/**
 * Form Validation System
 *
 * Provides a flexible validation system with built-in validators and custom validator support.
 * Validators can be chained using pipe syntax and support both sync and async validation.
 *
 * @example Basic usage
 * ```javascript
 * // Register custom validator
 * Gyos.validator('username', (value) => {
 *   return value.length >= 3 || 'Username must be at least 3 characters';
 * });
 *
 * // Validate with rules
 * const error = await Gyos.validate(value, 'required|email|minLength(5)');
 * if (error) {
 *   console.log(error); // "Invalid email address"
 * }
 * ```
 *
 * @example Async validator
 * ```javascript
 * Gyos.validator('uniqueEmail', async (value) => {
 *   const exists = await checkEmailExists(value);
 *   return !exists || 'Email already taken';
 * });
 * ```
 *
 * @example In component
 * ```javascript
 * Gyos.scope('LoginForm', {
 *   email: '',
 *   emailError: '',
 *
 *   async validateEmail() {
 *     this.emailError = await Gyos.validate(this.email, 'required|email');
 *   }
 * });
 * ```
 */
import { ValidatorFn } from "../types";
export interface ValidationContext {
    field?: string;
    form?: Record<string, any>;
    messages?: Record<string, string>;
}
/**
 * Register a custom validator
 *
 * @param name - Validator name
 * @param fn - Validator function (return true for valid, string for error message)
 *
 * @example
 * ```javascript
 * Gyos.validator('even', (value) => {
 *   return value % 2 === 0 || 'Must be an even number';
 * });
 * ```
 */
export declare function validator(name: string, fn: ValidatorFn): void;
/**
 * Get registered validator by name
 *
 * @param name - Validator name
 * @returns Validator function or undefined
 */
export declare function getValidator(name: string): ValidatorFn | undefined;
/**
 * Get all registered validator names
 *
 * @returns Array of validator names
 *
 * @example
 * ```javascript
 * console.log('Available validators:', Gyos.getValidatorNames());
 * // ['required', 'email', 'minLength', ...]
 * ```
 */
export declare function getValidatorNames(): string[];
/**
 * Validate a value against validation rules
 *
 * Supports custom error messages in two ways:
 * 1. Inline: "required:Custom message|email:Invalid email"
 * 2. Via context: { messages: { required: "Custom message" } }
 *
 * @param value - Value to validate
 * @param rules - Validation rules (pipe-separated: "required|email|minLength(5)")
 * @param context - Optional context with form data and custom messages
 * @returns Error message or null if valid
 *
 * @example Basic validation
 * ```javascript
 * const error = await Gyos.validate('test@', 'required|email');
 * // Returns: "Invalid email address"
 * ```
 *
 * @example Inline custom messages
 * ```javascript
 * const error = await Gyos.validate('', 'required:This field is mandatory|email:Enter valid email');
 * // Returns: "This field is mandatory"
 * ```
 *
 * @example Custom messages via context
 * ```javascript
 * const error = await Gyos.validate('abc', 'required|minLength(5)', {
 *   messages: {
 *     required: 'Please fill this field',
 *     minLength: 'Too short! Need at least 5 characters'
 *   }
 * });
 * // Returns: "Too short! Need at least 5 characters"
 * ```
 *
 * @example With form context
 * ```javascript
 * const error = await Gyos.validate(confirmPw, 'required|same(password)', {
 *   form: { password: 'MyPass123' },
 *   messages: { same: 'Passwords do not match' }
 * });
 * ```
 */
export declare function validate(value: any, rules: string, context?: ValidationContext): Promise<string | null>;
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