/// <reference types="node" />
import type { Middleware, ParameterizedContext, DefaultState, DefaultContext } from 'koa';
import type { IncomingMessage } from 'http';
import { HandlerOptions as RawHandlerOptions, OperationContext } from '../handler';
/**
 * Handler options when using the koa adapter.
 *
 * @category Server/koa
 */
export type HandlerOptions<Context extends OperationContext = undefined, KoaState = DefaultState, KoaContext = DefaultContext> = RawHandlerOptions<IncomingMessage, ParameterizedContext<KoaState, KoaContext>, Context>;
/**
 * The ready-to-use handler for [Koa](https://expressjs.com).
 *
 * Errors thrown from the provided options or callbacks (or even due to
 * library misuse or potential bugs) will reject the handler or bubble to the
 * returned iterator. They are considered internal errors and you should take care
 * of them accordingly.
 *
 * For production environments, its recommended not to transmit the exact internal
 * error details to the client, but instead report to an error logging tool or simply
 * the console.
 *
 * ```js
 * import Koa from 'koa'; // yarn add koa
 * import mount from 'koa-mount'; // yarn add koa-mount
 * import { createHandler } from 'graphql-sse/lib/use/koa';
 * import { schema } from './my-graphql';
 *
 * const app = new Koa();
 * app.use(
 *   mount('/graphql/stream', async (ctx, next) => {
 *     try {
 *       await handler(ctx, next);
 *     } catch (err) {
 *       console.error(err);
 *       ctx.response.status = 500;
 *       ctx.response.message = 'Internal Server Error';
 *     }
 *   }),
 * );
 *
 * app.listen({ port: 4000 });
 * console.log('Listening to port 4000');
 * ```
 *
 * @category Server/koa
 */
export declare function createHandler<Context extends OperationContext = undefined, KoaState = DefaultState, KoaContext = DefaultContext>(options: HandlerOptions<Context, KoaState, KoaContext>): Middleware<KoaState, KoaContext>;