Reactions

config.yml.example

@@ -8,6 +8,7 @@
         :quota: '256MB' # maximum storage size
     :tdlib_verbosity: 1
     :mam_threshold: 7 # in days
+    :max_reactions_per_emoji: 10 # named reactors relayed per (message, emoji) in group/channel XEP-0444 reactions
     :tdlib:
         :datadir: './sessions/'
         :client:

config/config.go

@@ -58,6 +58,11 @@ type TelegramConfig struct {
 	// HistoryBackfillWorkers bounds how many chats backfill concurrently
 	// (see gateway.HistoryBackfillWorkers). 0/unset falls back to 4.
 	HistoryBackfillWorkers uint32 `yaml:":history_backfill_workers"`
+
+	// MaxReactionsPerEmoji caps named reactors relayed per (message,
+	// emoji) in group/channel reactions (see gateway.MaxReactionsPerEmoji).
+	// 0/unset falls back to a default of 10.
+	MaxReactionsPerEmoji uint32 `yaml:":max_reactions_per_emoji"`
 }
 
 // TelegramContentConfig is for :content: subtree

go.mod

@@ -71,7 +71,7 @@ require (
 	nhooyr.io/websocket v1.6.5 // indirect
 )
 
-replace gosrc.io/xmpp => dev.narayana.im/narayana/go-xmpp v0.0.0-20250823114312-ed4011fc17e4
+replace gosrc.io/xmpp => dev.narayana.im/narayana/go-xmpp v0.0.0-20260821210951-a027f257a96d
 
 replace github.com/zelenin/go-tdlib => dev.narayana.im/narayana/go-tdlib v0.0.0-20240124222245-b4c12addb061
 

go.sum

@@ -1,8 +1,8 @@
 cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
 dev.narayana.im/narayana/go-tdlib v0.0.0-20240124222245-b4c12addb061 h1:CWAQT74LwQne/3Po5KXDvudu3N0FBWm3XZZZhtl5j2w=
 dev.narayana.im/narayana/go-tdlib v0.0.0-20240124222245-b4c12addb061/go.mod h1:Xs8fXbk5n7VaPyrSs9DP7QYoBScWYsjX+lUcWmx1DIU=
-dev.narayana.im/narayana/go-xmpp v0.0.0-20250823114312-ed4011fc17e4 h1:HQT33Zp3iRkbCiijWDo943K//wQgzoMccIP7Vb2uEfY=
+dev.narayana.im/narayana/go-xmpp v0.0.0-20260821210951-a027f257a96d h1:oeYqHbaAQPV4ID4X47fHOeSS5s4y4hZlog4hOsZuMkE=
-dev.narayana.im/narayana/go-xmpp v0.0.0-20250823114312-ed4011fc17e4/go.mod h1:L3NFMqYOxyLz3JGmgFyWf7r9htE91zVGiK40oW4RwdY=
+dev.narayana.im/narayana/go-xmpp v0.0.0-20260821210951-a027f257a96d/go.mod h1:L3NFMqYOxyLz3JGmgFyWf7r9htE91zVGiK40oW4RwdY=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/Laky-64/gologging v1.1.0 h1:iV/VgoIbImLrI3EPssOzzoyv1OQrp6t5RtDQTKzUes8=
 github.com/Laky-64/gologging v1.1.0/go.mod h1:Ody93tsM0OZUAsWApkfb3rg35fAvyZDAx07kNH13DhI=

telegram/client.go

@@ -166,6 +166,23 @@ type Client struct {
 	MessageIdChanges     map[int64]map[int64]*newId
 	MessageIdChangesLock sync.Mutex
 
+	// lastPeerReactions dedups outgoing XEP-0444 announcements - see
+	// peerReactionsChanged in reactions.go.
+	lastPeerReactions     map[reactionKey]string
+	lastPeerReactionsLock sync.Mutex
+
+	// activeEmojiReactions is Telegram's current global built-in reaction
+	// set, seeded from defaultActiveEmojiReactions and kept live by
+	// updateActiveEmojiReactions - see chatAllowsReaction in reactions.go.
+	activeEmojiReactions     map[string]bool
+	activeEmojiReactionsLock sync.Mutex
+
+	// customEmojiFallbacks caches a custom emoji reaction's plain-emoji
+	// fallback (Sticker.Emoji, resolved via GetCustomEmojiStickers) - see
+	// resolveReactionEmoji in reactions.go.
+	customEmojiFallbacks     map[int64]string
+	customEmojiFallbacksLock sync.Mutex
+
 	// guards the call trio. Connect() builds it after c.client is live;
 	// close() tears it down before c.client is closed. Accessors return
 	// nil when no live session.
@@ -319,6 +336,9 @@ func NewClient(conf config.TelegramConfig, jid string, component *xmpp.Component
 		XmppClientFeatures:   make(map[string]*[]string),
 		avatarHashes:         make(map[int64]*HashedAvatar),
 		MessageIdChanges:     make(map[int64]map[int64]*newId),
+		lastPeerReactions:    make(map[reactionKey]string),
+		activeEmojiReactions: newDefaultActiveEmojiReactions(),
+		customEmojiFallbacks: make(map[int64]string),
 		locks: clientLocks{
 			chatMessageLocks:    make(map[int64]*sync.Mutex),
 			deliveredMessageIds: make(map[int64]int64),

telegram/handlers.go

@@ -165,6 +165,12 @@ func (c *Client) dispatchUpdate(update client.Type) {
 		case client.TypeUpdateDeleteMessages:
 			typedUpdate, _ := update.(*client.UpdateDeleteMessages)
 			c.updateDeleteMessages(typedUpdate)
+		case client.TypeUpdateMessageInteractionInfo:
+			typedUpdate, _ := update.(*client.UpdateMessageInteractionInfo)
+			c.updateMessageInteractionInfo(typedUpdate)
+		case client.TypeUpdateActiveEmojiReactions:
+			typedUpdate, _ := update.(*client.UpdateActiveEmojiReactions)
+			c.updateActiveEmojiReactions(typedUpdate)
 		case client.TypeUpdateAuthorizationState:
 			typedUpdate, _ := update.(*client.UpdateAuthorizationState)
 			c.updateAuthorizationState(typedUpdate)

telegram/reactions.go

@@ -0,0 +1,523 @@
+package telegram
+
+import (
+	"sort"
+	"strconv"
+	"strings"
+
+	"dev.narayana.im/narayana/telegabber/xmpp/gateway"
+
+	"github.com/pkg/errors"
+	log "github.com/sirupsen/logrus"
+	"github.com/zelenin/go-tdlib/client"
+)
+
+// defaultActiveEmojiReactions seeds Client.activeEmojiReactions until the
+// first live updateActiveEmojiReactions arrives (normally within the
+// initial post-authorization update burst, so this seed's exposure window
+// is brief). There's no versioned schema for this set, so treat it as a
+// best-effort snapshot, not a ceiling: a chat's own restricted list
+// (ChatAvailableReactionsSome) always wins over it, and a Telegram-side
+// rejection is still the final authority regardless of what's in this
+// list. Compiled from the public list at
+// https://gist.github.com/Soulter/3f22c8e5f9c7e152e967e8bc28c97fc9
+// (Telegram's pre-custom-emoji "expanded" reaction set, ~2022).
+var defaultActiveEmojiReactions = []string{
+	"👍", "👎", "❤", "🔥", "🥰", "👏", "😁", "🤔", "🤯", "😱", "🤬", "😢",
+	"🎉", "🤩", "🤮", "💩", "🙏", "👌", "🕊", "🤡", "🥱", "🥴", "😍", "🐳",
+	"❤️‍🔥", "🌚", "🌭", "💯", "🤣", "⚡", "🍌", "🏆", "💔", "🤨", "😐", "🍓",
+	"🍾", "💋", "🖕", "😈", "😴", "😭", "🤓", "👻", "👨‍💻", "👀", "🎃", "🙈",
+	"😇", "😨", "🤝", "✍", "🤗", "🫡", "🎅", "🎄", "☃", "💅", "🤪", "🗿",
+	"🆒", "💘", "🙉", "🦄", "😘", "💊", "🙊", "😎", "👾", "🤷‍♂️", "🤷", "🤷‍♀️",
+	"😡",
+}
+
+func newDefaultActiveEmojiReactions() map[string]bool {
+	m := make(map[string]bool, len(defaultActiveEmojiReactions))
+	for _, e := range defaultActiveEmojiReactions {
+		m[e] = true
+	}
+	return m
+}
+
+// updateActiveEmojiReactions replaces the cached global reaction set with
+// TDlib's authoritative, current one.
+func (c *Client) updateActiveEmojiReactions(update *client.UpdateActiveEmojiReactions) {
+	m := make(map[string]bool, len(update.Emojis))
+	for _, e := range update.Emojis {
+		m[e] = true
+	}
+
+	c.activeEmojiReactionsLock.Lock()
+	c.activeEmojiReactions = m
+	c.activeEmojiReactionsLock.Unlock()
+}
+
+// chatAllowsReaction reports whether emoji is a plain-text reaction chat
+// currently accepts: chat's own restricted list if Telegram has set one
+// (ChatAvailableReactionsSome), otherwise the global active set.
+func (c *Client) chatAllowsReaction(chat *client.Chat, emoji string) bool {
+	if chat != nil {
+		if some, ok := chat.AvailableReactions.(*client.ChatAvailableReactionsSome); ok {
+			for _, rt := range some.Reactions {
+				if e, ok := rt.(*client.ReactionTypeEmoji); ok && e.Emoji == emoji {
+					return true
+				}
+			}
+			return false
+		}
+	}
+
+	c.activeEmojiReactionsLock.Lock()
+	defer c.activeEmojiReactionsLock.Unlock()
+	return c.activeEmojiReactions[emoji]
+}
+
+// paidReactionFallback stands in for ReactionTypePaid, which has no
+// emoji field of its own - Telegram's UI name for it ("Star reaction"),
+// not a protocol value.
+//
+// TODO: ReactionTypePaid doesn't exist in the go-tdlib revision this
+// project currently pins (predates Telegram's Stars-reactions feature) -
+// wire up the case below once that's bumped.
+const paidReactionFallback = "⭐"
+
+// resolveReactionEmoji returns rt's XEP-0444 plain-text equivalent, or
+// ok=false if it has none.
+func (c *Client) resolveReactionEmoji(rt client.ReactionType) (emoji string, ok bool) {
+	switch v := rt.(type) {
+	case *client.ReactionTypeEmoji:
+		return v.Emoji, true
+	case *client.ReactionTypeCustomEmoji:
+		return c.customEmojiFallback(int64(v.CustomEmojiId))
+	// case *client.ReactionTypePaid:
+	// 	return paidReactionFallback, true
+	default:
+		return "", false
+	}
+}
+
+func (c *Client) customEmojiFallback(customEmojiId int64) (string, bool) {
+	c.customEmojiFallbacksLock.Lock()
+	emoji, cached := c.customEmojiFallbacks[customEmojiId]
+	c.customEmojiFallbacksLock.Unlock()
+	if cached {
+		return emoji, true
+	}
+
+	stickers, err := c.client.GetCustomEmojiStickers(&client.GetCustomEmojiStickersRequest{
+		CustomEmojiIds: []client.JsonInt64{client.JsonInt64(customEmojiId)},
+	})
+	if err != nil || len(stickers.Stickers) == 0 {
+		return "", false
+	}
+
+	emoji = stickers.Stickers[0].Emoji
+	if emoji == "" {
+		return "", false
+	}
+
+	c.customEmojiFallbacksLock.Lock()
+	c.customEmojiFallbacks[customEmojiId] = emoji
+	c.customEmojiFallbacksLock.Unlock()
+	return emoji, true
+}
+
+// ReactionRestrictions reports chatId's allowed emoji and its per-message,
+// per-user reaction cap, for XEP-0444's disco#info restricted-reactions
+// form (urn:xmpp:reactions:0:restrictions). ok is false only if chatId
+// can't be resolved to a chat.
+//
+// TDlib doesn't expose the per-user cap as a queryable field; 1 for
+// non-Premium and 3 for Premium accounts matches Telegram's own
+// description of the feature (telegram.org/blog/infinite-reactions-statuses).
+func (c *Client) ReactionRestrictions(chatId int64) (allowlist []string, maxPerUser int, ok bool) {
+	chat, _, err := c.GetContactByID(chatId, nil, true)
+	if err != nil || chat == nil {
+		return nil, 0, false
+	}
+
+	if some, isSome := chat.AvailableReactions.(*client.ChatAvailableReactionsSome); isSome {
+		for _, rt := range some.Reactions {
+			if e, isEmoji := rt.(*client.ReactionTypeEmoji); isEmoji {
+				allowlist = append(allowlist, e.Emoji)
+			}
+		}
+	} else {
+		c.activeEmojiReactionsLock.Lock()
+		allowlist = mapKeys(c.activeEmojiReactions)
+		c.activeEmojiReactionsLock.Unlock()
+	}
+
+	sort.Strings(allowlist)
+
+	maxPerUser = 1
+	if c.me != nil && c.me.IsPremium {
+		maxPerUser = 3
+	}
+
+	return allowlist, maxPerUser, true
+}
+
+// reactionKey identifies one reactor's signature slot in lastPeerReactions.
+// SenderId is 0 for the peer side of a 1:1 chat (there's only one possible
+// non-self reactor there); in groups/channels it's the Telegram user id of
+// a named occupant, or ChatId itself for the pooled anonymous bucket (see
+// collectGroupReactions).
+type reactionKey struct {
+	ChatId    int64
+	MessageId int64
+	SenderId  int64
+}
+
+// updateMessageInteractionInfo relays a Telegram reaction change to XMPP,
+// restricted to resources that disco'd support for urn:xmpp:reactions:0
+// (GetReactionCapableFullJids / GetMUCReactionCapableFullJids) - anything
+// else is dropped rather than falling back to a flood of plaintext
+// notices for every reaction toggle.
+func (c *Client) updateMessageInteractionInfo(update *client.UpdateMessageInteractionInfo) {
+	if c.Session.IsChatIgnored(update.ChatId) {
+		return
+	}
+
+	chat, _, err := c.GetContactByID(update.ChatId, nil, true)
+	if err != nil || chat == nil {
+		return
+	}
+	isMUC := c.Session.MUC && c.IsGroup(chat)
+
+	xmppId, err := gateway.IdsDB.GetByTgIds(c.Session.Login, c.jid, update.ChatId, update.MessageId)
+	if err != nil {
+		xmppId = strconv.FormatInt(update.MessageId, 10)
+	}
+
+	if !isMUC {
+		selfEmojis, peerEmojis := c.splitPMReactions(update.InteractionInfo)
+
+		// Own reaction state can change from a different Telegram client,
+		// which has no other way to reach XMPP - relayed as a carbon
+		// (privileged component injection) since a component can't claim
+		// from=<the real user's JID> otherwise. Carbons fan out via the
+		// real server, so unlike the peer relay below this can't be
+		// filtered to reaction-capable resources only.
+		if c.me != nil && c.peerReactionsChanged(update.ChatId, update.MessageId, c.me.Id, selfEmojis) {
+			gateway.SendMessage(c.jid, gateway.CHATNODE(update.ChatId), c.xmpp,
+				gateway.SMReactions(&gateway.Reactions{Id: xmppId, Reactions: selfEmojis}),
+				gateway.SMIsCarbon(true),
+			)
+		}
+
+		if jids := c.GetReactionCapableFullJids(); len(jids) > 0 && c.peerReactionsChanged(update.ChatId, update.MessageId, 0, peerEmojis) {
+			from := gateway.CHATNODE(update.ChatId)
+			for _, jid := range jids {
+				gateway.SendReactionMessage(jid, from, c.xmpp, xmppId, peerEmojis, false)
+			}
+		}
+		return
+	}
+
+	jids := c.GetMUCReactionCapableFullJids(update.ChatId)
+	if len(jids) == 0 {
+		return
+	}
+
+	perOccupant, anonymousEmojis := c.collectGroupReactions(update.ChatId, update.MessageId, update.InteractionInfo)
+	mucJid := gateway.MUCJID(update.ChatId)
+
+	for senderId, senderEmojis := range perOccupant {
+		if !c.peerReactionsChanged(update.ChatId, update.MessageId, senderId, senderEmojis) {
+			continue
+		}
+		if !c.assureMUCOccupant(update.ChatId, senderId, &client.MessageSenderUser{UserId: senderId}, chat) {
+			continue
+		}
+		from := mucJid + "/" + c.GetMUCNickname(senderId)
+		for _, jid := range jids {
+			gateway.SendReactionMessage(jid, from, c.xmpp, xmppId, senderEmojis, true)
+		}
+	}
+
+	// Anonymous reactions (broadcast channel posts, or a group's
+	// "anonymous admin" reacting as the group) can't be attributed to a
+	// person, so they're pooled under the chat's own identity instead -
+	// same convention regular messages already use for anonymous-admin
+	// authorship (see getMessageSenderId/GetMUCNickname).
+	if c.peerReactionsChanged(update.ChatId, update.MessageId, update.ChatId, anonymousEmojis) {
+		anonymousSender := &client.MessageSenderChat{ChatId: update.ChatId}
+		if c.assureMUCOccupant(update.ChatId, update.ChatId, anonymousSender, chat) {
+			from := mucJid + "/" + c.GetMUCNickname(update.ChatId)
+			for _, jid := range jids {
+				gateway.SendReactionMessage(jid, from, c.xmpp, xmppId, anonymousEmojis, true)
+			}
+		}
+	}
+}
+
+// splitPMReactions splits a 1:1 message's reactions into self's own
+// current set and the peer's - IsChosen only means self is among a given
+// emoji's reactors, not that they're the only one (TotalCount still
+// includes the peer if both picked the same emoji).
+func (c *Client) splitPMReactions(info *client.MessageInteractionInfo) (selfEmojis, peerEmojis []string) {
+	if info == nil {
+		return nil, nil
+	}
+	for _, r := range info.Reactions {
+		emoji, ok := c.resolveReactionEmoji(r.Type)
+		if !ok {
+			continue
+		}
+		peerCount := r.TotalCount
+		if r.IsChosen {
+			peerCount--
+			selfEmojis = append(selfEmojis, emoji)
+		}
+		if peerCount > 0 {
+			peerEmojis = append(peerEmojis, emoji)
+		}
+	}
+	return selfEmojis, peerEmojis
+}
+
+// SendDelayedMUCReactions synthesizes XEP-0444 MAM-result stanzas for
+// message's current reactors, one call site down from
+// SendDelayedMUCMessage in a MAM replay loop. Unlike live relay it
+// doesn't call assureMUCOccupant, matching SendDelayedMUCMessage's own
+// MAM-replay convention of not establishing presence for a historical
+// sender; toJid only receives anything if its resource disco'd support
+// for urn:xmpp:reactions:0.
+func (c *Client) SendDelayedMUCReactions(chatId int64, message *client.Message, toJid string, mamQueryId string) {
+	_, resource, ok := gateway.SplitJID(toJid)
+	if !ok || !c.resourceSupportsReactions(resource) {
+		return
+	}
+
+	perOccupant, anonymousEmojis := c.collectGroupReactions(chatId, message.Id, message.InteractionInfo)
+	if len(perOccupant) == 0 && len(anonymousEmojis) == 0 {
+		return
+	}
+
+	xmppId, err := gateway.IdsDB.GetByTgIds(c.Session.Login, c.jid, chatId, message.Id)
+	if err != nil {
+		xmppId = strconv.FormatInt(message.Id, 10)
+	}
+
+	mucJid := gateway.MUCJID(chatId)
+	strId := strconv.FormatInt(message.Id, 10)
+	timestamp := int64(message.Date)
+
+	for senderId, senderEmojis := range perOccupant {
+		from := mucJid + "/" + c.GetMUCNickname(senderId)
+		entryId := "r" + strId + "-" + strconv.FormatInt(senderId, 10)
+		gateway.SendMAMReactionMessage(toJid, from, c.xmpp, xmppId, senderEmojis, entryId, timestamp, mucJid, mamQueryId)
+	}
+	if len(anonymousEmojis) > 0 {
+		from := mucJid + "/" + c.GetMUCNickname(chatId)
+		gateway.SendMAMReactionMessage(toJid, from, c.xmpp, xmppId, anonymousEmojis, "r"+strId+"-a", timestamp, mucJid, mamQueryId)
+	}
+}
+
+// collectGroupReactions expands a message's aggregate per-emoji reaction
+// counts into per-reactor emoji sets, since a XEP-0444 stanza carries one
+// sender's complete reaction set, not one emoji at a time.
+//
+// TDlib only samples up to 3 recent reactors per emoji for free
+// (MessageReaction.RecentSenderIds); beyond that, getMessageAddedReactions
+// is called to enumerate the rest, up to gateway.MaxReactionsPerEmoji -
+// remaining reactors past that cap are silently dropped (not queued, not
+// substituted with a placeholder) to bound the number of XMPP stanzas a
+// single popular reaction can generate. Anonymous reactors are exempt
+// from the cap since they all collapse into the one pooled bucket
+// regardless of count.
+func (c *Client) collectGroupReactions(chatId, messageId int64, info *client.MessageInteractionInfo) (perOccupant map[int64][]string, anonymousEmojis []string) {
+	if info == nil {
+		return nil, nil
+	}
+
+	limit := int(gateway.MaxReactionsPerEmoji)
+	if limit <= 0 {
+		limit = 10
+	}
+	apiLimit := limit
+	if apiLimit > 100 {
+		apiLimit = 100
+	}
+
+	perOccupant = make(map[int64][]string)
+	sawAnonymous := make(map[string]bool)
+
+	for _, r := range info.Reactions {
+		emoji, ok := c.resolveReactionEmoji(r.Type)
+		if !ok {
+			continue // paid reactions have no plain-text XEP-0444 equivalent
+		}
+
+		var senders []client.MessageSender
+		var enumerated bool
+		if int(r.TotalCount) > len(r.RecentSenderIds) {
+			added, err := c.client.GetMessageAddedReactions(&client.GetMessageAddedReactionsRequest{
+				ChatId:       chatId,
+				MessageId:    messageId,
+				ReactionType: r.Type,
+				Limit:        int32(apiLimit),
+			})
+			if err == nil {
+				enumerated = true
+				for _, a := range added.Reactions {
+					senders = append(senders, a.SenderId)
+				}
+			}
+		}
+		if !enumerated {
+			senders = r.RecentSenderIds
+		}
+
+		named := 0
+		for _, sender := range senders {
+			switch sender.MessageSenderType() {
+			case client.TypeMessageSenderUser:
+				if named >= limit {
+					continue
+				}
+				userId := sender.(*client.MessageSenderUser).UserId
+				perOccupant[userId] = append(perOccupant[userId], emoji)
+				named++
+			case client.TypeMessageSenderChat:
+				if !sawAnonymous[emoji] {
+					sawAnonymous[emoji] = true
+					anonymousEmojis = append(anonymousEmojis, emoji)
+				}
+			}
+		}
+	}
+
+	return perOccupant, anonymousEmojis
+}
+
+// peerReactionsChanged dedups against the last announced signature for
+// key. UpdateMessageInteractionInfo also fires for reasons unrelated to a
+// reaction change (e.g. view/forward counts), which would otherwise
+// re-announce the same <reactions/> state on every such update.
+func (c *Client) peerReactionsChanged(chatId, messageId, senderId int64, emojis []string) bool {
+	sorted := append([]string(nil), emojis...)
+	sort.Strings(sorted)
+	sig := strings.Join(sorted, "\x00")
+
+	key := reactionKey{ChatId: chatId, MessageId: messageId, SenderId: senderId}
+
+	c.lastPeerReactionsLock.Lock()
+	defer c.lastPeerReactionsLock.Unlock()
+
+	prev, known := c.lastPeerReactions[key]
+	if prev == sig {
+		return false
+	}
+	if sig == "" && !known {
+		// Not caching this keeps a later first real reaction correctly
+		// triggering below, instead of "no prior entry" being confused
+		// with "was reacted to, now cleared".
+		return false
+	}
+	c.lastPeerReactions[key] = sig
+	return true
+}
+
+// ownReactions returns chatId/messageId's currently self-chosen plain
+// emoji - deliberately not resolveReactionEmoji: removing a custom/paid
+// reaction needs its exact original type, not its fallback text, so
+// treating one as already-applied here would make it unremovable below.
+func (c *Client) ownReactions(chatId, messageId int64) (map[string]bool, error) {
+	message, err := c.client.GetMessage(&client.GetMessageRequest{
+		ChatId:    chatId,
+		MessageId: messageId,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	current := make(map[string]bool)
+	if message.InteractionInfo != nil {
+		for _, r := range message.InteractionInfo.Reactions {
+			if !r.IsChosen {
+				continue
+			}
+			if emoji, isEmoji := r.Type.(*client.ReactionTypeEmoji); isEmoji {
+				current[emoji.Emoji] = true
+			}
+		}
+	}
+	return current, nil
+}
+
+func mapKeys(m map[string]bool) []string {
+	keys := make([]string, 0, len(m))
+	for k := range m {
+		keys = append(keys, k)
+	}
+	return keys
+}
+
+// SetOwnMessageReactions reconciles the real user's chosen reactions on a
+// Telegram message with the complete set announced by an incoming
+// XEP-0444 <reactions/> stanza (always a full replacement, never a diff) -
+// diffing against TDlib's own reaction state since Telegram's per-user
+// reaction API is add/remove, not "set the following list" (TDlib's
+// setMessageReactions is bot-only).
+//
+// Per XEP-0444 S3.3, an invalid payload is rejected wholesale, before
+// touching Telegram (rejected then holds every requested emoji). A
+// rejection from Telegram's own API past that point is applied per-emoji
+// instead, not reverted - there's no atomic "set reactions" call
+// available to a non-bot account.
+func (c *Client) SetOwnMessageReactions(chatId, messageId int64, emojis []string) (applied []string, rejected []string) {
+	current, err := c.ownReactions(chatId, messageId)
+	if err != nil {
+		log.Error(errors.Wrap(err, "Failed to fetch message to reconcile reactions"))
+		return nil, nil
+	}
+	chat, _, _ := c.GetContactByID(chatId, nil, true)
+
+	for _, emoji := range emojis {
+		if !c.chatAllowsReaction(chat, emoji) {
+			log.Warnf("Reaction update for %d/%d rejected wholesale: %q not in chat's allowed set", chatId, messageId, emoji)
+			return mapKeys(current), emojis
+		}
+	}
+
+	wanted := make(map[string]bool, len(emojis))
+	for _, e := range emojis {
+		wanted[e] = true
+	}
+
+	for emoji := range wanted {
+		if current[emoji] {
+			continue
+		}
+		if _, err := c.client.AddMessageReaction(&client.AddMessageReactionRequest{
+			ChatId:                chatId,
+			MessageId:             messageId,
+			ReactionType:          &client.ReactionTypeEmoji{Emoji: emoji},
+			UpdateRecentReactions: true,
+		}); err != nil {
+			log.Warn(errors.Wrapf(err, "Reaction %q rejected", emoji))
+			rejected = append(rejected, emoji)
+			continue
+		}
+		current[emoji] = true
+	}
+	for emoji := range current {
+		if wanted[emoji] {
+			continue
+		}
+		if _, err := c.client.RemoveMessageReaction(&client.RemoveMessageReactionRequest{
+			ChatId:       chatId,
+			MessageId:    messageId,
+			ReactionType: &client.ReactionTypeEmoji{Emoji: emoji},
+		}); err != nil {
+			log.Error(errors.Wrap(err, "Failed to remove reaction"))
+			continue
+		}
+		delete(current, emoji)
+	}
+
+	return mapKeys(current), rejected
+}

telegram/utils.go

@@ -30,6 +30,7 @@ import (
 	"github.com/soheilhy/args"
 	"github.com/zelenin/go-tdlib/client"
 	"golang.org/x/sys/unix"
+	"gosrc.io/xmpp/stanza"
 )
 
 type VCardInfo struct {
@@ -609,7 +610,11 @@ func (c *Client) ProcessStatusUpdate(chatID int64, status string, show string, o
 	if isMUC {
 		newArgs = append(newArgs, gateway.SPFullFrom(gateway.MUCJID(chatID)))
 	} else {
-		newArgs = append(newArgs, gateway.SPCaps(gateway.PMCapsVer()))
+		var restrictionsForm *stanza.Form
+		if allowlist, maxPerUser, ok := c.ReactionRestrictions(chatID); ok {
+			restrictionsForm = gateway.ReactionRestrictionsForm(allowlist, maxPerUser)
+		}
+		newArgs = append(newArgs, gateway.SPCaps(gateway.PMCapsVer(restrictionsForm)))
 		newArgs = gateway.SPAppendFrom(newArgs, chatID)
 	}
 
@@ -3152,6 +3157,59 @@ func (c *Client) GetCarbonFullJids(isOutgoing bool, ignoredResource string, forc
 	return jids
 }
 
+// resourceSupportsReactions reports whether resource disco'd support for
+// XEP-0444 (gateway.NSReactions).
+func (c *Client) resourceSupportsReactions(resource string) bool {
+	c.XmppClientFeaturesLock.Lock()
+	features, ok := c.XmppClientFeatures[resource]
+	c.XmppClientFeaturesLock.Unlock()
+	if !ok || features == nil {
+		return false
+	}
+	for _, feature := range *features {
+		if feature == gateway.NSReactions {
+			return true
+		}
+	}
+	return false
+}
+
+// GetReactionCapableFullJids is like GetCarbonFullJids but for reactions:
+// unlike that one, there is no bare-JID fallback - an unprobed or
+// non-supporting resource is just skipped, never sent a legacy plaintext
+// notice instead.
+func (c *Client) GetReactionCapableFullJids() []string {
+	var jids []string
+	for _, resource := range c.resourcesSnapshot() {
+		if c.resourceSupportsReactions(resource) {
+			jids = append(jids, c.jid+"/"+resource)
+		}
+	}
+	return jids
+}
+
+// GetMUCReactionCapableFullJids is GetReactionCapableFullJids scoped to
+// the resources actually joined to chatId's room.
+func (c *Client) GetMUCReactionCapableFullJids(chatId int64) []string {
+	c.locks.mucCacheLock.Lock()
+	mucState := c.mucCache[chatId]
+	var resources []string
+	if mucState != nil {
+		for resource := range mucState.Resources {
+			resources = append(resources, resource)
+		}
+	}
+	c.locks.mucCacheLock.Unlock()
+
+	var jids []string
+	for _, resource := range resources {
+		if c.resourceSupportsReactions(resource) {
+			jids = append(jids, c.jid+"/"+resource)
+		}
+	}
+	return jids
+}
+
 func (c *Client) UpdateLastChatMessageId(chatId int64, messageId string) {
 	c.locks.lastMsgIdsLock.Lock()
 	defer c.locks.lastMsgIdsLock.Unlock()

xmpp/component.go

@@ -112,6 +112,10 @@ func NewComponent(conf config.XMPPConfig, tc config.TelegramConfig, idsPath stri
 		gateway.HistoryBackfillWorkers = tc.HistoryBackfillWorkers
 	}
 
+	if tc.MaxReactionsPerEmoji > 0 {
+		gateway.MaxReactionsPerEmoji = tc.MaxReactionsPerEmoji
+	}
+
 	options := xmpp.ComponentOptions{
 		TransportConfiguration: xmpp.TransportConfiguration{
 			Address: conf.Host + ":" + conf.Port,

xmpp/extensions/extensions.go

@@ -499,6 +499,19 @@ type AttachTo struct {
 	Id      string   `xml:"id,attr"`
 }
 
+// Reactions is from XEP-0444
+type Reactions struct {
+	XMLName   xml.Name   `xml:"urn:xmpp:reactions:0 reactions"`
+	Id        string     `xml:"id,attr"`
+	Reactions []Reaction `xml:"urn:xmpp:reactions:0 reaction"`
+}
+
+// Reaction is a child element of Reactions, from XEP-0444
+type Reaction struct {
+	XMLName xml.Name `xml:"urn:xmpp:reactions:0 reaction"`
+	Text    string   `xml:",chardata"`
+}
+
 // Namespace is a namespace!
 func (c PresenceNickExtension) Namespace() string {
 	return c.XMLName.Space
@@ -734,6 +747,11 @@ func (c AttachTo) Namespace() string {
 	return c.XMLName.Space
 }
 
+// Namespace is a namespace!
+func (c Reactions) Namespace() string {
+	return c.XMLName.Space
+}
+
 // NewReplyFallback initializes a fallback range
 func NewReplyFallback(start uint64, end uint64) Fallback {
 	return Fallback{
@@ -939,4 +957,10 @@ func init() {
 		"urn:xmpp:message-attaching:1",
 		"attach-to",
 	}, AttachTo{})
+
+	// reactions
+	stanza.TypeRegistry.MapExtension(stanza.PKTMessage, xml.Name{
+		"urn:xmpp:reactions:0",
+		"reactions",
+	}, Reactions{})
 }

xmpp/gateway/gateway.go

@@ -33,6 +33,14 @@ type Reply struct {
 	End    uint64
 }
 
+// Reactions is a XEP-0444 reaction set: the sender's complete current
+// list of emoji on the message identified by Id (always a full
+// replacement, never a diff).
+type Reactions struct {
+	Id        string
+	Reactions []string
+}
+
 type MarkerType byte
 
 const (
@@ -61,6 +69,9 @@ const NSCommand string = "http://jabber.org/protocol/commands"
 // NSCaps is the XEP-0115 entity capabilities namespace
 const NSCaps string = "http://jabber.org/protocol/caps"
 
+// NSReactions is the XEP-0444 message reactions namespace
+const NSReactions string = "urn:xmpp:reactions:0"
+
 // CapsNode is this software's advertised XEP-0115 node URI
 const CapsNode string = "https://dev.narayana.im/narayana/telegabber/"
 
@@ -121,6 +132,12 @@ var HistoryBackfillLimit uint32 = 1000
 // waiting behind it. 0 (unset) means the default of 4.
 var HistoryBackfillWorkers uint32 = 4
 
+// MaxReactionsPerEmoji caps named reactors relayed per (message, emoji)
+// pair for group/channel reactions - anonymous ones are exempt, see
+// telegram.updateMessageInteractionInfo. 0 (unset) means the default of
+// 10; values above 100 are clamped (TDlib's own per-call ceiling).
+var MaxReactionsPerEmoji uint32 = 10
+
 // DownloadSpaceMargin is extra free-disk-space headroom, beyond a file's
 // own declared size, required before a TDlib download proceeds. Download
 // requests are already serialized system-wide via StorageLock, so this
@@ -262,6 +279,32 @@ func SendMessageMarker(to string, from string, component *xmpp.Component, marker
 	}))
 }
 
+// SendReactionMessage creates and sends a message stanza with a XEP-0444
+// reaction set (see Reactions); an empty reactionEmojis clears id's reactions.
+func SendReactionMessage(to string, from string, component *xmpp.Component, id string, reactionEmojis []string, isGroupchat bool) {
+	sendMessageWrapper(to, from, component, SMReactions(&Reactions{
+		Id:        id,
+		Reactions: reactionEmojis,
+	}), SMIsGroupchat(isGroupchat))
+}
+
+// SendMAMReactionMessage is SendReactionMessage wrapped as a XEP-0313 MAM
+// result: entryId is this result's own id (distinct from id, the
+// reacted-to message's own id); timestamp stands in for a historical
+// reaction timestamp, which doesn't exist (only a reaction's current
+// state, not when it was added).
+func SendMAMReactionMessage(to string, from string, component *xmpp.Component, id string, reactionEmojis []string, entryId string, timestamp int64, mucJID string, mamQueryId string) {
+	sendMessageWrapper(to, from, component,
+		SMReactions(&Reactions{Id: id, Reactions: reactionEmojis}),
+		SMId(entryId),
+		SMStanzaId(entryId),
+		SMTimestamp(timestamp),
+		SMMamQueryId(mamQueryId),
+		SMMucJID(mucJID),
+		SMIsGroupchat(true),
+	)
+}
+
 // SendMUCInvite creates and send a MUC invitation message
 func SendMUCInvite(to string, from string, component *xmpp.Component, inviteFrom string) {
 	sendMessageWrapper(to, from, component, SMInviteFrom(inviteFrom))
@@ -340,6 +383,9 @@ var SMMucUserItem = args.New()
 // XEP-0380 EME hint - see omemo.go's omemoStanzaExtension.
 var SMOMEMOEnvelope = args.New()
 
+// SMReactions is a XEP-0444 reaction set (*Reactions)
+var SMReactions = args.New()
+
 func sendMessageWrapper(to, from string, component *xmpp.Component, args ...args.V) {
 	body := SMBody.Get(args)
 	subject := SMSubject.Get(args)
@@ -363,6 +409,7 @@ func sendMessageWrapper(to, from string, component *xmpp.Component, args ...args
 	mucJID := SMMucJID.Get(args)
 	mucUserItem, _ := SMMucUserItem.Get(args).(*MUCUserItem)
 	envelope, _ := SMOMEMOEnvelope.Get(args).(*e2ee.Envelope)
+	reactions, _ := SMReactions.Get(args).(*Reactions)
 
 	toJid, err := stanza.NewJid(to)
 	if err != nil {
@@ -525,6 +572,18 @@ func sendMessageWrapper(to, from string, component *xmpp.Component, args ...args
 	if replaceId != "" {
 		message.Extensions = append(message.Extensions, extensions.Replace{Id: replaceId})
 	}
+	if reactions != nil {
+		reactionExts := make([]extensions.Reaction, len(reactions.Reactions))
+		for i, r := range reactions.Reactions {
+			reactionExts[i] = extensions.Reaction{Text: r}
+		}
+		message.Extensions = append(message.Extensions,
+			extensions.Reactions{Id: reactions.Id, Reactions: reactionExts},
+			// XEP-0334: body-less messages are commonly excluded from
+			// MAM by default archiving policies, so hint explicitly.
+			stanza.HintStore{},
+		)
+	}
 	var userExt extensions.MessageXMucUserExtension
 	if inviteFrom != "" {
 		userExt.Invite = &extensions.MessageXMucUserInvite{
@@ -1086,6 +1145,7 @@ func AddPMDiscoFeatures(disco *stanza.DiscoInfo) {
 	}
 	disco.AddFeatures(stanza.NSMsgChatMarkers)
 	disco.AddFeatures(stanza.NSMsgReceipts)
+	disco.AddFeatures(NSReactions)
 	// Jingle / JMI features so clients (e.g. Dino) treat the contact as
 	// call-capable. Without these, JMI <proceed> never fires: the client
 	// disco-info's the caller before engaging its call state machine and
@@ -1117,13 +1177,37 @@ func AddCommonDiscoFeatures(disco *stanza.DiscoInfo) {
 	)
 }
 
+// ReactionRestrictionsForm builds the XEP-0444 disco#info restricted-
+// reactions data form (urn:xmpp:reactions:0:restrictions). Shared by the
+// real disco#info response and PMCapsVer so they stay identical.
+func ReactionRestrictionsForm(allowlist []string, maxPerUser int) *stanza.Form {
+	return stanza.NewForm([]*stanza.Field{
+		&stanza.Field{
+			Var:        "FORM_TYPE",
+			Type:       "hidden",
+			ValuesList: []string{"urn:xmpp:reactions:0:restrictions"},
+		},
+		&stanza.Field{
+			Var:        "allowlist",
+			ValuesList: allowlist,
+		},
+		&stanza.Field{
+			Var:        "max_reactions_per_user",
+			ValuesList: []string{strconv.Itoa(maxPerUser)},
+		},
+	}, "result")
+}
+
 // PMCapsVer computes the XEP-0115 ver for a 1:1 contact's disco#info.
-// Not cached: if AddPMDiscoFeatures ever starts varying silently (no
+// forms must match that contact's live disco#info response's own Forms.
-// signature change), a cached ver would go stale with no compiler warning.
+// Not otherwise cached: if AddPMDiscoFeatures ever starts varying
-func PMCapsVer() string {
+// silently (no signature change), a cached ver would go stale with no
+// compiler warning.
+func PMCapsVer(forms ...*stanza.Form) string {
 	disco := &stanza.DiscoInfo{}
 	AddPMDiscoFeatures(disco)
 	AddCommonDiscoFeatures(disco)
+	disco.Forms = forms
 	return DiscoVer(disco)
 }
 
@@ -1158,11 +1242,21 @@ func discoToCaps(disco *stanza.DiscoInfo, w io.Writer) {
 		io.WriteString(w, sep)
 	}
 
-	if disco.Form == nil {
+	var forms []*stanza.Form
-		return
+	for _, f := range disco.Forms {
+		if f != nil {
+			forms = append(forms, f)
 		}
-	fields := make([]*stanza.Field, len(disco.Form.Fields))
+	}
-	copy(fields, disco.Form.Fields)
+	// XEP-0115 S5.1 step 6: with more than one extended form, sort by
+	// FORM_TYPE value before processing each in turn.
+	sort.Slice(forms, func(i, j int) bool {
+		return formType(forms[i]) < formType(forms[j])
+	})
+
+	for _, form := range forms {
+		fields := make([]*stanza.Field, len(form.Fields))
+		copy(fields, form.Fields)
 		sort.Slice(fields, func(i, j int) bool {
 			a, b := fields[i], fields[j]
 			if a.Var == "FORM_TYPE" {
@@ -1195,3 +1289,14 @@ func discoToCaps(disco *stanza.DiscoInfo, w io.Writer) {
 			}
 		}
 	}
+}
+
+// formType returns form's FORM_TYPE field value, or "" if it has none.
+func formType(form *stanza.Form) string {
+	for _, field := range form.Fields {
+		if field.Var == "FORM_TYPE" && len(field.ValuesList) > 0 {
+			return field.ValuesList[0]
+		}
+	}
+	return ""
+}

xmpp/handlers.go

@@ -216,7 +216,7 @@ func HandleMessage(s xmpp.Sender, p stanza.Packet) {
 		return
 	}
 
-	if msg.Type != "error" && (msg.Body != "" || hasOMEMOPayload(msg)) {
+	if msg.Type != "error" && (msg.Body != "" || hasOMEMOPayload(msg) || hasReactionsPayload(msg)) {
 		log.WithFields(log.Fields{
 			"from": msg.From,
 			"to":   msg.To,
@@ -273,14 +273,22 @@ func HandleMessage(s xmpp.Sender, p stanza.Packet) {
 			var fallback extensions.Fallback
 			var replace extensions.Replace
 			var attachTo extensions.AttachTo
+			var reactions extensions.Reactions
 			msg.Get(&reply)
 			msg.Get(&fallback)
 			msg.Get(&replace)
 			msg.Get(&attachTo)
+			msg.Get(&reactions)
 			log.Debugf("reply: %#v", reply)
 			log.Debugf("fallback: %#v", fallback)
 			log.Debugf("replace: %#v", replace)
 			log.Debugf("attachTo: %#v", attachTo)
+			log.Debugf("reactions: %#v", reactions)
+
+			if reactions.Id != "" {
+				handleIncomingReaction(component, msg, session, bare, toID, isGroupchat, reactions)
+				return
+			}
 
 			var replyId int64
 			text := msg.Body
@@ -1116,6 +1124,7 @@ func handleGetDiscoInfo(s xmpp.Sender, iq *stanza.IQ, di *stanza.DiscoInfo) {
 							"http://jabber.org/protocol/muc",
 							"muc_persistent",
 							"muc_hidden",
+							"muc_membersonly",
 							"muc_moderated",
 							"muc_nonanonymous",
 							"muc_unsecured",
@@ -1125,6 +1134,7 @@ func handleGetDiscoInfo(s xmpp.Sender, iq *stanza.IQ, di *stanza.DiscoInfo) {
 							gateway.NS_MAM1,
 							gateway.NS_MAM2,
 							"urn:xmpp:mam:2#extended",
+							gateway.NSReactions,
 							"urn:xmpp:sid:0",
 							"vcard-temp",
 						)
@@ -1155,7 +1165,11 @@ func handleGetDiscoInfo(s xmpp.Sender, iq *stanza.IQ, di *stanza.DiscoInfo) {
 							})
 						}
 
-						disco.Form = stanza.NewForm(fields, "result")
+						disco.Forms = append(disco.Forms, stanza.NewForm(fields, "result"))
+
+						if allowlist, maxPerUser, restrictOk := session.ReactionRestrictions(toID); restrictOk {
+							disco.Forms = append(disco.Forms, gateway.ReactionRestrictionsForm(allowlist, maxPerUser))
+						}
 					}
 				} else if !toOk {
 					disco.AddFeatures(
@@ -1175,6 +1189,13 @@ func handleGetDiscoInfo(s xmpp.Sender, iq *stanza.IQ, di *stanza.DiscoInfo) {
 				}
 			} else {
 				gateway.AddPMDiscoFeatures(disco)
+				if fromOk {
+					if session, sessionOk := sessions[bare]; sessionOk {
+						if allowlist, maxPerUser, restrictOk := session.ReactionRestrictions(toID); restrictOk {
+							disco.Forms = append(disco.Forms, gateway.ReactionRestrictionsForm(allowlist, maxPerUser))
+						}
+					}
+				}
 			}
 		} else {
 			gateway.AddTransportDiscoFeatures(disco)
@@ -2808,6 +2829,7 @@ func handleSetQueryMAM(s xmpp.Sender, iq *stanza.IQ, query extensions.MAMQuery)
 	queryId := ns + " " + query.GetQueryId()
 	for _, message := range messages {
 		session.SendDelayedMUCMessage(toID, message, iq.From, queryId)
+		session.SendDelayedMUCReactions(toID, message, iq.From, queryId)
 	}
 
 	rs := stanza.ResultSet{}

xmpp/reactions.go

@@ -0,0 +1,69 @@
+package xmpp
+
+import (
+	"strings"
+
+	log "github.com/sirupsen/logrus"
+	"gosrc.io/xmpp"
+	"gosrc.io/xmpp/stanza"
+
+	"dev.narayana.im/narayana/telegabber/telegram"
+	"dev.narayana.im/narayana/telegabber/xmpp/extensions"
+	"dev.narayana.im/narayana/telegabber/xmpp/gateway"
+)
+
+// hasReactionsPayload reports whether msg carries a XEP-0444 <reactions/>
+// element - such stanzas are body-less by design, so HandleMessage's
+// body-gate (there to skip typing notifications etc.) needs this alongside
+// hasOMEMOPayload to let them through.
+func hasReactionsPayload(msg stanza.Message) bool {
+	var reactions extensions.Reactions
+	return msg.Get(&reactions)
+}
+
+// handleIncomingReaction applies an incoming XEP-0444 <reactions/> stanza
+// to Telegram, rejecting it (S3.3, type='error'/not-acceptable) if any
+// requested emoji isn't allowed. bare and toID are already resolved by
+// HandleMessage's caller.
+func handleIncomingReaction(component *xmpp.Component, msg stanza.Message, session *telegram.Client, bare string, toID int64, isGroupchat bool, reactions extensions.Reactions) {
+	var msgId int64
+	chatId, foundMsgId, err := gateway.IdsDB.GetByXmppId(session.Session.Login, bare, reactions.Id)
+	if err == nil {
+		if chatId != toID {
+			log.Warnf("Reaction chat mismatch: %v != %v", chatId, toID)
+			return
+		}
+		msgId = foundMsgId
+	} else {
+		var ok bool
+		msgId, ok = parseMessageId(reactions.Id)
+		if !ok {
+			return
+		}
+	}
+
+	emojis := make([]string, 0, len(reactions.Reactions))
+	for _, r := range reactions.Reactions {
+		if r.Text != "" {
+			emojis = append(emojis, r.Text)
+		}
+	}
+
+	_, rejected := session.SetOwnMessageReactions(toID, msgId, emojis)
+	if len(rejected) == 0 {
+		return
+	}
+
+	var from string
+	if isGroupchat {
+		from = gateway.MUCJID(toID)
+	} else {
+		from = gateway.CHATNODE(toID)
+	}
+	gateway.SendMessage(msg.From, from, component,
+		gateway.SMErrorText("Reaction(s) not allowed: "+strings.Join(rejected, " ")),
+		gateway.SMErrorCode(406),
+		gateway.SMId(msg.Id),
+		gateway.SMIsGroupchat(isGroupchat),
+	)
+}