• Head over to the Firebase Console.
• Click on "Create a project" and just follow the steps on the screen.
• Once your project is up and running, open it and pick the "Realtime Database" option from the menu on the left.
• Click "Create Database," choose your region, and set your database rules.

• Start a new Node.js project or go to your existing one.
• Run npm install firebase to get the Firebase dependency.
• Make a firebaseConfig.js file in your project and add this code:

const firebase = require('firebase/app');
require('firebase/database');

const firebaseConfig = {
  apiKey: "<YOUR_API_KEY>",
  authDomain: "<YOUR_AUTH_DOMAIN>",
  databaseURL: "<YOUR_DATABASE_URL>",
  projectId: "<YOUR_PROJECT_ID>",
  storageBucket: "<YOUR_STORAGE_BUCKET>",
  messagingSenderId: "<YOUR_MESSAGING_SENDER_ID>",
  appId: "<YOUR_APP_ID>",
};

firebase.initializeApp(firebaseConfig);

module.exports = firebase.database();

Replace those placeholders with your Firebase project's details, which you can find in the Firebase Console under Project Settings.

Let's use Apollo Server for our GraphQL server:

• Run npm install apollo-server graphql to get the needed dependencies.
• Create a server.js file and add this code:

const { ApolloServer, gql } = require('apollo-server');
const database = require('./firebaseConfig');

// Define your type definitions
const typeDefs = gql`
  type Query {
    getMessage(id: String!): String
  }

  type Mutation {
    addMessage(id: String!, message: String!): String
  }
`;

// Define your resolvers
const resolvers = {
  Query: {
    getMessage: async (_, { id }) => {
      const snapshot = await database.ref('messages').child(id).once('value');
      return snapshot.val();
    },
  },
  Mutation: {
    addMessage: async (_, { id, message }) => {
      await database.ref('messages').child(id).set(message);
      return message;
    },
  },
};

// Create the Apollo Server instance
const server = new ApolloServer({ typeDefs, resolvers });

// Start the server
server.listen().then(({ url }) => {
  console.log(`Server ready at ${url}`);
});

• Run node server.js to get your GraphQL server going.
• Check if it's running by visiting the local URL (usually http://localhost:4000) shown in the console.

• Use a GraphQL client like Apollo Client, Postman, or the Apollo Server's built-in playground.
• Test the queries and mutations you defined in the typeDefs.

Example Queries and Mutations:

# Query Example
query {
  getMessage(id: "1")
}

# Mutation Example
mutation {
  addMessage(id: "1", message: "Hello, Firebase!")
}

Make sure the data is being read from and written to your Firebase Realtime Database correctly.

• Go back to the Firebase Console.
• Navigate to "Realtime Database" > "Rules".
• Update the rules to define who can read/write data.

Example rules:

{
  "rules": {
    ".read": "auth != null",
    ".write": "auth != null",
  }
}

These rules make sure only authenticated users can read or write to the database. Adjust them based on what your app needs.