'use strict';

var client = new XMLHttpRequest();
var channel = findGetParameter('channel');
var duration = getInterval('duration');
var interval = getInterval('interval');

/**
 * @function
 * @description Processes the incoming packet.
 */
client.onload = function () {
  if (client.readyState === client.DONE) {
    if (this.status === 200 && this.responseXML !== null) {
      /* Gets current track */
      var current = this.responseXML.getElementsByTagName('song')[0];
      var artistTrack = current.getElementsByTagName('artist')[0].textContent;
      var titleTrack = current.getElementsByTagName('title')[0].textContent;

      /* Gets items on the page */
      var displayElement = document.getElementById('display');
      var artistElement = document.getElementById('artist');
      var titleElement = document.getElementById('title');

      if (artistElement.textContent !== artistTrack || titleElement.textContent !== titleTrack) {
        /* Updates text */
        artistElement.textContent = artistTrack;
        titleElement.textContent = titleTrack;

        /* Displays a pop-up window */
        displayElement.style['animation-name'] = 'fadeIn';

        setTimeout(function () {
          /* Removes a pop-up window */
          displayElement.style['animation-name'] = 'fadeOut';
        }, duration);
      }
    }
  }
};

/**
 * @function
 * @description Cyclical sending a request to update the information.
 */
setInterval(function tick() {
  client.open('GET', '//somafm.com/songs/' + channel + '.xml');
  client.send();
  return tick;
}(), interval);

/**
 * @function
 * @param {String} parameterName - Variable name
 * @returns {String} Value of variable
 * @description Searches for the value of the GET variable on the page.
 */
function findGetParameter(parameterName) {
  var result = null;
  var tmp = [];

  var items = window.location.search.substr(1).split('&');
  for (var index = 0; index < items.length; index++) {
    tmp = items[index].split('=');
    if (tmp[0] === parameterName) {
      result = decodeURIComponent(tmp[1]);
    }
  }

  return result;
}

/**
 * @function
 * @param {String} parameterName - Variable name
 * @returns {Number} Timer value, default 10 seconds
 * @description Gets the settings for the specified timer.
 */
function getInterval(parameterName) {
  var value = findGetParameter(parameterName);
  var interval = parseInt(value, 10);
  var result = 10000;

  if (isNaN(interval) === false) {
    result = interval;
  }

  return result;
}