Logger Usage Rules for Flutter App

# Logger Usage Rules for Flutter App

## Overview
This project uses a custom Logger class instead of `print()` and `debugPrint()` statements. The logger provides structured, categorized, and colorized logging with different levels and categories.

## Import Statement
Always import the logger at the top of your files:
```dart
import 'package:pupilica_hackathon/core/helpers/logger/logger.dart';
```

## When to Use Logger Instead of print/debugPrint

### ✅ ALWAYS Use Logger For:

1. **Debugging Information**
   - Variable values during development
   - Function entry/exit points
   - State changes in BLoC
   - API request/response data

2. **Error Handling**
   - Exception catching and logging
   - API errors
   - Validation failures
   - System errors

3. **User Flow Tracking**
   - Navigation events
   - Button clicks
   - Form submissions
   - Authentication events

4. **Performance Monitoring**
   - Function execution times
   - API response times
   - Memory usage warnings

5. **Business Logic Events**
   - OCR processing results
   - Data processing steps
   - Feature usage tracking

### ❌ NEVER Use print/debugPrint For:

1. **Production Code** - Logger provides better control
2. **Structured Data** - Logger handles JSON/Map formatting
3. **Error Context** - Logger includes stack traces
4. **Categorized Logs** - Logger provides category-based filtering
5. **Colorized Output** - Logger provides visual distinction

## Logger Methods and Usage

### 1. Debug Logging
```dart
// For development debugging
Logger.debug('User tapped login button', category: LogCategory.ui);
Logger.debug('API response received', category: LogCategory.api, data: {'status': 200, 'data': responseData});
```

### 2. Info Logging
```dart
// For general information
Logger.info('User successfully logged in', category: LogCategory.auth);
Logger.info('Navigation to home screen', category: LogCategory.navigation);
```

### 3. Warning Logging
```dart
// For potential issues
Logger.warning('API response time exceeded 5 seconds', category: LogCategory.api);
Logger.warning('Low memory detected', category: LogCategory.general);
```

### 4. Error Logging
```dart
// For errors and exceptions
try {
  // Some operation
} catch (e, stackTrace) {
  Logger.error('Failed to process OCR image', 
    category: LogCategory.ocr, 
    error: e, 
    stackTrace: stackTrace);
}

// For API errors
Logger.error('Login failed', 
  category: LogCategory.auth, 
  data: {'error_code': 401, 'message': 'Invalid credentials'});
```

### 5. Success Logging
```dart
// For successful operations
Logger.success('OCR processing completed successfully', category: LogCategory.ocr);
Logger.success('Data saved to database', category: LogCategory.database);
```

## Log Categories

Use appropriate categories for better log organization:

- `LogCategory.splash` - Splash screen related logs
- `LogCategory.navigation` - Navigation and routing logs
- `LogCategory.api` - API calls and responses
- `LogCategory.database` - Database operations
- `LogCategory.ui` - UI interactions and state changes
- `LogCategory.auth` - Authentication and authorization
- `LogCategory.ocr` - OCR processing and image analysis
- `LogCategory.general` - General purpose logs

## Code Examples

### BLoC Event Handling
```dart
// ❌ Wrong - using print
Future<FutureOr<void>> _onLoginEvent(
  LoginEvent event,
  Emitter<LoginState> emit,
) async {
  print('Login event received'); // ❌ Don't use print
  // ... logic
}

// ✅ Correct - using Logger
Future<FutureOr<void>> _onLoginEvent(
  LoginEvent event,
  Emitter<LoginState> emit,
) async {
  Logger.info('Login event received', category: LogCategory.auth);
  // ... logic
}
```

### Error Handling
```dart
// ❌ Wrong - using print for errors
try {
  await apiCall();
} catch (e) {
  print('Error: $e'); // ❌ Don't use print for errors
}

// ✅ Correct - using Logger
try {
  await apiCall();
} catch (e, stackTrace) {
  Logger.error('API call failed', 
    category: LogCategory.api, 
    error: e, 
    stackTrace: stackTrace);
}
```

### UI State Changes
```dart
// ❌ Wrong - using debugPrint
void _onButtonPressed() {
  debugPrint('Button pressed'); // ❌ Don't use debugPrint
  setState(() {
    // state change
  });
}

// ✅ Correct - using Logger
void _onButtonPressed() {
  Logger.debug('Button pressed', category: LogCategory.ui);
  setState(() {
    // state change
  });
}
```

### API Response Logging
```dart
// ❌ Wrong - using print
Future<ApiResponse> fetchData() async {
  print('Fetching data from API'); // ❌ Don't use print
  final response = await http.get(uri);
  print('Response: ${response.body}'); // ❌ Don't use print
  return ApiResponse.fromJson(jsonDecode(response.body));
}

// ✅ Correct - using Logger
Future<ApiResponse> fetchData() async {
  Logger.info('Fetching data from API', category: LogCategory.api);
  final response = await http.get(uri);
  Logger.debug('API response received', 
    category: LogCategory.api, 
    data: {'status_code': response.statusCode, 'body_length': response.body.length});
  return ApiResponse.fromJson(jsonDecode(response.body));
}
```

## Best Practices

### 1. Consistent Category Usage
- Always use the most specific category
- Group related logs under the same category
- Use `LogCategory.general` only when no other category fits

### 2. Meaningful Messages
```dart
// ❌ Poor message
Logger.debug('test', category: LogCategory.general);

// ✅ Good message
Logger.debug('User profile loaded successfully', category: LogCategory.ui);
```

### 3. Structured Data
```dart
// ✅ Include relevant data for debugging
Logger.debug('OCR processing started', 
  category: LogCategory.ocr, 
  data: {
    'image_size': '${image.width}x${image.height}',
    'processing_time': '${DateTime.now().millisecondsSinceEpoch}'
  });
```

### 4. Error Context
```dart
// ✅ Always include error and stack trace for exceptions
try {
  // risky operation
} catch (e, stackTrace) {
  Logger.error('Operation failed', 
    category: LogCategory.general, 
    error: e, 
    stackTrace: stackTrace,
    data: {'operation': 'data_processing', 'user_id': userId});
}
```

### 5. Performance Logging
```dart
// ✅ Log performance metrics
final stopwatch = Stopwatch()..start();
// ... operation
stopwatch.stop();
Logger.info('Operation completed', 
  category: LogCategory.general, 
  data: {'duration_ms': stopwatch.elapsedMilliseconds});
```

## Migration Guidelines

When refactoring existing code:

1. **Find all print/debugPrint statements**
2. **Determine the appropriate log level** (debug, info, warning, error, success)
3. **Choose the right category** based on context
4. **Add structured data** if relevant
5. **Include error handling** for try-catch blocks

## Development vs Production

- **Development**: Use all log levels liberally for debugging
- **Production**: Consider removing or reducing debug logs
- **Error logs**: Always keep in production for monitoring
- **Info logs**: Keep important business logic logs

## Log Output Format

The logger provides structured output with:
- Timestamp
- App name
- Category emoji and name
- Level emoji and name
- Message
- Additional data (if provided)
- Color coding for different levels

Example output:
```
[2024-01-15T10:30:45.123Z] Pupilica AI 🚀 SPLASH ℹ️ INFO: Splash screen initialized
[2024-01-15T10:30:45.456Z] Pupilica AI 🌐 API 🐛 DEBUG: API request sent | Data: {url: /api/login, method: POST}
```

This structured approach makes debugging much more efficient and provides better insights into application behavior.