getWrapperAncestor = function(elt) {

  var parent = elt ;

  while (parent != null) {

      if (CY.DOM.hasClass(parent, 'c-s')) 

        return parent ;

      parent = parent.parentNode ;

  }

  return null ; 

}

hasWrapperAncestor = function(elt) {

  return (getWrapperAncestor(elt) != null) ;

/*  var parent = elt ;

  while (parent != null) {

      if (CY.DOM.hasClass(parent, 'c-s')) 

        return true ;

      parent = parent.parentNode ;

  }

  return false ;*/ 

}

// returns null or :

// {'text' : textcontent, 'start': {'elt':startNode, 'nbChar':startOffset(==number of characters to selection start in the start node},

// 'end': ....}

// the text attribute is informational having it empty doesn't mean selection is empty !!

// when selection starts/ends in/on a non textual element (<hr/> for example) we very often have anchorNode/focusNode == body elt

// TODO adapt this body case by considering offset ( cf. http://www.w3.org/TR/DOM-Level-2-Traversal-Range/ranges.html)

getSelectionInfo  = function () {

  var startNode = null, endNode = null, startOffset = 0, endOffset = 0, text = '' ;

  if (window.getSelection) { // everything else than IE

    var userSelection = window.getSelection();

    if (userSelection.rangeCount > 0) {

      var range = userSelection.getRangeAt(0) ;

      text = range.toString() ;

      if (text != "")  {

        // selection occured from right to left ? :

        var r1 = document.createRange() ;r1.setStart(userSelection.anchorNode, userSelection.anchorOffset) ;r1.collapse(true) ;

        var r2 = document.createRange() ;r2.setEnd(userSelection.focusNode, userSelection.focusOffset) ;r2.collapse(false) ;

        var leftToRight = (r2.compareBoundaryPoints(2, r1) == 1) ; // 2 is for END_TO_END

//        CY.log("leftToRight : " + leftToRight) ;

        startNode = (leftToRight) ? userSelection.anchorNode.parentNode : userSelection.focusNode.parentNode ;  

        // GIB: when selecting amath, we should go up in the dom to find the accurate start/end Nodes

        if (startNode.nodeName == 'mi' || startNode.nodeName == 'mo') {

          startNode = startNode.parentElement.parentElement.parentElement.parentElement;

        }

        innerStartNode = (leftToRight) ? userSelection.anchorNode : userSelection.focusNode ;

        endNode = (leftToRight) ? userSelection.focusNode.parentNode : userSelection.anchorNode.parentNode;

        // GIB: when selecting amath, we should go up in the dom to find the accurate start/end Nodes

        if (endNode.nodeName == 'mi' || endNode.nodeName == 'mo') {

          endNode = endNode.parentElement.parentElement.parentElement.parentElement;

        }

        innerEndNode = (leftToRight) ? userSelection.focusNode : userSelection.anchorNode;

        startOffset = (leftToRight) ? userSelection.anchorOffset : userSelection.focusOffset;

        endOffset = (leftToRight) ? userSelection.focusOffset : userSelection.anchorOffset ;

        if (!hasWrapperAncestor(endNode) && hasWrapperAncestor(startNode)){

          var r3 = document.createRange() ;

          r3.setStart(innerStartNode, startOffset) ;

          var csStartAncestor = getWrapperAncestor(startNode) ;

          var next = csStartAncestor ;

          r3.setEndAfter(next) ;

          var ind = parseInt(csStartAncestor.id.substring('sv_'.length)) ;

          while(r3.toString().length < range.toString().length) {

              ind++ ;

              var node = CY.get("#sv_"+ind) ;

              if (node) {

                next = CY.Node.getDOMNode(node) ;

                r3.setEndAfter(next) ;

              }

              else 

                break ;

          }

          endNode = next.lastChild ;

          endOffset = CY.DOM.getText(endNode).length ;

        }

        else if (!hasWrapperAncestor(startNode) && hasWrapperAncestor(endNode)){

          var r3 = document.createRange() ;

          r3.setEnd(innerEndNode, endOffset) ;

          var csEndAncestor = getWrapperAncestor(endNode) ;

          var prev = csEndAncestor ;

          r3.setStartBefore(prev) ;

          var ind = parseInt(csEndAncestor.id.substring('sv_'.length)) ;

          while(r3.toString().length < range.toString().length) {

              ind-- ;

              var node = CY.get("#sv_"+ind) ;

              if (node) {

                prev = CY.Node.getDOMNode(node) ;

                r3.setStartBefore(prev) ;

              }

              else 

                break ;

          }

          startNode = prev.firstChild ;

          startOffset = 0 ;

        }

        else if (!hasWrapperAncestor(startNode) && !hasWrapperAncestor(endNode)){

          var textLength = text.length ;

          // gather nodes with id sv_xxxx as candidates for start ancestor

          var startNodeInds = [] ;

          for (var ind = 0 ;  ; ind++) {

            var svNode = CY.get("#sv_"+ind) ;

            if (svNode == null) {

              break;

            }

            else {

              var svText = svNode.get("text") ;

              if (text.indexOf(svText) == 0) {

                startNodeInds.push(ind) ;

              }

            }

          }

          // gather nodes with id sv_xxxx as candidates for end ancestor

          var endNodeInds = [] ;

          for (var ind = 0 ;  ; ind++) {

            var svNode = CY.get("#sv_"+ind) ;

            if (svNode == null) {

              break;

            }

            else {

              var svText = svNode.get("text") ;

              if (text.indexOf(svText) == (textLength - svText.length)) { // i.e. the selection exactly ends with svText

                endNodeInds.push(ind) ;

              }

            }

          }

          var stop = false ;

          for (var i = 0 ; i < startNodeInds.length ; i++) {

            for (var j = 0 ; j < endNodeInds.length ; j++) {

              var r4 = document.createRange() ;

              var s = CY.Node.getDOMNode(CY.get("#sv_"+startNodeInds[i])) ; var e = CY.Node.getDOMNode(CY.get("#sv_"+endNodeInds[j])) ;

              r4.setStartBefore(s) ; r4.setEndAfter(CY.Node.getDOMNode(e)) ;

              // does r4 starts after range start and r4 ends before range end ? 

              if ((-1 < r4.compareBoundaryPoints(0, range)) && (1 > r4.compareBoundaryPoints(2, range))) { 

                startNode = s.firstChild ;

                startOffset = 0 ;

                endNode = e.lastChild ;

                endOffset = CY.DOM.getText(e).length ;

                stop = true ; 

                break ;

              }

            }

            if (stop)

              break ;

          }             

        }       

        r1.detach() ;

        r2.detach() ;

      }

      else 

        return null ;

    }

    else 

      return null ;

  }

  else if (document.selection) { // IE case

    var rng = document.selection.createRange();

    if (rng.text.length == 0) 

      return null ;

    var el = rng.parentElement();

    // duplicate the range and collapse it to its start, to ask IE the parent element of the start textNode.    

    var rngStart = rng.duplicate();

    var rngEnd = rng.duplicate();

    rngStart.collapse(true); // collapse to start

    rngEnd.collapse(false);  // collapse to end

    startNode = rngStart.parentElement() ;

    while(rngStart.moveStart('character', -1) != 0) {

      if (rngStart.parentElement() != startNode)

        break ;

      startOffset++ ;

    }

    endNode = rngEnd.parentElement() ;

    while(rngEnd.moveEnd('character', -1) != 0) {

      if (rngEnd.parentElement() != endNode)

        break ;

      endOffset++ ;

    }

    text = rng.text ;

  }

  if (!hasWrapperAncestor(startNode) || !hasWrapperAncestor(endNode)){

    // CY.log('no wrapper on one end') ;

    return null ;

  }

  return {'text' : text, 'start' : {'elt':startNode, 'offset':startOffset}, 'end' : {'elt':endNode, 'offset':endOffset}} ;

}