Refactor

Analyze code and suggest refactoring opportunities with rationale. This is an analysis-only skill - it identifies and documents refactoring opportunities but does not execute them.

When to Use

• Reviewing code for improvement opportunities
• Planning a refactoring initiative
• Assessing technical debt in a codebase area
• Evaluating complexity, duplication, or coupling concerns
• Understanding blast radius before making changes

Input

• Target: file path, directory/package, or function/component name
• Optional: specific concern (duplication, complexity, coupling, testability, etc.)

Investigation Strategy

Track 1: Codebase Exploration

• Map dependencies and call sites for target code
• Identify blast radius of potential changes
• Find related code with similar patterns
• Assess test coverage of affected areas

Track 2: Code Analysis

• Deep analysis of code smells and patterns
• Identify refactoring opportunities
• Assess complexity metrics
• Evaluate maintainability concerns

Refactoring Patterns

Universal Patterns

Pattern	Description
Extract function/method	Pull out reusable logic
Inline function/variable	Remove unnecessary indirection
Rename	Improve clarity (with blast radius assessment)
Move	Relocate to better home (file, package, module)
Replace conditional with polymorphism	Simplify branching
Introduce parameter object	Group related parameters
Dependency inversion	Decouple via interfaces/abstractions

Go-Specific Patterns

Pattern	Description
Extract interface	Define behavior contracts
Consolidate error handling	Reduce repetitive error checks
Replace concrete with interface	Improve testability
Extract middleware	Separate cross-cutting concerns
Table-driven refactor	Convert repetitive code to data-driven

Frontend-Specific Patterns

Pattern	Description
Extract component	Break down large components
Extract custom hook	Reuse stateful logic
Lift state up	Move state to common ancestor
Push state down	Colocate state with usage
Extract render function	Simplify complex JSX
Memoization	Optimize re-renders

Output

Document the analysis using the template at references/templates/refactor-analysis.md.

The analysis should include:

• Code smells identified with locations
• Suggested refactorings with risk assessment
• Blast radius for each change
• Recommended order of operations
• Test coverage assessment

Constraints

• Analysis only: Do not execute refactorings - document recommendations
• Blast radius required: Every suggestion must include affected files/functions
• Risk assessment required: Every suggestion must be rated Low/Medium/High
• Order matters: Recommend sequence based on risk and dependencies
• Test awareness: Note test coverage and impact for each suggestion

Example

Refactoring Analysis: pkg/auth/handler.go

Target:
- Path: pkg/auth/handler.go
- Scope: file
- Concern: complexity

Summary:
The auth handler has grown to 450 lines with 3 code smells identified.
Recommend extracting token validation and session management into
separate services. Low-risk changes that improve testability.

Code Smells Identified:

1. Long Function (validateAndCreateSession)
   - Location: handler.go:145-280
   - Description: 135-line function handling validation, session
     creation, and response formatting
   - Impact: Hard to test, multiple responsibilities

2. Feature Envy (token validation)
   - Location: handler.go:156-198
   - Description: Handler reaches into token package internals
   - Impact: Tight coupling, changes ripple across packages

Suggested Refactorings:

1. Extract TokenValidator service
   - Type: Extract
   - Target: handler.go:156-198
   - Rationale: Encapsulates token validation logic
   - Blast Radius: handler.go, handler_test.go
   - Risk: Low — isolated logic, good test coverage
   - Test Impact: Add TokenValidator unit tests

2. Extract SessionManager service
   - Type: Extract
   - Target: handler.go:200-250
   - Rationale: Separates session concerns from HTTP handling
   - Blast Radius: handler.go, session.go, handler_test.go
   - Risk: Medium — touches session storage
   - Test Impact: Update integration tests

Recommended Order:
1. TokenValidator first (lowest risk, no dependencies)
2. SessionManager second (depends on cleaner handler)

Begin by identifying the target code and any specific concerns to focus on.