export type MiddlewarePromise<T extends string | undefined = SpecialNextParam> = Promise<MiddlewareResult<T>>;
export type MiddlewareResult<T extends string | undefined = SpecialNextParam> = Error | T | OptionsResponse;
/**
 * Defines a middleware interface that handles context and returns a result.
 * @template T - The context parameters the middleware handles.
 * @template TSpecialNextParam - The special next parameter type.
 */
export interface Middleware<T extends unknown[], TSpecialNextParam extends string | undefined = SpecialNextParam> {
    /**
     * Handles the provided context and returns a middleware result.
     * @param ...context - The context parameters to process.
     * @returns The result of the middleware processing.
     */
    handle(...context: T): MiddlewareResult<TSpecialNextParam>;
}
/**
 * Defines an error middleware interface to handle errors in the context.
 * @template T - The context parameters the middleware handles.
 * @template U - The special next parameter type.
 */
export interface ErrorMiddleware<T extends unknown[], U extends string | undefined = SpecialNextParam> {
    /**
     * Handles an error and the provided context.
     * @param error - The error or options response to handle.
     * @param ...context - The context parameters associated with the error.
     * @returns The result of error handling.
     */
    handleError(error: MiddlewareResult<U>, ...context: T): MiddlewareResult<U>;
}
export interface MiddlewareAsync<T extends unknown[], TSpecialNextParam extends string | undefined = SpecialNextParam> {
    handle(...context: T): Promise<MiddlewareResult<TSpecialNextParam>>;
}
export interface ErrorMiddlewareAsync<T extends unknown[], U extends string | undefined = SpecialNextParam> {
    handleError(error: MiddlewareResult<U>, ...context: T): Promise<MiddlewareResult<U>>;
}
export type AnyAsyncMiddleware<T extends unknown[], TSpecialNextParam extends string | undefined = SpecialNextParam> = MiddlewareAsync<T, TSpecialNextParam> | ErrorMiddlewareAsync<T, TSpecialNextParam>;
export type AnySyncMiddleware<T extends unknown[], TSpecialNextParam extends string | undefined = SpecialNextParam> = Middleware<T, TSpecialNextParam> | ErrorMiddleware<T, TSpecialNextParam>;
export type AnyMiddleware<T extends unknown[], TSpecialNextParam extends string | undefined = SpecialNextParam> = AnyAsyncMiddleware<T, TSpecialNextParam> | AnySyncMiddleware<T, TSpecialNextParam>;
export type OptionsResponse = {
    allow: string[];
};
export type MiddlewareError<T = unknown> = {
    error: T;
};
export type MiddlewareSuccess<T = unknown> = {
    success: T | Promise<T>;
};
export type SpecialNextParam = 'break' | undefined;
export declare const NotHandled: Promise<undefined>;
/**
 * Converts a function into a middleware handler.
 * @template T - The function's argument types.
 * @template U - The special next parameter type.
 * @param fn - The function to convert into a middleware.
 * @returns A middleware handler function.
 */
export declare function toMiddleware<T extends unknown[], U extends string | undefined>(fn: (...args: T) => unknown): Middleware<T, U>['handle'];
export declare function toMiddleware<T extends unknown[], U extends string | undefined>(fn: (...args: T) => Promise<unknown>): MiddlewareAsync<T, U>['handle'];
/**
 * Converts a function into a middleware object.
 * @template T - The function's argument types.
 * @template TSpecialNextParam - The special next parameter type.
 * @param fn - The function to convert into a middleware.
 * @returns A middleware object with appropriate handling methods.
 */
export declare function convertToMiddleware<T extends unknown[], TSpecialNextParam extends string | undefined = SpecialNextParam>(fn: (...args: T) => Promise<unknown>): MiddlewareAsync<T, TSpecialNextParam>;
export declare function convertToMiddleware<T extends unknown[], TSpecialNextParam extends string | undefined = SpecialNextParam, TReturnType = unknown>(fn: (...args: T) => TReturnType): Middleware<T, TSpecialNextParam>;
export declare function convertToMiddleware<T extends unknown[], TSpecialNextParam extends string | undefined = SpecialNextParam, TReturnType = unknown>(fn: (...args: T) => TReturnType): TReturnType extends Promise<unknown> ? MiddlewareAsync<T, TSpecialNextParam> : Middleware<T, TSpecialNextParam>;
/**
 * Converts a function into an error middleware object.
 * @template T - The context argument types.
 * @template TSpecialNextParam - The special next parameter type.
 * @param fn - The function to convert into an error middleware.
 * @returns An error middleware object with error handling capabilities.
 */
export declare function convertToErrorMiddleware<T extends unknown[], TSpecialNextParam extends string | undefined = SpecialNextParam>(fn: (error: Exclude<MiddlewareResult<TSpecialNextParam>, TSpecialNextParam>, ...args: T) => Promise<unknown>): ErrorMiddlewareAsync<T, TSpecialNextParam>;
export declare function convertToErrorMiddleware<T extends unknown[], TSpecialNextParam extends string | undefined = SpecialNextParam>(fn: (error: Exclude<MiddlewareResult<TSpecialNextParam>, TSpecialNextParam>, ...args: T) => unknown): ErrorMiddleware<T, TSpecialNextParam>;
/**
 * Checks if a value represents a middleware error.
 * @template TSpecialNextParam - The special next parameter type.
 * @param x - The value to check.
 * @returns True if the value is a middleware error, false otherwise.
 */
export declare function isMiddlewareError<TSpecialNextParam extends SpecialNextParam = SpecialNextParam>(x: MiddlewareError<MiddlewareResult<TSpecialNextParam>> | MiddlewareSuccess<unknown>): x is MiddlewareError<MiddlewareResult<TSpecialNextParam>>;
/**
 * Checks if a middleware is an error middleware.
 * @template T - The context argument types.
 * @template TSpecialNextParam - The special next parameter type.
 * @param middleware - The middleware to check.
 * @returns True if the middleware handles errors, false otherwise.
 */
export declare function isErrorMiddleware<T extends unknown[], TSpecialNextParam extends string | undefined>(middleware: unknown): middleware is ErrorMiddleware<T, TSpecialNextParam> | ErrorMiddlewareAsync<T, TSpecialNextParam>;
/**
 * Checks if a middleware is a standard (non-error) middleware.
 * @template T - The context argument types.
 * @template TSpecialNextParam - The special next parameter type.
 * @param middleware - The middleware to check.
 * @returns True if the middleware is standard, false otherwise.
 */
export declare function isStandardMiddleware<T extends unknown[], TSpecialNextParam extends string | undefined>(middleware: unknown): middleware is Middleware<T, TSpecialNextParam> | MiddlewareAsync<T, TSpecialNextParam>;
/**
 * Processes a middleware with the provided context.
 * @template X - The expected result type.
 * @template T - The context parameters.
 * @template TSpecialNextParam - The special next parameter type.
 * @param middleware - The middleware to process.
 * @param ...req - The context parameters for processing.
 * @returns The processed result.
 */
export declare function process<X = unknown, T extends unknown[] = unknown[], TSpecialNextParam extends string | undefined = SpecialNextParam>(middleware: Middleware<T, TSpecialNextParam> | MiddlewareAsync<T, TSpecialNextParam>, ...req: T): X;