import { estimateSceneMix, MAX_MIX_WORKING_BYTES } from "/packages/acoustics-core/mixdown.js";

export function createAudioRuntime() {
  let worker = null;
  let rejectWorker = null;
  let playbackContext = null;
  let playbackSource = null;

  function cancelMix() {
    if (!worker) return false;
    worker.terminate();
    worker = null;
    const reject = rejectWorker;
    rejectWorker = null;
    reject?.(new DOMException("사용자가 mix 생성을 취소했습니다.", "AbortError"));
    return true;
  }

  function renderMix(scene, assetBuffers) {
    if (worker) throw new Error("이미 확인용 mix를 만들고 있습니다.");
    const estimate = estimateSceneMix(scene, assetBuffers);
    const crossThreadBytes = estimate.workingBytes + estimate.assetBytes;
    if (crossThreadBytes > MAX_MIX_WORKING_BYTES) {
      throw new Error(
        `decode buffer와 Worker 복사본을 포함한 예상 메모리 ${(crossThreadBytes / 1024 ** 2).toFixed(1)} MiB가 ` +
          `${(MAX_MIX_WORKING_BYTES / 1024 ** 2).toFixed(0)} MiB 한도를 넘습니다.`,
      );
    }
    return new Promise((resolve, reject) => {
      const currentWorker = new Worker("/apps/dataset-builder/mix-worker.js", { type: "module" });
      worker = currentWorker;
      rejectWorker = reject;
      currentWorker.addEventListener("message", ({ data }) => {
        if (worker !== currentWorker) return;
        worker = null;
        rejectWorker = null;
        currentWorker.terminate();
        if (data.ok) resolve(data.result);
        else reject(new Error(data.message));
      });
      currentWorker.addEventListener("error", (event) => {
        if (worker !== currentWorker) return;
        worker = null;
        rejectWorker = null;
        currentWorker.terminate();
        reject(new Error(event.message || "mix Worker가 중단되었습니다."));
      });
      currentWorker.postMessage({ scene, assetBuffers: [...assetBuffers] });
    });
  }

  function stopPlayback() {
    if (!playbackSource) return false;
    playbackSource.onended = null;
    try {
      playbackSource.stop();
    } catch {
      // 이미 끝난 source는 정리만 한다.
    }
    playbackSource.disconnect();
    playbackSource = null;
    return true;
  }

  async function play(result, onEnded) {
    stopPlayback();
    playbackContext ??= new AudioContext();
    await playbackContext.resume();
    const buffer = playbackContext.createBuffer(1, result.samples.length, result.sampleRate);
    buffer.copyToChannel(result.samples, 0);
    playbackSource = playbackContext.createBufferSource();
    playbackSource.buffer = buffer;
    playbackSource.connect(playbackContext.destination);
    playbackSource.onended = () => {
      playbackSource?.disconnect();
      playbackSource = null;
      onEnded?.();
    };
    playbackSource.start();
  }

  function dispose() {
    cancelMix();
    stopPlayback();
    playbackContext?.close();
    playbackContext = null;
  }

  return {
    cancelMix,
    dispose,
    get isMixing() {
      return Boolean(worker);
    },
    get isPlaying() {
      return Boolean(playbackSource);
    },
    play,
    renderMix,
    stopPlayback,
  };
}