/**
 * Duplicate-PO prefill (issue #142) — map a source PurchaseOrder onto the
 * initial-value props the New PO form consumes. Pure (no DB / no I/O) so the
 * mapping is unit-testable; the page just fetches the PO and hands it here.
 *
 * Nothing is written: a duplicate is only a prefilled draft. Attachments,
 * status/dates, payment data and audit history are intentionally NOT copied —
 * a duplicate starts as a clean draft of the editable order fields.
 */
import { parsePoTerms, legacyPoTerms } from "@/lib/terms";
import type { PoTerm } from "@/lib/terms";
import type { LineItemInput } from "@/lib/validations/po";

type DecimalLike = { toNumber: () => number } | number | null | undefined;

const num = (v: DecimalLike, fallback = 0): number =>
  v == null ? fallback : typeof v === "number" ? v : v.toNumber();

export type DuplicateSourceLineItem = {
  name: string;
  description?: string | null;
  quantity: DecimalLike;
  unit: string;
  size?: string | null;
  unitPrice: DecimalLike;
  gstRate?: DecimalLike;
  productId?: string | null;
  accountId?: string | null;
};

export type DuplicateSourcePo = {
  title: string;
  vesselId: string;
  accountId: string;
  companyId?: string | null;
  vendorId?: string | null;
  projectCode?: string | null;
  placeOfDelivery?: string | null;
  dateRequired?: Date | null;
  piQuotationNo?: string | null;
  piQuotationDate?: Date | null;
  requisitionNo?: string | null;
  requisitionDate?: Date | null;
  terms?: unknown;
  tcDelivery?: string | null;
  tcDispatch?: string | null;
  tcInspection?: string | null;
  tcTransitInsurance?: string | null;
  tcPaymentTerms?: string | null;
  tcOthers?: string | null;
  lineItems: DuplicateSourceLineItem[];
};

export type DuplicatePrefill = {
  initialLineItems: LineItemInput[];
  initialMultiAccount: boolean;
  initialVendorId?: string;
  initialVesselId: string;
  initialCompanyId?: string;
  initialTitle: string;
  initialAccountId: string;
  initialProjectCode: string | null;
  initialPlaceOfDelivery: string | null;
  initialDateRequired?: string;
  initialPiQuotationNo?: string;
  initialPiQuotationDate?: string;
  initialRequisitionNo?: string;
  initialRequisitionDate?: string;
  initialTerms: PoTerm[];
};

/** Format a Date to a `yyyy-MM-dd` value for a native date input. */
export const toDateInputValue = (d: Date | null | undefined): string | undefined =>
  d ? new Date(d).toISOString().split("T")[0] : undefined;

export function buildDuplicatePrefill(source: DuplicateSourcePo): DuplicatePrefill {
  const savedTerms = parsePoTerms(source.terms);
  return {
    initialLineItems: source.lineItems.map((li) => ({
      name: li.name,
      description: li.description ?? "",
      quantity: num(li.quantity, 1),
      unit: li.unit,
      size: li.size ?? "",
      unitPrice: num(li.unitPrice, 0),
      gstRate: li.gstRate != null ? num(li.gstRate, 0.18) : 0.18,
      productId: li.productId ?? undefined,
      accountId: li.accountId ?? undefined,
    })),
    initialMultiAccount: source.lineItems.some((li) => !!li.accountId),
    initialVendorId: source.vendorId ?? undefined,
    initialVesselId: source.vesselId,
    initialCompanyId: source.companyId ?? undefined,
    initialTitle: source.title,
    initialAccountId: source.accountId,
    initialProjectCode: source.projectCode ?? null,
    initialPlaceOfDelivery: source.placeOfDelivery ?? null,
    initialDateRequired: toDateInputValue(source.dateRequired),
    initialPiQuotationNo: source.piQuotationNo ?? undefined,
    initialPiQuotationDate: toDateInputValue(source.piQuotationDate),
    initialRequisitionNo: source.requisitionNo ?? undefined,
    initialRequisitionDate: toDateInputValue(source.requisitionDate),
    initialTerms: savedTerms.length > 0 ? savedTerms : legacyPoTerms(source),
  };
}