(function() {
  var pairs = [
    [".aspx", ".aspx.cs"]
    ,[".h", ".c"]
  ];

  var alternate = function(url) {
    for (var pairIdx = 0; pairIdx < pairs.length; pairIdx++) {
      var pair = pairs[pairIdx];
      for (var extensionIdx = 0; extensionIdx < 2; extensionIdx++) {
        var extension = pair[extensionIdx];
        var pat = new RegExp("\\" + extension + "$");
        if (url.match(pat)) {
          return {
            extension: extension
            ,pattern: pat
            ,alternate: pair[(extensionIdx + 1) % 2]
          };
        }
      }
    }
  }

  var install = function() {
    var url = window.location.href;
    var info = alternate(url);
    if (info) {
      console.log(info);
      var link = $('<a href="#">' + info.alternate + '</a>').click(function() {
        window.location.href = url.replace(info.pattern, alternate);
      });
      console.log(link.text());
      $('#files ul.actions').append($("<li></li>").append(link));
    }
  }

  install();
})();