resolveWebModelUrl function

Future<String> resolveWebModelUrl(String rawPath)

Resolves rawPath — a model or tokenizer path core registered for an installed file — to a URL that fetch() can load.

opfs://<filename> (streaming storage) becomes a blob: URL of that OPFS file (the file itself, not a copy); any other path is returned unchanged. Throws StateError when an opfs:// path arrives while streaming storage is not enabled or OPFS is not available, and an Exception naming the file when OPFS has no such file.

Ownership: the blob: URL made for an opfs:// path is a NEW object URL that belongs to the caller. Revoke it (URL.revokeObjectURL) once its consumer has read the file — on success and on failure alike. Any other path is returned as it came and is not the caller's: never revoke it (core may own it).

Implementation

Future<String> resolveWebModelUrl(String rawPath) async {
  if (!rawPath.startsWith('opfs://')) return rawPath;

  final registry = ServiceRegistry.instance;
  if (!registry.useStreamingStorage) {
    throw StateError(
      'Got an "opfs://" path ("$rawPath") but streaming storage is not '
      'enabled (webStorageMode != WebStorageMode.streaming).',
    );
  }
  final downloadService = registry.downloadService;
  if (downloadService is! WebDownloadService) {
    throw StateError(
      'Expected WebDownloadService to resolve "$rawPath" on web.',
    );
  }
  if (downloadService.opfsService == null) {
    throw StateError(
      'OPFS service not available for "$rawPath" (streaming mode requires '
      'OPFS).',
    );
  }

  final filename = rawPath.substring('opfs://'.length);
  final JSObject file;
  try {
    final root = await _storage.getDirectory().toDart;
    final handle = await root.getFileHandle(filename.toJS).toDart;
    file = await handle.getFile().toDart;
  } catch (e) {
    throw Exception('Model not found in OPFS: $filename ($e)');
  }
  return _createObjectUrlJs(file).toDart;
}