import { YardCountry, type ScheduleTradeDirection } from '@edr/types';

type YardLike = { country?: string | null };

/**
 * Derive trade direction from origin and destination yard countries.
 * Ethiopia → Djibouti = EXPORT, Djibouti → Ethiopia = IMPORT, same country =
 * DOMESTIC (shown as "Intercity"; scheduling/contracts reject it for now).
 * Comparison is strict against the YardCountry enum values the yards table is
 * constrained to; the trim/case fold only shields legacy rows.
 */
export function deriveTradeDirection(
  originYard: YardLike,
  destinationYard: YardLike,
): ScheduleTradeDirection {
  const origin = normalizeCountry(originYard.country);
  const destination = normalizeCountry(destinationYard.country);

  if (origin === YardCountry.DJIBOUTI && destination === YardCountry.ETHIOPIA) {
    return 'IMPORT';
  }
  if (origin === YardCountry.ETHIOPIA && destination === YardCountry.DJIBOUTI) {
    return 'EXPORT';
  }
  return 'DOMESTIC';
}

function normalizeCountry(country: string | null | undefined): YardCountry | null {
  const folded = country?.trim().toLowerCase();
  if (folded === YardCountry.ETHIOPIA.toLowerCase()) return YardCountry.ETHIOPIA;
  if (folded === YardCountry.DJIBOUTI.toLowerCase()) return YardCountry.DJIBOUTI;
  return null;
}