/**
 * Type guards, error helpers, and argument validators for the plugin.
 */
/**
 * Type guard to check if a value is defined (not null or undefined)
 * @param value - Value to check
 * @returns True if value is not null or undefined
 */
export declare function isDefined<T>(value: T | null | undefined): value is T;
/**
 * Type guard to check if a value is a non-empty string
 * @param value - Value to check
 * @returns True if value is a string with at least one non-whitespace character
 */
export declare function isNonEmptyString(value: unknown): value is string;
/**
 * Coerce a finite numeric frontmatter value to its string form, mirroring how
 * Docusaurus (Joi `convert`) treats numeric `slug`/`id`/`title`. YAML parses an
 * unquoted `slug: 2025` as the number 2025, which would otherwise fail the
 * string guards and lose the numeric route.
 * @param value - Raw frontmatter value
 * @returns The value as a string when it is a finite number, otherwise unchanged
 */
export declare function coerceFrontMatterString(value: unknown): unknown;
/**
 * Type guard to check if a value is a non-empty array
 * @param value - Value to check
 * @returns True if value is an array with at least one element
 */
export declare function isNonEmptyArray<T>(value: unknown): value is T[];
/**
 * Safely extract an error message from an unknown error value
 * @param error - The error value (can be Error, string, or any other type)
 * @returns A string representation of the error
 */
export declare function getErrorMessage(error: unknown): string;
/**
 * Extract stack trace from unknown error types
 * @param error - The error value (can be Error or any other type)
 * @returns Stack trace if available, undefined otherwise
 */
export declare function getErrorStack(error: unknown): string | undefined;
/**
 * Custom error class for validation errors
 */
export declare class ValidationError extends Error {
    constructor(message: string);
}
/**
 * Validates that a value is not null or undefined
 * @param value - The value to validate
 * @param paramName - The parameter name for error messages
 * @returns The validated value
 * @throws ValidationError if the value is null or undefined
 */
export declare function validateRequired<T>(value: T | null | undefined, paramName: string): T;
/**
 * Validates that a value is a string and optionally checks its properties
 * @param value - The value to validate
 * @param paramName - The parameter name for error messages
 * @param options - Validation options for min/max length and pattern
 * @returns The validated string
 * @throws ValidationError if validation fails
 */
export declare function validateString(value: unknown, paramName: string, options?: {
    minLength?: number;
    maxLength?: number;
    pattern?: RegExp;
}): string;
/**
 * Validates that a value is an array and optionally validates elements
 * @param value - The value to validate
 * @param paramName - The parameter name for error messages
 * @param elementValidator - Optional function to validate each element
 * @returns The validated array
 * @throws ValidationError if validation fails
 */
export declare function validateArray<T>(value: unknown, paramName: string, elementValidator?: (item: unknown) => boolean): T[];