/refactor

description: 'Safe, incremental refactoring with SOLID evaluation. Trigger with "refactor this", "improve the code", "clean up", "restructure", "improve maintainability".'
allowed-tools:
  - Read
  - Edit
  - Grep
  - Glob
  - Bash

Safe, incremental refactoring with SOLID evaluation

Performs safe, step-by-step code refactoring with quantitative SOLID principles evaluation. Visualizes technical debt and clarifies improvement priorities.

Usage

# Identify complex code and create refactoring plan
find . -name "*.js" -exec wc -l {} + | sort -rn | head -10
"Refactor large files to reduce complexity"

# Detect and consolidate duplicate code
grep -r "function processUser" . --include="*.js"
"Consolidate duplicate functions using Extract Method"

# Evaluate SOLID principles violations
grep -r "class.*Service" . --include="*.js" | head -10
"Assess whether these classes follow Single Responsibility Principle"

Basic Examples

# Find long methods
grep -A 50 "function" src/*.js | grep -B 50 -A 50 "return" | wc -l
"Split methods over 50 lines using Extract Method"

# Find complex conditions
grep -r "if.*if.*if" . --include="*.js"
"Improve nested conditions using Strategy pattern"

# Find code smells
grep -r "TODO\|FIXME\|HACK" . --exclude-dir=node_modules
"Resolve technical debt in comments"

Refactoring Techniques

Extract Method (Split Big Functions)

// Before: Long method
function processOrder(order) {
  // 50 lines of complex processing
}

// After: Separation of responsibilities
function processOrder(order) {
  validateOrder(order);
  calculateTotal(order);
  saveOrder(order);
}

Replace Conditional with Polymorphism (Remove Switch/If Chains)

// Before: switch statement
function getPrice(user) {
  switch (user.type) {
    case "premium":
      return basePrice * 0.8;
    case "regular":
      return basePrice;
  }
}

// After: Strategy pattern
class PremiumPricing {
  calculate(basePrice) {
    return basePrice * 0.8;
  }
}

SOLID Principles Scoring (0-100 points)

Evaluation Criteria and Scoring

S - Single Responsibility (20 points)
├─ Number of responsibilities: 1 (20pts) | 2 (15pts) | 3 (10pts) | 4+ (5pts)
├─ Method count: <7 (+5pts) | 7-15 (+3pts) | >15 (0pts)
├─ Clear reasons for change: Clear (+5pts) | Unclear (0pts)
└─ Example score: UserService (auth + data processing) = 10 points

O - Open/Closed (20 points)
├─ Extension points: Strategy/Template Method (20pts) | Inheritance only (10pts) | None (5pts)
├─ Existing code changes for new features: Not needed (+5pts) | Minimal (+3pts) | Required (0pts)
├─ Interface usage: Appropriate (+5pts) | Partial (+3pts) | None (0pts)
└─ Example score: PaymentProcessor (Strategy) = 20 points

L - Liskov Substitution (20 points)
├─ Derived class contract compliance: Complete (20pts) | Partial (10pts) | Violated (0pts)
├─ Precondition strengthening: None (+5pts) | Present (-5pts)
├─ Postcondition weakening: None (+5pts) | Present (-5pts)
└─ Example score: Square extends Rectangle = 0 points (violated)

I - Interface Segregation (20 points)
├─ Interface size: 1-3 methods (20pts) | 4-7 (15pts) | 8+ (5pts)
├─ Unused method implementations: None (+5pts) | 1-2 (+2pts) | 3+ (0pts)
├─ Role clarity: Single role (+5pts) | Multiple roles (0pts)
└─ Example score: Readable/Writable separation = 20 points

D - Dependency Inversion (20 points)
├─ Dependency direction: Abstractions only (20pts) | Mixed (10pts) | Concretions only (5pts)
├─ DI usage: Constructor Injection (+5pts) | Setter (+3pts) | None (0pts)
├─ Testability: Mockable (+5pts) | Difficult (0pts)
└─ Example score: Repository Pattern = 20 points

Total Score = S + O + L + I + D
├─ 90-100 points: Excellent (SOLID compliant)
├─ 70-89 points: Good (Minor improvements needed)
├─ 50-69 points: Fair (Refactoring recommended)
├─ 30-49 points: Poor (Major improvements required)
└─ 0-29 points: Critical (Design overhaul required)

Technical Debt Quantification

Debt Calculation Formula

Technical Debt (time) = Complexity Score × Impact Range × Fix Difficulty

Complexity Score:
├─ Cyclomatic complexity: 1-5 (low) | 6-10 (med) | 11-20 (high) | 21+ (critical)
├─ Cognitive complexity: Nesting depth × conditional branches
├─ Lines of code: <50 (1pt) | 50-200 (2pts) | 200-500 (3pts) | 500+ (5pts)
└─ Duplication rate: 0-10% (1pt) | 10-30% (2pts) | 30-50% (3pts) | 50%+ (5pts)

Impact Range:
├─ Dependent modules: Direct dependencies + Indirect × 0.5
├─ Usage frequency: API calls/day
├─ Business importance: Critical (×3) | High (×2) | Medium (×1) | Low (×0.5)
└─ Team knowledge: 1 person knows (×3) | 2-3 (×2) | 4+ (×1)

Fix Difficulty:
├─ Test coverage: 0% (×3) | <50% (×2) | 50-80% (×1.5) | >80% (×1)
├─ Documentation: None (×2) | Insufficient (×1.5) | Adequate (×1)
├─ Dependencies: Tightly coupled (×3) | Moderate (×2) | Loosely coupled (×1)
└─ Change risk: Breaking change (×3) | Backward compatibility (×2) | Safe (×1)

Cost Conversion:
├─ Time cost: Debt time × Developer hourly rate
├─ Opportunity cost: New feature delay days × Daily revenue impact
├─ Quality cost: Bug probability × Fix cost × Frequency
└─ Total cost: Time + Opportunity + Quality costs

Priority Matrix

| Priority | Impact | Fix Cost | Time Savings | Investment ROI | Response Deadline | | -------------------------- | ------ | -------- | ------------ | --------------------- | ----------------- | | **Critical (Immediate)** | High | Low | > 5x | Invest 1h → Save 5h+ | Immediately | | **Important (Planned)** | High | High | 2-5x | Invest 1h → Save 2-5h | Within 1 month | | **Watch (Monitor)** | Low | High | 1-2x | Invest 1h → Save 1-2h | Within 3 months | | **Acceptable (Tolerable)** | Low | Low | < 1x | Investment = Savings | No action needed |

Refactoring Process

1. **Current Analysis and Measurement**

• Measure c