package group

import (
	"encoding/json"
	"errors"
	"fmt"
	"io/fs"
	"log"
	"net/url"
	"os"
	"path"
	"path/filepath"
	"sort"
	"strings"
	"sync"
	"time"

	"github.com/pion/ice/v2"
	"github.com/pion/sdp/v3"
	"github.com/pion/webrtc/v3"

	"github.com/jech/galene/token"
)

var Directory, DataDirectory string
var UseMDNS bool
var UDPMin, UDPMax uint16

type NotAuthorisedError struct {
	err error
}

func (err *NotAuthorisedError) Error() string {
	if err.err != nil {
		return "not authorised: " + err.err.Error()
	}
	return "not authorised"
}
func (err *NotAuthorisedError) Unwrap() error {
	return err.err
}

var ErrDuplicateUsername = &NotAuthorisedError{
	errors.New("this username is taken"),
}

type UserError string

func (err UserError) Error() string {
	return string(err)
}

type KickError struct {
	Id       string
	Username *string
	Message  string
}

func (err KickError) Error() string {
	m := "kicked out"
	if err.Message != "" {
		m += " (" + err.Message + ")"
	}
	if err.Username != nil && *err.Username != "" {
		m += " by " + *err.Username
	}
	return m
}

type ProtocolError string

func (err ProtocolError) Error() string {
	return string(err)
}

type ChatHistoryEntry struct {
	Id     string
	Source string
	User   *string
	Time   time.Time
	Kind   string
	Value  interface{}
}

const (
	LowBitrate = 100 * 1024
	MinBitrate = LowBitrate * 2
	MaxBitrate = 1024 * 1024 * 1024
)

type Group struct {
	name string

	mu          sync.Mutex
	description *Description
	locked      *string
	clients     map[string]Client
	history     []ChatHistoryEntry
	timestamp   time.Time
	data        map[string]interface{}
}

func (g *Group) Name() string {
	return g.name
}

func (g *Group) Locked() (bool, string) {
	g.mu.Lock()
	defer g.mu.Unlock()
	if g.locked != nil {
		return true, *g.locked
	} else {
		return false, ""
	}
}

func (g *Group) SetLocked(locked bool, message string) {
	g.mu.Lock()
	if locked {
		g.locked = &message
	} else {
		g.locked = nil
	}
	clients := g.getClientsUnlocked(nil)
	g.mu.Unlock()

	for _, c := range clients {
		c.Joined(g.Name(), "change")
	}
}

func (g *Group) Data() map[string]interface{} {
	g.mu.Lock()
	defer g.mu.Unlock()
	return g.data
}

func (g *Group) UpdateData(d map[string]interface{}) {
	g.mu.Lock()
	if g.data == nil {
		g.data = make(map[string]interface{})
	}
	for k, v := range d {
		if v == nil {
			delete(g.data, k)
		} else {
			g.data[k] = v
		}
	}
	clients := g.getClientsUnlocked(nil)
	g.mu.Unlock()

	for _, c := range clients {
		c.Joined(g.Name(), "change")
	}
}

func (g *Group) Description() *Description {
	g.mu.Lock()
	defer g.mu.Unlock()
	return g.description
}

func (g *Group) ClientCount() int {
	g.mu.Lock()
	defer g.mu.Unlock()
	return len(g.clients)
}

func (g *Group) mayExpire() bool {
	g.mu.Lock()
	defer g.mu.Unlock()

	if g.description.Public {
		return false
	}
	if len(g.clients) > 0 {
		return false
	}
	return time.Since(g.timestamp) > maxHistoryAge(g.description)
}

var groups struct {
	mu     sync.Mutex
	groups map[string]*Group
}

func (g *Group) API() (*webrtc.API, error) {
	g.mu.Lock()
	codecs := g.description.Codecs
	g.mu.Unlock()

	return APIFromNames(codecs)
}

func fmtpValue(fmtp, key string) string {
	fields := strings.Split(fmtp, ";")
	for _, f := range fields {
		k, v, found := strings.Cut(f, "=")
		if found && k == key {
			return v
		}
	}
	return ""
}

func CodecPayloadType(codec webrtc.RTPCodecCapability) (webrtc.PayloadType, error) {
	switch strings.ToLower(codec.MimeType) {
	case "video/vp8":
		return 96, nil
	case "video/vp9":
		profile := fmtpValue(codec.SDPFmtpLine, "profile-id")
		switch profile {
		case "", "0":
			return 98, nil
		case "2":
			return 100, nil
		default:
			return 0, fmt.Errorf("unknown VP9 profile %v", profile)

		}
	case "video/av1":
		return 35, nil
	case "video/h264":
		profile := fmtpValue(codec.SDPFmtpLine, "profile-level-id")
		if profile == "" {
			return 102, nil
		}
		if len(profile) < 4 {
			return 0, errors.New("malforned H.264 profile")
		}
		switch strings.ToLower(profile[:4]) {
		case "4200":
			return 102, nil
		case "42e0":
			return 108, nil
		default:
			return 0, fmt.Errorf(
				"unknown H.264 profile %v", profile,
			)
		}
	case "audio/opus":
		return 111, nil
	case "audio/g722":
		return 9, nil
	case "audio/pcmu":
		return 0, nil
	case "audio/pcma":
		return 8, nil
	default:
		return 0, fmt.Errorf("unknown codec %v", codec.MimeType)
	}
}

func codecsFromName(name string) ([]webrtc.RTPCodecParameters, error) {
	fb := []webrtc.RTCPFeedback{
		{"goog-remb", ""},
		{"nack", ""},
		{"nack", "pli"},
		{"ccm", "fir"},
	}

	var codecs []webrtc.RTPCodecCapability

	switch name {
	case "vp8":
		codecs = []webrtc.RTPCodecCapability{
			{
				"video/VP8", 90000, 0,
				"",
				fb,
			},
		}
	case "vp9":
		codecs = []webrtc.RTPCodecCapability{
			{
				"video/VP9", 90000, 0,
				"profile-id=0",
				fb,
			},
			{
				"video/VP9", 90000, 0,
				"profile-id=2",
				fb,
			},
		}
	case "av1":
		codecs = []webrtc.RTPCodecCapability{
			{
				"video/AV1", 90000, 0,
				"",
				fb,
			},
		}
	case "h264":
		codecs = []webrtc.RTPCodecCapability{
			{
				"video/H264", 90000, 0,
				"level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f",
				fb,
			},
		}
	case "opus":
		codecs = []webrtc.RTPCodecCapability{
			{
				"audio/opus", 48000, 2,
				"minptime=10;useinbandfec=1;stereo=1;sprop-stereo=1",
				nil,
			},
		}
	case "g722":
		codecs = []webrtc.RTPCodecCapability{
			{
				"audio/G722", 8000, 1,
				"",
				nil,
			},
		}
	case "pcmu":
		codecs = []webrtc.RTPCodecCapability{
			{
				"audio/PCMU", 8000, 1,
				"",
				nil,
			},
		}
	case "pcma":
		codecs = []webrtc.RTPCodecCapability{
			{
				"audio/PCMU", 8000, 1,
				"",
				nil,
			},
		}
	default:
		return nil, errors.New("unknown codec")
	}

	parms := make([]webrtc.RTPCodecParameters, 0, len(codecs))
	for _, c := range codecs {
		ptype, err := CodecPayloadType(c)
		if err != nil {
			log.Printf("Couldn't determine ptype for codec %v: %v",
				c.MimeType, err)
			continue
		}
		parms = append(parms, webrtc.RTPCodecParameters{
			RTPCodecCapability: c,
			PayloadType:        ptype,
		})
	}
	return parms, nil
}

func APIFromCodecs(codecs []webrtc.RTPCodecParameters) (*webrtc.API, error) {
	s := webrtc.SettingEngine{}
	s.SetSRTPReplayProtectionWindow(512)
	s.DisableActiveTCP(true)
	if !UseMDNS {
		s.SetICEMulticastDNSMode(ice.MulticastDNSModeDisabled)
	}
	m := webrtc.MediaEngine{}

	for _, codec := range codecs {
		tpe := webrtc.RTPCodecTypeVideo
		if strings.HasPrefix(strings.ToLower(codec.MimeType), "audio/") {
			tpe = webrtc.RTPCodecTypeAudio
		}
		err := m.RegisterCodec(codec, tpe)
		if err != nil {
			log.Printf("%v", err)
			continue
		}
	}

	if UDPMin > 0 && UDPMax > 0 {
		s.SetEphemeralUDPPortRange(UDPMin, UDPMax)
	}
	m.RegisterHeaderExtension(
		webrtc.RTPHeaderExtensionCapability{sdp.SDESMidURI},
		webrtc.RTPCodecTypeVideo)
	m.RegisterHeaderExtension(
		webrtc.RTPHeaderExtensionCapability{sdp.SDESRTPStreamIDURI},
		webrtc.RTPCodecTypeVideo)

	return webrtc.NewAPI(
		webrtc.WithSettingEngine(s),
		webrtc.WithMediaEngine(&m),
	), nil
}

func APIFromNames(names []string) (*webrtc.API, error) {
	if len(names) == 0 {
		names = []string{"vp8", "opus"}
	}
	var codecs []webrtc.RTPCodecParameters
	for _, n := range names {
		cs, err := codecsFromName(n)
		if err != nil {
			log.Printf("Codec %v: %v", n, err)
			continue
		}
		codecs = append(codecs, cs...)
	}

	return APIFromCodecs(codecs)
}

func Add(name string, desc *Description) (*Group, error) {
	g, notify, err := add(name, desc)
	for _, c := range notify {
		c.Joined(g.Name(), "change")
	}
	return g, err
}

func validGroupName(name string) bool {
	if filepath.Separator != '/' &&
		strings.ContainsRune(name, filepath.Separator) {
		return false
	}

	s := path.Clean("/" + name)
	if s == "/" {
		return false
	}

	return s == "/"+name
}

func add(name string, desc *Description) (*Group, []Client, error) {
	if !validGroupName(name) {
		return nil, nil, UserError("illegal group name")
	}

	groups.mu.Lock()
	defer groups.mu.Unlock()

	if groups.groups == nil {
		groups.groups = make(map[string]*Group)
	}

	var err error

	g := groups.groups[name]
	if g == nil {
		if desc == nil {
			desc, err = readDescription(name, true)
			if err != nil {
				return nil, nil, err
			}
		}

		g = &Group{
			name:        name,
			description: desc,
			clients:     make(map[string]Client),
			timestamp:   time.Now(),
		}
		groups.groups[name] = g
	}

	g.mu.Lock()
	defer g.mu.Unlock()

	notify := false
	if desc != nil {
		if !descriptionMatch(g.description, desc) {
			g.description = desc
			notify = true
		}
	} else if !descriptionUnchanged(name, g.description) {
		desc, err = readDescription(name, true)
		if err != nil {
			if !errors.Is(err, os.ErrNotExist) {
				log.Printf("Reading group %v: %v", name, err)
			}
			deleteUnlocked(g)
			return nil, nil, err
		}
		g.description = desc
		notify = true
	}

	autoLockKick(g)

	var clients []Client
	if notify {
		clients = g.getClientsUnlocked(nil)
	}
	return g, clients, nil
}

func Range(f func(g *Group) bool) {
	groups.mu.Lock()
	defer groups.mu.Unlock()

	for _, g := range groups.groups {
		ok := f(g)
		if !ok {
			break
		}
	}
}

func GetNames() []string {
	names := make([]string, 0)

	Range(func(g *Group) bool {
		names = append(names, g.name)
		return true
	})
	return names
}

type SubGroup struct {
	Name    string
	Clients int
}

func GetSubGroups(parent string) []SubGroup {
	prefix := parent + "/"
	subgroups := make([]SubGroup, 0)

	Range(func(g *Group) bool {
		if strings.HasPrefix(g.name, prefix) {
			g.mu.Lock()
			count := len(g.clients)
			g.mu.Unlock()
			if count > 0 {
				subgroups = append(subgroups,
					SubGroup{g.name, count})
			}
		}
		return true
	})
	return subgroups
}

func Get(name string) *Group {
	groups.mu.Lock()
	defer groups.mu.Unlock()
	if groups.groups == nil {
		return nil
	}
	return groups.groups[name]
}

func Delete(name string) bool {
	groups.mu.Lock()
	defer groups.mu.Unlock()
	g := groups.groups[name]
	if g == nil {
		return false
	}

	g.mu.Lock()
	defer g.mu.Unlock()
	return deleteUnlocked(g)
}

// Called with both groups.mu and g.mu taken.
func deleteUnlocked(g *Group) bool {
	if len(g.clients) != 0 {
		return false
	}

	delete(groups.groups, g.name)
	return true
}

func member(v string, l []string) bool {
	for _, w := range l {
		if v == w {
			return true
		}
	}
	return false
}

func AddClient(group string, c Client, creds ClientCredentials) (*Group, error) {
	g, err := Add(group, nil)
	if err != nil {
		return nil, err
	}

	g.mu.Lock()
	defer g.mu.Unlock()

	clients := g.getClientsUnlocked(nil)

	if !member("system", c.Permissions()) {
		username, perms, err := g.getPermission(creds)
		if err != nil {
			return nil, err
		}

		c.SetUsername(username)
		c.SetPermissions(perms)

		if !member("op", perms) {
			if g.locked != nil {
				m := *g.locked
				if m == "" {
					m = "this group is locked"
				}
				return nil, UserError(m)
			}
			if g.description.NotBefore != nil ||
				g.description.Expires != nil {
				now := time.Now()
				if g.description.NotBefore != nil &&
					g.description.NotBefore.After(now) {
					return nil, UserError(
						"this group is not open yet",
					)
				}
				if g.description.Expires != nil &&
					g.description.Expires.Before(now) {
					return nil, UserError(
						"this group is closed",
					)
				}
			}
			if g.description.Autokick {
				ops := false
				for _, c := range clients {
					if member("op", c.Permissions()) {
						ops = true
						break
					}
				}
				if !ops {
					return nil, UserError(
						"there are no operators " +
							"in this group",
					)
				}
			}
		}

		if !member("op", perms) && g.description.MaxClients > 0 {
			if len(g.clients) >= g.description.MaxClients {
				return nil, UserError("too many users")
			}
		}
	}
	id := c.Id()
	if id == "" {
		return nil, errors.New("client has empty id")
	}
	if g.clients[id] != nil {
		return nil, ProtocolError("duplicate client id")
	}
	g.clients[id] = c
	g.timestamp = time.Now()

	c.Joined(g.Name(), "join")

	u := c.Username()
	p := c.Permissions()
	s := c.Data()
	c.PushClient(g.Name(), "add", c.Id(), u, p, s)
	for _, cc := range clients {
		pp := cc.Permissions()
		uu := cc.Username()
		c.PushClient(g.Name(), "add", cc.Id(), uu, pp, cc.Data())
		cc.PushClient(g.Name(), "add", id, u, p, s)
	}

	return g, nil
}

// called locked
func autoLockKick(g *Group) {
	if !(g.description.Autolock && g.locked == nil) &&
		!g.description.Autokick {
		return
	}

	clients := g.getClientsUnlocked(nil)
	for _, c := range clients {
		if member("op", c.Permissions()) {
			return
		}
	}
	if g.description.Autolock && g.locked == nil {
		m := "this group is locked"
		g.locked = &m
		for _, c := range clients {
			c.Joined(g.Name(), "change")
		}
	}

	if g.description.Autokick {
		// we cannot call kickall, since it requires the group to
		// be unlocked.  And calling it asynchronously might
		// spuriously kick out an operator.
		go func(clients []Client) {
			for _, c := range clients {
				c.Kick(
					"", nil,
					"there are no operators in this group",
				)
			}
		}(g.getClientsUnlocked(nil))
	}
}

func DelClient(c Client) {
	g := c.Group()
	if g == nil {
		return
	}
	g.mu.Lock()
	if g.clients[c.Id()] != c {
		log.Printf("Deleting unknown client")
		g.mu.Unlock()
		return
	}
	delete(g.clients, c.Id())
	g.timestamp = time.Now()
	clients := g.getClientsUnlocked(nil)
	g.mu.Unlock()

	c.Joined(g.Name(), "leave")
	for _, cc := range clients {
		cc.PushClient(
			g.Name(), "delete", c.Id(), c.Username(), nil, nil,
		)
	}
	autoLockKick(g)
}

func (g *Group) GetClients(except Client) []Client {
	g.mu.Lock()
	defer g.mu.Unlock()
	return g.getClientsUnlocked(except)
}

func (g *Group) getClientsUnlocked(except Client) []Client {
	clients := make([]Client, 0, len(g.clients))
	for _, c := range g.clients {
		if c != except {
			clients = append(clients, c)
		}
	}
	return clients
}

func (g *Group) GetClient(id string) Client {
	g.mu.Lock()
	defer g.mu.Unlock()
	return g.getClientUnlocked(id)
}

func (g *Group) getClientUnlocked(id string) Client {
	for idd, c := range g.clients {
		if idd == id {
			return c
		}
	}
	return nil
}

func (g *Group) Range(f func(c Client) bool) {
	g.mu.Lock()
	defer g.mu.Unlock()
	for _, c := range g.clients {
		ok := f(c)
		if !ok {
			break
		}
	}
}

func kickall(g *Group, message string) {
	g.Range(func(c Client) bool {
		c.Kick("", nil, message)
		return true
	})
}

func Shutdown(message string) {
	Range(func(g *Group) bool {
		g.SetLocked(true, message)
		kickall(g, message)
		return true
	})
}

type warner interface {
	Warn(oponly bool, message string) error
}

func (g *Group) WallOps(message string) {
	clients := g.GetClients(nil)
	for _, c := range clients {
		w, ok := c.(warner)
		if !ok {
			continue
		}
		err := w.Warn(true, message)
		if err != nil {
			log.Printf("WallOps: %v", err)
		}
	}
}

const maxChatHistory = 50

// deleteFunc is just like slices.DeleteFunc.
// Remove this once we require Go 1.21.
func deleteFunc[S ~[]E, E any](s S, f func(E) bool) S {
	i := 0
	for i = range s {
		if f(s[i]) {
			break
		}
	}
	if i >= len(s) {
		return s
	}

	for j := i + 1; j < len(s); j++ {
		if v := s[j]; !f(v) {
			s[i] = v
			i++
		}
	}
	var zero E
	for j := i; j < len(s); j++ {
		s[j] = zero
	}
	return s[:i]
}

func (g *Group) ClearChatHistory(id string, userId string) {
	g.mu.Lock()
	defer g.mu.Unlock()
	if id == "" && userId == "" {
		g.history = nil
		return
	}
	g.history = deleteFunc(g.history, func(e ChatHistoryEntry) bool {
		return e.Source == userId && (id == "" || e.Id == id)
	})
}

func (g *Group) AddToChatHistory(id, source string, user *string, time time.Time, kind string, value interface{}) {
	g.mu.Lock()
	defer g.mu.Unlock()

	if len(g.history) >= maxChatHistory {
		copy(g.history, g.history[1:])
		g.history = g.history[:len(g.history)-1]
	}
	g.history = append(g.history,
		ChatHistoryEntry{Id: id, Source: source, User: user, Time: time, Kind: kind, Value: value},
	)
}

func discardObsoleteHistory(h []ChatHistoryEntry, duration time.Duration) []ChatHistoryEntry {
	i := 0
	for i < len(h) {
		if time.Since(h[i].Time) <= duration {
			break
		}
		i++
	}
	if i > 0 {
		copy(h, h[i:])
		h = h[:len(h)-i]
	}
	return h
}

func (g *Group) GetChatHistory() []ChatHistoryEntry {
	g.mu.Lock()
	defer g.mu.Unlock()

	g.history = discardObsoleteHistory(
		g.history, maxHistoryAge(g.description),
	)

	h := make([]ChatHistoryEntry, len(g.history))
	copy(h, g.history)
	return h
}

// Configuration represents the contents of the data/config.json file.
type Configuration struct {
	// The modtime and size of the file.  These are used to detect
	// when a file has changed on disk.
	modTime  time.Time `json:"-"`
	fileSize int64     `json:"-"`

	PublicServer   bool   `json:"publicServer"`
	CanonicalHost  string `json:"canonicalHost"`
	ProxyURL       string `json:"proxyURL"`
	WritableGroups bool   `json:"writableGroups"`
	Users          map[string]UserDescription

	// obsolete fields
	Admin []ClientPattern `json:"admin"`
}

func (conf Configuration) Zero() bool {
	return conf.modTime.Equal(time.Time{}) &&
		conf.fileSize == 0
}

var configuration struct {
	mu            sync.Mutex
	configuration *Configuration
}

func GetConfiguration() (*Configuration, error) {
	configuration.mu.Lock()
	defer configuration.mu.Unlock()

	if configuration.configuration == nil {
		configuration.configuration = &Configuration{}
	}

	filename := filepath.Join(DataDirectory, "config.json")
	fi, err := os.Stat(filename)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			if !configuration.configuration.Zero() {
				configuration.configuration = &Configuration{}
			}
			return configuration.configuration, nil
		}
		return nil, err
	}

	if configuration.configuration.modTime.Equal(fi.ModTime()) &&
		configuration.configuration.fileSize == fi.Size() {
		return configuration.configuration, nil
	}

	f, err := os.Open(filename)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	d := json.NewDecoder(f)
	d.DisallowUnknownFields()
	var conf Configuration
	err = d.Decode(&conf)
	if err != nil {
		return nil, err
	}
	if conf.Admin != nil {
		log.Printf("%v: field \"admin\" is obsolete, ignored", filename)
		conf.Admin = nil
	}
	configuration.configuration = &conf
	return configuration.configuration, nil
}

// called locked
func (g *Group) getPasswordPermission(creds ClientCredentials) (Permissions, error) {
	desc := g.description

	if creds.Username == nil {
		return Permissions{}, errors.New("username not provided")
	}
	if desc.Users != nil {
		if c, found := desc.Users[*creds.Username]; found {
			ok, err := c.Password.Match(creds.Password)
			if err != nil {
				return Permissions{}, err
			}
			if ok {
				return c.Permissions, nil
			} else {
				return Permissions{}, &NotAuthorisedError{}
			}
		}
	}

	if desc.WildcardUser != nil {
		ok, _ := desc.WildcardUser.Password.Match(creds.Password)
		if ok {
			return desc.WildcardUser.Permissions, nil
		}
	}
	return Permissions{}, &NotAuthorisedError{}
}

// Return true if there is a user entry with the given username.
// Always return false for an empty username.
func (g *Group) UserExists(username string) bool {
	g.mu.Lock()
	defer g.mu.Unlock()
	return g.userExists(username)
}

// called locked
func (g *Group) userExists(username string) bool {
	desc := g.description
	if desc.Users == nil {
		return false
	}
	_, found := desc.Users[username]
	return found
}

// called locked
func (g *Group) getPermission(creds ClientCredentials) (string, []string, error) {
	desc := g.description
	var username string
	var perms []string
	if creds.Token != "" {
		tok, err := token.Parse(creds.Token, desc.AuthKeys)
		if err != nil {
			return "", nil, &NotAuthorisedError{err: err}
		}

		conf, err := GetConfiguration()
		if err != nil {
			return "", nil, err
		}

		username, perms, err =
			tok.Check(conf.CanonicalHost, g.name, creds.Username)
		if err != nil {
			return "", nil, &NotAuthorisedError{err: err}
		}
		if username == "" && creds.Username != nil {
			if g.userExists(*creds.Username) {
				return "", nil, ErrDuplicateUsername
			}
			username = *creds.Username
		}
	} else if creds.Username != nil {
		username = *creds.Username
		ps, err := g.getPasswordPermission(creds)
		if err != nil {
			return "", nil, err
		}
		perms = ps.Permissions(desc)
	} else {
		return "", nil, errors.New("neither username nor token provided")
	}

	return username, perms, nil
}

func (g *Group) GetPermission(creds ClientCredentials) (string, []string, error) {
	g.mu.Lock()
	defer g.mu.Unlock()
	return g.getPermission(creds)
}

type Status struct {
	Name              string `json:"name"`
	Redirect          string `json:"redirect,omitempty"`
	Location          string `json:"location,omitempty"`
	Endpoint          string `json:"endpoint,omitempty"`
	DisplayName       string `json:"displayName,omitempty"`
	Description       string `json:"description,omitempty"`
	AuthServer        string `json:"authServer,omitempty"`
	AuthPortal        string `json:"authPortal,omitempty"`
	Locked            bool   `json:"locked,omitempty"`
	ClientCount       *int   `json:"clientCount,omitempty"`
	CanChangePassword bool   `json:"canChangePassword,omitempty"`
}

// Status returns a group's status.
// Base is the base URL for groups; if omitted, then both the Location and
// Endpoint members are omitted from the result.
func (g *Group) Status(authentified bool, base *url.URL) Status {
	desc := g.Description()

	if desc.Redirect != "" {
		return Status{
			Name:        g.name,
			Redirect:    desc.Redirect,
			DisplayName: desc.DisplayName,
			Description: desc.Description,
		}
	}

	var location, endpoint string
	if base != nil {
		wss := "wss"
		if base.Scheme == "http" {
			wss = "ws"
		}
		l := url.URL{
			Scheme: base.Scheme,
			Host:   base.Host,
			Path: path.Join(
				path.Join(base.Path, "/group/"),
				g.Name()) + "/",
		}
		location = l.String()
		e := url.URL{
			Scheme: wss,
			Host:   base.Host,
			Path:   path.Join(base.Path, "/ws"),
		}
		endpoint = e.String()
	}

	d := Status{
		Name:        g.name,
		Location:    location,
		Endpoint:    endpoint,
		DisplayName: desc.DisplayName,
		AuthServer:  desc.AuthServer,
		AuthPortal:  desc.AuthPortal,
		Description: desc.Description,
	}

	if authentified || desc.Public {
		// these are considered private information
		locked, _ := g.Locked()
		count := g.ClientCount()
		d.Locked = locked
		d.ClientCount = &count
	}
	if authentified {
		conf, err := GetConfiguration()
		if err == nil {
			d.CanChangePassword = conf.WritableGroups
		}
	}
	return d
}

func GetPublic(base *url.URL) []Status {
	gs := make([]Status, 0)
	Range(func(g *Group) bool {
		if g.Description().Public {
			gs = append(gs, g.Status(false, base))
		}
		return true
	})
	sort.Slice(gs, func(i, j int) bool {
		return gs[i].Name < gs[j].Name
	})
	return gs
}

// Update checks that all in-memory groups are up-to-date and updates the
// list of public groups.  It also removes from memory any non-public
// groups that haven't been accessed in maxHistoryAge.
func Update() {
	_, err := GetConfiguration()
	if err != nil {
		log.Printf("%v: %v",
			filepath.Join(DataDirectory, "config.json"),
			err,
		)
	}

	names := GetNames()
	for _, name := range names {
		g := Get(name)
		if g == nil {
			continue
		}

		deleted := false
		if g.mayExpire() {
			// Delete checks if the group is still empty
			deleted = Delete(name)
		}

		// update group description
		if !deleted {
			Add(name, nil)
		}
	}

	err = filepath.WalkDir(
		Directory,
		func(path string, d fs.DirEntry, err error) error {
			if err != nil {
				log.Printf("Group file %v: %v", path, err)
				return nil
			}
			if d.IsDir() {
				base := filepath.Base(path)
				if base[0] == '.' {
					log.Printf(
						"Ignoring group directory %v",
						path,
					)
					return fs.SkipDir
				}
				return nil
			}
			filename, err := filepath.Rel(Directory, path)
			if err != nil {
				log.Printf("Group file %v: %v", path, err)
				return nil
			}
			if !strings.HasSuffix(filename, ".json") {
				log.Printf(
					"Unexpected extension for group file %v",
					path,
				)
				return nil
			}
			base := filepath.Base(filename)
			if base[0] == '.' {
				log.Printf("Ignoring group file %v", filename)
				return nil
			}
			name := strings.TrimSuffix(filename, ".json")
			desc, err := GetDescription(name)
			if err != nil {
				log.Printf("Group file %v: %v", path, err)
				return nil
			}
			if desc.Public {
				Add(name, desc)
			}
			return nil
		},
	)

	if err != nil {
		log.Printf("Couldn't read groups: %v", err)
	}
}