import { formatMoney } from "@vmall/shared";
import type { Currency } from "@vmall/shared";

/** Currency-aware money formatter: exponents come from the API, cached app-wide. */
export function useMoney() {
  const { $api } = useNuxtApp();
  const { locale } = useI18n();
  const currencies = useState<Currency[]>("vmall.currencies", () => []);

  async function load(): Promise<void> {
    if (currencies.value.length > 0) return;
    try {
      currencies.value = await $api.listCurrencies();
    } catch {
      /* keep empty; fmt falls back to exponent 2 */
    }
  }

  function exponentOf(currency: string): number {
    return currencies.value.find((c) => c.code === currency)?.exponent ?? 2;
  }

  function fmt(amountMinor: number, currency: string): string {
    return formatMoney(amountMinor, currency, exponentOf(currency), locale.value);
  }

  /** Currency for money fields without an explicit currency: the table's base. */
  const shopCurrency = computed(
    () => currencies.value.find((c) => c.is_base)?.code ?? currencies.value[0]?.code ?? "USD",
  );

  /** Parse a major-unit decimal string into integer minor units; null when invalid. */
  function majorToMinor(value: string, currency: string): number | null {
    const clean = value.trim();
    if (!/^\d+(?:\.\d+)?$/.test(clean)) return null;
    const exponent = exponentOf(currency);
    const [whole, fraction = ""] = clean.split(".");
    if (fraction.length > exponent) return null;
    const minor = Number(whole) * 10 ** exponent + Number(fraction.padEnd(exponent, "0") || 0);
    return Number.isSafeInteger(minor) ? minor : null;
  }

  /** Render integer minor units as a major-unit string for form inputs. */
  function minorToMajor(minor: number, currency: string): string {
    const exponent = exponentOf(currency);
    const sign = minor < 0 ? "-" : "";
    const abs = Math.abs(minor);
    const whole = Math.trunc(abs / 10 ** exponent);
    if (exponent === 0) return `${sign}${whole}`;
    const fraction = (abs % 10 ** exponent).toString().padStart(exponent, "0");
    return `${sign}${whole}.${fraction}`;
  }

  return { currencies, load, fmt, shopCurrency, majorToMinor, minorToMajor };
}