import { fetch as undiciFetch } from "undici";
import { EventSource, type ErrorEvent } from "eventsource";
type Severity = "info" | "error";
interface Options {
    source: string;
    target: string;
    logger?: Pick<Console, Severity>;
    fetch?: any;
}
declare class Client {
    #private;
    constructor({ source, target, logger, fetch, }: Options);
    static createChannel({ fetch }?: {
        fetch?: typeof undiciFetch | undefined;
    }): Promise<string>;
    onmessage(msg: MessageEvent): Promise<void>;
    onopen(): void;
    onerror(err: ErrorEvent): void;
    start(): EventSource;
}
export default Client;