import * as Router from 'koa-router';
/**
 * A IF middleware that helps a branch checking.  Usage:
 *
 *     @If(predictor, ifClause)
 *     - execute ifClause when predictor returns true.
 *     - execute next middleware when predictor returns false.
 *
 *     @If(predictor, ifClause, elseClause)
 *     - execute ifClause when predictor returns true.
 *     - execute elseClause when predictor returns false.
 *
 * @param predictor - Predict which clause to execute.
 * @param ifClause - Execute when predictor returns true.
 * @param elseClause - Execute when predictor returns false. By default, execute
 *                     else clause.
 */
export declare function If(predictor: (ctx: Router.IRouterContext) => boolean | Promise<boolean>, ifClause: Router.IMiddleware | Router.IMiddleware[], elseClause?: Router.IMiddleware | Router.IMiddleware[]): ClassDecorator & PropertyDecorator & MethodDecorator;
export declare function _if(predictor: (ctx: Router.IRouterContext) => boolean | Promise<boolean>, ifClause: Router.IMiddleware | Router.IMiddleware[], elseClause?: Router.IMiddleware | Router.IMiddleware[]): (ctx: Router.IRouterContext, next: () => any) => Promise<void>;
/**
 * A WHEN middleware that helps a branch checking, next middleware will always
 * be executed regardless what predictor returns.
 *
 * @param predictor - Predict when the when clause will be executed.
 * @param whenClause - Execute when predictor returns true.
 */
export declare function When(predictor: (ctx: Router.IRouterContext) => boolean | Promise<boolean>, whenClause: Router.IMiddleware | Router.IMiddleware[]): ClassDecorator & PropertyDecorator & MethodDecorator;
export declare function _when(predictor: (ctx: Router.IRouterContext) => boolean | Promise<boolean>, whenClause: Router.IMiddleware | Router.IMiddleware[]): (ctx: Router.IRouterContext, next: () => any) => Promise<void>;
/**
 * A CHECK middleware that helps determines if to execute next middleware.
 * Usage:
 *
 *   @Check((ctx: Router.IRouterContext) => ctx.isAuthenticated())
 *
 * @param predictor - Returns true to execute next middleware.
 */
export declare function Check(predictor: (ctx: Router.IRouterContext) => boolean | Promise<boolean>): ClassDecorator & PropertyDecorator & MethodDecorator;
export declare function _check(predictor: (ctx: Router.IRouterContext) => boolean | Promise<boolean>): (ctx: Router.IRouterContext, next: () => any) => Promise<void>;
/**
 * A Tee middleware that helps execute a side function.
 * Usage:
 *
 *   @Tee((ctx) => console.log(ctx.path))
 *
 * @param fn - The side function to execute.
 * @param opts.post - specifies run tee after returned.
 */
export declare function Tee<T extends Router.IRouterContext>(fn: (ctx: T, next: () => any) => void | Promise<void>, opts?: TeeOptions): ClassDecorator & PropertyDecorator & MethodDecorator;
export declare function TeePost<T extends Router.IRouterContext>(fn: (ctx: T, next: () => any) => void | Promise<void>): ClassDecorator & PropertyDecorator & MethodDecorator;
export interface TeeOptions {
    post?: boolean;
}