/**
 * Selection helper for the "recent orders" / "recent drafts" lists.
 *
 * A single order can accumulate several invoice rows over its lifetime
 * (regenerations bump the `version`, cancel-and-reissue cancels the old row
 * and issues a new one). Crucially, a CANCELLED invoice can carry a HIGHER
 * `version` than the current active one, so picking "highest version wins"
 * would surface a stale cancelled invoice and hide the live one — the order
 * would render as if it had no invoice ("Generate" button) even though a
 * valid issued invoice exists.
 *
 * The correct representative for the UI is the latest NON-cancelled invoice;
 * only when every row is cancelled do we fall back to the latest cancelled
 * one (so the order can still show its "cancelled" state).
 */

export interface RepresentativeInvoiceRow {
  orderId: string;
  version: number;
  cancelledAt: Date | null;
}

/**
 * Build a map of orderId -> representative invoice.
 *
 * @param invoices Invoice rows for the relevant orders. MUST already be sorted
 *   by `version` descending (then `createdAt` descending), matching the
 *   Prisma query order, so the first non-cancelled row encountered per order
 *   is the highest-version active invoice.
 */
export function buildRepresentativeInvoiceMap<T extends RepresentativeInvoiceRow>(
  invoices: T[],
): Map<string, T> {
  const byOrder = new Map<string, T>();
  for (const inv of invoices) {
    const existing = byOrder.get(inv.orderId);
    if (!existing) {
      byOrder.set(inv.orderId, inv);
      continue;
    }
    // Upgrade from a cancelled placeholder to the first active invoice seen.
    if (existing.cancelledAt && !inv.cancelledAt) {
      byOrder.set(inv.orderId, inv);
    }
  }
  return byOrder;
}