init

.gitignore

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+.env
+database-key.json
+dist
+node_modules

package.json

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+{
+  "name": "mongo-firebase-backuper",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "type": "commonjs",
+  "dependencies": {
+    "@types/node": "^25.0.3",
+    "dotenv": "^17.2.3",
+    "firebase-admin": "^13.6.0",
+    "mongodb": "^7.0.0",
+    "node-cron": "^4.2.1",
+    "ts-node": "^10.9.2",
+    "typescript": "^5.9.3"
+  }
+}

src/firebase.ts

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+import admin from "firebase-admin";
+import serviceAccount from "../database-key.json";
+
+admin.initializeApp({
+  credential: admin.credential.cert(
+    serviceAccount as admin.ServiceAccount
+  ),
+  databaseURL: "https://pixel-battlegrounds-6c5a7-default-rtdb.firebaseio.com"
+});
+
+export const rtdb = admin.database();
+

src/index.ts

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+import "dotenv/config";
+import cron from "node-cron";
+import { syncPlayers } from "./sync";
+import { syncMongoToFirebase } from "./syncReverse"; // new function
+
+async function main() {
+  const args = process.argv.slice(2);
+
+  if (args.includes("--one-time")) {
+    console.log("🔹 Running one-time Mongo → Firebase sync...");
+    try {
+      await syncMongoToFirebase();
+      console.log("✅ One-time sync finished");
+    } catch (e) {
+      console.error("One-time sync error:", e);
+    }
+    process.exit(0); // exit after one-time run
+  }
+
+  // Default: cron + immediate run
+  console.log("Firebase → Mongo sync running (every 15 minutes)");
+
+  // Run immediately
+  try {
+    await syncPlayers();
+  } catch (e) {
+    console.error("Players sync error:", e);
+  }
+
+  // Schedule every 15 minutes
+  cron.schedule("*/15 * * * *", async () => {
+    try {
+      await syncPlayers();
+    } catch (e) {
+      console.error("Players sync error:", e);
+    }
+  });
+}
+
+main();
+

src/mongo.ts

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+import { MongoClient, Db } from "mongodb";
+
+const uri = process.env.MONGO_URI!;
+const client = new MongoClient(uri);
+let db: Db | null = null;
+
+export async function connectMongo(): Promise<Db> {
+  if (db) return db;
+
+  await client.connect();
+  db = client.db(); // database name is taken from URI
+  return db;
+}
+

src/sync.ts

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+import { rtdb } from "./firebase";
+import { connectMongo } from "./mongo";
+import { Document } from "mongodb";
+
+type PlayerDoc = Document & { _id: number };
+
+export async function syncPlayers() {
+  console.log("Players sync started:", new Date().toISOString());
+
+  const db = await connectMongo();
+  const collection = db.collection<PlayerDoc>("players");
+
+  // 🔹 RTDB path
+  const snapshot = await rtdb.ref("players").once("value");
+
+  const playersDict = snapshot.val();
+
+  if (!playersDict) {
+    console.log("No players data found");
+    return;
+  }
+
+  const bulkOps = Object.entries(playersDict).map(([id, data]) => ({
+    replaceOne: {
+      filter: { _id: Number(id) },
+      replacement: {
+        _id: Number(id),
+        ...(data as object)
+      },
+      upsert: true
+    }
+  }));
+
+  await collection.bulkWrite(bulkOps, { ordered: false });
+
+  console.log("Players synced:", bulkOps.length);
+}
+

src/syncReverse.ts

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+import { rtdb } from "./firebase";
+import { connectMongo } from "./mongo";
+
+export async function syncMongoToFirebase() {
+  console.log("Mongo → Firebase sync started:", new Date().toISOString());
+
+  const db = await connectMongo();
+  const collection = db.collection("players");
+
+  const allPlayers = await collection.find().toArray();
+
+  // Convert to dictionary: { numericId: {...playerFields} }
+  const playersDict: Record<string, any> = {};
+  for (const player of allPlayers) {
+    const { _id, ...fields } = player;
+    playersDict[_id.toString()] = fields;
+  }
+
+  // Push to Firebase Realtime Database
+  await rtdb.ref("players").set(playersDict);
+
+  console.log("Mongo → Firebase sync finished:", allPlayers.length, "players");
+}
+

tsconfig.json

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+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "module": "CommonJS",
+    "rootDir": "./src",
+    "outDir": "./dist",
+    "strict": true,
+    "esModuleInterop": true,
+
+    "resolveJsonModule": true,
+    "moduleResolution": "node"
+  }
+}
+