/**
 * Toolkit - Currency Formatting
 * 
 * Simple currency formatting. Currency code comes from user's WHMCS profile.
 * Typically JPY for this application.
 */

export type SupportedCurrency = "JPY" | "USD" | "EUR";

/**
 * Format a number as currency using WHMCS default currency
 * 
 * @param amount - The numeric amount to format
 * @param currencyCode - Optional currency code (defaults to WHMCS default)
 * @param locale - Optional locale (defaults to currency-specific locale)
 * 
 * @example
 * formatCurrency(1000)                    // Uses WHMCS default currency
 * formatCurrency(1000, "USD")            // Uses specific currency
 * formatCurrency(1000, "JPY", "ja-JP")  // Uses specific currency and locale
 */
export function formatCurrency(
  amount: number, 
  currencyCode: string = "JPY", 
  locale?: string
): string {
  // Use provided locale or get from currency
  const currencyLocale = locale || getCurrencyLocale(currencyCode as SupportedCurrency);

  // Determine fraction digits based on currency
  const fractionDigits = currencyCode === "JPY" ? 0 : 2;

  const formatter = new Intl.NumberFormat(currencyLocale, {
    style: "currency",
    currency: currencyCode,
    minimumFractionDigits: fractionDigits,
    maximumFractionDigits: fractionDigits,
  });

  return formatter.format(amount);
}

/**
 * Parse a currency string to a number
 */
export function parseCurrency(value: string): number | null {
  // Remove currency symbols, commas, and whitespace
  const cleaned = value.replace(/[¥$€,\s]/g, "");
  const parsed = Number.parseFloat(cleaned);
  return Number.isFinite(parsed) ? parsed : null;
}

/**
 * Get the locale string for a given currency
 */
export function getCurrencyLocale(currency: SupportedCurrency = "JPY"): string {
  const localeMap: Record<SupportedCurrency, string> = {
    JPY: "ja-JP",
    USD: "en-US",
    EUR: "de-DE",
  };
  return localeMap[currency] || "en-US";
}