Initial flame_lua_runtime package

lib/runtime/packages/game_package.dart

@@ -0,0 +1,96 @@
+import 'dart:io';
+
+import 'package:flutter/services.dart';
+
+import '../game/runtime_options.dart';
+import 'game_package_manifest.dart';
+
+class GamePackage {
+  const GamePackage.asset({
+    required this.rootPath,
+    required this.manifest,
+    this.runtimeLuaRoot = RuntimeOptions.defaultRuntimeLuaRoot,
+  }) : source = GamePackageSource.asset;
+
+  static const runtimeLuaPrefix = 'runtime:';
+
+  const GamePackage.file({
+    required this.rootPath,
+    required this.manifest,
+    this.runtimeLuaRoot = RuntimeOptions.defaultRuntimeLuaRoot,
+  }) : source = GamePackageSource.file;
+
+  final String rootPath;
+  final GamePackageSource source;
+  final GamePackageManifest manifest;
+  final String runtimeLuaRoot;
+
+  String get entryPath => _join(rootPath, manifest.entry);
+
+  bool get isAsset => source == GamePackageSource.asset;
+
+  Future<String> readText(String relativeOrAbsolutePath) async {
+    final runtimePath = _resolveRuntimeLuaPath(relativeOrAbsolutePath);
+    if (runtimePath != null) {
+      return rootBundle.loadString(runtimePath);
+    }
+
+    final path = _resolvePackagePath(relativeOrAbsolutePath);
+    if (isAsset) {
+      return rootBundle.loadString(path);
+    }
+    return File(path).readAsString();
+  }
+
+  Future<ByteData> readBytes(String relativeOrAbsolutePath) async {
+    final path = _resolvePackagePath(relativeOrAbsolutePath);
+    if (isAsset) {
+      return rootBundle.load(path);
+    }
+    final bytes = await File(path).readAsBytes();
+    return ByteData.sublistView(bytes);
+  }
+
+  String resolveResourcePath(String keyOrPath) {
+    final resource = manifest.resources[keyOrPath];
+    if (resource != null) {
+      return _join(rootPath, resource.path);
+    }
+
+    if (keyOrPath.startsWith(rootPath)) {
+      return keyOrPath;
+    }
+    if (keyOrPath.contains('/')) {
+      return _join(rootPath, keyOrPath);
+    }
+    return _join(_join(rootPath, manifest.assetsBase), keyOrPath);
+  }
+
+  String _resolvePackagePath(String relativeOrAbsolutePath) {
+    if (relativeOrAbsolutePath.startsWith(rootPath)) {
+      return relativeOrAbsolutePath;
+    }
+    return _join(rootPath, relativeOrAbsolutePath);
+  }
+
+  String? _resolveRuntimeLuaPath(String path) {
+    if (!path.startsWith(runtimeLuaPrefix)) {
+      return null;
+    }
+    final name = path.substring(runtimeLuaPrefix.length);
+    if (name.isEmpty || name.contains('/') || name.contains('..')) {
+      throw FormatException('Invalid runtime Lua module path: $path');
+    }
+    return _join(runtimeLuaRoot, name);
+  }
+
+  String _join(String left, String right) {
+    final normalizedLeft = left.endsWith('/')
+        ? left.substring(0, left.length - 1)
+        : left;
+    final normalizedRight = right.startsWith('/') ? right.substring(1) : right;
+    return '$normalizedLeft/$normalizedRight';
+  }
+}
+
+enum GamePackageSource { asset, file }