name: refactoring-patterns
description: "Apply safe refactoring patterns to improve code structure without changing behavior. Use when cleaning up code, reducing technical debt, or improving maintainability."
category: development-practices
priority: medium
tokenEstimate: 1000
agents: [qe-code-reviewer, qe-quality-analyzer, qe-test-refactorer]
implementation_status: optimized
optimization_version: 1.0
last_optimized: 2025-12-03
dependencies: []
quick_reference_card: true
tags: [refactoring, code-quality, technical-debt, maintainability, clean-code]

Refactoring Patterns

When refactoring:
1. ENSURE tests pass (never refactor without tests)
2. MAKE small change (one refactoring at a time)
3. RUN tests (must stay green)
4. COMMIT (save progress)
5. REPEAT

Safe Refactoring Cycle:

npm test               # Green ✅
# Make ONE small change
npm test               # Still green ✅
git commit -m "refactor: extract calculateTotal"
# Repeat

Code Smells → Refactoring:
| Smell | Refactoring |
|-------|-------------|
| Long method (>20 lines) | Extract Method |
| Large class | Extract Class |
| Long parameter list (>3) | Introduce Parameter Object |
| Duplicated code | Extract Method/Class |
| Complex conditional | Decompose Conditional |
| Magic numbers | Named Constants |
| Nested loops | Replace Loop with Pipeline |

NEVER REFACTOR:
- Without tests (write tests first)
- When deadline is tomorrow
- Code you don't understand
- Code that works and won't be touched

Quick Reference Card

Common Refactorings

The Rule of Three

1. First time → Just do it
2. Second time → Wince and duplicate
3. Third time → Refactor

Key Patterns

Extract Method

// Before: Long method
function processOrder(order) {
  // 50 lines of validation, calculation, saving, emailing...
}

// After: Clear responsibilities
function processOrder(order) {
  validateOrder(order);
  const pricing = calculatePricing(order);
  const saved = saveOrder(order, pricing);
  sendConfirmationEmail(saved);
  return saved;
}

Replace Loop with Pipeline

// Before
let results = [];
for (let item of items) {
  if (item.inStock) {
    results.push(item.name.toUpperCase());
  }
}

// After
const results = items
  .filter(item => item.inStock)
  .map(item => item.name.toUpperCase());

Decompose Conditional

// Before
if (order.total > 1000 && customer.isPremium && allInStock(order)) {
  return 'FREE_SHIPPING';
}

// After
function isEligibleForFreeShipping(order, customer) {
  return isLargeOrder(order) &&
         isPremiumCustomer(customer) &&
         allInStock(order);
}

Refactoring Anti-Patterns

Agent Integration

// Detect code smells
const smells = await Task("Detect Code Smells", {
  source: 'src/services/',
  patterns: ['long-method', 'large-class', 'duplicate-code']
}, "qe-quality-analyzer");

// Safe refactoring with test verification
await Task("Verify Refactoring", {
  beforeCommit: 'abc123',
  afterCommit: 'def456',
  expectSameBehavior: true
}, "qe-test-executor");

Agent Coordination Hints

Memory Namespace

aqe/refactoring/
├── smells/*          - Detected code smells
├── suggestions/*     - Refactoring recommendations
├── verifications/*   - Behavior preservation checks
└── history/*         - Refactoring log

Fleet Coordination

const refactoringFleet = await FleetManager.coordinate({
  strategy: 'refactoring',
  agents: [
    'qe-quality-analyzer',   // Identify targets
    'qe-test-generator',     // Add safety tests
    'qe-test-executor',      // Verify behavior
    'qe-test-refactorer'     // TDD refactor phase
  ],
  topology: 'sequential'
});

Related Skills

• tdd-london-chicago - TDD refactor phase
• code-review-quality - Review refactored code
• xp-practices - Collective ownership

Remember

Refactoring is NOT:
- Adding features
- Fixing bugs
- Performance optimization
- Rewriting from scratch

Refactoring IS:
- Improving structure
- Making code clearer
- Reducing complexity
- Removing duplication
- Without changing behavior

Always have tests. Always take small steps. Always keep tests green.