/// <reference types="@types/node" />
import { Writable } from "stream";
export interface IStreamCache<R, K> extends Iterable<ICacheItem<K>> {
    expire(key: K): Promise<boolean>;
    get(req: R): Promise<K>;
}
export interface IStreamCacheOptions<R, K> {
    keyExtractor: KeyExtractor<R, K>;
    streamExtractor: StreamExtractor<R>;
    cacheBackend: IStreamCacheBackend<K>;
    producer: StreamProducer<R>;
}
export interface ICacheItem<K> {
    readonly key: K;
    readonly lastAccess: Date;
    readonly size: number;
}
export declare type StreamProducer<R> = (req: R, stream: Writable) => void;
export declare type KeyExtractor<R, K> = (req: R) => K;
export declare type StreamExtractor<R> = (req: R) => Writable;
export interface IStreamCacheBackend<K> extends Iterable<ICacheItem<K>> {
    putStreaming(key: K): Promise<Writable>;
    getSteaming(key: K, output: Writable): Promise<boolean>;
    expunge(key: K): Promise<boolean>;
}
export declare function cache<R, K>(options: IStreamCacheOptions<R, K>): IStreamCache<R, K>;