/**
 * Per-locale formatters used in PDF rendering. We pin these to specific
 * locales (de-AT for German invoices) so that the output is deterministic
 * regardless of the runtime's default locale.
 */

const MONEY_FORMATTERS = new Map<string, Intl.NumberFormat>();
const QTY_FORMATTERS = new Map<string, Intl.NumberFormat>();
const DATE_FORMATTERS = new Map<string, Intl.DateTimeFormat>();

function localeFor(language: string): string {
  return language === "en" ? "en-GB" : "de-AT";
}

export function formatMoney(
  amount: number | string,
  currency: string,
  language: string,
): string {
  const num = typeof amount === "string" ? Number(amount) : amount;
  const key = `${language}|${currency}`;
  let f = MONEY_FORMATTERS.get(key);
  if (!f) {
    f = new Intl.NumberFormat(localeFor(language), {
      style: "decimal",
      minimumFractionDigits: 2,
      maximumFractionDigits: 2,
    });
    MONEY_FORMATTERS.set(key, f);
  }
  return `${f.format(Number.isFinite(num) ? num : 0)} ${currency}`;
}

export function formatQuantity(qty: number, unit: string, language: string): string {
  let f = QTY_FORMATTERS.get(language);
  if (!f) {
    f = new Intl.NumberFormat(localeFor(language), {
      minimumFractionDigits: 2,
      maximumFractionDigits: 2,
    });
    QTY_FORMATTERS.set(language, f);
  }
  return `${f.format(qty)} ${unit}`;
}

export function formatDate(date: Date | string, language: string): string {
  const d = typeof date === "string" ? new Date(date) : date;
  let f = DATE_FORMATTERS.get(language);
  if (!f) {
    f = new Intl.DateTimeFormat(localeFor(language), {
      day: "2-digit",
      month: "2-digit",
      year: "numeric",
    });
    DATE_FORMATTERS.set(language, f);
  }
  return f.format(d);
}

/** Adds days to a date, returning a new Date. */
export function addDays(date: Date, days: number): Date {
  const d = new Date(date);
  d.setDate(d.getDate() + days);
  return d;
}

/**
 * Formats a percentage. Tax rates from Shopify can be either 0.20 or 20 — we
 * accept both shapes via heuristics.
 */
export function formatTaxRate(rate: number, language: string): string {
  const pct = rate <= 1 ? rate * 100 : rate;
  const f = new Intl.NumberFormat(localeFor(language), {
    minimumFractionDigits: 0,
    maximumFractionDigits: 2,
  });
  return `${f.format(pct)}%`;
}