Add `rule-set decompile` command

cmd/sing-box/cmd_rule_set_decompile.go

@@ -0,0 +1,83 @@
+package main
+
+import (
+	"io"
+	"os"
+	"strings"
+
+	"github.com/sagernet/sing-box/common/srs"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	"github.com/sagernet/sing/common/json"
+
+	"github.com/spf13/cobra"
+)
+
+var flagRuleSetDecompileOutput string
+
+const flagRuleSetDecompileDefaultOutput = "<file_name>.json"
+
+var commandRuleSetDecompile = &cobra.Command{
+	Use:   "decompile [binary-path]",
+	Short: "Decompile rule-set binary to json",
+	Args:  cobra.ExactArgs(1),
+	Run: func(cmd *cobra.Command, args []string) {
+		err := decompileRuleSet(args[0])
+		if err != nil {
+			log.Fatal(err)
+		}
+	},
+}
+
+func init() {
+	commandRuleSet.AddCommand(commandRuleSetDecompile)
+	commandRuleSetDecompile.Flags().StringVarP(&flagRuleSetDecompileOutput, "output", "o", flagRuleSetDecompileDefaultOutput, "Output file")
+}
+
+func decompileRuleSet(sourcePath string) error {
+	var (
+		reader io.Reader
+		err    error
+	)
+	if sourcePath == "stdin" {
+		reader = os.Stdin
+	} else {
+		reader, err = os.Open(sourcePath)
+		if err != nil {
+			return err
+		}
+	}
+	plainRuleSet, err := srs.Read(reader, true)
+	if err != nil {
+		return err
+	}
+	ruleSet := option.PlainRuleSetCompat{
+		Version: C.RuleSetVersion1,
+		Options: plainRuleSet,
+	}
+	var outputPath string
+	if flagRuleSetDecompileOutput == flagRuleSetDecompileDefaultOutput {
+		if strings.HasSuffix(sourcePath, ".srs") {
+			outputPath = sourcePath[:len(sourcePath)-4] + ".json"
+		} else {
+			outputPath = sourcePath + ".json"
+		}
+	} else {
+		outputPath = flagRuleSetDecompileOutput
+	}
+	outputFile, err := os.Create(outputPath)
+	if err != nil {
+		return err
+	}
+	encoder := json.NewEncoder(outputFile)
+	encoder.SetIndent("", "  ")
+	err = encoder.Encode(ruleSet)
+	if err != nil {
+		outputFile.Close()
+		os.Remove(outputPath)
+		return err
+	}
+	outputFile.Close()
+	return nil
+}