refactor

Refactoring Skill

Usage

/refactor [target] [--type <refactoring>]

Parameters

• target: File, function, or directory
• --type: extract | rename | simplify | pattern | all

Examples

/refactor src/utils.ts
/refactor src/api/ --type extract
/refactor handleSubmit --type simplify
/refactor src/services/ --type pattern

Refactoring Types

Extract (--type extract)

Extract methods, classes, or modules:

// Before: Long function
function processOrder(order) {
  // validation (10 lines)
  // calculation (15 lines)
  // formatting (10 lines)
}

// After: Extracted functions
function processOrder(order) {
  validateOrder(order);
  const total = calculateTotal(order);
  return formatResult(total);
}

Rename (--type rename)

Improve naming clarity:

// Before
const d = new Date();
const fn = (x) => x * 2;
class Mgr {}

// After
const currentDate = new Date();
const doubleValue = (value) => value * 2;
class OrderManager {}

Simplify (--type simplify)

Reduce complexity:

// Before: Nested conditions
if (user) {
  if (user.isActive) {
    if (user.hasPermission) {
      return true;
    }
  }
}
return false;

// After: Guard clauses
if (!user) return false;
if (!user.isActive) return false;
if (!user.hasPermission) return false;
return true;

Pattern (--type pattern)

Apply design patterns:

// Before: Switch statement
function getDiscount(type) {
  switch (type) {
    case 'gold': return 0.2;
    case 'silver': return 0.1;
    default: return 0;
  }
}

// After: Strategy pattern
const discounts = {
  gold: { calculate: () => 0.2 },
  silver: { calculate: () => 0.1 },
  default: { calculate: () => 0 }
};

function getDiscount(type) {
  return (discounts[type] || discounts.default).calculate();
}

Workflow

Step 1: Analyze Target

# Find code smells
wc -l {file}  # Long files
Grep: "if.*if.*if|for.*for"  # Deep nesting
Grep: "TODO|FIXME|HACK"  # Technical debt markers

Step 2: Identify Opportunities

Step 3: Plan Changes

## Refactoring Plan

### Target: src/orderService.ts

### Issues Found
1. `processOrder` is 85 lines (should be <20)
2. Duplicate validation in 3 methods
3. Deep nesting in `calculateDiscount`

### Proposed Changes
1. Extract `validateOrder()`, `calculateTotals()`, `applyDiscounts()`
2. Create `ValidationService` for shared validation
3. Use guard clauses in `calculateDiscount`

### Execution Order
1. Add tests for current behavior
2. Extract methods (preserving behavior)
3. Run tests after each change
4. Commit incrementally

Step 4: Execute Safely

1. Verify tests exist
2. Make one change
3. Run tests
4. Commit
5. Repeat

Safety Checklist

Before refactoring:

• Tests exist for target code
• All tests pass
• Code is committed

After each change:

• Tests still pass
• Behavior unchanged
• Code compiles

After completion:

• All tests pass
• Code review complete
• Changes committed

Output Format

## Refactoring Report

### Target
`src/services/orderService.ts`

### Changes Made
| Line | Before | After |
|------|--------|-------|
| 45-85 | processOrder (40 lines) | processOrder (10 lines) + 3 helpers |

### New Functions
- `validateOrder(order)` - Validation logic
- `calculateTotals(items)` - Total calculation
- `applyDiscounts(total, customer)` - Discount logic

### Metrics
| Metric | Before | After |
|--------|--------|-------|
| Lines | 85 | 45 |
| Complexity | 12 | 4 |
| Functions | 1 | 4 |

### Tests
All 15 tests passing

Common Refactorings