/**
 * Mediator Pattern Interfaces.
 *
 * The Mediator pattern provides a single entry point for all requests.
 * Each request type maps to exactly one handler.
 *
 * This is different from events (fire-and-forget, multiple subscribers).
 * Requests are "do something and return a result" (single handler, response required).
 */
/**
 * Marker interface for requests.
 * The generic parameter TResponse indicates what the handler returns.
 *
 * @example
 * class GetUserRequest implements IRequest<User> {
 *   constructor(public readonly userId: string) {}
 * }
 */
export interface IRequest<TResponse = void> {
    /**
     * Phantom type to carry the response type.
     * Not used at runtime, only for type inference.
     */
    readonly __responseType?: TResponse;
}
/**
 * Handler for a specific request type.
 *
 * @example
 * class GetUserHandler implements IRequestHandler<GetUserRequest, User> {
 *   async handle(request: GetUserRequest): Promise<User> {
 *     return this.userRepository.findById(request.userId);
 *   }
 * }
 */
export interface IRequestHandler<TRequest extends IRequest<TResponse>, TResponse> {
    /**
     * Handle the request and return a response.
     */
    handle(request: TRequest): Promise<TResponse>;
}
/**
 * Request type constructor.
 * Used for registering handlers by request class.
 */
export interface IRequestType<TRequest extends IRequest<TResponse>, TResponse = unknown> {
    new (...args: any[]): TRequest;
}
/**
 * Mediator interface.
 * Routes requests to their registered handlers.
 */
export interface IMediator {
    /**
     * Send a request to its handler and return the response.
     *
     * @param request - The request to handle
     * @returns The handler's response
     * @throws Error if no handler is registered for the request type
     *
     * @example
     * const user = await mediator.send(new GetUserRequest('123'));
     */
    send<TResponse>(request: IRequest<TResponse>): Promise<TResponse>;
    /**
     * Register a handler for a request type.
     *
     * @param requestType - The request class constructor
     * @param handler - The handler instance
     */
    register<TRequest extends IRequest<TResponse>, TResponse>(requestType: IRequestType<TRequest, TResponse>, handler: IRequestHandler<TRequest, TResponse>): void;
}
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