/**
 * A plugin which enables rendering of math equations inside
 * of reveal.js slides. Essentially a thin wrapper for MathJax.
 *
 * @author Hakim El Hattab
 */
var RevealMath = window.RevealMath || (function () {

  var options = Reveal.getConfig().math || {};
  options.mathjax = options.mathjax || 'https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.0/MathJax.js';
  options.config = options.config || 'TeX-AMS_HTML-full';
  options.tex2jax = options.tex2jax || {
    inlineMath: [['$', '$'], ['\\(', '\\)']],
    skipTags: ['script', 'noscript', 'style', 'textarea', 'pre']
  };

  loadScript(options.mathjax + '?config=' + options.config, function () {

    MathJax.Hub.Config({
      messageStyle: 'none',
      tex2jax: options.tex2jax,
      skipStartupTypeset: true
    });

    // Typeset followed by an immediate reveal.js layout since
    // the typesetting process could affect slide height
    MathJax.Hub.Queue(['Typeset', MathJax.Hub]);
    MathJax.Hub.Queue(Reveal.layout);

    // Reprocess equations in slides when they turn visible
    Reveal.addEventListener('slidechanged', function (event) {

      MathJax.Hub.Queue(['Typeset', MathJax.Hub, event.currentSlide]);

    });

  });

  function loadScript(url, callback) {

    var head = document.querySelector('head');
    var script = document.createElement('script');
    script.type = 'text/javascript';
    script.src = url;

    // Wrapper for callback to make sure it only fires once
    var finish = function () {
      if (typeof callback === 'function') {
        callback.call();
        callback = null;
      }
    };

    script.onload = finish;

    // IE
    script.onreadystatechange = function () {
      if (this.readyState === 'loaded') {
        finish();
      }
    };

    // Normal browsers
    head.appendChild(script);

  }

})();