# Multi-Device Push Notifications Implementation

## Overview

Updated the push notification system to support multiple devices per user. Users can now receive push notifications on all their logged-in devices (mobile, tablet, desktop, etc.).

## Database Changes

### Migration: `update_push_tokens_to_array.sql`

- Converted single `push_token` field to `push_tokens` JSON array
- Automatically migrates existing single tokens to array format
- Adds optimized GIN index for JSON array queries

## API Endpoints

### 1. Add Push Token (New Device Login)

```http
POST /users/push-token
Authorization: Bearer <jwt_token>
Content-Type: application/json

{
  "pushToken": "device_push_token_from_najva_sdk",
  "deviceId": "optional_device_identifier"
}
```

### 2. Remove Push Token (Device Logout)

```http
DELETE /users/push-token
Authorization: Bearer <jwt_token>
Content-Type: application/json

{
  "pushToken": "device_push_token_to_remove"
}
```

### 3. Get All Push Tokens

```http
GET /users/push-tokens
Authorization: Bearer <jwt_token>
```

Response:

```json
{
  "pushTokens": ["token1", "token2", "token3"],
  "totalTokens": 3
}
```

### 4. Update Profile (Push Token Removed)

```http
PATCH /users/profile
Authorization: Bearer <jwt_token>
Content-Type: application/json

{
  "profilePic": "https://example.com/profile.jpg"
}
```

## Features

### ✅ Multi-Device Support

- Users can have multiple push tokens (one per device)
- Notifications sent to all registered devices simultaneously
- Automatic deduplication prevents duplicate tokens

### ✅ Invalid Token Cleanup

- Automatically detects invalid/expired tokens from Najva API response
- Removes invalid tokens from user's token list
- Logs cleanup activities for monitoring

### ✅ Device Management

- Add tokens when user logs in on new device
- Remove tokens when user logs out from device
- View all registered devices/tokens

### ✅ Backward Compatibility

- Existing single token data automatically migrated to array format
- No breaking changes to existing notification flow

## Implementation Details

### User Entity Changes

```typescript
// Before
@Property({ type: "varchar", nullable: true })
pushToken?: string;

// After
@Property({ type: "json", nullable: true })
pushTokens?: string[];
```

### Service Methods

```typescript
// Add token for new device
await usersService.addPushToken(userId, { pushToken: "token" });

// Remove token when logging out
await usersService.removePushToken(userId, { pushToken: "token" });

// Send to all user devices
await notificationsService.sendPushNotificationToUserDevices(userId, userTokens, message);
```

### Automatic Token Cleanup

When sending notifications, invalid tokens are automatically:

1. Detected from Najva API response
2. Logged for monitoring
3. Removed from user's token array
4. Database updated to clean state

## Frontend Integration

### When User Logs In

```javascript
// Get push token from Najva SDK
const pushToken = await najva.getPushToken();

// Register token for this device
await fetch("/api/users/push-token", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${jwt}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    pushToken: pushToken,
    deviceId: navigator.userAgent, // optional
  }),
});
```

### When User Logs Out

```javascript
// Remove token for this device
await fetch("/api/users/push-token", {
  method: "DELETE",
  headers: {
    Authorization: `Bearer ${jwt}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    pushToken: currentDeviceToken,
  }),
});
```

## Environment Variables

```env
NAJVA_API_KEY=your_najva_api_key
NAJVA_WEBSITE_ID=your_website_id
NAJVA_API_URL=https://push.najva.com/v1/send/token/
PUSH_TTL=24
FRONTEND_URL=https://your-frontend-domain.com
```

## Benefits

1. **Multi-Device Support**: Users get notifications on all their devices
2. **Device Management**: Add/remove devices as needed
3. **Automatic Cleanup**: Invalid tokens automatically removed
4. **Scalable**: Efficient JSON array storage with GIN indexing
5. **Reliable**: Handles edge cases like duplicate tokens and API failures
6. **Monitoring**: Comprehensive logging for debugging and monitoring

## Migration Steps

1. **Run Database Migration**:

   ```sql
   -- Execute: database/migrations/update_push_tokens_to_array.sql
   ```

2. **Update Frontend**:
   - Use new `/users/push-token` endpoints
   - Remove `pushToken` field from profile updates

3. **Deploy Backend**:
   - All changes are backward compatible
   - Existing tokens automatically migrated

## Testing

Test the multi-device functionality:

1. Login from Device A → Add token A
2. Login from Device B → Add token B
3. Create notification → Both devices receive push
4. Logout from Device A → Remove token A
5. Create notification → Only device B receives push

The system now properly supports users accessing your application from multiple devices while maintaining reliable push notification delivery!