# Braindrops Backend

Self-hosted Bun backend server for the Braindrops drops system.

## Features

- **REST API** - Automatic endpoint loading from drop backends
- **WebSocket** - Real-time bidirectional communication
- **SQLite Database** - Lightweight, file-based storage
- **Auto-Discovery** - Automatically loads drop backends on startup
- **Hot Reload** - Automatically reloads when code changes (dev mode)
- **CORS Support** - Configured for local development and production

## Architecture

```
backend/
├── src/
│   ├── index.js          # Main server entry point
│   ├── db.js             # SQLite database utilities
│   ├── loader.js         # Drop backend auto-discovery
│   ├── router.js         # API routing
│   ├── websocket.js      # WebSocket handling
│   └── shared/
│       └── middleware.js # CORS and other middleware
├── db/
│   └── braindrops.db     # SQLite database (gitignored)
└── package.json
```

## Development

### Starting the Backend

The backend is automatically started when you run:

```bash
npm run dev:drops <drop-name>
```

This starts:
- Drop dev server on port 3000
- CMS on port 8787  
- Backend on port 3001 (only loads the specified drop's backend)

### Standalone Backend

To run the backend independently:

```bash
npm run dev:backend
```

This loads ALL drop backends at once.

## Drop Backend Structure

Each drop can optionally have a `backend/` folder:

```
drops/<drop-name>/
├── src/              # Frontend code
├── backend/          # Backend code (optional)
│   ├── api.js        # REST endpoints
│   ├── schema.sql    # Database schema
│   └── websocket.js  # WebSocket handler (optional)
└── public/
```

### Example API (api.js)

```javascript
import { dbHelpers } from '../../../backend/src/db.js'
const { query, queryOne, run } = dbHelpers

export const routes = {
  'GET /items': async (req) => {
    const items = query('SELECT * FROM mydrop_items')
    return Response.json({ items })
  },
  
  'POST /items': async (req) => {
    const body = await req.json()
    const result = run('INSERT INTO mydrop_items (data) VALUES (?)', [body.data])
    return Response.json({ id: result.lastInsertRowid })
  }
}
```

### Example Schema (schema.sql)

```sql
CREATE TABLE IF NOT EXISTS mydrop_items (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    data TEXT NOT NULL,
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP
);
```

### Example WebSocket (websocket.js)

```javascript
export const websocket = {
  open(ws) {
    ws.send(JSON.stringify({ type: 'connected' }))
  },
  
  message(ws, message) {
    const data = JSON.parse(message)
    // Broadcast to all clients
    ws.publish('mydrop', JSON.stringify(data))
  }
}
```

## API Endpoints

### Health Check
```
GET /health
```

Returns server status and loaded drops.

### Drop APIs
```
/api/<drop-name>/*
```

Each drop's API is namespaced under `/api/<drop-name>/`.

Example:
```bash
# Get melodies from image-melody drop
curl http://localhost:3001/api/image-melody/melodies

# Create a new melody
curl -X POST http://localhost:3001/api/image-melody/melodies \
  -H "Content-Type: application/json" \
  -d '{"name":"My Melody","imageData":{},"melodyData":{}}'
```

### WebSocket
```
ws://<host>:<port>/ws/<drop-name>
```

Example:
```javascript
const ws = new WebSocket('ws://localhost:3001/ws/image-melody')

ws.onmessage = (event) => {
  const data = JSON.parse(event.data)
  console.log('Received:', data)
}

ws.send(JSON.stringify({ type: 'hello' }))
```

## Database

The backend uses SQLite for data storage:
- Database file: `backend/db/braindrops.db`
- Tables use naming convention: `<drop-name>_<table-name>`
- Schemas are auto-applied on startup
- WAL mode enabled for better concurrency

### Database Helpers

Available in drop backends via import:

```javascript
import { dbHelpers } from '../../../backend/src/db.js'
const { query, queryOne, run } = dbHelpers

// Get all rows
const items = query('SELECT * FROM mydrop_items')

// Get single row
const item = queryOne('SELECT * FROM mydrop_items WHERE id = ?', [1])

// Insert/Update/Delete
const result = run('INSERT INTO mydrop_items (data) VALUES (?)', ['test'])
console.log(result.lastInsertRowid) // Get inserted ID
```

## Environment Variables

Create a `.env` file in the root directory:

```bash
# Production URL for CORS
PRODUCTION_URL=https://yourdomain.com

# Optional: Custom port
PORT=3001

# Your API keys
OPENAI_API_KEY=your-key
SOME_SERVICE_KEY=your-key
```

Access in code:
```javascript
const apiKey = process.env.OPENAI_API_KEY
```

## Production Build

Build for production:

```bash
node bin/buildBackend.js
```

This creates `backend/dist/` with:
- All source files
- package.json
- Database directory
- Start script

### Deploying to Production

1. Copy `backend/dist/` to your server
2. Install dependencies: `cd backend/dist && bun install`
3. Set environment variables
4. Start: `./start.sh`

### nginx Configuration

```nginx
# API proxy
location /api/ {
    proxy_pass http://localhost:3001;
}

# WebSocket proxy
location /ws/ {
    proxy_pass http://localhost:3001;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
}
```

## Troubleshooting

### Backend not starting

1. Check if port 3001 is available:
   ```bash
   lsof -i :3001
   ```

2. Check backend logs in the terminal

3. Ensure Bun is installed:
   ```bash
   bun --version
   ```

### Drop backend not loading

1. Check that `drops/<drop-name>/backend/` exists
2. Check that `api.js` has a valid `export const routes = {}`
3. Look for errors in terminal output during startup

### Database errors

1. Check that `backend/db/` directory exists
2. Check file permissions
3. Review schema.sql for syntax errors
4. Delete `braindrops.db` to start fresh (will lose data)

## Development Tips

1. **Route Patterns** - Use Express-style patterns:
   - `GET /items` - List all
   - `GET /items/:id` - Get by ID
   - `POST /items` - Create
   - `PUT /items/:id` - Update
   - `DELETE /items/:id` - Delete

2. **Error Handling** - Return proper status codes:
   ```javascript
   if (!item) {
     return Response.json({ error: 'Not found' }, { status: 404 })
   }
   ```

3. **Validation** - Always validate input:
   ```javascript
   if (!body.name || !body.data) {
     return Response.json({ error: 'Missing fields' }, { status: 400 })
   }
   ```

4. **JSON Storage** - Store complex data as JSON:
   ```javascript
   run('INSERT INTO items (data) VALUES (?)', [JSON.stringify(obj)])
   ```

5. **WebSocket Channels** - Use drop name for pub/sub:
   ```javascript
   ws.publish('mydrop', JSON.stringify({ event: 'update' }))
   ```

## License

Same as parent project.