First stab at maglevc

cmd/maglevc/complete.go

@@ -0,0 +1,113 @@
+// Copyright (c) 2026, Pim van Pelt <pim@ipng.ch>
+
+package main
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/chzyer/readline"
+
+	"git.ipng.ch/ipng/vpp-maglev/internal/grpcapi"
+)
+
+const completeTimeout = 1 * time.Second
+
+// Completer implements readline.AutoCompleter for the command tree.
+type Completer struct {
+	root   *Node
+	client grpcapi.MaglevClient
+}
+
+// Do implements readline.AutoCompleter.
+// line is the full current line; pos is the cursor position.
+// Returns (newLine [][]rune, length int) where length is how many rune bytes
+// before pos should be replaced by each candidate in newLine.
+func (co *Completer) Do(line []rune, pos int) (newLine [][]rune, length int) {
+	before := string(line[:pos])
+	tokens := splitTokens(before)
+
+	// Determine the partial token being completed.
+	var partial string
+	var prefix []string
+	if len(tokens) == 0 || (len(before) > 0 && before[len(before)-1] == ' ') {
+		// Cursor is after a space — completing a new token.
+		prefix = tokens
+		partial = ""
+	} else {
+		// Cursor is within the last token.
+		prefix = tokens[:len(tokens)-1]
+		partial = tokens[len(tokens)-1]
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), completeTimeout)
+	defer cancel()
+
+	candidates := Candidates(co.root, prefix, partial, ctx, co.client)
+
+	var suffixes [][]rune
+	for _, c := range candidates {
+		suffix := c.Word[len(partial):]
+		suffixes = append(suffixes, []rune(suffix+" "))
+	}
+	return suffixes, len([]rune(partial))
+}
+
+// questionListener intercepts the '?' key and prints inline help.
+type questionListener struct {
+	root   *Node
+	client grpcapi.MaglevClient
+	rl     *readline.Instance
+}
+
+func (ql *questionListener) OnChange(line []rune, pos int, key rune) (newLine []rune, newPos int, ok bool) {
+	if key != '?' {
+		return line, pos, false
+	}
+
+	// line[:pos] includes the '?' just typed — strip it before tokenizing.
+	before := string(line[:pos])
+	if len(before) > 0 && before[len(before)-1] == '?' {
+		before = before[:len(before)-1]
+	}
+	tokens := splitTokens(before)
+
+	var partial string
+	var prefix []string
+	if len(before) == 0 || before[len(before)-1] == ' ' {
+		prefix = tokens
+		partial = ""
+	} else if len(tokens) > 0 {
+		prefix = tokens[:len(tokens)-1]
+		partial = tokens[len(tokens)-1]
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), completeTimeout)
+	defer cancel()
+
+	candidates := Candidates(ql.root, prefix, partial, ctx, ql.client)
+
+	fmt.Fprintf(ql.rl.Stderr(), "\r\n")
+	if len(candidates) == 0 {
+		fmt.Fprintf(ql.rl.Stderr(), "  <no completions>\r\n")
+	} else {
+		for _, c := range candidates {
+			if c.Help != "" {
+				fmt.Fprintf(ql.rl.Stderr(), "  %-20s  %s\r\n", c.Word, c.Help)
+			} else {
+				fmt.Fprintf(ql.rl.Stderr(), "  %s\r\n", c.Word)
+			}
+		}
+	}
+
+	// Remove the '?' from the line and return with cursor one step back.
+	newLine = append(append([]rune{}, line[:pos-1]...), line[pos:]...)
+	return newLine, pos - 1, true
+}
+
+// splitTokens splits a string into whitespace-separated tokens.
+func splitTokens(s string) []string {
+	return strings.Fields(s)
+}