Trim desktop message link punctuation in linear time

tools/chatgui/src/message_links.cpp

@@ -12,13 +12,24 @@ QVector<MessageLink> messageLinks(const QString& text) {
         const auto match = matches.next();
         QString url = match.captured();
         if (!url.startsWith(QStringLiteral("utun://"))) {
-            while (!url.isEmpty()) {
-                const QChar last = url.back();
-                const int closing = QStringLiteral(")]}").indexOf(last);
-                const bool unmatched = closing >= 0 && url.count(last) > url.count(QStringLiteral("([{").at(closing));
-                if (!QStringLiteral(".,;:!?").contains(last) && !unmatched) break;
-                url.chop(1);
+            // Один подсчёт и один проход по хвосту: повторный count() на каждой скобке даёт O(n²).
+            qsizetype balance[3] = {};
+            for (const QChar ch : url) {
+                const int opening = QStringLiteral("([{").indexOf(ch);
+                const int closing = QStringLiteral(")]}").indexOf(ch);
+                if (opening >= 0) balance[opening]--;
+                if (closing >= 0) balance[closing]++;
             }
+            auto end = url.size();
+            while (end > 0) {
+                const QChar last = url.at(end - 1);
+                const int closing = QStringLiteral(")]}").indexOf(last);
+                const bool unmatched = closing >= 0 && balance[closing] > 0;
+                if (!QStringLiteral(".,;:!?").contains(last) && !unmatched) break;
+                if (closing >= 0) balance[closing]--;
+                end--;
+            }
+            url.truncate(end);
             const QUrl parsed(url, QUrl::StrictMode);
             if (!parsed.isValid() || parsed.host().isEmpty()) continue;
         }