maintenance: add simple host completion

Author: tschaefer

cmd/completion/completion.go

@@ -5,6 +5,14 @@ Licensed under the MIT license, see LICENSE in the project root for details.
 package completion
 
 import (
+	"bufio"
+	"errors"
+	"fmt"
+	"maps"
+	"os"
+	"os/user"
+	"slices"
+
 	"github.com/spf13/cobra"
 	"github.com/tschaefer/finchctl/internal/config"
 )
@@ -39,3 +47,43 @@ func CompleteDashboardRole(cmd *cobra.Command, args []string, toComplete string)
 
 	return []string{"viewer", "operator", "admin"}, cobra.ShellCompDirectiveNoFileComp
 }
+
+func CompleteHostName(cmd *cobra.Command, args []string, toComplete string) ([]cobra.Completion, cobra.ShellCompDirective) {
+	if len(args) != 0 {
+		return nil, cobra.ShellCompDirectiveNoFileComp
+	}
+
+	curUser, err := user.Current()
+	if err != nil {
+		panic(err)
+	}
+
+	knownHosts := curUser.HomeDir + "/.ssh/known_hosts"
+	if _, err = os.Stat(knownHosts); errors.Is(err, os.ErrNotExist) {
+		return nil, cobra.ShellCompDirectiveNoFileComp
+	}
+
+	readFile, err := os.Open(knownHosts)
+	if err != nil {
+		return nil, cobra.ShellCompDirectiveNoFileComp
+	}
+	defer func() {
+		_ = readFile.Close()
+	}()
+
+	fileScanner := bufio.NewScanner(readFile)
+	fileScanner.Split(bufio.ScanLines)
+
+	hosts := map[string]int{}
+	for fileScanner.Scan() {
+		var host string
+		if _, err := fmt.Sscan(fileScanner.Text(), &host); err != nil {
+			continue
+		}
+
+		hosts[host] = 1
+	}
+	list := slices.Sorted(maps.Keys(hosts))
+
+	return list, cobra.ShellCompDirectiveNoFileComp
+}

cmd/service/deploy.go

@@ -19,10 +19,11 @@ import (
 )
 
 var deployCmd = &cobra.Command{
-	Use:   "deploy [user@]host[:port]",
-	Short: "Deploy Finch service to a remote host",
-	Args:  cobra.ExactArgs(1),
-	Run:   runDeployCmd,
+	Use:               "deploy [user@]host[:port]",
+	Short:             "Deploy Finch service to a remote host",
+	Args:              cobra.ExactArgs(1),
+	Run:               runDeployCmd,
+	ValidArgsFunction: completion.CompleteHostName,
 }
 
 func init() {

cmd/service/deregister.go

@@ -15,10 +15,11 @@ import (
 )
 
 var deregisterCmd = &cobra.Command{
-	Use:   "deregister [user@]host[:port]",
-	Short: "Deregister the client from a service on a remote host",
-	Args:  cobra.ExactArgs(1),
-	Run:   runDeregisterCmd,
+	Use:               "deregister [user@]host[:port]",
+	Short:             "Deregister the client from a service on a remote host",
+	Args:              cobra.ExactArgs(1),
+	Run:               runDeregisterCmd,
+	ValidArgsFunction: completion.CompleteHostName,
 }
 
 func init() {

cmd/service/register.go

@@ -15,10 +15,11 @@ import (
 )
 
 var registerCmd = &cobra.Command{
-	Use:   "register [user@]host[:port]",
-	Short: "Register the client with a service on a remote host",
-	Args:  cobra.ExactArgs(1),
-	Run:   runRegisterCmd,
+	Use:               "register [user@]host[:port]",
+	Short:             "Register the client with a service on a remote host",
+	Args:              cobra.ExactArgs(1),
+	Run:               runRegisterCmd,
+	ValidArgsFunction: completion.CompleteHostName,
 }
 
 func init() {

cmd/service/rotate_certificate.go

@@ -15,10 +15,11 @@ import (
 )
 
 var rotateCertificateCmd = &cobra.Command{
-	Use:   "rotate-certificate [user@]host[:port]",
-	Short: "Rotate mTLS certificates of a service on a remote host",
-	Args:  cobra.ExactArgs(1),
-	Run:   runRotateCertificateCmd,
+	Use:               "rotate-certificate [user@]host[:port]",
+	Short:             "Rotate mTLS certificates of a service on a remote host",
+	Args:              cobra.ExactArgs(1),
+	Run:               runRotateCertificateCmd,
+	ValidArgsFunction: completion.CompleteHostName,
 }
 
 func init() {

cmd/service/rotate_secret.go

@@ -15,10 +15,11 @@ import (
 )
 
 var rotateSecretCmd = &cobra.Command{
-	Use:   "rotate-secret [user@]host[:port]",
-	Short: "Rotate secret of a service on a remote host",
-	Args:  cobra.ExactArgs(1),
-	Run:   runRotateSecretCmd,
+	Use:               "rotate-secret [user@]host[:port]",
+	Short:             "Rotate secret of a service on a remote host",
+	Args:              cobra.ExactArgs(1),
+	Run:               runRotateSecretCmd,
+	ValidArgsFunction: completion.CompleteHostName,
 }
 
 func init() {

cmd/service/teardown.go

@@ -19,10 +19,11 @@ import (
 )
 
 var teardownCmd = &cobra.Command{
-	Use:   "teardown [user@]host[:port]",
-	Short: "Tear down Finch service from a remote host",
-	Args:  cobra.ExactArgs(1),
-	Run:   runTeardownCmd,
+	Use:               "teardown [user@]host[:port]",
+	Short:             "Tear down Finch service from a remote host",
+	Args:              cobra.ExactArgs(1),
+	Run:               runTeardownCmd,
+	ValidArgsFunction: completion.CompleteHostName,
 }
 
 func init() {

cmd/service/update.go

@@ -15,10 +15,11 @@ import (
 )
 
 var updateCmd = &cobra.Command{
-	Use:   "update [user@]host[:port]",
-	Short: "Update service on a remote host",
-	Args:  cobra.ExactArgs(1),
-	Run:   runUpdateCmd,
+	Use:               "update [user@]host[:port]",
+	Short:             "Update service on a remote host",
+	Args:              cobra.ExactArgs(1),
+	Run:               runUpdateCmd,
+	ValidArgsFunction: completion.CompleteHostName,
 }
 
 func init() {