function toArrayBuffer(src: Buffer | Uint8Array): ArrayBuffer {
  const u8 = src instanceof Uint8Array ? src : new Uint8Array(src);
  return u8.buffer.slice(u8.byteOffset, u8.byteOffset + u8.byteLength) as ArrayBuffer;
}

export async function enableAudioE2EE(pc: RTCPeerConnection, keyBuffer: Buffer | Uint8Array) {
  const raw = toArrayBuffer(keyBuffer);
  if (raw.byteLength !== 32) throw new Error("E2EE key must be 32 bytes");

  const key = await crypto.subtle.importKey(
    "raw",
    raw,
    { name: "AES-CTR" },
    false,
    ["encrypt", "decrypt"]
  );

  const makeCounter = (ts: number, dir: number) => {
    const counter = new Uint8Array(16);
    const dv = new DataView(counter.buffer);
    dv.setUint32(0, dir, false);              // разделяем направление
    dv.setBigUint64(8, BigInt(ts), false);    // nonce из timestamp кадра
    return counter;
  };

  const attachSender = (sender: RTCRtpSender) => {
    // @ts-ignore Chromium/Electron API
    if (!sender.createEncodedStreams) return;
    // @ts-ignore
    const { readable, writable } = sender.createEncodedStreams();

    const enc = new TransformStream({
      async transform(frame: any, controller) {
        const counter = makeCounter(frame.timestamp ?? 0, 1);
        const out = await crypto.subtle.encrypt(
          { name: "AES-CTR", counter, length: 64 },
          key,
          frame.data
        );
        frame.data = new Uint8Array(out); // тот же размер
        controller.enqueue(frame);
      }
    });

    readable.pipeThrough(enc).pipeTo(writable).catch(() => {});
  };

  const attachReceiver = (receiver: RTCRtpReceiver) => {
    // @ts-ignore Chromium/Electron API
    if (!receiver.createEncodedStreams) return;
    // @ts-ignore
    const { readable, writable } = receiver.createEncodedStreams();

    const dec = new TransformStream({
      async transform(frame: any, controller) {
        const counter = makeCounter(frame.timestamp ?? 0, 1);
        const out = await crypto.subtle.decrypt(
          { name: "AES-CTR", counter, length: 64 },
          key,
          frame.data
        );
        frame.data = new Uint8Array(out); // тот же размер
        controller.enqueue(frame);
      }
    });

    readable.pipeThrough(dec).pipeTo(writable).catch(() => {});
  };

  pc.getSenders().forEach((s) => s.track?.kind === "audio" && attachSender(s));
  pc.getReceivers().forEach((r) => r.track?.kind === "audio" && attachReceiver(r));

  pc.addEventListener("track", (e) => {
    if (e.track.kind === "audio") attachReceiver(e.receiver);
  });
}