[refactor] Semantic Function Clustering Analysis - Code Organization Improvements

[github-actions]

Analysis performed on: 2026-02-14
Repository: github/gh-aw-mcpg
Commit: 039a262 (Refactor: Extract marshalToResponse helper)
Files analyzed: 67 non-test Go files
Functions cataloged: 450+ functions and methods

---

Executive Summary

This comprehensive semantic function clustering analysis examined all non-test Go source files to identify refactoring opportunities. The codebase demonstrates strong organization with clear package boundaries and well-structured code. Analysis identified 4 medium-priority refactoring opportunities for improved code organization through function consolidation, naming consistency, and reduced duplication.

Key Findings:

• ✅ Well-organized packages - Clear separation of concerns across 16 packages
• ⚠️ 4 medium-priority refactoring opportunities identified
• ⚠️ Function naming inconsistencies in validation error constructors
• ⚠️ Truncate function duplication across 2 packages with different implementations
• ⚠️ Validation logic scattered across 3 files (1,080 lines total)
• ✅ Excellent logging infrastructure - Well-organized across 14 files
• ✅ Strong DIFC implementation - Well-structured security model
• ✅ No critical refactoring needs - Code is appropriately structured

---

Package Inventory

Analysis by Package (16 packages, 67 files, 450+ functions/methods)

Package	Files	Functions	Primary Purpose
auth	1	5	Authentication header parsing
cmd	7	40+	CLI commands (Cobra framework)
config	8	50+	Configuration parsing & validation
difc	5	60+	Data flow security control
envutil	1	3	Environment utilities
guard	4	15+	Security guards
launcher	3	20+	Backend process management
logger	14	70+	Multi-format logging system
mcp	2	32+	MCP protocol implementation
middleware	1	6+	HTTP middleware (jq schema)
server	10	60+	HTTP server & routing
sys	1	6+	System server for introspection
testutil	4	25+	Test utilities
timeutil	1	1	Time formatting
tty	2	3	Terminal detection
version	1	2	Version management

Statistics:

• Total packages: 16
• Total files: 67 non-test Go files
• Total functions: 450+ standalone functions and methods

---

Identified Refactoring Opportunities

Priority 1: Function Naming Consistency 🔧

Issue: Validation Error Constructor Functions Don't Follow Go Conventions

Problem: Error constructor functions in internal/config/rules/rules.go don't follow standard Go naming conventions for constructors. Go idiom is to prefix constructor functions with New.

Current naming (inconsistent with Go conventions):

// config/rules/rules.go - current names
func UnsupportedType(fieldName, actualType, jsonPath, suggestion string) *ValidationError
func UndefinedVariable(varName, jsonPath string) *ValidationError
func MissingRequired(fieldName, serverType, jsonPath, suggestion string) *ValidationError
func UnsupportedField(fieldName, message, jsonPath, suggestion string) *ValidationError
func PortRange(port int, jsonPath string) *ValidationError
func TimeoutPositive(timeout int, fieldName, jsonPath string) *ValidationError
func MountFormat(mount, jsonPath string, index int) *ValidationError
func NonEmptyString(value, fieldName, jsonPath string) *ValidationError
func AbsolutePath(value, fieldName, jsonPath string) *ValidationError

Issue: These functions construct *ValidationError instances but don't use the New* prefix, making it unclear they are constructors.

Recommendation: Rename to follow Go New*Error convention:

// Better: Clear that these are error constructors
func NewUnsupportedTypeError(fieldName, actualType, jsonPath, suggestion string) *ValidationError
func NewUndefinedVariableError(varName, jsonPath string) *ValidationError
func NewMissingRequiredError(fieldName, serverType, jsonPath, suggestion string) *ValidationError
func NewUnsupportedFieldError(fieldName, message, jsonPath, suggestion string) *ValidationError
func NewPortRangeError(port int, jsonPath string) *ValidationError
func NewTimeoutPositiveError(timeout int, fieldName, jsonPath string) *ValidationError
func NewMountFormatError(mount, jsonPath string, index int) *ValidationError
func NewNonEmptyStringError(value, fieldName, jsonPath string) *ValidationError
func NewAbsolutePathError(value, fieldName, jsonPath string) *ValidationError

Benefits:

• Clear that functions are constructors (Go idiom: New* prefix)
• Consistent with other constructor patterns in codebase (28 other New* functions)
• Better IDE autocomplete grouping
• Easier to distinguish from validation functions vs error creation

Call sites to update: ~25-30 locations in validation files

Estimated effort: 1-2 hours (rename + update call sites)
Impact: High - Improves code clarity and follows Go conventions

---

Priority 2: Duplicate Truncate Functions 🔧

Issue: Two Different String Truncation Implementations

Problem: Two truncate functions with different behaviors exist in separate packages for similar purposes.

Evidence:

// internal/auth/header.go:172-180
func TruncateSessionID(sessionID string) string {
    if sessionID == "" {
        return "(none)"
    }
    if len(sessionID) <= 8 {
        return sessionID
    }
    return sessionID[:8] + "..."
}

// internal/logger/sanitize/sanitize.go:75-82
func TruncateSecret(input string) string {
    if len(input) > 4 {
        return input[:4] + "..."
    } else if len(input) > 0 {
        return "..."
    }
    return ""
}

Differences:

• TruncateSessionID: Truncates to 8 chars, returns "(none)" for empty
• TruncateSecret: Truncates to 4 chars, returns "" for empty
• Both do string truncation with "..." suffix
• Different truncation lengths and empty-string handling

Recommendation: Create unified truncation utility with configurable behavior:

// internal/logger/sanitize/sanitize.go (or new internal/stringutil/)
// TruncateString truncates a string to maxLen characters with optional suffix
func TruncateString(s string, maxLen int, suffix string, emptyValue string) string {
    if s == "" {
        return emptyValue
    }
    if len(s) <= maxLen {
        return s
    }
    return s[:maxLen] + suffix
}

// Keep existing functions as convenience wrappers
func TruncateSecret(input string) string {
    return TruncateString(input, 4, "...", "")
}

// Move TruncateSessionID from auth/header.go to sanitize/
func TruncateSessionID(sessionID string) string {
    return TruncateString(sessionID, 8, "...", "(none)")
}
``````

**Benefits**:
- Single source of truth for truncation logic
- Easier to test and maintain
- Consistent behavior across codebase
- Flexible for future use cases
- Better location: `sanitize` package handles all sensitive data truncation

**Files to update**:
- `internal/logger/sanitize/sanitize.go` - Add unified function
- `internal/auth/header.go` - Remove `TruncateSessionID`, import from sanitize
- Update any imports

**Estimated effort**: 1 hour  
**Impact**: Medium - Reduces code duplication, improves maintainability

---

### Priority 3: Validation Logic Organization ⚠️

#### Issue: Config Validation Split Across 3 Large Files

**Problem**: Configuration validation logic is distributed across multiple files totaling 1,080 lines without clear separation of concerns.

**Current structure**:
``````
internal/config/
├── validation.go (272 lines, 10+ functions)
│   ├── expandVariables()
│   ├── validateMounts()
│   ├── validateServerConfig()
│   ├── validateStandardServerConfig()
│   └── ... 6+ more functions
├── validation_env.go (338 lines, 15+ functions)
│   ├── ValidateExecutionEnvironment()
│   ├── ValidateContainerizedEnvironment()
│   ├── expandEnvVariables()
│   └── ... 12+ more functions
└── validation_schema.go (470 lines, 7+ functions)
    ├── validateJSONSchema()
    ├── formatValidationErrorRecursive()
    └── ... 5+ more functions

Analysis:

• 32+ validation functions across 3 files (~1,080 lines)
• Not immediately clear why functions are split this way
• Some overlap in responsibilities (e.g., environment variable expansion in multiple files)

Recommendation Options:

Option A: Keep current structure but add clear documentation ✅ (Recommended)

• Add package-level doc comments explaining the split
• Add file-level comments describing each file's scope
• This is the lowest-risk option that improves clarity

// validation.go
// Package config provides configuration validation.
// This file handles core server configuration validation including
// server types, ports, timeouts, and mounts.

// validation_env.go
// Environment-specific validation for containerized and non-containerized
// execution environments, Docker accessibility checks, and runtime requirements.

// validation_schema.go
// JSON schema validation using the official MCP Gateway schema.
// Handles schema fetching, validation, and error formatting.
``````

**Option B: Better separation by responsibility**
``````
internal/config/
├── validation_config.go - Config structure validation (current validation.go)
├── validation_environment.go - Environment-specific checks (current validation_env.go)
└── validation_schema.go - JSON schema validation (keep as-is)

Option C: Consolidate into single file

• Higher risk, may make file too large (1,080+ lines)
• Not recommended unless there's clear overlap

Benefits:

• Clearer code organization
• Easier to find validation functions
• Reduced cognitive load when working with validation
• Better understanding of validation architecture

Estimated effort: 30 minutes (Option A), 2-3 hours (Option B)
Impact: Medium - Improves code navigation and organization

---

Priority 4: Logger Close() Pattern ⚠️

Issue: 5 Logger Types with Similar Close() Methods

Problem: Each logger type implements nearly identical Close() methods with mutex handling. This creates ~150 lines of boilerplate code.

Evidence - Pattern repeated across 5 types:

// Pattern repeated in:
// - file_logger.go:63-74
// - jsonl_logger.go:69-80
// - markdown_logger.go:73-84
// - server_file_logger.go:128-139
// - tools_logger.go (similar pattern)

func (fl *FileLogger) Close() error {
    fl.mu.Lock()
    defer fl.mu.Unlock()
    if fl.file != nil {
        if err := fl.file.Close(); err != nil {
            return fmt.Errorf("failed to close log file: %w", err)
        }
        fl.file = nil
    }
    return nil
}

Current implementation: ~150 lines of repeated boilerplate

Note: The codebase already has:

• ✅ Centralized initialization via global_helpers.go
• ✅ Shared closeLogFile() helper (used in some places)
• ⚠️ Close() methods still duplicated across types

Recommendation Options:

Option A: Use existing closeLogFile helper consistently

// Already exists in common.go - use it more widely
func closeLogFile(file *os.File, mu *sync.Mutex, loggerName string) error

Option B: Extract common Close logic with interface (More comprehensive)

// internal/logger/common.go
type ClosableLogger struct {
    mu   sync.RWMutex
    file *os.File
}

func (cl *ClosableLogger) Close() error {
    cl.mu.Lock()
    defer cl.mu.Unlock()
    if cl.file != nil {
        if err := cl.file.Close(); err != nil {
            return fmt.Errorf("failed to close log file: %w", err)
        }
        cl.file = nil
    }
    return nil
}

// Each logger embeds ClosableLogger
type FileLogger struct {
    ClosableLogger
    // ... other fields
}
``````

**Option C: Keep as-is** (Acceptable)
- Pattern is simple and clear
- Type-specific implementations allow for future customization
- Minor duplication may be acceptable for clarity

**Benefits** (if refactored):
- Reduce ~150 lines of boilerplate code
- Centralize resource cleanup patterns
- Easier to add new logger types
- Consistent with existing `global_helpers.go` pattern

**Estimated effort**: 2-3 hours  
**Impact**: Low-Medium - Optional improvement, current code works well

---

## Patterns That Are Correctly Implemented ✅

### Pattern 1: Domain-Specific Logging Helpers (Correct Placement)

**Observation**: Logging-related helper functions exist in domain packages (launcher, server) rather than in the logger package.

**Analysis**: ✅ **This is correct** - These are domain-specific helpers that wrap logger calls with business logic:
- `launcher/log_helpers.go` - Launch-specific logging (7 functions)
- `server/` package - HTTP-specific logging (4 functions)

These belong in their domain packages, not in the logger package. Moving them would create inappropriate dependencies.

**Recommendation**: ✅ **No action needed**

---

### Pattern 2: Validation Functions Well-Distributed by Domain (Correct)

**Observation**: Validation functions correctly distributed by responsibility:
- **auth package**: `ValidateAPIKey()` - Auth validation
- **config package**: 32+ functions - Configuration validation
- **server package**: `extractAndValidateSession()` - HTTP session validation
- **difc package**: Security label validation

**Analysis**: ✅ **Excellent organization** - Each package validates its own domain

**Recommendation**: ✅ **No action needed**

---

### Pattern 3: Sanitization Properly Centralized (Excellent Practice)

**Observation**: Security-critical sanitization centralized in `internal/logger/sanitize/`

**Functions**:
- `SanitizeString()` - Full string/payload sanitization
- `SanitizeJSON()` - JSON data sanitization
- `TruncateSecret()` - Sensitive value truncation
- `TruncateSecretMap()` - Environment variable sanitization
- `SanitizeArgs()` - Docker command args sanitization

**Analysis**: ✅ **Model security practice** - All sanitization logic auditable in one location

**Recommendation**: ✅ **No action needed** - Exemplary implementation

---

### Pattern 4: Config Package File Organization (Excellent)

**Structure**:
``````
internal/config/
├── config_core.go - TOML file loading
├── config_feature.go - Feature flags
├── config_payload.go - Payload configuration
├── config_stdin.go - JSON stdin parsing
├── rules/rules.go - Validation error types
├── validation.go - Core validation
├── validation_env.go - Environment validation
└── validation_schema.go - Schema validation

Analysis: ✅ Excellent separation:

• Core vs feature config clearly separated
• File vs stdin loading in dedicated files
• Validation organized by type
• Reusable error types abstracted into subpackage

Recommendation: ✅ No action needed - Model to follow

---

Pattern 5: Constructor Pattern Usage (Excellent)

Observation: 28 New* constructor functions consistently used across packages

Examples:

• launcher.New(), logger.New(), server.NewUnified()
• difc.NewLabel(), guard.NewRegistry(), mcp.NewConnection()

Analysis: ✅ Proper Go idiom - Consistent constructor pattern

Note: This makes Priority 1 (validation error constructors) more important - they should follow the same pattern!

Recommendation: ✅ Pattern is correct - Extend to validation errors

---

Function Pattern Analysis

Pattern Distribution

Pattern	Count	Assessment
Constructor (New*)	28	✅ Properly implemented
Registration (Register*)	8	✅ Correctly used
Cleanup (Close*)	15	✅ Each package manages resources
Validation (Validate*)	20+	✅ Well-distributed by domain
Sanitization (Sanitize*)	5	✅ Centralized in sanitize package
Extraction (Extract*)	4	✅ Appropriate locations
Parsing (Parse*)	2	✅ Clear purpose

---

Duplicate Detection Results

Methodology: Analyzed all 450+ functions/methods for:

• Exact name matches across files
• Similar code patterns and logic
• Semantic equivalence across packages

Results: ✅ Minimal duplicates found

Acceptable Function Name Collisions:

• Close() methods on different types (15 occurrences) - ✅ Expected for io.Closer pattern
• Error() methods on error types (3+ occurrences) - ✅ Required for error interface
• New() constructors (8 occurrences) - ✅ Standard Go constructor pattern

Identified Duplicates (covered in Priority 2):

• TruncateSessionID() vs TruncateSecret() - Similar implementations, different parameters

Analysis: The lack of significant duplicates indicates:

• ✅ Good code reuse practices
• ✅ Minimal copy-paste programming
• ✅ Appropriate abstraction levels

---

Recommendations Summary

Phase 1: High Impact (2-3 hours total)

1. ✅ Rename Validation Error Constructors (config/rules/)

   • Change UnsupportedType() → NewUnsupportedTypeError()
   • Apply to 9 constructor functions
   • Benefit: Follows Go conventions, consistent with 28 other constructors
   • Effort: 1-2 hours

2. ✅ Consolidate Truncate Functions (auth/, logger/sanitize/)

   • Create unified TruncateString() utility
   • Move TruncateSessionID to sanitize package
   • Keep existing as convenience wrappers
   • Benefit: Single source of truth, easier to maintain
   • Effort: 1 hour

Phase 2: Medium Improvements (30 min - 3 hours)

3. ✅ Document Validation File Organization (config/) - Low risk ✨
   • Add clear package and file-level documentation
   • Explain 3-file split rationale
   • Benefit: Easier navigation, clearer architecture
   • Effort: 30 minutes
   • Note: Can optionally rename files for clarity (2-3 hours)

Phase 3: Optional Enhancements (2-3 hours, low priority)

4. ⚠️ Logger Close() Pattern (logger/) - Optional
   • Consider using existing closeLogFile helper more consistently
   • OR extract common Close() logic with embedded struct
   • Current implementation is acceptable
   • Benefit: Reduce ~150 lines of boilerplate
   • Effort: 2-3 hours
   • Note: May not be worth the effort given current code works well

---

Implementation Checklist

Phase 1: Quick Wins (2-3 hours)

• Rename error constructor functions in config/rules/rules.go to New*Error() pattern
• Update call sites (25-30 locations in validation*.go files)
• Create unified TruncateString() utility in logger/sanitize/sanitize.go
• Move TruncateSessionID() from auth/header.go to sanitize/sanitize.go
• Update imports and call sites
• Run tests: make test-all

Phase 2: Medium Improvements (30 min - 3 hours)

• Add package-level documentation to config/ explaining validation structure
• Add file-level comments to validation.go, validation_env.go, validation_schema.go
• Optional: Consider renaming validation.go → validation_config.go for clarity
• Update tests if needed

Phase 3: Optional Enhancements (2-3 hours, defer if time constrained)

• Evaluate logger Close() pattern - decide if refactoring needed
• Consider consolidating with existing closeLogFile helper
• Update tests and documentation

Final Steps

• Run full test suite: make test-all
• Run linter: make lint
• Run formatter: make format
• Update documentation if needed
• Code review with team

---

Analysis Metadata

• Detection Method: Semantic code analysis + pattern matching + manual review
• Packages Analyzed: 16 internal packages
• Files Analyzed: 67 non-test Go files
• Functions Cataloged: 450+ standalone functions and methods
• Patterns Identified: 10 major patterns (4 need attention, 6 well-implemented)
• Issues Found: 4 medium-priority refactoring opportunities
• Code Organization Quality: ✅ Strong with improvement opportunities
• Analysis Date: 2026-02-14

---

Conclusion

This codebase demonstrates strong organization with clear package boundaries, appropriate separation of concerns, and minimal code duplication. The analysis identified 4 medium-priority opportunities for improvement, primarily around:

1. Naming consistency (validation error constructors) - High value
2. Code deduplication (truncate functions) - Medium value
3. Documentation clarity (validation file organization) - Low effort, good value
4. Boilerplate reduction (logger Close methods) - Optional

Key Strengths:

• ✅ Clear package structure following Go best practices
• ✅ Domain-specific functions correctly placed in their packages
• ✅ Security-critical sanitization properly centralized
• ✅ Minimal code duplication (only 1 significant case identified)
• ✅ Consistent use of Go idioms (New*, Register*, Close patterns)
• ✅ Excellent separation of validation, configuration, and business logic
• ✅ Well-organized logging infrastructure with multiple formats
• ✅ Strong security model (DIFC) with clear abstractions

Overall Assessment: This analysis found no critical refactoring needs. The codebase is well-maintained and follows Go best practices. The identified opportunities represent incremental improvements rather than urgent technical debt.

Recommended Action:

• Phase 1 (2-3 hours): High-impact improvements in naming and deduplication
• Phase 2 (30 min - 3 hours): Documentation improvements for clarity
• Phase 3 (optional): Can be deferred or skipped based on team priorities

The most valuable improvements are Phase 1 - especially the validation error constructor renaming, which brings consistency with the rest of the codebase's 28 other New* constructors.

---

References:

• §22018341324 - This workflow run

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