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>

2 files changed, 135 insertions, 0 deletions

diff --git a/libs/installer_fomod_plus/patchwizard/lib/PatchFinder.cpp b/libs/installer_fomod_plus/patchwizard/lib/PatchFinder.cpp
new file mode 100644
index 0000000..cd06b3a
--- /dev/null
+++ b/libs/installer_fomod_plus/patchwizard/lib/PatchFinder.cpp
@@ -0,0 +1,86 @@
+#include "PatchFinder.h"
+
+std::vector<AvailablePatch> PatchFinder::getAvailablePatchesForMod(const MOBase::IModInterface* mod)
+{
+    std::vector<AvailablePatch> available_patches = {};
+
+    // Verify that the mod has plugins in some shape or form.
+    if (const auto it = m_installedPlugins.find(mod); it == m_installedPlugins.end()) {
+        return available_patches;
+    }
+
+    // Look through the database
+    for (const auto& fomodDbEntries = mFomodDb->getEntries(); const auto& entry : fomodDbEntries) {
+        for (const auto& option : entry->getOptions()) {
+            // Skip options that are already selected/installed
+            if (option.selectionState == SelectionState::Selected) {
+                continue;
+            }
+
+            // Extract just the filename from the path (handle both / and \)
+            const auto fileName = option.fileName.substr(option.fileName.find_last_of("/\\") + 1);
+
+            // Skip if already installed in the modlist
+            if (m_installedPluginsCacheSet.contains(fileName)) {
+                continue;
+            }
+
+            // Technically without this check, we're doing a lookup for the entire modlist, which actually
+            // kinda works, but isn't the intention of this function. Might want to consider reworking
+            // it to map to mod names with one pass of the DB instead of a DB pass per mod.
+            if (!std::ranges::any_of(option.masters, [&mod](const std::string& master) {
+                return master == mod->name().toStdString();
+            })) {
+                continue;
+            }
+
+            // If we have all of this patch's masters in our modlist, and it's not installed, add it to the results.
+            if (std::ranges::all_of(option.masters, [this](const std::string& master) {
+                return m_installedPluginsCacheSet.contains(master);
+            })) {
+                AvailablePatch patch{
+                    option,
+                    entry->getDisplayName(),
+                    mod->name().toStdString(),
+                    false,  // not installed
+                    false,  // not hidden
+                    option.selectionState == SelectionState::Deselected  // userDeselected
+                };
+                available_patches.push_back(patch);
+            }
+        }
+    }
+
+    return available_patches;
+}
+
+std::vector<AvailablePatch> PatchFinder::getAvailablePatchesForModList()
+{
+    std::vector<AvailablePatch> available_patches = {};
+    for (const auto& modName : m_organizer->modList()->allMods()) {
+        const auto mod = m_organizer->modList()->getMod(modName);
+        if (mod == nullptr) {
+            continue;
+        }
+        for (const auto& available_patch : getAvailablePatchesForMod(mod)) {
+            available_patches.emplace_back(available_patch);
+        }
+    }
+
+    return available_patches;
+}
+
+void PatchFinder::populateInstalledPlugins()
+{
+    for (const auto& modName : m_organizer->modList()->allMods()) {
+        const auto mod      = m_organizer->modList()->getMod(modName);
+        const auto mod_tree = mod->fileTree();
+        for (auto it = mod_tree->begin(); it != mod_tree->end(); ++it) {
+            if ((*it)->isFile() && isPluginFile((*it)->name())) {
+                std::cout << "Plugin: " << (*it)->name().toStdString() << std::endl;
+                m_installedPlugins[mod].emplace_back((*it)->name().toStdString());
+                m_installedPluginsCacheSet.insert((*it)->name().toStdString());
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/libs/installer_fomod_plus/patchwizard/lib/PatchFinder.h b/libs/installer_fomod_plus/patchwizard/lib/PatchFinder.h
new file mode 100644
index 0000000..02327e3
--- /dev/null
+++ b/libs/installer_fomod_plus/patchwizard/lib/PatchFinder.h
@@ -0,0 +1,49 @@
+#pragma once
+
+#include "../../installer/lib/Logger.h"
+
+#include <FomodDB.h>
+#include <imodinterface.h>
+#include <imoinfo.h>
+#include <ifiletree.h>
+
+struct AvailablePatch {
+    FomodOption fomod_option;
+    std::string installer_name;
+    std::string patch_for_mod;
+    bool installed = false;
+    bool hidden    = false;
+    bool userDeselected = false;  // True if user explicitly chose not to install
+};
+
+class PatchFinder {
+friend class FomodPlusPatchWizard;
+
+public:
+    explicit PatchFinder(MOBase::IOrganizer* m_organizer) : m_organizer(m_organizer)
+    {
+        mFomodDb = std::make_unique<FomodDB>(m_organizer->basePath().toStdString());
+        logMessage(DEBUG, "mFomodDb loaded.");
+    }
+
+    std::vector<AvailablePatch> getAvailablePatchesForMod(const MOBase::IModInterface* mod);
+    std::vector<AvailablePatch> getAvailablePatchesForModList();
+
+protected:
+    void populateInstalledPlugins();
+
+private:
+    Logger& log = Logger::getInstance();
+    MOBase::IOrganizer* m_organizer;
+    std::unique_ptr<FomodDB> mFomodDb;
+
+    // Map of { pluginPtr: [1.esp, 2.esp, 3.esp] }
+    std::unordered_map<const MOBase::IModInterface*, std::vector<std::string> > m_installedPlugins;
+    std::unordered_set<std::string> m_installedPluginsCacheSet;
+
+    void logMessage(const LogLevel level, const std::string& message) const
+    {
+        log.logMessage(level, "[PATCHFINDER] " + message);
+    }
+
+};
\ No newline at end of file