import DBDownload from "../database/entities/db-download";
import { DBPost } from "../database/db";
import DBUrl from "../database/entities/db-url";
import Downloader from "./downloader";
import { DownloaderState, DownloadProgress } from "../util/state";
export declare function getDownloaders(): Promise<Downloader[]>;
/**
 * Find the next DBDownload that needs a URL processed, which is not already inside the given array.
 *
 * This is a mutex, and can only be invoked with one concurrent lookup.
 */
export declare const getNextPendingDownload: (ignoreURLs: Set<string>) => Promise<Promise<DBDownload | undefined>>;
/**
 * Run the downloading process for all unhandled DBUrls, and any that are saved live.
 */
export declare function downloadAll(state: DownloaderState): Promise<number>;
export interface DownloaderData {
    /** The relative path of this file. Not as useful for Downloaders. */
    relativeFile: string;
    /** The target output file's absolute path */
    file: string;
    /** The target URL, unpacked from dl.url.address for simplicity */
    url: string;
    /** The Post providing this URL */
    post: DBPost;
    /** The DBDownload object providing this URL. */
    dl: DBDownload;
}
export interface DownloaderFunctions {
    /** Register a new URL, and sets the current URL as an album parent. Noop for nested albums. */
    addAlbum: (url: string) => Promise<DBDownload | null>;
    /** Mark the current URL as failed, and add a reason. The URL will be skipped by default after this. */
    markInvalid: (reason: string) => Promise<DBUrl>;
    /** gracefully exit in a way that will be swallowed by the parent error handling. */
    userExit: (reason?: string) => void;
}
/**
 * Generate the data structure and callbacks that are to be passed into the Downloader instances.
 */
export declare function buildDownloadData(dl: DBDownload): Promise<{
    data: DownloaderData;
    callbacks: DownloaderFunctions;
}>;
/**
 * Iterate through all available downloaders, attempting to handle the given DBDownload.
 */
export declare function handleDownload(dl: DBDownload, progress: DownloadProgress): Promise<DBUrl | undefined>;
/**
 * Builds and saves a new DBFile for the given DBUrl and file path.
 */
export declare function processFinishedDownload(url: DBUrl, subPath: string, handler: string): Promise<DBUrl>;