var audioContext = new (window.AudioContext || window.webkitAudioContext)();

// variables globales
var audioBuffer,
  fuenteDeReproduccion;
var splitter = audioContext.createChannelSplitter(2);
var gainIzq = audioContext.createGain();
var gainDcha = audioContext.createGain();
var pannerIzq = audioContext.createStereoPanner();
var pannerDcha = audioContext.createStereoPanner();


function solicitarAudio(url) {
  var request = new XMLHttpRequest();
  request.open("GET", url, true);
  request.responseType = "arraybuffer";
  request.onload = function() {
    audioContext.decodeAudioData(request.response, function(buffer) {
      audioBuffer = buffer;
    });
  };
  request.send();
}

function reproducirAudio() {
 // fuenteDeReproduccion --> splitter --> gainIzq  --> pannerIzq  --> destination
 //                                    ↳ gainDcha --> pannerDcha --> destination

  fuenteDeReproduccion = audioContext.createBufferSource();
  fuenteDeReproduccion.loop = true;
  fuenteDeReproduccion.buffer = audioBuffer;
  
  fuenteDeReproduccion.connect(splitter);
  
  splitter.connect(gainIzq, 0);
  splitter.connect(gainDcha, 1);
  
  gainIzq.connect(pannerIzq);
  //gainIzq.gain.value = inputIzq.value;
  
  gainDcha.connect(pannerDcha); 
  //gainDcha.gain.value = inputDcha.value;

  
  pannerIzq.connect(audioContext.destination);
  pannerIzq.pan.value = -1;
  
  pannerDcha.connect(audioContext.destination);
  pannerDcha.pan.value = 1;
  fuenteDeReproduccion.connect(audioContext.destination);
  fuenteDeReproduccion.start(audioContext.currentTime);
}

function detenerAudio() {
  fuenteDeReproduccion.stop();
}

function audio(){
  if (stop) {// si el audio está parado
    start = true;
    stop = false;
    boton.innerHTML = "||";//detener
    reproducirAudio();
  }else{// de lo contrario
    stop = true;
    start = false;
    boton.innerHTML = "▷";//reproducir
    detenerAudio()
  }
}

solicitarAudio(
  "https://s3-us-west-2.amazonaws.com/s.cdpn.io/222579/Kevin_MacLeod_-_Camille_Saint-Sans_Danse_Macabre_-_Finale.mp3"
);



// Utiliza el evento click para iniciar o detener la reproducción
boton.addEventListener("click", audio, false);

inputIzq.addEventListener("input", function() {
  gainIzq.gain.value = this.value;
});

inputDcha.addEventListener("input", function() {
  gainDcha.gain.value = this.value;
});