chore(sonar): Phase 1 maintainability cleanup (~50 issues)

internal/api/admin_handlers.go

@@ -8,6 +8,8 @@ import (
 	"strconv"
 	"strings"
 	"time"
+
+	"github.com/RandomCodeSpace/otelcontext/internal/httpconst"
 )
 
 // handleGetStats handles GET /api/stats
@@ -18,7 +20,7 @@ func (s *Server) handleGetStats(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return
 	}
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 	_ = json.NewEncoder(w).Encode(stats)
 }
 
@@ -50,7 +52,7 @@ func (s *Server) handlePurge(w http.ResponseWriter, r *http.Request) {
 
 	slog.Info("Admin purge completed", "days", days, "logs_purged", logsDeleted, "traces_purged", tracesDeleted)
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 	_ = json.NewEncoder(w).Encode(map[string]any{
 		"logs_purged":   logsDeleted,
 		"traces_purged": tracesDeleted,
@@ -65,7 +67,7 @@ func (s *Server) handleVacuum(w http.ResponseWriter, _ *http.Request) {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return
 	}
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 	_ = json.NewEncoder(w).Encode(map[string]string{"status": "vacuumed"})
 }
 
@@ -110,7 +112,7 @@ func (s *Server) handleDropFTS(w http.ResponseWriter, r *http.Request) {
 	}
 	slog.Info("drop_fts completed", "elapsed_ms", elapsed.Milliseconds(), "reclaimed_bytes", reclaimed)
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 	_ = json.NewEncoder(w).Encode(map[string]any{
 		"reclaimed_bytes": reclaimed,
 		"elapsed_ms":      elapsed.Milliseconds(),

internal/api/log_handlers.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"github.com/RandomCodeSpace/otelcontext/internal/api/views"
+	"github.com/RandomCodeSpace/otelcontext/internal/httpconst"
 	"github.com/RandomCodeSpace/otelcontext/internal/realtime"
 	"github.com/RandomCodeSpace/otelcontext/internal/storage"
 )
@@ -67,7 +68,7 @@ func (s *Server) handleGetLogs(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 	_ = json.NewEncoder(w).Encode(map[string]any{
 		"data":  views.LogsFromModels(logs),
 		"total": total,
@@ -96,7 +97,7 @@ func (s *Server) handleGetLogContext(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 	_ = json.NewEncoder(w).Encode(views.LogsFromModels(logs))
 }
 
@@ -120,7 +121,7 @@ func (s *Server) handleGetLogInsight(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 	_ = json.NewEncoder(w).Encode(map[string]string{"insight": string(l.AIInsight)})
 }
 

internal/api/metrics_handlers.go

@@ -7,6 +7,7 @@ import (
 	"time"
 
 	"github.com/RandomCodeSpace/otelcontext/internal/api/views"
+	"github.com/RandomCodeSpace/otelcontext/internal/httpconst"
 )
 
 // handleGetTrafficMetrics handles GET /api/metrics/traffic
@@ -35,7 +36,7 @@ func (s *Server) handleGetTrafficMetrics(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 	_ = json.NewEncoder(w).Encode(points)
 }
 
@@ -64,7 +65,7 @@ func (s *Server) handleGetLatencyHeatmap(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 	_ = json.NewEncoder(w).Encode(points)
 }
 
@@ -94,7 +95,7 @@ func (s *Server) handleGetDashboardStats(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 	_ = json.NewEncoder(w).Encode(views.DashboardStatsFromModel(stats))
 }
 
@@ -121,7 +122,7 @@ func (s *Server) handleGetServiceMapMetrics(w http.ResponseWriter, r *http.Reque
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 	_ = json.NewEncoder(w).Encode(views.ServiceMapMetricsFromModel(metrics))
 }
 
@@ -149,7 +150,7 @@ func (s *Server) handleGetMetricBuckets(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 	_ = json.NewEncoder(w).Encode(views.MetricBucketsFromModels(buckets))
 }
 
@@ -164,7 +165,7 @@ func (s *Server) handleGetMetricNames(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 	_ = json.NewEncoder(w).Encode(names)
 }
 
@@ -186,6 +187,6 @@ func (s *Server) handleGetServices(w http.ResponseWriter, r *http.Request) {
 	if services == nil {
 		services = []string{}
 	}
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 	_ = json.NewEncoder(w).Encode(services)
 }

internal/graphrag/drain_test.go

@@ -147,7 +147,7 @@ func TestConcurrentMatchRaceFree(t *testing.T) {
 			defer wg.Done()
 			for i := 0; i < per; i++ {
 				line := fmt.Sprintf("worker %d processed request id=%d from 10.0.0.%d", wid, i, i%250)
-				if tpl := d.Match(line, ts); tpl == nil {
+				if d.Match(line, ts) == nil {
 					t.Errorf("nil template")
 					return
 				}

internal/httpconst/httpconst.go

@@ -0,0 +1,13 @@
+// Package httpconst centralises HTTP header names and content-type strings
+// shared by the API, MCP, and OTLP-HTTP handlers so the same literal isn't
+// duplicated across packages.
+package httpconst
+
+const (
+	// HeaderContentType is the canonical HTTP Content-Type header name.
+	HeaderContentType = "Content-Type"
+
+	// ContentTypeJSON is the application/json content type used by every JSON
+	// response on the API and MCP surface.
+	ContentTypeJSON = "application/json"
+)

internal/ingest/otlp_http.go

@@ -28,6 +28,11 @@ import (
 // downstream a chance to drain.
 const defaultRetryAfterSeconds = 1
 
+// headerContentType is the canonical HTTP Content-Type header name. Local
+// const so the OTLP-HTTP receiver compiles without pulling in a shared
+// helper for a one-line literal.
+const headerContentType = "Content-Type" //nolint:goconst // single literal; Sonar S1192 satisfied via const
+
 // withTenantFromHTTP attaches a tenant ID from the X-Tenant-ID header (if any)
 // to the request context before delegating to the gRPC Export methods.
 // Uses the shared storage.WithTenantContext helper so ingest and read paths
@@ -269,7 +274,7 @@ func (h *HTTPHandler) readBody(r *http.Request) ([]byte, error) {
 
 // unmarshal decodes the body based on Content-Type header.
 func (h *HTTPHandler) unmarshal(r *http.Request, body []byte, msg proto.Message) error {
-	ct := r.Header.Get("Content-Type")
+	ct := r.Header.Get(headerContentType)
 	switch ct {
 	case contentTypeProtobuf, "":
 		if err := proto.Unmarshal(body, msg); err != nil {
@@ -287,9 +292,9 @@ func (h *HTTPHandler) unmarshal(r *http.Request, body []byte, msg proto.Message)
 
 // writeResponse marshals and writes the OTLP response.
 func (h *HTTPHandler) writeResponse(w http.ResponseWriter, r *http.Request, msg proto.Message) {
-	ct := r.Header.Get("Content-Type")
+	ct := r.Header.Get(headerContentType)
 	if ct == contentTypeJSON {
-		w.Header().Set("Content-Type", contentTypeJSON)
+		w.Header().Set(headerContentType, contentTypeJSON)
 		data, err := protojson.Marshal(msg)
 		if err != nil {
 			writeOTLPError(w, http.StatusInternalServerError, "failed to marshal response")
@@ -298,7 +303,7 @@ func (h *HTTPHandler) writeResponse(w http.ResponseWriter, r *http.Request, msg
 		w.WriteHeader(http.StatusOK)
 		_, _ = w.Write(data)
 	} else {
-		w.Header().Set("Content-Type", contentTypeProtobuf)
+		w.Header().Set(headerContentType, contentTypeProtobuf)
 		data, err := proto.Marshal(msg)
 		if err != nil {
 			writeOTLPError(w, http.StatusInternalServerError, "failed to marshal response")
@@ -321,7 +326,7 @@ func writeOTLPError(w http.ResponseWriter, statusCode int, msg string) {
 		http.Error(w, msg, statusCode)
 		return
 	}
-	w.Header().Set("Content-Type", contentTypeProtobuf)
+	w.Header().Set(headerContentType, contentTypeProtobuf)
 	w.WriteHeader(statusCode)
 	_, _ = w.Write(data)
 }

internal/ingest/otlp_http_backpressure_test.go

@@ -130,7 +130,7 @@ func TestHTTPBackpressure_TracesReturns429WithRetryAfter(t *testing.T) {
 	if rec.Code != http.StatusTooManyRequests {
 		t.Fatalf("want 429, got %d (body=%q)", rec.Code, rec.Body.String())
 	}
-	if got := rec.Header().Get("Retry-After"); got == "" {
+	if rec.Header().Get("Retry-After") == "" {
 		t.Fatal("Retry-After header missing on 429 response")
 	}
 	if ct := rec.Header().Get("Content-Type"); ct != contentTypeProtobuf {

internal/mcp/server.go

@@ -14,6 +14,7 @@ import (
 	"github.com/RandomCodeSpace/central-ops/pkg/httputil"
 	"github.com/RandomCodeSpace/otelcontext/internal/graph"
 	"github.com/RandomCodeSpace/otelcontext/internal/graphrag"
+	"github.com/RandomCodeSpace/otelcontext/internal/httpconst"
 	"github.com/RandomCodeSpace/otelcontext/internal/storage"
 	"github.com/RandomCodeSpace/otelcontext/internal/telemetry"
 	"github.com/RandomCodeSpace/otelcontext/internal/vectordb"
@@ -209,7 +210,7 @@ func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 // handleRPC processes JSON-RPC 2.0 requests.
 func (s *Server) handleRPC(w http.ResponseWriter, r *http.Request) {
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 
 	body, err := io.ReadAll(io.LimitReader(r.Body, 1<<20)) // 1 MB cap
 	if err != nil {
@@ -321,7 +322,7 @@ func (s *Server) handleRPC(w http.ResponseWriter, r *http.Request) {
 	case "resources/list":
 		result = map[string]any{
 			"resources": []map[string]any{
-				{"uri": "OtelContext://system/graph", "name": "System Graph", "mimeType": "application/json"},
+				{"uri": "OtelContext://system/graph", "name": "System Graph", "mimeType": httpconst.ContentTypeJSON},
 				{"uri": "OtelContext://metrics/prometheus", "name": "Prometheus Metrics", "mimeType": "text/plain"},
 			},
 		}
@@ -406,7 +407,7 @@ func writeSSE(w http.ResponseWriter, f http.Flusher, event, data string) {
 
 // writeError writes a JSON-RPC error response.
 func writeError(w http.ResponseWriter, id any, code int, msg string) {
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(httpconst.HeaderContentType, httpconst.ContentTypeJSON)
 	resp := JSONRPCResponse{
 		JSONRPC: "2.0",
 		ID:      id,