import type { Handle } from 'mdast-util-to-markdown';
import type { PageFrontmatter } from 'myst-frontmatter';
import type { Root } from 'myst-spec';
import type { VFile } from 'vfile';
import type { NestedKinds, NestedState, Validator } from './types.js';
type Kind = keyof NestedKinds;
export declare function incrementNestedLevel(kind: Kind, state: NestedState, value?: number): void;
export declare function popNestedLevel(kind: Kind, state: NestedState, value?: number): number;
/**
 * Create a mdast-to-markdown handler for all unsupported node types
 *
 * This is then able to log an error rather than throwing.
 */
export declare function unsupportedHandlers(tree: Root, supported: string[], file: VFile): Record<string, Handle>;
/**
 * Run tree validation functions for specified node types
 *
 * This validation is separate from the mdast-to-markdown handlers so it may
 * log errors to vfile. Then, handlers can take into account the validated structure.
 */
export declare function runValidators(tree: Root, validators: Record<string, Validator>, file: VFile): void;
/**
 * Add frontmatter to the beginning of markdown content as yaml
 *
 * If no frontmatter is provided, the markdown content is returned as-is.
 * Frontmatter is not validated, and the only coercion is reducing license to a
 * string rather than structured object.
 */
export declare function addFrontmatter(page: string, frontmatter?: PageFrontmatter): string;
export {};
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