wip: complete subcommands after bare flags

commands/commands.go

@@ -85,6 +85,24 @@ func Run(v string) int {
 	sort.Sort(cli.CommandsByName(commands))
 	app.Commands = commands
 	app.EnableBashCompletion = true
+	app.BashComplete = func(cCtx *cli.Context) {
+		// ripped from cli.DefaultCompleteWithFlags
+		var lastArg string
+
+		if len(os.Args) > 2 {
+			lastArg = os.Args[len(os.Args)-2]
+		}
+
+		if lastArg != "" {
+			if strings.HasPrefix(lastArg, "-") {
+				if !islastFlagComplete(lastArg, app.Flags) {
+					dnscontrolPrintFlagSuggestions(lastArg, app.Flags, cCtx.App.Writer)
+					return
+				}
+			}
+		}
+		dnscontrolPrintCommandSuggestions(app.Commands, cCtx.App.Writer)
+	}
 	if err := app.Run(os.Args); err != nil {
 		return 1
 	}

commands/completion.go

@@ -4,11 +4,14 @@ import (
 	"embed"
 	"errors"
 	"fmt"
-	"github.com/urfave/cli/v2"
+	"io"
 	"os"
 	"path"
 	"strings"
 	"text/template"
+	"unicode/utf8"
+
+	"github.com/urfave/cli/v2"
 )
 
 //go:embed completion-scripts/completion.*.gotmpl
@@ -89,3 +92,79 @@ func getCompletionSupportedShells() (shells []string, shellCompletionScripts map
 	}
 	return shells, shellCompletionScripts, nil
 }
+
+func dnscontrolPrintCommandSuggestions(commands []*cli.Command, writer io.Writer) {
+	for _, command := range commands {
+		if command.Hidden {
+			continue
+		}
+		if strings.HasSuffix(os.Getenv("SHELL"), "zsh") {
+			for _, name := range command.Names() {
+				_, _ = fmt.Fprintf(writer, "%s:%s\n", name, command.Usage)
+			}
+		} else {
+			for _, name := range command.Names() {
+				_, _ = fmt.Fprintf(writer, "%s\n", name)
+			}
+		}
+	}
+}
+
+func dnscontrolCliArgContains(flagName string) bool {
+	for _, name := range strings.Split(flagName, ",") {
+		name = strings.TrimSpace(name)
+		count := utf8.RuneCountInString(name)
+		if count > 2 {
+			count = 2
+		}
+		flag := fmt.Sprintf("%s%s", strings.Repeat("-", count), name)
+		for _, a := range os.Args {
+			if a == flag {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+func dnscontrolPrintFlagSuggestions(lastArg string, flags []cli.Flag, writer io.Writer) {
+	cur := strings.TrimPrefix(lastArg, "-")
+	cur = strings.TrimPrefix(cur, "-")
+	for _, flag := range flags {
+		if bflag, ok := flag.(*cli.BoolFlag); ok && bflag.Hidden {
+			continue
+		}
+		for _, name := range flag.Names() {
+			name = strings.TrimSpace(name)
+			// this will get total count utf8 letters in flag name
+			count := utf8.RuneCountInString(name)
+			if count > 2 {
+				count = 2 // reuse this count to generate single - or -- in flag completion
+			}
+			// if flag name has more than one utf8 letter and last argument in cli has -- prefix then
+			// skip flag completion for short flags example -v or -x
+			if strings.HasPrefix(lastArg, "--") && count == 1 {
+				continue
+			}
+			// match if last argument matches this flag and it is not repeated
+			if strings.HasPrefix(name, cur) && cur != name && !dnscontrolCliArgContains(name) {
+				flagCompletion := fmt.Sprintf("%s%s", strings.Repeat("-", count), name)
+				_, _ = fmt.Fprintln(writer, flagCompletion)
+			}
+		}
+	}
+}
+
+func islastFlagComplete(lastArg string, flags []cli.Flag) bool {
+	cur := strings.TrimPrefix(lastArg, "-")
+	cur = strings.TrimPrefix(cur, "-")
+	for _, flag := range flags {
+		for _, name := range flag.Names() {
+			name = strings.TrimSpace(name)
+			if strings.HasPrefix(name, cur) && cur != name && !dnscontrolCliArgContains(name) {
+				return false
+			}
+		}
+	}
+	return true
+}