const audio = (function () {
  const audio = {};

  let music = [];
  let current_index = -1;
  let links, parent;
  let selected = false;
  let playing = false;
  let built = false;
  let initted = false;
  let ui = null;

  audio.init = function () {
    if (initted) {
      audio.index();
      return;
    }
    parent = document.querySelector("#audio");

    audio.index();
    audio.build();
    if (music.length) {
      audio.el.src = music[0].href;
    }
    initted = true;
  };

  audio.index = function (files) {
    music = [];
    current_index = -1;
    if (files) {
      music = files
        .filter((file) => AUDIO_REGEXP.test(file.filename))
        .map((file) => ({
          href: make_link(file),
          title: file.filename.replace(AUDIO_REGEXP, ""),
        }));
    } else {
      var links = document.querySelectorAll("a");
      Array.prototype.slice.apply(links).forEach(function (link) {
        if (!link.href.match(/\.(mp3|wav|aiff?|m4a|ogg|opus|flac)$/)) return;
        link.dataset.index = music.length;
        music.push({
          el: link,
          href: link.href,
          title: link.innerText,
        });
        if (playing && link.href === audio.el.src) {
          current_index = parseInt(link.dataset.index);
        }
      });
    }
    // console.log(music);
    if (playing) {
      audio.set_cursor();
    }
  };

  audio.build = function () {
    if (built) return;
    built = true;
    audio.el = document.createElement("audio");
    audio.el.setAttribute("controls", true);
    // audio.el.addEventListener("loadeddata", () => { if (selected) audio.el.play() })
    audio.el.addEventListener("ended", this.nextUnlessFinished.bind(this));
    parent.appendChild(audio.el);
    document.body.addEventListener("keydown", audio.keydown);
  };

  audio.destroy = function () {
    audio.el.pause();
    parent.removeChild(audio.el);
    audio.el = null;
    document.body.removeEventListener("keydown", audio.keydown);
    built = false;
  };

  audio.listen = function (uiController) {
    ui = uiController;
  };

  audio.play = function (index) {
    current_index = (parseInt(index) + music.length) % music.length;
    if (!music[current_index]) {
      return;
    }
    playing = true;
    audio.el.src = music[current_index].href;
    audio.el.play();
    audio.set_cursor();
    if (ui) {
      ui.onPlay(music[current_index]);
    }
  };

  audio.pause = function () {
    audio.el.pause();
    if (ui) {
      ui.onPause();
    }
  };

  audio.toggle = function () {
    if (audio.el.paused) {
      audio.el.play();
      if (ui && music[current_index]) {
        ui.onPlay(music[current_index]);
      }
    } else {
      audio.el.pause();
      if (ui) {
        ui.onPause();
      }
    }
  };

  audio.set_cursor = function () {
    selected = document.querySelector(".playing");
    if (selected) selected.classList.remove("playing");
    if (current_index > -1 && music[current_index].el) {
      music[current_index].el.classList.add("playing");
    }
  };

  audio.prev = function () {
    audio.play(current_index - 1);
  };

  audio.next = function () {
    audio.play(current_index + 1);
  };

  audio.nextUnlessFinished = function () {
    if (current_index < music.length - 1) {
      audio.next();
    }
  };

  audio.keydown = function (event) {
    function element_is_text_input(element) {
      var tagName = element.tagName.toLowerCase();
      return (
        (tagName == "input" && element.type == "text") ||
        tagName == "textarea" ||
        tagName == "button"
      );
    }
    if (element_is_text_input(document.activeElement)) {
      return;
    }
    if (app.typing || event.ctrlKey || event.altKey || event.metaKey) return;
    if (!music[current_index]) return;
    switch (event.keyCode) {
      case 37: // left
        if (event.shiftKey) {
          audio.el.currentTime -= 10;
        } else {
          audio.prev();
        }
        break;
      case 39: // right
        if (event.shiftKey) {
          audio.el.currentTime += 10;
        } else {
          audio.next();
        }
        break;
      case 32: // spacebar
        event.preventDefault();
        audio.toggle();
        break;
    }
  };

  return audio;
})();