tane/apps/app_seeds/lib/services/social_account_store.dart

import '../security/secret_store.dart';

/// The per-identity key scope for [account]: empty for the original identity
/// (account 0, so its data keeps the legacy un-namespaced keys), otherwise a
/// distinct namespace. Used by the per-identity stores (chats, profile, name
/// cache) so switching identity never mixes one identity's data into another.
String socialAccountScope(int account) => account == 0 ? '' : 'acct$account';

/// Remembers which social identity ("account") of the root seed is active, and
/// how many the user has created, so identities can be switched and listed.
///
/// Each account is a pseudonymous Nostr identity deterministically derived from
/// the SAME root seed (see `NostrKeyDerivation.deriveFromSeed`), so switching
/// never adds anything to back up — the one seed still regenerates them all.
/// Keystore-backed: no plaintext at rest.
class SocialAccountStore {
  SocialAccountStore(this._store);

  final SecretStore _store;

  static const _activeKey = 'tane.social.account.active';
  static const _maxKey = 'tane.social.account.max';

  /// The active account index (0 = the original identity).
  Future<int> active() async => _readInt(_activeKey);

  /// The highest account index ever created (so the list is 0..max and a new
  /// identity takes max + 1). At least the active one always exists.
  Future<int> maxCreated() async {
    final max = await _readInt(_maxKey);
    final activeIdx = await active();
    return max > activeIdx ? max : activeIdx;
  }

  /// Switches the active identity to [account] (must already be within
  /// 0..maxCreated, or be maxCreated + 1 for a freshly created one).
  Future<void> setActive(int account) async {
    if (account < 0) {
      throw ArgumentError.value(account, 'account', 'must be >= 0');
    }
    await _store.write(_activeKey, '$account');
    if (account > await _readInt(_maxKey)) {
      await _store.write(_maxKey, '$account');
    }
  }

  /// Creates a brand-new identity (the next index) and makes it active. Returns
  /// the new account index.
  Future<int> createNew() async {
    final next = await maxCreated() + 1;
    await setActive(next);
    return next;
  }

  Future<int> _readInt(String key) async {
    final raw = await _store.read(key);
    if (raw == null || raw.isEmpty) return 0;
    return int.tryParse(raw) ?? 0;
  }
}