How to Set Up Automated Email Campaigns Triggered by User Actions in FlutterFlow

1// functions/src/emailTriggers.ts
2import * as functions from 'firebase-functions';
3import * as admin from 'firebase-admin';
4
5const db = admin.firestore();
6
7export const sendWelcomeEmail = functions.firestore
8  .document('users/{userId}')
9  .onCreate(async (snap, context) => {
10    const userId = context.params.userId;
11    const user = snap.data();
12    const logId = `${userId}_welcome`;
13
14    // Idempotency check
15    const logRef = db.collection('email_log').doc(logId);
16    const existing = await logRef.get();
17    if (existing.exists) return;
18
19    // Reserve the log entry before sending
20    await logRef.set({
21      user_id: userId,
22      email_type: 'welcome',
23      recipient_email: user.email,
24      sent_at: admin.firestore.FieldValue.serverTimestamp(),
25      status: 'pending',
26    });
27
28    try {
29      await sendEmail({
30        to: user.email,
31        subject: `Welcome to the app, ${user.display_name}!`,
32        html: buildWelcomeHtml(user.display_name),
33      });
34      await logRef.update({ status: 'sent' });
35    } catch (err) {
36      await logRef.update({ status: 'failed', error: String(err) });
37      throw err; // Re-throw so Firebase retries the function
38    }
39  });
40
41async function sendEmail(opts: { to: string; subject: string; html: string }) {
42  const res = await fetch('https://api.resend.com/emails', {
43    method: 'POST',
44    headers: {
45      Authorization: `Bearer ${functions.config().resend.key}`,
46      'Content-Type': 'application/json',
47    },
48    body: JSON.stringify({
49      from: 'hello@yourapp.com',
50      to: opts.to,
51      subject: opts.subject,
52      html: opts.html,
53    }),
54  });
55  if (!res.ok) throw new Error(`Email API error: ${res.status}`);
56}
57
58function buildWelcomeHtml(name: string): string {
59  return `<h1>Welcome, ${name}!</h1><p>Get started by completing your profile.</p>`;
60}

1export const sendDripEmails = functions.pubsub
2  .schedule('0 10 * * *')
3  .timeZone('America/New_York')
4  .onRun(async () => {
5    const drips = [
6      { daysAfterSignup: 3, emailType: 'day3_tips', subject: '3 tips for getting started' },
7      { daysAfterSignup: 7, emailType: 'day7_check', subject: 'How is it going?' },
8      { daysAfterSignup: 14, emailType: 'day14_feature', subject: 'Have you tried this feature?' },
9    ];
10
11    for (const drip of drips) {
12      const cutoffStart = new Date();
13      cutoffStart.setDate(cutoffStart.getDate() - drip.daysAfterSignup - 1);
14      const cutoffEnd = new Date();
15      cutoffEnd.setDate(cutoffEnd.getDate() - drip.daysAfterSignup);
16
17      const usersSnap = await db.collection('users')
18        .where('created_at', '>=', admin.firestore.Timestamp.fromDate(cutoffStart))
19        .where('created_at', '<', admin.firestore.Timestamp.fromDate(cutoffEnd))
20        .where('email_opted_in', '==', true)
21        .get();
22
23      for (const userDoc of usersSnap.docs) {
24        const user = userDoc.data();
25        const logId = `${userDoc.id}_${drip.emailType}`;
26        const logRef = db.collection('email_log').doc(logId);
27        const existing = await logRef.get();
28        if (existing.exists) continue;
29
30        await logRef.set({ status: 'pending', sent_at: admin.firestore.FieldValue.serverTimestamp() });
31        try {
32          await sendEmail({ to: user.email, subject: drip.subject, html: `<p>Hi ${user.display_name}</p>` });
33          await logRef.update({ status: 'sent' });
34        } catch (e) {
35          await logRef.update({ status: 'failed' });
36        }
37      }
38    }
39  });