import * as Koa from 'koa';
import * as winston from 'winston';
import { DefaultState, ParameterizedContext } from 'koa';
import { HttpRequest } from '@google-cloud/logging';
type LoggerType = winston.Logger;
export interface AnnotatedContextType {
    log: LoggerType;
}
/**
 * Generates a Koa middleware that installs a request-specific logger on
 * the `context` object. It optionally can do HttpRequest timing that can be
 * used for generating request logs. This can be used to integrate with logging
 * libraries such as winston and bunyan.
 *
 * @param projectId Generated traceIds will be associated with this project.
 * @param makeChildLogger A function that generates logger instances that will
 * be installed onto `ctx` as `ctx.log`. The logger should include the trace in
 * each log entry's metadata (associated with the LOGGING_TRACE_KEY property.
 * @param emitRequestLog Optional. A function that will emit a parent request
 * log. While some environments like GAE and GCF emit parent request logs
 * automatically, other environments do not. When provided this function will be
 * called with a populated `HttpRequest` which can be emitted as
 * request log.
 */
export declare function makeMiddleware(projectId: string, makeChildLogger: (trace: string, span?: string, traceSampled?: boolean) => LoggerType, emitRequestLog?: (httpRequest: HttpRequest, trace: string, span?: string, traceSampled?: boolean) => void): Koa.Middleware<DefaultState, ParameterizedContext<AnnotatedContextType>>;
export {};