[Backend] Implement Automated Prescription Refill Reminder Scheduler

[llinsss]

⚠️ This is a backend issue — work is done inside the backend/ folder

Description

PrescriptionsService has a getRefillReminders() method that calculates which prescriptions are due for refill, and a RefillReminder interface is defined. However, this method is never called automatically — reminders are only returned if the frontend explicitly polls the endpoint. Pet owners miss refill windows because no proactive notification is sent.

Current State

• backend/src/modules/prescriptions/prescriptions.service.ts — getRefillReminders() exists
• RefillReminder interface is defined with daysUntilRefill and estimatedRefillDate
• No cron job or BullMQ scheduler calls getRefillReminders()
• NotificationsService is not injected into PrescriptionsService

What Needs to Be Built

1. Inject NotificationsService into PrescriptionsService

• Add NotificationsService to PrescriptionsModule imports and constructor

2. Refill Reminder Scheduler (prescriptions/prescription-reminder.scheduler.ts)

@Injectable()
export class PrescriptionReminderScheduler {
  @Cron('0 9 * * *') // Daily at 9am
  async sendRefillReminders() {
    const reminders = await this.prescriptionsService.getRefillReminders();
    for (const reminder of reminders) {
      if (reminder.daysUntilRefill <= 3) {
        await this.notificationsService.create({ ... });
      }
    }
  }
}

3. Notification Content

• Title: Refill Reminder: {medication}
• Body: {petName}'s {medication} needs a refill in {daysUntilRefill} days (est. {estimatedRefillDate})
• Category: MEDICATION
• Deep link to prescription detail page

4. Deduplication

• Track sent reminders in Redis with key refill_reminder:{prescriptionId}:{date} TTL 24h
• Skip if reminder already sent today for this prescription

Acceptance Criteria

• Reminders are sent daily at 9am for prescriptions due within 3 days
• Each reminder is sent at most once per day per prescription (deduplication)
• Notification includes medication name, pet name, and estimated refill date
• Scheduler is registered in PrescriptionsModule
• Unit tests cover scheduling logic and deduplication

Files to Create / Modify

• backend/src/modules/prescriptions/prescription-reminder.scheduler.ts (new)
• backend/src/modules/prescriptions/prescriptions.module.ts (register scheduler)
• backend/src/modules/prescriptions/prescriptions.service.ts (inject NotificationsService)
• backend/src/modules/prescriptions/prescription-reminder.scheduler.spec.ts (new)

Priority

High — refill reminders are calculated but never delivered

Estimated Effort

1–2 days

[Opeyemi01-del]

@Opeyemi01-del has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Kindly assign this issue boss

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Opeyemi01-del to this issue.

[ndii-dev]

@ndii-dev has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

I would like to work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @ndii-dev to this issue.

[drips-wave]

Congratulations, @ndii-dev! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

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