/**
 * Catalog merging for message extraction.
 * @module bquery/i18n
 */
import { type ExtractedCatalog, type ExtractedMessage } from './extract';
/** Outcome of merging freshly extracted messages into an existing catalog. */
export type MergeResult = {
    /** The merged, nested catalog. */
    catalog: ExtractedCatalog;
    /** Keys newly introduced by this extraction run. */
    added: string[];
    /** Keys present before but no longer found in source (only when `prune`). */
    removed: string[];
    /** Count of existing translations preserved untouched. */
    kept: number;
};
/** Options for {@link mergeCatalog}. */
export type MergeOptions = {
    /**
     * Drop keys that exist in `existing` but are no longer found in source.
     * Default `false` — stale keys are preserved so translations are never lost
     * by accident. Pass `true` for a strict prune.
     */
    prune?: boolean;
};
/**
 * Merges extracted messages into an existing catalog without clobbering
 * already-translated values.
 *
 * - **New keys** are added with their extracted default (the `defineMessages`
 *   source string, or `''` for keys seen only in `t()` calls).
 * - **Existing keys** keep their current value — translations are never
 *   overwritten.
 * - **Stale keys** are preserved unless `prune` is set.
 *
 * @param existing - The current catalog (e.g. parsed from `locales/en.json`)
 * @param extracted - Flat messages from {@link extractFromSource}
 * @param options - Merge behaviour
 * @returns The merged catalog plus a diff summary
 */
export declare const mergeCatalog: (existing: ExtractedCatalog, extracted: ExtractedMessage[], options?: MergeOptions) => MergeResult;
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