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

export function usePrice() {
  const { currency } = usePrefs();
  const { locale } = useI18n();
  const { $api } = useNuxtApp();
  const currencies = useState<Currency[]>("mall-currencies", () => []);
  const cache = useState<Map<string, number>>("mall-price-cache", () => new Map());
  const currencyRequest = useState<Promise<Currency[]> | null>("mall-currency-request", () => null);

  async function ensureCurrencies(): Promise<Currency[]> {
    if (currencies.value.length > 0) return currencies.value;
    if (!currencyRequest.value) {
      currencyRequest.value = $api.listCurrencies().then((list) => {
        currencies.value = list;
        return list;
      }).finally(() => {
        currencyRequest.value = null;
      });
    }
    return currencyRequest.value;
  }

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

  async function convertAmount(amountMinor: number, from: string, to = currency.value): Promise<number> {
    if (from === to) return amountMinor;
    const key = `${amountMinor}:${from}:${to}`;
    const cached = cache.value.get(key);
    if (cached !== undefined) return cached;
    const converted = await $api.convert(amountMinor, from, to);
    cache.value.set(key, converted.amount_minor);
    return converted.amount_minor;
  }

  async function formatPrice(amountMinor: number, from: string, to = currency.value): Promise<string> {
    await ensureCurrencies();
    const amount = await convertAmount(amountMinor, from, to);
    return formatMoney(amount, to, exponentFor(to), locale.value);
  }

  async function formatAmount(amountMinor: number, code: string): Promise<string> {
    await ensureCurrencies();
    return formatMoney(amountMinor, code, exponentFor(code), locale.value);
  }

  return {
    currency,
    currencies,
    cache,
    ensureCurrencies,
    exponentFor,
    convertAmount,
    formatPrice,
    formatAmount,
  };
}