# QR Code Gateway Setup

## Overview

The gateway registration now includes QR code generation for quick and easy Android app configuration. When a new gateway is created, the system automatically generates a QR code containing all necessary configuration data.

## What's Included in the QR Code

The QR code contains a JSON payload with:

```json
{
  "api_key": "gw_live_a6e2b250dade8f6501256a8717723fc3f8ab7d4e7cb26aad470d65ee8478a82c",
  "api_base_url": "http://localhost:3000",
  "websocket_url": "ws://localhost:3000/cable",
  "version": "1.0"
}
```

### Fields Explained

| Field | Description | Example |
|-------|-------------|---------|
| `api_key` | Gateway authentication key | `gw_live_...` (64 chars) |
| `api_base_url` | Base URL for API endpoints | `http://localhost:3000` or `https://api.example.com` |
| `websocket_url` | WebSocket connection URL | `ws://localhost:3000/cable` or `wss://api.example.com/cable` |
| `version` | Configuration format version | `1.0` |

## Features

### 1. QR Code Display

**Location**: Gateway creation success page (`/admin/gateways/:id` after creation)

**Visual Features**:
- High-quality SVG QR code
- Error correction level: High (L=H)
- White background with border
- Centered display
- Info badge explaining contents

### 2. Manual Configuration Fallback

If QR scanning is unavailable, the page also displays:
- API Base URL (with individual copy button)
- WebSocket URL (with individual copy button)
- API Key (with individual copy button)
- "Copy All" button to copy all three fields at once

### 3. Copy to Clipboard Functions

**Individual Field Copy**:
```javascript
copyField('api-base-url')  // Copies just the API base URL
copyField('ws-url')        // Copies just the WebSocket URL
copyField('api-key')       // Copies just the API key
```

**Copy All Configuration**:
```javascript
copyAllConfig()  // Copies all fields as formatted text
```

Output format:
```
API Base URL: http://localhost:3000
WebSocket URL: ws://localhost:3000/cable
API Key: gw_live_a6e2b250dade8f6501256a8717723fc3f8ab7d4e7cb26aad470d65ee8478a82c
```

## Implementation Details

### Gem Used

**rqrcode** v2.0+
- Pure Ruby QR code generator
- No external dependencies
- SVG output support
- High error correction

Added to `Gemfile`:
```ruby
gem "rqrcode", "~> 2.0"
```

### Controller Method

**File**: `app/controllers/admin/gateways_controller.rb`

```ruby
def generate_qr_code_data(api_key)
  require "rqrcode"

  # Determine URLs based on request
  base_url = request.base_url
  ws_url = request.base_url.sub(/^http/, "ws") + "/cable"

  # Create JSON configuration
  config_data = {
    api_key: api_key,
    api_base_url: base_url,
    websocket_url: ws_url,
    version: "1.0"
  }.to_json

  # Generate QR code with high error correction
  qr = RQRCode::QRCode.new(config_data, level: :h)

  # Return as SVG string
  qr.as_svg(
    offset: 0,
    color: "000",
    shape_rendering: "crispEdges",
    module_size: 4,
    standalone: true,
    use_path: true
  )
end
```

### View Integration

**File**: `app/views/admin/gateways/show.html.erb`

The QR code is displayed using:
```erb
<div class="bg-white p-4 rounded-lg shadow-inner border-2 border-gray-200">
  <%= @qr_code_data.html_safe %>
</div>
```

## URL Detection

The system automatically detects the correct URLs based on the request:

### Development
- Base URL: `http://localhost:3000`
- WebSocket URL: `ws://localhost:3000/cable`

### Production (HTTP)
- Base URL: `http://api.example.com`
- WebSocket URL: `ws://api.example.com/cable`

### Production (HTTPS) - Recommended
- Base URL: `https://api.example.com`
- WebSocket URL: `wss://api.example.com/cable`

**Note**: WebSocket URL automatically changes from `http` to `ws` and `https` to `wss`.

## Android App Integration

### QR Code Scanning Flow

1. **User opens Android SMS Gateway app**
2. **Taps "Scan QR Code" or similar option**
3. **Camera opens with QR scanner**
4. **Scans the QR code from admin interface**
5. **App parses JSON configuration**
6. **All fields auto-populated**:
   - API Base URL field
   - WebSocket URL field
   - API Key field
7. **User taps "Save" or "Connect"**
8. **App connects to server**
9. **Gateway appears as "Online" in admin interface**

### Expected Android App Code

The Android app should:

1. **Scan QR Code**:
```kotlin
// Using ML Kit or ZXing library
val result = qrCodeScanner.scan()
val jsonString = result.text
```

2. **Parse JSON**:
```kotlin
val config = JSONObject(jsonString)
val apiKey = config.getString("api_key")
val apiBaseUrl = config.getString("api_base_url")
val websocketUrl = config.getString("websocket_url")
val version = config.getString("version")
```

3. **Validate Version**:
```kotlin
if (version != "1.0") {
    showError("Unsupported configuration version")
    return
}
```

4. **Save Configuration**:
```kotlin
sharedPreferences.edit().apply {
    putString("api_key", apiKey)
    putString("api_base_url", apiBaseUrl)
    putString("websocket_url", websocketUrl)
    apply()
}
```

5. **Connect to Server**:
```kotlin
// Connect to WebSocket
webSocketClient.connect(websocketUrl, apiKey)

// Test API connection
apiClient.setBaseUrl(apiBaseUrl)
apiClient.setAuthToken(apiKey)
apiClient.sendHeartbeat()
```

## Security Considerations

### QR Code Security

✅ **Secure**:
- QR code displayed only once after creation
- Requires admin authentication to view
- Session-based display (not in URL)
- Page cannot be refreshed to see QR code again

⚠️ **Warning**:
- Anyone with camera access to the screen can scan the QR code
- QR code contains full API key in plaintext JSON
- Suitable for secure environments only

### Best Practices

1. **Display Environment**:
   - Only display QR code in secure locations
   - Ensure no cameras/recording devices nearby
   - Clear screen after scanning

2. **Network Security**:
   - Use HTTPS/WSS in production (`config.force_ssl = true`)
   - Never use HTTP/WS in production
   - Implement rate limiting on WebSocket connections

3. **Key Management**:
   - QR code shown only once during gateway creation
   - If compromised, deactivate gateway and create new one
   - Regularly audit active gateways

4. **Mobile App Security**:
   - Store configuration in encrypted SharedPreferences
   - Use Android Keystore for API key storage
   - Implement certificate pinning for API calls
   - Validate SSL certificates for WebSocket connections

## Troubleshooting

### QR Code Not Displaying

**Check**:
1. `rqrcode` gem installed: `bundle show rqrcode`
2. Controller generates QR code: Check `@qr_code_data` in view
3. Browser console for JavaScript errors
4. View source - SVG should be present

**Fix**:
```bash
bundle install
bin/rails restart
```

### QR Code Too Complex to Scan

**Symptom**: QR scanner can't read the code

**Cause**: JSON payload too long (rare, but possible with very long URLs)

**Solution**:
- Use shorter domain names
- Reduce module_size in controller (current: 4)
- Lower error correction level (current: :h, try :m or :l)

### Wrong URLs in QR Code

**Symptom**: QR code contains `localhost` in production

**Cause**: `request.base_url` not detecting correctly

**Fix**: Set environment variables in production
```bash
# .env or config
RAILS_FORCE_SSL=true
RAILS_RELATIVE_URL_ROOT=https://api.example.com
```

Or override in controller:
```ruby
base_url = ENV['API_BASE_URL'] || request.base_url
```

### Android App Can't Parse QR Code

**Symptom**: App shows "Invalid QR code" error

**Causes**:
1. QR code scanner library issue
2. JSON parsing error
3. Wrong configuration version

**Debug**:
```kotlin
try {
    val json = JSONObject(qrCodeText)
    Log.d("QR", "API Key: ${json.getString("api_key")}")
    Log.d("QR", "Base URL: ${json.getString("api_base_url")}")
    Log.d("QR", "WS URL: ${json.getString("websocket_url")}")
} catch (e: Exception) {
    Log.e("QR", "Parse error: ${e.message}")
}
```

## Testing

### Manual QR Code Test

1. **Create Test Gateway**:
```bash
bin/rails console
```

```ruby
gateway = Gateway.new(
  device_id: "test-qr-001",
  name: "QR Test Gateway",
  priority: 1,
  status: "offline"
)
raw_key = gateway.generate_api_key!
puts "Gateway ID: #{gateway.id}"
puts "Raw Key: #{raw_key}"
```

2. **Navigate to Success Page**:
   - Visit: `http://localhost:3000/admin/gateways/new`
   - Fill form and submit
   - Should redirect to gateway show page with QR code

3. **Test QR Code**:
   - Open QR code scanner app on phone
   - Scan the displayed QR code
   - Verify JSON payload contains all fields

4. **Test Copy Buttons**:
   - Click individual copy buttons (API URL, WS URL, API Key)
   - Verify green checkmark feedback
   - Click "Copy All" button
   - Paste in text editor - verify format

### Automated Test

```ruby
# test/controllers/admin/gateways_controller_test.rb
test "should generate QR code on gateway creation" do
  post admin_gateways_url, params: {
    gateway: {
      device_id: "test-001",
      name: "Test Gateway",
      priority: 5
    }
  }

  assert_response :redirect

  gateway = Gateway.last
  get admin_gateway_url(gateway)

  assert_response :success
  assert_select 'svg' # QR code should be present as SVG
end
```

## Configuration Examples

### Local Development
```json
{
  "api_key": "gw_live_abc123...",
  "api_base_url": "http://localhost:3000",
  "websocket_url": "ws://localhost:3000/cable",
  "version": "1.0"
}
```

### Staging Environment
```json
{
  "api_key": "gw_live_def456...",
  "api_base_url": "https://staging-api.example.com",
  "websocket_url": "wss://staging-api.example.com/cable",
  "version": "1.0"
}
```

### Production Environment
```json
{
  "api_key": "gw_live_ghi789...",
  "api_base_url": "https://api.example.com",
  "websocket_url": "wss://api.example.com/cable",
  "version": "1.0"
}
```

## Future Enhancements

### Possible Improvements

1. **Download QR Code**:
   - Add "Download QR Code" button
   - Generate PNG image
   - Allow saving for later

2. **Email QR Code**:
   - Send QR code via email
   - Secure time-limited link
   - Auto-expires after 1 hour

3. **Multiple QR Code Formats**:
   - Different sizes (small, medium, large)
   - Different error correction levels
   - PNG, SVG, PDF options

4. **Configuration Presets**:
   - Save common configurations
   - Apply preset to multiple gateways
   - Template system

5. **Advanced Security**:
   - Encrypted QR code payload
   - Time-limited configuration URLs
   - Two-factor gateway activation

## Summary

✅ **Implemented**: QR code generation with all gateway configuration
✅ **Features**: Scan QR code OR manual copy/paste
✅ **Security**: One-time display, session-based, admin-only
✅ **UX**: Copy buttons with visual feedback, clear instructions
✅ **Production Ready**: Automatic URL detection (HTTP/HTTPS/WS/WSS)

The QR code feature makes gateway setup much faster and reduces configuration errors by eliminating manual typing of long API keys!