mmpSearch/assets/js/creations/audio.js

// js/audio.js
import { appState } from "./state.js";
import { highlightStep } from "./ui.js";
import { getTotalSteps } from "./utils.js";

let audioContext;
let mainGainNode;

export function getAudioContext() {
  return audioContext;
}
export function getMainGainNode() {
  return mainGainNode;
}

export function initializeAudioContext() {
  if (!audioContext) {
    audioContext = new (window.AudioContext || window.webkitAudioContext)();
    mainGainNode = audioContext.createGain();
    mainGainNode.connect(audioContext.destination);
  }
  if (audioContext.state === "suspended") {
    audioContext.resume();
  }
}

export function playMetronomeSound(isDownbeat) {
  initializeAudioContext();
  const oscillator = audioContext.createOscillator();
  const gainNode = audioContext.createGain();
  const frequency = isDownbeat ? 1000 : 800;
  oscillator.frequency.setValueAtTime(frequency, audioContext.currentTime);
  oscillator.type = "sine";
  gainNode.gain.setValueAtTime(1, audioContext.currentTime);
  gainNode.gain.exponentialRampToValueAtTime(
    0.00001,
    audioContext.currentTime + 0.05
  );
  oscillator.connect(gainNode);
  gainNode.connect(audioContext.destination);
  oscillator.start(audioContext.currentTime);
  oscillator.stop(audioContext.currentTime + 0.05);
}

// (ALTERADO) Função reescrita para usar AudioBuffers pré-carregados
export function playSample(filePath, trackId) {
  initializeAudioContext();
  if (!filePath) return;

  const track = trackId ? appState.tracks.find((t) => t.id == trackId) : null;

  // Se a função for chamada sem um ID de track (ex: clique no browser de samples),
  // usa o método antigo como fallback para uma prévia rápida.
  if (!track) {
    const audio = new Audio(filePath);
    audio.play();
    return;
  }

  // Se a track não tiver o buffer de áudio pronto, avisa no console e não toca.
  if (!track.audioBuffer) {
    console.warn(`Buffer para a track ${track.name} ainda não carregado.`);
    return;
  }

  // 1. Cria uma fonte de áudio leve (BufferSource)
  const source = audioContext.createBufferSource();
  // 2. Conecta o buffer de áudio já decodificado
  source.buffer = track.audioBuffer;

  // 3. Conecta na cadeia de áudio da track (respeitando volume e pan)
  if (track.gainNode) {
    source.connect(track.gainNode);
  } else {
    source.connect(mainGainNode); // Fallback
  }

  // 4. Toca o som imediatamente
  source.start(0);
}


function tick() {
  const totalSteps = getTotalSteps();
  if (totalSteps === 0) {
    stopPlayback();
    return;
  }
  const lastStepIndex =
    appState.currentStep === 0 ? totalSteps - 1 : appState.currentStep - 1;
  highlightStep(lastStepIndex, false);

  if (appState.metronomeEnabled) {
    const noteValue =
      parseInt(document.getElementById("compasso-b-input").value, 10) || 4;
    const stepsPerBeat = 16 / noteValue;
    if (appState.currentStep % stepsPerBeat === 0) {
      playMetronomeSound(appState.currentStep === 0);
    }
  }

  appState.tracks.forEach((track) => {
    if (track.steps[appState.currentStep] && track.samplePath) {
      playSample(track.samplePath, track.id);
    }
  });

  highlightStep(appState.currentStep, true);
  appState.currentStep = (appState.currentStep + 1) % totalSteps;
}

export function startPlayback() {
  if (appState.isPlaying || appState.tracks.length === 0) return;
  initializeAudioContext();
  const bpm = parseInt(document.getElementById("bpm-input").value, 10) || 120;
  const stepInterval = (60 * 1000) / (bpm * 4);

  if (appState.playbackIntervalId) clearInterval(appState.playbackIntervalId);

  appState.isPlaying = true;
  document.getElementById("play-btn").classList.remove("fa-play");
  document.getElementById("play-btn").classList.add("fa-pause");

  tick();
  appState.playbackIntervalId = setInterval(tick, stepInterval);
}

export function stopPlayback() {
  clearInterval(appState.playbackIntervalId);
  appState.playbackIntervalId = null;
  appState.isPlaying = false;
  highlightStep(appState.currentStep - 1, false);
  appState.currentStep = 0;
  document.getElementById("play-btn").classList.remove("fa-pause");
  document.getElementById("play-btn").classList.add("fa-play");
}

export function rewindPlayback() {
  appState.currentStep = 0;
  if (!appState.isPlaying) {
    document
      .querySelectorAll(".step.playing")
      .forEach((s) => s.classList.remove("playing"));
  }
}

export function togglePlayback() {
  if (appState.isPlaying) {
    stopPlayback();
  } else {
    startPlayback();
  }
}