/** The booking fields that decide who hauls the road legs. */
export interface MileHaulageRow {
  tradeDirection: string | null;
  /** `first_mile_pickup_address` — set when the customer asked EDR to collect. */
  firstMile: string | null;
  /** `last_mile_delivery_address` — set when the customer asked EDR to deliver. */
  lastMile: string | null;
}

/**
 * Whether the customer bought the EDR road leg that matters for their direction:
 * delivery at the end of an import, collection at the start of an export. A
 * DOMESTIC booking can use either, so either one counts.
 *
 * The address is the signal because it is the only per-booking record of the
 * choice. `service_types.includes_first_mile` / `includes_last_mile` cannot be
 * used — every service type ships with both set to true, so reading them would
 * mean every booking uses EDR haulage and none could ever self-haul.
 */
export function usesEdrMileService(booking: MileHaulageRow): boolean {
  const hasFirstMile = Boolean(booking.firstMile?.trim());
  const hasLastMile = Boolean(booking.lastMile?.trim());
  switch (booking.tradeDirection) {
    case 'IMPORT':
      return hasLastMile;
    case 'EXPORT':
      return hasFirstMile;
    default:
      return hasFirstMile || hasLastMile;
  }
}

/**
 * EDR haulage and a customer's own truck are alternatives, never both. Whichever
 * side is being set up, it has to reject the other — a guard on only one side
 * lets the two paths open on the same booking, each unaware of the other.
 */
export const SELF_HAUL_CONFLICT_MESSAGE =
  'This booking is delivered by the customer’s own truck — an EDR mile leg cannot also be assigned.';

export const EDR_HAULAGE_CONFLICT_MESSAGE =
  'Customer truck assignment is only allowed when first/last mile delivery is not selected, or when the EDR last-mile request has not been approved';

/** The booking fields that decide whether the customer may still bring their own truck. */
export interface MileCommitmentRow extends MileHaulageRow {
  /**
   * EDR has actually committed to the delivery leg: the booking's last-mile
   * request was approved, or a `freight.last_mile` leg row exists for it.
   * Selecting delivery on the contract is only a request — see
   * `edrHaulsThisBooking`.
   */
  lastMileCommitted: boolean;
}

/**
 * SQL for `MileCommitmentRow.lastMileCommitted`, to be selected alongside the
 * booking row aliased `b`. Both services that gate self-haul read the same
 * fragment so the rule cannot drift between them.
 */
export const LAST_MILE_COMMITTED_SQL = `(
  EXISTS (SELECT 1
            FROM freight.last_mile lm
           WHERE lm.booking_id = b.id AND lm.deleted_at IS NULL)
  OR EXISTS (SELECT 1
               FROM freight.last_mile_requests lmr
              WHERE lmr.booking_id = b.id
                AND lmr.deleted_at IS NULL
                AND lmr.status = 'APPROVED')
)`;

/**
 * Whether EDR is hauling this booking's road leg, such that the customer may
 * NOT assign their own truck. Stricter than `usesEdrMileService` on the
 * delivery side: choosing last-mile delivery on the contract opens a request
 * that the Truck & Machinery chief still has to approve, and until that
 * approval the customer is free to self-haul instead. Collection (the export
 * leg) has no approval step, so the contract choice alone decides it.
 *
 * `usesEdrMileService` keeps answering the other question — whether the booking
 * belongs in the EDR mile queues at all — and the queue side still refuses a
 * booking that already carries a customer truck, so the two paths remain
 * mutually exclusive whichever acts first.
 */
export function edrHaulsThisBooking(booking: MileCommitmentRow): boolean {
  const hasFirstMile = Boolean(booking.firstMile?.trim());
  const lastMileApproved = Boolean(booking.lastMile?.trim()) && booking.lastMileCommitted;
  switch (booking.tradeDirection) {
    case 'IMPORT':
      return lastMileApproved;
    case 'EXPORT':
      return hasFirstMile;
    default:
      return hasFirstMile || lastMileApproved;
  }
}

/**
 * The road legs are chosen on the contract. A booking whose contract bought
 * neither has no business in the first/last-mile queues at all.
 */
export const NO_MILE_SERVICE_MESSAGE =
  'This booking did not select first/last mile delivery on its contract, so it cannot be assigned an EDR mile leg.';