First stab at maglevc

cmd/maglevc/shell.go

@@ -0,0 +1,94 @@
+// Copyright (c) 2026, Pim van Pelt <pim@ipng.ch>
+
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+
+	"github.com/chzyer/readline"
+
+	"git.ipng.ch/ipng/vpp-maglev/internal/grpcapi"
+)
+
+// errQuit is a sentinel returned by runQuit to exit the REPL.
+var errQuit = errors.New("quit")
+
+// runShell runs the interactive REPL until the user types quit/exit or EOF.
+func runShell(ctx context.Context, client grpcapi.MaglevClient) error {
+	root := buildTree()
+
+	comp := &Completer{root: root, client: client}
+	ql := &questionListener{root: root, client: client}
+
+	cfg := &readline.Config{
+		Prompt:          "maglev> ",
+		AutoComplete:    comp,
+		InterruptPrompt: "^C",
+		EOFPrompt:       "exit",
+		Listener:        ql,
+	}
+	rl, err := readline.NewEx(cfg)
+	if err != nil {
+		return fmt.Errorf("readline init: %w", err)
+	}
+	ql.rl = rl
+	defer rl.Close()
+
+	for {
+		line, err := rl.Readline()
+		if err == readline.ErrInterrupt {
+			continue
+		}
+		if err == io.EOF {
+			return nil
+		}
+		if err != nil {
+			return err
+		}
+
+		tokens := splitTokens(line)
+		if len(tokens) == 0 {
+			continue
+		}
+
+		if err := dispatch(ctx, root, client, tokens); err != nil {
+			if errors.Is(err, errQuit) {
+				return nil
+			}
+			fmt.Fprintf(rl.Stderr(), "error: %v\n", err)
+		}
+	}
+}
+
+// dispatch walks the tree and executes the matched command.
+func dispatch(ctx context.Context, root *Node, client grpcapi.MaglevClient, tokens []string) error {
+	node, args := Walk(root, tokens)
+
+	if node.Run == nil {
+		showHelp(root, tokens)
+		return nil
+	}
+
+	return node.Run(ctx, client, args)
+}
+
+// showHelp prints available completions for the given token path.
+func showHelp(root *Node, tokens []string) {
+	node, _ := Walk(root, tokens)
+
+	candidates := filterFixedChildren(node.Children, "")
+	if len(candidates) == 0 {
+		fmt.Println("  <no completions>")
+		return
+	}
+	for _, c := range candidates {
+		if c.Help != "" {
+			fmt.Printf("  %-20s  %s\n", c.Word, c.Help)
+		} else {
+			fmt.Printf("  %s\n", c.Word)
+		}
+	}
+}