Revise tag related implementations

Fix #12690.

src/base/orderedset.h

@@ -0,0 +1,108 @@
+/*
+ * Bittorrent Client using Qt and libtorrent.
+ * Copyright (C) 2021  Mike Tzou (Chocobo1)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ * In addition, as a special exception, the copyright holders give permission to
+ * link this program with the OpenSSL project's "OpenSSL" library (or with
+ * modified versions of it that use the same license as the "OpenSSL" library),
+ * and distribute the linked executables. You must obey the GNU General Public
+ * License in all respects for all of the code used other than "OpenSSL".  If you
+ * modify file(s), you may extend this exception to your version of the file(s),
+ * but you are not obligated to do so. If you do not wish to do so, delete this
+ * exception statement from your version.
+ */
+
+#pragma once
+
+#include <functional>
+#include <set>
+#include <type_traits>
+
+#include "algorithm.h"
+
+template <typename T, typename Compare = std::less<T>>
+class OrderedSet : public std::set<T, Compare>
+{
+    using ThisType = OrderedSet<T, Compare>;
+
+public:
+    using BaseType = std::set<T, Compare>;
+
+    using key_type = typename BaseType::key_type;
+    using value_type = typename BaseType::value_type;
+
+    using BaseType::BaseType;
+    using BaseType::operator=;
+
+    // The following are custom functions that are in line with Qt API interface, such as `QSet`
+
+#if __cplusplus < 202002L
+    bool contains(const key_type &value) const
+    {
+        return (BaseType::find(value) != BaseType::cend());
+    }
+#endif
+
+    int count() const
+    {
+        return static_cast<int>(BaseType::size());
+    }
+
+    ThisType &intersect(const ThisType &other)
+    {
+        Algorithm::removeIf(*this, [&other](const value_type &value) -> bool
+        {
+            return !other.contains(value);
+        });
+        return *this;
+    }
+
+    bool isEmpty() const
+    {
+        return BaseType::empty();
+    }
+
+    template <typename std::enable_if_t<std::is_same_v<value_type, QString>, int> = 0>
+    QString join(const QString &separator) const
+    {
+        auto iter = BaseType::cbegin();
+        if (iter == BaseType::cend())
+            return {};
+
+        QString ret = *iter;
+        ++iter;
+
+        while (iter != BaseType::cend())
+        {
+            ret.push_back(separator + *iter);
+            ++iter;
+        }
+
+        return ret;
+    }
+
+    bool remove(const key_type &value)
+    {
+        return (BaseType::erase(value) > 0);
+    }
+
+    ThisType &unite(const ThisType &other)
+    {
+        BaseType::insert(other.cbegin(), other.cend());
+        return *this;
+    }
+};