import { RouteParams } from '@sigiljs/pathfinder';
import { ClientRequest } from '../../index';
import { $InternalModifierContext, $SigilInternalModifierAPI } from './modifier.types';
/**
 * Request content modifier.
 *
 * Installed on a specific router and can modify
 * the already processed request. The returned value
 * will be merged into the request object.
 *
 * > The modifier will not be invoked if the router
 * > fails to find a registered handler.
 *
 * To ensure correct typing, specify the return type
 * in the subclass definition:
 * ```typescript
 * class MyModifier extends Modifier<{ additionalData: number }> {}
 * ```
 *
 * @template T type of additional data to merge into the request.
 * @template Path route path string type (e.g., "/users/:id").
 */
export declare abstract class Modifier<T = any, Path extends string = string> {
    protected readonly sigil: $SigilInternalModifierAPI | undefined;
    protected readonly logger: $InternalModifierContext["logger"];
    /**
     * Creates a new Modifier instance. No parameters.
     */
    protected constructor();
    /**
     * Lifecycle method called just before the request is passed
     * to the registered handler.
     *
     * @param request client request object already processed by the framework.
     * @returns additional data to merge into the request,
     * matching the type specified in the subclass.
     */
    abstract onRequest(request: ClientRequest<RouteParams<Path>>): T | Promise<T>;
}
type PayloadOfConstructor<C> = C extends ModifierConstructor<infer Out, any> ? Awaited<Out> : never;
/**
 * Converts a union of types to their intersection.
 * Used to merge payload types from multiple modifiers.
 * @template U union of types.
 */
type UnionToIntersection<U> = (U extends any ? (x: U) => 0 : never) extends (x: infer I) => 0 ? I : never;
/**
 * Utility type to merge payloads of all modifiers in an array.
 * @template Arr array of modifier constructors.
 */
export type MergePayloads<Arr extends readonly ModifierConstructor<any, any>[]> = UnionToIntersection<PayloadOfConstructor<Arr[number]>>;
/**
 * Constructor type for a Modifier subclass.
 * @template Out return type of onRequest.
 * @template P route path type.
 */
export type ModifierConstructor<Out, P extends string = string> = new () => Modifier<Out, P>;
export {};