/**
 * Custom Zod types for Extend-specific field types.
 *
 * These create Zod schemas that will be converted to our extend:type fields.
 */
import { z } from "zod";
import { DATE_TYPE_MARKER, CURRENCY_TYPE_MARKER, SIGNATURE_TYPE_MARKER } from "./types";
/**
 * Creates a date field schema.
 *
 * In the API, this becomes:
 * ```json
 * { "type": ["string", "null"], "extend:type": "date" }
 * ```
 *
 * The output will always be an ISO date string (yyyy-mm-dd) or null.
 *
 * @example
 * ```typescript
 * const schema = extendSchema({
 *   invoice_date: extendDate().describe("The invoice date"),
 * });
 * ```
 */
export declare function extendDate(): z.ZodNullable<z.ZodString> & {
    _extendType: typeof DATE_TYPE_MARKER;
};
/**
 * Creates a currency field schema.
 *
 * In the API, this becomes:
 * ```json
 * {
 *   "type": "object",
 *   "extend:type": "currency",
 *   "properties": {
 *     "amount": { "type": ["number", "null"] },
 *     "iso_4217_currency_code": { "type": ["string", "null"] }
 *   },
 *   "required": ["amount", "iso_4217_currency_code"]
 * }
 * ```
 *
 * @example
 * ```typescript
 * const schema = extendSchema({
 *   total_amount: extendCurrency().describe("Total invoice amount"),
 * });
 * ```
 */
export declare function extendCurrency(): z.ZodObject<{
    amount: z.ZodNullable<z.ZodNumber>;
    iso_4217_currency_code: z.ZodNullable<z.ZodString>;
}> & {
    _extendType: typeof CURRENCY_TYPE_MARKER;
};
/**
 * Creates a signature field schema.
 *
 * In the API, this becomes:
 * ```json
 * {
 *   "type": "object",
 *   "extend:type": "signature",
 *   "properties": {
 *     "printed_name": { "type": ["string", "null"] },
 *     "signature_date": { "type": ["string", "null"], "extend:type": "date" },
 *     "is_signed": { "type": ["boolean", "null"] },
 *     "title_or_role": { "type": ["string", "null"] }
 *   },
 *   "required": ["printed_name", "signature_date", "is_signed", "title_or_role"]
 * }
 * ```
 *
 * @example
 * ```typescript
 * const schema = extendSchema({
 *   customer_signature: extendSignature().describe("Customer's signature"),
 * });
 * ```
 */
export declare function extendSignature(): z.ZodObject<{
    printed_name: z.ZodNullable<z.ZodString>;
    signature_date: z.ZodNullable<z.ZodString>;
    is_signed: z.ZodNullable<z.ZodBoolean>;
    title_or_role: z.ZodNullable<z.ZodString>;
}> & {
    _extendType: typeof SIGNATURE_TYPE_MARKER;
};
/**
 * Type guard to check if a schema has an extend type marker.
 */
export declare function hasExtendType(schema: z.ZodType): schema is z.ZodType & {
    _extendType: symbol;
};
/**
 * Get the extend type marker from a schema, if present.
 */
export declare function getExtendType(schema: z.ZodType): symbol | undefined;