Codebase Cleanup Refactor Clean

# Refactor and Clean Code Implementation Playbook

This file contains detailed patterns, checklists, and code samples referenced by the skill.

## Instructions

### 1. Code Analysis
First, analyze the current code for:
- **Code Smells**
  - Long methods/functions (>20 lines)
  - Large classes (>200 lines)
  - Duplicate code blocks
  - Dead code and unused variables
  - Complex conditionals and nested loops
  - Magic numbers and hardcoded values
  - Poor naming conventions
  - Tight coupling between components
  - Missing abstractions

- **SOLID Violations**
  - Single Responsibility Principle violations
  - Open/Closed Principle issues
  - Liskov Substitution problems
  - Interface Segregation concerns
  - Dependency Inversion violations

- **Performance Issues**
  - Inefficient algorithms (O(n²) or worse)
  - Unnecessary object creation
  - Memory leaks potential
  - Blocking operations
  - Missing caching opportunities

### 2. Refactoring Strategy

Create a prioritized refactoring plan:

**Immediate Fixes (High Impact, Low Effort)**
- Extract magic numbers to constants
- Improve variable and function names
- Remove dead code
- Simplify boolean expressions
- Extract duplicate code to functions

**Method Extraction**
```
# Before
def process_order(order):
    # 50 lines of validation
    # 30 lines of calculation
    # 40 lines of notification

# After
def process_order(order):
    validate_order(order)
    total = calculate_order_total(order)
    send_order_notifications(order, total)
```

**Class Decomposition**
- Extract responsibilities to separate classes
- Create interfaces for dependencies
- Implement dependency injection
- Use composition over inheritance

**Pattern Application**
- Factory pattern for object creation
- Strategy pattern for algorithm variants
- Observer pattern for event handling
- Repository pattern for data access
- Decorator pattern for extending behavior

### 3. SOLID Principles in Action

Provide concrete examples of applying each SOLID principle:

**Single Responsibility Principle (SRP)**
```python
# BEFORE: Multiple responsibilities in one class
class UserManager:
    def create_user(self, data):
        # Validate data
        # Save to database
        # Send welcome email
        # Log activity
        # Update cache
        pass

# AFTER: Each class has one responsibility
class UserValidator:
    def validate(self, data): pass

class UserRepository:
    def save(self, user): pass

class EmailService:
    def send_welcome_email(self, user): pass

class UserActivityLogger:
    def log_creation(self, user): pass

class UserService:
    def __init__(self, validator, repository, email_service, logger):
        self.validator = validator
        self.repository = repository
        self.email_service = email_service
        self.logger = logger

    def create_user(self, data):
        self.validator.validate(data)
        user = self.repository.save(data)
        self.email_service.send_welcome_email(user)
        self.logger.log_creation(user)
        return user
```

**Open/Closed Principle (OCP)**
```python
# BEFORE: Modification required for new discount types
class DiscountCalculator:
    def calculate(self, order, discount_type):
        if discount_type == "percentage":
            return order.total * 0.1
        elif discount_type == "fixed":
            return 10
        elif discount_type == "tiered":
            # More logic
            pass

# AFTER: Open for extension, closed for modification
from abc import ABC, abstractmethod

class DiscountStrategy(ABC):
    @abstractmethod
    def calculate(self, order): pass

class PercentageDiscount(DiscountStrategy):
    def __init__(self, percentage):
        self.percentage = percentage

    def calculate(self, order):
        return order.total * self.percentage

class FixedDiscount(DiscountStrategy):
    def __init__(self, amount):
        self.amount = amount

    def calculate(self, order):
        return self.amount

class TieredDiscoun