Add FUSE external mapping support, BG3/Oblivion Remastered fixes, fomod-plus and NaK integration

FUSE VFS now deploys non-data-dir mod mappings (Paks, OBSE, UE4SS, etc.)
via real symlinks and injects file-level data-dir mappings (plugins.txt,
loadorder.txt) into the VFS tree. Fixes game launches for Oblivion
Remastered (Root Builder path resolution, script extender support) and
BG3 (Wine prefix documents directory, file mapper symlinks on Linux).

Vendors mo2-fomod-plus plugin and NaK crate for FOMOD installer and
game finder/runtime support.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 94 insertions, 0 deletions

diff --git a/libs/installer_fomod_plus/installer/lib/FileInstaller.h b/libs/installer_fomod_plus/installer/lib/FileInstaller.h
new file mode 100644
index 0000000..1c122a7
--- /dev/null
+++ b/libs/installer_fomod_plus/installer/lib/FileInstaller.h
@@ -0,0 +1,94 @@
+#pragma once
+
+#include <ifiletree.h>
+#include <nlohmann/json.hpp>
+
+#include "ConditionTester.h"
+#include "FlagMap.h"
+#include "Logger.h"
+#include "xml/ModuleConfiguration.h"
+
+
+/* This is what legacy fomodInstaller does:
+        modName.update(dialog.getName(), GUESS_USER);
+        return dialog.updateTree(tree);
+
+   This is a link to the legacy updateTree method:
+    https://github.com/ModOrganizer2/modorganizer-installer_fomod/blob/fc263f2d923c704b4853c11ed4f8b8cf3920f30d/src/fomodinstallerdialog.cpp#L546
+
+*/
+
+// Things this should do:
+// - Copy all requiredInstall files
+// - Copy all conditionalInstall files
+// - Copy all selected files from steps that were visible to the user at the point of install
+
+using namespace MOBase;
+
+using FileGlobalIndex = int;
+using FileDescriptor = std::pair<File, FileGlobalIndex>;
+
+class StepViewModel;
+
+class FileInstaller {
+public:
+    FileInstaller(
+        IOrganizer* organizer,
+        QString fomodPath,
+        const std::shared_ptr<IFileTree>& fileTree,
+        std::unique_ptr<ModuleConfiguration> fomodFile,
+        const std::shared_ptr<FlagMap>& flagMap,
+        const std::vector<std::shared_ptr<StepViewModel> >& steps);
+
+    std::shared_ptr<IFileTree> install() const;
+
+    /**
+     * @brief Create a 'fomod.json' file to add to the base of the installTree. Functionally similar to MO2's meta.ini.
+     *
+     * Until there's more utility in the JSON structure itself, it will simply be of this format:
+     * @code
+     * {
+     *  "steps": [
+     *    {
+     *      "name": "Step 1",
+     *      "groups": [
+     *        {
+     *          "name": "Group 1",
+     *          "plugins: [
+     *            "Plugin1.esp",
+     *            "Plugin2.esp"
+     *          ]
+     *        }
+     *      ]
+     *    }
+     *  ]
+     * }
+     * @endcode
+     *
+     * @return nhlohmann::json
+     */
+    nlohmann::json generateFomodJson() const;
+
+    std::string getQualifiedFilePath(const std::string& treePath) const;
+
+    std::vector<std::string> collectPositiveFileNamesFromDependencyPatterns(const std::vector<DependencyPattern> &patterns);
+
+    void addFiles(std::vector<File>& main, std::vector<File> toAdd) const;
+
+private:
+    IOrganizer* mOrganizer;
+    Logger& log = Logger::getInstance();
+    QString mFomodPath;
+    std::shared_ptr<IFileTree> mFileTree;
+    std::unique_ptr<ModuleConfiguration> mFomodFile;
+    std::shared_ptr<FlagMap> mFlagMap;
+    ConditionTester mConditionTester;
+    std::vector<std::shared_ptr<StepViewModel> > mSteps; // TODO: Maybe this is nasty. Idk.
+
+    std::vector<File> collectFilesToInstall() const;
+
+    void logMessage(LogLevel level, const std::string& message) const
+    {
+        log.logMessage(level, "[INSTALLER] " + message);
+    }
+};