import { FontBytesByVariant } from '../font/index.js';
/** A curated open substitute family (the Croscore + Carlito/Caladea set, like LibreOffice). */
export type FamilyKey = 'arimo' | 'tinos' | 'cousine' | 'carlito' | 'caladea';
/**
 * A WRITING SYSTEM the curated five cannot draw at all. They are Latin families
 * — Greek, Cyrillic and Hebrew ride along, everything else is a notdef box —
 * and 2145 characters of the corpus fall outside them: Han, Kana, Hangul,
 * Arabic, the geometric symbols a form's checkbox is made of.
 *
 * These are fetched only when a document actually holds such a character, and
 * only in the regular weight: Noto Sans SC is ten megabytes, and a bold run in
 * it is better stroked (see `SyntheticFace`) than downloaded four times over.
 */
export type ScriptKey = 'jp' | 'kr' | 'sc' | 'arabic' | 'hebrew' | 'thai' | 'symbols1' | 'symbols2';
/** Either kind of substitute — a Latin family or a per-script face. */
export type SubstituteKey = FamilyKey | ScriptKey;
/** Whether a substitute key names a writing system rather than a Latin family. */
export declare function isScriptKey(key: SubstituteKey): key is ScriptKey;
/**
 * Fetch the ONE face a writing system is drawn with.
 *
 * @param script The writing system.
 * @param fetchImpl Injectable `fetch` (defaults to the global one).
 * @returns The regular face, or `undefined` when the download fails.
 */
export declare function fetchScriptFont(script: ScriptKey, fetchImpl?: FetchLike): Promise<FontBytesByVariant | undefined>;
/** A family name, read: which substitute it maps to and what it says about the face. */
export interface FamilyStyle {
    readonly key: FamilyKey;
    /** The NAME asks for a heavy face (`Arial Black`, `DIN-Bold`). */
    readonly bold?: boolean;
    /** …or a slanted one (`Frutiger Oblique`). */
    readonly italic?: boolean;
    /**
     * …or a narrow one (`Arial Narrow`), as the fraction of the normal advance it
     * sets at. No curated family ships a condensed cut, so the substitute is
     * squeezed instead — Arial Narrow's own widths are 82 % of Arial's, which is
     * also what LibreOffice's Liberation Sans Narrow reproduces.
     */
    readonly widthScale?: number;
}
/**
 * Map a document-referenced font family to a curated open substitute: an exact
 * metric twin when one is known (e.g. Calibri → Carlito), otherwise a
 * serif/mono/sans style fallback.
 *
 * The name may also carry the FACE — `Times New Roman Bold` is the Times
 * family, and read whole it matches no twin at all and fell through to the
 * generic sans, which is how a Times heading came out in a grotesque.
 *
 * @param name The referenced family name (case-insensitive); empty ⇒ Arimo.
 * @returns The chosen family and what the name said about the face.
 */
export declare function resolveFamilyStyle(name: string | undefined): FamilyStyle;
/**
 * The curated substitute for a family name — {@link resolveFamilyStyle} without
 * the face it also carries.
 *
 * @param name The referenced family name (case-insensitive); empty ⇒ Arimo.
 * @returns The chosen {@link FamilyKey}.
 */
export declare function resolveFamilyKey(name: string | undefined): FamilyKey;
/** A minimal `fetch`-like function (injectable for tests / offline use). */
export type FetchLike = (url: string) => Promise<{
    ok: boolean;
    arrayBuffer: () => Promise<ArrayBuffer>;
}>;
/** Options for {@link fetchFontSet}. */
export interface FetchFontSetOptions {
    /** Document font family name to substitute, or a curated {@link FamilyKey} directly. */
    readonly family?: string | FamilyKey;
    /** Injectable fetch (defaults to the global `fetch`); lets tests run offline. */
    readonly fetch?: FetchLike;
}
/**
 * Download a full variant set (regular required; bold/italic/bold-italic
 * best-effort) for the open family that best matches the requested name.
 *
 * @param options The family to substitute and an optional fetch override.
 * @returns The downloaded font bytes per variant.
 * @throws Error when the required regular face cannot be downloaded.
 */
export declare function fetchFontSet(options?: FetchFontSetOptions): Promise<FontBytesByVariant>;
/** Test / diagnostic helper: clear the in-memory font-download cache. */
export declare function clearFontCache(): void;