import { AbstractTTSClient } from "../core/abstract-tts";
import type { SpeakOptions, TTSCredentials, UnifiedVoice } from "../types";
/**
 * eSpeak TTS Client for Node.js environments
 *
 * This client uses the text2wav package for server-side eSpeak TTS synthesis.
 * For browser environments, use EspeakBrowserTTSClient instead.
 */
export declare class EspeakNodeTTSClient extends AbstractTTSClient {
    constructor(credentials?: TTSCredentials);
    /**
     * Get the list of required credential types for this engine
     * @returns Array of required credential field names
     */
    protected getRequiredCredentials(): string[];
    /**
     * eSpeak does not require credentials in Node.js
     */
    checkCredentials(): Promise<boolean>;
    /**
     * Synthesize text to audio bytes (Uint8Array)
     * @param text Text to synthesize
     * @param options Synthesis options
     * @returns Promise resolving to audio bytes
     */
    synthToBytes(text: string, options?: SpeakOptions): Promise<Uint8Array>;
    /**
     * Synthesize text to a byte stream (ReadableStream)
     * @param text Text to synthesize
     * @param options Synthesis options
     * @returns Promise resolving to an object containing the audio stream and an empty word boundaries array.
     */
    synthToBytestream(text: string, options?: SpeakOptions): Promise<{
        audioStream: ReadableStream<Uint8Array>;
        wordBoundaries: Array<{
            text: string;
            offset: number;
            duration: number;
        }>;
    }>;
    /**
     * Return available voices for eSpeak
     */
    _getVoices(): Promise<UnifiedVoice[]>;
}
export { EspeakNodeTTSClient as EspeakTTSClient };