import { EventEmitter } from '@herbcaudill/eventemitter42';
/**
 * Receives numbered inbound messages and emits them in order. If a message is missing after a delay, asks
 * for it to be sent (or resent).
 *
 * Numbers and sends outbound messages, and responds to requests for missing messages.
 */
export declare class MessageQueue<T> extends EventEmitter<MessageQueueEvents<T>> {
    #private;
    constructor({ sendMessage, timeout }: Options<T>);
    /**
     * Messages can be received before the service is started (e.g. while waiting to be ready to send
     * over the network). They will be emitted in order when start() is called.
     */
    start(): this;
    /**
     * Stop emitting messages. Messages will be queued until start() is called again.
     */
    stop(): this;
    /**
     * Assigns a number to the message and sends it.
     */
    send(message: T): this;
    /**
     * Resends a message that was previously sent.
     */
    resend(index: number): this;
    /**
     * Queues inbound messages and, if we're started, emits them in order.
     */
    receive(message: NumberedMessage<T>): this;
}
export type NumberedMessage<T> = T & {
    index: number;
};
export type MessageQueueEvents<T> = {
    message: (message: NumberedMessage<T>) => void;
    request: (index: number) => void;
};
type Options<T> = {
    /** Send function */
    sendMessage: (message: NumberedMessage<T>) => void;
    /** Time to wait (in ms) before requesting a missing message */
    timeout?: number;
};
export {};
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