Refactor: Apply Clean Code principles to reduce duplication and complexity

[Copilot]

Apply Clean Code refactoring to improve maintainability without changing behavior. Eliminate code duplication, simplify control flow, and improve naming consistency.

Changes

Eliminate Duplication (DRY)

• Extract ResponseFactory for standardized API response maps (7 duplicate HashMap initializations → 1 reusable utility)
• Extract TokenExtractor for JWT parsing (duplicate split logic in JwtTokenFilter and CurrentUserApi → single source)
• Extract validatePaginationParams() in ArticleDatafetcher (5 identical validation blocks → 1 method)

Simplify Control Flow (KISS)

• Replace nested if-else with early returns in ArticleQueryService, ProfileApi, UsersApi
• Replace size() == 0 with isEmpty() throughout
• Extract guard clauses in authentication logic

Improve Naming

• Fix typo: followdUsers → followedUsers
• Replace generic names: optional → descriptive variable names
• Extract magic strings to constants: AUTHORIZATION_HEADER, PAGINATION_PARAM_ERROR, EMPTY_BIO

Example - Before/After

Before:

private Map<String, Object> userResponse(UserWithToken userWithToken) {
  return new HashMap<String, Object>() {{
    put("user", userWithToken);
  }};
}

After:

import static io.spring.api.ResponseFactory.userResponse;
// Method eliminated - use centralized factory

Impact

• 13 files refactored
• ~70 lines of duplication removed
• Reduced cyclomatic complexity across 10+ methods
• All tests passing, behavior preserved

Warning

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>Refactor this code</issue_title>
<issue_description>---
mode: "agent"
description: 'Improve application with Clean Code principles by applying direct modifications'

Objective

Analyze and directly refactor code to comply with Clean Code principles, improving readability, simplicity, consistency, and testability without modifying functional behavior.

As a [Role]

Senior Software Engineer specializing in:

• Software craftsmanship and SOLID principles
• Code review in agile environments and technical debt reduction
• Clean architecture and maintainable code structure
• Direct refactoring with behavior preservation expertise

Context

Existing code requiring improvement with:

• Clean Code principles violations (naming, responsibilities, etc.)
• Accumulated technical debt impacting maintainability
• Complex, duplicated, or poorly readable code
• Need for progressive improvement without functional regression
• Modern language standards not applied

Identified Problems

• Unclear naming: Poorly named variables, functions, and classes in source code
• Multiple responsibilities: Classes/methods violating SRP principle
• High cyclic complexity: Nested logic difficult to understand
• Code duplication: DRY principle violations within code files
• Lack of explicitness: Code requiring too many comments
• Non-isolated side effects: Impure functions difficult to test
• Inconsistent code style: Mixed formatting and conventions in source files

Refactoring Objective

• Apply Clean Code: Clear naming, single responsibility, simplicity
• Reduce complexity: Decompose complex blocks
• Eliminate duplication: Factor out redundant code
• Improve testability: Isolate side effects
• Maintain consistency: Uniform standards and conventions

Technical Constraints

• Code files only: Refactor exclusively source code files (.js, .ts, .py, .java, .cs, etc.)
• No documentation changes: Do not modify README, comments, or documentation files
• No configuration files: Avoid changing package.json, config files, or build scripts
• Preserve behavior: No functional regression
• Maintain API: Public interface compatibility
• Progressive approach: One refactoring at a time
• Modern standards: Align with language best practices

Expected Output

1. Initial analysis:

   • Identification of code smells and Clean Code violations in source files only
   • Prioritization of modifications by impact/ease within code boundaries

2. Applied refactorings:

   • Direct source code file modifications step by step
   • Documentation of applied Clean Code principle for each code change
   • Behavior preservation validation through code analysis

3. Improvement summary:

   • List of code modifications performed (exclude documentation/config changes)
   • Code quality metrics improvement (if measurable)
   • Recommendations for next code refactoring steps

Style and Best Practices

• KISS: Keep It Simple, Stupid - simplicity above all
• DRY: Don't Repeat Yourself - eliminate duplication
• SOLID: Object-oriented design principles
• Clean Code: Robert C. Martin - naming, functions, classes

Expected Response Format

1. Step N: [Code Modification Title]

   • Identified Problem: Detected code smell in source file
   • Applied Principle: Clean Code reference
   • Code Modification: Direct application to source code file only
   • Benefit: Code quality improvement achieved

2. Global Summary:

   • Code modifications applied with Clean Code references
   • Source code quality improvement metrics
   • Future code refactoring recommendations

Important: Focus exclusively on source code improvements. Do not suggest changes to:

• Documentation files (README.md, docs/, etc.)
• Configuration files (package.json, tsconfig.json, etc.)
• Build scripts or deployment files
• Test files (unless specifically analyzing test code quality)</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes gologic-ca/Workshop-dette-technique#9

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