refactoring-patterns

name	Refactoring Patterns
description	Common refactoring patterns and code improvement techniques. Use when refactoring code, improving structure, or when user mentions refactoring, code smells, or code quality improvements.
allowed-tools	Read, Write, Edit, Bash

Refactoring Patterns

This skill provides common refactoring patterns, code smell detection, and structural improvement techniques.

What This Skill Provides

1. Code Smell Detection

• Identify duplicate code
• Detect complex functions
• Find poor naming
• Spot structural issues

2. Refactoring Patterns

• Extract Method
• Extract Class
• Rename for Clarity
• Simplify Conditionals
• Remove Duplication

3. Structural Improvements

• Module organization
• Dependency management
• Interface clarity
• Separation of concerns

4. Refactoring Scripts

• detect-duplicates.sh - Find duplicate code
• complexity-check.sh - Measure function complexity
• naming-analysis.sh - Analyze naming quality

Instructions

Detecting Code Smells

When analyzing code for refactoring opportunities:

1. Long Methods (> 50 lines)

   • Break into smaller functions
   • Use Extract Method pattern

2. Duplicate Code

   • Identify repeated patterns
   • Extract to shared utility

3. Complex Conditionals

   • Simplify with guard clauses
   • Use polymorphism or strategy pattern

4. Poor Naming

   • Use descriptive names
   • Follow naming conventions

Common Refactoring Patterns

Extract Method

Before:

function processOrder(order) {
  // validate
  if (!order.items) return false;
  if (!order.customer) return false;

  // calculate
  let total = 0;
  for (let item of order.items) {
    total += item.price * item.quantity;
  }

  // save
  db.save(order);
}

After:

function processOrder(order) {
  if (!validateOrder(order)) return false;
  const total = calculateTotal(order.items);
  saveOrder(order);
}

function validateOrder(order) {
  return order.items && order.customer;
}

function calculateTotal(items) {
  return items.reduce((sum, item) =>
    sum + (item.price * item.quantity), 0);
}

function saveOrder(order) {
  db.save(order);
}

Simplify Conditionals

Before:

if user.is_active and user.has_permission and not user.is_banned:
    allow_access()
else:
    deny_access()

After:

def can_access(user):
    return user.is_active and user.has_permission and not user.is_banned

if can_access(user):
    allow_access()
else:
    deny_access()

Extract Class

Before:

class User {
  name;
  email;
  street;
  city;
  zip;

  getAddress() {
    return `${this.street}, ${this.city} ${this.zip}`;
  }
}

After:

class Address {
  constructor(street, city, zip) {
    this.street = street;
    this.city = city;
    this.zip = zip;
  }

  toString() {
    return `${this.street}, ${this.city} ${this.zip}`;
  }
}

class User {
  name;
  email;
  address;

  constructor(name, email, address) {
    this.name = name;
    this.email = email;
    this.address = address;
  }
}

Refactoring Checklist

When refactoring code:

• Preserve existing functionality (no behavior changes)
• Run existing tests after each change
• Improve readability and maintainability
• Reduce complexity where possible
• Maintain backward compatibility
• Update documentation if structure changes
• Add tests for new extracted methods

Complexity Metrics

Cyclomatic Complexity - Number of paths through code

• 1-10: Simple, low risk
• 11-20: Moderate, medium risk
• 21-50: Complex, high risk
• 50+: Very complex, very high risk

Target: Keep functions under complexity of 10

Best Practices

• Refactor in small, incremental steps
• Run tests after each refactoring
• Commit refactorings separately from features
• Don't change functionality during refactoring
• Use descriptive names for extracted methods
• Keep functions focused on single responsibility

Success Criteria

• ✅ Code smells are identified and addressed
• ✅ Functions are small and focused
• ✅ Duplication is eliminated
• ✅ Naming is clear and descriptive
• ✅ Complexity is reduced
• ✅ Tests still pass after refactoring

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Plugin: 04-iterate Skill Type: Patterns + Analysis Auto-invocation: Yes (via description matching)