import { en, type DictKey } from './en';

/** Fixed locale for every Intl call, server and client, so hydration never diverges. */
export const LOCALE = 'en-US' as const;

type Params = Record<string, string | number | null | undefined>;

/**
 * Translate a dictionary key, interpolating `{name}` placeholders.
 * Usage: `t('metric.rankWorld', { rank: '12th', n: 190 })`.
 * Missing keys return the key itself so a typo is visible rather than silent.
 */
export function t(key: DictKey, params?: Params): string {
  const raw: string = en[key] ?? key;
  if (!params) return raw;
  return raw.replace(/\{(\w+)\}/g, (_, k: string) => {
    const v = params[k];
    return v == null ? '' : String(v);
  });
}

/** Optional-key variant for dynamic keys (e.g. `change.kind.${kind}`); returns `fallback` when the key is unknown. */
export function tOpt(key: string, fallback: string, params?: Params): string {
  if (key in en) return t(key as DictKey, params);
  return fallback;
}

export type { DictKey };