Notification Automation (Email + SMS + Telegram) via Triggers

Setting Up Notification Automation (Email + SMS + Telegram) via Triggers

An automated notification system sends messages to users on trigger events through multiple channels. A unified notification service receives events from the application and distributes them across channels based on user preferences.

Notification Service Architecture

// notification.service.ts
interface NotificationRequest {
  userId: string;
  type: NotificationType;
  data: Record<string, unknown>;
  channels?: Channel[];  // if not specified — by user settings
  priority?: 'high' | 'normal' | 'low';
}

type NotificationType =
  | 'order.placed'
  | 'order.shipped'
  | 'payment.failed'
  | 'password.reset'
  | 'promo.discount';

class NotificationService {
  async send(request: NotificationRequest): Promise<void> {
    const prefs = await this.userPrefsRepo.findByUserId(request.userId);
    const channels = request.channels ?? this.resolveChannels(request.type, prefs);

    await Promise.allSettled(
      channels.map(channel => this.sendViaChannel(channel, request, prefs))
    );
  }

  private resolveChannels(type: NotificationType, prefs: UserPrefs): Channel[] {
    const channelMap: Record<NotificationType, Channel[]> = {
      'order.placed': ['email', 'telegram'],
      'order.shipped': ['email', 'sms', 'telegram'],
      'payment.failed': ['email', 'sms'],      // critical — all channels
      'password.reset': ['email'],              // email only
      'promo.discount': prefs.marketingChannels // user choice
    };
    return channelMap[type] ?? ['email'];
  }
}

Email via Resend

import { Resend } from 'resend';
const resend = new Resend(process.env.RESEND_API_KEY);

async function sendEmailNotification(
  user: User,
  type: NotificationType,
  data: Record<string, unknown>
) {
  const template = emailTemplates[type];

  await resend.emails.send({
    from: '[email protected]',
    to: user.email,
    subject: template.subject(data),
    react: template.component({ user, ...data })
  });
}

// Template for order.shipped
const orderShippedTemplate = {
  subject: (data) => `Your order #${data.orderId} has been shipped`,
  component: ({ user, orderId, trackingNumber, estimatedDelivery }) => (
    <OrderShippedEmail
      name={user.firstName}
      orderId={orderId}
      trackingNumber={trackingNumber}
      trackingUrl={`https://example.com/track/${trackingNumber}`}
      estimatedDelivery={estimatedDelivery}
    />
  )
};

SMS via Twilio

import twilio from 'twilio';
const client = twilio(process.env.TWILIO_SID, process.env.TWILIO_TOKEN);

async function sendSmsNotification(
  user: User,
  type: NotificationType,
  data: Record<string, unknown>
) {
  if (!user.phone || !user.phoneVerified) return;

  const templates: Record<NotificationType, (data: Record<string, unknown>) => string> = {
    'order.shipped': (d) =>
      `Order #${d.orderId} shipped. Track: ${d.trackingNumber}. Expect by ${d.date}`,
    'payment.failed': (d) =>
      `Payment for order #${d.orderId} failed. Update card: ${d.retryUrl}`
  };

  const text = templates[type]?.(data);
  if (!text) return;

  await client.messages.create({
    to: user.phone,
    from: process.env.TWILIO_PHONE,
    body: text
  });
}

Telegram via Bot API

import TelegramBot from 'node-telegram-bot-api';
const bot = new TelegramBot(process.env.TELEGRAM_BOT_TOKEN);

async function sendTelegramNotification(
  user: User,
  type: NotificationType,
  data: Record<string, unknown>
) {
  if (!user.telegramChatId) return;

  const messages: Record<string, (d: Record<string, unknown>) => string> = {
    'order.shipped':
      (d) => `📦 *Order #${d.orderId} shipped*\n\nTracking: \`${d.trackingNumber}\`\nExpected: ${d.date}`,
    'payment.failed':
      (d) => `⚠️ *Payment Error*\n\nOrder #${d.orderId} not paid. [Retry](${d.retryUrl})`
  };

  const text = messages[type]?.(data);
  if (!text) return;

  await bot.sendMessage(user.telegramChatId, text, {
    parse_mode: 'Markdown',
    disable_web_page_preview: true
  });
}

// Telegram account binding by user
bot.onText(/\/start (.+)/, async (msg, match) => {
  const linkToken = match[1];
  const userId = await verifyLinkToken(linkToken);

  if (userId) {
    await userRepo.updateTelegramChatId(userId, msg.chat.id.toString());
    bot.sendMessage(msg.chat.id, '✅ Telegram connected! You will receive notifications.');
  }
});

Preference Management

// Table user_notification_prefs
interface UserNotificationPrefs {
  userId: string;
  emailEnabled: boolean;
  smsEnabled: boolean;
  telegramEnabled: boolean;
  marketingEmailEnabled: boolean;
  marketingSmsEnabled: boolean;
  quietHoursStart: string;  // '22:00'
  quietHoursEnd: string;    // '08:00'
  timezone: string;         // 'Europe/Moscow'
}

Retry and Queue

// Notifications via Bull Queue with retry
const notificationQueue = new Bull('notifications', { redis: redisConfig });

notificationQueue.process(async (job) => {
  const { userId, type, data } = job.data;
  await notificationService.send({ userId, type, data });
});

// Add with delay for non-urgent
await notificationQueue.add(
  { userId, type: 'promo.discount', data },
  {
    delay: 5 * 60 * 1000,  // 5 minute delay
    attempts: 3,
    backoff: { type: 'exponential', delay: 2000 }
  }
);

Timeline

Email + SMS + Telegram with preference management and queue — 1–2 weeks.