/**
 * transformers.js (ONNX, dual-environment) TTS (text-to-speech) adapter battery.
 *
 * @module @nhtio/adk/batteries/tts/transformers_js/adapter
 *
 * @remarks
 * Battery backed by transformers.js's `text-to-speech` (TextToAudio) pipeline. **Environment-neutral**
 * — runs in Node (via `onnxruntime-node`) and the browser (via `onnxruntime-web` / WebGPU), auto-selected
 * by the package; there is no WebGPU requirement, mirroring the transformers.js STT and Embeddings
 * batteries this adapter is modeled on.
 *
 * Accepts plain text input, resolves speaker embeddings / speed / inference steps from the merged
 * constructor + per-call options, and returns a WAV-encoded {@link GeneratedMediaOutput}.
 *
 * `@huggingface/transformers` is an optional peer dependency, imported lazily.
 */
import type { GeneratedMediaOutput } from "../_shared/index";
import type { TransformersJsSynthesizeOptions } from "./types";
/**
 * TTS adapter for transformers.js's text-to-speech (TextToAudio) pipeline.
 *
 * @remarks
 * Reusable: construct once, call {@link TransformersJsTtsAdapter.synthesize} as many times as needed.
 * The pipeline is resolved lazily on first use (or via {@link preload}) and cached with single-flight
 * semantics so concurrent calls share one load.
 */
export declare class TransformersJsTtsAdapter {
    #private;
    /**
     * Whether this battery is available. transformers.js is environment-neutral (Node + browser), so
     * this is `true` whenever the runtime can import the peer — there is no WebGPU requirement.
     */
    static isAvailable(): boolean;
    /**
     * @param options - Constructor options. Validated eagerly.
     * @throws {@link @nhtio/adk/batteries!E_INVALID_TRANSFORMERS_JS_TTS_OPTIONS} when invalid.
     */
    constructor(options: unknown);
    /** Instance availability probe (honours an injected `isAvailable`). */
    isAvailable(): boolean;
    /** Eagerly loads (and caches) the pipeline so the first `synthesize` call is fast. Idempotent. */
    preload(): Promise<void>;
    /** Drops the cached pipeline and in-flight load so the next call reloads. */
    reset(): void;
    /**
     * Release the loaded model's ONNX sessions + GPU/wasm buffers, then drop the cached pipeline.
     *
     * @remarks
     * `reset()` only nulls the JS reference; the native ONNX Runtime sessions and WebGPU/wasm device
     * memory stay alive until GC. `TextToAudioPipeline` extends `Pipeline`, which exposes `dispose()` —
     * this awaits it so the memory is reclaimed between loads, swallows a disposal error (teardown must
     * not throw), and finishes with `reset()`. Idempotent.
     */
    dispose(): Promise<void>;
    /**
     * Synthesizes text into a WAV audio clip.
     *
     * @param text - The text to speak. Passed verbatim to the pipeline.
     * @param opts - Per-call options; each field overrides the constructor default of the same name.
     * @returns A {@link GeneratedMediaOutput} descriptor with `kind: 'audio'`, `mimeType: 'audio/wav'`,
     *   and the WAV bytes.
     * @throws {@link @nhtio/adk/batteries!E_TRANSFORMERS_JS_TTS_ENGINE_ERROR} when the pipeline fails to
     *   load, the synthesis call throws, or the returned audio lacks `toBlob()`.
     */
    synthesize(text: string, opts?: TransformersJsSynthesizeOptions): Promise<GeneratedMediaOutput>;
}