feat: add preview channels endpoint

agent/internal/httpapi/preview.go

@@ -0,0 +1,58 @@
+package httpapi
+
+import (
+	"encoding/json"
+	"net/http"
+	"strconv"
+)
+
+type previewChannel struct {
+	Name   string `json:"name"`
+	HlsURL string `json:"hls_url,omitempty"`
+}
+
+// handlePreviewChannels returns available video preview channels.
+// GET /v1/preview/channels
+func (s *Server) handlePreviewChannels(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodGet {
+		errorJSON(w, http.StatusMethodNotAllowed, "method not allowed")
+		return
+	}
+	if !s.authorize(r, false) {
+		errorJSON(w, http.StatusUnauthorized, "unauthorized")
+		return
+	}
+
+	channels := s.discoverChannels(r)
+	if channels == nil {
+		channels = make([]previewChannel, 0)
+	}
+	writeJSON(w, http.StatusOK, map[string]any{"channels": channels})
+}
+
+func (s *Server) discoverChannels(r *http.Request) []previewChannel {
+	if s.ms == nil {
+		return nil
+	}
+	_, body, err := s.ms.GetGraphs(r.Context())
+	if err != nil {
+		return nil
+	}
+
+	var graphs []struct {
+		Name string `json:"name"`
+	}
+	if err := json.Unmarshal(body, &graphs); err != nil {
+		return nil
+	}
+
+	baseURL := "http://" + s.hostname + ":" + strconv.Itoa(s.mediaPort)
+	var channels []previewChannel
+	for _, g := range graphs {
+		channels = append(channels, previewChannel{
+			Name:   g.Name,
+			HlsURL: baseURL + "/hls/" + g.Name + "/index.m3u8",
+		})
+	}
+	return channels
+}

agent/internal/httpapi/server.go

@@ -134,6 +134,7 @@ func New(agentCfg config.AgentConfig, baseDir string, ms *mediaserver.Client, st
 	mux.HandleFunc("/v1/face-gallery/reload", s.handleFaceGalleryReload)
 	mux.HandleFunc("/v1/alarms/report", s.handleAlarmReport)
 	mux.HandleFunc("/v1/alarms/recent", s.handleAlarmsRecent)
+	mux.HandleFunc("/v1/preview/channels", s.handlePreviewChannels)
 	mux.HandleFunc("/v1/resources/status", s.handleResourcesStatus)
 	mux.HandleFunc("/v1/resources/", s.handleResourceUpload)
 	mux.HandleFunc("/v1/models", s.handleModelsList)