import { ControlInput } from './ControlInput';
/**
 * State validation function
 *
 * Takes a Control state object and returns `true` if the state passes validation.  If
 * validation fails, a `ValidationResult` object is returned instead.
 */
export declare type StateValidationFunction<TState> = (state: TState, input: ControlInput) => true | ValidationFailure | Promise<true | ValidationFailure>;
/**
 * Describes a validation failure.
 *
 * Usage:
 * - A reason code should be provided that uniquely describes the kind of validation
 *   failure.  A reason code is useful for context-specific rendering and other business
 *   function.   It is not mandatory as for some simple cases it may be duplicative to
 *   provide both a reason code and a single rendering of that reason code.
 *
 * - A rendered reason for situations where the rendered form is not context-sensitive and
 *   can be conveniently provided when the ValidationFailure is instantiated.
 */
export declare type ValidationFailure = {
    /**
     * A code representing what validation failed.
     *
     * Usage:
     *  - use reasonCode for business logic and transform to a prompt during the rendering
     *    phase.
     */
    reasonCode?: string;
    /**
     * A rendered prompt fragment that can be directly included in the `Response`.
     *
     * Usage:
     *  - If convenient, generate the prompt fragment at instantiation time.
     *  - A renderedReason should not be used in logic or further transformed.
     */
    renderedReason?: string;
};
/**
 * Helper to evaluate a prop that accepts one or more StateValidationFunction<TState> functions.
 * @param validationProp - either a single StateValidationFunction<TState> or an array of
 * the same.
 * @param state - The control's state object.
 * @param input - ControlInput.
 */
export declare function evaluateValidationProp<TState>(validationProp: StateValidationFunction<TState> | Array<StateValidationFunction<TState>>, state: TState, input: ControlInput): Promise<true | ValidationFailure>;
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