import 'dart:io';

/// The private keys of imported client certificates, as PEM files in the app's
/// own storage. The database keeps the public certificate; the key stays out
/// of it, so a copy of the database never carries a reader's identity.
///
/// The operations are synchronous on purpose: they touch one small file at a
/// time, only when the reader imports or uses an identity, and staying off the
/// event loop keeps them completing within a single interaction.
class KeyStore {
  KeyStore(this._root);

  /// The directory the keys live in, resolved lazily because finding it asks
  /// the platform.
  final Future<Directory> Function() _root;

  Future<File> _file(int id) async {
    final root = await _root();
    return File('${root.path}${Platform.pathSeparator}$id.pem');
  }

  /// Stores the key of the certificate with this id.
  Future<void> save(int id, String pem) async {
    final file = await _file(id);
    file.parent.createSync(recursive: true);
    file.writeAsStringSync(pem);
  }

  /// The key of the certificate with this id, or null when there is none.
  Future<String?> read(int id) async {
    final file = await _file(id);
    if (!file.existsSync()) return null;
    return file.readAsStringSync();
  }

  /// Removes the key of the certificate with this id.
  Future<void> delete(int id) async {
    final file = await _file(id);
    if (file.existsSync()) file.deleteSync();
  }
}