server.js

import express from "express";
import bodyParser from "body-parser";
import admin from "firebase-admin";
import fs from "fs";

// Load Firebase service account key
const serviceAccount = JSON.parse(
  fs.readFileSync("./serviceAccountKey.json", "utf-8")
);

admin.initializeApp({
  credential: admin.credential.cert(serviceAccount),
});

const app = express();
app.use(bodyParser.json());

// Send notification to multiple tokens
app.post("/send", async (req, res) => {
  try {
    const { tokens, title, body, data } = req.body;

    if (!tokens || tokens.length === 0) {
      return res.status(400).json({ error: "No tokens provided" });
    }

    const message = {
      notification: { title, body },
      data: data || {}, // custom key-value data
      tokens,
    };

    const response = await admin.messaging().sendEachForMulticast(message);
    res.json({ success: true, response });
  } catch (error) {
    console.error("Error sending notification:", error);
    res.status(500).json({ error: error.message });
  }
});

app.listen(3000, () => {
  console.log("🚀 FCM Server running on http://localhost:3000");
});