updated time

main.go

@@ -11,6 +11,7 @@ import (
 	"strconv"
 	"strings"
 	"sync"
+	"time"
 )
 
 //go:embed static/*
@@ -19,6 +20,7 @@ var indexHTML embed.FS
 type store struct {
 	mu    sync.RWMutex
 	value int
+	updatedAt time.Time
 }
 
 func (s *store) get() int {
@@ -30,9 +32,16 @@ func (s *store) get() int {
 func (s *store) set(v int) {
 	s.mu.Lock()
 	s.value = v
+	s.updatedAt = time.Now()
 	s.mu.Unlock()
 }
 
+func (s *store) snapshot() (int, time.Time) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	return s.value, s.updatedAt
+}
+
 func main() {
 	secret := os.Getenv("WRITE_SECRET")
 	addr := os.Getenv("ADDR")
@@ -108,7 +117,12 @@ func (s *server) handleIndex(w http.ResponseWriter, r *http.Request) {
 	}
 
 	w.Header().Set("Content-Type", "text/html; charset=utf-8")
-	if err := page.Execute(w, map[string]any{"Watts": s.store.get()}); err != nil {
+	watts, updatedAt := s.store.snapshot()
+	updatedLabel := "not updated yet"
+	if !updatedAt.IsZero() {
+		updatedLabel = updatedAt.Format("02.01.2006 15:04:05")
+	}
+	if err := page.Execute(w, map[string]any{"Watts": watts, "UpdatedAt": updatedLabel}); err != nil {
 		http.Error(w, "render error", http.StatusInternalServerError)
 	}
 }