var currentRange,_parentElem,supportRange = typeof document.createRange === 'function';
  function getCurrentRange() {
    var selection,
    range,
    txt = $('editor');
    if(supportRange){
      selection = document.getSelection();
      if (selection.getRangeAt && selection.rangeCount) {
        range = document.getSelection().getRangeAt(0);
        _parentElem = range.commonAncestorContainer;
      }
    }else{
      range = document.selection.createRange();
      _parentElem = range.parentElement();
    }
    if( _parentElem && (avalon.contains(txt, _parentElem) || txt === _parentElem) ){
      parentElem = _parentElem;
      return range;
    }
    return range;
  }
  function saveSelection() {
    currentRange = getCurrentRange();
  }
  function restoreSelection() {
    if(!currentRange){
      return;
    }
    var selection,
    range;
    if(supportRange){
      selection = document.getSelection();
      selection.removeAllRanges();
      selection.addRange(currentRange);
    }else{
      range = document.selection.createRange();
      range.setEndPoint('EndToEnd', currentRange);
      if(currentRange.text.length === 0){
        range.collapse(false);
      }else{
        range.setEndPoint('StartToStart', currentRange);
      }
      range.select();
    }
  }

function insertImage(html){
    restoreSelection();
    if(document.selection)
      currentRange.pasteHTML(html); 
    else
      document.execCommand("insertImage", false,html);
    saveSelection();
  }
  avalon.bind($('post_input'),'mouseup',function(e){
    saveSelection();
  });
  avalon.bind($('post_input'),'keyup',function(e){
    saveSelection();
  });