package main

// Locale, time zone and console keymap as one module (novox/hq to-be 42 Phase 1, research 027/02:
// the operator's choice of one module for the three). Measured on 2026-10-04, three machines had
// en_US.UTF-8, Europe/Brussels and no keymap, and one had another zone and a German keymap with no
// record why; the module brings every machine to the first.
//
// The locale and the keymap are files the host writes whole. The time zone is not a file the mesh
// may write: /etc/localtime is a symbolic link into the zone database, and the mesh creates no
// symbolic links (ADR 0012). Writing a copy of the zone there instead would leave every tool that
// reads the zone's name from the link (timedatectl among them) answering "n/a", and a module may not
// declare an action (ADR 0005). So the module's own binary is run once by the host, as root, as a
// step (`set-time-zone`, below): it asks the service manager's time daemon to set the zone, which
// makes the distribution's own link — the mesh writes none — and reads it back.

import (
	"fmt"
	"os"
	"regexp"
	"sort"
	"strings"
)

// What the module declares: its manifest's files and its step's argument, held to these by a test.
const (
	MeshLang   = "en_US.UTF-8"
	MeshZone   = "Europe/Brussels"
	MeshKeymap = "us"
)

// Settings is the machine's locale, time zone and keymap as its own daemons report them.
type Settings struct {
	Locale        map[string]string `json:"locale"`
	Lang          string            `json:"lang"`
	LangGenerated bool              `json:"lang_generated"`
	TimeZone      string            `json:"time_zone"`
	LocalRTC      bool              `json:"rtc_in_local_time"`
	NTP           bool              `json:"ntp_enabled"`
	NTPSynced     bool              `json:"ntp_synchronized"`
	Keymap        string            `json:"console_keymap"`
	X11           map[string]string `json:"x11,omitempty"`
	// AsDeclared says, for each of the three, whether the machine is what the module declares.
	AsDeclared map[string]bool `json:"as_declared"`
}

// Get reads localectl and timedatectl, and whether the locale in force is generated.
func (m *Machine) Get() (Settings, error) {
	s := Settings{Locale: map[string]string{}, X11: map[string]string{}}
	out, err := m.Out("localectl", "status")
	if err != nil {
		return s, err
	}
	lc := ParseLocalectl(out)
	s.Locale, s.Keymap, s.X11 = lc.Locale, lc.Keymap, lc.X11
	s.Lang = s.Locale["LANG"]
	td, err := m.Out("timedatectl", "show")
	if err != nil {
		return s, err
	}
	kv := keyValues(td, "=")
	s.TimeZone = kv["Timezone"]
	s.LocalRTC = kv["LocalRTC"] == "yes"
	s.NTP = kv["NTP"] == "yes"
	s.NTPSynced = kv["NTPSynchronized"] == "yes"
	gen, err := m.Out("locale", "-a")
	if err != nil {
		return s, err
	}
	s.LangGenerated = generated(lines(gen), s.Lang)
	s.AsDeclared = map[string]bool{
		"locale":    s.Lang == MeshLang && s.LangGenerated,
		"time_zone": s.TimeZone == MeshZone,
		"keymap":    s.Keymap == MeshKeymap,
	}
	return s, nil
}

// Localectl is `localectl status` read: the system locale's variables, the console keymap and the
// X11 keyboard settings.
type Localectl struct {
	Locale map[string]string
	Keymap string
	X11    map[string]string
}

// ParseLocalectl reads `localectl status`. The locale's variables continue on lines of their own
// beneath its label; "(unset)" is said as empty.
func ParseLocalectl(out string) Localectl {
	l := Localectl{Locale: map[string]string{}, X11: map[string]string{}}
	label := ""
	for _, raw := range strings.Split(out, "\n") {
		line := strings.TrimSpace(raw)
		if line == "" {
			continue
		}
		value := line
		if k, v, ok := strings.Cut(line, ": "); ok && !strings.Contains(k, "=") {
			label, value = strings.TrimSpace(k), strings.TrimSpace(v)
		}
		if value == "(unset)" || value == "n/a" {
			value = ""
		}
		switch {
		case label == "System Locale":
			if k, v, ok := strings.Cut(value, "="); ok {
				l.Locale[k] = v
			}
		case label == "VC Keymap":
			l.Keymap = value
		case strings.HasPrefix(label, "X11 "):
			if value != "" {
				l.X11[strings.ToLower(strings.TrimPrefix(label, "X11 "))] = value
			}
		}
	}
	return l
}

// normal is a locale's name as glibc compares it: the codeset lowercased without dashes, so
// en_US.UTF-8 in a file and en_US.utf8 in `locale -a` are the same locale.
func normal(name string) string {
	lang, codeset, ok := strings.Cut(name, ".")
	if !ok {
		return name
	}
	mod := ""
	if c, at, found := strings.Cut(codeset, "@"); found {
		codeset, mod = c, "@"+at
	}
	return lang + "." + strings.ToLower(strings.ReplaceAll(codeset, "-", "")) + mod
}

func generated(have []string, want string) bool {
	if want == "" {
		return false
	}
	for _, h := range have {
		if normal(strings.TrimSpace(h)) == normal(want) {
			return true
		}
	}
	return false
}

// Zone is the time zone tool's answer.
type Zone struct {
	TimeZone string   `json:"time_zone"`
	Before   string   `json:"before,omitempty"`
	Changed  bool     `json:"changed"`
	Declared string   `json:"declared"`
	Zones    []string `json:"zones,omitempty"`
	Count    int      `json:"zones_matching,omitempty"`
	Note     string   `json:"note,omitempty"`
}

func (m *Machine) zone() (string, error) {
	out, err := m.Out("timedatectl", "show", "--property=Timezone", "--value")
	return strings.TrimSpace(out), err
}

func (m *Machine) zones() ([]string, error) {
	out, err := m.Out("timedatectl", "list-timezones")
	return lines(out), err
}

// TimeZone reads the zone, lists the zones matching a word, or sets one. Setting goes through the
// time daemon with sudo -n, which polkit would otherwise refuse to an account without a session.
func (m *Machine) TimeZone(set, match string) (Zone, error) {
	z := Zone{Declared: MeshZone}
	current, err := m.zone()
	if err != nil {
		return z, err
	}
	z.TimeZone = current
	if match != "" {
		all, err := m.zones()
		if err != nil {
			return z, err
		}
		for _, name := range all {
			if strings.Contains(strings.ToLower(name), strings.ToLower(match)) {
				z.Zones = append(z.Zones, name)
			}
		}
		z.Count = len(z.Zones)
		if len(z.Zones) > 200 {
			z.Zones = z.Zones[:200]
		}
	}
	if set == "" {
		return z, nil
	}
	all, err := m.zones()
	if err != nil {
		return z, err
	}
	if !contains(all, set) {
		return z, fmt.Errorf("%q is not a time zone this machine knows (timedatectl list-timezones)", set)
	}
	z.Before = current
	if set != current {
		if _, err := m.Root("timedatectl", "set-timezone", set); err != nil {
			return z, err
		}
		after, err := m.zone()
		if err != nil {
			return z, err
		}
		if after != set {
			return z, fmt.Errorf("the time zone was set to %s and reads back as %s", set, after)
		}
		z.TimeZone, z.Changed = after, true
	}
	if set != MeshZone {
		z.Note = fmt.Sprintf("the module declares %s; its step sets that zone again whenever the module's bundle changes", MeshZone)
	}
	return z, nil
}

func contains(list []string, want string) bool {
	for _, s := range list {
		if s == want {
			return true
		}
	}
	return false
}

// Locales is what this machine can, may and does use.
type Locales struct {
	Lang           string   `json:"lang"`
	LangGenerated  bool     `json:"lang_generated"`
	Generated      []string `json:"generated"`
	Enabled        []string `json:"enabled_in_locale_gen"`
	Available      []string `json:"available,omitempty"`
	AvailableCount int      `json:"available_count"`
}

// Locales reads `locale -a`, the uncommented lines of /etc/locale.gen, and the locales glibc can
// generate (/usr/share/i18n/SUPPORTED) — listed when a word narrows them, counted otherwise.
func (m *Machine) Locales(match string) (Locales, error) {
	l := Locales{Generated: []string{}, Enabled: []string{}}
	gen, err := m.Out("locale", "-a")
	if err != nil {
		return l, err
	}
	l.Generated = lines(gen)
	if conf, err := m.ReadFile("/etc/locale.conf"); err == nil {
		l.Lang = keyValues(string(conf), "=")["LANG"]
	} else if !os.IsNotExist(err) {
		return l, err
	}
	l.LangGenerated = generated(l.Generated, l.Lang)
	if gen, err := m.ReadFile("/etc/locale.gen"); err == nil {
		for _, line := range lines(string(gen)) {
			if line = strings.TrimSpace(line); !strings.HasPrefix(line, "#") {
				l.Enabled = append(l.Enabled, line)
			}
		}
	}
	supported, err := m.ReadFile("/usr/share/i18n/SUPPORTED")
	if err != nil && !os.IsNotExist(err) {
		return l, err
	}
	for _, line := range lines(string(supported)) {
		name := strings.Fields(line)[0]
		l.AvailableCount++
		if match != "" && strings.Contains(strings.ToLower(name), strings.ToLower(match)) {
			l.Available = append(l.Available, strings.TrimSpace(line))
		}
	}
	return l, nil
}

// Keymaps is the console keymaps this machine has.
type Keymaps struct {
	Current string   `json:"current"`
	Keymaps []string `json:"keymaps"`
	Count   int      `json:"count"`
}

var keymapName = regexp.MustCompile(`^[A-Za-z0-9_.+-]+$`)

// Keymaps lists `localectl list-keymaps`, narrowed to a word when one is given.
func (m *Machine) Keymaps(match string) (Keymaps, error) {
	k := Keymaps{Keymaps: []string{}}
	status, err := m.Out("localectl", "status")
	if err != nil {
		return k, err
	}
	k.Current = ParseLocalectl(status).Keymap
	out, err := m.Out("localectl", "list-keymaps", "--no-pager")
	if err != nil {
		return k, err
	}
	for _, name := range lines(out) {
		name = strings.TrimSpace(name)
		if !keymapName.MatchString(name) {
			continue
		}
		if match == "" || strings.Contains(strings.ToLower(name), strings.ToLower(match)) {
			k.Keymaps = append(k.Keymaps, name)
		}
	}
	sort.Strings(k.Keymaps)
	k.Count = len(k.Keymaps)
	if len(k.Keymaps) > 500 {
		k.Keymaps = k.Keymaps[:500]
	}
	return k, nil
}

// SetTimeZoneStep is the module's step, run once by the host as root: the zone set through the time
// daemon when it differs, and read back. It changes nothing on a machine already in the zone.
func (m *Machine) SetTimeZoneStep(zone string) (string, error) {
	if zone == "" || strings.HasPrefix(zone, "-") || strings.Contains(zone, "..") {
		return "", fmt.Errorf("%q is not a time zone", zone)
	}
	if _, err := m.ReadFile("/usr/share/zoneinfo/" + zone); err != nil {
		return "", fmt.Errorf("%s is not in this machine's zone database: %v", zone, err)
	}
	current, err := m.zone()
	if err != nil {
		return "", err
	}
	if current == zone {
		return fmt.Sprintf("the time zone is already %s", zone), nil
	}
	if _, err := m.Root("timedatectl", "set-timezone", zone); err != nil {
		return "", err
	}
	after, err := m.zone()
	if err != nil {
		return "", err
	}
	if after != zone {
		return "", fmt.Errorf("the time zone was set to %s and reads back as %s", zone, after)
	}
	return fmt.Sprintf("the time zone was %s and is now %s", current, zone), nil
}