import type { CitationEngine } from './types.js';
/**
 * Register the citation engine the builds format citations with (the
 * `postext-citeproc` package registers itself: `import 'postext-citeproc/register'`).
 * Without one, citations print as written and the build warns
 * (`citationsUnavailable`).
 */
export declare function registerCitationEngine(next: CitationEngine | undefined): void;
/** The registered citation engine, if any. */
export declare function citationEngine(): CitationEngine | undefined;
/**
 * How to load the citation engine when a document first needs it — a
 * dynamic import, so a host pays for it only on documents that cite:
 *
 * ```ts
 * setCitationEngineLoader(() => import('postext-citeproc/register'));
 * ```
 *
 * The layout worker calls it before building a document that cites works
 * (see {@link ensureCitationEngine}).
 */
export declare function setCitationEngineLoader(next: (() => Promise<unknown>) | undefined): void;
/** Load the citation engine with the registered loader, once; true when an
 *  engine is registered afterwards. */
export declare function ensureCitationEngine(): Promise<boolean>;
/** Whether a document's markdown may cite works or define references: an
 *  `@`, a `:::references` block or a `references:` front matter field. A
 *  cheap test, before parsing, of whether the engine is worth loading. */
export declare function mayNeedCitations(markdown: string): boolean;
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