# Service Integrations — EventBus Architecture

Tracking document for the platform-wide EventBus and service integration work.

**Started:** 2026-03-30
**Branch:** v2

---

## Architecture Overview

Changemaker Lite has 30+ services but most operate as isolated tools. The EventBus provides a centralized, typed, in-process pub/sub system that decouples event producers from consumers.

```
Service Handler (shift created, donation completed, etc.)
        |
        v
  eventBus.publish('shift.created', payload)
        |
        +-- ListmonkListener      (newsletter sync)
        +-- RocketChatListener    (team notifications)
        +-- CrmActivityListener   (contact timeline)
        +-- CalendarSyncListener  (unified calendar)
        +-- N8nWebhookListener    (external automation)
        +-- GancioSyncListener    (public event calendar)
```

### Why In-Process EventEmitter (not Redis PubSub)

- Single Express process — no distributed coordination needed
- Zero serialization overhead (pass JS objects directly)
- Data already persisted in DB — events are ephemeral notifications
- Matches the existing fire-and-forget pattern used by Listmonk/RC services
- Can be swapped to Redis PubSub later if we go multi-process

### Key Files

| File | Purpose |
|------|---------|
| `api/src/types/events.ts` | Typed event catalog (all event names + payloads) |
| `api/src/services/event-bus.service.ts` | Core EventBus (publish/subscribe/stats) |
| `api/src/services/event-listeners/listmonk.listener.ts` | Listmonk newsletter sync |
| `api/src/services/event-listeners/rocketchat.listener.ts` | Rocket.Chat notifications |
| `api/src/services/event-listeners/crm-activity.listener.ts` | CRM ContactActivity writer |
| `api/src/services/event-listeners/calendar-sync.listener.ts` | Calendar unification |
| `api/src/services/event-listeners/n8n-webhook.listener.ts` | n8n automation bridge |
| `api/src/services/event-listeners/gancio.listener.ts` | Gancio event sync (shifts + ticketed events) |
| `api/src/services/event-listeners/engagement-scoring.listener.ts` | Contact engagement scores (Redis ZSET) |
| `api/src/services/event-listeners/homepage-stats.listener.ts` | Homepage real-time counters + cache invalidation |

---

## Progress Tracker

### Phase 1: Core Infrastructure
- [x] Explore existing event patterns (Listmonk, RC, Gancio, provisioning)
- [x] Design EventBus architecture
- [x] Implement EventBus service (`api/src/services/event-bus.service.ts`)
- [x] Define typed event catalog (`api/src/types/events.ts` — 46 events across 14 modules)
- [x] Register EventBus in server.ts startup
- [x] Add EventBus stats endpoint (`GET /api/observability/event-bus`)

### Phase 2: Migrate Existing Integrations
- [x] Listmonk event sync → EventBus listener (9 event subscriptions)
- [x] Rocket.Chat webhook service → EventBus listener (4 event subscriptions)
- [x] Gancio shift/event sync → EventBus listener (3 event subscriptions)

### Phase 3: New Listeners
- [x] CRM Activity auto-generation listener (11 event subscriptions)
- [x] Calendar sync listener (8 event subscriptions)
- [x] n8n webhook emitter listener (wildcard subscription, forwards all events)
- [x] Listmonk webhook receiver (inbound: open, click, bounce, unsubscribe → EventBus)

### Phase 4: Wire Up Publishers (migrated from inline calls)
- [x] Shift CRUD + signup (shift.created/updated/deleted, shift.signup.created/cancelled)
- [x] Canvass session complete + visits (canvass.session.completed, contact.address.updated)
- [x] Response submit (response.submitted)
- [x] Campaign email sent (campaign.email.sent)
- [x] Payment/donation/subscription events (3 event types)
- [x] Contact tag changes (contact.tags.changed — 3 call sites)
- [x] Reengagement sent (reengagement.sent)
- [x] Campaign CRUD + publish + moderation (campaign.created/updated/deleted/published/status.changed)
- [x] User create/update/delete/approve (user.created/updated/deleted/approved)
- [x] SMS campaign start/complete + message send/receive (4 event types)
- [x] Media video publish/unpublish/view (3 event types)
- [x] Ticketed event publish/cancel (EventBus publishes alongside existing Gancio calls)
- [x] Impact story publish (social.impact-story.published)
- [x] Meeting create/delete (jitsi.routes.ts — meeting.created, meeting.deleted)

### Phase 4b: Extended Listeners (2026-03-31)
- [x] RC listener: +7 subscriptions (campaign.published, donations, subscriptions, SMS escalation, user.approved, video.published, ticketed-event.published)
- [x] CRM listener: +2 subscriptions (subscription activated, email bounced)
- [x] RC webhook service: +7 new formatter methods
- [x] Prisma migration: SHIFT, MEETING, TICKETED_EVENT added to CalendarItemSource enum
- [x] Calendar sync listener: uses proper source types (SHIFT, MEETING, TICKETED_EVENT)

### Phase 4c: New Data Listeners (2026-03-31)
- [x] Engagement scoring listener (11 subscriptions, Redis ZSET leaderboard)
- [x] Homepage stats listener (12 subscriptions, Redis counters + recent activity)
- [x] GET /api/homepage/live-stats endpoint (public, real-time counters + recent)
- [x] GET /api/observability/engagement-leaderboard endpoint (admin, top contacts)

### Phase 5: Future
- [ ] Migrate meeting-planner Gancio calls to EventBus (blocked: synchronous return value needed)
- [ ] Homepage service: swap COUNT queries for Redis counters in getStats()
- [ ] Engagement score materialization: periodic job to denormalize scores to Contact model

---

## Event Catalog

### Currently Wired (11 event points, 3 consumers)

| Event | Listmonk | Rocket.Chat | Gancio |
|-------|----------|-------------|--------|
| shift.signup | yes | yes | - |
| shift.signup.cancelled | - | yes | - |
| shift.created | - | - | yes |
| shift.updated | - | - | yes |
| shift.deleted | - | - | yes |
| canvass.session.completed | yes | yes | - |
| canvass.address.updated | yes | - | - |
| campaign.email.sent | yes | - | - |
| response.submitted | - | yes | - |
| subscription.activated | yes | - | - |
| donation.completed | yes | - | - |
| product.purchased | yes | - | - |
| contact.tags.changed | yes | - | - |
| reengagement.sent | yes | - | - |

### New Events (49+ handlers need publishers)

| Event | CRM Activity | Calendar | RC | n8n |
|-------|-------------|----------|-----|-----|
| campaign.created | - | - | - | yes |
| campaign.published | - | - | yes | yes |
| campaign.status.changed | - | - | yes | yes |
| user.approved | - | - | yes | yes |
| user.created | - | - | - | yes |
| video.published | - | - | yes | yes |
| video.viewed | yes | - | - | - |
| sms.message.received | yes | - | yes* | yes |
| sms.campaign.completed | - | - | yes | yes |
| ticketed-event.published | - | yes | - | yes |
| meeting.created | - | yes | - | - |
| impact-story.published | - | - | yes | yes |
| shift.created | - | yes | - | yes |
| donation.completed | yes | - | yes | yes |
| subscription.activated | yes | - | - | yes |

*SMS escalations (QUESTION/NEGATIVE sentiment) to relevant RC channel

---

## Design Decisions

1. **Listeners self-guard**: Each listener checks its own feature flag (ENABLE_CHAT, LISTMONK_SYNC_ENABLED, etc.) — the EventBus doesn't filter
2. **Error isolation**: Each listener wraps its handler in try-catch; one listener failing doesn't affect others
3. **No persistence**: Events are ephemeral — if the server restarts mid-event, it's lost (data is already in DB)
4. **Stats tracking**: EventBus tracks per-event emission counts + per-listener execution counts for observability
5. **Wildcard subscriptions**: Listeners can subscribe to `shift.*` to catch all shift events