feat: Implement platform-specific persistence for renderer settings and save games

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

apps/wolf_3d_cli/lib/cli_renderer_settings_persistence.dart

@@ -12,9 +12,7 @@ import 'package:wolf_3d_dart/wolf_3d_engine.dart';
 class CliRendererSettingsPersistence extends RendererSettingsPersistence
     with JsonRendererSettingsPersistence {
   CliRendererSettingsPersistence({String? filePath})
-    : _filePath =
-          filePath ??
-          '${Platform.environment['HOME'] ?? '.'}/.wolf3d_cli_settings.json';
+    : _filePath = filePath ?? '${_platformConfigDir()}/settings.json';
 
   final String _filePath;
 
@@ -40,3 +38,21 @@ class CliRendererSettingsPersistence extends RendererSettingsPersistence
     }
   }
 }
+
+String _platformConfigDir() {
+  if (Platform.isLinux) {
+    final String xdg = Platform.environment['XDG_CONFIG_HOME'] ?? '';
+    final String home = Platform.environment['HOME'] ?? '.';
+    return xdg.isNotEmpty ? '$xdg/wolf3d' : '$home/.config/wolf3d';
+  }
+  if (Platform.isMacOS) {
+    final String home = Platform.environment['HOME'] ?? '.';
+    return '$home/Library/Application Support/wolf3d';
+  }
+  if (Platform.isWindows) {
+    final String appData = Platform.environment['APPDATA'] ?? '.';
+    return '$appData/wolf3d';
+  }
+  final String home = Platform.environment['HOME'] ?? '.';
+  return '$home/.config/wolf3d';
+}

apps/wolf_3d_cli/lib/cli_save_game_persistence.dart

@@ -12,9 +12,7 @@ import 'package:wolf_3d_dart/wolf_3d_engine.dart';
 /// `SAVEGAM{slot}.{ext}` where `{ext}` follows the active game version.
 class CliSaveGamePersistence implements SaveGamePersistence {
   CliSaveGamePersistence({String? directoryPath})
-    : _directoryPath =
-          directoryPath ??
-          '${Platform.environment['HOME'] ?? '.'}/.wolf3d_saves';
+    : _directoryPath = directoryPath ?? '${_platformConfigDir()}/saves';
 
   final String _directoryPath;
 
@@ -66,3 +64,21 @@ class CliSaveGamePersistence implements SaveGamePersistence {
     return '$_directoryPath/SAVEGAM$normalizedSlot.${version.fileExtension}';
   }
 }
+
+String _platformConfigDir() {
+  if (Platform.isLinux) {
+    final String xdg = Platform.environment['XDG_CONFIG_HOME'] ?? '';
+    final String home = Platform.environment['HOME'] ?? '.';
+    return xdg.isNotEmpty ? '$xdg/wolf3d' : '$home/.config/wolf3d';
+  }
+  if (Platform.isMacOS) {
+    final String home = Platform.environment['HOME'] ?? '.';
+    return '$home/Library/Application Support/wolf3d';
+  }
+  if (Platform.isWindows) {
+    final String appData = Platform.environment['APPDATA'] ?? '.';
+    return '$appData/wolf3d';
+  }
+  final String home = Platform.environment['HOME'] ?? '.';
+  return '$home/.config/wolf3d';
+}