import { TrainSchedule } from './entities/train-schedule.entity';

export type TrainRunSource = Pick<TrainSchedule, 'trainNumber' | 'voyageNumber'>;

/**
 * How a departure is named in every customer-facing SMS / email:
 *
 *   "train 8001 (voyage V-2026-117)"
 *
 * Both identifiers are the SCHEDULE's own columns — `train_schedules.train_number`
 * and `train_schedules.voyage_number`. The built train (`freight.trains`) carries
 * a `train_name` that the build form labels "voyage number"; that is a different
 * identifier and must never be quoted to customers. Always pass the schedule.
 *
 * Returns null when the schedule has neither number (older rows, or an unbuilt
 * departure whose pool number is assigned at dispatch) so callers can fall back
 * to a generic phrase instead of printing "train (voyage)".
 */
export function trainRunLabel(
  schedule: TrainRunSource | null | undefined,
  opts: { capitalize?: boolean } = {},
): string | null {
  if (!schedule) return null;
  const train = schedule.trainNumber?.trim() || null;
  const voyage = schedule.voyageNumber?.trim() || null;
  if (!train && !voyage) return null;
  const head = train ? `train ${train}` : 'train';
  const label = voyage ? `${head} (voyage ${voyage})` : head;
  return opts.capitalize ? label.charAt(0).toUpperCase() + label.slice(1) : label;
}