# Subscriber Status System

## Overview

The newsletter system tracks subscribers with a `status` field that determines whether they receive newsletters.

## Status Field

### Database Schema

```javascript
{
  _id: ObjectId("..."),
  email: "user@example.com",
  subscribed_at: ISODate("2025-11-11T15:50:29.478Z"),
  status: "active"  // or "inactive"
}
```

### Status Values

| Status | Description | Receives Newsletters |
|--------|-------------|---------------------|
| `active` | Subscribed and active | ✅ Yes |
| `inactive` | Unsubscribed | ❌ No |

## How It Works

### Subscription Flow

```
User subscribes
    ↓
POST /api/subscribe
    ↓
Create subscriber with status: 'active'
    ↓
User receives newsletters
```

### Unsubscription Flow

```
User unsubscribes
    ↓
POST /api/unsubscribe
    ↓
Update subscriber status: 'inactive'
    ↓
User stops receiving newsletters
```

### Re-subscription Flow

```
Previously unsubscribed user subscribes again
    ↓
POST /api/subscribe
    ↓
Update status: 'active' + new subscribed_at date
    ↓
User receives newsletters again
```

## API Endpoints

### Subscribe

```bash
curl -X POST http://localhost:5001/api/subscribe \
  -H "Content-Type: application/json" \
  -d '{"email": "user@example.com"}'
```

**Creates subscriber with:**
- `email`: user@example.com
- `status`: "active"
- `subscribed_at`: current timestamp

### Unsubscribe

```bash
curl -X POST http://localhost:5001/api/unsubscribe \
  -H "Content-Type: application/json" \
  -d '{"email": "user@example.com"}'
```

**Updates subscriber:**
- `status`: "inactive"

## Newsletter Sending

### Who Receives Newsletters

Only subscribers with `status: 'active'` receive newsletters.

**Sender Service Query:**
```python
subscribers_collection.find({'status': 'active'})
```

**Admin API Query:**
```python
subscribers_collection.count_documents({'status': 'active'})
```

### Testing

```bash
# Check active subscriber count
curl http://localhost:5001/api/admin/stats | jq '.subscribers'

# Output:
# {
#   "total": 10,
#   "active": 8
# }
```

## Database Operations

### Add Active Subscriber

```javascript
db.subscribers.insertOne({
  email: "user@example.com",
  subscribed_at: new Date(),
  status: "active"
})
```

### Deactivate Subscriber

```javascript
db.subscribers.updateOne(
  { email: "user@example.com" },
  { $set: { status: "inactive" } }
)
```

### Reactivate Subscriber

```javascript
db.subscribers.updateOne(
  { email: "user@example.com" },
  { $set: { 
    status: "active",
    subscribed_at: new Date()
  }}
)
```

### Query Active Subscribers

```javascript
db.subscribers.find({ status: "active" })
```

### Count Active Subscribers

```javascript
db.subscribers.countDocuments({ status: "active" })
```

## Common Issues

### Issue: Stats show 0 active subscribers but subscribers exist

**Cause:** Old bug where stats checked `{active: true}` instead of `{status: 'active'}`

**Solution:** Fixed in latest version. Stats now correctly query `{status: 'active'}`

**Verify:**
```bash
# Check database directly
docker-compose exec mongodb mongosh munich_news -u admin -p changeme \
  --authenticationDatabase admin \
  --eval "db.subscribers.find({status: 'active'}).count()"

# Check via API
curl http://localhost:5001/api/admin/stats | jq '.subscribers.active'
```

### Issue: Newsletter not sending to subscribers

**Possible causes:**
1. Subscribers have `status: 'inactive'`
2. No subscribers in database
3. Email configuration issue

**Debug:**
```bash
# Check subscriber status
docker-compose exec mongodb mongosh munich_news -u admin -p changeme \
  --authenticationDatabase admin \
  --eval "db.subscribers.find().pretty()"

# Check active count
curl http://localhost:5001/api/admin/stats | jq '.subscribers'

# Try sending
curl -X POST http://localhost:5001/api/admin/send-newsletter \
  -H "Content-Type: application/json"
```

## Migration Notes

### If you have old subscribers without status field

Run this migration:

```javascript
// Set all subscribers without status to 'active'
db.subscribers.updateMany(
  { status: { $exists: false } },
  { $set: { status: "active" } }
)
```

### If you have subscribers with `active: true/false` field

Run this migration:

```javascript
// Convert old 'active' field to 'status' field
db.subscribers.updateMany(
  { active: true },
  { $set: { status: "active" }, $unset: { active: "" } }
)

db.subscribers.updateMany(
  { active: false },
  { $set: { status: "inactive" }, $unset: { active: "" } }
)
```

## Best Practices

### 1. Always Check Status

When querying subscribers for sending:
```python
# ✅ Correct
subscribers_collection.find({'status': 'active'})

# ❌ Wrong
subscribers_collection.find({})  # Includes inactive
```

### 2. Soft Delete

Never delete subscribers - just set status to 'inactive':
```python
# ✅ Correct - preserves history
subscribers_collection.update_one(
    {'email': email},
    {'$set': {'status': 'inactive'}}
)

# ❌ Wrong - loses data
subscribers_collection.delete_one({'email': email})
```

### 3. Track Subscription History

Consider adding fields:
```javascript
{
  email: "user@example.com",
  status: "active",
  subscribed_at: ISODate("2025-01-01"),
  unsubscribed_at: null,  // Set when status changes to inactive
  resubscribed_count: 0   // Increment on re-subscription
}
```

### 4. Validate Before Sending

```python
# Check subscriber count before sending
count = subscribers_collection.count_documents({'status': 'active'})
if count == 0:
    return {'error': 'No active subscribers'}
```

## Related Documentation

- [ADMIN_API.md](ADMIN_API.md) - Admin API endpoints
- [DATABASE_SCHEMA.md](DATABASE_SCHEMA.md) - Complete database schema
- [NEWSLETTER_API_UPDATE.md](../NEWSLETTER_API_UPDATE.md) - Newsletter API changes