import { AbstractTTSClient } from "../core/abstract-tts.js";
import type { SpeakOptions, TTSCredentials, UnifiedVoice } from "../types.js";
/**
 * eSpeak TTS client for browser environments using meSpeak.js
 * This provides eSpeak functionality in browsers and Node.js via WebAssembly
 * For Node.js-only environments with better performance, use EspeakNodeTTSClient instead.
 */
export declare class EspeakBrowserTTSClient extends AbstractTTSClient {
    private nodeClient?;
    private meSpeak;
    private meSpeakReady;
    constructor(credentials?: TTSCredentials);
    synthToBytes(text: string, options?: SpeakOptions): Promise<Uint8Array>;
    private ensureMeSpeakLoaded;
    private getVoicePayload;
    /**
     * 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 WASM
     */
    _getVoices(): Promise<UnifiedVoice[]>;
    /**
     * Get the list of required credential types for this engine
     * @returns Array of required credential field names
     */
    protected getRequiredCredentials(): string[];
    /**
     * Check if credentials are valid (eSpeak doesn't need credentials)
     */
    checkCredentials(): Promise<boolean>;
    /**
     * Get detailed credential validation info
     */
    checkCredentialsAdvanced(): Promise<{
        valid: boolean;
        message: string;
        details?: Record<string, any>;
    }>;
}
export { EspeakBrowserTTSClient as EspeakWasmTTSClient };