import { Document, Model } from 'mongoose';
/**
 * DocumentMerger
 *
 * Provides a utility to merge references within documents of a MongoDB collection by replacing
 * all occurrences of an old identifier with a new identifier in specified fields.
 *
 * This class handles both single string references and arrays of references,
 * ensuring unique values after the merge.
 *
 * @template T - Type of Mongoose Document
 * @template Field - Keys of T excluding standard Document properties, representing the fields to update
 */
export declare class DocumentMerger<T extends Document, Field extends keyof Omit<T, keyof Document>> {
    private readonly logger;
    private readonly model;
    private readonly oldId;
    private readonly newId;
    private readonly fields;
    /**
     * Initializes the DocumentMerger with the collection model, IDs to merge, and target fields.
     *
     * @param model - Mongoose model representing the target collection
     * @param oldId - Identifier to be replaced in documents
     * @param newId - Identifier to replace oldId with
     * @param fields - List of document fields where replacements should occur
     */
    constructor(model: Model<T>, oldId: string, newId: string, ...fields: Field[]);
    /**
     * Executes the merge operation over all documents in the collection.
     *
     * Iterates asynchronously through each document using a cursor to avoid loading all documents at once.
     * For each document:
     *  - Optionally applies a transformation function before merging.
     *  - Replaces occurrences of oldId with newId in each specified field.
     *    - If the field is a string matching oldId, it is replaced directly.
     *    - If the field is an array, each occurrence of oldId is replaced with newId,
     *      and duplicates are removed to maintain uniqueness.
     *  - Saves the updated document without modifying timestamp fields.
     *
     * This approach ensures memory efficiency and consistency during the merge process.
     *
     * @param transform - Optional callback to modify each document before merging fields
     * @returns Promise resolving when all documents have been processed and saved
     */
    merge(transform?: (item: Omit<T, keyof Document>) => Omit<T, keyof Document>): Promise<void>;
}