From f595057a0be7473ab058180b3f11abed6c71b920 Mon Sep 17 00:00:00 2001
From: Philippe Vaucher <Silex@users.noreply.github.com>
Date: Sat, 14 Jun 2025 00:08:34 +0200
Subject: [PATCH] [signal] Set flags from environment variables (#3972)

---
 signal/cmd/env.go | 35 +++++++++++++++++++++++++++++++++++
 signal/cmd/run.go |  1 +
 2 files changed, 36 insertions(+)
 create mode 100644 signal/cmd/env.go

diff --git a/signal/cmd/env.go b/signal/cmd/env.go
new file mode 100644
index 000000000..3c15ebe1f
--- /dev/null
+++ b/signal/cmd/env.go
@@ -0,0 +1,35 @@
+package cmd
+
+import (
+	"os"
+	"strings"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+	"github.com/spf13/pflag"
+)
+
+// setFlagsFromEnvVars reads and updates flag values from environment variables with prefix NB_
+func setFlagsFromEnvVars(cmd *cobra.Command) {
+	flags := cmd.PersistentFlags()
+	flags.VisitAll(func(f *pflag.Flag) {
+		newEnvVar := flagNameToEnvVar(f.Name, "NB_")
+		value, present := os.LookupEnv(newEnvVar)
+		if !present {
+			return
+		}
+
+		err := flags.Set(f.Name, value)
+		if err != nil {
+			log.Infof("unable to configure flag %s using variable %s, err: %v", f.Name, newEnvVar, err)
+		}
+	})
+}
+
+// flagNameToEnvVar converts flag name to environment var name adding a prefix,
+// replacing dashes and making all uppercase (e.g. setup-keys is converted to NB_SETUP_KEYS according to the input prefix)
+func flagNameToEnvVar(cmdFlag string, prefix string) string {
+	parsed := strings.ReplaceAll(cmdFlag, "-", "_")
+	upper := strings.ToUpper(parsed)
+	return prefix + upper
+}
diff --git a/signal/cmd/run.go b/signal/cmd/run.go
index 3a671a848..39bc8331f 100644
--- a/signal/cmd/run.go
+++ b/signal/cmd/run.go
@@ -303,4 +303,5 @@ func init() {
 	runCmd.Flags().StringVar(&signalLetsencryptDomain, "letsencrypt-domain", "", "a domain to issue Let's Encrypt certificate for. Enables TLS using Let's Encrypt. Will fetch and renew certificate, and run the server with TLS")
 	runCmd.Flags().StringVar(&signalCertFile, "cert-file", "", "Location of your SSL certificate. Can be used when you have an existing certificate and don't want a new certificate be generated automatically. If letsencrypt-domain is specified this property has no effect")
 	runCmd.Flags().StringVar(&signalCertKey, "cert-key", "", "Location of your SSL certificate private key. Can be used when you have an existing certificate and don't want a new certificate be generated automatically. If letsencrypt-domain is specified this property has no effect")
+	setFlagsFromEnvVars(runCmd)
 }