/**
 * apply tagOpen/tagClose to selection in textarea, use sampleText instead
 * of selection if there is none copied and adapted from phpBB
 */
function insertTags(txtarea, tagOpen, tagClose, sampleText) {
  txtarea = document.getElementById(txtarea)
  var agt = navigator.userAgent.toLowerCase();
  var is_gecko = (agt.indexOf('gecko') != -1);
  // IE
  if(document.selection  && !is_gecko) {
    var theSelection = document.selection.createRange().text;
    if(!theSelection) { theSelection=sampleText;}
    txtarea.focus();
    if(theSelection.charAt(theSelection.length - 1) == " "){// exclude ending space char, if any
      theSelection = theSelection.substring(0, theSelection.length - 1);
      document.selection.createRange().text = tagOpen + theSelection + tagClose + " ";
    } else {
      document.selection.createRange().text = tagOpen + theSelection + tagClose;
    }
  // Mozilla
  } else if(txtarea.selectionStart || txtarea.selectionStart == '0') {
     var startPos = txtarea.selectionStart;
    var endPos = txtarea.selectionEnd;
    var scrollTop=txtarea.scrollTop;
    var myText = (txtarea.value).substring(startPos, endPos);
    if(!myText) { myText=sampleText;}
    if(myText.charAt(myText.length - 1) == " "){ // exclude ending space char, if any
      subst = tagOpen + myText.substring(0, (myText.length - 1)) + tagClose + " ";
    } else {
      subst = tagOpen + myText + tagClose;
    }
    txtarea.value = txtarea.value.substring(0, startPos) + subst +
    txtarea.value.substring(endPos, txtarea.value.length);
    txtarea.focus();

    var cPos=startPos+(tagOpen.length+myText.length+tagClose.length);
    txtarea.selectionStart=cPos;
    txtarea.selectionEnd=cPos;
    txtarea.scrollTop=scrollTop;

  // All others
  } else {
    var copy_alertText=alertText;
    var re1=new RegExp("\\$1","g");
    var re2=new RegExp("\\$2","g");
    copy_alertText=copy_alertText.replace(re1,sampleText);
    copy_alertText=copy_alertText.replace(re2,tagOpen+sampleText+tagClose);
    var text;
    if (sampleText) {
      text=prompt(copy_alertText);
    } else {
      text="";
    }
    if(!text) { text=sampleText;}
    text=tagOpen+text+tagClose;
    //append to the end
    txtarea.value += "\n"+text;

    // in Safari this causes scrolling
    if(!is_safari) {
      txtarea.focus();
    }

  }
  // reposition cursor if possible
  if (txtarea.createTextRange) txtarea.caretPos = document.selection.createRange().duplicate();
}
