feat: play cached TTS audio immediately on auto-start if already generated

scraper/internal/server/server.go

@@ -134,6 +134,8 @@ func (s *Server) ListenAndServe(ctx context.Context) error {
 		`{"error":"audio generation timed out"}`,
 	)
 	mux.Handle("POST /ui/audio/{slug}/{n}", audioGenHandler)
+	// Status route: returns the proxy URL if audio was already generated, 404 otherwise.
+	mux.HandleFunc("GET /ui/audio/{slug}/{n}", s.handleAudioStatus)
 	// Proxy route: fetches the generated file from Kokoro /v1/download/{filename}.
 	mux.HandleFunc("GET /ui/audio-proxy/{slug}/{n}", s.handleAudioProxy)
 
@@ -355,6 +357,39 @@ func (s *Server) writeAudioResponse(w http.ResponseWriter, slug string, n int, v
 	})
 }
 
+// handleAudioStatus handles GET /ui/audio/{slug}/{n}.
+// Returns the proxy URL if audio was already generated this session, 404 otherwise.
+func (s *Server) handleAudioStatus(w http.ResponseWriter, r *http.Request) {
+	slug := r.PathValue("slug")
+	n, err := strconv.Atoi(r.PathValue("n"))
+	if err != nil || n < 1 {
+		http.Error(w, `{"error":"invalid chapter"}`, http.StatusBadRequest)
+		return
+	}
+	voice := r.URL.Query().Get("voice")
+	if voice == "" {
+		voice = s.kokoroVoice
+	}
+	speedStr := r.URL.Query().Get("speed")
+	speed := 1.0
+	if speedStr != "" {
+		if v, err := strconv.ParseFloat(speedStr, 64); err == nil && v > 0 {
+			speed = v
+		}
+	}
+
+	cacheKey := fmt.Sprintf("%s/%d/%s/%.2f", slug, n, voice, speed)
+	s.audioMu.Lock()
+	filename, ok := s.audioCache[cacheKey]
+	s.audioMu.Unlock()
+
+	if !ok {
+		http.Error(w, `{"error":"not generated"}`, http.StatusNotFound)
+		return
+	}
+	s.writeAudioResponse(w, slug, n, voice, speed, filename)
+}
+
 // handleAudioProxy handles GET /ui/audio-proxy/{slug}/{n}.
 // It looks up the Kokoro download filename for this chapter (voice/speed) and
 // proxies GET /v1/download/{filename} from the Kokoro server back to the browser.