/**
 * @flow strict
 */

"use strict";

type DirectMessageObject<UserId: number> = {|
    message_type: string,
    ids: $ReadOnlyArray<UserId>,
|};
type StreamObject = {|
    message_type: string,
    stream_id: number,
    topic: string,
|};

type Worker<UserId> = {|
    get_current_time: () => number, // as ms since epoch
    notify_server_start: (DirectMessageObject<UserId> | StreamObject) => void,
    notify_server_stop: (DirectMessageObject<UserId> | StreamObject) => void,
|};

declare export function update<UserId>(
    worker: Worker<UserId>,
    new_recipient: DirectMessageObject<UserId> | StreamObject | null,
): void;