decode static method

LiveSnapshot decode(String text)

Reads text: a file written by export --to, the output of export --json, or a bare {"storage": ..., "backpack": ...} object.

Throws a FormatException saying what's wrong.

Implementation

static LiveSnapshot decode(String text) {
  Object? decoded;
  try {
    decoded = jsonDecode(text);
  } on FormatException catch (e) {
    throw FormatException('isn\'t valid JSON (${e.message})');
  }
  // export --json prints [{device, ok, result}].
  if (decoded is List) {
    if (decoded.length != 1 || decoded.single is! Map) {
      throw FormatException(
        'holds ${decoded.length} apps\' results; export one app at a time',
      );
    }
    decoded = (decoded.single as Map)['result'];
  }
  if (decoded is Map &&
      decoded['result'] is Map &&
      !decoded.containsKey('storage')) {
    decoded = decoded['result'];
  }
  if (decoded is! Map ||
      !decoded.containsKey('storage') && !decoded.containsKey('backpack')) {
    throw const FormatException(
      'should be a JSON object with "storage" and "backpack"',
    );
  }
  final Object? version = decoded['nylo'];
  if (version is num && version > formatVersion) {
    throw FormatException(
      'uses snapshot format $version, newer than this Metro '
      '(format $formatVersion). Update nylo_framework',
    );
  }
  return LiveSnapshot(
    storage: _stringKeyed(decoded['storage'], 'storage'),
    backpack: _stringKeyed(decoded['backpack'], 'backpack'),
    app: _text(decoded['app']),
    env: _text(decoded['env']),
    device: _text(decoded['device']),
    route: _text(decoded['route']),
    exportedAt: DateTime.tryParse(_text(decoded['exportedAt']) ?? ''),
  );
}