import type { ErrorContext } from './types';
/** A locale catalog maps `code` → message template (with `{{var}}`). */
export type MessageCatalog = Record<string, string>;
/**
 * Locale to use when `format` is called without one. This is a plain fallback
 * label, not a special catalog: the untagged default copy lives in the registry
 * itself, so there is no built-in `'en'` catalog to keep in sync.
 */
export declare const DEFAULT_LOCALE = "en";
/**
 * Register or extend a locale catalog. Merges with any existing entries for
 * that locale (new entries win), so hosts can override individual codes — pass
 * the default locale to override the base copy.
 */
export declare function registerCatalog(locale: string, catalog: MessageCatalog): void;
/**
 * Render a localized message for a code.
 *
 * Resolution order:
 * 1. requested-locale overlay entry (template) → interpolate
 * 2. registry default message (template → interpolate, or function → call)
 * 3. humanized code
 */
export declare function format(code: string, context?: ErrorContext, locale?: string): string;