Implementing a simple blockchain oracle on Ethereum

Conference.sol

// SPDX-License-Identifier: MIT
pragma solidity 0.8.17;

import "./TicketsFeedInterface.sol";

contract Conference {
    TicketsFeedInterface ticketsFeed;

    constructor(address _ticketsFeed) {
        ticketsFeed = TicketsFeedInterface(_ticketsFeed);
    }

    function checkPrice(uint256 payment, uint256 price) internal pure {
        require(payment == price, "Not enouth ETH to buy a ticket");
    }

    function buyTicket() public payable {
        uint256 ticketsSold = ticketsFeed.getData();

        if (ticketsSold < 10) { checkPrice(msg.value, 0.01 ether); }
        else if (ticketsSold < 100) { checkPrice(msg.value, 0.1 ether); }
        else { checkPrice(msg.value, 1 ether); }

        // Ticket buying logic
    }
}

TicketsFeed.js

const ethers = require('ethers');

// JSON of the compiled TicketsFeed contract
const TicketsFeed = require('./TicketsFeed.json');

// Address of the deployed TicketsFeed oracle contract
const TicketsFeedAddress = '0x';

const BLOCKCHAIN_NODE_URL = '';
const PRIVATE_KEY = '0x';

// The logic for calculating the number of sold tickets
function getTicketsSoldNumber() {
    return 102;
}

async function main() {
    // Get instances of provider and signer to be able to interact with the blockchain
    const provider = new ethers.providers.JsonRpcProvider(BLOCKCHAIN_NODE_URL);
    const signer = new ethers.Wallet(PRIVATE_KEY, provider);

    // Create an instance of deployed oracle contract
    const TicketsFeedContract = new ethers.Contract(TicketsFeedAddress, TicketsFeed.abi, signer);
    
    // Retrieve data: it can be an API call, database query, etc.
    const ticketsSold = getTicketsSoldNumber();

    // Create setData transaction
    const sendDataTx = await TicketsFeedContract.setData(ticketsSold);

    // Wait for the transaction to be applied
    await sendDataTx.wait();
}
  
main().catch((error) => {
    console.error(error);
});

TicketsFeed.sol

// SPDX-License-Identifier: MIT
pragma solidity 0.8.17;

import "@openzeppelin/contracts/access/Ownable.sol";

import "./TicketsFeedInterface.sol";

contract TicketsFeed is Ownable, TicketsFeedInterface {
    uint256 private ticketsSold;

    function getData() public view returns (uint256) {
        return ticketsSold;
    }

    function setData(uint256 _ticketsSold) external onlyOwner {
        ticketsSold = _ticketsSold;
    }
}

TicketsFeedInterface.sol

// SPDX-License-Identifier: MIT
pragma solidity 0.8.17;

interface TicketsFeedInterface {
    function getData() external view returns(uint256);
    function setData(uint256 ticketsSold) external; 
}