[duplicate-code] Duplicate Code Pattern: HTTP Response Writer Wrappers

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🔍 Duplicate Code Pattern: HTTP Response Writer Wrappers

Part of duplicate code analysis: #375

Summary

Two nearly identical HTTP response writer wrapper implementations exist in the server package, differing only in field type (bytes.Buffer vs []byte). This duplication was introduced as part of the SDK logging changes in PR #372.

Duplication Details

Pattern: Response Writer Wrapper for Capturing Output

• Severity: Medium
• Occurrences: 2 instances
• Locations:
  • internal/server/sdk_logging.go (lines 40-54) - sdkLoggingResponseWriter
  • internal/server/transport.go (lines 52-66) - loggingResponseWriter

Code Comparison:

sdk_logging.go (uses bytes.Buffer):

type sdkLoggingResponseWriter struct {
    http.ResponseWriter
    body       bytes.Buffer
    statusCode int
}

func (w *sdkLoggingResponseWriter) WriteHeader(statusCode int) {
    w.statusCode = statusCode
    w.ResponseWriter.WriteHeader(statusCode)
}

func (w *sdkLoggingResponseWriter) Write(b []byte) (int, error) {
    w.body.Write(b)
    return w.ResponseWriter.Write(b)
}

transport.go (uses []byte):

type loggingResponseWriter struct {
    http.ResponseWriter
    body       []byte
    statusCode int
}

func (w *loggingResponseWriter) WriteHeader(statusCode int) {
    w.statusCode = statusCode
    w.ResponseWriter.WriteHeader(statusCode)
}

func (w *loggingResponseWriter) Write(b []byte) (int, error) {
    w.body = append(w.body, b...)
    return w.ResponseWriter.Write(b)
}

Key Difference: Only the body storage type differs (bytes.Buffer vs []byte with append)

Impact Analysis

• Maintainability: Changes to response capture logic need duplication across both types
• Bug Risk: Low - implementations are simple, but inconsistency could cause confusion
• Code Bloat: ~15 lines duplicated
• Testing: Requires separate tests for identical functionality

Refactoring Recommendations

1. Extract to Shared Middleware Utility (Recommended)

• Create internal/server/middleware.go with unified response writer:

  // responseCapturingWriter wraps http.ResponseWriter to capture response body
  type responseCapturingWriter struct {
      http.ResponseWriter
      body       *bytes.Buffer
      statusCode int
  }

• Location: internal/server/middleware.go (new file)
• Estimated effort: 1 hour
• Benefits:
  • Single implementation for all logging needs
  • Consistent behavior across different logging contexts
  • Easier to enhance (e.g., add size limits, compression)

2. Standardize on bytes.Buffer

• Use bytes.Buffer in both locations (more efficient for large responses)
• Update transport.go to match sdk_logging.go pattern
• Estimated effort: 15 minutes
• Benefits:
  • Quick fix
  • Better memory efficiency with Buffer API

3. Wrapper Factory Function

• Create factory: func newLoggingResponseWriter(w http.ResponseWriter) *loggingResponseWriter
• Consolidate initialization logic
• Estimated effort: 30 minutes

Implementation Checklist

• Create internal/server/middleware.go with shared response writer
• Add unit tests for response writer wrapper
• Update sdk_logging.go to use shared implementation
• Update transport.go to use shared implementation
• Remove duplicate type definitions
• Verify all logging functionality still works correctly
• Consider adding response size limits or streaming support

Parent Issue

See parent analysis report: #375
Related to #375

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