import { PackageInfo } from "./PackageInfo";
import { PackageSource } from "./PackageSource";
/**
 * A combined prioritized view over multiple package sources.
 */
export declare class PackageSourceUnion extends PackageSource {
    readonly sources: PackageSource[];
    /**
     * Creates a union view over multiple package sources.
     *
     * @param {IPackageSource[]} sources  Array of package sources in priority order.
     */
    constructor(sources: PackageSource[]);
    /**
     * Gets information about all OpenT2T packages currently available from the source.
     * This method is optional; it may not be implemented for remote sources.
     * CAUTION: This is a potentially slow operation.
     *
     * @returns {Promise<PackageInfo[]>} An array of package information
     * objects, or an empty array if the cache is empty
     */
    getAllPackageInfoAsync(): Promise<PackageInfo[]>;
    /**
     * Gets information about an OpenT2T package from the source
     * (potentially without downloading the whole package).
     *
     * @param {string} name  Name of the package
     * @returns {(Promise<PackageInfo | null)} Information about the requested
     * package, or null if the requested package is not found at the source
     */
    getPackageInfoAsync(name: string): Promise<PackageInfo | null>;
    /**
     * Downloads or copies a package to a target (cache) directory.
     *
     * @param {string} name  Name of the package
     * @param {string} targetDirectory  Directory where the package is to be extracted
     */
    copyPackageAsync(name: string, targetDirectory: string): Promise<void>;
}