tell user they might downgrade in update popup

src/singletons/Updates.cpp

@@ -13,6 +13,7 @@
 #include <QDesktopServices>
 #include <QMessageBox>
 #include <QProcess>
+#include <QRegularExpression>
 
 namespace chatterino {
 namespace {
@@ -20,6 +21,38 @@ namespace {
     {
         return getSettings()->betaUpdates ? "beta" : "stable";
     }
+
+    /// Checks if the online version is newer or older than the current version.
+    bool isDowngradeOf(const QString &online, const QString &current)
+    {
+        static auto matchVersion =
+            QRegularExpression(R"((\d+)(?:\.(\d+))?(?:\.(\d+))?(?:\.(\d+))?)");
+
+        // Versions are just strings, they don't need to follow a specific
+        // format so we can only assume if one version is newer than another
+        // one.
+
+        // We match x.x.x.x with each version level being optional.
+
+        auto onlineMatch = matchVersion.match(online);
+        auto currentMatch = matchVersion.match(current);
+
+        for (int i = 1; i <= 4; i++)
+        {
+            if (onlineMatch.captured(i).toInt() <
+                currentMatch.captured(i).toInt())
+            {
+                return true;
+            }
+            if (onlineMatch.captured(i).toInt() >
+                currentMatch.captured(i).toInt())
+            {
+                break;
+            }
+        }
+
+        return false;
+    }
 }  // namespace
 
 Updates::Updates()
@@ -263,6 +296,8 @@ void Updates::checkForUpdates()
             if (this->currentVersion_ != this->onlineVersion_)
             {
                 this->setStatus_(UpdateAvailable);
+                this->isDowngrade_ =
+                    isDowngradeOf(this->onlineVersion_, this->currentVersion_);
             }
             else
             {
@@ -309,6 +344,11 @@ bool Updates::isError() const
     }
 }
 
+bool Updates::isDowngrade() const
+{
+    return this->isDowngrade_;
+}
+
 void Updates::setStatus_(Status status)
 {
     if (this->status_ != status)

src/singletons/Updates.hpp

@@ -32,6 +32,7 @@ public:
 
     bool shouldShowUpdateButton() const;
     bool isError() const;
+    bool isDowngrade() const;
 
     pajlada::Signals::Signal<Status> statusUpdated;
 
@@ -39,6 +40,7 @@ private:
     QString currentVersion_;
     QString onlineVersion_;
     Status status_ = None;
+    bool isDowngrade_{};
 
     QString updateExe_;
     QString updatePortable_;

src/widgets/dialogs/UpdateDialog.cpp

@@ -50,9 +50,17 @@ void UpdateDialog::updateStatusChanged(Updates::Status status)
     {
         case Updates::UpdateAvailable: {
             this->ui_.label->setText(
-                QString("An update (%1) is available.\n\nDo you want to "
+                (Updates::getInstance().isDowngrade()
-                        "download and install it?")
+                     ? QString(
-                    .arg(Updates::getInstance().getOnlineVersion()));
+                           "The version online (%1) seems to be lower than the "
+                           "current (%2).\nEither a version was reverted or "
+                           "you are running a newer build.\n\nDo you want to "
+                           "download and install it?")
+                           .arg(Updates::getInstance().getOnlineVersion(),
+                                Updates::getInstance().getCurrentVersion())
+                     : QString("An update (%1) is available.\n\nDo you want to "
+                               "download and install it?")
+                           .arg(Updates::getInstance().getOnlineVersion())));
             this->updateGeometry();
         }
         break;