import { DIVEResourceKind } from '../prototype/ResourcePrototype.ts';
import { DIVEResourceLease } from '../lease/ResourceLease.ts';
/**
 * Options of a {@link DIVEResourceCache}.
 */
export type DIVEResourceCacheOptions = {
    /**
     * How many prototypes no lease holds any more are kept for a later draw,
     * the least recently released one freed first. `0` frees them at once.
     */
    keep?: number;
};
/**
 * Resource prototypes by URL, so a URL is loaded and parsed once however
 * many resources use it, independent of any DIVE instance or scene.
 *
 * Prototypes are keyed by the resolved URL, so relative, `./`-prefixed and
 * absolute forms of one file share one. Once its last lease is released, a
 * prototype is kept, up to `keep` of them, and a draw of its URL lends the
 * loaded data again without loading; a prototype pushed out of that list, or
 * released while nothing is kept, is freed and dropped, so the next draw of
 * that URL loads again. A failed load is never kept.
 *
 * @typeParam T - The value, e.g. a texture.
 */
export declare class DIVEResourceCache<T extends object> {
    private _kind;
    private _prototypes;
    /** released prototypes by key, least recently released first */
    private _kept;
    private _keep;
    /**
     * @param _kind - How the data is loaded, lent and freed.
     * @param options - How many released prototypes are kept.
     */
    constructor(_kind: DIVEResourceKind<T>, { keep }?: DIVEResourceCacheOptions);
    /**
     * Draws from the prototype of a URL, making it unless it exists.
     *
     * @param url - The URL.
     * @returns The lease, to be released once it is no longer used.
     */
    draw(url: string): Promise<DIVEResourceLease<T>>;
    /**
     * Frees and drops every kept prototype; prototypes in use stay.
     */
    trim(): void;
    /** keeps a prototype its last lease left, freeing the oldest kept beyond the limit */
    private _idle;
    /** frees a prototype no lease holds and drops it */
    private _free;
    /** drops a prototype, unless a newer one took its key */
    private _drop;
}