function addWikiFormattingToolbar(textarea) {
  if ((typeof(document["selection"]) == "undefined")
   && (typeof(textarea["setSelectionRange"]) == "undefined")) {
    return;
  }
  
  var toolbar = document.createElement("div");
  toolbar.className = "wikitoolbar";

  function addButton(id, title, fn) {
    var a = document.createElement("a");
    a.href = "#";
    a.id = id;
    a.title = title;
    a.onclick = function() { try { fn() } catch (e) { } return false };
    a.tabIndex = 400;
    toolbar.appendChild(a);
  }

  function encloseSelection(prefix, suffix) {
    textarea.focus();
    var start, end, sel, scrollPos, subst;
    if (typeof(document["selection"]) != "undefined") {
      sel = document.selection.createRange().text;
    } else if (typeof(textarea["setSelectionRange"]) != "undefined") {
      start = textarea.selectionStart;
      end = textarea.selectionEnd;
      scrollPos = textarea.scrollTop;
      sel = textarea.value.substring(start, end);
    }
    if (sel.match(/ $/)) { // exclude ending space char, if any
      sel = sel.substring(0, sel.length - 1);
      suffix = suffix + " ";
    }
    subst = prefix + sel + suffix;
    if (typeof(document["selection"]) != "undefined") {
      var range = document.selection.createRange().text = subst;
      textarea.caretPos -= suffix.length;
    } else if (typeof(textarea["setSelectionRange"]) != "undefined") {
      textarea.value = textarea.value.substring(0, start) + subst +
                       textarea.value.substring(end);
      if (sel) {
        textarea.setSelectionRange(start + subst.length, start + subst.length);
      } else {
        textarea.setSelectionRange(start + prefix.length, start + prefix.length);
      }
      textarea.scrollTop = scrollPos;
    }
  }

  addButton("strong", "Bold text: '''Example'''", function() {
    encloseSelection("'''", "'''");
  });
  addButton("em", "Italic text: ''Example''", function() {
    encloseSelection("''", "''");
  });
  addButton("heading", "Heading: == Example ==", function() {
    encloseSelection("\n== ", " ==\n", "Heading");
  });
  addButton("link", "Link: [http://www.example.com/ Example]", function() {
    encloseSelection("[", "]");
  });
  addButton("code", "Code block: {{{ example }}}", function() {
    encloseSelection("\n{{{\n", "\n}}}\n");
  });
  addButton("hr", "Horizontal rule: ----", function() {
    encloseSelection("\n----\n", "");
  });
  addButton("np", "New paragraph", function() {
    encloseSelection("\n\n", "");
  });
  addButton("br", "Line break: [[BR]]", function() {
    encloseSelection("[[BR]]\n", "");
  });

  textarea.parentNode.insertBefore(toolbar, textarea);
}

// Add the toolbar to all <textarea> elements on the page with the class
// 'wikitext'.
var re = /\bwikitext\b/;
var textareas = document.getElementsByTagName("textarea");
for (var i = 0; i < textareas.length; i++) {
  var textarea = textareas[i];
  if (textarea.className && re.test(textarea.className)) {
    addWikiFormattingToolbar(textarea);
  }
}