const dateTimeFormatters = new Map<string, Intl.DateTimeFormat>();
const numberFormatters = new Map<string, Intl.NumberFormat>();

export function formatDateTime(value: string | null | undefined, locale: string): string {
  if (!value) {
    return "-";
  }
  const date = new Date(value);
  if (Number.isNaN(date.getTime())) {
    return "-";
  }
  let formatter = dateTimeFormatters.get(locale);
  if (!formatter) {
    formatter = new Intl.DateTimeFormat(locale, {
      dateStyle: "medium",
      timeStyle: "short",
    });
    dateTimeFormatters.set(locale, formatter);
  }
  return formatter.format(date);
}

export function formatNumber(value: number, locale: string, maximumFractionDigits = 2): string {
  const key = `${locale}:${maximumFractionDigits}`;
  let formatter = numberFormatters.get(key);
  if (!formatter) {
    formatter = new Intl.NumberFormat(locale, { maximumFractionDigits });
    numberFormatters.set(key, formatter);
  }
  return formatter.format(value);
}

export function formatDuration(milliseconds: number): string {
  if (milliseconds < 1000) {
    return `${milliseconds} ms`;
  }
  return `${(milliseconds / 1000).toFixed(milliseconds < 10000 ? 2 : 1)} s`;
}

export function toDateTimeLocal(value: string | null | undefined): string {
  if (!value) {
    return "";
  }
  const date = new Date(value);
  const offset = date.getTimezoneOffset() * 60_000;
  return new Date(date.getTime() - offset).toISOString().slice(0, 19);
}