How you can use Firebase Cloud Functions to add server-side logic to a mobile application

How you can use Firebase Cloud Functions to add server-side logic to a mobile application

1. User Authentication Triggers

Cloud Functions can be used to execute code in response to user authentication events, such as user creation or deletion.

Example: Send a Welcome Email on User Signup

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

exports.sendWelcomeEmail = functions.auth.user().onCreate((user) => {
    const email = user.email; // The email of the user.
    const displayName = user.displayName; // The display name of the user.

    // Implement your email sending logic here.
    console.log(`Sending welcome email to ${email}`);
});

2. Database Triggers

Cloud Functions can respond to changes in the Firebase Realtime Database or Firestore.

Example: Update User Count on New User Addition

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

exports.updateUserCount = functions.firestore
    .document('users/{userId}')
    .onCreate((snap, context) => {
        const newValue = snap.data();
        const countRef = admin.firestore().collection('metrics').doc('userCount');
        return countRef.update({
            count: admin.firestore.FieldValue.increment(1)
        });
    });

3. HTTP Triggers

Cloud Functions can be exposed as HTTP endpoints that can be called directly from your mobile app.

Example: Create a Cloud Function to Handle HTTP Requests

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

exports.addMessage = functions.https.onRequest((req, res) => {
    const original = req.query.text;
    admin.firestore().collection('messages').add({original: original}).then((writeResult) => {
        res.json({result: `Message with ID: ${writeResult.id} added.`});
    });
});

4. Scheduled Functions

You can schedule Cloud Functions to run at specific intervals, similar to a cron job.

Example: Clean Up Old Data Periodically

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

exports.scheduledFunction = functions.pubsub.schedule('every 24 hours').onRun((context) => {
    const now = admin.firestore.Timestamp.now();
    const cutoff = new Date(now.toDate());
    cutoff.setDate(cutoff.getDate() - 30); // 30 days ago
    const cutoffTimestamp = admin.firestore.Timestamp.fromDate(cutoff);

    const oldItemsQuery = admin.firestore().collection('items').where('createdAt', '<', cutoffTimestamp);

    return oldItemsQuery.get().then((snapshot) => {
        const batch = admin.firestore().batch();
        snapshot.forEach((doc) => {
            batch.delete(doc.ref);
        });
        return batch.commit();
    });
});

5. Image Processing

You can use Cloud Functions to handle image uploads and perform processing tasks like resizing or generating thumbnails.

Example: Generate Thumbnails for Uploaded Images

const functions = require('firebase-functions');
const admin = require('firebase-admin');
const {Storage} = require('@google-cloud/storage');
const sharp = require('sharp');

admin.initializeApp();
const gcs = new Storage();

exports.generateThumbnail = functions.storage.object().onFinalize(async (object) => {
    const bucket = gcs.bucket(object.bucket);
    const filePath = object.name;
    const fileName = filePath.split('/').pop();
    const tempFilePath = `/tmp/${fileName}`;
    const tempThumbnailPath = `/tmp/thumb_${fileName}`;

    // Download the file from bucket.
    await bucket.file(filePath).download({destination: tempFilePath});

    // Generate a thumbnail using Sharp.
    await sharp(tempFilePath).resize({width: 200}).toFile(tempThumbnailPath);

    // Upload the thumbnail back to the bucket.
    await bucket.upload(tempThumbnailPath, {
        destination: `thumbnails/thumb_${fileName}`
    });
});

These examples illustrate how you can leverage Firebase Cloud Functions to add powerful backend capabilities to your mobile applications without having to manage your own servers.