feat: sync ephemeral transient messages

Sync telesrv 570ccf8 (feat(ephemeral): implement Layer 228 transient messages).

Skipped telesrv docs changes per public sync rules; normalized the public appearance seed label.

internal/domain/botapi_update.go

@@ -1,5 +1,7 @@
 package domain
 
+import "time"
+
 // BotAPIUpdateKind is the Bot API delivery shape for a queued update.
 type BotAPIUpdateKind string
 
@@ -22,6 +24,109 @@ type BotCallbackQuery struct {
 	InlineMessage *BotInlineMessageID
 }
 
+// BotAPIEphemeralPayload is a self-contained 24-hour Bot API queue snapshot.
+// Ordinary queued messages are reloaded from their durable message tables;
+// ephemeral messages have no such table and therefore travel in this explicit
+// envelope instead of overloading SourcePts or an ordinary message id. The
+// public shape deliberately cannot represent random IDs, payload hashes,
+// auth-key/session identifiers, or the originating device.
+type BotAPIEphemeralPayload struct {
+	Message BotAPIEphemeralMessage
+	ReplyTo *BotAPIEphemeralMessage `json:",omitempty"`
+}
+
+type BotAPIEphemeralMessage struct {
+	ID                 int
+	Peer               Peer
+	SenderUserID       int64
+	ReceiverUserID     int64
+	Date               int
+	EditDate           int
+	TopMessageID       int
+	ReplyToEphemeralID int
+	Content            EphemeralContent
+	Version            uint64
+	ExpiresAt          time.Time
+}
+
+func NewBotAPIEphemeralPayload(message EphemeralMessage) *BotAPIEphemeralPayload {
+	payload := &BotAPIEphemeralPayload{Message: publicBotAPIEphemeralMessage(message)}
+	if message.BotAPIReply != nil {
+		reply := publicBotAPIEphemeralMessage(*message.BotAPIReply)
+		payload.ReplyTo = &reply
+	}
+	return payload
+}
+
+func publicBotAPIEphemeralMessage(message EphemeralMessage) BotAPIEphemeralMessage {
+	return BotAPIEphemeralMessage{
+		ID: message.ID, Peer: message.Peer,
+		SenderUserID: message.SenderUserID, ReceiverUserID: message.ReceiverUserID,
+		Date: message.Date, EditDate: message.EditDate,
+		TopMessageID: message.TopMessageID, ReplyToEphemeralID: message.ReplyToEphemeralID,
+		Content: message.Content, Version: message.Version, ExpiresAt: message.ExpiresAt,
+	}
+}
+
+func (m BotAPIEphemeralMessage) EphemeralMessage() EphemeralMessage {
+	return EphemeralMessage{
+		ID: m.ID, Peer: m.Peer,
+		SenderUserID: m.SenderUserID, ReceiverUserID: m.ReceiverUserID,
+		Date: m.Date, EditDate: m.EditDate,
+		TopMessageID: m.TopMessageID, ReplyToEphemeralID: m.ReplyToEphemeralID,
+		Content: m.Content, Version: m.Version, ExpiresAt: m.ExpiresAt,
+	}
+}
+
+func (p BotAPIEphemeralPayload) EphemeralMessage() EphemeralMessage {
+	message := p.Message.EphemeralMessage()
+	if p.ReplyTo != nil {
+		reply := p.ReplyTo.EphemeralMessage()
+		message.BotAPIReply = &reply
+	}
+	return message
+}
+
+func (p BotAPIEphemeralPayload) Validate() error {
+	if err := p.Message.Validate(); err != nil {
+		return err
+	}
+	if p.Message.ReplyToEphemeralID == 0 {
+		if p.ReplyTo != nil {
+			return ErrEphemeralInvalid
+		}
+		return nil
+	}
+	if p.ReplyTo == nil || p.ReplyTo.Validate() != nil || p.ReplyTo.ID != p.Message.ReplyToEphemeralID ||
+		p.ReplyTo.Peer != p.Message.Peer || p.ReplyTo.Date > p.Message.Date ||
+		!sameEphemeralParticipantPair(p.Message.SenderUserID, p.Message.ReceiverUserID, p.ReplyTo.SenderUserID, p.ReplyTo.ReceiverUserID) {
+		return ErrEphemeralInvalid
+	}
+	return nil
+}
+
+func sameEphemeralParticipantPair(firstSender, firstReceiver, secondSender, secondReceiver int64) bool {
+	return (firstSender == secondSender && firstReceiver == secondReceiver) ||
+		(firstSender == secondReceiver && firstReceiver == secondSender)
+}
+
+func (m BotAPIEphemeralMessage) Expired(now time.Time) bool {
+	return !m.ExpiresAt.IsZero() && !now.Before(m.ExpiresAt)
+}
+
+func (m BotAPIEphemeralMessage) Validate() error {
+	date := time.Unix(int64(m.Date), 0)
+	if m.ID <= 0 || m.ID > MaxMessageBoxID || m.Peer.Type != PeerTypeChannel || m.Peer.ID <= 0 ||
+		m.SenderUserID <= 0 || m.ReceiverUserID <= 0 || m.SenderUserID == m.ReceiverUserID ||
+		m.Date <= 0 || m.Version == 0 || m.ExpiresAt.IsZero() || !m.ExpiresAt.After(date) ||
+		m.ExpiresAt.Sub(date) > EphemeralMessageRetention+time.Second ||
+		(m.EditDate != 0 && m.EditDate < m.Date) || m.TopMessageID < 0 || m.TopMessageID > MaxMessageBoxID ||
+		m.ReplyToEphemeralID < 0 || m.ReplyToEphemeralID > MaxMessageBoxID || m.ReplyToEphemeralID == m.ID {
+		return ErrEphemeralInvalid
+	}
+	return ValidateEphemeralContent(m.Content)
+}
+
 // BotInlineMessageID is the domain-only shape of inputBotInlineMessageID64.
 // It can be projected both to MTProto and to Bot API's opaque
 // inline_message_id without leaking tg types into the store boundary.
@@ -44,6 +149,7 @@ type BotAPIUpdate struct {
 	SourcePts int
 	Date      int
 	Callback  *BotCallbackQuery
+	Ephemeral *BotAPIEphemeralPayload
 }
 
 // EnqueueBotAPIUpdateRequest describes a message-like update that should be
@@ -56,4 +162,5 @@ type EnqueueBotAPIUpdateRequest struct {
 	SourcePts int
 	Date      int
 	Callback  *BotCallbackQuery
+	Ephemeral *BotAPIEphemeralPayload
 }