/**
 * Shared helper utilities for Zod schema preprocessing.
 *
 * @module udp-schema/helpers
 */
import { z } from 'zod';
/**
 * Converts empty / whitespace-only strings to `undefined`
 * so Zod `.optional()` treats them as "not provided".
 */
export declare const emptyStringToUndefined: (value: unknown) => unknown;
/**
 * Optional trimmed string with 100-char max.
 * Empty strings are coerced to `undefined`.
 */
export declare const optionalTrimmedString: z.ZodPreprocess<z.ZodOptional<z.ZodString>>;
/**
 * Optional 4-digit year (1900–2099).
 * Empty strings and undefined are treated as "not provided".
 * Accepts strings like "2020". Rejects non-digits and out-of-range values.
 *
 * Uses superRefine (not preprocess) to keep input type as `string | undefined`
 * for full react-hook-form compatibility.
 */
export declare const optionalYearSchema: z.ZodOptional<z.ZodString>;
/**
 * Optional phone number — digits only, 7–15 characters.
 * Accepts an optional leading + for country code (e.g. +919876543210).
 * Empty strings and undefined are treated as "not provided".
 *
 * Uses superRefine (not preprocess) to keep input type as `string | undefined`
 * for full react-hook-form compatibility.
 */
export declare const optionalPhoneSchema: z.ZodOptional<z.ZodString>;
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