var audio = (function(){
  var audio = {}
  
  var el, music = [], current_index = -1
  var links, comment, parent
  var selected = false
  var playing = false
  var built = false

  audio.init = function () {
    comment = document.querySelector("#comment")
    parent = document.querySelector("#audio")
    
    audio.index()
    audio.build()
    el.src = music[0]
  }
  audio.index = function () {
    music = []
    var links = document.querySelectorAll("a")
    Array.prototype.slice.apply(links).forEach(function(link){
      if (! link.href.match(/\.(mp3|wav|ogg|opus|flac)$/)) return
      link.dataset.index = music.length
      music.push(link)
      if (playing && link.href === el.src) {
        current_index = parseInt(link.dataset.index)
      }
    })
    if (playing) {
      audio.set_cursor()
    }
  }
  audio.build = function () {
    if (built) return
    built = true
    el = audio.el = document.createElement("audio")
    el.setAttribute("controls", true)
    el.addEventListener("loadeddata", () => { if (selected) el.play() })
    el.addEventListener("ended", audio.next)
    parent.appendChild(el)
    document.body.addEventListener("keydown", audio.keydown)
  }
  audio.destroy = function () {
    el.pause()
    el = null
    parent.removeChild(el)
    document.body.removeEventListener("keydown", audio.keydown)
    built = false
  }
  audio.play = function (index) {
    playing = true
    current_index = (parseInt(index) + music.length) % music.length
    el.src = music[current_index].href
    audio.set_cursor()
  }
  audio.set_cursor = function () {
    selected = document.querySelector(".playing")
    if (selected) selected.classList.remove("playing")
    music[current_index].classList.add("playing")
  }
  audio.prev = function (){
    audio.play(current_index - 1)
  }
  audio.next = function (){
    audio.play(current_index + 1)
  }
  audio.toggle = function (){
    if (el.paused) el.play()
    else el.pause()
  }
  audio.keydown = function(e){
    function element_is_text_input(el) {
      var tagName = el.tagName.toLowerCase()
      return (tagName == 'input' && el.type == 'text' || tagName == 'textarea' || tagName == 'button')
    }
    if (element_is_text_input(document.activeElement)) {
      return
    }
    if (app.typing || e.ctrlKey || e.altKey || e.metaKey) return
    switch (e.keyCode) {
      case 37: // left
        if (e.shiftKey) {
          el.currentTime -= 10
        } else {
          audio.prev()
        }
        break;
      case 39: // right
        if (e.shiftKey) {
          el.currentTime += 10
        } else {
          audio.next()
        }
        break;
      case 32: // spacebar
        e.preventDefault()
        audio.toggle()
        break;
    }
  }
  
  return audio

})()