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

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

packages/wolf_3d_dart/lib/src/engine/rendering/default_renderer_settings_persistence.dart

@@ -0,0 +1,5 @@
+/// Routes to the native or stub implementation based on platform.
+library;
+
+export 'default_renderer_settings_persistence_stub.dart'
+    if (dart.library.io) 'default_renderer_settings_persistence_io.dart';

packages/wolf_3d_dart/lib/src/engine/rendering/default_renderer_settings_persistence_io.dart

@@ -0,0 +1,49 @@
+/// Native (dart:io) renderer-settings persistence.
+library;
+
+import 'dart:io';
+
+import 'package:wolf_3d_dart/src/engine/rendering/renderer_settings.dart';
+import 'package:wolf_3d_dart/src/engine/rendering/renderer_settings_persistence.dart';
+import 'package:wolf_3d_dart/src/platform/platform_config_dir.dart';
+
+/// Persists [WolfRendererSettings] as JSON to the platform config directory.
+///
+/// Pass an explicit [filePath] to override the default location (useful in tests).
+class DefaultRendererSettingsPersistence extends RendererSettingsPersistence
+    with JsonRendererSettingsPersistence {
+  DefaultRendererSettingsPersistence({String? filePath}) : _filePath = filePath;
+
+  final String? _filePath;
+  String? _resolvedPath;
+
+  Future<String> _getFilePath() async {
+    if (_resolvedPath != null) return _resolvedPath!;
+    _resolvedPath = _filePath ?? '${platformConfigDir()}/settings.json';
+    return _resolvedPath!;
+  }
+
+  @override
+  Future<String?> readRaw() async {
+    try {
+      final String path = await _getFilePath();
+      final File f = File(path);
+      if (!f.existsSync()) return null;
+      return await f.readAsString();
+    } catch (_) {
+      return null;
+    }
+  }
+
+  @override
+  Future<void> writeRaw(String json) async {
+    try {
+      final String path = await _getFilePath();
+      final Directory dir = File(path).parent;
+      if (!dir.existsSync()) await dir.create(recursive: true);
+      await File(path).writeAsString(json, flush: true);
+    } catch (_) {
+      // Best-effort.
+    }
+  }
+}

packages/wolf_3d_dart/lib/src/engine/rendering/default_renderer_settings_persistence_stub.dart

@@ -0,0 +1,17 @@
+/// Web stub for renderer-settings persistence: silently skips all I/O.
+library;
+
+import 'package:wolf_3d_dart/src/engine/rendering/renderer_settings.dart';
+import 'package:wolf_3d_dart/src/engine/rendering/renderer_settings_persistence.dart';
+
+/// No-op implementation used on web, where dart:io is unavailable.
+class DefaultRendererSettingsPersistence extends RendererSettingsPersistence {
+  // ignore: avoid_unused_constructor_parameters
+  DefaultRendererSettingsPersistence({String? filePath});
+
+  @override
+  Future<WolfRendererSettings?> load() async => null;
+
+  @override
+  Future<void> save(WolfRendererSettings settings) async {}
+}

packages/wolf_3d_dart/lib/src/engine/save/default_save_game_persistence.dart

@@ -0,0 +1,5 @@
+/// Routes to the native or stub implementation based on platform.
+library;
+
+export 'default_save_game_persistence_stub.dart'
+    if (dart.library.io) 'default_save_game_persistence_io.dart';

packages/wolf_3d_dart/lib/src/engine/save/default_save_game_persistence_io.dart

@@ -0,0 +1,65 @@
+/// Native (dart:io) slot-based save-game persistence.
+library;
+
+import 'dart:io';
+import 'dart:typed_data';
+
+import 'package:wolf_3d_dart/src/engine/save/save_game_persistence.dart';
+import 'package:wolf_3d_dart/src/platform/platform_config_dir.dart';
+import 'package:wolf_3d_dart/wolf_3d_data_types.dart';
+
+/// Persists save-game slots as raw bytes under the platform config directory.
+///
+/// Files are stored in `<configDir>/saves/` and named
+/// `SAVEGAM{slot}.{ext}` where `{ext}` follows the active game version.
+///
+/// Pass an explicit [directoryPath] to override the default (useful in tests).
+class DefaultSaveGamePersistence extends SaveGamePersistence {
+  DefaultSaveGamePersistence({String? directoryPath})
+    : _directoryPath = directoryPath ?? '${platformConfigDir()}/saves';
+
+  final String _directoryPath;
+
+  @override
+  Future<Uint8List?> load({
+    required int slot,
+    required GameVersion version,
+  }) async {
+    try {
+      final File file = File(_slotPath(slot, version));
+      if (!file.existsSync()) return null;
+      return await file.readAsBytes();
+    } catch (_) {
+      return null;
+    }
+  }
+
+  @override
+  Future<bool> exists({
+    required int slot,
+    required GameVersion version,
+  }) async {
+    try {
+      final File file = File(_slotPath(slot, version));
+      return file.existsSync() && file.lengthSync() > 0;
+    } catch (_) {
+      return false;
+    }
+  }
+
+  @override
+  Future<void> save({
+    required int slot,
+    required GameVersion version,
+    required Uint8List bytes,
+  }) async {
+    final Directory dir = Directory(_directoryPath);
+    if (!dir.existsSync()) await dir.create(recursive: true);
+    await File(_slotPath(slot, version)).writeAsBytes(bytes, flush: true);
+  }
+
+  String _slotPath(int slot, GameVersion version) {
+    final String normalizedSlot = slot.clamp(0, 9).toString();
+    return '$_directoryPath/SAVEGAM$normalizedSlot.${version.fileExtension}';
+  }
+}

packages/wolf_3d_dart/lib/src/engine/save/default_save_game_persistence_stub.dart

@@ -0,0 +1,32 @@
+/// Web stub for save-game persistence: silently skips all I/O.
+library;
+
+import 'dart:typed_data';
+
+import 'package:wolf_3d_dart/src/engine/save/save_game_persistence.dart';
+import 'package:wolf_3d_dart/wolf_3d_data_types.dart';
+
+/// No-op implementation used on web, where dart:io is unavailable.
+class DefaultSaveGamePersistence extends SaveGamePersistence {
+  // ignore: avoid_unused_constructor_parameters
+  DefaultSaveGamePersistence({String? directoryPath});
+
+  @override
+  Future<Uint8List?> load({
+    required int slot,
+    required GameVersion version,
+  }) async => null;
+
+  @override
+  Future<bool> exists({
+    required int slot,
+    required GameVersion version,
+  }) async => false;
+
+  @override
+  Future<void> save({
+    required int slot,
+    required GameVersion version,
+    required Uint8List bytes,
+  }) async {}
+}

packages/wolf_3d_dart/lib/src/platform/platform_config_dir.dart

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+/// Returns the platform-appropriate Wolf3D config directory path.
+///
+/// This file is only ever imported by native (dart:io) code paths and must
+/// never be loaded on web.
+library;
+
+import 'dart:io';
+
+/// Returns the Wolf3D config directory for the current platform.
+///
+/// - Linux: `$XDG_CONFIG_HOME/wolf3d` (defaults to `~/.config/wolf3d`)
+/// - macOS: `~/Library/Application Support/wolf3d`
+/// - Windows: `%APPDATA%/wolf3d`
+/// - Other: `~/.config/wolf3d`
+String platformConfigDir() {
+  if (Platform.isLinux) {
+    final String xdg = Platform.environment['XDG_CONFIG_HOME'] ?? '';
+    final String home = Platform.environment['HOME'] ?? '.';
+    return xdg.isNotEmpty ? '$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';
+}