// This module, TensorFlow and the model are imported only after Transcribe.
let enginePromise, model;
const MODEL = 'https://cdn.jsdelivr.net/npm/@spotify/basic-pitch@1.0.1/model/model.json';
async function engine() {
  if (!enginePromise)
    enginePromise = (async () => {
      const tf = await import('https://esm.sh/@tensorflow/tfjs@4.22.0');
      await selectBackend(
        tf,
        !!navigator.gpu,
        () => import('https://esm.sh/@tensorflow/tfjs-backend-webgpu@4.22.0'),
      );
      await tf.ready();
      const pitch = await import(
        'https://esm.sh/@spotify/basic-pitch@1.0.1?deps=@tensorflow/tfjs@4.22.0'
      );
      const graph = await tf.loadGraphModel(MODEL);
      model = new pitch.BasicPitch(Promise.resolve(graph));
      return { tf, pitch, backend: tf.getBackend() };
    })().catch((error) => {
      enginePromise = null;
      throw error;
    });
  return enginePromise;
}
export async function selectBackend(tf, hasGPU, loadGPU) {
  if (hasGPU) {
    try {
      await loadGPU();
      if (await tf.setBackend('webgpu')) return 'webgpu';
    } catch {}
  }
  for (const backend of ['webgl', 'cpu']) {
    try {
      if (await tf.setBackend(backend)) return backend;
    } catch {}
  }
  throw new Error('No TensorFlow backend is available in this browser.');
}
export async function transcribe(buffer, progress) {
  const decoded = await new OfflineAudioContext(1, 1, 22050).decodeAudioData(buffer);
  if (decoded.duration > 900) throw new Error('Browser transcription is limited to 15 minutes.');
  const context = new OfflineAudioContext(1, Math.ceil(decoded.duration * 22050), 22050),
    source = context.createBufferSource();
  source.buffer = decoded;
  source.connect(context.destination);
  source.start();
  const audio = await context.startRendering();
  progress('Loading Basic Pitch library and model…');
  const { tf, pitch, backend } = await engine();
  const frames = [],
    onsets = [];
  // Basic Pitch 1.0.1 retains intermediate tensors; release each run's scope.
  // Model weights were loaded before this scope and stay available for reuse.
  tf.engine().startScope();
  try {
    await model.evaluateModel(
      audio.getChannelData(0),
      (f, o) => {
        frames.push(...f);
        onsets.push(...o);
      },
      (p) => progress(`Transcribing on ${backend}: ${Math.round(p * 100)}%`),
    );
  } finally {
    tf.engine().endScope();
  }
  return {
    notes: pitch.noteFramesToTime(pitch.outputToNotesPoly(frames, onsets, 0.25, 0.25, 5)),
    engine: `basic-pitch-1.0.1/${backend}`,
  };
}