Sponsored ERC721

Repository for the basic tools in javascript and golang for integrating Conflux Network NFTs (ERC-721) into applications. The following details how to mint, get address NFT ids, and set up transaction sponsorship (optional).

The above illustrates a basic PoC of integrating NFTs into a game. The game only need to track the user's address in their account. The backend needs to interface with the Conflux Network blockchain to send/mint assets for each user, and also retrieve data. The marketplace for trading assets can be handled by third-party marketplaces that aggregate NFTs/game assets from any game - which is the unique functionality that blockchain enables: cross-game assets.

This repository details the middleware layer of providing easy to use/integrate functions for games to connect NFTs to a game.

Contract

ERC721 Contract from OpenZeppelin with slight modification to expose the mint functionality:

// SPDX-License-Identifier: WTFPL

pragma solidity ^0.6.0;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";

contract NFTBase is ERC721 {
    address private owner;

    constructor() ERC721("MyCollectible", "MCO") public {
      owner = msg.sender;
    }

    //exposing the safe mint function
    function safeMint(address to, uint256 tokenId) public {
      require(msg.sender == owner, "NFTBase: Only owner can mint");
      _safeMint(to, tokenId);
    }

    function safeMint(address to, uint256 tokenId, bytes calldata _data) public {
      require(msg.sender == owner, "NFTBase: Only owner can mint");
      _safeMint(to, tokenId, _data);
    }

}

Then the contract is:

• Compiled using conflux-truffle (cfxtruffle compile)
• ABI/bytecode used for deployment

Deploy

Javascript files for deploying NFT contract and setting up transaction sponsorship.

Function	Details
node deploy <KEY_ENV>	Deploy the corresponding ERC721 contract to Conflux testnet
node sponsor <KEY_ENV> <CONTRACT_ADDR>	Send CFX as sponsor for gas and collateral
node checkSponsor <CONTRACT_ADDR>	Check sponsorship parameters of contract address
node addSponsored <KEY_ENV> <CONTRACT_ADDR> <SPONSORED_ADDR>	Admin can add an address as a sponsored address for smart contract interaction
node isSponsered <CONTRACT_ADDR> <USER_ADDR>	Check if user is sponsored for the smart contract
node destroy <KEY_ENV> <CONTRACT_ADDR>	Destroy the contract and unstake storage collateral (only contract admin can call)

Example

Sample .env file:

ENDPOINT=http://test.confluxrpc.org
PRIVATE_KEY1=0x<private_key>
PRIVATE_KEY2=0x<private_key>

Sample function calls:

//for deploying contract
node deploy PRIVATE_KEY1
node sponsor PRIVATE_KEY2 0x8aa092e0660c59eab456efdbd39ae8d158e9a95b
node checkSponsor 0x8aa092e0660c59eab456efdbd39ae8d158e9a95b
node addSponsored PRIVATE_KEY1 0x8aa092e0660c59eab456efdbd39ae8d158e9a95b 0x15fd1E4F13502b1a8BE110F100EC001d0270552d
node isSponsored 0x8aa092e0660c59eab456efdbd39ae8d158e9a95b 0x15fd1E4F13502b1a8BE110F100EC001d0270552d

//for destroying contract
node destroy PRIVATE_KEY1 0x8aa092e0660c59eab456efdbd39ae8d158e9a95b

Note: PRIVATE_KEY1 is the creator of the contract and is the default admin, so it is used in the addSponsored command. PRIVATE_KEY2 is used to represent any sponsor.

Contract address (testnet): 0x8aa092e0660c59eab456efdbd39ae8d158e9a95b

Resources

Sponsorship contract interface: https://github.com/Conflux-Chain/conflux-rust/blob/master/internal_contract/contracts/SponsorWhitelistControl.sol
Documentation: https://developer.conflux-chain.org/docs/conflux-rust/internal_contract/internal_contract#sponsorwhitelistcontrol-contract

Packages

Once the previous steps are followed to deploying a smart contract, the following packages in go or javascript can be used to interact with the contract to mint and read data.

All packages follow the same basic format for functions (Note: Function capitalization may be different depending on the package. See examples for usage):

Name	Input	Output	Functionality
constructor	endpoint, NFT address	nft object	Constructor for creating the NFT instance for use
mint	user address, nft ID	transaction hash	Mint NFT (of specific ID) to a user's wallet
getAssets	user address	array of nft IDs	Get a list of NFT IDs for the specific user

A .env file is required to provide the Conflux Network private key for the NFT smart contract deployer.

PRIVATE_KEY=<insert-private-key>

Javascript

yarn add @aalu1418/sponsored-erc721

Example + Usage

Go

go get github.com/Conflux-Network-Global/sponsored-erc721/golang

Example + Usage

Other Languages

There is plenty of room for improvement!

• Python
• .NET
• C++
• etc