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, 129 insertions, 0 deletions

diff --git a/libs/installer_fomod_plus/share/FOMODData/FomodDBEntry.h b/libs/installer_fomod_plus/share/FOMODData/FomodDBEntry.h
new file mode 100644
index 0000000..5d39f95
--- /dev/null
+++ b/libs/installer_fomod_plus/share/FOMODData/FomodDBEntry.h
@@ -0,0 +1,129 @@
+#pragma once
+
+#include <string>
+#include <utility>
+#include <vector>
+#include <nlohmann/json.hpp>
+
+/*
+The following JSON will be part of an array of similar objects in the root level "JSON DB" for FOMOD Plus.
+It contains information to resolve the identity of a given mod (names can change), and then the options
+in the FOMOD with their respective masters.
+{
+    modId: 12345,
+    displayName: "Lux (Patch Hub)",
+    options: [
+        {
+            "name" "JK's The Hag's Cure",
+            "fileName": "Lux - JK's The Hag's Cure patch.esp",
+            "masters": [
+                "Skyrim.esm",
+                "JK's The Hag's Cure.esp",
+                "Lux - Resources.esp",
+                "Lux.esp"
+            ],
+            "step": "Page One",
+            "group": "Group One",
+            "selectionState": "Available"
+        }
+    ]
+}
+*/
+
+enum class SelectionState {
+  Unknown,     // Not yet matched to choices
+  Selected,    // User selected this option
+  Deselected,  // User manually deselected
+  Available    // Present but user didn't interact (or choices not recorded)
+};
+
+inline std::string selectionStateToString(SelectionState state) {
+  switch (state) {
+    case SelectionState::Unknown: return "Unknown";
+    case SelectionState::Selected: return "Selected";
+    case SelectionState::Deselected: return "Deselected";
+    case SelectionState::Available: return "Available";
+    default: return "Unknown";
+  }
+}
+
+inline SelectionState stringToSelectionState(const std::string& str) {
+  if (str == "Selected") return SelectionState::Selected;
+  if (str == "Deselected") return SelectionState::Deselected;
+  if (str == "Available") return SelectionState::Available;
+  return SelectionState::Unknown;
+}
+
+struct FomodOption {
+  std::string name;
+  std::string fileName;
+  std::vector<std::string> masters;
+  std::string step;
+  std::string group;
+  SelectionState selectionState = SelectionState::Unknown;
+
+  FomodOption(std::string n, std::string fn, std::vector<std::string> m, std::string s, std::string g,
+              SelectionState state = SelectionState::Unknown)
+  : name(std::move(n)), fileName(std::move(fn)), masters(std::move(m)), step(std::move(s)), group(std::move(g)),
+    selectionState(state) {}
+};
+
+class FomodDbEntry {
+public:
+  explicit FomodDbEntry(nlohmann::json json) {
+    modId = json["modId"];
+    displayName = json["displayName"];
+    for (auto &option: json["options"]) {
+      // create an option from this object
+      SelectionState state = SelectionState::Unknown;
+      if (option.contains("selectionState")) {
+        state = stringToSelectionState(option["selectionState"]);
+      }
+      FomodOption fomodOption(
+        option["name"],
+        option["fileName"],
+        option["masters"],
+        option["step"],
+        option["group"],
+        state
+      );
+      options.push_back(fomodOption);
+    }
+  }
+
+  explicit FomodDbEntry(const int modId, std::string displayName, const std::vector<FomodOption> &options)
+    : modId(modId), displayName(std::move(displayName)), options(options) {
+  }
+
+
+  [[nodiscard]] int getModId() const { return modId; }
+  [[nodiscard]] std::string getDisplayName() const { return displayName; }
+  [[nodiscard]] const std::vector<FomodOption>& getOptions() const { return options; }
+  [[nodiscard]] std::vector<FomodOption>& getOptionsMutable() { return options; }
+
+  [[nodiscard]] nlohmann::json toJson() const {
+    nlohmann::json result;
+    result["modId"] = modId;
+    result["displayName"] = displayName;
+
+    nlohmann::json optionsArray = nlohmann::json::array();
+    for (const auto &[name, fileName, masters, step, group, selectionState]: options) {
+      nlohmann::json optionJson;
+      optionJson["name"] = name;
+      optionJson["fileName"] = fileName;
+      optionJson["masters"] = masters;
+      optionJson["step"] = step;
+      optionJson["group"] = group;
+      optionJson["selectionState"] = selectionStateToString(selectionState);
+      optionsArray.push_back(optionJson);
+    }
+
+    result["options"] = optionsArray;
+    return result;
+  }
+
+private:
+  int modId;
+  std::string displayName;
+  std::vector<FomodOption> options;
+};