deploy.js

const main = async () => {
  const gameContractFactory = await hre.ethers.getContractFactory('MyEpicGame');
  const gameContract = await gameContractFactory.deploy(
    [0, 1, 2],                           
    ["Leo", "Aang", "Tom Brady"],       
    ["https://i.imgur.com/pKd5Sdk.png", 
    "https://i.imgur.com/xVu4vFL.png", 
    "https://i.imgur.com/FcXCH9W.jpg"],
    [100, 200, 300],                    
    [100, 50, 25]                       
  );
  await gameContract.deployed();
  console.log("Contract deployed to:", gameContract.address);

  
  let txn;
  txn = await gameContract.mintCharacterNFT(0);
  txn.wait();

  txn = await gameContract.mintCharacterNFT(1);
  txn.wait();

  txn = await gameContract.mintCharacterNFT(1);
  txn.wait();

  txn = await gameContract.mintCharacterNFT(2);
  txn.wait();

  console.log("Done deploying and minting!");

};

const runMain = async () => {
  try {
    await main();
    process.exit(0);
  } catch (error) {
    console.log(error);
    process.exit(1);
  }
};

runMain();

MyEpicGame.sol

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

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

import "@openzeppelin/contracts/utils/Counters.sol";
import "@openzeppelin/contracts/utils/Strings.sol";

// String encoding libraries
import { Base64 } from "./libraries/Base64.sol";

import "hardhat/console.sol";


contract MyEpicGame is ERC721 {

  struct CharacterAttributes {
    string name;
    string imageURI;        
    uint hp;
    uint attackDamage;
  }

  using Counters for Counters.Counter;
  Counters.Counter private _tokenIds;

  mapping(uint => CharacterAttributes) public defaultAttributes;
  mapping(uint256 => CharacterAttributes) public nftHolderAttributes;

  constructor(
    uint[] memory characterIds,
    string[] memory characterNames,
    string[] memory characterImageURIs,
    uint[] memory characterHp,
    uint[] memory characterAttackDmg
  )
    ERC721("Heroes", "HERO")
  {
    for(uint i = 0; i < characterIds.length; i += 1) {
      defaultAttributes[characterIds[i]] = CharacterAttributes({
        name: characterNames[i],
        imageURI: characterImageURIs[i],
        hp: characterHp[i],
        attackDamage: characterAttackDmg[i]
      });

      CharacterAttributes memory c = defaultAttributes[characterIds[i]];
      console.log("Done initializing %s w/ HP %s, img %s", c.name, c.hp, c.imageURI);
    }
  }

  function tokenURI(uint256 _tokenId) public view override returns (string memory) {
    CharacterAttributes memory charAttributes = nftHolderAttributes[_tokenId];

    string memory strHp = Strings.toString(charAttributes.hp);
    string memory strAttackDamage = Strings.toString(charAttributes.attackDamage);

    string memory json = Base64.encode(
      bytes(
        string(
          abi.encodePacked(
            '{"name": "',
            charAttributes.name,
            ' -- NFT #: ',
            Strings.toString(_tokenId),
            '", "description": "CriticalHit is a turn-based NFT game where you take turns to attack the boos.", "image": "',
            charAttributes.imageURI,
            '", "attributes": [ { "trait_type": "Health Points", "value": ',strHp,', "max_value": 300 }, { "trait_type": "Attack Damage", "value": ',
            strAttackDamage,', "max_value": 400} ]}'
          )
        )
      )
    );

    string memory output = string(
      abi.encodePacked("data:application/json;base64,", json)
    );
    
    return output;
  }

  function mintCharacterNFT(uint _characterId) external {
    uint256 newItemId = _tokenIds.current();

    _safeMint(msg.sender, newItemId);

    nftHolderAttributes[newItemId] = CharacterAttributes({
      name: defaultAttributes[_characterId].name,
      imageURI: defaultAttributes[_characterId].imageURI,
      hp: defaultAttributes[_characterId].hp,
      attackDamage: defaultAttributes[_characterId].attackDamage
    });

    console.log("Minted NFT w/ tokenId %s and characterId %s", newItemId, _characterId);
    _tokenIds.increment();
  }
}

run.js

const main = async () => {
  const gameContractFactory = await hre.ethers.getContractFactory('MyEpicGame');
  const gameContract = await gameContractFactory.deploy(
    [0, 1, 2],                           
    ["Leo", "Aang", "Tom Brady"],       
    ["https://i.imgur.com/pKd5Sdk.png", 
    "https://i.imgur.com/xVu4vFL.png", 
    "https://i.imgur.com/FcXCH9W.jpg"],
    [100, 200, 300],                    
    [100, 50, 25]                       
  );
  await gameContract.deployed();
  console.log("Contract deployed to:", gameContract.address);

  
  let txn;
  txn = await gameContract.mintCharacterNFT(0);
  txn.wait();

  txn = await gameContract.mintCharacterNFT(1);
  txn.wait();

  txn = await gameContract.mintCharacterNFT(1);
  txn.wait();

  txn = await gameContract.mintCharacterNFT(2);
  txn.wait();

  console.log("Done deploying and minting!");

};

const runMain = async () => {
  try {
    await main();
    process.exit(0);
  } catch (error) {
    console.log(error);
    process.exit(1);
  }
};

runMain();