commit b7987248c198964feecdee87a89327a91d4423bc
Author: DCreason <dakotacreason@gmail.com>
Date:   Thu Mar 19 15:00:10 2026 +0000

    init

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..5241cc6
--- /dev/null
+++ b/README.md
@@ -0,0 +1,31 @@
+# samba-configer
+
+`samba-configer` is a small interactive terminal program for reading an existing Samba configuration, listing shares, and guiding add/edit/delete operations.
+
+It is implemented in Go with only the standard library so it builds into a single executable easily.
+
+## Build
+
+```bash
+go build -o samba-configer .
+```
+
+## Run
+
+```bash
+./samba-configer -config /etc/samba/smb.conf
+```
+
+The program:
+
+- Reads the Samba config and parses non-`[global]` sections as shares.
+- Prompts to add, edit, or delete a share.
+- Checks `valid users` entries against local accounts.
+- Offers to create missing local accounts with `useradd -M -s /usr/sbin/nologin <user>`.
+- Writes a timestamped backup before saving changes.
+
+If you create a local account for a Samba-authenticated share, you may still need to add the Samba password separately:
+
+```bash
+smbpasswd -a <username>
+```
diff --git a/app.go b/app.go
new file mode 100644
index 0000000..bf8a27b
--- /dev/null
+++ b/app.go
@@ -0,0 +1,384 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"os/user"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"time"
+)
+
+var ErrCancelled = errors.New("cancelled")
+
+type UserManager interface {
+	UserExists(name string) bool
+	CreateUser(name string) error
+}
+
+type CommandRunner interface {
+	Run(name string, args ...string) error
+}
+
+type RealUserManager struct{}
+
+func (RealUserManager) UserExists(name string) bool {
+	_, err := user.Lookup(name)
+	return err == nil
+}
+
+func (RealUserManager) CreateUser(name string) error {
+	runner := OSCommandRunner{}
+	return runner.Run("useradd", "-M", "-s", "/usr/sbin/nologin", name)
+}
+
+type OSCommandRunner struct{}
+
+func (OSCommandRunner) Run(name string, args ...string) error {
+	cmd := exec.Command(name, args...)
+	cmd.Stdin = os.Stdin
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}
+
+type App struct {
+	configPath string
+	users      UserManager
+	reader     *bufio.Reader
+	writer     *bufio.Writer
+}
+
+func NewApp(configPath string, users UserManager) *App {
+	return &App{
+		configPath: configPath,
+		users:      users,
+		reader:     bufio.NewReader(os.Stdin),
+		writer:     bufio.NewWriter(os.Stdout),
+	}
+}
+
+func (a *App) Run() error {
+	doc, err := ParseConfigFile(a.configPath)
+	if err != nil {
+		return fmt.Errorf("read config: %w", err)
+	}
+
+	for {
+		shareSections := doc.ShareSections()
+		a.println("")
+		a.println("Samba share editor")
+		a.println("==================")
+		a.println("Current shares:")
+		if len(shareSections) == 0 {
+			a.println("  (none)")
+		} else {
+			for i, section := range shareSections {
+				cfg := ShareFromSection(section)
+				a.printf("  %d. %s -> %s\n", i+1, cfg.Name, cfg.Path)
+			}
+		}
+		a.println("")
+		a.println("[a] add share")
+		a.println("[e] edit share")
+		a.println("[d] delete share")
+		a.println("[w] write config and exit")
+		a.println("[q] quit without saving")
+		a.flush()
+
+		choice, err := a.prompt("Select an action")
+		if err != nil {
+			return err
+		}
+
+		switch strings.ToLower(choice) {
+		case "a", "add":
+			if err := a.addShare(doc); err != nil {
+				return err
+			}
+		case "e", "edit":
+			if err := a.editShare(doc); err != nil {
+				return err
+			}
+		case "d", "delete":
+			if err := a.deleteShare(doc); err != nil {
+				return err
+			}
+		case "w", "write":
+			return a.writeConfig(doc)
+		case "q", "quit":
+			return nil
+		default:
+			a.println("Unknown choice.")
+		}
+	}
+}
+
+func (a *App) addShare(doc *Document) error {
+	cfg, err := a.collectShareConfig(ShareConfig{})
+	if err != nil {
+		return err
+	}
+
+	if doc.Section(cfg.Name) != nil {
+		a.println("A share with that name already exists.")
+		return nil
+	}
+
+	if err := a.ensureUsers(cfg.ValidUsers); err != nil {
+		return err
+	}
+
+	doc.UpsertSection(BuildShareSection(nil, cfg))
+	a.println("Share added.")
+	return nil
+}
+
+func (a *App) editShare(doc *Document) error {
+	section, err := a.selectShare(doc)
+	if err != nil || section == nil {
+		return err
+	}
+
+	originalName := section.Name
+	cfg, err := a.collectShareConfig(ShareFromSection(section))
+	if err != nil {
+		return err
+	}
+
+	if !strings.EqualFold(originalName, cfg.Name) && doc.Section(cfg.Name) != nil {
+		a.println("A share with that new name already exists.")
+		return nil
+	}
+
+	if err := a.ensureUsers(cfg.ValidUsers); err != nil {
+		return err
+	}
+
+	if !strings.EqualFold(originalName, cfg.Name) {
+		doc.DeleteSection(originalName)
+	}
+	doc.UpsertSection(BuildShareSection(section, cfg))
+	a.println("Share updated.")
+	return nil
+}
+
+func (a *App) deleteShare(doc *Document) error {
+	section, err := a.selectShare(doc)
+	if err != nil || section == nil {
+		return err
+	}
+
+	confirm, err := a.confirm(fmt.Sprintf("Delete share %q", section.Name), false)
+	if err != nil {
+		return err
+	}
+	if !confirm {
+		a.println("Delete cancelled.")
+		return nil
+	}
+
+	doc.DeleteSection(section.Name)
+	a.println("Share deleted.")
+	return nil
+}
+
+func (a *App) writeConfig(doc *Document) error {
+	backup := fmt.Sprintf("%s.bak.%s", a.configPath, time.Now().UTC().Format("20060102T150405Z"))
+	if err := copyFile(a.configPath, backup); err != nil {
+		return fmt.Errorf("create backup %s: %w", backup, err)
+	}
+
+	if err := os.WriteFile(a.configPath, []byte(doc.Serialize()), 0o644); err != nil {
+		return fmt.Errorf("write config: %w", err)
+	}
+
+	a.printf("Config written to %s\n", a.configPath)
+	a.printf("Backup saved to %s\n", backup)
+	return nil
+}
+
+func (a *App) selectShare(doc *Document) (*Section, error) {
+	shares := doc.ShareSections()
+	if len(shares) == 0 {
+		a.println("There are no shares to select.")
+		return nil, nil
+	}
+
+	raw, err := a.prompt("Share number")
+	if err != nil {
+		return nil, err
+	}
+
+	index, err := strconv.Atoi(raw)
+	if err != nil || index < 1 || index > len(shares) {
+		a.println("Invalid selection.")
+		return nil, nil
+	}
+
+	return shares[index-1], nil
+}
+
+func (a *App) collectShareConfig(existing ShareConfig) (ShareConfig, error) {
+	name, err := a.promptDefault("Share name", existing.Name)
+	if err != nil {
+		return ShareConfig{}, err
+	}
+	name = strings.TrimSpace(name)
+	if name == "" {
+		return ShareConfig{}, errors.New("share name cannot be empty")
+	}
+
+	path, err := a.promptDefault("Path", existing.Path)
+	if err != nil {
+		return ShareConfig{}, err
+	}
+	path = strings.TrimSpace(path)
+	if path == "" {
+		return ShareConfig{}, errors.New("path cannot be empty")
+	}
+
+	comment, err := a.promptDefault("Comment", existing.Comment)
+	if err != nil {
+		return ShareConfig{}, err
+	}
+
+	browseable, err := a.promptDefault("Browseable (yes/no)", defaultString(existing.Browseable, "yes"))
+	if err != nil {
+		return ShareConfig{}, err
+	}
+
+	readOnly, err := a.promptDefault("Read only (yes/no)", defaultString(existing.ReadOnly, "no"))
+	if err != nil {
+		return ShareConfig{}, err
+	}
+
+	guestOK, err := a.promptDefault("Guest ok (yes/no)", defaultString(existing.GuestOK, "no"))
+	if err != nil {
+		return ShareConfig{}, err
+	}
+
+	usersDefault := strings.Join(existing.ValidUsers, ", ")
+	usersRaw, err := a.promptDefault("Valid users (comma or space separated, blank for none)", usersDefault)
+	if err != nil {
+		return ShareConfig{}, err
+	}
+
+	return ShareConfig{
+		Name:       name,
+		Path:       filepath.Clean(path),
+		Comment:    strings.TrimSpace(comment),
+		Browseable: browseable,
+		ReadOnly:   readOnly,
+		GuestOK:    guestOK,
+		ValidUsers: splitUsers(usersRaw),
+	}, nil
+}
+
+func (a *App) ensureUsers(users []string) error {
+	for _, name := range users {
+		if a.users.UserExists(name) {
+			continue
+		}
+
+		create, err := a.confirm(fmt.Sprintf("User %q does not exist. Create it with useradd", name), true)
+		if err != nil {
+			return err
+		}
+		if !create {
+			continue
+		}
+
+		if err := a.users.CreateUser(name); err != nil {
+			return fmt.Errorf("create user %s: %w", name, err)
+		}
+
+		a.printf("Created local user %s\n", name)
+		a.println("If Samba authentication is required, add a Samba password with: smbpasswd -a " + name)
+	}
+
+	return nil
+}
+
+func (a *App) prompt(label string) (string, error) {
+	a.printf("%s: ", label)
+	a.flush()
+	text, err := a.reader.ReadString('\n')
+	if err != nil {
+		return "", err
+	}
+	return strings.TrimSpace(text), nil
+}
+
+func (a *App) promptDefault(label, defaultValue string) (string, error) {
+	if defaultValue == "" {
+		return a.prompt(label)
+	}
+
+	a.printf("%s [%s]: ", label, defaultValue)
+	a.flush()
+	text, err := a.reader.ReadString('\n')
+	if err != nil {
+		return "", err
+	}
+	text = strings.TrimSpace(text)
+	if text == "" {
+		return defaultValue, nil
+	}
+	return text, nil
+}
+
+func (a *App) confirm(label string, defaultYes bool) (bool, error) {
+	suffix := "y/N"
+	if defaultYes {
+		suffix = "Y/n"
+	}
+
+	answer, err := a.prompt(fmt.Sprintf("%s [%s]", label, suffix))
+	if err != nil {
+		return false, err
+	}
+	if answer == "" {
+		return defaultYes, nil
+	}
+
+	switch strings.ToLower(answer) {
+	case "y", "yes":
+		return true, nil
+	case "n", "no":
+		return false, nil
+	default:
+		return false, errors.New("expected yes or no")
+	}
+}
+
+func (a *App) println(line string) {
+	fmt.Fprintln(a.writer, line)
+}
+
+func (a *App) printf(format string, args ...any) {
+	fmt.Fprintf(a.writer, format, args...)
+}
+
+func (a *App) flush() {
+	_ = a.writer.Flush()
+}
+
+func defaultString(value, fallback string) string {
+	if strings.TrimSpace(value) == "" {
+		return fallback
+	}
+	return value
+}
+
+func copyFile(src, dst string) error {
+	data, err := os.ReadFile(src)
+	if err != nil {
+		return err
+	}
+	return os.WriteFile(dst, data, 0o644)
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..f5562f0
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module samba-configer
+
+go 1.25.0
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..4916c3b
--- /dev/null
+++ b/main.go
@@ -0,0 +1,24 @@
+package main
+
+import (
+	"errors"
+	"flag"
+	"fmt"
+	"os"
+)
+
+func main() {
+	configPath := flag.String("config", "/etc/samba/smb.conf", "path to smb.conf")
+	flag.Parse()
+
+	app := NewApp(*configPath, RealUserManager{})
+	if err := app.Run(); err != nil {
+		if errors.Is(err, ErrCancelled) {
+			fmt.Fprintln(os.Stderr, "cancelled")
+			os.Exit(1)
+		}
+
+		fmt.Fprintf(os.Stderr, "error: %v\n", err)
+		os.Exit(1)
+	}
+}
diff --git a/parser.go b/parser.go
new file mode 100644
index 0000000..22525fd
--- /dev/null
+++ b/parser.go
@@ -0,0 +1,297 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"slices"
+	"strings"
+)
+
+type Document struct {
+	Preamble []string
+	Sections []*Section
+}
+
+type Section struct {
+	Name  string
+	Lines []Line
+}
+
+type Line struct {
+	Raw      string
+	Key      string
+	Value    string
+	IsKV     bool
+	Disabled bool
+}
+
+func ParseConfigFile(path string) (*Document, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	return ParseConfig(string(data))
+}
+
+func ParseConfig(contents string) (*Document, error) {
+	doc := &Document{}
+	var current *Section
+
+	scanner := bufio.NewScanner(strings.NewReader(contents))
+	for scanner.Scan() {
+		raw := scanner.Text()
+		trimmed := strings.TrimSpace(raw)
+		if strings.HasPrefix(trimmed, "[") && strings.HasSuffix(trimmed, "]") {
+			name := strings.TrimSpace(trimmed[1 : len(trimmed)-1])
+			current = &Section{Name: name}
+			doc.Sections = append(doc.Sections, current)
+			continue
+		}
+
+		line := parseLine(raw)
+		if current == nil {
+			doc.Preamble = append(doc.Preamble, raw)
+			continue
+		}
+		current.Lines = append(current.Lines, line)
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, err
+	}
+
+	return doc, nil
+}
+
+func parseLine(raw string) Line {
+	trimmed := strings.TrimSpace(raw)
+	if trimmed == "" || strings.HasPrefix(trimmed, "#") || strings.HasPrefix(trimmed, ";") {
+		return Line{Raw: raw}
+	}
+
+	disabled := false
+	parseTarget := trimmed
+	if strings.HasPrefix(parseTarget, "#") || strings.HasPrefix(parseTarget, ";") {
+		disabled = true
+		parseTarget = strings.TrimSpace(parseTarget[1:])
+	}
+
+	key, value, ok := strings.Cut(parseTarget, "=")
+	if !ok {
+		return Line{Raw: raw}
+	}
+
+	return Line{
+		Raw:      raw,
+		Key:      strings.TrimSpace(strings.ToLower(key)),
+		Value:    strings.TrimSpace(value),
+		IsKV:     true,
+		Disabled: disabled,
+	}
+}
+
+func (d *Document) ShareSections() []*Section {
+	var shares []*Section
+	for _, section := range d.Sections {
+		if !strings.EqualFold(section.Name, "global") {
+			shares = append(shares, section)
+		}
+	}
+	return shares
+}
+
+func (d *Document) Section(name string) *Section {
+	for _, section := range d.Sections {
+		if strings.EqualFold(section.Name, name) {
+			return section
+		}
+	}
+	return nil
+}
+
+func (d *Document) DeleteSection(name string) bool {
+	for i, section := range d.Sections {
+		if strings.EqualFold(section.Name, name) {
+			d.Sections = append(d.Sections[:i], d.Sections[i+1:]...)
+			return true
+		}
+	}
+	return false
+}
+
+func (d *Document) UpsertSection(section *Section) {
+	for i, existing := range d.Sections {
+		if strings.EqualFold(existing.Name, section.Name) {
+			d.Sections[i] = section
+			return
+		}
+	}
+	d.Sections = append(d.Sections, section)
+}
+
+func (d *Document) Serialize() string {
+	var b strings.Builder
+	for _, line := range d.Preamble {
+		b.WriteString(line)
+		b.WriteString("\n")
+	}
+
+	if len(d.Preamble) > 0 && len(d.Sections) > 0 {
+		b.WriteString("\n")
+	}
+
+	for i, section := range d.Sections {
+		b.WriteString(fmt.Sprintf("[%s]\n", section.Name))
+		for _, line := range section.Lines {
+			if line.IsKV {
+				if line.Disabled {
+					b.WriteString(fmt.Sprintf("# %s = %s\n", line.Key, line.Value))
+				} else {
+					b.WriteString(fmt.Sprintf("    %s = %s\n", line.Key, line.Value))
+				}
+				continue
+			}
+
+			b.WriteString(line.Raw)
+			b.WriteString("\n")
+		}
+
+		if i < len(d.Sections)-1 {
+			b.WriteString("\n")
+		}
+	}
+
+	return b.String()
+}
+
+type ShareConfig struct {
+	Name       string
+	Path       string
+	Comment    string
+	Browseable string
+	ReadOnly   string
+	GuestOK    string
+	ValidUsers []string
+}
+
+func ShareFromSection(section *Section) ShareConfig {
+	cfg := ShareConfig{
+		Name:       section.Name,
+		Browseable: "yes",
+		ReadOnly:   "no",
+		GuestOK:    "no",
+	}
+
+	for _, line := range section.Lines {
+		if !line.IsKV || line.Disabled {
+			continue
+		}
+
+		switch line.Key {
+		case "path":
+			cfg.Path = line.Value
+		case "comment":
+			cfg.Comment = line.Value
+		case "browseable", "browsable":
+			cfg.Browseable = line.Value
+		case "read only", "readonly":
+			cfg.ReadOnly = line.Value
+		case "guest ok":
+			cfg.GuestOK = line.Value
+		case "valid users":
+			cfg.ValidUsers = splitUsers(line.Value)
+		}
+	}
+
+	return cfg
+}
+
+func BuildShareSection(existing *Section, cfg ShareConfig) *Section {
+	var lines []Line
+	if existing != nil {
+		lines = slices.Clone(existing.Lines)
+	} else {
+		lines = []Line{}
+	}
+
+	section := &Section{
+		Name:  cfg.Name,
+		Lines: lines,
+	}
+
+	section.SetValue("path", cfg.Path)
+	if cfg.Comment != "" {
+		section.SetValue("comment", cfg.Comment)
+	} else {
+		section.DeleteValue("comment")
+	}
+	section.SetValue("browseable", normalizeBoolish(cfg.Browseable, "yes"))
+	section.SetValue("read only", normalizeBoolish(cfg.ReadOnly, "no"))
+	section.SetValue("guest ok", normalizeBoolish(cfg.GuestOK, "no"))
+	if len(cfg.ValidUsers) > 0 {
+		section.SetValue("valid users", strings.Join(cfg.ValidUsers, ", "))
+	} else {
+		section.DeleteValue("valid users")
+	}
+
+	return section
+}
+
+func (s *Section) SetValue(key, value string) {
+	canonical := strings.ToLower(strings.TrimSpace(key))
+	for i, line := range s.Lines {
+		if line.IsKV && line.Key == canonical {
+			s.Lines[i].Value = value
+			s.Lines[i].Disabled = false
+			return
+		}
+	}
+
+	s.Lines = append(s.Lines, Line{
+		Key:   canonical,
+		Value: value,
+		IsKV:  true,
+	})
+}
+
+func (s *Section) DeleteValue(key string) {
+	canonical := strings.ToLower(strings.TrimSpace(key))
+	dst := s.Lines[:0]
+	for _, line := range s.Lines {
+		if line.IsKV && line.Key == canonical {
+			continue
+		}
+		dst = append(dst, line)
+	}
+	s.Lines = dst
+}
+
+func splitUsers(raw string) []string {
+	fields := strings.FieldsFunc(raw, func(r rune) bool {
+		return r == ',' || r == ' ' || r == '\t'
+	})
+
+	var users []string
+	for _, field := range fields {
+		field = strings.TrimSpace(field)
+		if field != "" {
+			users = append(users, field)
+		}
+	}
+	return users
+}
+
+func normalizeBoolish(value, fallback string) string {
+	switch strings.ToLower(strings.TrimSpace(value)) {
+	case "yes", "true", "1":
+		return "yes"
+	case "no", "false", "0":
+		return "no"
+	case "":
+		return fallback
+	default:
+		return value
+	}
+}
diff --git a/parser_test.go b/parser_test.go
new file mode 100644
index 0000000..13cf2ff
--- /dev/null
+++ b/parser_test.go
@@ -0,0 +1,96 @@
+package main
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestParseConfigFindsShares(t *testing.T) {
+	doc, err := ParseConfig(`
+# comment
+[global]
+    workgroup = WORKGROUP
+
+[media]
+    path = /srv/media
+    valid users = alice, bob
+    guest ok = no
+`)
+	if err != nil {
+		t.Fatalf("ParseConfig() error = %v", err)
+	}
+
+	shares := doc.ShareSections()
+	if len(shares) != 1 {
+		t.Fatalf("expected 1 share, got %d", len(shares))
+	}
+
+	cfg := ShareFromSection(shares[0])
+	if cfg.Name != "media" {
+		t.Fatalf("expected share name media, got %q", cfg.Name)
+	}
+	if cfg.Path != "/srv/media" {
+		t.Fatalf("expected path /srv/media, got %q", cfg.Path)
+	}
+	if strings.Join(cfg.ValidUsers, ",") != "alice,bob" {
+		t.Fatalf("expected users alice,bob, got %v", cfg.ValidUsers)
+	}
+}
+
+func TestBuildShareSectionUpdatesValues(t *testing.T) {
+	section := &Section{
+		Name: "public",
+		Lines: []Line{
+			{Key: "path", Value: "/old", IsKV: true},
+			{Key: "comment", Value: "old", IsKV: true},
+		},
+	}
+
+	updated := BuildShareSection(section, ShareConfig{
+		Name:       "public",
+		Path:       "/srv/public",
+		Comment:    "",
+		Browseable: "yes",
+		ReadOnly:   "no",
+		GuestOK:    "yes",
+		ValidUsers: []string{"alice"},
+	})
+
+	cfg := ShareFromSection(updated)
+	if cfg.Path != "/srv/public" {
+		t.Fatalf("expected updated path, got %q", cfg.Path)
+	}
+	if cfg.Comment != "" {
+		t.Fatalf("expected comment removed, got %q", cfg.Comment)
+	}
+	if strings.Join(cfg.ValidUsers, ",") != "alice" {
+		t.Fatalf("expected alice, got %v", cfg.ValidUsers)
+	}
+}
+
+func TestSerializeProducesSectionHeaders(t *testing.T) {
+	doc := &Document{
+		Preamble: []string{"# smb.conf"},
+		Sections: []*Section{
+			BuildShareSection(nil, ShareConfig{
+				Name:       "docs",
+				Path:       "/srv/docs",
+				Browseable: "yes",
+				ReadOnly:   "no",
+				GuestOK:    "no",
+			}),
+		},
+	}
+
+	out := doc.Serialize()
+	for _, want := range []string{
+		"# smb.conf",
+		"[docs]",
+		"path = /srv/docs",
+		"browseable = yes",
+	} {
+		if !strings.Contains(out, want) {
+			t.Fatalf("serialized output missing %q:\n%s", want, out)
+		}
+	}
+}
diff --git a/samba-configer b/samba-configer
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