feat: video download

Signed-off-by: bggRGjQaUbCoE <githubaccount56556@proton.me>

lib/utils/path_utils.dart

@@ -0,0 +1,29 @@
+import 'dart:io' show Platform;
+
+import 'package:path/path.dart' as path;
+
+late final String tmpDirPath;
+
+late final String appSupportDirPath;
+
+late String downloadPath;
+
+String get defDownloadPath =>
+    path.join(appSupportDirPath, PathUtils.downloadDir);
+
+abstract final class PathUtils {
+  static const videoNameType1 = '0.mp4';
+  static const _fileExt = '.m4s';
+  static const audioNameType2 = 'audio$_fileExt';
+  static const videoNameType2 = 'video$_fileExt';
+  static const downloadDir = 'download';
+
+  static String buildShadersAbsolutePath(
+    String baseDirectory,
+    List<String> shaders,
+  ) {
+    return shaders
+        .map((shader) => path.join(baseDirectory, shader))
+        .join(Platform.isWindows ? ';' : ':');
+  }
+}