Refactoring Assistant

Overview

The Refactoring Assistant identifies code smells, suggests improvements, and helps execute safe refactoring operations that improve code quality without breaking functionality.

SKILL.md Template

---
name: refactor
description: Identify refactoring opportunities and guide safe code transformations. Use when improving code quality, reducing technical debt, or restructuring code.
---

When refactoring code, follow this approach:

## 1. Code Smell Detection
Identify common issues:

### Complexity Smells
- Long methods (>20 lines)
- Deep nesting (>3 levels)
- Long parameter lists (>4 params)
- Complex conditionals

### Duplication Smells
- Copy-paste code blocks
- Similar class structures
- Repeated logic patterns

### Coupling Smells
- Feature envy
- Inappropriate intimacy
- Middle man classes
- Message chains

## 2. Refactoring Techniques

### Extract Method
Before:
```javascript
function processOrder(order) {
  // validate
  if (!order.items) throw new Error('No items');
  if (!order.customer) throw new Error('No customer');
  // calculate
  let total = 0;
  for (const item of order.items) {
    total += item.price * item.quantity;
  }
  // apply discount
  if (order.customer.isPremium) {
    total *= 0.9;
  }
  return total;
}

After:

function processOrder(order) {
  validateOrder(order);
  const total = calculateTotal(order.items);
  return applyDiscount(total, order.customer);
}

Replace Conditional with Polymorphism

Introduce Parameter Object

Replace Magic Numbers with Constants

3. Safety Checklist

Before refactoring:

• Tests exist and pass
• Understand the full scope
• Identify all callers
• Plan incremental changes

After refactoring:

• All tests still pass
• No behavior changes
• Code review completed
• Performance verified

## Example Analysis

```markdown
## Refactoring Analysis: UserService.js

### Code Smells Found

1. **Long Method** (Line 45-120)
   - `processUserRegistration` is 75 lines
   - Suggestion: Extract validation, notification, and persistence

2. **Duplicated Code** (Lines 150, 220)
   - Email validation repeated in two places
   - Suggestion: Extract to shared utility

3. **Feature Envy** (Line 180)
   - `calculateUserScore` accesses too many fields from `statsService`
   - Suggestion: Move method to StatsService

### Recommended Refactorings

| Priority | Smell | Technique | Effort |
|----------|-------|-----------|--------|
| High | Long Method | Extract Method | Medium |
| High | Duplication | Extract Function | Low |
| Medium | Feature Envy | Move Method | Medium |

### Step-by-Step Plan

1. Add tests for `processUserRegistration` (if missing)
2. Extract `validateRegistration()` method
3. Extract `sendWelcomeEmail()` method
4. Extract `createUserRecord()` method
5. Run tests, verify behavior unchanged

Usage

/refactor src/services/UserService.ts

Or ask naturally:

How can I improve the code quality in this file?

Best Practices

• Refactor in small, testable increments
• Never refactor and add features simultaneously
• Use version control to checkpoint progress
• Keep tests green throughout the process