import '../model/account_data.dart';

/// Joins concurrent calls into the one already running for the same account
/// session. A run left over from a signed-out session never blocks the next
/// account's first call.
class SessionSingleFlight {
  Future<void>? _running;
  int? _epoch;

  Future<void> run(Future<void> Function() action) {
    final epoch = AccountData().sessionEpoch;
    final running = _running;
    if (running != null && _epoch == epoch) return running;
    _epoch = epoch;
    late final Future<void> current;
    current = action().whenComplete(() {
      if (identical(_running, current)) _running = null;
    });
    return _running = current;
  }
}