import { CustomValidator } from '../base';
import { Optional } from '../context';
import { ValidationChain } from './validation-chain';
export interface ContextHandler<Chain> {
    /**
     * Stops running validations if any of the previous ones have failed.
     *
     * Useful to prevent a custom validator that touches a database or external API from running when
     * you know it will fail.
     *
     * May be used multiple times in the same validation chain if desired.
     *
     * @example
     *  check('username')
     *    .isEmail()
     *    // If not an email, stop here
     *    .bail()
     *    .custom(checkDenylistDomain)
     *    // If domain is not allowed, don't go check if it already exists
     *    .bail()
     *    .custom(checkEmailExists)
     *
     * @returns the current validation chain
     */
    bail(): Chain;
    /**
     * Adds a condition on whether the validation should continue on a field or not.
     * @param condition may be either
     *  - a custom validator-like function, which must truthy or a promise that resolves to continue
     *    validation. If the return value is falsy, a promise that rejects, or if it throws, validation
     *    will stop.
     * - a validation chain which if it would produce errors, the validation chain stops.
     * @example
     *  check('newPassword')
     *    // Only validate if the old password has been provided
     *    .if((value, { req }) => req.body.oldPassword)
     *    // Or, use it with a a validation chain
     *    .if(body('oldPassword').notEmpty())
     * @returns the current validation chain
     */
    if(condition: CustomValidator | ValidationChain): Chain;
    /**
     * Marks the field(s) of the validation chain as optional.
     * By default, only fields with an `undefined` value are considered optional and will be ignored
     * when validating.
     *
     * @param options an object of options to customize the behavior of optional.
     * @returns the current validation chain
     */
    optional(options?: Partial<Optional> | true): Chain;
}