/**
 * Text → voice-note synthesis (OpenAI TTS).
 *
 * Channel-agnostic and framework-free: every dependency (client, enablement,
 * voice mapping, instructions) is injected by the host, so this module never
 * reads `process.env` and never imports a transport.
 *
 * Distinct from `src/core/voice.ts`, which maps languages to Twilio/Polly
 * voice identifiers for phone-call TwiML. This module produces Ogg/Opus audio
 * bytes for voice-note style delivery.
 *
 * TTS with `response_format: "opus"` returns mono Ogg/Opus and the duration
 * falls out of the container (see `ogg.ts`). The synthesizer validates both — a
 * non-mono or unparseable response is refused rather than delivered as a
 * broken bubble.
 */
import type OpenAI from "openai";
export interface VoiceNote {
    /** Mono Ogg/Opus bytes, sendable as-is with mimetype `audio/ogg; codecs=opus`. */
    bytes: Uint8Array;
    /** Whole seconds for the voice-note bubble, parsed from the Ogg container. */
    seconds: number;
}
export interface SynthesizeOptions {
    /** Persona id — the host's `voiceFor` decides what it means. */
    personaId?: string | null;
    /** Extra delivery steering appended to the configured base instructions. */
    instructions?: string;
}
export interface SynthesizerConfig {
    /** Lazy OpenAI client — injected so this module never reads env. */
    client: () => OpenAI;
    /** Master gate; false makes the synthesizer a no-op null. */
    enabled: () => boolean;
    /** TTS model. */
    model?: string;
    /** Voice for a persona id (host-owned mapping). */
    voiceFor?: (personaId: string | null | undefined) => string;
    /** Base delivery instructions prepended to every request. */
    baseInstructions?: string;
    /** Input text clamp — long voice notes are a poor listening experience. */
    maxChars?: number;
    /** Playback speed multiplier (OpenAI speech `speed`, 0.25–4). Default 1. */
    speed?: number;
}
export declare const DEFAULT_MAX_VOICE_TEXT_CHARS = 550;
/** Synthesize text into a voice note, or null when it cannot be delivered. */
export type Synthesizer = (text: string, options?: SynthesizeOptions) => Promise<VoiceNote | null>;
/**
 * Build a synthesizer: text → VoiceNote | null.
 *
 * Returns null (never throws) when disabled, when the text is empty, or when
 * synthesis or container validation fails — callers always have a text
 * fallback available.
 */
export declare function createSynthesizer(config: SynthesizerConfig): Synthesizer;