function preg_quote(str, delimiter) {
  // Quote regular expression characters plus an optional character
  //
  // version: 1107.2516
  // discuss at: http://phpjs.org/functions/preg_quote
  // +   original by: booeyOH
  // +   improved by: Ates Goral (http://magnetiq.com)
  // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // +   bugfixed by: Onno Marsman
  // +   improved by: Brett Zamir (http://brett-zamir.me)
  // *     example 1: preg_quote("$40");
  // *     returns 1: '\$40'
  // *     example 2: preg_quote("*RRRING* Hello?");
  // *     returns 2: '\*RRRING\* Hello\?'
  // *     example 3: preg_quote("\\.+*?[^]$(){}=!<>|:");
  // *     returns 3: '\\\.\+\*\?\[\^\]\$\(\)\{\}\=\!\<\>\|\:'
  return (str + '').replace(new RegExp('[.\\\\+*?\\[\\^\\]$(){}=!<>|:\\' + (delimiter || '') + '-]', 'g'), '\\$&');
}

function loadScript(url, cb) {
  var script;
  script = document.createElement('script');
  script.src = url;
  script.onload = function(){
    cb && cb({isNew: true})
  };
  document.getElementsByTagName('head')[0].appendChild(script);
}

var Formula = {
  mode: 'plain',
  latexeasy: null,
  init: function () {
    // console.log('Formula.init')
    Formula.initMode();
    Formula.initEvent();
    Formula.initSubmit();
  },
  renderPlain: function () {
    var $preview = $('#preview');
    var value = $('#editor').val();
    if (!value) {
      $preview.hide();
      return;
    }
    value = encodeURIComponent(value);
    var formulaConfig = editor.getOpt('formulaConfig');
    var src = formulaConfig.imageUrlTemplate.replace(/\{\}/, value);
    $('#previewImage').attr('src', src);
    $preview.show();
  },
  setValuePlain: function (value) {
    $('#editor').val(value);
    Formula.renderPlain();
  },
  setValueLive: function (value) {
    if (!Formula.latexeasy) {
      setTimeout(function () {
        Formula.setValueLive(value);
      }, 100);
      return;
    }
    Formula.latexeasy.call('set.latex', {latex: value});
  },
  initMode: function () {
    var formulaConfig = editor.getOpt('formulaConfig');
    if ('live' === formulaConfig.editorMode) {
      $('#liveEditor').attr('src', formulaConfig.editorLiveServer+'/editor');
      $('#modeLive').show();
      Formula.mode = 'live';
    } else {
      $('#modePlain').show();
      Formula.mode = 'plain';
    }
    var img = editor.selection.getRange().getClosedNode();
    if (img && img.getAttribute('data-formula-image') !== null) {
      var value = img.getAttribute('data-formula-image');
      if (value) {
        Formula.setValue(decodeURIComponent(value));
      }
    }
  },
  setValue: function (value) {
    switch (Formula.mode) {
      case 'plain':
        Formula.setValuePlain(value);
        break;
      case 'live':
        Formula.setValueLive(value);
        break;
    }
  },
  getValue: function (cb) {
    switch (Formula.mode) {
      case 'plain':
        cb($.trim($('#editor').val()));
        break;
      case 'live':
        Formula.latexeasy.call('get.latex', {}, function (data) {
          cb(data.latex);
        });
        break;
    }
  },
  initEvent: function () {
    var changeTimer = null, le;
    switch (Formula.mode) {
      case 'plain':
        // console.log('Formula.initEvent');
        $('#editor').on('change keypress', function () {
          changeTimer && clearTimeout(changeTimer);
          changeTimer = setTimeout(function () {
            Formula.renderPlain();
          }, 1000);
        });
        $('#inputDemo').on('click', function () {
          $('#editor').val('f(a) = \\frac{1}{2\\pi i} \\oint\\frac{f(z)}{z-a}dz');
          Formula.renderPlain();
        });
        break;
      case 'live':
        var formulaConfig = editor.getOpt('formulaConfig');
        loadScript(formulaConfig.editorLiveServer+'/vendor/LatexEasyEditor/editor/sdk.js',function(){
          le = new window.LatexEasy(document.getElementById('liveEditor'));
          le.on('ready', function () {
            Formula.latexeasy = le;
          });
          le.init();
        });
        break;
    }
  },
  initSubmit: function () {
    dialog.onclose = function (t, ok) {
      if (!ok) {
        return true;
      }
      // console.log('onclose', t, ok);
      Formula.getValue(function (value) {
        editor.execCommand('formula', value);
        editor.fireEvent('saveScene');
        dialog.close(false);
      });
      return false;
    };
  }
};
