import { getFirestore } from 'firebase-admin/firestore';

const db = getFirestore();

// Storing
const buffer = Buffer.from('hello world', 'utf-8');
// From a file: const buffer = fs.readFileSync('./image.png');

await db.collection('files').doc('doc-id').set({
  data: buffer,  // Buffer is accepted directly by the Admin SDK
});

// Retrieving — comes back as Buffer on Node.js
const snap = await db.collection('files').doc('doc-id').get();
const retrieved: Buffer = snap.data()!.data;
console.log(retrieved.toString('utf-8')); // 'hello world'

import { getFirestore, doc, setDoc, getDoc, Bytes } from 'firebase/firestore';

const db = getFirestore();

// Storing — wrap your Uint8Array in Bytes
const uint8 = new TextEncoder().encode('hello world');

await setDoc(doc(db, 'files', 'doc-id'), {
  data: Bytes.fromUint8Array(uint8),
  // or from base64: Bytes.fromBase64String('aGVsbG8gd29ybGQ=')
});

// Retrieving
const snap = await getDoc(doc(db, 'files', 'doc-id'));
const bytes: Bytes = snap.data()!.data;
const decoded = new TextDecoder().decode(bytes.toUint8Array());
console.log(decoded); // 'hello world'