Fix handling of tags containing '&' character

PR #21024.
Closes #20773.

src/gui/utils.cpp

@@ -1,5 +1,6 @@
 /*
  * Bittorrent Client using Qt and libtorrent.
+ * Copyright (C) 2024  Vladimir Golovnev <glassez@yandex.ru>
  * Copyright (C) 2017  Mike Tzou
  *
  * This program is free software; you can redistribute it and/or
@@ -54,6 +55,7 @@
 
 #include "base/global.h"
 #include "base/path.h"
+#include "base/tag.h"
 #include "base/utils/fs.h"
 #include "base/utils/version.h"
 
@@ -216,3 +218,29 @@ void Utils::Gui::openFolderSelect(const Path &path)
     openPath(path.parentPath());
 #endif
 }
+
+QString Utils::Gui::tagToWidgetText(const Tag &tag)
+{
+    return tag.toString().replace(u'&', u"&&"_s);
+}
+
+Tag Utils::Gui::widgetTextToTag(const QString &text)
+{
+    // replace pairs of '&' with single '&' and remove non-paired occurrences of '&'
+    QString cleanedText;
+    cleanedText.reserve(text.size());
+    bool amp = false;
+    for (const QChar c : text)
+    {
+        if (c == u'&')
+        {
+            amp = !amp;
+            if (amp)
+                continue;
+        }
+
+        cleanedText.append(c);
+    }
+
+    return Tag(cleanedText);
+}