Adding support for JSON-formatted output 1/n

cmd/headscale/cli/namespaces.go

@@ -3,6 +3,7 @@ package cli
 import (
 	"fmt"
 	"log"
+	"strings"
 
 	"github.com/spf13/cobra"
 )
@@ -22,16 +23,21 @@ var CreateNamespaceCmd = &cobra.Command{
 		return nil
 	},
 	Run: func(cmd *cobra.Command, args []string) {
+		o, _ := cmd.Flags().GetString("output")
 		h, err := getHeadscaleApp()
 		if err != nil {
 			log.Fatalf("Error initializing: %s", err)
 		}
-		_, err = h.CreateNamespace(args[0])
+		namespace, err := h.CreateNamespace(args[0])
-		if err != nil {
+		if strings.HasPrefix(o, "json") {
-			fmt.Println(err)
+			jsonOutput(namespace, err, o)
 			return
 		}
-		fmt.Printf("Ook.\n")
+		if err != nil {
+			fmt.Printf("Error creating namespace: %s\n", err)
+			return
+		}
+		fmt.Printf("Namespace created\n")
 	},
 }
 
@@ -39,17 +45,22 @@ var ListNamespacesCmd = &cobra.Command{
 	Use:   "list",
 	Short: "List all the namespaces",
 	Run: func(cmd *cobra.Command, args []string) {
+		o, _ := cmd.Flags().GetString("output")
 		h, err := getHeadscaleApp()
 		if err != nil {
 			log.Fatalf("Error initializing: %s", err)
 		}
-		ns, err := h.ListNamespaces()
+		namespaces, err := h.ListNamespaces()
+		if strings.HasPrefix(o, "json") {
+			jsonOutput(namespaces, err, o)
+			return
+		}
 		if err != nil {
 			fmt.Println(err)
 			return
 		}
 		fmt.Printf("ID\tName\n")
-		for _, n := range *ns {
+		for _, n := range *namespaces {
 			fmt.Printf("%d\t%s\n", n.ID, n.Name)
 		}
 	},

cmd/headscale/cli/nodes.go

@@ -3,6 +3,7 @@ package cli
 import (
 	"fmt"
 	"log"
+	"strings"
 
 	"github.com/spf13/cobra"
 )
@@ -21,17 +22,22 @@ var RegisterCmd = &cobra.Command{
 		if err != nil {
 			log.Fatalf("Error getting namespace: %s", err)
 		}
+		o, _ := cmd.Flags().GetString("output")
 
 		h, err := getHeadscaleApp()
 		if err != nil {
 			log.Fatalf("Error initializing: %s", err)
 		}
-		err = h.RegisterMachine(args[0], n)
+		m, err := h.RegisterMachine(args[0], n)
-		if err != nil {
+		if strings.HasPrefix(o, "json") {
-			fmt.Printf("Error: %s", err)
+			jsonOutput(m, err, o)
 			return
 		}
-		fmt.Println("Ook.")
+		if err != nil {
+			fmt.Printf("Cannot register machine: %s\n", err)
+			return
+		}
+		fmt.Printf("Machine registered\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))
+}

cmd/headscale/headscale.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"encoding/json"
 	"errors"
 	"fmt"
 	"log"
@@ -19,7 +20,27 @@ var versionCmd = &cobra.Command{
 	Short: "Print the version.",
 	Long:  "The version of headscale.",
 	Run: func(cmd *cobra.Command, args []string) {
-		fmt.Println(version)
+
+		o, _ := cmd.Flags().GetString("output")
+		switch o {
+		case "":
+			fmt.Println(version)
+		case "json":
+			j, err := json.MarshalIndent(map[string]string{"version": version}, "", "\t")
+			if err != nil {
+				log.Fatalln(err)
+			}
+			fmt.Println(string(j))
+
+		case "json-line":
+			j, err := json.Marshal(map[string]string{"version": version})
+			if err != nil {
+				log.Fatalln(err)
+			}
+			fmt.Println(string(j))
+		default:
+			fmt.Printf("Unknown format %s\n", o)
+		}
 	},
 }
 
@@ -123,6 +144,8 @@ func main() {
 	cli.CreatePreAuthKeyCmd.PersistentFlags().Bool("reusable", false, "Make the preauthkey reusable")
 	cli.CreatePreAuthKeyCmd.Flags().StringP("expiration", "e", "", "Human-readable expiration of the key (30m, 24h, 365d...)")
 
+	headscaleCmd.PersistentFlags().StringP("output", "o", "", "Output format. Empty for human-readable, 'json' or 'json-line'")
+
 	if err := headscaleCmd.Execute(); err != nil {
 		fmt.Println(err)
 		os.Exit(-1)