[#1396] cli/playground: Improve terminal control key handling

Signed-off-by: Alexander Chuprov <a.chuprov@yadro.com>

cmd/frostfs-cli/modules/container/policy_playground.go

@@ -1,11 +1,10 @@
 package container
 
 import (
-	"bufio"
 	"encoding/hex"
 	"encoding/json"
+	"errors"
 	"fmt"
-	"io"
 	"os"
 	"strings"
 
@@ -14,6 +13,7 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-node/cmd/frostfs-cli/internal/key"
 	commonCmd "git.frostfs.info/TrueCloudLab/frostfs-node/cmd/internal/common"
 	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/netmap"
+	"github.com/chzyer/readline"
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
 )
@@ -163,6 +163,16 @@ func (repl *policyPlaygroundREPL) netMap() netmap.NetMap {
 	return nm
 }
 
+var policyPlaygroundCompleter = readline.NewPrefixCompleter(
+	readline.PcItem("list"),
+	readline.PcItem("ls"),
+	readline.PcItem("add"),
+	readline.PcItem("load"),
+	readline.PcItem("remove"),
+	readline.PcItem("rm"),
+	readline.PcItem("eval"),
+)
+
 func (repl *policyPlaygroundREPL) run() error {
 	if len(viper.GetString(commonflags.RPC)) > 0 {
 		key := key.GetOrGenerate(repl.cmd)
@@ -189,15 +199,32 @@ func (repl *policyPlaygroundREPL) run() error {
 		"rm":     repl.handleRemove,
 		"eval":   repl.handleEval,
 	}
-	for reader := bufio.NewReader(os.Stdin); ; {
+
-		fmt.Print("> ")
+	rl, err := readline.NewEx(&readline.Config{
-		line, err := reader.ReadString('\n')
+		Prompt:          "> ",
+		InterruptPrompt: "^C",
+		AutoComplete:    policyPlaygroundCompleter,
+	})
 	if err != nil {
-			if err == io.EOF {
+		return fmt.Errorf("error initializing readline: %w", err)
+	}
+	defer rl.Close()
+
+	var exit bool
+	for {
+		line, err := rl.Readline()
+		if err != nil {
+			if errors.Is(err, readline.ErrInterrupt) {
+				if exit {
 					return nil
 				}
+				exit = true
+				continue
+			}
 			return fmt.Errorf("reading line: %v", err)
 		}
+		exit = false
+
 		parts := strings.Fields(line)
 		if len(parts) == 0 {
 			continue