/**
 * Voice TTS module — manages Piper subprocess for text-to-speech.
 *
 * Sentence buffering: accumulates tokens until sentence boundary,
 * then pipes each sentence to Piper and streams raw PCM back.
 *
 * Audio format: 16-bit signed PCM, 22050 Hz, mono.
 */
export declare const SAMPLE_RATE = 22050;
export declare const CHANNELS = 1;
export declare const BIT_DEPTH = 16;
/**
 * Buffers streaming tokens into complete sentences for TTS.
 */
export declare class SentenceBuffer {
    private buffer;
    private onSentence;
    constructor(onSentence: (sentence: string) => void);
    /** Add a token to the buffer. Flushes complete sentences. */
    push(token: string): void;
    /** Flush any remaining text in the buffer. */
    flush(): void;
    /** Clear the buffer without flushing. */
    clear(): void;
}
/**
 * Check if Piper and the specified voice are available.
 */
export declare function isPiperAvailable(voice?: string): boolean;
export interface VoiceTTSSessionOptions {
    voice?: string;
    /** Called with raw PCM chunks (16-bit signed, 22050 Hz, mono) */
    onAudio: (pcm: Buffer) => void;
    /** Called when all queued sentences have been spoken */
    onDone: () => void;
    /** Called on error */
    onError?: (err: Error) => void;
}
/**
 * Manages a voice TTS session — buffers tokens into sentences,
 * synthesizes each with Piper, and streams PCM audio back.
 */
export declare class VoiceTTSSession {
    private voice;
    private sentenceBuffer;
    private queue;
    private processing;
    private aborted;
    private finished;
    private doneFired;
    private onAudio;
    private userOnDone;
    private onError;
    private activeProc;
    private completionPromise;
    private resolveCompletion;
    constructor(opts: VoiceTTSSessionOptions);
    /** Feed a streaming token into the session. */
    pushToken(token: string): void;
    /** Signal that no more tokens will arrive. Flushes remaining buffer. */
    finish(): void;
    /** Abort the session — stop all synthesis immediately. */
    abort(): void;
    /**
     * Resolves when the session is fully complete: all sentences synthesized
     * (onDone fired) OR the session was aborted. Lets callers wait for voice
     * playback to be fully delivered before tearing down the WebSocket binding.
     */
    waitForCompletion(): Promise<void>;
    private fireDone;
    private processQueue;
    private synthesizeSentence;
}
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