# Broadcasting: Faye → ActionCable Migration Guide

## Current state

```
Model (SimplyStored::Couch)
  → ApplicationController.new.broadcast_user   # ⚠️ anti-pattern
    → Mozo.broadcast_user
      → Mozo::Broadcaster::Faye.new.broadcast  # HTTP POST to Faye
        → Faye server (Thin, port 9296)
          → WebSocket → browser clients
```

## Target state

```
Model (Broadcastable concern)
  → Mozo.broadcast_user
    → Mozo::Broadcaster::ActionCable.new.broadcast  # in-process async
      → ActionCable (Rails built-in)
        → WebSocket → browser clients
```

## What this branch adds

| File | Purpose |
|------|---------|
| `lib/mozo/broadcaster/action_cable.rb` | Drop-in ActionCable broadcaster adapter |
| `config/cable.yml` | ActionCable configuration (async for single-server) |
| `app/channels/application_cable/connection.rb` | WebSocket auth via auth_token |
| `app/channels/mozo_channel.rb` | Channel authorization for user/supplier/employee |
| `app/models/concerns/broadcastable.rb` | Clean module for models (replaces old monkey-patch) |
| `config/routes.rb` | Mounts `/cable` WebSocket endpoint |
| `config/initializers/model_broadcast.rb` | Fixed: delegates to Mozo directly (no more `ApplicationController.new`) |

## How to switch

### 1. Server (one-line change)

In `config/initializers/mozo_settings.rb`, change:

```ruby
# Mozo.broadcaster = Mozo::Broadcaster::Faye.new  # old
Mozo.broadcaster = Mozo::Broadcaster::ActionCable.new  # new
```

### 2. Client (mozo-user / mozo-supplier)

**Old Faye client (conceptual):**
```js
var client = new Faye.Client('https://events.mozo.bar/faye');
client.subscribe('/user/123', function(msg) { ... });
```

**New ActionCable client:**
```js
// Using @rails/actioncable npm package
import { createConsumer } from "@rails/actioncable";

const consumer = createConsumer(
  `wss://mozo.bar/cable?auth_token=${authToken}`
);

consumer.subscriptions.create(
  { channel: "MozoChannel", id: "user_123" },
  {
    received(data) {
      // data = { event: "list_closed", data: { id: 42 } }
      handleEvent(data.event, data.data);
    }
  }
);
```

### 3. Remove Faye

Once stable:
- Remove `gem 'faye'` from Gemfile
- Remove `faye/` directory
- Remove nginx `events.mozo.bar` vhost
- Stop the Faye Thin process

## Benefits

- **No extra process** — ActionCable runs inside Puma
- **Async** — `broadcast` is non-blocking
- **Simpler deploys** — one less service to manage
- **WebSocket native** — no long-polling fallback complexity
- **Rails auth** — cookies/sessions work automatically

---

# Counter: DrbCounter → Redis Migration

## Current state

```
Supplier::Counters (app/models/supplier/counters.rb)
  → Mozo::Counter.incr/decr/get/set
    → Mozo::Counter.connection (Mozo::DrbCounter.object)
      → DRb → druby://localhost:9022
        → InMemoryQCounter (separate Ruby process)
          → on startup: reloads counts from CouchDB
          → in-memory only (lost on restart)
```

## Problems

1. **In-memory only** — restart the DRb process = lose all counts until CouchDB reload
2. **Single-process** — DRb runs one Ruby process, single point of failure
3. **Separate process** — another thing to monitor, deploy, and restart
4. **Race conditions** — between Puma workers, increment/decrement is not atomic across the DRb boundary
5. **Custom code** — `InMemoryQCounter` is 100 lines of hand-rolled counter logic

## Target state

```
Supplier::Counters
  → Mozo::Counter.incr/decr/get/set
    → Mozo::Counter.connection (Mozo::Counter::Redis.new)
      → Redis (localhost:6379)
        → persistent, atomic, multi-process safe
```

## How to switch

In `config/initializers/mozo_settings.rb`, change:

```ruby
# Mozo::Counter.connection = Mozo::DrbCounter.object  # old
Mozo::Counter.connection = Mozo::Counter::Redis.new    # new
```

That's it. All existing `Mozo::Counter.get/set/incr/decr` calls work unchanged.

## What Redis provides

- **Atomic INCR/DECR** — no race conditions
- **Persistence** — RDB snapshots + AOF, survives restarts
- **Multi-process** — all Puma workers share the same Redis
- **Already needed** — ActionCable uses Redis for pub/sub in production
- **Battle-tested** — millions of deployments

## Migration steps

1. `apt-get install redis-server` — already done on vmi3300327
2. `gem 'redis', '~> 5.0'` — added to Gemfile
3. Switch `Mozo::Counter.connection` — one-line change in mozo_settings.rb
4. Stop the DRb counter process (`drb_counter/drb_counter.rb`)