telegabber/xmpp/handlers.go

package xmpp

import (
	"encoding/xml"
	"fmt"
	"github.com/pkg/errors"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	"dev.narayana.im/narayana/telegabber/persistence"
	"dev.narayana.im/narayana/telegabber/telegram"
	"dev.narayana.im/narayana/telegabber/xmpp/extensions"
	"dev.narayana.im/narayana/telegabber/xmpp/gateway"

	"github.com/google/uuid"
	log "github.com/sirupsen/logrus"
	"github.com/soheilhy/args"
	"gosrc.io/xmpp"
	"gosrc.io/xmpp/stanza"
)

const (
	TypeVCardTemp byte = iota
	TypeVCard4
)

const MUC_DEFAULT_HISTORY_LIMIT int32 = 20

// kludge for client resuming after the transport restart (by full jids)
var probeFired = make(map[string]bool)
var probeFiredLock = sync.Mutex{}

func logPacketType(p stanza.Packet) {
	log.Warnf("Ignoring packet: %T\n", p)
}

// HandleIq processes an incoming XMPP iq
func HandleIq(s xmpp.Sender, p stanza.Packet) {
	iq, ok := p.(*stanza.IQ)
	if !ok {
		logPacketType(p)
		return
	}

	log.Debugf("%#v", iq)
	if iq.Type == stanza.IQTypeGet {
		_, ok := iq.Payload.(*extensions.IqVcardTemp)
		if ok {
			go handleGetVcardIq(s, iq, TypeVCardTemp)
			return
		}
		pubsub, ok := iq.Payload.(*stanza.PubSubGeneric)
		if ok && pubsub.Items != nil {
			if pubsub.Items.Node == gateway.NodeVCard4 {
				go handleGetVcardIq(s, iq, TypeVCard4)
				return
			}
			if pubsub.Items.Node == gateway.NodeAvatarData {
				go handleGetAvatarDataIq(s, iq, pubsub)
				return
			}
		}
		discoInfo, ok := iq.Payload.(*stanza.DiscoInfo)
		if ok {
			go handleGetDiscoInfo(s, iq, discoInfo)
			return
		}
		discoItems, ok := iq.Payload.(*stanza.DiscoItems)
		if ok {
			go handleGetDiscoItems(s, iq, discoItems)
			return
		}
		_, ok = iq.Payload.(*extensions.QueryRegister)
		if ok {
			go handleGetQueryRegister(s, iq)
			return
		}
		queryMucAdmin, ok := iq.Payload.(*extensions.QueryMucAdmin)
		if ok {
			go handleGetQueryMucAdmin(s, iq, queryMucAdmin)
			return
		}
		_, ok = iq.Payload.(*extensions.QueryMucOwner)
		if ok {
			go handleGetQueryMucOwner(s, iq)
			return
		}
		queryMAM2, ok := iq.Payload.(*extensions.MAM2Query)
		if ok {
			go handleGetQueryMAM(s, iq, queryMAM2)
			return
		}
		queryMAM1, ok := iq.Payload.(*extensions.MAM1Query)
		if ok {
			go handleGetQueryMAM(s, iq, queryMAM1)
			return
		}
		queryMAM0, ok := iq.Payload.(*extensions.MAM0Query)
		if ok {
			go handleGetQueryMAM(s, iq, queryMAM0)
			return
		}
		_, ok = iq.Payload.(*extensions.MAM2Metadata)
		if ok {
			go handleGetMetadataMAM2(s, iq)
			return
		}
		_, ok = iq.Payload.(*stanza.Version)
		if ok {
			go handleGetVersion(s, iq)
			return
		}
		_, ok = iq.Payload.(*extensions.EntityTime)
		if ok {
			go handleGetEntityTime(s, iq)
			return
		}
	} else if iq.Type == stanza.IQTypeSet {
		queryRegister, ok := iq.Payload.(*extensions.QueryRegister)
		if ok {
			go handleSetQueryRegister(s, iq, queryRegister)
			return
		}
		command, ok := iq.Payload.(*stanza.Command)
		if ok {
			go handleSetQueryCommand(s, iq, command)
			return
		}
		queryMucAdmin, ok := iq.Payload.(*extensions.QueryMucAdmin)
		if ok {
			go handleSetQueryMucAdmin(s, iq, queryMucAdmin)
			return
		}
		queryMucOwner, ok := iq.Payload.(*extensions.QueryMucOwner)
		if ok {
			go handleSetQueryMucOwner(s, iq, queryMucOwner)
			return
		}
		queryMAM2, ok := iq.Payload.(*extensions.MAM2Query)
		if ok {
			go handleSetQueryMAM(s, iq, queryMAM2)
			return
		}
		queryMAM1, ok := iq.Payload.(*extensions.MAM1Query)
		if ok {
			go handleSetQueryMAM(s, iq, queryMAM1)
			return
		}
		queryMAM0, ok := iq.Payload.(*extensions.MAM0Query)
		if ok {
			go handleSetQueryMAM(s, iq, queryMAM0)
			return
		}
	} else if iq.Type == stanza.IQTypeResult {
		discoInfo, ok := iq.Payload.(*stanza.DiscoInfo)
		if ok {
			go handleClientFeatures(s, iq, discoInfo)
			return
		}
	}
}

// HandleMessage processes an incoming XMPP message
func HandleMessage(s xmpp.Sender, p stanza.Packet) {
	msg, ok := p.(stanza.Message)
	if !ok {
		logPacketType(p)
		return
	}

	component, ok := s.(*xmpp.Component)
	if !ok {
		log.Error("Not a component")
		return
	}

	if msg.Type != "error" && msg.Body != "" {
		log.WithFields(log.Fields{
			"from": msg.From,
			"to":   msg.To,
		}).Warn("Message")
		log.Debugf("%#v", msg)

		bare, resource, ok := gateway.SplitJID(msg.From)
		if !ok {
			return
		}

		gatewayJid := gateway.Jid.Bare()

		session, ok := sessions[bare]
		if !ok {
			if msg.To == gatewayJid {
				gateway.SubscribeToTransport(component, msg.From)
			} else {
				log.Error("Message from stranger")
			}
			return
		}

		toID, ok, toIsGroup := toToID(msg.To)
		if ok {
			toJid, err := stanza.NewJid(msg.To)
			if err != nil {
				log.Error("Invalid to JID!")
				return
			}

			isGroupchat := msg.Type == "groupchat"

			if session.Session.MUC {
				chat, _, err := session.GetContactByID(toID, nil, true)
				if err == nil && session.IsGroup(chat) {
					if !toIsGroup {
						gateway.SendErrorMessage(msg.From, toJid.Node, "KHVATIT SYUDA ZVONITb", 403, false, component)
						return
					}

					if toJid.Resource != "" {
						if isGroupchat {
							gateway.SendErrorMessageWithBody(msg.From, msg.To, msg.Body, "", msg.Id, 400, true, component)
						} else {
							gateway.SendErrorMessage(msg.From, msg.To, "PMing room occupants is not supported, use the real JID", 406, true, component)
						}
						return
					}
				}
			}

			var reply extensions.Reply
			var fallback extensions.Fallback
			var replace extensions.Replace
			var attachTo extensions.AttachTo
			msg.Get(&reply)
			msg.Get(&fallback)
			msg.Get(&replace)
			msg.Get(&attachTo)
			log.Debugf("reply: %#v", reply)
			log.Debugf("fallback: %#v", fallback)
			log.Debugf("replace: %#v", replace)
			log.Debugf("attachTo: %#v", attachTo)

			var replyId int64
			text := msg.Body
			if len(reply.Id) > 0 {
				chatId, msgId, err := gateway.IdsDB.GetByXmppId(session.Session.Login, bare, reply.Id)
				if err == nil {
					if chatId != toID {
						log.Warnf("Chat mismatch: %v ≠ %v", chatId, toID)
					} else {
						replyId = msgId
						log.Debugf("replace tg: %#v %#v", chatId, msgId)
					}
				} else {
					replyId, _ = parseMessageId(reply.Id)
				}

				if replyId != 0 && fallback.For == "urn:xmpp:reply:0" && len(fallback.Body) > 0 {
					body := fallback.Body[0]
					var start, end int64
					start, err = strconv.ParseInt(body.Start, 10, 64)
					if err != nil {
						log.WithFields(log.Fields{
							"start": body.Start,
						}).Warn(errors.Wrap(err, "Failed to parse fallback start!"))
					}
					end, err = strconv.ParseInt(body.End, 10, 64)
					if err != nil {
						log.WithFields(log.Fields{
							"end": body.End,
						}).Warn(errors.Wrap(err, "Failed to parse fallback end!"))
					}

					fullRunes := []rune(text)
					cutRunes := make([]rune, 0, len(text)-int(end-start))
					cutRunes = append(cutRunes, fullRunes[:start]...)
					cutRunes = append(cutRunes, fullRunes[end:]...)
					text = string(cutRunes)
				}
			}
			var replaceId int64
			if replace.Id != "" {
				chatId, msgId, err := gateway.IdsDB.GetByXmppId(session.Session.Login, bare, replace.Id)
				if err == nil {
					if chatId != toID {
						if isGroupchat {
							gateway.SendErrorMessage(msg.From, gateway.MUCJID(toID), text, 400, isGroupchat, component)
						} else {
							gateway.SendTextMessage(msg.From, gateway.CHATNODE(toID), "<ERROR: Chat mismatch>", component, isGroupchat)
						}
						return
					}
					replaceId = msgId
					log.Debugf("replace tg: %#v %#v", chatId, msgId)
				} else {
					if isGroupchat {
						gateway.SendErrorMessage(msg.From, gateway.MUCJID(toID), text, 400, isGroupchat, component)
					} else {
						gateway.SendTextMessage(msg.From, gateway.CHATNODE(toID), "<ERROR: Could not find matching message to edit>", component, isGroupchat)
					}
					return
				}
			}

			session.SendMessageLock.Lock()
			defer session.SendMessageLock.Unlock()
			tgMessage, isCommand := session.ProcessOutgoingMessage(toID, text, msg.From, replyId, replaceId, isGroupchat, false)
			if tgMessage != nil {
				if replaceId != 0 {
					// not needed (is it persistent among clients though?)
					/* err = gateway.IdsDB.ReplaceIdPair(session.Session.Login, bare, replace.Id, msg.Id, tgMessageId)
					if err != nil {
						log.Errorf("Failed to replace id %v with %v %v", replace.Id, msg.Id, tgMessageId)
					} */
					session.AddToEditOutbox(replace.Id, resource)
				} else {
					messageId := msg.Id
					if attachTo.Id != "" {
						messageId = attachTo.Id
					}
					err = gateway.IdsDB.Set(session.Session.Login, bare, toID, tgMessage.Id, messageId)
					if err == nil {
						// session.AddToOutbox(msg.Id, resource)
						session.UpdateLastChatMessageId(toID, messageId)
					} else {
						log.Errorf("Failed to save ids %v/%v %v", toID, tgMessage.Id, messageId)
					}
				}

				// pong groupchat messages back
				if isGroupchat && toJid.Resource == "" && tgMessage.SenderId != nil {
					session.SendMessageToGateway(
						toID,
						tgMessage,
						msg.Id,
						false,
						msg.To + "/" + session.GetMUCNickname(session.GetSenderId(tgMessage.SenderId)),
						[]string{msg.From},
						"",
					)
				}
			} else if isCommand && isGroupchat && session.Session.MUC {
				// pong outgoing commands back to groupchats
				gateway.SendMessage(msg.From, msg.To + "/" + session.GetMUCNickname(0), text, "", component, nil, 0, "", false, isGroupchat, false, "", "", "", "", nil)
			} else {
				/*
					// if a message failed to edit on Telegram side, match new XMPP ID with old Telegram ID anyway
					if replaceId != 0 {
						err = gateway.IdsDB.ReplaceXmppId(session.Session.Login, bare, replace.Id, msg.Id)
						if err != nil {
							log.Errorf("Failed to replace id %v with %v", replace.Id, msg.Id)
						}
					} */
			}
			return
		} else {
			toJid, err := stanza.NewJid(msg.To)
			if err == nil && toJid.Bare() == gatewayJid && (strings.HasPrefix(msg.Body, "/") || strings.HasPrefix(msg.Body, "!")) {
				response, _ := session.ProcessTransportCommand(msg.Body, resource)
				if response != "" {
					gateway.SendServiceMessage(msg.From, response, component)
				}
				return
			}
		}
		log.Warn("Unknown purpose of the message, skipping")
	}

	if msg.Body == "" {
		var privilege1 extensions.ComponentPrivilege1
		if ok := msg.Get(&privilege1); ok {
			log.Debugf("privilege1: %#v", privilege1)
		}

		for _, perm := range privilege1.Perms {
			if perm.Access == "message" && perm.Type == "outgoing" {
				gateway.MessageOutgoingPermissionVersion = 1
			}
		}

		var privilege2 extensions.ComponentPrivilege2
		if ok := msg.Get(&privilege2); ok {
			log.Debugf("privilege2: %#v", privilege2)
		}

		for _, perm := range privilege2.Perms {
			if perm.Access == "message" && perm.Type == "outgoing" {
				gateway.MessageOutgoingPermissionVersion = 2
			}
		}

		var displayed stanza.MarkDisplayed
		msg.Get(&displayed)
		if displayed.ID != "" {
			log.Debugf("displayed: %#v", displayed)

			bare, _, ok := gateway.SplitJID(msg.From)
			if !ok {
				return
			}
			session, ok := sessions[bare]
			if !ok {
				return
			}
			toID, ok, _ := toToID(msg.To)
			if !ok {
				return
			}
			msgId, err := strconv.ParseInt(displayed.ID, 10, 64)
			if err == nil {
				session.MarkAsRead(toID, msgId)
			}
			return
		}

		if msg.Thread == "" && msg.Subject != "" && msg.Type == "groupchat" {
			log.Debugf("MUC subject change: %#v", msg)

			bare, _, ok := gateway.SplitJID(msg.From)
			if !ok {
				return
			}
			session, ok := sessions[bare]
			if !ok {
				return
			}
			toID, ok, isGroup := toToID(msg.To)
			if !ok || !isGroup {
				return
			}
			_, resource, ok := gateway.SplitJID(msg.To)
			if ok && resource != "" {
				return
			}

			go func() {
				pinOk := session.NewPinnedMessage(toID, msg.Subject, msg.From)
				if !pinOk {
					gateway.SendErrorMessage(msg.From, gateway.MUCJID(toID), "", 406, true, component)
				}
			}()
		}
	}

	if msg.Type == "error" {
		log.Errorf("MESSAGE ERROR: %#v", p)

		if msg.XMLName.Space == "jabber:component:accept" && msg.Error.Code == 401 {
			suffix := "@" + msg.From
			for bare, session := range sessions {
				if strings.HasSuffix(bare, suffix) {
					for _, jid := range session.GetCarbonFullJids(true, "", false) {
						gateway.SendServiceMessage(jid, "Your server \""+msg.From+"\" does not allow to send carbons", component)
					}
				}
			}
		}
	}
}

// HandlePresence processes an incoming XMPP presence
func HandlePresence(s xmpp.Sender, p stanza.Packet) {
	prs, ok := p.(stanza.Presence)
	if !ok {
		logPacketType(p)
		return
	}

	if prs.Type == "subscribe" {
		handleSubscription(s, prs)
	}
	if prs.To == gateway.Jid.Bare() {
		handlePresence(s, prs)
		return
	}
	var mucExt stanza.MucPresence
	prs.Get(&mucExt)
	if mucExt.XMLName.Space != "" {
		handleMUCPresence(s, prs, mucExt)
		return
	}
	tryHandleMUCPresence(s, prs)
}

func handleSubscription(s xmpp.Sender, p stanza.Presence) {
	log.WithFields(log.Fields{
		"from": p.From,
		"to":   p.To,
	}).Warn("Subscription request")
	log.Debugf("%#v", p)

	reply := stanza.Presence{Attrs: stanza.Attrs{
		From: p.To,
		To:   p.From,
		Id:   p.Id,
		Type: "subscribed",
	}}

	component, ok := s.(*xmpp.Component)
	if !ok {
		log.Error("Not a component")
		return
	}

	_ = gateway.ResumableSend(component, reply)

	toID, ok, _ := toToID(p.To)
	if !ok {
		return
	}
	bare, _, ok := gateway.SplitJID(p.From)
	if !ok {
		return
	}
	session, ok := getTelegramInstance(bare, &persistence.Session{}, component)
	if !ok {
		return
	}
	go session.ProcessStatusUpdate(toID, "", "", true, gateway.SPImmed(false))
}

func handlePresence(s xmpp.Sender, p stanza.Presence) {
	presenceType := p.Type
	if presenceType == "" {
		presenceType = "online"
	}

	component, ok := s.(*xmpp.Component)
	if !ok {
		log.Error("Not a component")
		return
	}

	log.WithFields(log.Fields{
		"type": presenceType,
		"from": p.From,
		"to":   p.To,
	}).Warn("Presence")
	log.Debugf("%#v", p)

	// create session
	bare, resource, ok := gateway.SplitJID(p.From)
	if !ok {
		return
	}
	session, ok := getTelegramInstance(bare, &persistence.Session{}, component)
	if !ok {
		return
	}

	switch p.Type {
	// destroy session
	case "unsubscribed", "unsubscribe":
		if session.Disconnect(resource, false) {
			sessionLock.Lock()
			delete(sessions, bare)
			sessionLock.Unlock()
		}
	// go offline
	case "unavailable", "error":
		session.Disconnect(resource, false)
	// go online
	case "probe", "", "online", "subscribe":
		// due to the weird implementation of go-tdlib wrapper, it won't
		// return the client instance until successful authorization
		go func() {
			err := session.Connect(resource, false)
			if err != nil {
				log.Error(errors.Wrap(err, "TDlib connection failure"))
			} else {
				var probeFiredForFrom bool
				probeFiredLock.Lock()
				_, probeFiredForFrom = probeFired[p.From]
				probeFired[p.From] = true
				probeFiredLock.Unlock()

				if p.Type != "probe" || !probeFiredForFrom {
					for status := range session.StatusesRange() {
						show, description, typ := status.Destruct()
						newArgs := []args.V{
							gateway.SPImmed(false),
						}
						if typ != "" {
							newArgs = append(newArgs, gateway.SPType(typ))
						}
						go session.ProcessStatusUpdate(
							status.ID,
							description,
							show,
							true,
							newArgs...,
						)
					}
					probeClientFeatures(p.From, component)
					session.UpdateChatNicknames()
				}
			}
		}()
	}
}

func handleMUCPresence(s xmpp.Sender, p stanza.Presence, mucExt stanza.MucPresence) {
	log.WithFields(log.Fields{
		"type": p.Type,
		"from": p.From,
		"to":   p.To,
	}).Warn("MUC presence")
	log.Debugf("%#v", p)

	if p.Type == "" {
		toBare, nickname, ok := gateway.SplitJID(p.To)
		if ok {
			component, ok := s.(*xmpp.Component)
			if !ok {
				log.Error("Not a component")
				return
			}

			// separate declaration is crucial for passing as pointer to defer
			var reply *stanza.Presence
			reply = &stanza.Presence{Attrs: stanza.Attrs{
				From: toBare,
				To:   p.From,
				Id:   p.Id,
			}}
			defer gateway.ResumableSend(component, reply)

			if nickname == "" {
				presenceReplySetError(reply, 400)
				return
			}

			chatId, ok, toIsGroup := toToID(toBare)
			if !ok || !toIsGroup {
				presenceReplySetError(reply, 405)
				return
			}

			fromBare, fromResource, ok := gateway.SplitJID(p.From)
			if !ok {
				presenceReplySetError(reply, 400)
				return
			}

			session, ok := sessions[fromBare]
			if !ok || !session.Session.MUC {
				presenceReplySetError(reply, 407)
				return
			}

			chat, _, err := session.GetContactByID(chatId, nil, true)
			if err != nil || !session.IsGroup(chat) {
				presenceReplySetError(reply, 404)
				return
			}

			status := session.GetMyStatusInChat(chatId)
			log.Debugf("status in group %v: %v", chatId, status)
			switch status {
			case telegram.ChatMemberStatusBanned, telegram.ChatMemberStatusIllegal:
				presenceReplySetError(reply, 403)
				return
			}

			log.Debugf("%#v", mucExt)
			maxStanzas, maxStanzasOk := mucExt.History.MaxStanzas.Get()
			maxChars, maxCharsOk := mucExt.History.MaxChars.Get()
			seconds, secondsOk := mucExt.History.Seconds.Get()

			var limit *telegram.MessageLimit
			if maxStanzasOk {
				limit = telegram.NewMessageLimitMessages(int32(maxStanzas))
			} else if maxCharsOk {
				limit = telegram.NewMessageLimitChars(maxChars)
			} else if secondsOk {
				limit = telegram.NewMessageLimitSince(time.Now().Add(time.Duration(seconds) * -time.Second).Unix())
			} else if !mucExt.History.Since.IsZero() {
				limit = telegram.NewMessageLimitSince(mucExt.History.Since.Unix())
			} else {
				limit = telegram.NewMessageLimitMessages(MUC_DEFAULT_HISTORY_LIMIT)
			}
			session.JoinMUC(chatId, fromResource, limit)
		}
	}
}

func tryHandleMUCPresence(s xmpp.Sender, p stanza.Presence) {
	toBare, nickname, ok := gateway.SplitJID(p.To)
	if !ok || nickname == "" {
		return
	}

	log.WithFields(log.Fields{
		"type": p.Type,
		"from": p.From,
		"to":   p.To,
	}).Warn("Nickname change presence?")
	log.Debugf("%#v", p)

	fromBare, fromResource, ok := gateway.SplitJID(p.From)
	if !ok {
		return
	}

	session, ok := sessions[fromBare]
	if !ok || !session.Session.MUC {
		return
	}

	chatId, ok, toIsGroup := toToID(toBare)
	if !ok || !toIsGroup {
		return
	}

	chat, _, err := session.GetContactByID(chatId, nil, true)
	if err != nil || !session.IsGroup(chat) {
		return
	}

	component, ok := s.(*xmpp.Component)
	if !ok {
		log.Error("Not a component")
		return
	}

	if p.Type == stanza.PresenceTypeError {
		return
	}

	if !session.MUCHasResource(chatId, fromResource) {
		// groupchat 1.0 join
		gateway.SendPresence(
			component,
			p.From,
			gateway.SPFullFrom(p.To),
			gateway.SPType("unavailable"),
			gateway.SPMUCAffiliation("none"),
			gateway.SPMUCRole("none"),
			gateway.SPMUCStatusCodes([]uint16{110, 307, 333}),
		)
		return
	}

	switch p.Type {
	case "":
		if p.Show == "" {
			handleMUCNicknameChange(component, p, session, chatId, toBare, nickname)
		}
	case stanza.PresenceTypeUnavailable:
		handleMUCUnavailable(component, p, session, chatId, fromResource)
	}
}

func handleMUCNicknameChange(component *xmpp.Component, p stanza.Presence, session *telegram.Client, chatId int64, toBare string, newNickname string) {
	log.Warn("🗿 Yes")

	from := toBare
	nickname, ok := session.GetMyMUCNickname(chatId)
	if ok {
		if nickname == newNickname {
			log.Warn("But whatever, it's the same")
			return
		}
		from = from+"/"+nickname
	}
	reply := &stanza.Presence{
		Attrs: stanza.Attrs{
			From:  from,
			To:    p.From,
			Id:    p.Id,
			Type:  stanza.PresenceTypeError,
		},
		Error: stanza.Err{
			Code:   406,
			Type:   stanza.ErrorTypeModify,
			Reason: "not-acceptable",
			Text:   "Telegram does not support changing nicknames per-chat. Issue a /setname command to the transport if you wish to change the global name",
		},
	}
	gateway.ResumableSend(component, reply)
}

func handleMUCUnavailable(component *xmpp.Component, p stanza.Presence, session *telegram.Client, chatId int64, resource string) {
	log.Warn("No, it's a MUC exit")

	session.LeaveMUC(chatId, resource)

	gateway.SendPresence(
		component,
		p.From,
		gateway.SPFullFrom(p.To),
		gateway.SPType("unavailable"),
		gateway.SPMUCAffiliation("member"),
		gateway.SPMUCRole("none"),
		gateway.SPMUCJid(p.From),
		gateway.SPMUCStatusCodes([]uint16{110}),
	)
}

func handleGetVcardIq(s xmpp.Sender, iq *stanza.IQ, typ byte) {
	log.WithFields(log.Fields{
		"from": iq.From,
		"to":   iq.To,
	}).Warn("VCard request")

	fromJid, err := stanza.NewJid(iq.From)
	if err != nil {
		log.Error("Invalid from JID!")
		return
	}

	session, ok := sessions[fromJid.Bare()]
	if !ok {
		log.Error("IQ from stranger")
		return
	}

	toID, toOk, isGroup := toToID(iq.To)
	if !toOk {
		log.Error("Invalid IQ to")
		return
	}

	if isGroup {
		toJid, err := stanza.NewJid(iq.To)
		if err != nil {
			log.Error("Invalid to JID!")
			return
		}

		if toJid.Resource != "" {
			toID = session.GetMUCMemberIdByNickname(toID, toJid.Resource)
		}
	}

	info, err := session.GetVcardInfo(toID)
	if err != nil {
		log.Error(err)
		return
	}

	answer := stanza.IQ{
		Attrs: stanza.Attrs{
			From: iq.To,
			To:   iq.From,
			Id:   iq.Id,
			Type: "result",
		},
		Payload: makeVCardPayload(typ, iq.To, info, session),
	}
	log.Debugf("%#v", answer)

	component, ok := s.(*xmpp.Component)
	if !ok {
		log.Error("Not a component")
		return
	}

	_ = gateway.ResumableSend(component, &answer)
}

func handleGetAvatarDataIq(s xmpp.Sender, iq *stanza.IQ, pubsub *stanza.PubSubGeneric) {
	fromJid, err := stanza.NewJid(iq.From)
	if err != nil {
		log.Errorf("Invalid from JID %v", iq.From)
		return
	}

	chatId, ok, _ := toToID(iq.To)
	if !ok {
		log.Errorf("Invalid chat id in To JID %v", iq.To)
		return
	}

	session, ok := sessions[fromJid.Bare()]
	if !ok {
		log.Errorf("IQ from stranger %v", iq.From)
		return
	}

	var id string
	if len(pubsub.Items.List) > 0 {
		id = pubsub.Items.List[0].Id
	}
	log.Infof("Avatar id %v for chat %v", id, iq.To)

	pubsubAnswer := stanza.PubSubGeneric{
		Items: &stanza.Items{
			Node: gateway.NodeAvatarData,
		},
	}

	answer := stanza.IQ{
		Attrs: stanza.Attrs{
			From: iq.To,
			To:   iq.From,
			Id:   iq.Id,
			Type: "result",
		},
		Payload: &pubsubAnswer,
	}

	component, ok := s.(*xmpp.Component)
	if !ok {
		log.Error("Not a component")
		return
	}

	defer gateway.ResumableSend(component, &answer)

	hashedAvatar := session.GetHashedAvatar(chatId)

	if id != "" && hashedAvatar.Hash != id {
		log.Infof("Cache contains %v hash for chat %v, but %v was requested; aborting", hashedAvatar.Hash, iq.To, id)
		return
	}
	if hashedAvatar.File == 0 {
		log.Infof("Avatar for chat %v is explicitly missing", iq.To)
		return
	}

	file, err := session.GetFile(hashedAvatar.File)
	if err != nil {
		log.WithFields(log.Fields{
			"chatId": chatId,
		}).Error(errors.Wrap(err, "Cannot get avatar file"))
		return
	}

	dataString := session.GetPhotoBase64(file)
	if dataString == "" {
		log.Errorf("Error reading avatar file for chat %v", iq.To)
		return
	}

	pubsubAnswer.Items.List = append(pubsubAnswer.Items.List, stanza.Item{
		Id: hashedAvatar.Hash,
		Any: &stanza.Node{
			XMLName: xml.Name{Local: "data", Space: gateway.NodeAvatarData},
			Content: dataString,
		},
	})

	log.WithFields(log.Fields{
		"length": len(dataString),
	}).Debugf("%#v", answer)
}

func getTelegramChatType(from string, to string) (telegram.ChatType, error) {
	toId, ok, _ := toToID(to)
	if ok {
		bare, _, ok := gateway.SplitJID(from)
		if ok {
			session, ok := sessions[bare]
			if ok {
				chatType, _, chatTypeErr := session.GetChatType(toId, true)
				return chatType, chatTypeErr
			}
		}
	}

	return telegram.ChatTypeUnknown, errors.New("Unknown chat type")
}

func iqResultStub(s xmpp.Sender, iq *stanza.IQ) (*xmpp.Component, *stanza.IQ, bool) {
	answer, err := stanza.NewIQ(stanza.Attrs{
		Type: stanza.IQTypeResult,
		From: iq.To,
		To:   iq.From,
		Id:   iq.Id,
		Lang: "en",
	})
	if err != nil {
		log.Errorf("Failed to create answer IQ: %v", err)
		return nil, nil, false
	}

	component, ok := s.(*xmpp.Component)
	if !ok {
		log.Error("Not a component")
		return nil, nil, false
	}

	return component, answer, true
}

func handleGetDiscoInfo(s xmpp.Sender, iq *stanza.IQ, di *stanza.DiscoInfo) {
	component, answer, ok := iqResultStub(s, iq)
	if !ok {
		return
	}
	defer gateway.ResumableSend(component, answer)

	disco := answer.DiscoInfo()
	answer.Payload = disco
	toID, toOk, toIsGroup := toToID(iq.To)

	if toIsGroup {
		toJid, err := stanza.NewJid(iq.To)
		if err == nil && toJid.Resource != "" {
			iqAnswerSetError(answer, 400)
			return
		}
	}

	if di.Node == "" {
		var isMuc bool
		bare, _, fromOk := gateway.SplitJID(iq.From)
		if fromOk {
			session, sessionOk := sessions[bare]
			if sessionOk && session.Session.MUC {
				if toOk && toIsGroup {
					chat, _, err := session.GetContactByID(toID, nil, true)
					if err == nil && session.IsGroup(chat) {
						isMuc = true
						disco.AddIdentity(chat.Title, "conference", "text")

						disco.AddFeatures(
							"http://jabber.org/protocol/muc",
							"muc_persistent",
							"muc_hidden",
							"muc_moderated",
							"muc_nonanonymous",
							"muc_unsecured",
							"http://jabber.org/protocol/muc#stable_id",
							"jabber:iq:register",
							gateway.NS_MAM0,
							gateway.NS_MAM1,
							gateway.NS_MAM2,
							"urn:xmpp:mam:2#extended",
							"urn:xmpp:sid:0",
							"vcard-temp",
						)
						fields := []*stanza.Field{
							&stanza.Field{
								Var:        "FORM_TYPE",
								Type:       "hidden",
								ValuesList: []string{"http://jabber.org/protocol/muc#roominfo"},
							},
							&stanza.Field{
								Var:        "muc#roominfo_description",
								Label:      "Description",
								ValuesList: []string{session.GetChatDescription(chat)},
							},
							&stanza.Field{
								Var:        "muc#roominfo_occupants",
								Label:      "Number of occupants",
								ValuesList: []string{strconv.FormatInt(int64(session.GetChatMemberCount(chat)), 10)},
							},
						}

						hashedAvatar := session.GetHashedAvatar(toID)
						if hashedAvatar != nil {
							fields = append(fields, &stanza.Field{
								Var:        "muc#roominfo_avatarhash",
								Label:      "Avatar hash",
								ValuesList: []string{hashedAvatar.Hash},
							})
						}

						disco.Form = stanza.NewForm(fields, "result")
					}
				} else if !toOk {
					disco.AddFeatures(
						stanza.NSDiscoItems,
						"http://jabber.org/protocol/muc#stable_id",
					)
					disco.AddIdentity("Telegram group chats", "conference", "text")
				}
			}
		}

		if toOk {
			if toIsGroup {
				if !isMuc {
					iqAnswerSetError(answer, 404)
					return
				}
			} else {
				disco.AddIdentity("", "account", "registered")
			}
			disco.AddFeatures(stanza.NSMsgChatMarkers)
			disco.AddFeatures(stanza.NSMsgReceipts)
		} else {
			disco.AddIdentity("Telegram Gateway", "gateway", "telegram")
			disco.AddFeatures("jabber:iq:register")
		}
		disco.AddFeatures(gateway.NSCommand)
		disco.AddFeatures("jabber:iq:version")
		disco.AddFeatures("urn:xmpp:time")
	} else if di.Node == "x-roomuser-item" {
		bare, _, fromOk := gateway.SplitJID(iq.From)
		if fromOk {
			session, sessionOk := sessions[bare]
			if sessionOk && session.Session.MUC {
				if toOk && toIsGroup {
					chat, _, err := session.GetContactByID(toID, nil, true)
					if err == nil && session.IsGroup(chat) {
						disco.SetNode(di.Node)
						disco.AddIdentity(session.GetMUCNickname(0), "conference", "text")
					}
				}
			}
		}
	} else if di.Node == "http://jabber.org/protocol/muc#traffic" {
		// noop yet, empty result as intended, TODO: add XHTML whenever supported
	} else {
		chatType, chatTypeErr := getTelegramChatType(iq.From, iq.To)

		var cmdType telegram.CommandType
		if toOk {
			cmdType = telegram.CommandTypeChat
		} else {
			cmdType = telegram.CommandTypeTransport
		}

		for name, command := range telegram.GetCommands(cmdType) {
			if di.Node == name {
				if chatTypeErr == nil && !telegram.IsCommandForChatType(command, chatType) {
					break
				}
				disco.AddIdentity(telegram.CommandToHelpString(name, command), "automation", "command-node")
				disco.AddFeatures(gateway.NSCommand, "jabber:x:data")
				break
			}
		}
	}
}

func handleGetDiscoItems(s xmpp.Sender, iq *stanza.IQ, di *stanza.DiscoItems) {
	component, answer, ok := iqResultStub(s, iq)
	if !ok {
		return
	}
	defer gateway.ResumableSend(component, answer)

	log.Debugf("discoItems: %#v", di)

	toID, toOk, toIsGroup := toToID(iq.To)

	if toIsGroup {
		toJid, err := stanza.NewJid(iq.To)
		if err == nil && toJid.Resource != "" {
			iqAnswerSetError(answer, 400)
			return
		}
	}

	disco := answer.DiscoItems()

	if di.Node == gateway.NSCommand {
		chatType, chatTypeErr := getTelegramChatType(iq.From, iq.To)

		var cmdType telegram.CommandType
		if toOk {
			cmdType = telegram.CommandTypeChat
		} else {
			cmdType = telegram.CommandTypeTransport
		}

		var isOnline bool
		bare, _, ok := gateway.SplitJID(iq.From)
		if ok {
			session, ok := sessions[bare]
			if ok {
				isOnline = session.Online()

				if toOk {
					isBot, err := session.IsBot(toID, true)
					if err == nil && isBot {
						disco.AddItem(iq.To, "botmenu", "Bot Menu")
					}
				}
			}
		}

		if !(toOk || isOnline) {
			disco.AddItem(iq.To, "loginwizard", "Login Wizard")
		}

		commands := telegram.GetCommands(cmdType)
		for _, name := range telegram.SortedCommandKeys(commands, telegram.OnlineFilterAny) {
			command := commands[name]
			if chatTypeErr == nil && !telegram.IsCommandForChatType(command, chatType) {
				continue
			}
			if !isOnline && command.LoginOnly {
				continue
			}
			disco.AddItem(iq.To, name, telegram.CommandToHelpString(name, command))
		}
	} else if di.Node == "" {
		if !toOk {
			bare, _, fromOk := gateway.SplitJID(iq.From)
			if fromOk {
				// raw access, no need to create a new instance if not connected
				session, sessionOk := sessions[bare]
				if sessionOk && session.Session.MUC {
					disco.AddItem(gateway.Jid.Bare(), "", "Telegram group chats")
					for _, chat := range session.GetGroupChats() {
						jid := gateway.MUCJID(chat.Id)
						disco.AddItem(jid, "", chat.Title)
					}
				}
			}
		}
	}
	answer.Payload = disco

	log.Debugf("%#v", answer)
}

func handleGetQueryRegister(s xmpp.Sender, iq *stanza.IQ) {
	component, answer, ok := iqResultStub(s, iq)
	if !ok {
		return
	}
	defer gateway.ResumableSend(component, answer)

	_, toOk, toIsGroup := toToID(iq.To)

	bare, _, ok := gateway.SplitJID(iq.From)
	var session *telegram.Client
	var sessionOk bool
	if ok {
		session, sessionOk = sessions[bare]
	}

	if toOk {
		if toIsGroup {
			nickname := "me"
			if sessionOk {
				nickname = session.GetMUCNickname(0)
			}
			answer.Payload = extensions.QueryRegister{
				Instructions: "MUC username is static",
				Username:     nickname,
				Registered:   &extensions.QueryRegisterRegistered{},
			}
		} else {
			query := extensions.QueryRegister{}
			iqAnswerRegisterSetError(answer, &query, 404)
			return
		}
	} else {
		var login string
		if sessionOk {
			login = session.Session.Login
		}

		var query stanza.IQPayload
		if login == "" {
			query = extensions.QueryRegister{
				Instructions: fmt.Sprintf("Authorization in Telegram is a multi-step process, so please accept %v to your contacts and follow further instructions (provide the authentication code there, etc.).\nFor now, please provide your login.", iq.To),
			}
		} else {
			query = extensions.QueryRegister{
				Instructions: "Already logged in",
				Username:     login,
				Registered:   &extensions.QueryRegisterRegistered{},
			}
		}
		answer.Payload = query

		log.Debugf("%#v", query)

		if login == "" {
			gateway.SubscribeToTransport(component, iq.From)
		}
	}
}

func handleGetVersion(s xmpp.Sender, iq *stanza.IQ) {
	component, ok := s.(*xmpp.Component)
	if !ok {
		log.Error("Not a component")
		return
	}

	answer, err := stanza.NewIQ(stanza.Attrs{
		Type: stanza.IQTypeResult,
		From: iq.To,
		To:   iq.From,
		Id:   iq.Id,
		Lang: "en",
	})
	if err != nil {
		log.Errorf("Failed to create answer IQ: %v", err)
		return
	}

	answer.Version().SetInfo(gateway.Jid.Resource, gateway.Version, "")

	log.Debugf("%#v", answer.Payload)

	_ = gateway.ResumableSend(component, answer)
}

func handleGetEntityTime(s xmpp.Sender, iq *stanza.IQ) {
	component, ok := s.(*xmpp.Component)
	if !ok {
		log.Error("Not a component")
		return
	}

	// separate declaration is crucial for passing as pointer to defer
	var answer *stanza.IQ
	var err error
	answer, err = stanza.NewIQ(stanza.Attrs{
		Type: stanza.IQTypeResult,
		From: iq.To,
		To:   iq.From,
		Id:   iq.Id,
		Lang: "en",
	})
	if err != nil {
		log.Errorf("Failed to create answer IQ: %v", err)
		return
	}

	defer gateway.ResumableSend(component, answer)

	fromJid, err := stanza.NewJid(iq.From)
	if err != nil {
		log.Error("Invalid from JID!")
		return
	}

	session, ok := sessions[fromJid.Bare()]
	if !ok {
		log.Error("IQ from stranger")
		return
	}

	entityTime := extensions.EntityTime{
		Tzo: session.GetTZD(),
		Utc: time.Now().UTC().Format(time.RFC3339),
	}
	answer.Payload = &entityTime

	log.Debugf("%#v", entityTime)
}

func handleGetQueryMucAdmin(s xmpp.Sender, iq *stanza.IQ, query *extensions.QueryMucAdmin) {
	component, answer, ok := iqResultStub(s, iq)
	if !ok {
		return
	}
	defer gateway.ResumableSend(component, answer)

	bare, _, fromOk := gateway.SplitJID(iq.From)
	if !fromOk {
		iqAnswerSetError(answer, 400)
		return
	}

	session, sessionOk := sessions[bare]
	if !sessionOk || !session.Session.MUC {
		iqAnswerSetError(answer, 403)
		return
	}

	toID, toOk, toIsGroup := toToID(iq.To)
	if !toOk || !toIsGroup {
		iqAnswerSetError(answer, 406)
		return
	}

	chat, _, err := session.GetContactByID(toID, nil, true)
	if err != nil || !session.IsGroup(chat) {
		iqAnswerSetError(answer, 405)
		return
	}

	if len(query.Items) != 1 {
		iqAnswerSetError(answer, 400)
		return
	}
	item := query.Items[0]

	if item.Role != "" && item.Affiliation != "" {
		iqAnswerSetError(answer, 400)
		return
	}

	var membersList telegram.MembersList
	switch item.Role {
	case "moderator":
		membersList = telegram.MembersListAdministrators
	case "participant":
		membersList = telegram.MembersListMembers
	}
	switch item.Affiliation {
	case "owner":
		membersList = telegram.MembersListCreators
	case "admin":
		membersList = telegram.MembersListAdministrators
	case "member":
		membersList = telegram.MembersListMembers
	case "outcast":
		membersList = telegram.MembersListBanned
	}

	if membersList == telegram.MembersListNone {
		iqAnswerSetError(answer, 400)
		return
	}

	payload := &extensions.QueryMucAdmin{}
	answer.Payload = payload

	members, err := session.GetChatMembers(toID, false, "", membersList)
	if err == nil {
		for _, member := range members {
			senderId, nickname, affiliation, role := session.TgMemberToMUCOccupant(member, chat)
			if item.Role != "" && role != item.Role {
				continue
			}
			if item.Affiliation != "" && affiliation != item.Affiliation {
				continue
			}
			newItem := extensions.QueryMucAdminItem{}
			if item.Affiliation == "" || item.Affiliation != "outcast" {
				newItem.Nick = nickname
			}
			if item.Role != "" {
				newItem.Role = role
				newItem.Jid = gateway.CHATJID(senderId, true)
			} else {
				newItem.Affiliation = affiliation
				newItem.Jid = gateway.CHATJID(senderId, false)
			}
			payload.Items = append(payload.Items, &newItem)
		}
	}
}

func handleGetQueryMucOwner(s xmpp.Sender, iq *stanza.IQ) {
	component, answer, ok := iqResultStub(s, iq)
	if !ok {
		return
	}
	defer gateway.ResumableSend(component, answer)

	bare, _, fromOk := gateway.SplitJID(iq.From)
	if !fromOk {
		iqAnswerSetError(answer, 400)
		return
	}

	session, sessionOk := sessions[bare]
	if !sessionOk || !session.Session.MUC {
		iqAnswerSetError(answer, 403)
		return
	}

	toID, toOk, toIsGroup := toToID(iq.To)
	if !toOk || !toIsGroup {
		iqAnswerSetError(answer, 405)
		return
	}

	chat, _, err := session.GetContactByID(toID, nil, true)
	if err != nil || chat == nil || !session.IsGroup(chat) {
		iqAnswerSetError(answer, 405)
		return
	}

	payload := &extensions.QueryMucOwner{}
	answer.Payload = payload

	dummyString := ""
	changeSubject := "1"
	if chat.Permissions != nil && !chat.Permissions.CanPinMessages {
		changeSubject = "0"
	}

	payload.Form = &stanza.Form{
		Type:   stanza.FormTypeForm,
		Title:  fmt.Sprintf("Configuration for \"%v\" room", chat.Title),
		Fields: []*stanza.Field{
			&stanza.Field{
				Var:        "FORM_TYPE",
				Type:       stanza.FieldTypeHidden,
				ValuesList: []string{"http://jabber.org/protocol/muc#roominfo"},
			},
			&stanza.Field{
				Var:        "muc#roomconfig_roomname",
				Label:      "Group name",
				Required:   &dummyString,
				ValuesList: []string{chat.Title},
			},
			&stanza.Field{
				Var:        "muc#roomconfig_roomdesc",
				Label:      "Description (optional)",
				ValuesList: []string{session.GetChatDescription(chat)},
			},
			&stanza.Field{
				Var:        "muc#roomconfig_changesubject",
				Label:      "Allow Occupants to Change Subject?",
				Type:       stanza.FieldTypeBool,
				ValuesList: []string{changeSubject},
			},
		},
	}
}

func handleGetQueryMAM(s xmpp.Sender, iq *stanza.IQ, query extensions.MAMQuery) {
	component, answer, ok := iqResultStub(s, iq)
	if !ok {
		return
	}
	defer gateway.ResumableSend(component, answer)

	payload2 := &extensions.MAM2Query{}
	payload1 := &extensions.MAM1Query{}
	payload0 := &extensions.MAM0Query{}
	ns := query.Namespace()
	switch ns {
	case gateway.NS_MAM2:
		answer.Payload = payload2
	case gateway.NS_MAM1:
		answer.Payload = payload1
	case gateway.NS_MAM0:
		answer.Payload = payload0
	}

	form := stanza.Form{
		Type:   stanza.FormTypeForm,
		Fields: []*stanza.Field{
			&stanza.Field{
				Var:        "FORM_TYPE",
				Type:       stanza.FieldTypeHidden,
				ValuesList: []string{ns},
			},
			&stanza.Field{
				Var:  "with",
				Type: stanza.FieldTypeJidSingle,
			},
			&stanza.Field{
				Var:  "start",
				Type: stanza.FieldTypeTextSingle,
			},
			&stanza.Field{
				Var:  "end",
				Type: stanza.FieldTypeTextSingle,
			},
			&stanza.Field{
				Var:  "before-id",
				Type: stanza.FieldTypeTextSingle,
			},
			&stanza.Field{
				Var:  "after-id",
				Type: stanza.FieldTypeTextSingle,
			},
			&stanza.Field{
				Var:  "ids",
				Type: stanza.FieldTypeListMulti,
			},
		},
	}
	payload2.Form = &form
	payload1.Form = &form
	payload0.Form = &form
	log.Debugf("MAM info request: %#v", query)
}

func handleGetMetadataMAM2(s xmpp.Sender, iq *stanza.IQ) {
	component, answer, ok := iqResultStub(s, iq)
	if !ok {
		return
	}
	defer gateway.ResumableSend(component, answer)

	bare, _, fromOk := gateway.SplitJID(iq.From)
	if !fromOk {
		iqAnswerSetError(answer, 400)
		return
	}

	session, sessionOk := sessions[bare]
	if !sessionOk || !session.Session.MUC {
		iqAnswerSetError(answer, 403)
		return
	}

	toID, toOk, toIsGroup := toToID(iq.To)
	if !toOk || !toIsGroup {
		iqAnswerSetError(answer, 405)
		return
	}

	chat, _, err := session.GetContactByID(toID, nil, true)
	if err != nil || chat == nil || !session.IsGroup(chat) {
		iqAnswerSetError(answer, 405)
		return
	}

	payload := &extensions.MAM2Metadata{}
	answer.Payload = payload

	quotaTs := time.Now().AddDate(0, 0, -int(gateway.MAMThreshold))
	preFirstMessage, preFirstMessageErr := session.FindMessageByTime(toID, quotaTs)
	var preFirstMessageId int64
	if preFirstMessageErr == nil && preFirstMessage != nil {
		preFirstMessageId = preFirstMessage.Id
	} else {
		preFirstMessageId = 1
	}
	startMessage, startMessageErr := session.GetNextMessage(toID, preFirstMessageId)
	if startMessageErr == nil && startMessage != nil {
		payload.Start = &extensions.MAM2MetadataStart{
			Id:        strconv.FormatInt(startMessage.Id, 10),
			Timestamp: extensions.TimestampToRFC3339(int64(startMessage.Date)),
		}
	}

	endMessage, endMessageErr := session.GetPreviousMessage(toID, 0)
	if endMessageErr == nil && endMessage != nil {
		payload.End = &extensions.MAM2MetadataEnd{
			Id:        strconv.FormatInt(endMessage.Id, 10),
			Timestamp: extensions.TimestampToRFC3339(int64(endMessage.Date)),
		}
	}
	log.Debugf("MAM metadata: %#v", payload)
}

func handleSetQueryRegister(s xmpp.Sender, iq *stanza.IQ, query *extensions.QueryRegister) {
	component, answer, ok := iqResultStub(s, iq)
	if !ok {
		return
	}
	defer gateway.ResumableSend(component, answer)

	_, toOk, _ := toToID(iq.To)
	if toOk {
		iqAnswerRegisterSetError(answer, query, 400)
		return
	}

	if query.Remove != nil {
		iqAnswerRegisterSetError(answer, query, 405)
		return
	}

	var login string
	var session *telegram.Client
	bare, resource, ok := gateway.SplitJID(iq.From)
	if ok {
		session, ok = sessions[bare]
		if ok {
			login = session.Session.Login
		}
	}

	if login == "" {
		if !ok {
			session, ok = getTelegramInstance(bare, &persistence.Session{}, component)
			if !ok {
				iqAnswerRegisterSetError(answer, query, 500)
				return
			}
		}

		err := session.TryLogin(resource, query.Username)
		if err != nil {
			if err.Error() == telegram.TelegramAuthDone {
				iqAnswerRegisterSetError(answer, query, 406)
			} else {
				iqAnswerRegisterSetError(answer, query, 500)
			}
			return
		}

		err = session.SetPhoneNumber(query.Username)
		if err != nil {
			iqAnswerRegisterSetError(answer, query, 500)
			return
		}

		// everything okay, the response should be empty with no payload/error at this point
		gateway.SubscribeToTransport(component, iq.From)
	} else {
		iqAnswerRegisterSetError(answer, query, 406)
	}
}

func handleSetQueryCommand(s xmpp.Sender, iq *stanza.IQ, command *stanza.Command) {
	component, answer, ok := iqResultStub(s, iq)
	if !ok {
		return
	}

	cancelSend := false

	defer func() {
		if !cancelSend {
			gateway.ResumableSend(component, answer)
		}
	}()

	log.Debugf("command: %#v", command)

	bare, resource, ok := gateway.SplitJID(iq.From)
	if !ok {
		return
	}
	toId, toOk, _ := toToID(iq.To)

	var cmdString string
	var cmdType telegram.CommandType
	var form *stanza.Form
	for _, ce := range command.CommandElements {
		fo, formOk := ce.(*stanza.Form)
		if formOk {
			form = fo
			break
		}
	}
	if toOk {
		cmdType = telegram.CommandTypeChat
	} else {
		cmdType = telegram.CommandTypeTransport
	}
	if form != nil {
		if command.Node == "config" {
			session, ok := sessions[bare]
			if ok {
				var infoStrings []string
				var warnString, errString string
				for _, field := range form.Fields {
					if len(field.ValuesList) > 0 {
						// 10. In accordance with Section 3.2.2.1 of XML Schema Part 2: Datatypes, the allowable
						// lexical representations for the xs:boolean datatype are the strings "0" and "false"
						// for the concept 'false' and the strings "1" and "true" for the concept 'true';
						// implementations MUST support both styles of lexical representation.
						fieldValue := persistence.NormalizeProperty(field.Var, field.ValuesList[0])

						if gateway.MessageOutgoingPermissionVersion == 0 && field.Var == "carbons" && fieldValue == "true" {
							warnString = "The server did not allow to enable carbons"
							continue
						}

						oldValue, err := session.Session.Get(field.Var)
						if err != nil || oldValue != fieldValue {
							value, err := session.Session.Set(field.Var, fieldValue)
							if err != nil {
								errString = fmt.Sprintf("Error for field %v: %v, aborting", field.Var, err.Error())
								break
							}
							if field.Var == "muc" {
								switch fieldValue {
								case "true":
									go session.MigrateToMUCs()
								case "false":
									go session.MigrateFromMUCs()
								}
							}
							infoStrings = append(infoStrings, fmt.Sprintf("%s set to %s", field.Var, value))
							gateway.DirtySessions = true
						}
					}
				}

				var elements []stanza.CommandElement
				if errString != "" {
					elements = append(elements, &stanza.Note{
						Text: errString,
						Type: stanza.CommandNoteTypeErr,
					})
				}
				if warnString != "" {
					elements = append(elements, &stanza.Note{
						Text: warnString,
						Type: stanza.CommandNoteTypeWarn,
					})
				}
				for _, infoString := range infoStrings {
					elements = append(elements, &stanza.Note{
						Text: infoString,
						Type: stanza.CommandNoteTypeInfo,
					})
				}

				answer.Payload = &stanza.Command{
					SessionId:       command.Node,
					Node:            command.Node,
					Status:          stanza.CommandStatusCompleted,
					CommandElements: elements,
				}
			}
		} else if !toOk && command.Node == "loginwizard" {
			var session *telegram.Client
			answer.Payload, cancelSend, session = loginWizardPayload(bare, form, resource, command.Action)

			log.Debugf("immediate loginwizard payload: %#v", answer.Payload)
			if cancelSend {
				go sendLoginWizardResponse(component, answer, session)
			}
		} else if toOk && command.Node == "botmenu" {
			payload := &stanza.Command{
				SessionId: command.Node,
				Node:      command.Node,
			}
			answer.Payload = payload

			if len(form.Fields) == 1 && form.Fields[0] != nil &&
				form.Fields[0].Var == "command" && len(form.Fields[0].ValuesList) == 1 {
				session, ok := sessions[bare]
				if ok {
					msgText := "/" + form.Fields[0].ValuesList[0]
					session.LastBotCmdString = msgText
					tgMessage, _ := session.ProcessOutgoingMessage(toId, msgText, iq.From, 0, 0, false, true)
					if tgMessage != nil {
						payload.Status = stanza.CommandStatusCompleted
					} else {
						setCommandPayloadError(payload, "Failed to send a bot command")
					}
				} else {
					setCommandPayloadError(payload, "Session is lost")
				}
			} else {
				setCommandPayloadError(payload, "Broken form")
			}
		} else {
			// just for the case the client messed the order somehow
			sort.Slice(form.Fields, func(i int, j int) bool {
				iField := form.Fields[i]
				jField := form.Fields[j]
				if iField != nil && jField != nil {
					ii, iErr := strconv.ParseInt(iField.Var, 10, 64)
					ji, jErr := strconv.ParseInt(jField.Var, 10, 64)
					return iErr == nil && jErr == nil && ii < ji
				}
				return false
			})

			var cmd strings.Builder
			cmd.WriteString("/")
			cmd.WriteString(command.Node)
			for _, field := range form.Fields {
				cmd.WriteString(" ")
				if len(field.ValuesList) > 0 {
					cmd.WriteString(field.ValuesList[0])
				}
			}

			cmdString = cmd.String()
		}
	} else {
		if command.Action == "" || command.Action == stanza.CommandActionExecute {
			cmd, ok := telegram.GetCommand(cmdType, command.Node)
			if ok && len(cmd.Arguments) > 0 {
				var fields []*stanza.Field
				if command.Node == "config" {
					session, ok := sessions[bare]
					if ok {
						for _, key := range persistence.ConfigKeys {
							// no reason to display the item if carbons won't work
							if key == "carbons" && gateway.MessageOutgoingPermissionVersion == 0 {
								continue
							}

							value, err := session.Session.Get(key)
							if err != nil {
								log.Errorf("Achtung! Programming error in sessions with key %v", key)
								continue
							}

							var fieldType string
							if persistence.PropertyType(key) == persistence.PropertyTypeBool {
								fieldType = stanza.FieldTypeBool
							}

							field := stanza.Field{
								Var:        key,
								Label:      key,
								Type:       fieldType,
								ValuesList: []string{value},
							}
							fields = append(fields, &field)
							log.Debugf("field: %#v", field)
						}
					}
				} else {
					for i, arg := range cmd.Arguments {
						var required *string
						if i < cmd.RequiredArgs {
							dummyString := ""
							required = &dummyString
						}

						var fieldType string
						var options []stanza.Option
						if toOk && i == 0 {
							switch command.Node {
							case "mute", "kick", "ban", "promote", "unmute", "unban":
								session, ok := sessions[bare]
								if ok {
									var membersList telegram.MembersList
									switch command.Node {
									case "unmute":
										membersList = telegram.MembersListRestricted
									case "unban":
										membersList = telegram.MembersListBannedAndAdministrators
									}
									members, err := session.GetChatMembers(toId, true, "", membersList)
									if err == nil {
										fieldType = stanza.FieldTypeListSingle
										switch command.Node {
										// allow empty form
										case "mute", "unmute":
											options = append(options, stanza.Option{
												ValuesList: []string{""},
											})
										}
										for _, member := range members {
											senderId := session.GetSenderId(member.MemberId)
											options = append(options, stanza.Option{
												Label:      session.FormatContact(senderId),
												ValuesList: []string{strconv.FormatInt(senderId, 10)},
											})
										}
									}
								}
							}
						}

						field := stanza.Field{
							Var:      strconv.FormatInt(int64(i), 10),
							Label:    arg,
							Required: required,
							Type:     fieldType,
							Options:  options,
						}
						fields = append(fields, &field)
						log.Debugf("field: %#v", field)
					}
				}
				form := stanza.Form{
					Type:         stanza.FormTypeForm,
					Title:        command.Node,
					Instructions: []string{cmd.Description},
					Fields:       fields,
				}
				answer.Payload = &stanza.Command{
					SessionId:       command.Node,
					Node:            command.Node,
					Status:          stanza.CommandStatusExecuting,
					CommandElements: []stanza.CommandElement{&form},
				}
				log.Debugf("form: %#v", form)
			} else if !toOk && command.Node == "loginwizard" {
				var session *telegram.Client
				answer.Payload, cancelSend, session = loginWizardPayload(bare, nil, resource, "")

				log.Debugf("immediate loginwizard payload: %#v", answer.Payload)
				if cancelSend {
					go sendLoginWizardResponse(component, answer, session)
				}
			} else if toOk && command.Node == "botmenu" {
				session, ok := sessions[bare]

				var link *telegram.BotLink
				var commands []*telegram.BotCommand
				var err error
				if ok {
					link, commands, err = session.GetBotMenu(toId)
				}

				payload := &stanza.Command{
					SessionId: command.Node,
					Node:      command.Node,
				}
				answer.Payload = payload

				if !ok || err != nil {
					setCommandPayloadError(payload, "Cannot retrieve commands")
				} else {
					if link != nil {
						payload.Status = stanza.CommandStatusCompleted
						payload.CommandElements = []stanza.CommandElement{
							&stanza.Note{
								Text: fmt.Sprintf("%v: %v", link.Description, link.Link),
								Type: stanza.CommandNoteTypeInfo,
							},
						}
					} else {
						var options []stanza.Option
						for _, cmd := range commands {
							options = append(options, stanza.Option{
								Label:      fmt.Sprintf("/%v — %v", cmd.Command, cmd.Description),
								ValuesList: []string{cmd.Command},
							})
						}

						dummyString := ""
						field := stanza.Field{
							Var:      "command",
							Type:     stanza.FieldTypeListSingle,
							Required: &dummyString,
							Options:  options,
						}
						log.Debugf("field: %#v", field)

						form := stanza.Form{
							Type:   stanza.FormTypeForm,
							Fields: []*stanza.Field{&field},
						}
						log.Debugf("form: %#v", form)

						payload.Status = stanza.CommandStatusExecuting
						payload.CommandElements = []stanza.CommandElement{&form}
					}
				}
			} else {
				cmdString = "/" + command.Node
			}
		} else if command.Action == stanza.CommandActionCancel {
			if command.Node == "loginwizard" {
				session, ok := sessions[bare]
				if ok {
					session.ProcessTransportCommand("/cancelauth", resource)
				}
			}
			answer.Payload = &stanza.Command{
				SessionId: command.Node,
				Node:      command.Node,
				Status:    stanza.CommandStatusCancelled,
			}
		}
	}

	if cmdString != "" {
		session, ok := sessions[bare]
		if !ok {
			return
		}

		var response string
		var success bool
		if toOk {
			response, _, success = session.ProcessChatCommand(toId, cmdString)
		} else {
			response, success = session.ProcessTransportCommand(cmdString, resource)
		}

		var noteType string
		if success {
			noteType = stanza.CommandNoteTypeInfo
		} else {
			noteType = stanza.CommandNoteTypeErr
		}

		answer.Payload = &stanza.Command{
			SessionId: command.Node,
			Node:      command.Node,
			Status:    stanza.CommandStatusCompleted,
			CommandElements: []stanza.CommandElement{
				&stanza.Note{
					Text: response,
					Type: noteType,
				},
			},
		}

	}

	log.Debugf("command response: %#v %v", answer.Payload, cancelSend)
}

func handleSetQueryMucAdmin(s xmpp.Sender, iq *stanza.IQ, query *extensions.QueryMucAdmin) {
	component, answer, ok := iqResultStub(s, iq)
	if !ok {
		return
	}
	defer gateway.ResumableSend(component, answer)

	bare, _, fromOk := gateway.SplitJID(iq.From)
	if !fromOk {
		iqAnswerSetError(answer, 400)
		return
	}

	session, sessionOk := sessions[bare]
	if !sessionOk || !session.Session.MUC {
		iqAnswerSetError(answer, 403)
		return
	}

	toID, toOk, toIsGroup := toToID(iq.To)
	if !toOk || !toIsGroup {
		iqAnswerSetError(answer, 406)
		return
	}

	// pre-bake all data to make it transactional as much as possible
	type Item struct {
		UserID int64
		Nick   string
		Status telegram.ChatMemberStatus
	}

	var items []Item
	for _, item := range query.Items {
		if item.Affiliation == "owner" {
			iqAnswerSetError(answer, 403)
			return
		}

		if (item.Role != "" && item.Affiliation != "") ||
		   (item.Role != "" && item.Nick == "") ||
		   (item.Affiliation != "" && item.Jid == "") {
			iqAnswerSetError(answer, 400)
			return
		}


		var userID int64
		if item.Jid != "" {
			userID, _, _ = toToID(item.Jid)
		} else if item.Nick != "" {
			userID = session.GetMUCMemberIdByNickname(toID, item.Nick)
		}
		if userID == 0 {
			iqAnswerSetError(answer, 404)
			return
		}

		nick := session.GetMUCNickname(userID)

		var status telegram.ChatMemberStatus

		switch item.Role {
		case "none":
			status = telegram.ChatMemberStatusKicked
		case "visitor":
			status = telegram.ChatMemberStatusMuted
		case "participant":
			status = telegram.ChatMemberStatusUnmuted
		case "moderator":
			status = telegram.ChatMemberStatusPromoted
		}
		switch item.Affiliation {
		case "none":
			status = telegram.ChatMemberStatusKicked
		case "outcast":
			status = telegram.ChatMemberStatusBanned
		case "member":
			status = telegram.ChatMemberStatusUnmuted
		case "admin":
			status = telegram.ChatMemberStatusPromoted
		}

		// nothing has been detected
		if status == telegram.ChatMemberStatusIllegal {
			iqAnswerSetError(answer, 400)
			return
		}

		items = append(items, Item{
			UserID: userID,
			Nick:   nick,
			Status: status,
		})
	}

	for _, item := range items {
		err := session.SetChatMemberStatus(toID, item.UserID, item.Status, 0, "", item.Nick)
		if err != nil {
			code, ok := telegram.GetErrorCode(err)
			if !ok {
				code = 500
			}
			iqAnswerSetError(answer, int(code))
			answer.Error.Text = err.Error()
			return
		}
	}
}

func handleSetQueryMucOwner(s xmpp.Sender, iq *stanza.IQ, query *extensions.QueryMucOwner) {
	component, answer, ok := iqResultStub(s, iq)
	if !ok {
		return
	}
	defer gateway.ResumableSend(component, answer)

	bare, _, fromOk := gateway.SplitJID(iq.From)
	if !fromOk {
		iqAnswerSetError(answer, 400)
		return
	}

	session, sessionOk := sessions[bare]
	if !sessionOk || !session.Session.MUC {
		iqAnswerSetError(answer, 403)
		return
	}

	toID, toOk, toIsGroup := toToID(iq.To)
	if !toOk || !toIsGroup {
		iqAnswerSetError(answer, 405)
		return
	}

	chat, _, err := session.GetContactByID(toID, nil, true)
	if err != nil || chat == nil || !session.IsGroup(chat) {
		iqAnswerSetError(answer, 405)
		return
	}

	if query.Form != nil {
		switch query.Form.Type {
		case stanza.FormTypeSubmit:
			// okay, noop
		case stanza.FormTypeCancel:
			return
		default:
			iqAnswerSetError(answer, 400)
			return
		}

		err = nil
		for _, field := range query.Form.Fields {
			switch field.Var {
			case "muc#roomconfig_roomname", "muc#roomconfig_roomdesc", "muc#roomconfig_changesubject":
				if len(field.ValuesList) != 1 {
					iqAnswerSetError(answer, 400)
					return
				}

				value := field.ValuesList[0]

				switch field.Var {
				case "muc#roomconfig_roomname":
					if value == "" {
						iqAnswerSetError(answer, 400)
						return
					}
					if value != chat.Title {
						err = session.SetChatTitle(toID, value)
						if err != nil {
							break
						}
					}
				case "muc#roomconfig_roomdesc":
					if value != session.GetChatDescription(chat) {
						err = session.SetChatDescription(toID, value)
						if err != nil {
							break
						}
					}
				case "muc#roomconfig_changesubject":
					b, ok := ToBool(value)
					if !ok {
						iqAnswerSetError(answer, 400)
						return
					}
					permissions := chat.Permissions
					if permissions != nil && b != permissions.CanPinMessages {
						newPermissions := telegram.CloneChatPermissions(permissions)
						newPermissions.CanPinMessages = b

						err = session.SetChatPermissions(toID, newPermissions)
						if err != nil {
							break
						}
					}
				}
			}
		}
	} else if query.Destroy != nil {
		err = session.DestroyMUC(toID)
	} else {
		// per 1.0 spec version, it also could be a destruction, but too dangerous to cover probably
		iqAnswerSetError(answer, 400)
		return
	}

	if err != nil {
		code, ok := telegram.GetErrorCode(err)
		if !ok {
			code = 500
		}
		iqAnswerSetError(answer, int(code))
		answer.Error.Text = err.Error()
		return
	}

}

func handleSetQueryMAM(s xmpp.Sender, iq *stanza.IQ, query extensions.MAMQuery) {
	component, answer, ok := iqResultStub(s, iq)
	if !ok {
		return
	}
	defer gateway.ResumableSend(component, answer)

	bare, _, fromOk := gateway.SplitJID(iq.From)
	if !fromOk {
		iqAnswerSetError(answer, 400)
		return
	}

	session, sessionOk := sessions[bare]
	if !sessionOk || !session.Session.MUC {
		iqAnswerSetError(answer, 403)
		return
	}

	toID, toOk, toIsGroup := toToID(iq.To)
	if !toOk || !toIsGroup {
		iqAnswerSetError(answer, 405)
		return
	}

	chat, _, err := session.GetContactByID(toID, nil, true)
	if err != nil || chat == nil || !session.IsGroup(chat) {
		iqAnswerSetError(answer, 405)
		return
	}

	var startTime, endTime time.Time
	var beforeId, afterId int64
	var ids []string

	var rsmBefore, rsmAfter int64
	var rsmLastPage bool
	var rsmLimit int32
	var justCount bool

	form := query.GetForm()
	queryRs := query.GetSet()
	ns := query.Namespace()

	log.Debugf("MAM query to %v: %#v %#v %#v", toID, query, form, queryRs)
	if form != nil && form.Type == stanza.FormTypeSubmit {
		for _, field := range form.Fields {
			if len(field.ValuesList) < 1 {
				iqAnswerSetError(answer, 400)
				return
			}

			value := field.ValuesList[0]
			log.Debugf("MAM query field: %v %v", field.Var, value)

			switch field.Var {
			case "FORM_TYPE":
				if value != ns {
					iqAnswerSetError(answer, 400)
					return
				}
			case "with": // okay, and?
			case "start", "end":
				timestamp, err := time.Parse(time.RFC3339, value)
				if err != nil {
					iqAnswerSetError(answer, 400)
					return
				}

				switch field.Var {
				case "start":
					startTime = timestamp
				case "end":
					endTime = timestamp
				}
			case "before-id":
				beforeId, ok = parseMessageId(value)
				if !ok {
					iqAnswerSetError(answer, 400)
					return
				}
			case "after-id":
				afterId, ok = parseMessageId(value)
				if !ok {
					iqAnswerSetError(answer, 400)
					return
				}
			case "ids":
				ids = field.ValuesList
			default:
				iqAnswerSetError(answer, 501)
				return
			}
		}
	}

	if queryRs != nil {
		if queryRs.After != nil {
			rsmAfter, ok = parseMessageId(*queryRs.After)
			if !ok {
				iqAnswerSetError(answer, 400)
				return
			}
			log.Debugf("MAM RSM after: %v", rsmAfter)
		}
		if queryRs.Before != nil {
			before := *queryRs.Before
			if before == "" {
				rsmLastPage = true
				log.Debugf("MAM RSM last page")
			} else {
				rsmBefore, ok = parseMessageId(*queryRs.Before)
				if !ok {
					iqAnswerSetError(answer, 400)
					return
				}
				log.Debugf("MAM RSM before: %v", rsmBefore)
			}
		}
		if queryRs.Max != nil {
			rsmLimit = int32(*queryRs.Max)
			if rsmLimit == 0 {
				justCount = true
			}
			log.Debugf("MAM RSM max: %v", rsmLimit)
		}

		if queryRs.First != nil {
			iqAnswerSetError(answer, 400)
			return
		}
		if queryRs.Index != nil {
			iqAnswerSetError(answer, 501)
			return
		}
		if queryRs.Last != nil {
			iqAnswerSetError(answer, 400)
			return
		}
	}

	if rsmLimit == 0 && !justCount {
		rsmLimit = 100
	}

	// check for mutual parameter compatibility, there's a lot of them, nah?
	if ((!startTime.IsZero() || !endTime.IsZero()) && (beforeId != 0 || afterId != 0 || ids != nil)) ||
		((beforeId != 0 || afterId != 0) && (!startTime.IsZero() || !endTime.IsZero() || ids != nil)) ||
		(ids != nil && (!startTime.IsZero() || !endTime.IsZero() || beforeId != 0 || afterId != 0)) {
		iqAnswerSetError(answer, 501)
		log.Debugf("MAM: incompatible parameters")
		return
	}

	// dummy call to circumvent unexported type
	messages, _, err := session.GetMessagesBetween(toID, 0, 0, 0, false)

	var order bool // false from start, true from end
	// lower priority
	if !endTime.IsZero() {
		order = true
	}
	// higher priority
	if beforeId != 0 {
		order = false
	}
	if afterId != 0 {
		order = true
	}
	if rsmAfter != 0 {
		order = false
	}
	if rsmBefore != 0 || rsmLastPage {
		order = true
	}
	if order {
		rsmLimit = -rsmLimit // hacky, I know, and? :P
	}

	quotaTs := time.Now().AddDate(0, 0, -int(gateway.MAMThreshold))
	var beyond, complete bool
	fromStart := !order
	toEnd := order
	var overallyFirstMessageId, overallyLastMessageId int64

	reverse := query.GetFlipPage() != nil

	if ids != nil {
		for _, sId := range ids {
			id, ok := parseMessageId(sId)
			if !ok {
				iqAnswerSetError(answer, 400)
				log.Debugf("MAM: bogus id")
				return
			}
			msg, err := session.GetMessage(toID, id)
			if err != nil {
				iqAnswerSetError(answer, 404)
				log.Debugf("MAM: unknown id")
				return
			}
			messages = append(messages, msg)
		}
		messages = telegram.ChronologicallySortMessages(messages, reverse)
		complete = true
	} else if beforeId != 0 || afterId != 0 {
		if (beforeId != 0 && afterId != 0) && beforeId < afterId {
			iqAnswerSetError(answer, 400)
			log.Debugf("MAM: before < after")
			return
		}

		// don't allow to fetch far beyond the quota
		var replaceWithQuotaTs bool
		if afterId != 0 {
			afterMessage, afterMessageErr := session.GetMessage(toID, afterId)
			if afterMessageErr == nil && afterMessage != nil {
				if int64(afterMessage.Date) < quotaTs.Unix() {
					replaceWithQuotaTs = true
				}
			} else {
				iqAnswerSetError(answer, 404)
				log.Debugf("MAM: unknown after")
				return
			}
		} else {
			replaceWithQuotaTs = true
		}
		if replaceWithQuotaTs {
			preFirstMessage, preFirstMessageErr := session.FindMessageByTime(toID, quotaTs)
			if preFirstMessageErr == nil && preFirstMessage != nil {
				afterId = preFirstMessage.Id
			} else {
				// there seem to be no messages older than quota, it's safe to fetch from the very start
				afterId = 1 // https://github.com/tdlib/td/issues/195#issuecomment-380836359
			}
		}

		if beforeId != 0 {
			beforeMessage, beforeMessageErr := session.GetMessage(toID, beforeId)
			if beforeMessageErr != nil || beforeMessage == nil {
				iqAnswerSetError(answer, 404)
				log.Debugf("MAM: unknown before")
				return
			}
			overallyLastMessage, overallyLastMessageErr := session.GetPreviousMessage(toID, beforeId)
			if overallyLastMessageErr == nil && overallyLastMessage != nil {
				overallyLastMessageId = overallyLastMessage.Id
			}
		} else {
			newestMessage, newestMessageErr := session.GetPreviousMessage(toID, 0)
			if newestMessageErr == nil && newestMessage != nil {
				overallyLastMessageId = newestMessage.Id
			}
		}

		if rsmAfter != 0 {
			if rsmAfter < afterId || (beforeId != 0 && rsmAfter > beforeId) {
				iqAnswerSetError(answer, 400)
				log.Debugf("MAM: unknown RSM after")
				return
			}
			if rsmAfter != afterId {
				fromStart = false
				overallyFirstMessage, overallyFirstMessageErr := session.GetNextMessage(toID, afterId)
				if overallyFirstMessageErr == nil && overallyFirstMessage != nil {
					overallyFirstMessageId = overallyFirstMessage.Id
				}
			}
			afterId = rsmAfter
		}

		if rsmBefore != 0 {
			if rsmBefore < afterId || (beforeId != 0 && rsmBefore > beforeId) {
				iqAnswerSetError(answer, 400)
				log.Debugf("MAM: unknown RSM before")
				return
			}
			if rsmBefore < beforeId {
				toEnd = false
			}
			beforeId = rsmBefore
		}

		var lastMessageId int64
		// should be fine even with beforeId=0 as it would mean the last as needed
		lastMessage, lastMessageErr := session.GetPreviousMessage(toID, beforeId)
		if lastMessageErr == nil && lastMessage != nil {
			lastMessageId = lastMessage.Id
		} else {
			beyond = true
		}

		if !beyond {
			messages, complete, err = session.GetMessagesBetween(toID, afterId, lastMessageId, rsmLimit, reverse)
		}
	} else { // time limit or no limits at all
		// don't allow to fetch far beyond the quota
		if !endTime.IsZero() && endTime.Before(quotaTs) {
			beyond = true
			complete = true
		}
		if (!startTime.IsZero() && startTime.Before(quotaTs)) || startTime.IsZero() {
			startTime = quotaTs
		}

		if !beyond {
			var fromMessageId int64
			var lastMessageId int64
			fromMessage, fromMessageErr := session.FindMessageByTime(toID, startTime)
			if fromMessageErr == nil && fromMessage != nil {
				fromMessageId = fromMessage.Id
			} else {
				// there seem to be no messages older than quota, it's safe to fetch from the very start
				fromMessageId = 1 // https://github.com/tdlib/td/issues/195#issuecomment-380836359
			}

			if !endTime.IsZero() {
				endMsg, endMsgErr := session.FindMessageByTime(toID, endTime)
				if endMsgErr == nil && endMsg != nil {
					lastMessageId = endMsg.Id
					overallyLastMessageId = lastMessageId
				} else {
					beyond = true
					complete = true
				}
			} else {
				newestMessage, newestMessageErr := session.GetPreviousMessage(toID, 0)
				if newestMessageErr == nil && newestMessage != nil {
					overallyLastMessageId = newestMessage.Id
				}
			}

			if rsmAfter != 0 {
				rsmAfterMessage, rsmAfterMessageErr := session.GetMessage(toID, rsmAfter)
				if rsmAfterMessageErr == nil && rsmAfterMessage != nil {
					if !endTime.IsZero() && int64(rsmAfterMessage.Date) > endTime.Unix() {
						iqAnswerSetError(answer, 400)
						log.Debugf("MAM: RSM after out of range")
						return
					}

					if rsmAfterMessage.Id > fromMessageId && int64(rsmAfterMessage.Date) >= startTime.Unix() {
						fromStart = false
						overallyFirstMessage, overallyFirstMessageErr := session.GetNextMessage(toID, fromMessageId)
						if overallyFirstMessageErr == nil && overallyFirstMessage != nil {
							overallyFirstMessageId = overallyFirstMessage.Id
						}
					}
					fromMessageId = rsmAfterMessage.Id
				} else {
					iqAnswerSetError(answer, 404)
					log.Debugf("MAM: unknown RSM after")
					return
				}
			}

			if rsmBefore != 0 {
				rsmBeforeMessage, rsmBeforeMessageErr := session.GetMessage(toID, rsmBefore)
				if rsmBeforeMessageErr == nil && rsmBeforeMessage != nil {
					if int64(rsmBeforeMessage.Date) < startTime.Unix() {
						iqAnswerSetError(answer, 400)
						log.Debugf("MAM: RSM before out of range")
						return
					}

					if endTime.IsZero() || int64(rsmBeforeMessage.Date) <= endTime.Unix() {
						newLastMessage, newLastMessageErr := session.GetPreviousMessage(toID, rsmBeforeMessage.Id)
						if newLastMessageErr == nil && newLastMessage != nil {
							if lastMessageId == 0 || lastMessageId != newLastMessage.Id {
								toEnd = false
								lastMessageId = newLastMessage.Id
							}
						} else {
							// nothing?.. not complete, just empty
							beyond = true
						}
					}
				} else {
					iqAnswerSetError(answer, 404)
					log.Debugf("MAM: unknown RSM before")
					return
				}
			}

			if !beyond { // yes🗿, twice
				messages, complete, err = session.GetMessagesBetween(toID, fromMessageId, lastMessageId, rsmLimit, reverse)
			}
		}
	}

	log.Debugf("obtained %v messages", len(messages))
	// ty zhe lopnesh, detochka
	queryId := ns + " " + query.GetQueryId()
	for _, message := range messages {
		session.SendDelayedMUCMessage(toID, message, iq.From, queryId)
	}

	rs := stanza.ResultSet{}
	switch ns {
	case gateway.NS_MAM2:
		answer.Payload = &extensions.MAM2Fin{
			ResultSet: &rs,
			Complete:  complete,
			Stable:    false,
		}
	case gateway.NS_MAM1:
		answer.Payload = &extensions.MAM1Fin{
			ResultSet: &rs,
			Complete:  complete,
			Stable:    false,
		}
	case gateway.NS_MAM0:
		answer.Payload = &extensions.MAM0Fin{
			ResultSet: &rs,
			Complete:  complete,
			Stable:    false,
		}
	}

	if answer.Payload == nil {
		log.Error("Unknown MAM version")
		return
	}

	if beyond {
		count := 0
		rs.Count = &count
		log.Debugf("MAM: beyond")
	} else {
		if len(messages) > 0 {
			firstMsgId := messages[0].Id
			lastMsgId := messages[len(messages)-1].Id
			if fromStart {
				if reverse {
					overallyFirstMessageId = lastMsgId
				} else {
					overallyFirstMessageId = firstMsgId
				}
			}
			if toEnd {
				if reverse {
					overallyLastMessageId = firstMsgId
				} else {
					overallyLastMessageId = lastMsgId
				}
			}
		}

		var firstMsgPositionCount, lastMsgPositionCount int32
		// estimate overall count
		if overallyFirstMessageId != 0 && overallyLastMessageId != 0 {
			firstMsgPosition, firstMsgPositionErr := session.GetChatMessagePosition(toID, overallyFirstMessageId)
			if firstMsgPositionErr == nil && firstMsgPosition != nil {
				firstMsgPositionCount = firstMsgPosition.Count
			}
			lastMsgPosition, lastMsgPositionErr := session.GetChatMessagePosition(toID, overallyLastMessageId)
			if lastMsgPositionErr == nil && lastMsgPosition != nil {
				lastMsgPositionCount = lastMsgPosition.Count
			}
			log.WithFields(log.Fields{
				"overallyFirstMessageId": overallyFirstMessageId,
				"overallyLastMessageId":  overallyLastMessageId,
				"firstMsgPositionCount":  firstMsgPositionCount,
				"lastMsgPositionCount":   lastMsgPositionCount,
			}).Debug("RSM count")
			if firstMsgPositionCount != 0 && lastMsgPositionCount != 0 {
				count := int(firstMsgPositionCount - lastMsgPositionCount + 1)
				rs.Count = &count
			}
		}

		if len(messages) > 0 {
			firstMsgId := messages[0].Id
			lastMsgId := messages[len(messages)-1].Id
			if reverse {
				firstMsgId, lastMsgId = lastMsgId, firstMsgId
			}
			rs.First = &stanza.First{
				Content: strconv.FormatInt(firstMsgId, 10),
			}
			if firstMsgPositionCount != 0 {
				rsmFirstMsgPosition, rsmFirstMsgPositionErr := session.GetChatMessagePosition(toID, firstMsgId)
				if rsmFirstMsgPositionErr == nil && rsmFirstMsgPosition != nil {
					index := int(firstMsgPositionCount - rsmFirstMsgPosition.Count)
					rs.First.Index = &index
				}
			}
			last := strconv.FormatInt(lastMsgId, 10)
			rs.Last = &last
		}
	}
	if log.GetLevel() == log.DebugLevel {
		xmlFin, err := xml.Marshal(answer.Payload)
		if err == nil {
			log.Debug(string(xmlFin))
		} else {
			log.Debugf("MAM fin: %#v %#v", answer.Payload, rs)
		}
	}
}

func iqAnswerSetError(answer *stanza.IQ, code int) {
	iqAnswerSetErrorInternal(answer, code, false)
}

func iqAnswerRegisterSetError(answer *stanza.IQ, payload *extensions.QueryRegister, code int) {
	answer.Payload = *payload
	iqAnswerSetErrorInternal(answer, code, true)
}

func iqAnswerSetErrorInternal(answer *stanza.IQ, code int, registerMode bool) {
	answer.Type = stanza.IQTypeError
	switch code {
	case 400:
		answer.Error = &stanza.Err{
			Type:   stanza.ErrorTypeModify,
			Reason: "bad-request",
		}
	case 401:
		answer.Error = &stanza.Err{
			Type:   stanza.ErrorTypeAuth,
			Reason: "not-authorized",
		}
	case 403:
		answer.Error = &stanza.Err{
			Type:   stanza.ErrorTypeAuth,
			Reason: "forbidden",
		}
	case 404:
		answer.Error = &stanza.Err{
			Type:   stanza.ErrorTypeCancel,
			Reason: "item-not-found",
		}
	case 405:
		answer.Error = &stanza.Err{
			Type:   stanza.ErrorTypeCancel,
			Reason: "not-allowed",
		}
	case 406:
		answer.Error = &stanza.Err{
			Type:   stanza.ErrorTypeModify,
			Reason: "not-acceptable",
		}
	case 500:
		answer.Error = &stanza.Err{
			Type:   stanza.ErrorTypeWait,
			Reason: "internal-server-error",
		}
	case 501:
		answer.Error = &stanza.Err{
			Type:   stanza.ErrorTypeCancel,
			Reason: "feature-not-implemented",
		}
	default:
		log.Error("Unknown error code, falling back with empty reason")
		answer.Error = &stanza.Err{
			Type:   stanza.ErrorTypeCancel,
			Reason: "undefined-condition",
		}
	}
	answer.Error.Code = code

	if registerMode {
		switch code {
		case 404:
			answer.Error.Text = "No such room"
		case 405:
			answer.Error.Text = "Logging out is dangerous. If you are sure you would be able to receive the authentication code again, issue the /logout command to the transport"
		case 406:
			answer.Error.Text = "Phone number already provided, chat with the transport for further instruction"
		}
	}
}

func presenceReplySetError(reply *stanza.Presence, code int) {
	reply.Type = stanza.PresenceTypeError
	reply.Error = stanza.Err{
		Code: code,
	}
	switch code {
	case 400:
		reply.Error.Type = stanza.ErrorTypeModify
		reply.Error.Reason = "jid-malformed"
	case 403:
		reply.Error.Type = stanza.ErrorTypeAuth
		reply.Error.Reason = "forbidden"
	case 404:
		reply.Error.Type = stanza.ErrorTypeCancel
		reply.Error.Reason = "item-not-found"
	case 405:
		reply.Error.Type = stanza.ErrorTypeCancel
		reply.Error.Reason = "not-allowed"
	case 407:
		reply.Error.Type = stanza.ErrorTypeAuth
		reply.Error.Reason = "registration-required"
	default:
		log.Error("Unknown error code, falling back with empty reason")
		reply.Error.Type = stanza.ErrorTypeCancel
		reply.Error.Reason = "undefined-condition"
	}
}

func setCommandPayloadError(payload *stanza.Command, err string) {
	note := stanza.Note{
		Text: err,
		Type: stanza.CommandNoteTypeErr,
	}
	payload.Status = stanza.CommandStatusCompleted
	payload.CommandElements = append(payload.CommandElements, &note)
}

func probeClientFeatures(jid string, component *xmpp.Component) {
	id, err := uuid.NewRandom()
	if err != nil {
		log.Error("Could not generate ID for a client features probe")
		return
	}

	probe := stanza.IQ{
		Attrs: stanza.Attrs{
			From: gateway.Jid.Bare(),
			To:   jid,
			Id:   id.String(),
			Type: stanza.IQTypeGet,
		},
		Payload: &stanza.DiscoInfo{},
	}
	log.Debugf("%#v", probe)

	gateway.ResumableSend(component, &probe)
}

func handleClientFeatures(s xmpp.Sender, iq *stanza.IQ, discoInfo *stanza.DiscoInfo) {
	fromJid, err := stanza.NewJid(iq.From)
	if err != nil {
		log.Error("Invalid from JID!")
		return
	}
	bareFrom := fromJid.Bare()

	session, ok := sessions[bareFrom]
	if !ok {
		log.Errorf("Got client features for unknown JID %v", bareFrom)
		return
	}

	var features []string
	var avatarNotify bool
	for _, feature := range discoInfo.Features {
		features = append(features, feature.Var)
		if feature.Var == gateway.NodeAvatarMetadataNotify {
			avatarNotify = true
		}
	}

	session.XmppClientFeaturesLock.Lock()
	session.XmppClientFeatures[fromJid.Resource] = &features
	session.XmppClientFeaturesLock.Unlock()

	log.Debugf("Features for %v: %#v", iq.From, features)

	if avatarNotify {
		go sendPubSubAvatarNotifications(s, iq.From, session)
	}
}

func sendPubSubAvatarNotifications(s xmpp.Sender, jid string, session *telegram.Client) {
	component, ok := s.(*xmpp.Component)
	if !ok {
		log.Error("Not a component")
		return
	}

	for _, chatId := range session.OwnChatsKeys() {
		chat, _, err := session.GetContactByID(chatId, nil, true)
		if err != nil || chat == nil {
			continue
		}

		if chat.Photo == nil {
			session.SetEmptyAvatarHash(chatId)
			continue
		}

		sha1 := session.GetPhotoSha1(chat.Photo.Small, chat.Id)
		size := session.GetPhotoSize(chat.Photo.Small)

		var chatJid string
		if session.Session.MUC && session.IsGroup(chat) {
			chatJid = gateway.MUCJID(chat.Id)
		} else {
			chatJid = gateway.CHATJID(chat.Id, false)
		}
		gateway.SendPubSubAvatarNotification(component, jid, chatJid, sha1, size)
	}
}

func toToID(to string) (int64, bool, bool) {
	var isGroup bool
	toParts := strings.Split(to, "@")
	if len(toParts) < 2 {
		return 0, false, isGroup
	}
	node := toParts[0]
	if strings.HasPrefix(node, "c") {
		isGroup = true
		node = node[1:]
	}
	toID, err := strconv.ParseInt(node, 10, 64)
	if err != nil {
		log.WithFields(log.Fields{
			"to": to,
		}).Error(errors.Wrap(err, "Invalid to JID!"))
		return 0, false, isGroup
	}
	return toID, true, isGroup
}

func parseMessageId(sId string) (int64, bool) {
	if sId[0] == 'e' {
		idParts := strings.Split(sId[1:], ":")
		if len(idParts) >= 1 {
			sId = idParts[0]
		}
	} else if sId[0] == 'c' {
		sId = sId[1:]
	}
	id, err := strconv.ParseInt(sId, 10, 64)
	if err != nil {
		log.Warn(errors.Wrap(err, "Failed to parse message ID!"))
		return 0, false
	}
	return id, true
}

func makeVCardPayload(typ byte, id string, info telegram.VCardInfo, session *telegram.Client) stanza.IQPayload {
	var base64Photo string
	if info.Photo != nil {
		base64Photo = session.GetPhotoBase64(info.Photo)
	}

	if typ == TypeVCardTemp {
		vcard := &extensions.IqVcardTemp{}

		vcard.Fn.Text = info.Fn
		if base64Photo != "" {
			vcard.Photo.Type.Text = "image/jpeg"
			vcard.Photo.Binval.Text = base64Photo
		}
		vcard.Nickname.Text = strings.Join(info.Nicknames, ",")
		vcard.N.Given.Text = info.Given
		vcard.N.Family.Text = info.Family
		vcard.Tel.Number.Text = info.Tel
		vcard.Desc.Text = info.Info

		return vcard
	} else if typ == TypeVCard4 {
		nodes := []stanza.Node{}
		if info.Fn != "" {
			nodes = append(nodes, stanza.Node{
				XMLName: xml.Name{Local: "fn"},
				Nodes: []stanza.Node{
					stanza.Node{
						XMLName: xml.Name{Local: "text"},
						Content: info.Fn,
					},
				},
			})
		}
		if base64Photo != "" {
			nodes = append(nodes, stanza.Node{
				XMLName: xml.Name{Local: "photo"},
				Nodes: []stanza.Node{
					stanza.Node{
						XMLName: xml.Name{Local: "uri"},
						Content: "data:image/jpeg;base64," + base64Photo,
					},
				},
			})
		}
		for _, nickname := range info.Nicknames {
			nodes = append(nodes, stanza.Node{
				XMLName: xml.Name{Local: "nickname"},
				Nodes: []stanza.Node{
					stanza.Node{
						XMLName: xml.Name{Local: "text"},
						Content: nickname,
					},
				},
			}, stanza.Node{
				XMLName: xml.Name{Local: "impp"},
				Nodes: []stanza.Node{
					stanza.Node{
						XMLName: xml.Name{Local: "uri"},
						Content: "https://t.me/" + nickname,
					},
				},
			})
		}
		if info.Family != "" || info.Given != "" {
			nodes = append(nodes, stanza.Node{
				XMLName: xml.Name{Local: "n"},
				Nodes: []stanza.Node{
					stanza.Node{
						XMLName: xml.Name{Local: "surname"},
						Content: info.Family,
					},
					stanza.Node{
						XMLName: xml.Name{Local: "given"},
						Content: info.Given,
					},
				},
			})
		}
		if info.Tel != "" {
			nodes = append(nodes, stanza.Node{
				XMLName: xml.Name{Local: "tel"},
				Nodes: []stanza.Node{
					stanza.Node{
						XMLName: xml.Name{Local: "uri"},
						Content: "tel:" + info.Tel,
					},
				},
			})
		}
		if info.Info != "" {
			nodes = append(nodes, stanza.Node{
				XMLName: xml.Name{Local: "note"},
				Nodes: []stanza.Node{
					stanza.Node{
						XMLName: xml.Name{Local: "text"},
						Content: info.Info,
					},
				},
			})
		}

		pubsub := &stanza.PubSubGeneric{
			Items: &stanza.Items{
				Node: gateway.NodeVCard4,
				List: []stanza.Item{
					stanza.Item{
						Id: id,
						Any: &stanza.Node{
							XMLName: xml.Name{Local: "vcard"},
							Attrs: []xml.Attr{
								xml.Attr{
									Name:  xml.Name{Local: "xmlns"},
									Value: "urn:ietf:params:xml:ns:vcard-4.0",
								},
							},
							Nodes: nodes,
						},
					},
				},
			},
		}

		return pubsub
	}

	return nil
}

// ToBool returns bool, ok
func ToBool(b string) (bool, bool) {
	switch b {
	case "0", "false":
		return false, true
	case "1", "true":
		return true, true
	}

	return false, false
}