/// <reference types="node" />
import { Stream } from 'node:stream';
import { MiddlewareResult } from './middleware.js';
/**
 * Represents a triple (stream, metadata, metadataChanged) containing the results of middleware evaluation.
 */
export interface TransformResult<S extends Stream> {
    readonly stream: S;
    readonly metadata: object;
    readonly metadataChanged: boolean;
}
/**
 * Represents a triple (stream, metadata, metadataChanged) that can be updated
 * with middleware results.
 */
export declare class MiddlewareTransformable<S extends Stream> implements TransformResult<S> {
    stream: S;
    metadata: object;
    metadataChanged: boolean;
    constructor(stream: S, metadata: object);
    /**
     * Update this object with the results from a middleware.
     *
     * If the results contain a reference to metadata, the metadataChanged
     * attribute will be set to true.
     *
     * @param result The results.
     */
    update(result?: MiddlewareResult<S>): void;
}