import { type MessageParams, type UiMessages } from './i18n.js';
import type { FormDataValues, FormErrors } from './formContext.js';
export type BuiltinRule = 'required' | 'email' | 'url' | `minLength:${number}` | `maxLength:${number}` | `min:${number}` | `max:${number}`;
export type CustomRule<T extends FormDataValues> = (value: unknown, data: T) => string | undefined | null | false;
export type PatternRule = {
    pattern: RegExp;
    message?: string;
};
export type FieldRule<T extends FormDataValues = FormDataValues> = BuiltinRule | PatternRule | CustomRule<T>;
export type FormRules<T extends FormDataValues = FormDataValues> = {
    [K in keyof T]?: FieldRule<T> | FieldRule<T>[];
};
export interface ValidateOptions {
    /** Locale for built-in messages (`es`, `en`, …) */
    locale?: string;
    /** Override validation copy */
    messages?: Partial<UiMessages>;
    /** Translate helper (e.g. `i18n.t`) */
    t?: (key: keyof UiMessages, params?: MessageParams) => string;
}
/**
 * Declarative validation → `FormErrors` for `<Form bind:errors>`.
 *
 * @example
 * ```ts
 * errors = validateForm(data, {
 *   email: ['required', 'email'],
 *   password: ['required', 'minLength:8'],
 *   age: ['min:18']
 * }, { locale: 'es' });
 * ```
 */
export declare function validateForm<T extends FormDataValues>(data: T, rules: FormRules<T>, options?: ValidateOptions): FormErrors;
/** True when `current` differs from `initial` (shallow JSON compare). */
export declare function isFormDirty<T>(current: T, initial: T): boolean;
/** First error message, or `undefined` when valid. */
export declare function firstFormError(errors: FormErrors): string | undefined;