(function () {

    // Check if the browser supports web audio. Safari wants a prefix.
    if ('AudioContext' in window || 'webkitAudioContext' in window) {

      //////////////////////////////////////////////////
      // Here's the part for just playing an audio file.
      //////////////////////////////////////////////////
      var play = function play(audioBuffer) {
        var source = context.createBufferSource();
        source.buffer = audioBuffer;
        source.connect(context.destination);
        source.start();
      };

      var URL = 'https://s3-us-west-2.amazonaws.com/s.cdpn.io/123941/Yodel_Sound_Effect.mp3';
      var AudioContext = window.AudioContext || window.webkitAudioContext;
      var context = new AudioContext(); // Make it crossbrowser
      var gainNode = context.createGain();
      gainNode.gain.value = 1; // set volume to 100%
      var playButton = document.querySelector('#play');
      var yodelBuffer = void 0;

      // The Promise-based syntax for BaseAudioContext.decodeAudioData() is not supported in Safari(Webkit).
      window.fetch(URL)
        .then(response => response.arrayBuffer())
        .then(arrayBuffer => context.decodeAudioData(arrayBuffer,
           audioBuffer => {
              yodelBuffer = audioBuffer;
            },
            error =>
              console.error(error)
          ))

      playButton.onclick = function () {
        return play(yodelBuffer);
      };

      // Play the file every 2 seconds. You won't hear it in iOS until the audio context is unlocked.
      window.setInterval(function(){
        play(yodelBuffer);
      }, 5000);


      //////////////////////////////////////////////////
      // Here's the part for unlocking the audio context, probably for iOS only
      //////////////////////////////////////////////////

      // From https://paulbakaus.com/tutorials/html5/web-audio-on-ios/
      // "The only way to unmute the Web Audio context is to call noteOn() right after a user interaction. This can be a click or any of the touch events (AFAIK – I only tested click and touchstart)."
      
      var unmute = document.getElementById('unmute');
      unmute.addEventListener('click', unlock);

      function unlock() {
        console.log("unlocking")
        // create empty buffer and play it
        var buffer = context.createBuffer(1, 1, 22050);
        var source = context.createBufferSource();
        source.buffer = buffer;
        source.connect(context.destination);

        // play the file. noteOn is the older version of start()
        source.start ? source.start(0) : source.noteOn(0);

        // by checking the play state after some time, we know if we're really unlocked
        setTimeout(function() {
          if((source.playbackState === source.PLAYING_STATE || source.playbackState === source.FINISHED_STATE)) {
            // Hide the unmute button if the context is unlocked.
            unmute.style.display = "none";
          }
        }, 0);
      }

      // Try to unlock, so the unmute is hidden when not necessary (in most browsers).
      unlock();
    }
  }
)();