Add check/format command

cmd/sing-box/cmd_format.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+
+	"github.com/goccy/go-json"
+	"github.com/sagernet/sing-box/option"
+	"github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+)
+
+var commandFormatFlagWrite bool
+
+var commandFormat = &cobra.Command{
+	Use:   "format",
+	Short: "format configuration",
+	Run:   formatConfiguration,
+}
+
+func init() {
+	commandFormat.Flags().BoolVarP(&commandFormatFlagWrite, "write", "w", false, "write result to (source) file instead of stdout")
+}
+
+func formatConfiguration(cmd *cobra.Command, args []string) {
+	configContent, err := os.ReadFile(configPath)
+	if err != nil {
+		logrus.Fatal("read config: ", err)
+	}
+	var options option.Options
+	err = json.Unmarshal(configContent, &options)
+	if err != nil {
+		logrus.Fatal("decode config: ", err)
+	}
+	buffer := new(bytes.Buffer)
+	encoder := json.NewEncoder(buffer)
+	encoder.SetIndent("", "  ")
+	err = encoder.Encode(options)
+	if err != nil {
+		logrus.Fatal("encode config: ", err)
+	}
+	if !commandFormatFlagWrite {
+		os.Stdout.Write(buffer.Bytes())
+		return
+	}
+	if bytes.Compare(configContent, buffer.Bytes()) == 0 {
+		return
+	}
+	output, err := os.Create(configPath)
+	if err != nil {
+		logrus.Fatal("open output: ", err)
+	}
+	_, err = output.Write(buffer.Bytes())
+	output.Close()
+	if err != nil {
+		logrus.Fatal("write output: ", err)
+	}
+	outputPath, _ := filepath.Abs(configPath)
+	os.Stderr.WriteString(outputPath)
+}