applyEvent method

@override InvoiceState applyEvent(InvoiceState state, Event event)

Applies event to state and returns the next state (bead libspiffy-mmb). state is never modified; eventador's eventHandler replaces the aggregate's state with the result once the event has applied, so an event that fails midway changes nothing.

Implementation

@override
InvoiceState applyEvent(InvoiceState state, Event event) {
  if (event is! InvoiceEvent) {
    throw ArgumentError('Expected InvoiceEvent, got ${event.runtimeType}');
  }

  return switch (event) {
    final InvoiceCreatedEvent evt => _applyInvoiceCreated(state, evt),
    // Replay-only: nothing emits InvoiceStatusChangedEvent any more
    // (reachability sweep 2026-09-18, section 2). The arm stays because a
    // journal written by an earlier release may contain the event and must
    // still replay to the same state.
    // ignore: deprecated_member_use_from_same_package
    final InvoiceStatusChangedEvent evt => _applyInvoiceStatusChanged(state, evt),
    final InvoicePaidEvent evt => _applyInvoicePaid(state, evt),
    final InvoiceExpiredEvent evt => _applyInvoiceExpired(state, evt),
    final InvoiceCancelledEvent evt => _applyInvoiceCancelled(state, evt),
    _ => throw ArgumentError('Unknown event type: ${event.runtimeType}'),
  };
}