import { Db } from 'mongodb';
import { DocumentNode } from 'graphql';
import { GraphQLExecutionResult } from './mongo-queries';
/**
 * Function that formats errors off of {GraphQLExecutionResult}s.
 */
export declare type ErrorFormatter = (result: GraphQLExecutionResult, includeStack?: boolean) => any;
/**
 * Options to change the behavior of the GraphQL mongo client.
 */
export interface GraphQLMongoClientOptions {
    /**
     * Whitelist of collections that can be queried. If provided, an error will be thrown any time an attempt is
     * made to query a collection not in the whitelist.
     */
    whitelist?: string[];
    /**
     * If true, will include stack trace in error results. Defaults to false.
     */
    includeStack?: boolean;
    /**
     * Function to format error objects. Defaults to the following format:
     * {
     *   collection: string;
     *   message: string;
     *   stack?: string[]; // if includeStack === true
     * }
     */
    formatError?: ErrorFormatter;
    /**
     * If no limit clause is passed, this default limit will be used. This is to prevent
     * someone accidentally pulling in thousands or millions of mongo documents by mistake.
     * Defaults to 100 if not passed.
     */
    defaultLimit?: number;
    /**
     * The maximum limit accepted for a graphql request. If a limit is encountered above this
     * an error will be thrown. Defaults to 10000.
     */
    maxLimit?: number;
}
/**
 * Results from a graphql query. Will contain the {data} element which will have results
 * for every collection-based query that succeeded as well as an {errors} array that will contain
 * any errors that occurred.
 */
export interface QueryResult {
    /**
     * The data that was retrieved. Will have an entry per collection queried under that collection's name.
     *
     * @example
     * If you query for the following:
     *
     * {
     *   users {
     *     name
     *   }
     *   places {
     *     lat
     *     lng
     *   }
     * }
     *
     * Your response will be:
     * {
     *   data: {
     *     users: [ ...users results here ],
     *     places: [ ...places results here ],
     *   }
     * }
     */
    data: {
        [collection: string]: any;
    };
    /**
     * Errors that occurred during the process (if any).
     */
    errors?: any[];
    /**
     * Metadata about each collection query such as the limit applied and offset.
     */
    _meta?: {
        [collection: string]: {
            limit?: number;
            offset?: number;
        };
    };
}
/**
 * A mongo client that wraps the standard node MongoDB driver with
 * an API that allows for making queries using GraphQL.
 */
export declare class MongoGraphQLClient {
    private readonly connection;
    private readonly whitelist;
    private readonly includeStack;
    private readonly errorFormatter;
    private readonly defaultLimit;
    private readonly maxLimit;
    /**
     * Create a new {MongoGraphQLClient}.
     * @param connection The DB connection.
     * @param options Options to change the behavior of the client.
     */
    constructor(connection: Db, options?: GraphQLMongoClientOptions);
    /**
     * Gets the options that this client was configured with.
     */
    getOptions(): {
        database: string;
        whitelist: string[];
        includeStack: boolean;
        errorFormatter: ErrorFormatter;
        defaultLimit: number;
        maxLimit: number;
    };
    /**
     * Performs a MongoDB find operation for every collection specified in the passed
     * GraphQL query and returns the results and any errors as a promise.
     *
     * @param query The query to perform.
     * @param variables Variables to use in the query.
     * @return {Promise<QueryResult>} The result of the queries.
     */
    find(query: DocumentNode | string, variables?: object): Promise<QueryResult>;
    /**
     * Performs a MongoDB findOne operation for exactly one collection and returns
     * just a single document for that collection. Will throw an error if multiple
     * collections are included in the query.
     *
     * @param query The query to perform,.
     * @param variables Variables to use in the query.
     * @return {Promise<QueryResult>}
     */
    findOne(query: DocumentNode | string, variables?: object): Promise<QueryResult>;
}
/**
 * Default error formatter
 * @param result The result of the query.
 * @param includeStack If true, signifies that stack should be printed.
 */
export declare function defaultErrorFormatter(result: GraphQLExecutionResult, includeStack: boolean): {
    collection: string;
    message: string | Error;
    stack: string[];
};