// TODO move this file into assets and use hugo pipes and babel

(function(){
  var STATES = ["colorscheme-dark", "colorscheme-light", "colorscheme-auto"];
  var LABELS = ["On", "Off", "Auto"]; // display text of dark mode setting - corresponds with STATES array

  var CS_BTN_CLASS = 'cs-mode-button';
  var CS_BTN_CONTAINER_CLASS = 'cs-mode-container';
  var CS_BTN_TEXT_CLASS = 'cs-mode-button-state';
  var CS_MODE_COOKIE_NAME = "cs_mode"; // name of cookie that stores dark mode setting

  var MODE_BTN_TEXT_ELEMENT = document.getElementById(CS_BTN_TEXT_CLASS);

  var activeState = -1; // the active index of the STATES array
  var cookieMode; // dark mode setting value retrieved from cookie

  // toggles the color scheme between the states specified in the array STATES
  function toggleColorscheme() {
    for(var i = 0; i < STATES.length; i++) {
      if (document.body.classList.contains(STATES[i])) {
        document.body.classList.remove(STATES[activeState]);
        activeState = activeState < STATES.length - 1 ? activeState + 1 : 0;
        document.body.classList.add(STATES[activeState]);
        MODE_BTN_TEXT_ELEMENT.innerText = LABELS[activeState];
        document.cookie = CS_MODE_COOKIE_NAME + "=" + STATES[activeState] + "; path=/;max-age=315360000";
        break;
      }
    }
  }

  // returns the value fo the cookie named name
  // or null if not present.
  function getCookie(name) {
    var cookieList = document.cookie.split(";")
    var value = null;

    for (var i = 0; i < cookieList.length; i++) {
      if (cookieList[i].indexOf(CS_MODE_COOKIE_NAME + "=") > -1) {
        value = cookieList[i].substring(cookieList[i].indexOf('=') + 1);
      }
    }
    return value;
  }

  cookieMode = getCookie(CS_MODE_COOKIE_NAME);

  if (cookieMode !== null) {
    for(var i = 0; i < STATES.length; i++) {
      document.body.classList.remove(STATES[i]);
    }
    document.body.classList.add(cookieMode);
    // cannot set activeState directly in here, in case cookie is not present
    // (in which case, document.body will already have the class which was
    // specified in /layouts/_default/baseof.html, which we will use later).
  }
  // now we can use document.body.classlist to set activeState.
  for(var i = 0; i < STATES.length; i++) {
    if (document.body.classList.contains(STATES[i])) {
      activeState = i;
    }
  }
  MODE_BTN_TEXT_ELEMENT.innerText = LABELS[activeState];

  // if activeState is valid, add button's event listener,
  // otherwise hide the toggle button.
  if (activeState > -1) {
    document.getElementById(CS_BTN_CLASS).addEventListener('click', function() {
      toggleColorscheme();
    })
  } else {
    document.getElementById(CS_BTN_CONTAINER_CLASS).style.display = "none";
  }
})();