clashapi: Allow to update external UI from API

experimental/clashapi/api_meta.go

@@ -7,6 +7,7 @@ import (
 	"time"
 
 	"github.com/sagernet/sing-box/experimental/clashapi/trafficontrol"
+	E "github.com/sagernet/sing/common/exceptions"
 	"github.com/sagernet/sing/common/json"
 	"github.com/sagernet/ws"
 	"github.com/sagernet/ws/wsutil"
@@ -20,6 +21,7 @@ import (
 func (s *Server) setupMetaAPI(r chi.Router) {
 	r.Get("/memory", memory(s.trafficManager))
 	r.Mount("/group", groupRouter(s))
+	r.Post("/upgrade/ui", updateExternalUI(s))
 }
 
 type Memory struct {
@@ -77,3 +79,25 @@ func memory(trafficManager *trafficontrol.Manager) func(w http.ResponseWriter, r
 		}
 	}
 }
+
+func updateExternalUI(server *Server) func(w http.ResponseWriter, r *http.Request) {
+	return func(w http.ResponseWriter, r *http.Request) {
+		if server.externalUI == "" {
+			render.Status(r, http.StatusNotImplemented)
+			render.JSON(w, r, newError("not set external UI"))
+			return
+		}
+		err := server.downloadExternalUI()
+		if err != nil {
+			server.logger.Error(E.Cause(err, "download external ui"))
+			render.Status(r, http.StatusInternalServerError)
+			render.JSON(w, r, newError(err.Error()))
+			return
+		}
+		render.JSON(w, r, render.M{"status": "ok"})
+		if flusher, isFlusher := w.(http.Flusher); isFlusher {
+			flusher.Flush()
+		}
+		server.logger.Info("updated external UI")
+	}
+}

experimental/clashapi/server.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"runtime"
 	"strings"
+	"sync"
 	"syscall"
 	"time"
 
@@ -57,6 +58,7 @@ type Server struct {
 	externalUI               string
 	externalUIDownloadURL    string
 	externalUIDownloadDetour string
+	externalUIAccess         sync.Mutex
 }
 
 func NewServer(ctx context.Context, logFactory log.ObservableFactory, options option.ClashAPIOptions) (adapter.ClashServer, error) {

experimental/clashapi/server_resources.go

@@ -37,6 +37,8 @@ func (s *Server) checkAndDownloadExternalUI() {
 }
 
 func (s *Server) downloadExternalUI() error {
+	s.externalUIAccess.Lock()
+	defer s.externalUIAccess.Unlock()
 	var downloadURL string
 	if s.externalUIDownloadURL != "" {
 		downloadURL = s.externalUIDownloadURL