import type { IStorage, SubtitleTrack } from '@nomercy-entertainment/nomercy-player-core';
/** Recorded when the viewer turns subtitles off, so a later item stays off. */
export declare const SUBTITLES_OFF = "off";
/**
 * The viewer's last chosen audio and subtitle language, carried from one item
 * to the next.
 *
 * A choice is a language, never a track index: an index means a different
 * language on every file, and the master playlist's own DEFAULT flag follows
 * the source's stream order, so neither survives an episode change. Remembering
 * the language is what makes the next episode open in the language the viewer
 * picked, whatever the encode declared.
 *
 * A caption choice is more than a language. A viewer who picked English SDH and
 * got plain English back was handed a different track under the same name, and
 * two renditions of the same language and variant can differ only by container
 * — an `.ass` carries the show's own styling where a `.vtt` does not. So the
 * variant and the format travel with the language.
 */
export declare class TrackLanguageMemory {
    private readonly storage?;
    private audio;
    private subtitle;
    constructor(storage?: IStorage | undefined);
    audioLanguage(): string | null;
    /** The caption choice, or `null` when the viewer has never made one. */
    subtitleChoice(): SubtitleChoice | null;
    rememberAudio(language: string | null | undefined): void;
    /** Pass `SUBTITLES_OFF` for a deliberate off; `undefined` is not a choice. */
    rememberSubtitle(choice: SubtitleTrack | typeof SUBTITLES_OFF | null | undefined): void;
    private read;
    private write;
}
/** A caption choice: a deliberate off, or the language / variant / format picked. */
export type SubtitleChoice = typeof SUBTITLES_OFF | SubtitleDescriptor;
export interface SubtitleDescriptor {
    language: string;
    type?: string;
    format?: string;
}
/** The file's format, taken from its URL — the manifest does not carry one. */
export declare function formatOf(track: Pick<SubtitleTrack, 'url'>): string | undefined;
/**
 * The track that answers a caption choice, narrowest match first.
 *
 * A list filtered by device capability can drop the exact variant, and a viewer
 * is better served by the same language in a different flavour than by no
 * captions at all. Position is never consulted: it means a different track on
 * every file. The language step is passed in because the player owns the
 * prefix rules (`en` answering `en-US`).
 */
export declare function matchSubtitleTrack(tracks: ReadonlyArray<SubtitleTrack>, wanted: SubtitleDescriptor, matchLanguage: (languages: Array<string | undefined>, wantedLanguage: string) => number): number;