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, 70 insertions, 8 deletions

diff --git a/libs/basic_games/basic_game.py b/libs/basic_games/basic_game.py
index e0f7ba5..b3ff73d 100644
--- a/libs/basic_games/basic_game.py
+++ b/libs/basic_games/basic_game.py
@@ -1,11 +1,13 @@
 from __future__ import annotations
 
+import os
+import platform
 import shutil
 import sys
 from pathlib import Path
 from typing import Callable, Generic, TypeVar
 
-from PyQt6.QtCore import QDir, QFileInfo, QStandardPaths
+from PyQt6.QtCore import QDir, QFileInfo, QStandardPaths, qWarning
 from PyQt6.QtGui import QIcon
 from PyQt6.QtWidgets import QMessageBox
 
@@ -17,6 +19,49 @@ from .basic_features.basic_save_game_info import (
 )
 
 
+def _find_wine_userprofile() -> str | None:
+    """On Linux, find the Wine/Proton user profile directory inside the prefix.
+
+    Returns the host path equivalent of %USERPROFILE% (e.g.
+    ``<prefix>/drive_c/users/steamuser``) or *None* if no valid prefix is
+    found.
+    """
+    if platform.system() == "Windows":
+        return None
+
+    candidates: list[str] = []
+
+    # 1. Flatpak data prefix (most common for Fluorine)
+    flatpak_pfx = os.path.expanduser(
+        "~/.var/app/com.fluorine.manager/Prefix/pfx"
+    )
+    candidates.append(flatpak_pfx)
+
+    # 2. Fluorine config prefix_path
+    try:
+        config_dir = os.environ.get(
+            "XDG_CONFIG_HOME", os.path.join(str(Path.home()), ".config")
+        )
+        cfg_path = os.path.join(config_dir, "fluorine", "config.json")
+        if os.path.isfile(cfg_path):
+            import json
+
+            with open(cfg_path, "r") as f:
+                cfg = json.load(f)
+            pfx = cfg.get("prefix_path", "")
+            if pfx:
+                candidates.append(pfx)
+    except Exception:
+        pass
+
+    for pfx in candidates:
+        user_dir = os.path.join(pfx, "drive_c", "users", "steamuser")
+        if os.path.isdir(user_dir):
+            return user_dir
+
+    return None
+
+
 def replace_variables(value: str, game: BasicGame) -> str:
     """Replace special paths in the given value."""
 
@@ -28,12 +73,23 @@ def replace_variables(value: str, game: BasicGame) -> str:
             ),
         )
     if value.find("%USERPROFILE%") != -1:
-        value = value.replace(
-            "%USERPROFILE%",
-            QStandardPaths.writableLocation(
-                QStandardPaths.StandardLocation.HomeLocation
-            ),
-        )
+        if platform.system() != "Windows":
+            wine_profile = _find_wine_userprofile()
+            if wine_profile:
+                value = value.replace("%USERPROFILE%", wine_profile)
+            else:
+                qWarning(
+                    "No Wine/Proton prefix found. "
+                    "Ensure a prefix is configured in Settings > Proton."
+                )
+                value = value.replace("%USERPROFILE%", "")
+        else:
+            value = value.replace(
+                "%USERPROFILE%",
+                QStandardPaths.writableLocation(
+                    QStandardPaths.StandardLocation.HomeLocation
+                ),
+            )
     if value.find("%GAME_DOCUMENTS%") != -1:
         value = value.replace(
             "%GAME_DOCUMENTS%", game.documentsDirectory().absolutePath()
@@ -41,6 +97,9 @@ def replace_variables(value: str, game: BasicGame) -> str:
     if value.find("%GAME_PATH%") != -1:
         value = value.replace("%GAME_PATH%", game.gameDirectory().absolutePath())
 
+    # Normalize Windows backslash path separators for Linux.
+    value = value.replace("\\", "/")
+
     return value
 
 
@@ -634,8 +693,11 @@ class BasicGame(mobase.IPluginGame):
         return QDir(self._gamePath)
 
     def dataDirectory(self) -> QDir:
+        data_path = self._mappings.dataDirectory.get()
+        if data_path and QDir.isAbsolutePath(data_path):
+            return QDir(data_path)
         return QDir(
-            self.gameDirectory().absoluteFilePath(self._mappings.dataDirectory.get())
+            self.gameDirectory().absoluteFilePath(data_path)
         )
 
     def setGamePath(self, path: Path | str) -> None: