feat: expose dry-run summary via control api

docs/README.md

@@ -23,6 +23,8 @@
 The dry-run mode generates a synthetic, hardware-free frame summary based on the current config.
 It is intended as a no-hardware smoke path for the CLI and config/control-adjacent logic.
 
+The HTTP control plane also exposes `GET /dry-run` for quick inspection of the currently effective no-hardware summary.
+
 ## Offline generation
 
 `cmd/offline` generates a deterministic no-hardware IQ/composite-style file using the repository's output backend path.

internal/control/control.go

@@ -3,11 +3,14 @@ package control
 import (
     "encoding/json"
     "net/http"
+    "sync"
 
     "github.com/jan/fm-rds-tx/internal/config"
+    drypkg "github.com/jan/fm-rds-tx/internal/dryrun"
 )
 
 type Server struct {
+    mu  sync.RWMutex
     cfg config.Config
 }
 
@@ -17,6 +20,7 @@ func (s *Server) Handler() http.Handler {
     mux := http.NewServeMux()
     mux.HandleFunc("/healthz", s.handleHealth)
     mux.HandleFunc("/status", s.handleStatus)
+    mux.HandleFunc("/dry-run", s.handleDryRun)
     return mux
 }
 
@@ -26,12 +30,25 @@ func (s *Server) handleHealth(w http.ResponseWriter, _ *http.Request) {
 }
 
 func (s *Server) handleStatus(w http.ResponseWriter, _ *http.Request) {
+    s.mu.RLock()
+    cfg := s.cfg
+    s.mu.RUnlock()
+
     w.Header().Set("Content-Type", "application/json")
     _ = json.NewEncoder(w).Encode(map[string]any{
         "service": "fm-rds-tx",
-        "backend": s.cfg.Backend.Kind,
-        "frequencyMHz": s.cfg.FM.FrequencyMHz,
-        "stereoEnabled": s.cfg.FM.StereoEnabled,
-        "rdsEnabled": s.cfg.RDS.Enabled,
+        "backend": cfg.Backend.Kind,
+        "frequencyMHz": cfg.FM.FrequencyMHz,
+        "stereoEnabled": cfg.FM.StereoEnabled,
+        "rdsEnabled": cfg.RDS.Enabled,
     })
 }
+
+func (s *Server) handleDryRun(w http.ResponseWriter, _ *http.Request) {
+    s.mu.RLock()
+    cfg := s.cfg
+    s.mu.RUnlock()
+
+    w.Header().Set("Content-Type", "application/json")
+    _ = json.NewEncoder(w).Encode(drypkg.Generate(cfg))
+}

internal/control/control_test.go

@@ -35,3 +35,20 @@ func TestStatus(t *testing.T) {
         t.Fatalf("unexpected service: %v", body["service"])
     }
 }
+
+func TestDryRunEndpoint(t *testing.T) {
+    srv := NewServer(cfgpkg.Default())
+    req := httptest.NewRequest(http.MethodGet, "/dry-run", nil)
+    rec := httptest.NewRecorder()
+    srv.Handler().ServeHTTP(rec, req)
+    if rec.Code != http.StatusOK {
+        t.Fatalf("unexpected status: %d", rec.Code)
+    }
+    var body map[string]any
+    if err := json.Unmarshal(rec.Body.Bytes(), &body); err != nil {
+        t.Fatalf("decode body: %v", err)
+    }
+    if body["mode"] != "dry-run" {
+        t.Fatalf("unexpected mode: %v", body["mode"])
+    }
+}