import type { MongoClient } from "mongodb";
import { Document } from "../Node.js";
import type { BaseReader } from "./type.js";
/**
 * Read in from MongoDB
 */
export declare class SimpleMongoReader implements BaseReader {
    private client;
    constructor(client: MongoClient);
    /**
     * Flattens an array of strings or string arrays into a single-dimensional array of strings.
     * @param texts - The array of strings or string arrays to flatten.
     * @returns The flattened array of strings.
     */
    private flatten;
    /**
     * Loads data from MongoDB collection
     * @param {string} dbName - The name of the database to load.
     * @param {string} collectionName - The name of the collection to load.
     * @param {string[]} fieldNames - An array of field names to retrieve from each document. Defaults to ["text"].
     * @param {string} separator - The separator to join multiple field values. Defaults to an empty string.
     * @param {Record<string, any>} filterQuery - Specific query, as specified by MongoDB NodeJS documentation.
     * @param {Number} maxDocs - The maximum number of documents to retrieve. Defaults to 0 (retrieve all documents).
     * @param {string[]} metadataNames - An optional array of metadata field names. If specified extracts this information as metadata.
     * @returns {Promise<Document[]>}
     * @throws If a field specified in fieldNames or metadataNames is not found in a MongoDB document.
     */
    loadData(dbName: string, collectionName: string, fieldNames?: string[], separator?: string, filterQuery?: Record<string, any>, maxDocs?: number, metadataNames?: string[]): Promise<Document[]>;
}