# Refactor

> Fowler/Martin Code Refactoring Best Practices

- Skill: `comeonoliver/refactor-2` (Agent Skill)
- Install (CLI): `npx skillmds@latest add comeonoliver/refactor-2`
- Raw SKILL.md: https://api.skillmd.com/api/skills/comeonoliver/refactor-2/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: ComeOnOliver (https://skillmd.com/u/comeonoliver)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/comeonoliver/refactor-2

---

# Fowler/Martin Code Refactoring Best Practices

Comprehensive code refactoring guide based on Martin Fowler's catalog and Clean Code principles, designed for AI agents and LLMs. Contains 43 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation.

## When to Apply

Reference these guidelines when:
- Refactoring existing code to improve maintainability
- Decomposing long methods or large classes
- Reducing coupling between components
- Simplifying complex conditional logic
- Reviewing code for code smells and anti-patterns

## Rule Categories by Priority

| Priority | Category | Impact | Prefix |
|----------|----------|--------|--------|
| 1 | Structure & Decomposition | CRITICAL | `struct-` |
| 2 | Coupling & Dependencies | CRITICAL | `couple-` |
| 3 | Naming & Clarity | HIGH | `name-` |
| 4 | Conditional Logic | HIGH | `cond-` |
| 5 | Abstraction & Patterns | MEDIUM-HIGH | `pattern-` |
| 6 | Data Organization | MEDIUM | `data-` |
| 7 | Error Handling | MEDIUM | `error-` |
| 8 | Micro-Refactoring | LOW | `micro-` |

## Quick Reference

### 1. Structure & Decomposition (CRITICAL)

- `struct-extract-method` - Extract Method for Long Functions
- `struct-single-responsibility` - Apply Single Responsibility Principle
- `struct-extract-class` - Extract Class from Large Class
- `struct-compose-method` - Compose Method for Readable Flow
- `struct-function-length` - Keep Functions Under 20 Lines
- `struct-replace-method-with-object` - Replace Method with Method Object
- `struct-parameter-object` - Introduce Parameter Object

### 2. Coupling & Dependencies (CRITICAL)

- `couple-dependency-injection` - Use Dependency Injection
- `couple-hide-delegate` - Hide Delegate to Reduce Coupling
- `couple-remove-middle-man` - Remove Middle Man When Excessive
- `couple-feature-envy` - Fix Feature Envy by Moving Methods
- `couple-interface-segregation` - Apply Interface Segregation Principle
- `couple-preserve-whole-object` - Preserve Whole Object Instead of Fields

### 3. Naming & Clarity (HIGH)

- `name-intention-revealing` - Use Intention-Revealing Names
- `name-avoid-abbreviations` - Avoid Abbreviations and Acronyms
- `name-consistent-vocabulary` - Use Consistent Vocabulary
- `name-searchable-names` - Use Searchable Names
- `name-avoid-encodings` - Avoid Type Encodings in Names

### 4. Conditional Logic (HIGH)

- `cond-guard-clauses` - Replace Nested Conditionals with Guard Clauses
- `cond-polymorphism` - Replace Conditional with Polymorphism
- `cond-decompose` - Decompose Complex Conditionals
- `cond-consolidate` - Consolidate Duplicate Conditional Fragments
- `cond-special-case` - Introduce Special Case Object
- `cond-lookup-table` - Replace Conditional with Lookup Table

### 5. Abstraction & Patterns (MEDIUM-HIGH)

- `pattern-strategy` - Extract Strategy for Algorithm Variants
- `pattern-template-method` - Use Template Method for Shared Skeleton
- `pattern-factory` - Use Factory for Complex Object Creation
- `pattern-open-closed` - Apply Open-Closed Principle
- `pattern-composition-over-inheritance` - Prefer Composition Over Inheritance
- `pattern-extract-superclass` - Extract Superclass for Common Behavior

### 6. Data Organization (MEDIUM)

- `data-encapsulate-collection` - Encapsulate Collection
- `data-replace-primitive` - Replace Primitive with Object
- `data-encapsulate-record` - Encapsulate Record into Class
- `data-split-variable` - Split Variable with Multiple Assignments
- `data-replace-temp-with-query` - Replace Temp with Query

### 7. Error Handling (MEDIUM)

- `error-exceptions-over-codes` - Use Exceptions Instead of Error Codes
- `error-custom-exceptions` - Create Domain-Specific Exception Types
- `error-fail-fast` - Fail Fast with Preconditions
- `error-separate-concerns` - Separate Error Handling from Business Logic

### 8. Micro-Refactoring (LOW)

- `micro-remove-dead-code` - Remove Dead Code
- `micro-inline-variable` - Inline Trivial Variables
- `micro-simplify-expressions` - Simplify Boolean Expressions
- `micro-rename-for-clarity` - Rename for Clarity

## How to Use

Read individual reference files for detailed explanations and code examples:

- [Section definitions](references/_sections.md) - Category structure and impact levels
- [Rule template](assets/templates/_template.md) - Template for adding new rules
- Individual rules: `references/{prefix}-{slug}.md`

## Full Compiled Document

For the complete guide with all rules expanded: `AGENTS.md`