Initial commit

lib/features/downloader/data/io_file_system.dart

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+import 'dart:async';
+import 'dart:io';
+
+import 'package:crypto/crypto.dart' as c;
+import 'package:injectable/injectable.dart';
+import 'package:moonwell_launcher/features/downloader/domain/repositories/file_system.dart';
+
+@LazySingleton(as: FileSystem)
+class IoFileSystem implements FileSystem {
+  @override
+  Future<void> ensureParentExists(String path) =>
+      File(path).parent.create(recursive: true);
+
+  @override
+  Future<bool> exists(String path) => File(path).exists();
+
+  @override
+  Future<int> sizeOf(String path) async => (await File(path).stat()).size;
+
+  @override
+  Future<void> truncate(String path) async =>
+      File(path).writeAsBytes(const [], flush: true);
+
+  @override
+  Future<void> createEmpty(String path) => File(path).create(recursive: true);
+
+  @override
+  Future<StreamSink<List<int>>> openAppend(String path) async =>
+      File(path).openWrite(mode: FileMode.append);
+
+  @override
+  Future<bool> verifyFile(
+    String path, {
+    required String expected,
+    required String algo,
+  }) async {
+    final file = File(path);
+    if (!await file.exists()) return false;
+
+    final digestHex = await _computeDigestHex(file, algo);
+    return _constantTimeEquals(digestHex.toLowerCase(), expected.toLowerCase());
+  }
+
+  Future<String> _computeDigestHex(File file, String algo) async {
+    final hash = switch (algo.toLowerCase()) {
+      'md5' => c.md5,
+      'sha256' => c.sha256,
+      _ => throw ArgumentError('Unsupported checksum algo: $algo'),
+    };
+
+    // Stream the file into the hash converter; no extra buffers.
+    final digest = await hash.bind(file.openRead()).first; // -> c.Digest
+    return digest.toString(); // lowercase hex
+  }
+
+  bool _constantTimeEquals(String a, String b) {
+    if (a.length != b.length) return false;
+    var result = 0;
+    for (var i = 0; i < a.length; i++) {
+      result |= a.codeUnitAt(i) ^ b.codeUnitAt(i);
+    }
+    return result == 0;
+  }
+}

lib/features/downloader/data/minio_storage_reader.dart

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+import 'package:injectable/injectable.dart';
+import 'package:minio/minio.dart';
+import 'package:moonwell_launcher/features/downloader/domain/entities/remote_object_meta.dart';
+import 'package:moonwell_launcher/features/downloader/domain/repositories/storage_reader.dart';
+
+/// MinIO storage reader implementation.
+@LazySingleton(as: StorageReader)
+class MinioStorageReader implements StorageReader {
+  final Minio _client;
+
+  MinioStorageReader(this._client);
+
+  @override
+  Future<Stream<List<int>>> readFromOffset({
+    required String bucket,
+    required String key,
+    required int startOffset,
+  }) {
+    return _client.getPartialObject(bucket, key, startOffset);
+  }
+
+  @override
+  Future<RemoteObjectMeta> stat({
+    required String bucket,
+    required String key,
+  }) async {
+    final s = await _client.statObject(bucket, key);
+    return RemoteObjectMeta(size: s.size ?? 0, eTag: s.etag ?? '');
+  }
+}