// Opus codec wrapper. Uses the native @discordjs/opus addon when it happens to
// be installed (faster), otherwise opusscript (WASM): no compiler needed, so it
// installs cleanly on arm64 SBCs.
import { createRequire } from "node:module";

const require = createRequire(import.meta.url);

export const SAMPLE_RATE = 48_000;
export const FRAME_SAMPLES = 960; // 20 ms @ 48 kHz
export const FRAME_BYTES = FRAME_SAMPLES * 2; // mono Int16

let backend = null;

function loadBackend() {
  if (backend) return backend;
  try {
    const { OpusEncoder } = require("@discordjs/opus");
    backend = {
      name: "@discordjs/opus (native)",
      create(channels) {
        const codec = new OpusEncoder(SAMPLE_RATE, channels);
        return {
          encode: (pcm) => codec.encode(pcm),
          decode: (data) => codec.decode(data),
          setBitrate: (bps) => codec.setBitrate(bps),
          dispose() {},
        };
      },
    };
  } catch {
    const OpusScript = require("opusscript");
    backend = {
      name: "opusscript (wasm)",
      create(channels) {
        const codec = new OpusScript(SAMPLE_RATE, channels, OpusScript.Application.VOIP);
        return {
          encode: (pcm) => Buffer.from(codec.encode(pcm, pcm.length / (2 * channels))),
          decode: (data) => Buffer.from(codec.decode(data)),
          setBitrate: (bps) => codec.setBitrate(bps),
          dispose: () => codec.delete(),
        };
      },
    };
  }
  return backend;
}

export function opusBackendName() {
  return loadBackend().name;
}

/** Mono 48 kHz Opus codec (encoder + decoder state). */
export function createOpusCodec({ bitrate } = {}) {
  const codec = loadBackend().create(1);
  if (bitrate) {
    try { codec.setBitrate(bitrate); } catch { /* keep the library default */ }
  }
  return codec;
}