Improve Search handling

Legacy SearchEngine class really has three roles:
  1. Manage search plugins,
  2. Handle the search job, and
  3. Handle the download of the torrent file using the search plugin.
Now it is splitted into 3 classes: SearchManager, SearchHandler and
SearchDownloadHandler.
Search GUI is also improved.

src/base/search/searchpluginmanager.h

@@ -0,0 +1,115 @@
+/*
+ * Bittorrent Client using Qt and libtorrent.
+ * Copyright (C) 2015, 2018  Vladimir Golovnev <glassez@yandex.ru>
+ * Copyright (C) 2006  Christophe Dumez <chris@qbittorrent.org>
+ *
+ * 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 <QHash>
+#include <QMetaType>
+#include <QObject>
+
+#include "base/utils/version.h"
+
+using PluginVersion = Utils::Version<unsigned short, 2>;
+Q_DECLARE_METATYPE(PluginVersion)
+
+struct PluginInfo
+{
+    QString name;
+    PluginVersion version;
+    QString fullName;
+    QString url;
+    QStringList supportedCategories;
+    QString iconPath;
+    bool enabled;
+};
+
+class SearchDownloadHandler;
+class SearchHandler;
+
+class SearchPluginManager : public QObject
+{
+    Q_OBJECT
+    Q_DISABLE_COPY(SearchPluginManager)
+
+public:
+    SearchPluginManager();
+    ~SearchPluginManager() override;
+
+    QStringList allPlugins() const;
+    QStringList enabledPlugins() const;
+    QStringList supportedCategories() const;
+    PluginInfo *pluginInfo(const QString &name) const;
+
+    void enablePlugin(const QString &name, bool enabled = true);
+    void updatePlugin(const QString &name);
+    void installPlugin(const QString &source);
+    bool uninstallPlugin(const QString &name);
+    static void updateIconPath(PluginInfo * const plugin);
+    void checkForUpdates();
+
+    SearchHandler *startSearch(const QString &pattern, const QString &category, const QStringList &usedPlugins);
+    SearchDownloadHandler *downloadTorrent(const QString &siteUrl, const QString &url);
+
+    static PluginVersion getPluginVersion(QString filePath);
+    static QString categoryFullName(const QString &categoryName);
+    QString pluginFullName(const QString &pluginName);
+    static QString pluginsLocation();
+    static QString engineLocation();
+
+signals:
+    void pluginEnabled(const QString &name, bool enabled);
+    void pluginInstalled(const QString &name);
+    void pluginInstallationFailed(const QString &name, const QString &reason);
+    void pluginUninstalled(const QString &name);
+    void pluginUpdated(const QString &name);
+    void pluginUpdateFailed(const QString &name, const QString &reason);
+
+    void checkForUpdatesFinished(const QHash<QString, PluginVersion> &updateInfo);
+    void checkForUpdatesFailed(const QString &reason);
+
+private:
+    void update();
+    void updateNova();
+    void parseVersionInfo(const QByteArray &info);
+    void installPlugin_impl(const QString &name, const QString &path);
+    bool isUpdateNeeded(QString pluginName, PluginVersion newVersion) const;
+
+    void versionInfoDownloaded(const QString &url, const QByteArray &data);
+    void versionInfoDownloadFailed(const QString &url, const QString &reason);
+    void pluginDownloaded(const QString &url, QString filePath);
+    void pluginDownloadFailed(const QString &url, const QString &reason);
+
+    static QString pluginPath(const QString &name);
+
+    static const QHash<QString, QString> m_categoryNames;
+
+    const QString m_updateUrl;
+
+    QHash<QString, PluginInfo*> m_plugins;
+};