router/tools/ipadm/interactive.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"strings"
)

var stdinReader = bufio.NewReader(os.Stdin)

// prompt shows label with a "[current]" hint, reads one line, and returns
// current unchanged if the user just presses enter.
func prompt(label, current string) string {
	if current != "" {
		fmt.Printf("%s [%s]: ", label, current)
	} else {
		fmt.Printf("%s: ", label)
	}
	line, _ := stdinReader.ReadString('\n')
	line = strings.TrimSpace(line)
	if line == "" {
		return current
	}
	return line
}

// interactiveEdit implements the bare `ipadm <hostname>` form: add the host
// if it doesn't exist yet, otherwise edit it in place. Returns the updated
// host list, or an error if validation fails.
func interactiveEdit(hosts []Host, name string, cfg netConfig) ([]Host, error) {
	if err := validateHostname(name); err != nil {
		return nil, err
	}
	idx := findHost(hosts, name)

	var cur Host
	if idx >= 0 {
		cur = hosts[idx]
		fmt.Printf("Editing existing host %q (press enter to keep a value)\n", name)
	} else {
		cur = Host{Name: name}
		fmt.Printf("New host %q (press enter to accept defaults)\n", name)
	}

	// MAC decides which subnet the host belongs in (see netConfig), so it's
	// asked first and used to suggest a matching free IP below.
	for {
		mac := prompt("MAC address (optional, '-' to clear)", macOrDash(cur.MAC))
		if mac == "-" {
			mac = ""
		}
		norm, err := normalizeMAC(mac)
		if err != nil {
			fmt.Fprintln(os.Stderr, "error:", err)
			continue
		}
		cur.MAC = norm
		break
	}

	cidr := cfg.cidrFor(cur.MAC)
	suggested := cur.IP
	if suggested == "" || validateIP(suggested, cidr, cfg.gatewayIP) != nil {
		if freeIP, err := nextFreeIP(hosts, cidr, idx, cfg.gatewayIP); err == nil {
			suggested = freeIP
		}
	}

	for {
		ip := prompt(fmt.Sprintf("IP address (%s)", cidr), suggested)
		if err := validateIP(ip, cidr, cfg.gatewayIP); err != nil {
			fmt.Fprintln(os.Stderr, "error:", err)
			continue
		}
		cur.IP = ip
		break
	}

	cur.Comment = prompt("Comment", cur.Comment)

	if other := findByIP(hosts, cur.IP, idx); other >= 0 {
		return nil, fmt.Errorf("IP %s is already assigned to host %q", cur.IP, hosts[other].Name)
	}
	if other := findByMAC(hosts, cur.MAC, idx); other >= 0 {
		return nil, fmt.Errorf("MAC %s is already assigned to host %q", cur.MAC, hosts[other].Name)
	}

	if idx >= 0 {
		hosts[idx] = cur
	} else {
		hosts = append(hosts, cur)
	}
	return hosts, nil
}

func macOrDash(mac string) string {
	if mac == "" {
		return ""
	}
	return mac
}