Add modl:// protocol support for mod.pub downloads

Handle modl:// links alongside nxm:// for downloading mods from
mod.pub. mod.pub uses a different URL format than Nexus — the download
URL is embedded as a query parameter: modl://game/?url=<encoded-url>

- Register x-scheme-handler/modl in desktop files and MIME lists
- Accept both nxm and modl schemes in URL parsing (NxmLink, NXMUrl)
- Parse modl:// direct download links and route to startDownloadURLs
- Make key/expires optional in NxmLink::parse (not used by mod.pub)
- Add debug logging for received URLs to aid troubleshooting

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

6 files changed, 46 insertions, 20 deletions

diff --git a/data/icons/com.fluorine.manager.desktop b/data/icons/com.fluorine.manager.desktop
index ff62c76..5d85cf8 100644
--- a/data/icons/com.fluorine.manager.desktop
+++ b/data/icons/com.fluorine.manager.desktop
@@ -8,7 +8,7 @@ Icon=com.fluorine.manager
 Terminal=false
 Categories=Game;Utility;
 Keywords=mod;organizer;modding;skyrim;fallout;
-MimeType=x-scheme-handler/nxm;
+MimeType=x-scheme-handler/nxm;x-scheme-handler/modl;
 Actions=create-portable;list-instances;
 
 [Desktop Action create-portable]
diff --git a/libs/uibase/src/nxmurl.cpp b/libs/uibase/src/nxmurl.cpp
index d09cdde..33bb22f 100644
--- a/libs/uibase/src/nxmurl.cpp
+++ b/libs/uibase/src/nxmurl.cpp
@@ -29,7 +29,7 @@ NXMUrl::NXMUrl(const QString& url)
 {
   QUrl nxm(url);
   QUrlQuery query(nxm);
-  QRegularExpression exp("nxm://[a-z0-9]+/mods/(\\d+)/files/(\\d+)",
+  QRegularExpression exp("(?:nxm|modl)://[a-z0-9]+/mods/(\\d+)/files/(\\d+)",
                          QRegularExpression::CaseInsensitiveOption);
   auto match = exp.match(url);
   if (!match.hasMatch()) {
diff --git a/src/src/main.cpp b/src/src/main.cpp
index b12ac7e..eed977e 100644
--- a/src/src/main.cpp
+++ b/src/src/main.cpp
@@ -205,6 +205,13 @@ int run(int argc, char* argv[])
                                    .arg(link.expires)

                                    .arg(link.user_id));

                          });

+

+        QObject::connect(&nxmHandler, &NxmHandlerLinux::directDownloadReceived,

+                         &app.core(), [&](const QString& url, const QString&) {

+                           QMetaObject::invokeMethod(&app.core(), [&app, url] {

+                             app.core().downloadManager()->startDownloadURLs(QStringList{url});

+                           }, Qt::QueuedConnection);

+                         });

       }

 #endif

 

diff --git a/src/src/nxmhandler_linux.cpp b/src/src/nxmhandler_linux.cpp
index fbf94d7..9441375 100644
--- a/src/src/nxmhandler_linux.cpp
+++ b/src/src/nxmhandler_linux.cpp
@@ -102,12 +102,15 @@ void updateMimeAppsList(const QString& path, const QString& mimeType,
 std::optional<NxmLink> NxmLink::parse(const QString& url)
 {
   const QUrl parsed(url);
-  if (!parsed.isValid() || parsed.scheme().compare("nxm", Qt::CaseInsensitive) != 0) {
+  const QString scheme = parsed.scheme().toLower();
+  if (!parsed.isValid() || (scheme != "nxm" && scheme != "modl")) {
+    log::debug("NxmLink::parse rejected scheme: '{}'", url);
     return {};
   }
 
   const QString gameDomain = parsed.host().trimmed();
   if (gameDomain.isEmpty()) {
+    log::debug("NxmLink::parse rejected empty host: '{}'", url);
     return {};
   }
 
@@ -115,6 +118,7 @@ std::optional<NxmLink> NxmLink::parse(const QString& url)
       parsed.path().split('/', Qt::SkipEmptyParts);
 
   if (parts.size() != 4 || parts[0] != "mods" || parts[2] != "files") {
+    log::debug("NxmLink::parse rejected path (expected /mods/ID/files/ID): '{}'", url);
     return {};
   }
 
@@ -123,22 +127,15 @@ std::optional<NxmLink> NxmLink::parse(const QString& url)
   const uint64_t modId  = parts[1].toULongLong(&modOk);
   const uint64_t fileId = parts[3].toULongLong(&fileOk);
   if (!modOk || !fileOk) {
+    log::debug("NxmLink::parse rejected non-numeric IDs: '{}'", url);
     return {};
   }
 
+  // key/expires are required for NXM but optional for modl:// (mod.pub).
   const QUrlQuery query(parsed);
-  const QString key = query.queryItemValue("key");
-  if (key.isEmpty()) {
-    return {};
-  }
-
-  bool expiresOk       = false;
-  const uint64_t expires = query.queryItemValue("expires").toULongLong(&expiresOk);
-  if (!expiresOk) {
-    return {};
-  }
-
-  const int userId = query.queryItemValue("user_id").toInt();
+  const QString key      = query.queryItemValue("key");
+  const uint64_t expires = query.queryItemValue("expires").toULongLong();
+  const int userId       = query.queryItemValue("user_id").toInt();
 
   return NxmLink{gameDomain, modId, fileId, key, expires, userId};
 }
@@ -229,7 +226,7 @@ void NxmHandlerLinux::registerHandler() const
                                   "Type=Application\n"
                                   "Name=Mod Organizer 2 NXM Handler\n"
                                   "Exec=%1\n"
-                                  "MimeType=x-scheme-handler/nxm;\n"
+                                  "MimeType=x-scheme-handler/nxm;x-scheme-handler/modl;\n"
                                   "NoDisplay=true\n").arg(execLine);
 
   if (!writeTextFile(desktopPath, desktop)) {
@@ -241,6 +238,10 @@ void NxmHandlerLinux::registerHandler() const
                      "mo2-nxm-handler.desktop");
   updateMimeAppsList(appsDir + "/mimeapps.list", "x-scheme-handler/nxm",
                      "mo2-nxm-handler.desktop");
+  updateMimeAppsList(configDir + "/mimeapps.list", "x-scheme-handler/modl",
+                     "mo2-nxm-handler.desktop");
+  updateMimeAppsList(appsDir + "/mimeapps.list", "x-scheme-handler/modl",
+                     "mo2-nxm-handler.desktop");
 
   const auto result =
       QProcess::execute("update-desktop-database", QStringList() << appsDir);
@@ -302,13 +303,29 @@ void NxmHandlerLinux::processSocketData(QLocalSocket* socket)
       continue;
     }
 
+    log::info("received link on socket: {}", line);
+
+    // Try NXM-style parse first (nxm:// or modl:// with /mods/ID/files/ID path).
     const auto link = NxmLink::parse(line);
-    if (!link) {
-      log::warn("received invalid nxm url on socket: {}", line);
+    if (link) {
+      emit nxmReceived(*link);
       continue;
     }
 
-    emit nxmReceived(*link);
+    // modl:// direct download: modl://GAME/?url=<encoded-download-url>
+    const QUrl parsed(line);
+    if (parsed.isValid() && parsed.scheme().compare("modl", Qt::CaseInsensitive) == 0) {
+      const QUrlQuery query(parsed);
+      const QString downloadUrl = query.queryItemValue("url", QUrl::FullyDecoded);
+      if (!downloadUrl.isEmpty()) {
+        const QString gameDomain = parsed.host().trimmed();
+        log::info("modl direct download for '{}': {}", gameDomain, downloadUrl);
+        emit directDownloadReceived(downloadUrl, gameDomain);
+        continue;
+      }
+    }
+
+    log::warn("received unrecognized url on socket: {}", line);
   }
 }
 
diff --git a/src/src/nxmhandler_linux.h b/src/src/nxmhandler_linux.h
index b6bd675..c4631aa 100644
--- a/src/src/nxmhandler_linux.h
+++ b/src/src/nxmhandler_linux.h
@@ -41,6 +41,7 @@ public:
 
 signals:
   void nxmReceived(NxmLink link);
+  void directDownloadReceived(QString url, QString gameDomain);
 
 private:
   void onNewConnection();
diff --git a/src/src/shared/util.cpp b/src/src/shared/util.cpp
index 2c982dc..70c0aeb 100644
--- a/src/src/shared/util.cpp
+++ b/src/src/shared/util.cpp
@@ -510,5 +510,6 @@ void ResetExitFlag()
 

 bool isNxmLink(const QString& link)

 {

-  return link.startsWith("nxm://", Qt::CaseInsensitive);

+  return link.startsWith("nxm://", Qt::CaseInsensitive) ||

+         link.startsWith("modl://", Qt::CaseInsensitive);

 }