merged with fixes

internal/store/message_pin.go

@@ -0,0 +1,31 @@
+package store
+
+import (
+	"crypto/rand"
+	"encoding/binary"
+	"fmt"
+
+	"telesrv/internal/domain"
+)
+
+// PrivatePinServiceRequest prepares the service receipt for a shared pin.
+// Pin state, checked under the store's pair lock, is the command's idempotency
+// boundary. A new receipt key allows unpin/repin even at the same timestamp.
+func PrivatePinServiceRequest(req domain.PinPrivateMessageRequest) (domain.SendPrivateTextRequest, error) {
+	var key [8]byte
+	var id int64
+	for id == 0 {
+		if _, err := rand.Read(key[:]); err != nil {
+			return domain.SendPrivateTextRequest{}, fmt.Errorf("pin service receipt key: %w", err)
+		}
+		id = int64(binary.LittleEndian.Uint64(key[:]))
+	}
+	return domain.SendPrivateTextRequest{
+		SenderUserID: req.OwnerUserID, RecipientUserID: req.Peer.ID, RandomID: id,
+		Media: &domain.MessageMedia{Kind: domain.MessageMediaKindService,
+			ServiceAction: &domain.MessageServiceAction{Kind: domain.MessageServiceActionPinMessage}},
+		ReplyTo: &domain.MessageReply{MessageID: req.MessageID, Peer: req.Peer},
+		Silent:  req.Silent, Date: req.Date, RecipientBlocked: req.RecipientBlocked,
+		OriginAuthKeyID: req.OriginAuthKeyID, OriginSessionID: req.OriginSessionID,
+	}, nil
+}