[duplicate-code] Duplicate Code Pattern: Inline JSON Response Construction in proxy/handler.go

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Part of duplicate code analysis: #2300

Summary

The same 3-line JSON response construction block appears 4 times in internal/proxy/handler.go. A centralised writeJSONResponse helper already exists in internal/server/http_helpers.go but is not accessible to the proxy package. The proxy package duplicates this logic inline instead.

Duplication Details

Pattern: Inline JSON response headers + body encoding

• Severity: Medium

• Occurrences: 4 instances in the same file

• Locations:

  • internal/proxy/handler.go (lines 35–37) — health-check response
  • internal/proxy/handler.go (lines 69–71) — unknown GraphQL operation forbidden
  • internal/proxy/handler.go (lines 135–137) — write operation DIFC block
  • internal/proxy/handler.go (lines 214–216) — strict-mode collection block

• Existing helper (not used by proxy):

  • internal/server/http_helpers.go (lines 22–26) — writeJSONResponse(w, statusCode, body)

• Code Sample (each occurrence looks like this):

  w.Header().Set("Content-Type", "application/json")
  w.WriteHeader(http.StatusForbidden)
  json.NewEncoder(w).Encode(map[string]string{
      "message": "...",
  })

Impact Analysis

• Maintainability: Every future change to the response format (e.g., adding a requestId field, switching to json.Marshal + explicit w.Write) must be applied in 4 places instead of 1.
• Bug Risk: Content-Type header could be omitted or set to the wrong value in a future edit to any of the 4 sites.
• Code Bloat: ~12 lines that could be 4 single-line calls.

Refactoring Recommendations

1. Add a package-level helper to internal/proxy/

   • Create internal/proxy/http_helpers.go containing:

     func writeJSONResponse(w http.ResponseWriter, status int, body interface{}) {
         w.Header().Set("Content-Type", "application/json")
         w.WriteHeader(status)
         json.NewEncoder(w).Encode(body)
     }

   • Replace all 4 inline blocks in handler.go with calls to this helper.
   • Estimated effort: ~30 minutes
   • Benefits: single place to adjust response serialisation; consistent behaviour

2. Alternative: Extract to a shared internal/httputil package

   • If server/http_helpers.go's writeJSONResponse is needed by more packages in the future, move it to internal/httputil/ and import from both server and proxy.
   • More disruptive but more scalable.

Implementation Checklist

• Review the 4 duplication sites in internal/proxy/handler.go
• Create writeJSONResponse helper in proxy package (or shared package)
• Replace 4 inline blocks with helper calls
• Verify tests still pass (make test)
• Confirm no functionality broken

Parent Issue

See parent analysis report: #2300
Related to #2300

Generated by Duplicate Code Detector · ◷

• expires on Mar 29, 2026, 3:03 AM UTC