Fix conversation context topic fallback

server/im_http.go

@@ -4088,7 +4088,11 @@ func serveIMConversationContext(wrt http.ResponseWriter, req *http.Request) {
 		writeIMError(wrt, req, http.StatusMethodNotAllowed, 30002, imReasonMethodNotAllowed, "method not allowed", nil)
 		return
 	}
-	topic, peer := normalizeP2PConversationTopic(topic, principal.Uid)
+	topic, peer, err := resolveConversationContextTopic(principal, topic)
+	if err != nil {
+		writeIMRelationError(wrt, req, err)
+		return
+	}
 	if topic == "" || peer.IsZero() {
 		writeIMError(wrt, req, http.StatusBadRequest, 30000, imReasonMalformedRequest, "malformed request", map[string]any{"field": "topic"})
 		return
@@ -9996,6 +10000,37 @@ func normalizeP2PConversationTopic(topic string, uid types.Uid) (string, types.U
 	return topic, peer
 }
 
+func resolveConversationContextTopic(principal *imPrincipal, topic string) (string, types.Uid, error) {
+	normalized, peer := normalizeP2PConversationTopic(topic, principal.Uid)
+	if normalized != "" && !peer.IsZero() {
+		return normalized, peer, nil
+	}
+	topic = strings.TrimSpace(topic)
+	if types.GetTopicCat(topic) != types.TopicCatP2P {
+		return "", types.ZeroUid, nil
+	}
+	if _, _, err := types.ParseP2P(topic); err != nil {
+		return "", types.ZeroUid, nil
+	}
+	cursor := ""
+	for {
+		items, nextCursor, err := store.Relations.ListFriends(principal.TenantID, principal.Uid, "", "", cursor, 100)
+		if err != nil {
+			return "", types.ZeroUid, err
+		}
+		for _, item := range items {
+			if strings.TrimSpace(item.Friendship.Topic) == topic && !item.Friendship.PeerID.IsZero() {
+				return topic, item.Friendship.PeerID, nil
+			}
+		}
+		if nextCursor == "" {
+			break
+		}
+		cursor = nextCursor
+	}
+	return "", types.ZeroUid, nil
+}
+
 func normalizeConversationSettingsTopic(topic string, uid types.Uid) string {
 	if normalized, peer := normalizeP2PConversationTopic(topic, uid); !peer.IsZero() {
 		return normalized