccessControlEnumerable.sol";
import "./Initializable.sol";

contract Monkey is AccessControlEnumerable, CRC721Enumerable, Initializable {
    using Strings for uint256;

    string private _name;
    string private _symbol;
    string private _uri;

    mapping(uint256 => uint256) public tokenFeatureCode;

    bytes32 public constant MINTER_ROLE = keccak256("MINTER_ROLE");

    constructor() public ERC721("", "") {}

    function initialize(string memory name, string memory symbol, string memory uri) public initializer {
        _setupRole(DEFAULT_ADMIN_ROLE, msg.sender);
        _setupRole(MINTER_ROLE, msg.sender);
        _name = name;
        _symbol  = symbol;
        setURI(uri);
    }

    function name() public view virtual override returns (string memory) {
        return _name;
    }

    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    function setURI(string memory newuri) public virtual {
        require(hasRole(DEFAULT_ADMIN_ROLE, _msgSender()), "Monkey: must have admin role to set URI");
        _uri = newuri;
    }

    function _baseURI() internal view virtual override returns (string memory) {
        return _uri;
    }

    function tokenURI(uint256 tokenId) public view virtual override(ERC721)  returns (string memory) {
        require(_exists(tokenId), "Monkey: nonexistent token");
        string memory baseURI = _baseURI();
        return bytes(baseURI).length > 0 ? string(abi.encodePacked(baseURI, tokenId.toString(), ".json")) : "";
    }

    function mint(address to, uint256 tokenId) public virtual {
        require(hasRole(MINTER_ROLE, _msgSender()), "Monkey: must have minter role to mint");
        _mint(to, tokenId);
    }

    function burn(uint256 tokenId) public virtual {
        require(hasRole(MINTER_ROLE, _msgSender()), "Monkey: must have admin role to burn");
        _burn(tokenId);
    } 

    function transfer(address from, address to, uint256 tokenId) public virtual {
        require(hasRole(MINTER_ROLE, _msgSender()), "Monkey: must have admin role to transfer");
        _transfer(from, to, tokenId);
    }

    function setTokenFeatureCode(uint256 tokenId, uint256 featureCode) public virtual {
        require(hasRole(MINTER_ROLE, _msgSender()), "Monkey: must have minter role to mint");
        require(tokenFeatureCode[tokenId] == 0, "Monkey: token feature code is already set up");
        tokenFeatureCode[tokenId] = featureCode;
    }

    function addMinter(address minter) external {
        require(hasRole(DEFAULT_ADMIN_ROLE, _msgSender()), "Monkey: must have admin role to add minter");
        grantRole(MINTER_ROLE, minter);
    }

    function removeMinter(address minter) external {
        require(hasRole(DEFAULT_ADMIN_ROLE, _msgSender()), "Monkey: must have admin role to remove minter");
        revokeRole(MINTER_ROLE, minter);
    }

    /**
     * See {IERC165-supportsInterface}
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override(AccessControlEnumerable, ERC721Enumerable) returns (bool) {
        return AccessControlEnumerable.supportsInterface(interfaceId) || ERC721Enumerable.supportsInterface(interfaceId);
    }
}

代码中用到的工具类、库都可以找到开源代码，若有需要可点赞、留言，或私聊，小的会补充