# 🌐 N8n Webhook Integration Guide

## Endpoint Configuration

### Production Endpoint
```
URL: https://n8n.lab.ubharajaya.ac.id/webhook/23c6993d-1792-48fb-ad1c-ffc78a3e6254
Method: POST
Content-Type: application/json
```

### Testing Endpoint
```
URL: https://n8n.lab.ubharajaya.ac.id/webhook-test/23c6993d-1792-48fb-ad1c-ffc78a3e6254
Method: POST
Content-Type: application/json
```

### Switch Configuration
**File**: `config/AppConfig.kt`
```kotlin
// Production (default)
const val USE_WEBHOOK = N8N_WEBHOOK_PROD

// Switch ke testing
const val USE_WEBHOOK = N8N_WEBHOOK_TEST
```

---

## Request Format

### JSON Payload Example

```json
{
  "npm": "12345678",
  "nama": "John Doe",
  "latitude": -6.896123,
  "longitude": 107.610056,
  "timestamp": 1704067200000,
  "foto_base64": "iVBORw0KGgoAAAANSUhEUgAAA...ABJRU5ErkJggg=="
}
```

### Field Descriptions

| Field | Type | Example | Notes |
|-------|------|---------|-------|
| `npm` | String | "12345678" | Nomor Pokok Mahasiswa |
| `nama` | String | "John Doe" | Nama lengkap mahasiswa |
| `latitude` | Number | -6.896123 | Koordinat latitude (format: 6 desimal) |
| `longitude` | Number | 107.610056 | Koordinat longitude (format: 6 desimal) |
| `timestamp` | Number | 1704067200000 | Unix timestamp dalam milliseconds |
| `foto_base64` | String | "iVBORw0K..." | Foto compressed JPEG dalam Base64 |

---

## Response Handling

### Success Response (HTTP 200/201)

```json
{
  "success": true,
  "message": "Attendance recorded successfully",
  "data": {
    "id": "65a7b8c9d0e1f2g3h4i5j6k7",
    "npm": "12345678",
    "nama": "John Doe",
    "timestamp": 1704067200000,
    "status": "accepted"
  }
}
```

**App Behavior**:
- Status badge: ✅ ACCEPTED (green)
- Message: "✓ Absensi berhasil dikirim!"
- Database: Save with status = "accepted"

### Error Response (HTTP 400+)

```json
{
  "error": true,
  "message": "Location outside of allowed area",
  "code": "LOCATION_INVALID"
}
```

**App Behavior**:
- Status badge: ✗ REJECTED (red)
- Message: "✗ Gagal: Server returned code: 400"
- Database: Save with status = "rejected"

### Server Timeout (no response)

**App Behavior**:
- After 10 seconds: Show error
- Message: "✗ Gagal: timeout"
- Database: Save with status = "rejected"

---

## Real-World Examples

### Example 1: Valid Attendance

**Request**:
```bash
curl -X POST https://n8n.lab.ubharajaya.ac.id/webhook/23c6993d-1792-48fb-ad1c-ffc78a3e6254 \
  -H "Content-Type: application/json" \
  -d '{
    "npm": "12345678",
    "nama": "Arif Rachman Dwi",
    "latitude": -6.8961,
    "longitude": 107.6100,
    "timestamp": 1704067200000,
    "foto_base64": "[COMPRESSED_JPEG_BASE64]"
  }'
```

**Response** (Success):
```json
HTTP/1.1 200 OK
{
  "success": true,
  "message": "Attendance recorded",
  "status": "accepted"
}
```

---

### Example 2: Location Out of Area

**Request**:
```bash
curl -X POST https://n8n.lab.ubharajaya.ac.id/webhook/23c6993d-1792-48fb-ad1c-ffc78a3e6254 \
  -H "Content-Type: application/json" \
  -d '{
    "npm": "12345678",
    "nama": "Arif Rachman Dwi",
    "latitude": -6.8, 
    "longitude": 107.5,
    "timestamp": 1704067200000,
    "foto_base64": "[COMPRESSED_JPEG_BASE64]"
  }'
```

**Response** (Out of Radius):
```json
HTTP/1.1 400 Bad Request
{
  "error": true,
  "message": "Location is outside of allowed area",
  "code": "LOCATION_INVALID",
  "distance": 12500
}
```

---

## Image Compression Details

### Photo Processing in App

1. **Capture**: Camera Intent mengambil JPEG thumbnail
2. **Compress**: Bitmap compressed dengan quality 80%
3. **Encode**: JPEG bytes di-encode ke Base64
4. **Size**: Typical size ~50-100 KB (Base64 ~70-130 KB)

### Configuration

**File**: `config/AppConfig.kt`
```kotlin
const val PHOTO_COMPRESS_QUALITY = 80  // Range: 0-100
```

### Compression Quality Reference

| Quality | Use Case |
|---------|----------|
| 50 | Minimal quality, smallest size |
| 80 | Balanced (DEFAULT) |
| 100 | Maximum quality, largest size |

---

## N8n Workflow Integration

### Expected Workflow Steps

1. **Webhook Trigger**
   - Menerima POST request dengan JSON payload
   - Validasi format & required fields

2. **Data Validation**
   - Check NPM format
   - Validate coordinates (lat/lon ranges)
   - Validate timestamp (not in future)
   - Check foto_base64 format

3. **Location Validation**
   - Calculate distance from campus center
   - Check if within allowed radius
   - Return error if out of bounds

4. **Photo Processing**
   - Decode Base64 image
   - Optional: Save to storage
   - Optional: Run face detection
   - Optional: Save metadata

5. **Database Storage**
   - Insert into attendance table
   - Record timestamp & location
   - Update student statistics

6. **Response**
   - Return HTTP 200 + success message
   - Or HTTP 400 + error message

### Sample N8n Workflow JSON

See `n8n-workflow-EAS.json` in project root for complete workflow configuration.

---

## Monitoring & Testing

### Monitoring URL
```
https://ntfy.ubharajaya.ac.id/EAS
```

Monitor real-time webhook notifications:
- New attendance submissions
- Errors & rejections
- System alerts

### Spreadsheet Tracking
```
https://docs.google.com/spreadsheets/d/1jH15MfnNgpPGuGeid0hYfY7fFUHCEFbCmg8afTyyLZs/
```

Track all recorded attendance data:
- Student information
- Location & timestamp
- Photo references
- Status & notes

### Testing Endpoint
```
https://n8n.lab.ubharajaya.ac.id/webhook-test/23c6993d-1792-48fb-ad1c-ffc78a3e6254
```

Use for testing before production:
- Simulates webhook behavior
- Doesn't actually save to production database
- Useful for app development & testing

---

## Implementation Code Reference

### Sending Request (AttendanceRepository.kt)

```kotlin
fun sendToN8n(
    onSuccess: () -> Unit,
    onError: (String) -> Unit,
    attendance: Attendance,
    foto: Bitmap
) {
    thread {
        try {
            val url = URL(AppConfig.USE_WEBHOOK)
            val conn = url.openConnection() as HttpURLConnection
            
            conn.requestMethod = "POST"
            conn.setRequestProperty("Content-Type", "application/json")
            conn.doOutput = true
            conn.connectTimeout = 10000
            conn.readTimeout = 10000
            
            // Create JSON payload
            val json = JSONObject().apply {
                put("npm", attendance.npm)
                put("nama", attendance.nama)
                put("latitude", attendance.latitude)
                put("longitude", attendance.longitude)
                put("timestamp", attendance.timestamp)
                put("foto_base64", bitmapToBase64(foto))
            }
            
            // Send request
            conn.outputStream.use {
                it.write(json.toString().toByteArray())
                it.flush()
            }
            
            // Handle response
            val responseCode = conn.responseCode
            if (responseCode == 200 || responseCode == 201) {
                onSuccess()
            } else {
                onError("Server returned code: $responseCode")
            }
            
            conn.disconnect()
        } catch (e: Exception) {
            onError(e.message ?: "Unknown error")
        }
    }
}
```

---

## Troubleshooting

### 1. Connection Timeout
```
Error: "✗ Gagal: timeout"
Solution:
- Check internet connection
- Verify URL is correct
- Test network connectivity
- Increase timeout if needed
```

### 2. Invalid JSON Response
```
Error: "✗ Gagal: JSON parsing error"
Solution:
- Verify payload format
- Check all required fields present
- Validate Base64 string
- Check JSON syntax
```

### 3. 400 Bad Request
```
Error: "✗ Gagal: Server returned code: 400"
Possible causes:
- Invalid NPM format
- Coordinates out of valid range
- Missing required fields
- Malformed Base64 image
```

### 4. 401 Unauthorized
```
Error: "✗ Gagal: Server returned code: 401"
Solution:
- Check webhook URL is correct
- Verify webhook is active in N8n
- Check authentication headers if required
```

### 5. 403 Forbidden
```
Error: "✗ Gagal: Server returned code: 403"
Solution:
- Verify webhook permissions
- Check if webhook is enabled
- Verify IP whitelist settings
```

### 6. 500 Server Error
```
Error: "✗ Gagal: Server returned code: 500"
Solution:
- Check N8n workflow logs
- Verify database connection
- Check N8n service status
- Contact system administrator
```

---

## Security Considerations

### Data Protection
- All data sent over HTTPS
- No sensitive data stored in logs
- Base64 photo cannot be directly viewed
- Timestamp validation prevents replay attacks

### Rate Limiting
- Consider implementing rate limiting on N8n
- Prevent duplicate submissions
- Monitor for unusual activity

### Validation
- Server should validate all inputs
- Reject invalid coordinates
- Verify photo file integrity
- Check timestamp within reasonable window

---

## API Contract

### Version Information
```
API Version: v1
Last Updated: 2025-01-14
Endpoint Status: Active
```

### Backward Compatibility
- Current version: 1.0
- No breaking changes planned
- All fields are required
- Response format is stable

### Future Enhancements
- [ ] Support for batch submissions
- [ ] Webhook signature verification
- [ ] Custom error codes
- [ ] Rate limiting headers
- [ ] API versioning in URL

---

**Document Version**: 1.0  
**Last Updated**: 2025-01-14  
**Status**: ✅ Complete & Current