/refactoring-patterns

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]
trust_tier: 2
validation:
  schema_path: schemas/output.json
  validator_path: scripts/validate-config.json

Refactoring Patterns

<default_to_action> 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

</default_to_action>

Quick Reference Card

Common Refactorings

| Pattern | Before | After | |---------|--------|-------| | **Extract Method** | 50-line function | 5 small functions | | **Extract Class** | Class doing 5 things | 5 single-purpose classes | | **Parameter Object** | `fn(a,b,c,d,e,f)` | `fn(options)` | | **Replace Conditional** | `if (type === 'a') {...}` | Polymorphism | | **Pipeline** | Nested loops | `.filter().map().reduce()` |

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

| ❌ Anti-Pattern | Problem | ✅ Better | |-----------------|---------|-----------| | Without tests | No safety net | Write tests first | | Big bang | Rewrite everything | Small incremental steps | | For perfection | Endless tweaking | Good enough, move on | | Premature abstraction | Pattern not clear yet | Wait for Rule of Three | | During feature work | Mixed changes | Separate commits |

---

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-london-chicago/) - TDD refactor phase
• [code-review-quality](../code-review-quality/) - Review refactored code
• [xp-practices](../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.**