import policy from "./invoice-booking-policy.json";

// Single source of truth for the amount an invoice line contributes to a machine's
// income. The flag itself lives in ./invoice-booking-policy.json because the CLI
// booking script must obey exactly the same rule — two copies of a financial
// constant will eventually disagree.
//
// Client ruling, 2026-10-01: amounts are booked VAT-INCLUSIVE, i.e. the figure the
// debtor actually pays. Set `bookInclusiveVat: false` in the JSON to book ex-VAT
// instead, then re-run `npm run seed && node scripts/book-invoice.mjs`.
export const BOOK_INCLUSIVE_VAT = policy.bookInclusiveVat;

// The amount to post to monthly_income for one invoice line.
export function bookedAmount(amountExcl: number, vat: number): number {
  const r = (n: number) => Math.round((n || 0) * 100) / 100;
  return BOOK_INCLUSIVE_VAT ? r(amountExcl) + r(vat) : r(amountExcl);
}

// Label for whichever mode is active, so the UI never says "ex VAT" while booking
// the inclusive figure (or the reverse).
export const BOOKED_LABEL = BOOK_INCLUSIVE_VAT ? "incl VAT" : "ex VAT";
export const BOOKED_LONG_LABEL = BOOK_INCLUSIVE_VAT
  ? "Booked to income (incl VAT)"
  : "Booked to income (ex VAT)";