Adding support for JSON-formatted output 1/n

cmd/headscale/cli/utils.go

@@ -1,6 +1,8 @@
 package cli
 
 import (
+	"encoding/json"
+	"fmt"
 	"io"
 	"log"
 	"os"
@@ -13,6 +15,10 @@ import (
 	"tailscale.com/tailcfg"
 )
 
+type ErrorOutput struct {
+	Error string
+}
+
 func absPath(path string) string {
 	// If a relative path is provided, prefix it with the the directory where
 	// the config file was found.
@@ -72,3 +78,35 @@ func loadDerpMap(path string) (*tailcfg.DERPMap, error) {
 	err = yaml.Unmarshal(b, &derpMap)
 	return &derpMap, err
 }
+
+func jsonOutput(result interface{}, errResult error, outputFormat string) {
+	var j []byte
+	var err error
+	switch outputFormat {
+	case "json":
+		if errResult != nil {
+			j, err = json.MarshalIndent(ErrorOutput{errResult.Error()}, "", "\t")
+			if err != nil {
+				log.Fatalln(err)
+			}
+		} else {
+			j, err = json.MarshalIndent(result, "", "\t")
+			if err != nil {
+				log.Fatalln(err)
+			}
+		}
+	case "json-line":
+		if errResult != nil {
+			j, err = json.Marshal(ErrorOutput{errResult.Error()})
+			if err != nil {
+				log.Fatalln(err)
+			}
+		} else {
+			j, err = json.Marshal(result)
+			if err != nil {
+				log.Fatalln(err)
+			}
+		}
+	}
+	fmt.Println(string(j))
+}