(function () {
  var footnotes = function () {
     return [{
       type: 'lang',
       filter: function filter(text) {
         return text.replace(/^\[\^([\d\w]+)\]:\s*((\n+(\s{2,4}|\t).+)+)$/mg, function (str, name, rawContent, _, padding) {
           var content = converter.makeHtml(rawContent.replace(new RegExp('^' + padding, 'gm'), ''));
           return '<div class="footnote" id="footnote-' + name + '"><a href="#footnote-' + name + '"><sup>[' + name + ']</sup></a>:' + content + '</div>';
         });
       }},
       {
         type: 'lang',
         filter: function filter(text) {
           return text.replace(/^\[\^([\d\w]+)\]:( |\n)((.+\n)*.+)$/mg, function (str, name, _, content) {
             return '<small class="footnote" id="footnote-' + name + '"><a href="#footnote-' + name + '"><sup>[' + name + ']</sup></a>: ' + content + '</small>';
           });
         }
         },
       {
         type: 'lang',
         filter: function filter(text) {
           return text.replace(/\[\^([\d\w]+)\]/m, function (str, name) {
             return '<a href="#footnote-' + name + '"><sup>[' + name + ']</sup></a>';
           });
         }
       }];
  };

  // Client-side export
  if (typeof window !== 'undefined' && window.showdown && window.showdown.extensions) {
    window.showdown.extensions.footnotes = footnotes;
  }
  if (typeof module !== 'undefined') {
    module.exports = footnotes;
  }

}());